JP2011098680A - Traveling driver unit of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traveling driver unit of a working vehicle, which improves a power transmission efficiency while well securing a traveling stability and a traveling performance on an irregular ground, and thereby to practically efficiently improve fuel consumption. <P>SOLUTION: The traveling driver unit is equipped with: a hydraulic power transmission 10 having a hydraulic pump 11 driven by an engine 1, and a hydraulic motor 12 driven by a pressure oil discharged by the hydraulic pump; an electric power supply source consisting of an electricity generator 21 driven by the engine, and/or an electric storage device such as a battery 22 and a capacitor; and an electric motor 25 driven by an electric power supplied from the electric power supply source; and a total force transmission 30 transmitting together the output of the electric motor and that of the hydraulic motor in the hydraulic power transmission, to an axle shaft 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a traveling drive device for a work vehicle such as a wheel loader, a wheel excavator, or a wheel crane, and more particularly to a device that transmits an engine output to an axle using a hydraulic pump, a hydraulic motor, or the like.

  Conventionally, a traveling drive device for this type of work vehicle includes a hydraulic pump driven by an engine and a hydraulic motor driven by discharge hydraulic oil of the hydraulic pump, and transmits the power of the hydraulic motor to an axle. Are widely used. There are two types of hydraulic travel drive devices, one in which a return pipe of a hydraulic motor communicates with a tank, and another so-called HST (hydrostatic transmission) in which a hydraulic pump and a hydraulic motor are connected in a closed circuit.

  However, the conventional hydraulic travel drive device has a problem that the efficiency of the hydraulic pump and the hydraulic motor is low, and there is an energy loss such as a pressure loss of the pipe, so that the power transmission efficiency is low. Furthermore, since the kinetic energy at the time of deceleration is consumed by the brake and is not regenerated, there is a problem that the energy efficiency is low and the fuel consumption is poor.

  Therefore, in order to solve such a problem, for example, a travel drive device as disclosed in Patent Document 1 has been proposed. The proposed travel drive device includes a hydraulic pump driven by an engine, an HST drive device having a hydraulic motor connected to the hydraulic pump in a closed circuit, and an electric motor driven using electric power generated by driving the engine ( An electric motor), a first driving wheel driven by the HST driving device, a second driving wheel driven by the electric motor, a vehicle speed detecting means for detecting a vehicle speed, and a vehicle speed detected by the vehicle speed detecting means. And a control means for distributing the engine output to the HST driving device and the electric motor so as to reduce the proportion of power distributed to the HST driving device and increase the proportion of power distributed to the electric motor. . In this case, as the vehicle speed increases, the ratio of the engine output distributed to the HST drive device decreases and the ratio of the engine output distributed to the electric motor increases, so that it is possible to improve fuel consumption particularly at high speeds.

Japanese Patent Application No. 2008-137524

  However, in the above proposal, when the front wheels are driven by the HST driving device and the rear wheels are driven by the electric motor as described in the best mode for carrying out the invention of the specification, it depends on the vehicle speed. As a result, there is a problem that the steering characteristic of the vehicle changes and the running stability decreases. That is, since the ratio of the engine output distributed to the HST drive device is large at low speed, the vehicle is in a state close to front drive, and the vehicle steer characteristic is generally an understeer characteristic, whereas the ratio of engine output distributed to the motor is high speed. Therefore, the vehicle is close to the rear drive or completely in the rear drive state, and the steering characteristic of the vehicle is generally an oversteer characteristic. Also, when the front wheels are stuck when traveling on rough terrain, the front drive is mainly used at low speeds, so the driving force on the rear wheel side to escape the stack is insufficient, and the driving performance on rough terrain is poor. There is also the problem of being sufficient.

  In addition, since the ratio of the engine output distributed to the HST drive device is large at low speeds, the HST drive device is mainly driven even when the running load torque is low, such as running at a low speed and constant speed. Power transmission efficiency is low, and fuel consumption deteriorates. Further, since the ratio of the engine output distributed to the motor is high at high speeds, the motor is mainly driven during acceleration in a high speed region or traveling uphill, and the torque of the HST drive device is not used. For this reason, there is a problem that sufficient driving torque cannot be ensured, and acceleration performance and climbability in a high speed region are deteriorated.

  Further, since the hydraulic motor of the HST drive device is always rotated as the axle rotates, there is a problem that a mechanical rotation loss of the hydraulic motor always occurs and the energy efficiency is lowered.

  The present invention has been made in view of the above points, and the object of the present invention is, in particular, that the engine output is efficiently transmitted to the axle by the combined use of hydraulic equipment and electric equipment, thereby improving running stability and rough terrain. Therefore, it is intended to provide a traveling drive device for a work vehicle that can improve the power transmission efficiency and effectively improve the fuel efficiency while ensuring good traveling performance.

  In order to solve the above problems, the invention according to claim 1 includes a hydraulic pump driven by an engine and a hydraulic motor driven by the discharge pressure oil of the hydraulic pump as a travel drive device of the work vehicle. A hydraulic power transmission unit, a generator driven by an engine, a power supply source composed of a power storage device such as a battery and a capacitor, or both, an electric motor driven by power supplied from the power supply source, A combined force transmission unit that transmits the output of the electric motor and the output of the hydraulic motor of the hydraulic power transmission unit to the axle is provided.

  In this configuration, the first power transmission system that transmits the engine output to the axle via the hydraulic power transmission unit and the resultant force transmission unit according to the traveling state of the vehicle, and the engine output is temporarily converted into the power of the power supply source. After the conversion, the electric motor can be driven by this electric power, and the second power transmission system that transmits the power to the axle via the resultant force transmission unit can be used separately or in combination. For example, when the running load torque is low at a low speed, the second power transmission system having a high power transmission efficiency is mainly used, so that the power transmission efficiency can be increased and the fuel consumption can be improved accordingly. In addition, in the case of acceleration in a high speed region or traveling uphill, sufficient power can be transmitted to the axle by using both the first power transmission system and the second power transmission system. Can increase the sex.

  In addition, since the engine output is transmitted to the same axle via the first power transmission system and the second power transmission system, the steering characteristic of the vehicle is not changed by changing the power transmission system. And traveling stability can be improved. In addition, when applied to both the front wheel axle and the rear wheel axle as axles, when traveling on rough terrain, for example, when the front wheels are stuck, the rear wheel side can be driven out of the stack, and the performance on rough terrain can be improved. Can be good.

  According to a second aspect of the present invention, in the travel drive device for the work vehicle according to the first aspect, the detection and estimation means for detecting or estimating the engine output, the engine speed or the accelerator amount, and a signal from the detection and estimation means, When the engine output, engine speed, or accelerator amount is smaller than a predetermined value, the engine output distributed to the hydraulic power transmission unit is reduced to zero or the axle is driven mainly by the output of the electric motor. Control means for increasing the engine output distributed to the hydraulic power transmission unit when the rotational speed or accelerator amount is greater than a predetermined value and controlling the axle to be driven by the output of both the electric motor and the hydraulic power transmission unit; Further, a configuration is provided.

  In this configuration, the engine output, or the engine speed or accelerator amount related thereto is detected or estimated by the detection estimating means, and the engine output or the like is determined under the control of the control means that receives a signal from the detection estimating means. If the value is smaller than the value, the engine output distributed to the hydraulic power transmission unit is reduced to zero or the axle is driven mainly by the output of the motor, so the power transmission efficiency at low output is ensured. Can be increased. When the engine output is larger than a predetermined value, the engine output distributed to the hydraulic power transmission unit is increased, and the axle is driven by the output of both the electric motor and the hydraulic power transmission unit. Acceleration and climbing performance can be improved with certainty.

  According to a third aspect of the present invention, in the traveling drive device for a work vehicle according to the first aspect, the driving load is smaller than a predetermined value upon receiving a signal from the detection estimating means for detecting or estimating the traveling load and the detection estimating means. In this case, the engine output distributed to the hydraulic power transmission unit is made small or zero, so that the axle is driven mainly by the output of the electric motor. When the running load is larger than a predetermined value, the engine distributed to the hydraulic power transmission unit Control means for increasing the output and controlling the axle to be driven by the output of both the electric motor and the hydraulic power transmission unit is provided.

  In this configuration, the traveling load associated with the engine output is detected or estimated by the detection estimating unit, and under the control of the control unit that receives a signal from the detection estimating unit, the hydraulic load is less than the predetermined value. By making the engine output distributed to the power transmission unit small or zero, the axle is driven mainly by the output of the electric motor, so that the power transmission efficiency at low load can be reliably increased. Further, when the traveling load is larger than a predetermined value, the engine output distributed to the hydraulic power transmission unit is increased, and the axle is driven by the output of both the electric motor and the hydraulic power transmission unit. Acceleration and climbability in high-speed areas can be reliably improved.

  According to a fourth aspect of the present invention, in the traveling drive device for a work vehicle according to the second or third aspect, the power supply source is constituted by both a generator and a power storage device, and further detects an operation of an accelerator pedal or a brake pedal. When the control means receives a signal from the operation detection means and the amount of operation of the accelerator pedal decreases or becomes zero during traveling, or when the brake pedal is operated during traveling In addition, the electric motor is operated as a generator to regenerate traveling power, and when the charge amount of the power storage device is lower than a set value, the regenerated power is charged to the power storage device, and the charge amount of the power storage device is If it is higher than the set value, the generator is operated as an electric motor by the regenerated electric power, and the engine brakes consume the regenerative electric power by applying normal torque to the engine. A configuration is provided to perform control. In this configuration, when the accelerator pedal operation amount decreases or becomes zero during traveling, or when the brake pedal is operated during traveling, that is, when decelerating, the operation detecting means detects this, and this operation detecting means Under the control of the control means that receives a signal from the motor, the electric motor is operated as a generator to regenerate the traveling power, and to charge the regenerated power to the power storage device when the charge amount of the power storage device is low, Regenerative power can be used effectively, and energy efficiency can be increased accordingly.

  According to a fifth aspect of the present invention, in the traveling drive device for a work vehicle according to any one of the first to fourth aspects, further, between the hydraulic motor of the hydraulic power transmission unit and the resultant force transmission unit. It is set as the structure provided with the provided clutch apparatus. In this configuration, when the output of the hydraulic motor is transmitted to the axle, the clutch device is connected manually or automatically to ensure the output transmission, while the clutch device is used to drive the axle only by the electric motor. Can be stopped, and energy loss due to idling of the hydraulic motor can be prevented.

  According to a sixth aspect of the present invention, in the traveling drive device for a work vehicle according to the fifth aspect, the clutch device is automatically operated when the rotational speed of the hydraulic motor coincides with the input rotational speed on the hydraulic motor side of the resultant force transmission unit. When the rotational speed of the hydraulic motor is lower than the input rotational speed on the hydraulic motor side of the resultant force transmission unit, the rotational speed sensitive type is automatically disconnected. In this configuration, the clutch device is of a rotational speed sensitive type, and the connection state and the disconnection state are switched between the rotational speed of the hydraulic motor that is the connection target and the hydraulic motor side input rotational speed of the resultant force transmission unit. Since this is performed when they coincide with each other, it is possible to prevent occurrence of a shock at the time of switching and breakage of the clutch device.

  The invention according to claim 7 is the traveling drive device for a work vehicle according to any one of claims 1 to 6, further comprising a speed reducer provided between the electric motor and the resultant force transmission unit. Make the configuration. In this configuration, since the reduction ratio from the electric motor to the axle is larger than that from the hydraulic motor to the axle by the reduction gear, it is possible to output at a high speed even when the generated torque of the electric motor is small.

  According to an eighth aspect of the present invention, in the traveling drive device for a work vehicle according to any one of the first to seventh aspects, the resultant force transmission unit includes a switching mechanism capable of changing a reduction ratio. . In this configuration, the high-speed driving performance is improved by changing the reduction ratio in the resultant force transmission unit by the switching mechanism according to the traveling state of the vehicle, for example, by switching the reduction ratio in the resultant force transmission unit high in on-road. Further, in off-road, the output torque can be increased and the off-road running performance can be improved by switching the reduction ratio in the resultant force transmission unit to be low.

  As described above, according to the traveling drive device for a work vehicle according to the present invention, when the traveling load torque is low at a low speed, the power transmission system such as an electric motor is mainly used to increase the power transmission efficiency accordingly. Fuel consumption can be improved, and sufficient power can be transmitted to the axle by using a power transmission system such as a hydraulic motor and a power transmission system such as an electric motor in the case of acceleration or climbing in a high speed range. Therefore, acceleration performance and climbing performance in a high speed region can be improved. In addition, since the engine output is transmitted to the same axle via a power transmission system such as a hydraulic motor and a power transmission system such as an electric motor, the steering characteristic of the vehicle changes due to a change in the power transmission system. Therefore, the running stability can be ensured satisfactorily, and when applied to both the front wheel axle and the rear axle as the axle, the running performance on rough terrain can be ensured well.

  In particular, in the invention according to claim 2 or 3, under the control of the control means, the engine output distributed to the hydraulic power transmission unit in the case of a low output / low running load is reduced or made zero. In addition, since the axle is driven by the output of the motor, the power transmission efficiency at low output can be reliably increased, and the engine output distributed to the hydraulic power transmission unit in the case of high output and high running load Since the axle is driven by the output of both the electric motor and the hydraulic power transmission unit, the acceleration performance and the climbing performance in the high speed region can be reliably improved, and the operation reliability can be improved.

  In the invention according to claim 4, when the vehicle is decelerating during traveling, the motor is operated as a generator under the control of the control means to regenerate the traveling power and to regenerate the power when the charge amount of the power storage device is low. In order to charge the power storage device, the regenerative power can be used effectively, and the energy efficiency can be increased correspondingly to improve the fuel efficiency.

  In the invention according to claim 5, when the vehicle is driven by driving only the electric motor, the hydraulic motor can be stopped by disconnecting the clutch device, so that energy loss due to idling of the hydraulic motor can be prevented. Further improvement in fuel consumption can be achieved.

  In the invention according to claim 6, since the clutch device is of a rotational speed sensitive type, it is possible to prevent the occurrence of shock at the time of switching and the breakage of the clutch device, which is effective for implementation. .

  In the invention according to claim 7, since the reduction ratio from the electric motor to the axle is larger than that from the hydraulic motor to the axle by the reduction gear, it can be output at high speed even when the generated torque of the electric motor is small, The output of the motor can be increased while reducing the size of the motor.

  Further, in the invention according to claim 8, high speed running performance can be improved by switching the reduction ratio in the resultant force transmission portion high in on-road, and low reduction ratio in the resultant force transmission portion is switched in off-road. Thus, the output torque can be increased to improve the off-road driving performance, and the driving performance can be improved.

FIG. 1 is a configuration diagram of a travel drive device for a work vehicle according to a first embodiment of the present invention. FIG. 2 is a flowchart showing the control contents of the controller. FIG. 3 is a flowchart showing a power control routine on the generator side. FIG. 4 is a flowchart showing a power control routine on the hydraulic pump side. FIG. 5 is a flowchart showing a travel control routine during deceleration. FIG. 6 is a characteristic diagram showing the relationship between the generator speed, the generator torque, and the generator output. FIG. 7 is a characteristic diagram showing the relationship between engine speed and engine output. FIG. 8 is a characteristic diagram showing the relationship between the generator speed and the generator target torque. FIG. 9 is a characteristic diagram showing the relationship between the motor speed and the motor target torque. FIG. 10 is a characteristic diagram showing the relationship between the pump differential pressure and the hydraulic pump target flow rate. FIG. 11 is a characteristic diagram showing the relationship between the supply-side piping internal pressure and the hydraulic motor capacity. FIG. 12 is the first half of a characteristic diagram showing the correlation on the time axis of vehicle speed, accelerator amount, engine speed, engine power + battery power, power distribution, actuator side power, battery charge amount, and brake amount. FIG. 13 is the latter half of the characteristic diagram. FIG. 14 is a view corresponding to FIG. 1 showing a second embodiment of the present invention. FIG. 15 is a view corresponding to FIG. 1, showing a third embodiment of the present invention. FIG. 16 is a view corresponding to FIG. 1, showing a fourth embodiment of the present invention. FIG. 17 is a view corresponding to FIG. 1 showing a fifth embodiment of the present invention. FIG. 18 is a view corresponding to FIG. 1 showing a sixth embodiment of the present invention. FIG. 19 is a view corresponding to FIG. 1, showing a seventh embodiment of the present invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments that are modes for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration of a traveling drive device for a work vehicle according to a first embodiment of the present invention, wherein 1 is an engine, 2 is a power divider connected to an output shaft of the engine 1, and this power divider 2 Is for distributing the output of the engine 1 to the hydraulic pump 11 of the hydraulic power transmission unit 10 and the generator 21 of the electric power transmission unit 20.

  The hydraulic power transmission unit 10 includes a variable displacement hydraulic pump 11 driven by the output of the engine 1 and a variable displacement hydraulic motor 12 driven by the discharge pressure oil of the hydraulic pump 11. The both 11 and 12 are connected by a closed circuit 13 so-called HST. The pressure in the closed circuit 13 is set to a predetermined value or less by high-pressure relief valves 14a and 14b as a pair of safety valves. The hydraulic pump 11 is provided with a charge pump 15, and the hydraulic oil discharged from the charge pump 15 secures a minimum set pressure by the low pressure relief valve 16, and the pressure in the closed circuit 13 becomes below the minimum set pressure. In this case, the hydraulic oil is fed into the closed circuit 13 from the check valves 17a and 17b, so that the pressure in the closed circuit 13 is ensured to be equal to or higher than the minimum set pressure, and the occurrence of cavitation in the closed circuit 13 is prevented. ing.

  The electric power transmission unit 20 includes, as a power supply source, a generator 21 driven by the output of the engine 1 and a battery 22 as a power storage device. An electric motor 25 driven by electric power supplied from the battery 22 via the converter 23 and the inverter 24 is also included. Here, the converter 23 is originally a circuit that converts AC power generated in the generator 21 into DC power, and the inverter 24 is a circuit that converts DC power into AC power and supplies it to the electric motor 25. In this embodiment, as will be described later, when the motor 25 is operated as a generator and the generator 21 is operated as a motor when the vehicle is decelerated, the converter 23 functions as an inverter and the inverter 24 functions as a converter. Yes.

  The rotational power (output) of the hydraulic motor 12 that is an output unit of the hydraulic power transmission unit 10 and the rotational power (output) of the electric motor 25 that is an output unit of the electric power transmission unit 20 are used as a resultant force transmission unit. After being matched by the transfer 30, it is transmitted to the axle 33 via the prober shaft 31 and the differential device 32, and the axle 33 and the wheels 34 at both ends thereof are rotationally driven. The transfer 30 meshes with the first gear 30a connected to the output shaft of the hydraulic motor 12, the second gear 30b connected to the output shaft of the electric motor 25, and the first and second gears 30a and 30b. And a third gear 30 c connected to the propeller shaft 31. When the vehicle has two axles 33, the two axles 33 may be equipped with a traveling drive device, or one axle 33 may be equipped with a traveling drive device and the other axle may be an idler. The same applies to the case of having three or more axles 33.

  Further, reference numeral 40 denotes a controller as control means for the travel drive device. The controller 40 switches the hydraulic oil discharge direction of the hydraulic pump 11 of the hydraulic power transmission unit 10 in accordance with a signal from the forward / reverse switching switch 41. The rotation direction of the electric motor 25 of the electric power transmission unit 20 is switched via the inverter 24. In addition to the signal from the forward / reverse selector switch 41, the controller 40 includes a signal from the engine speed detecting means 42 for detecting the output speed of the engine 1 (that is, the engine speed), and a depression operation amount (accelerator amount) of the accelerator pedal 43. From the signal of the accelerator operation detecting means 44 for detecting the signal, the signal of the generator rotational speed detecting means 45 for detecting the rotational speed of the generator 21 from the one-phase phase voltage of the converter 23, the one-phase phase voltage of the inverter 24, etc. A signal from the motor rotation speed detection means 46 for detecting the rotation speed of the electric motor 25 and a signal from the pump differential pressure detection means 47 for detecting the differential pressure between the hydraulic oil suction port and the hydraulic oil discharge port of the hydraulic pump 11 are input. Based on these signals, the controller 40 is configured so that the engine 1, the hydraulic pump 11 of the hydraulic power transmission unit 10, and the electric power Which is as to control such as a generator 21 of Itarubu 20.

  Next, of the control by the controller 40, the control contents when the engine output is distributed to the hydraulic pump 12 of the hydraulic power transmission unit 10 and the generator 21 of the electric power transmission unit 20 are shown in FIGS. It demonstrates according to the flowchart shown.

In FIG. 2, after starting, it is first determined in step S1 whether or not the accelerator amount is greater than zero based on the signal from the accelerator operation detecting means 4. When this determination is YES, that is, when the accelerator is being operated, the engine speed N _e is detected by the engine speed detecting means 42 in step S2, and the engine set speed N _e2 is calculated in step S3. This engine set speed N _e2 is the maximum value of the engine speed at which the engine output can be distributed only to the generator 21. As shown in FIG. 6, the maximum output of the generator 21 is P _wgmax when the generator rotational speed N _g is N _g1 or more, and T _gmax × N _{g when} it is less than N _g1 . Therefore, P _we2 is

When N _g ≧ N _g1 P _we2 = P _wgmax / η _g (1)

In the case of N _g <N _g1 P _we2 = (T _gmax × N _g ) / η _g (2)

Here, η _g is the generator efficiency. In addition, when the rotational speed of the electric motor 25 is low at a low speed, the maximum input power of the electric motor 25 may be equal to or lower than the electric power generated by the generator 21. In this case, the maximum output of the generator 21 may be limited so that the power generation amount of the generator 21 does not exceed the maximum input power of the electric motor 25.

Subsequently, it is determined whether the engine speed N _e is less than the engine speed N _e2 when the engine output set value P _we2 in step S4. Here, as shown in FIG. 7, the engine output P _we are in the following engine speed at which the maximum output P _Wemax since it tends to monotonically increase with respect to the engine speed N _e, the engine speed N _e the engine output P _we can easily and reliably estimated from, also, the determination in step S4 is the same as the engine output P _we have determined whether less than the engine output set value P _we2 It is.

Then, the determination in step S4 is when YES, the words when the engine output _{P we} is smaller than the engine output set values _{P we2,} the generator 21 to allocate only the generator 21 to the engine output _{P we} in step S5 After setting the input power P _wg = P _we , the power control on the generator side is executed based on this in step S6, and the control is terminated. When the engine output _Pwe is distributed only to the generator 1, the capacity of the hydraulic pump 11 is controlled to zero.

On the other hand, when the determination of step S4 is NO, that is, when the engine output _{P we} have more than engine power setting _{P we2,} engine to distribute the engine output _{P we} in the generator 21 and the hydraulic pump 11 in step S7 of the output _{P we,} the input power _P wg of the generator 21 the power of the equivalent engine power set value _{P we2 (= P we2),} the input power _P wp of the hydraulic pump 11 and the remaining power ₍₌ P _{we -P we2} ), The power control on the generator 21 side is executed in step S8 based on the set value, and the power control on the hydraulic pump 11 side is executed in step S9, and the control is terminated.

  When the determination in step S1 is NO, that is, when the vehicle is traveling and the accelerator is decelerated with zero, the traveling control during deceleration is executed in step S10, and the control is terminated.

In addition, when the charge amount of the battery 22 is equal to or larger than the set value, the input power _Pwg of the generator 21 can be reduced from the above-described value by the discharge power of the battery 22. In this case, since the amount of power generated by the generator 21 decreases and the load on the engine 1 decreases, the engine speed may be controlled to decrease accordingly.

  The power control on the generator side in step S6 or S8 is performed according to the flowchart shown in FIG.

That is, after start, first, as to confirm the input power P _wg of the generator 21 previously set in step S11, detects the rotational speed N _g of the generator 21 by the generator rotation speed detection means 45 in step S12 . The rotational speed N _g of the generator 21, instead of detecting the generator rotation speed detection means 45, it may be obtained by multiplying the speed reduction ratio of the engine speed N _g.

Subsequently, in step S13, the target torque _Tg of the generator 21 is calculated by the following equation (3) using the rotational speed _Ng of the generator 21 and the input power _Pwg of the generator 21.

T _g = P _wg × η _g / N _g (3)

However, the target torque _{T g} of the generator 21, which is calculated by the equation (3) is when exceeding the maximum torque _{T gmax} of the generator 21 limits the target torque _{T g} to _{T gmax.} Thus, the target torque T _g of the generator 21 will those having the characteristics shown in FIG.

The torque of the generator 21 is controlled to be the target torque T _g in step S14.

Next, in step S15, the output power _Pwm of the electric motor 25 is calculated by the following equation (4).

P _wm = P _wg × η _g × η _m (4)

Here, η _m is the efficiency of the electric motor 25. When the charge amount of the battery 22 is equal to or greater than a set value, the output power P _wm of the electric motor 25 may be set by adding the discharge power of the battery 22 to the input power P _wg of the generator 21.

Subsequently, after detecting the rotational speed N _m of the electric motor 25 by the electric motor rotational speed detecting means 46 in step S16, the target of the electric motor 25 by the following equation based on the rotational speed N _m of the electric motor 25 in step S17 (5) Torque _Tm is calculated.

T _m = P _wm / N _m (5)

However, the target torque _{T m} of a motor 25 which is calculated by the equation (5) is when exceeding the maximum torque _{T mmax} of the motor 25 limits the target torque _{T m} to _{T mmax.} Thus, the target torque T _m of a motor 25, the one having the characteristics shown in FIG.

The torque of the motor 25 is controlled to be the target torque T _m at step S18. The power control on the generator side is thus completed.

  The power control on the hydraulic pump side in step S9 is performed according to the flowchart shown in FIG.

That is, after the start, as well as confirm the input power _P wp of the hydraulic pump 11 previously set ₍₌ P _{we -P we2)} at step S21, the differential pressure of the hydraulic pump 11 by the pump differential pressure detection means 47 in step S22 detecting a [Delta] p _p, calculates the rotational speed N _p of the hydraulic pump 11 by multiplying the speed reduction ratio of the power divider 2 to the engine speed N _e detected by the engine speed detecting means 42 in step S23.

Then, the target flow rate _{Q p} of the hydraulic pump 11 in step S23 is calculated by the equation (6) below.

Q _p = P _wp / ΔP _p (6)

However, the target flow rate _{Q p} of the hydraulic pump 11 calculated by the equation (6) when exceeding the maximum flow rate _{Q pmax} of the hydraulic pump 11 limits the target flow rate _{Q p} to _{Q pmax.} Here, the maximum flow rate Q _pmax of the hydraulic pump 11 is determined by the following equation (7).

_{Q pmax = η p × q pmax} × N p (7)

However, η _p is the volumetric efficiency of the hydraulic pump 11 and q _pmax is the maximum capacity of the hydraulic pump 11. Accordingly, the target flow rate Q _p of the hydraulic pump 11 will those having the characteristics shown in FIG. 10.

Then, the target capacity _{q p} of the hydraulic pump 11 in the step S25 is calculated by the equation (8) below.

_{q p = Q p / (η} p × N p) (8)

The capacity of the hydraulic pump 11 is controlled to be the target capacity q _p in step S26. Thus, the power control on the hydraulic pump side is completed.

According to the power control as described above, when the engine output P _we is engine output set value P _we2 above, engine output is distributed to the generator 21 and the hydraulic pump 11, from the generator 21 or battery 22 The output of the electric motor 25 driven by the supplied power and the output of the hydraulic motor 12 driven by the power supplied as pressure oil from the hydraulic pump 11 are combined by the transfer 30 and transmitted to the axle 33 to rotate the axle 33. To drive.

Here, an example of the capacity control of the hydraulic motor 12 will be described with reference to FIG. 11. The hydraulic motor 12 has a capacity q _p of the maximum capacity when the pressure in the supply-side piping of the closed circuit 13 is equal to or higher than the set value P _1. has become q _pmax, capacity q _p is decreased as the pressure when the supply pipe system pressure is below the set value P ₁ is reduced, eventually the minimum capacity q _min. The minimum capacity q _min may be zero, for example. Then, when driven by the electric motor 25 alone, the capacity of the hydraulic pump 11 becomes zero and the discharge flow rate from the hydraulic pump 11 becomes zero. However, by _setting the minimum capacity q _mmin of the hydraulic motor 12 to zero, The suction flow rate becomes zero, and the suction flow rate and the discharge flow rate can be balanced. As the capacity control, for example, a pressure sensor is provided in the pipe of the closed circuit 13, and the capacity control is electrically performed by the controller 40 based on the pressure measurement value of the pressure sensor, or the hydraulic motor 12 is controlled by the hydraulic control. A function that can change the control characteristics may be provided.

  The travel control during deceleration in step S10 is performed according to the flowchart shown in FIG.

  That is, after starting, first, in step S31, the electric motor 25 is operated as a generator to regenerate traveling power. Subsequently, in step S32, it is determined whether or not the battery charge amount is smaller than the set value based on the signal from the battery 22. If this determination is YES, the regenerative power is charged and recovered in the battery 22 in step S33. On the other hand, when the determination is NO, the generator 21 is operated as an electric motor in step S34, and the normal torque is applied to the engine 1 to consume regenerative power by the engine brake, and the control is ended.

  Next, the operation of the travel drive device will be described with reference to FIGS. FIGS. 12 and 13 show vehicle speed, accelerator amount, engine speed, engine power + battery power, power distribution, actuator side when running at a constant speed pattern of acceleration, high speed, deceleration, and low speed. Changes in power, battery charge amount and brake amount are shown.

First, at the time of acceleration of the vehicle, the driver depresses the accelerator pedal 43 to accelerate. In this case, the engine speed is increased according to the increase of the accelerating amount, the engine output P _we will engine output set value P _we2 more. Since we are full accelerator, the engine output _{P we} becomes the maximum output _{P wemax.} In the power distribution, a _portion corresponding to the output set value _Pwe2 of the engine maximum output _Pwemax is distributed as the generator input power, and the remainder ( _{Pwemax− Pwe2} ) is distributed as the hydraulic pump input power. However, when the battery charge amount is equal to or greater than the set value SOC1, since the battery 22 is in a dischargeable state, the battery 22 can be discharged and the power generation amount of the generator 21 can be reduced by the amount of battery discharge. In this case, since the power generation amount of the generator 21 is reduced by the amount of battery discharge, the engine output is also reduced by that amount. As a result, the sum of the battery discharge amount and the engine output becomes the engine maximum output _Pwemax . Further, since the engine output decreases as described above while the battery 22 is discharging, the engine speed may be reduced by an amount commensurate with the decrease in engine output. From the above, when the vehicle is accelerated, the output generated by the electric motor 25 that is supplied with power from the generator 25 and the battery 22 and the output of the hydraulic motor 12 that is driven by being supplied with power from the hydraulic pump 11 are transferred. 30 is transmitted to the axle 33 via 30 or the like, and the axle 33 is rotationally driven.

When the vehicle travels at a constant speed, it can normally travel with less power than during acceleration. Therefore, when the vehicle runs at a constant speed, the driver reduces the accelerator amount to an extent appropriate for the speed. Therefore, the engine speed is reduced, the engine output P _we concomitantly decreases than the output setting value P _we2. In this case, since the engine output _Pwe is distributed only to the generator 21 and power is not distributed to the hydraulic pump 11, the hydraulic motor 12 does not receive power supply from the hydraulic pump 11, and the output power of the hydraulic motor 12 is zero. It becomes. The axle 33 is driven by an electric motor 25 that is driven by receiving power supply from the generator 21.

  When the vehicle decelerates, the electric motor 25 operates as a generator, power regeneration to the battery 22 is performed, and the charge amount of the battery 22 is recovered.

Next, the effect of the travel drive device will be described. When traveling at a constant speed at a low speed, as described above, the engine output _Pwe is distributed only to the generator 21 and receives power supply from the generator 21. The axle 33 is driven by the electric motor 25 driven in this manner. For this reason, compared with the case where a part of the engine output _Pwe is distributed to the hydraulic pump 11 of the hydraulic power transmission unit 10 having a low power transmission efficiency, the power transmission efficiency at the time of low speed traveling is increased, and the fuel efficiency is improved accordingly. be able to.

Further, in the case of acceleration at a high speed or traveling uphill, the driver usually operates the accelerator pedal 43 so as to increase the accelerator amount, so that the engine output _Pwe increases and the engine output _Pwe is generated by the power generation. The axle 33 is divided by the output of the electric motor 25 which is distributed to the machine 21 and the hydraulic pump 11 and driven by receiving power supply from the generator 21 and the output of the hydraulic motor 12 which is driven by receiving power supply from the hydraulic pump 11. Is driven. For this reason, sufficient drive torque can be ensured with respect to the axle 33, and acceleration performance and climbing performance at high speed can be enhanced.

  In addition, since the engine output Pwe is transmitted to the same axle 33 via the hydraulic power transmission unit 10 and the electric power transmission unit 20, the steering characteristic of the vehicle changes due to a change in the power transmission system. There is no such thing, and good running stability can be secured. Further, when applied to both the front wheel axle and the rear wheel axle as the axle 33, for example, when traveling on rough terrain, for example, when the front wheels are stacked, it is possible to escape the stack by driving the rear wheels. The running performance can be improved.

  Furthermore, when the vehicle is decelerated, the electric motor 25 is operated as a generator, and the regenerated electric power is used for charging the battery 22, so that the energy efficiency can be increased accordingly.

  FIG. 14 shows an overall configuration of a travel drive device for a work vehicle according to a second embodiment of the present invention. In the case of the second embodiment, the configuration of the hydraulic power transmission unit 50 is different from that in the case of the first embodiment.

  That is, the hydraulic power transmission unit 50 is interposed between the hydraulic pump 51 driven by the output of the engine 1, the hydraulic motor 52 driven by the discharge pressure oil of the hydraulic pump 51, and both of them. And a switching valve 53. The switching valve 53 switches the rotational direction of the hydraulic motor 52 by switching the position under the control of the controller 40 that receives a signal from the forward / reverse switching switch 41.

  The hydraulic power transmission unit 50 also includes high-pressure relief valves 54a and 54b and check valves 55a and 55b. However, the charge pump 15 such as the hydraulic power transmission unit 10 in the first embodiment or the like The low pressure relief valve 16 does not exist. The configuration of the travel drive device other than the hydraulic power transmission unit 50 is the same as that in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And also in the said 2nd Embodiment, the fundamental operation | movement and effect of a traveling drive apparatus are the same as that of the case of 1st Embodiment.

  FIG. 15 shows an overall configuration of a travel drive device for a work vehicle according to a third embodiment of the present invention. In the case of the third embodiment, the travel drive device has a configuration suitable for driving a plurality (two in the figure) of axles 33a and 33b.

  That is, the hydraulic power transmission unit 10 of the travel drive device has an HST configuration having a pair of hydraulic motors 12 a and 12 b driven by the discharge pressure oil of the hydraulic pump 11. In addition, the electric power transmission unit 20 of the travel drive device includes a pair of electric motors 25a and 25b driven by electric power supplied from a generator 21 or a battery 22 as an electric power supply source, and the electric motors 25a and 25b. It has a pair of inverters 24a and 24b that convert the DC power supplied from the generator 21 or the battery 22 into AC power and supply it.

  The output shafts of the pair of hydraulic motors 12a and 12b are both connected to the first gear 30a of the transfer 30, and the output shafts of the pair of electric motors 25a and 25b are both the second gear 30b of the transfer 30. It is connected to. And after the output of a pair of hydraulic motor 12a, 12b and the output of a pair of electric motor 25a, 25b are match | combined by the transfer 30, the prober shaft 31, the differential gears 32a and 32b between wheels, and the differential gear 61 between axles are made. The two axles 33a and 33b and the two axles 33a and 33b and the wheels 34a and 34b at both ends thereof are rotationally driven. The other configurations of the travel drive device are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And in the said 3rd Embodiment, while being able to respond | correspond to the case where a big driving torque is required in order to drive the several axles 33a and 33b in the large vehicle with many axles especially among work vehicles. As in the case of the first embodiment, controlling the hydraulic motors 12a, 12b and the electric motors 25a, 25b, etc., also has the effect of improving the power transmission efficiency and improving the fuel consumption.

  FIG. 16 shows an overall configuration of a travel drive device for a work vehicle according to a fourth embodiment of the present invention. In the case of the fourth embodiment, the travel drive device includes a clutch device 71 provided between the hydraulic motor 12 of the hydraulic power transmission unit 10 and the transfer 30.

  Although not shown in detail in the drawing, the clutch device 71 is of a rotational speed sensitive type such as a one-way clutch, and the rotational speed of the hydraulic motor 12 and the first gear 30a which is the hydraulic motor side input portion of the transfer 30 are provided. A connection state is automatically established when the rotation speed matches, and a disconnection state is automatically established when the rotation speed of the hydraulic motor 12 is lower than the rotation speed of the first gear 30a of the transfer 30. The other configurations of the travel drive device are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And in 4th Embodiment, in addition to having the same effect as the case of 1st Embodiment, when driving with the axle 33 driven only by the electric motor 25 like constant speed driving | running | working, the hydraulic motor 12 Since the rotation speed of the first gear 30a of the transfer 30 is lower than the rotation speed of the first gear 30a of the transfer 30, the clutch device 71 is automatically disconnected. For this reason, the hydraulic motor 12 does not run idle due to power transmission from the transfer 30 side, energy loss can be prevented correspondingly, and fuel consumption can be improved.

  In addition, the clutch device 71 is of a rotational speed sensitive type, and the connection state and the disconnection state thereof are switched between the rotational speed of the hydraulic motor 12 and the first gear 30a of the transfer 30 that are connected to each other. Since it is performed when the rotational speed matches, it is possible to prevent occurrence of a shock at the time of switching and damage to the clutch device 71.

  FIG. 17 shows an overall configuration of a travel drive device for a work vehicle according to a fifth embodiment of the present invention. In the case of the fifth embodiment, the traveling drive device includes a reduction gear 81 provided between the electric motor 25 and the transfer 30. The other configurations of the travel drive device are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And in 4th Embodiment, in addition to having an effect similarly to the case of 1st Embodiment, the reduction ratio from the electric motor 25 to the axle shaft 33 is made from the hydraulic motor 12 to the axle shaft 33 by the said reduction gear 81. FIG. Therefore, even when the generated torque of the electric motor 25 is small, it can be output at a high speed, and as a result, the output of the electric motor 25 can be increased while the electric motor 25 is downsized. .

  FIG. 18 shows an overall configuration of a travel drive device for a work vehicle according to a sixth embodiment of the present invention. In the case of the sixth embodiment, the travel drive device is a switching that can change the reduction ratio to high and low two stages as a resultant force transmission unit that transmits the output of the electric motor 25 and the output of the hydraulic motor 12 to the axle 33 side. A transfer 90 having a mechanism 91 and a clutch device 71 provided between the hydraulic motor 12 and the transfer 90 are provided as in the case of the fourth embodiment.

  The switching mechanism 91 includes a first gear train 92 including three gears 92 a, 92 b, and 92 c that transmits the outputs of the hydraulic motor 12 and the electric motor 25 to the axle 33 side with a low reduction ratio, and the hydraulic motor 12 and the electric motor 25. The second gear train 93 including three gears 93a, 93b, 93c for transmitting the output to the axle 33 side at a high reduction ratio, and either one of the first and second gear trains 92, 93 are in a power transmission state. And when the selector 94 is moved to the first gear train 92 side, the first gear train 92 is connected to the power transmission state, and the second gear train 92 is in the idling state. As a result, the outputs of the hydraulic motor 12 and the electric motor 25 are transmitted to the axle 33 side with a low reduction ratio. On the other hand, when the selector 94 is moved toward the second gear train 93, the second gear train 93 is driven. Coupled to reach state, the first gear train 92 is idle state, and is transmitted to the axle 33 side at the output of the hydraulic motor 12 and the motor 25 is high reduction ratio. The selector 94 is switched in position by an actuator (not shown) such as an air cylinder in accordance with the switching operation of the shift switch 95 under the control of the controller 40 that receives the signal of the shift switch 95. ing. The other configurations of the travel drive device are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And in the said 6th Embodiment, 4th Embodiment by having provided the clutch apparatus 71 provided between the hydraulic motor 12 and the transfer 90 with the effect similar to the case of 1st Embodiment. In addition to the effects similar to the above, the reduction ratio can be appropriately changed by the switching mechanism 91 of the transfer 90 according to the traveling state of the vehicle. For example, high speed driving performance can be improved by switching the reduction ratio at the transfer 90 high on road, and off-road driving performance by increasing the output torque by switching the reduction ratio at the transfer 90 low on off road. Can be improved.

  FIG. 19 shows an overall configuration of a travel drive device for a work vehicle according to a seventh embodiment of the present invention. In the case of the seventh embodiment, the configuration in which the output of the hydraulic motor 12 and the output of the electric motor 25 are combined and transmitted to the axle 33 is different from that in the case of the first embodiment.

  That is, the electric motor 25 is coaxially attached to the output shaft 101 of the hydraulic motor 12, and the output of the electric motor 25 and the output of the hydraulic motor 12 are matched by the output shaft 101, via the transfer 102 and the prober shaft 31. It is configured to be transmitted to the axle 33. The transfer 102 includes a first gear 102 a connected to the output shaft 101 of the hydraulic motor 101, and a second gear 102 b that meshes with the first gear 102 a and is connected to the propeller shaft 31. . In the case of the seventh embodiment, the output shaft 101 of the hydraulic motor 12 and the transfer 102 constitute a resultant force transmission unit 100 that transmits the output of the hydraulic motor 101 and the output of the electric motor 25 together to the axle 33. The other configurations of the travel drive device are the same as those in the first embodiment, and the same members are denoted by the same reference numerals and the description thereof is omitted.

  And also in the said 7th Embodiment, the fundamental operation | movement and effect of a traveling drive apparatus are the same as that of the case of 1st Embodiment.

In addition, this invention is not limited to the said 1st thru | or 7th embodiment, Various other forms are included. For example in the first embodiment, the engine speed detecting means 42 for detecting an engine speed N _e is provided to estimate the engine output P _we from the engine speed N _e detected by the detection means 42, the engine output P _we may allocate an engine output _{P we} if engine power set value _{P we2} smaller than only to the generator 21, the generator 21 and the hydraulic pump engine output _{P we} have a case where the engine output _{P we} above the engine output set value _{P we2} However, the present invention is provided with an engine output detecting means for directly detecting the engine output based on, for example, the output torque and the rotational speed, and the engine output P detected by the detecting means. The distribution of the engine output _Pwe may be controlled according to the size of the _we . Further, there is a correlation between the engine output P _we and the engine speed N _e, and since made to have a correlation between the accelerating amount and the engine speed N _e When controlling the engine speed N _e in the governor, If the detected value is smaller than a predetermined value, the engine output _Pwe is distributed only to the generator 21, and if the detected value is larger than the predetermined value, the engine output _Pwe is detected as a generator. 21 and the hydraulic pump 11 may be distributed.

Furthermore, between the engine output P _we the travel load P _wL, relationship is established as shown in the following equation (9).

P _wL = P _we × η _a (9)

Where η _a is the actuator efficiency. Thus, since the engine output P _we and travel load P _wL is almost proportional, the present invention, instead of the engine output P _we, provided detection or estimation means for detecting or estimating the travel load P _wL, this may perform distribution control of engine output P _we depending on the size of the detected or estimated travel load P _wL by detection or estimation means. Here, as a method of estimating the traveling load P _wL , for example, the following equation (10) may be used.

P _wL = {F _t + F _a + M (g × sin θ + a)} × V (10)

Where F _t is the rolling resistance of the tire, F _a is the air resistance, M is the vehicle mass, g is the gravitational acceleration, a is the acceleration, V is the vehicle speed, and θ is the road surface inclination angle. From equation (10), the traveling load can be estimated by measuring the vehicle speed V, acceleration a, and road surface inclination angle θ.

  In addition, in the first embodiment, when the vehicle 25 is decelerated, the motor 25 is operated as a generator, and when the regenerative power is charged to the battery 22, when the charge amount is equal to or larger than a set value, the generator 21 is used as the motor. The regenerative electric power is consumed by the engine brake by operating and applying a normal torque to the engine 1, but the present invention operates the generator 21 as an electric motor when the charge amount of the battery 22 is equal to or greater than a set value. Instead, regenerative power may be consumed by a regenerative resistor connected between the generator 21 and the electric motor 25. Further, instead of the battery 22, another power storage device such as a capacitor may be used. Furthermore, when the vehicle decelerates, not only when the accelerator amount that is the amount of depression of the accelerator pedal 43 is zero as in the first embodiment, but when the depression operation of the brake pedal is input, The power generation amount of the electric motor 25 may be increased according to the brake operation amount. In this case, the regenerative power can be increased according to the increase in the brake operation amount.

DESCRIPTION OF SYMBOLS 1 Engine 10,50 Hydraulic power transmission part 11,51 Hydraulic pump 12,12a, 12b, 52 Hydraulic motor 20 Electric power transmission part 21 Generator (electric power supply source)
22 Battery (power storage device, power supply source)
25, 25a, 25b Electric motor 30, 90 Transfer (synthetic force transmission part)
33, 33a, 33b Axle 40 controller (control means)
42 Engine speed detection means 43 Accelerator pedal 44 Accelerator operation detection means 71 Clutch device 81 Reducer 91 Switching mechanism 100 Combined force transmission unit

Claims (8)

A hydraulic power transmission unit having a hydraulic pump driven by an engine and a hydraulic motor driven by the discharge pressure oil of the hydraulic pump;
A power source comprising a generator driven by an engine, a power storage device such as a battery or a capacitor, or both;
An electric motor driven by electric power supplied from the power supply source;
A traveling drive device for a work vehicle, comprising: a resultant force transmission unit that transmits the output of the electric motor and the output of the hydraulic motor of the hydraulic power transmission unit to the axle. Detection estimation means for detecting or estimating engine output, engine speed or accelerator amount;
When the engine output, the engine speed or the accelerator amount is smaller than a predetermined value in response to the signal from the detection estimation means, the engine output distributed to the hydraulic power transmission unit is reduced or reduced to zero mainly to output the motor. If the engine output, engine speed or accelerator amount is greater than a predetermined value, the engine output distributed to the hydraulic power transmission unit is increased, and the axle is driven by the output of both the electric motor and the hydraulic power transmission unit. The traveling drive device for a work vehicle according to claim 1, further comprising a control unit that performs control to drive. Detection and estimation means for detecting or estimating the running load;
When the signal from the detection estimation means is received and the traveling load is smaller than a predetermined value, the engine output distributed to the hydraulic power transmission unit is reduced to zero or the axle is driven mainly by the output of the electric motor. And a control means for controlling to increase the engine output distributed to the hydraulic power transmission unit when the load is greater than a predetermined value and to drive the axle by the output of both the electric motor and the hydraulic power transmission unit. A travel drive device for a work vehicle according to claim 1. The power supply source consists of both a generator and a power storage device,
Comprising an operation detecting means for detecting an operation of an accelerator pedal or a brake pedal;
The control means receives the signal from the operation detecting means, and when the amount of operation of the accelerator pedal decreases or becomes zero during traveling, or when the brake pedal is operated during traveling, When the driving power is regenerated and the amount of charge of the power storage device is lower than a set value, the regenerated power is charged to the power storage device, and the amount of charge of the power storage device is higher than the set value. The traveling of the work vehicle according to claim 2 or 3, wherein the generator is operated by the regenerated electric power as an electric motor, and the engine brake is used to control to consume the regenerative electric power by applying a normal rotation torque to the engine. Drive device.   The travel drive device for a work vehicle according to any one of claims 1 to 4, further comprising a clutch device provided between a hydraulic motor and a resultant force transmission portion of the hydraulic power transmission portion.   The clutch device is automatically connected when the rotational speed of the hydraulic motor matches the hydraulic motor side input rotational speed of the resultant force transmission unit, and the rotational speed of the hydraulic motor is the hydraulic motor side input rotational speed of the resultant force transmission unit. 6. The traveling drive device for a work vehicle according to claim 5, wherein the traveling drive device for the work vehicle is of a rotational speed sensitive type that automatically enters a disconnected state when it falls below the number.   The travel drive apparatus for a work vehicle according to any one of claims 1 to 6, further comprising a speed reducer provided between the electric motor and the resultant force transmission unit.   The travel drive device for a work vehicle according to any one of claims 1 to 7, wherein the resultant force transmission unit includes a switching mechanism capable of changing a reduction ratio.