JP2650614B2 - Forklift control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a forklift, which realizes both vehicle speed control and optimal fuel efficiency control of the forklift.

[0002]

2. Description of the Related Art A conventional forklift control device connects an output shaft of an engine to wheels via a stepped transmission having a sliding element, and an accelerator pedal through a wire to a throttle valve of the engine. And a clutch pedal (referred to as an inching pedal in an AT car) for operating the sliding element to connect / disconnect the wheel to / from the output shaft of the engine. Vehicle speed and cargo handling speed are adjusted. Specifically, when performing normal driving, the vehicle speed is adjusted by the depression amount of the accelerator pedal with the clutch pedal connected, and when performing the cargo handling operation while the vehicle is stopped, the vehicle is adjusted by the depression amount of the accelerator pedal with the clutch pedal released. The cargo handling speed is adjusted.

In recent years, a continuously variable transmission has been used as a transmission in order to improve operability, and a speed ratio of the transmission is continuously adjusted so that the vehicle speed becomes a target vehicle speed with respect to an accelerator depression amount. Some of them have been developed.

[0004]

In any case, there is known a conventional forklift in which vehicle speed control is performed from the viewpoint of improving operability, but fuel efficiency is taken into consideration. There is no. That is, as described above, in the conventional vehicle, the target vehicle speed is set in accordance with the accelerator pedal depression amount, and the accelerator pedal is depressed, and the operation amount is uniquely transmitted to the throttle valve via a wire. When the engine opens and closes and the engine blows up, the speed ratio of the transmission is merely changed to a power transmission state in which the vehicle speed takes a target value with respect to the engine speed. Therefore, the engine speed completely depends on the throttle opening. But,
As a characteristic of the engine, there is a target engine speed that satisfies the optimum fuel efficiency condition with respect to the throttle opening,
When considering a conventional forklift from that point of view, the engine speed is quite a consequence and changes completely regardless of the optimal fuel efficiency conditions, so the fuel efficiency is poor and a considerable loss occurs at full operation. Conceivable.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and has as its object to provide a control device for a forklift which presupposes vehicle speed control of the forklift and also enables optimum fuel economy running. The purpose is.

[0006]

In order to achieve the above object, the present invention employs the following configuration.

That is, as shown in FIG. 1, a control device for a forklift according to the present invention includes a fluid transmission c interposed between an engine a and a wheel b for continuously changing a speed ratio e; For a forklift including an accelerator o which is not connected to a throttle valve d of an engine a, an accelerator depression amount detecting means f, a vehicle speed detecting means g, an engine speed detecting means h, Throttle opening detection means i, first setting means j for setting target vehicle speed V0 for accelerator depression amount ACC, and target engine speed SE0 for setting throttle opening THL that satisfies optimal fuel economy conditions. 2 and the actual vehicle speed V
Second comparison unit for outputting a first comparison unit m for outputting the deviation epsilon ₁ is compared with the target vehicle speed V0, the deviation epsilon ₂ by comparing the actual engine speed SE and the target engine speed SE0 n and the deviations ε ₁ output by the first and second comparing units m and n,
control means p for outputting a speed ratio control signal s (e) and a throttle opening control signal s (THL) in a direction to cancel both ε ₂ and controlling the speed ratio e and the throttle opening THL. It is characterized by the following.

[0008]

As described above, the accelerator o is set to the throttle valve d.
And the throttle opening THL is controlled together with the speed ratio e, the conventional control parameter becomes the speed ratio e.
However, in the present invention, two control parameters are the speed ratio e and the throttle opening THL.
Therefore, the vehicle speed V and the engine speed S are used for control purposes.
The two control amounts of E can be handled simultaneously. That is,
When the driver has depressed the accelerator o, the accelerator depression amount ACC is input from the accelerator depression amount detecting means f to the first setting means j, and the target vehicle speed V0 corresponding to the depression amount ACC is input to the first setting means j. Is set. Then, the target vehicle speed V0 is inputted with actual vehicle speed V detected by the vehicle speed detecting means g in the first comparing section m, a deviation epsilon ₁ therebetween is inputted into the control means p from the comparison unit m. On the other hand, the throttle opening THL is input from the throttle opening detecting means i to the second setting means k, and a target engine speed SE0 corresponding to the throttle opening THL is set in the second setting means k. Then, the target engine speed SE0 is input to the second comparator n together with the actual engine speed SE detected by the engine speed detector h, and the difference ε ₂ between the _two is sent to the controller p. Is entered. The control means p outputs the speed ratio control signal s (e) and the throttle opening control signal s (THL) so that both the deviations ε ₁ and ε ₂ become 0, and adjusts the speed ratio e and the throttle opening THL. Control. As a result, the vehicle speed V is controlled to the target vehicle speed V0 appropriate for the accelerator pedal depression amount ACC of the driver, and the engine speed SE is controlled to the target engine speed SE0 that meets the optimum fuel efficiency condition.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

A forklift to which this control mechanism is applied has an HS configuration in which a variable displacement pump 1 and a variable displacement motor 2 are connected by a hydraulic circuit 3 as shown in FIG.
T, a continuously variable transmission 4 having a pump input shaft 1
a is connected to the engine 5, the motor output shaft 2 a is connected to the wheels 6, and the accelerator pedal 7 is not connected to the throttle valve of the engine 5. The engine 5 is a throttle valve control actuator 5a.
When a throttle drive signal S (THL) is given, the actuator 5a drives a throttle valve (not shown) to realize a required throttle opening THL. On the other hand, the HST 4 sets the capacity of the pump 1 to Dp, the number of rotations of the pump input shaft 1a to Np, the capacity of the motor 2 to Dm, the number of rotations of the motor output shaft 2a to Nm, and the maximum capacities Dpmax and Dmmax to each other. Assuming that they are equal, and further assuming that there is no leakage in the hydraulic circuit 3, a relationship of Dp × Np = Dm × Nm holds, and the speed ratio e is expressed as e = Nm / Np = Dp / Dm. It is. The speed ratio e can be continuously adjusted by changing the pump displacement Dp or the motor displacement Dm. That is, as shown in FIG. 3, when the pump displacement Dp is changed from 0 to the maximum Dp max while the motor displacement Dm is kept at the maximum Dm max, the speed ratio e
Changes in the range of 0 ≦ e ≦ 1 as shown in FIG. 4, and further changes the motor capacity Dm from the maximum Dm max toward 0 while maintaining the pump capacity Dp at the maximum Dp max as shown in FIG. Then, as shown in FIG. 4, the speed ratio e is 1 ≦ e.
The characteristic changes in the region of FIG. The variable displacement motor 2 can be replaced with a fixed displacement motor. In this case, the speed ratio e changes only in the range of 0 ≦ e ≦ 1. A fixed pump is connected to the pump input shaft 1a via a gear or the like, and this fixed pump transfers oil to be discharged using a power of the engine 5 to a lift cylinder or a tilt cylinder (not shown), and lifts and lowers a mast or a mast. The tilting is performed.

In the above-described forklift, the present embodiment is designed to control the speed ratio e of the HST 4 and the throttle opening THL of the engine 5 in order to control the accelerator pedal depression amount detector 11, the vehicle speed detector 12, and the engine speed. The rotational speed detector 13, the throttle opening detector 14, the speed ratio detector 15, and the first setting unit, the second setting unit, the first comparison unit, the second comparison unit, and the control unit And a controller 16 that plays a role.

The accelerator depression amount detector 11 is, for example, a potentiometer attached to a rotation shaft of the accelerator pedal 7 and converts the accelerator depression amount ACC into an electric signal and outputs the electric signal.

The vehicle speed detector 12 is, for example, an encoder attached to the axle, that is, the motor output shaft 2a, and converts the vehicle speed V corresponding to the rotation speed Nm into an electric signal and outputs it. I have.

The engine speed detector 13 is, for example, an encoder attached to the crankshaft of the engine 5 or the pump input shaft 1a, and converts the engine speed SE into an electric signal and outputs the electric signal.

The throttle opening detector 14 is, for example, a potentiometer attached to the throttle valve drive shaft or the throttle valve control actuator 5a, and converts the throttle opening THL into an electric signal and outputs it. Has become.

The speed ratio detector 15 is disposed at a position for detecting a change amount such as a swash plate angle or an eccentric position of a pintle of the pump 1 and the motor 2 constituting the HST 4, and detects a capacity. The speed ratio e corresponding to the capacity is converted into an electric signal and output.

The controller 16 is constituted by a normal microcomputer system having, for example, a CPU, a memory, an interface, and the like, and its memory is provided from the viewpoint of operability and the like as shown in the block diagram of FIG. MAP1 as first setting means for determining a target vehicle speed V0 considered to be optimal with respect to the accelerator pedal depression amount ACC, and second setting for defining a target engine speed SE0 which satisfies the optimal fuel efficiency condition with respect to the throttle opening THL. Mean MAP
2 are stored. Specifically, for example, the MAP1 is set so that the accelerator depression amount ACC and the target vehicle speed V0 correspond substantially linearly. In MAP2, the optimal fuel consumption line in FIG. 7 is stored. That is, as is apparent from the SE-TE curve in FIG. 3, if a certain throttle opening THL is determined as the characteristic of the engine, the engine speed SE and the engine output torque TE are located somewhere on a unique curve. But on that curve,
There is only one engine speed SE that satisfies the optimum fuel consumption condition with respect to the throttle opening, and the optimum fuel consumption line is formed by connecting the points over an arbitrary throttle opening THL. Further, the memory comprises a first comparison unit 16a for outputting a deviation epsilon ₁ by comparing the actual vehicle speed V and the target vehicle speed V0,
A second comparison unit 16b for outputting a deviation epsilon ₂ compares with the target engine speed SE0 actual engine speed SE, PI control for converting the deviation epsilon ₁ to the speed ratio control signal S (e), PD control, a control function H ₁ based on PID control or the like,
And similar control function H ₄ for converting the deviation epsilon ₂ to the throttle control signal S (THL) is at least stored.

Here, in the block diagram of FIG. 5, a thick line is a portion corresponding to a mechanical element, and a thin line is a portion corresponding to a control element of the controller 16.

The outline of the control program executed by the controller 16 together with the operation of the mechanical system will be described below with reference to FIGS.

First, the operating characteristics of the mechanical system will be described. (1) When the system is in a steady state, the engine 5 rotates at a certain rotation speed SE under a certain throttle opening THL, and the HST 4 The rotational speed SE is converted into the vehicle speed V of the wheel 6 at a certain constant speed ratio e. The vehicle speed V is constant, and a load torque TW of a magnitude corresponding to the vehicle speed V is applied to the engine 5. H2 is the vehicle speed V and load torque TW at that time.
, And shows a characteristic peculiar to each mechanism as shown in FIG. Further, as shown in FIG. 7, since the engine output torque TE is uniquely determined with respect to the throttle opening THL and the engine speed SE, the engine output torque TE is also constant in this case. Since the load torque TW and the engine output torque TE are balanced on the shaft 1a (2a), the above-mentioned engine speed SE is kept constant.

(2-A) Next, considering the case where the speed ratio e is increased from the steady state, the vehicle speed V increases, and as a result, the load torque TW increases. For this reason, the axle 1a
In (2a), the load torque TW is the engine output torque TE
, The engine speed SE decreases through the inertia s · Ie of the engine 5.

(2-B) Conversely, when the speed ratio e is reduced from the steady state, the vehicle speed V is reduced, and as a result, the load torque TW is reduced. Therefore, the axle 1a (2a)
Above, the load torque TW falls below the engine output torque TE, and the engine speed SE rises.

(3-A) Further, considering the case where the throttle opening THL is increased from the steady state, the engine output torque TE increases. Therefore, the axle 1a (2
a) above, the engine output torque TE exceeds the load torque TW, and the inertia of the engine 5 causes the engine speed S to increase.
E increases and the vehicle speed V also increases.

(3-B) Conversely, when the throttle opening THL is decreased from the steady state, the engine output torque TE decreases. Therefore, the engine output torque TE falls below the load torque TW on the axle 1a (2a), the engine speed SE decreases, and the vehicle speed V also decreases.

Next, control of this embodiment will be considered in consideration of the characteristics of the mechanical system described above. First, when the mechanical system is in the above-described steady state (1), the control system has converged.
That is, the actual vehicle speed V corresponds to the accelerator opening ACC and MA
It matches the target vehicle speed V0 taken from P1. Therefore, the speed ratio control signal S (e) is not output when the deviation ε ₁ is 0, and the HST 4 maintains the speed ratio e at that time. Further, the engine speed SE is set to M corresponding to the throttle opening THL.
Coincides with the target engine rotational speed SE ₀ retrieved from the AP2. Therefore, the deviation epsilon ₂ is a throttle control actuator 5a throttle control signal S (THL) is not output by 0, the throttle opening THL holds opening THL at that time.

Now, when the driver depresses the accelerator pedal 7, the accelerator depression amount ACC increases. Then MAP
Larger target vehicle speed V0 is taken out through one deviation epsilon ₁ from comparing portion 16a + is output. This allows
Control function H ₁ a via in speed ratio increasing signal S (e) is output and input into HST4. As a result, the mechanical system causes the state change of (2-A) described above. That is, the vehicle speed V increases and the engine speed SE decreases. Since the vehicle speed V is fed back to the successive approximation unit 16a, the vehicle speed V gradually approaches the target vehicle speed V0, the deviation ε decreases, and the speed ratio e
Control speed slows down. On the other hand, when the engine speed SE decreases due to this control, the deviation ε _{2 of} +
Is output, and a throttle opening increase signal S (THL) is output via the control function H4. As a result, the mechanical system causes the state change (3-A) described above. That is, the engine speed SE increases and the vehicle speed V also increases. Throttle opening T
HL is successively converted to a target vehicle speed SE0 via MAP2, and the target vehicle speed SE0 is fed back to the comparison unit 16b. Therefore, the engine speed SE gradually approaches the target value SE0 with respect to the throttle opening THL, and the deviation ε
₂ is reduced and the control speed of the throttle opening THL is reduced.

Actually, the above-mentioned state changes (2-A) and (3-A) of the mechanical system occur in combination with the accelerator depression operation ACC, and the vehicle speed V is set to a target value corresponding to the accelerator depression amount ACC. When the engine speed SE approaches the value V0, the engine speed SE approaches the target value THL0 that satisfies the optimum fuel consumption condition with respect to the throttle opening THL, and the system converges toward the steady state (1) as a whole. At that time, (3-A)
If the vehicle speed V increases too much at this time, the comparison unit 16a
There output deviation epsilon ₁ to the - so to become, the speed ratio decreasing signal S
(e) is output. Then, the mechanical system is (2-B) → (3
The state change of -B) occurs, and a steady state is reached. That is, in the above control, the state changes of (2-A) to (3-B) are merged and finally converge to the steady state of (1).

Although the description is omitted, when the accelerator pedal depression amount ACC is reduced, the control according to the above is performed, and the state change of the mechanical systems (2-B) and (3-B) is performed first. It occurs as a fusion, and in some cases (2-A), (3-A)
Finally, the vehicle speed V approaches the target value V0 corresponding to the accelerator pedal depression amount ACC, and the engine speed SE approaches the target value THL0 that satisfies the optimum fuel efficiency condition with respect to the throttle opening THL. Therefore, the system as a whole converges to the steady state of (1).

Therefore, when the control device of the present embodiment is applied, not only can the forklift run at a desired speed, but also the relationship between the engine speed and the throttle opening is controlled so as to conform to the optimum fuel efficiency condition. It is possible to reliably improve fuel efficiency as compared with the conventional case.

Next, another embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. Note that the same reference numerals are given to portions common to the above-described embodiment, and description thereof will be omitted.

In this embodiment, the throttle opening control device 101 shown in FIG. 8 is constituted by a step motor, and also serves as the throttle valve control actuator 5a and the throttle opening detector 14 in the above embodiment. At the same time, the throttle control signal S (THL) is input as a pulse to change the throttle opening position,
The throttle opening THL is detected based on the integrated value of the pulse. Further, the pump 1 and the motor 2 of this embodiment are of a radial piston type which realizes a capacity change by the eccentricity of the pintle, and the eccentricity control device 102 is provided with the eccentricity means and the speed ratio detector 15 (not shown) in the embodiment. The motor is constituted by a step motor having a function of changing the eccentric position by inputting a speed ratio control signal S (e) as a pulse, and detecting the eccentric position, that is, the speed ratio e by integrating the pulse. ing.

As shown in FIG. 9, the controller 103 has an accelerator operation amount ACC on the horizontal axis and a target vehicle speed V0 on the vertical axis.
10, the target vehicle speed map has characteristics such that the inclination changes in two steps upward to the right and, as shown in FIG. 10, the throttle opening THL is plotted on the horizontal axis, and the target engine speed S is plotted on the vertical axis.
A target engine speed map is stored such that when E0 is taken, the target engine speed map changes linearly upward to the right and then asymptotically approaches a constant value. Thus, the controller 103 of the present embodiment has a function of comparing the actual vehicle speed V with the target vehicle speed V0, the actual engine speed SE and the target engine speed SE.
0 is provided with the function of comparing the vehicle speed deviation with the speed ratio control signal S.
(e), and the engine speed deviation is converted into a throttle control signal S (THL).
That is, the control mode is different from that of the above embodiment in that the vehicle speed deviation is converted into a throttle control signal S (THL) and the engine speed deviation is converted into a speed ratio control signal S (e). . The step motor driving pulse rate (pulses / second) at this time is defined as A × | target vehicle speed V0−actual vehicle speed V |, and the latter is B × | target engine speed SE0−actual, where A and B are constants. The engine speed SE | is defined.

More specifically, as shown in the flowchart of FIG. 11, the actual engine speed SE and the actual vehicle speed V are detected in step S1, and the accelerator depression amount ACC is determined in step S2.
And the throttle opening THL are detected, and a target engine speed SE0 and a target vehicle speed V0 are determined from the maps shown in FIGS. 9 and 10 in step S3. Then, in step S4, it is determined whether or not the target vehicle speed V0 is equal to or higher than the actual vehicle speed V. If YES, a throttle opening increase signal S (THL) is output in step S5, and if NO, in step S6. A throttle opening decrease signal S (THL) is output. In step S7, the target engine speed SE
0 is equal to or greater than the actual engine speed SE, and Y
In the case of ES, a speed ratio decrease signal S (e) is output in step S8, and in the case of NO, a speed ratio increase signal S (e) is output in step S9. That is, in the above embodiment, step S
After step 4, step S8 or S9 is executed.
7 has the opposite relationship to the execution of step S5 or S6. Steps S7 to S7
9 may be performed first, and steps S4 to S6 may be performed later. Alternatively, steps S4 to S6 and steps S7 to S9 may be performed simultaneously by parallel control.

Thus, according to this control, step S
5, the state change of (3-A) described in the above embodiment occurs in the entire system, (3-B) in step S6, (2-B) in step S8, and (2-B) in step S9.
The state changes in A) occur, and the entire system converges to the steady state in (1) while they fuse.

Therefore, according to the control device of this embodiment, similarly to the above-described embodiment, not only can the forklift run at a desired speed, but also the relationship between the engine speed and the throttle opening is adapted to the optimum fuel economy condition. So that the fuel efficiency can be improved more reliably than in the past. Of course, through all the embodiments, since the vehicle speed according to the accelerator operation amount operated by the driver can be obtained, even when it is desired to drive at a constant vehicle speed, it is not necessary to frequently operate the accelerator regardless of the fluctuation of the running load, Further, it is needless to say that a half clutch (inching) operation is not required even at a low speed, and there is an effect that an easy driving can be performed.

The specific configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0037]

The control device for a forklift according to the present invention separates the accelerator from the throttle valve and treats not only the speed ratio but also the throttle opening as an arbitrary control parameter. The vehicle speed control and the engine speed control adapted to the optimum fuel efficiency condition corresponding to the throttle opening can be executed simultaneously, and as a result, not only can the speed operability of the forklift be improved, but also the This has a special effect that the fuel-efficient traveling can be surely performed.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram of the present invention.

FIG. 2 is a conceptual diagram showing a configuration according to an embodiment of the present invention.

FIG. 3 is a graph showing characteristics of the HST used in the embodiment.

FIG. 4 is a diagram showing characteristics of the HST used in the embodiment.
Graph corresponding to.

FIG. 5 is a block diagram showing an outline of control of the embodiment.

FIG. 6 is a graph showing a relationship between a vehicle speed V and a load torque TW in the embodiment.

FIG. 7 is a graph illustrating an optimal fuel consumption line stored in MAP2 in the embodiment.

FIG. 8 is a conceptual diagram showing a configuration according to another embodiment of the present invention.

FIG. 9 is a graph showing characteristics of a target vehicle speed map of the embodiment.

FIG. 10 is a graph showing characteristics of a target engine speed map of the embodiment.

FIG. 11 is a flowchart showing an outline of control of the embodiment.

[Explanation of symbols]

 a, 5 ... Engine b, 6 ... Wheels c, 4 ... Fluid type transmission (HST) d ... Throttle valve e ... Speed ratio f, 11 ... Accelerator depression amount detecting means (detector) g, 12 ... Vehicle speed detecting means ( Detectors) h, 13: engine speed detecting means (detector) i, 14: throttle opening detecting means (detector) j, MAP1: first setting means k, MAP2: second setting means m, 16a .. First comparator n, 16b second comparator o, 7 accelerator p, 16 control means (controller) ACC accelerator depression SE SE engine speed SE0 target engine speed THL throttle opening V: Vehicle speed V0: Target vehicle speed

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-46828 (JP, A) JP-A-56-121836 (JP, A) JP-A-6-144086 (JP, A) JP-A-6-146 117285 (JP, A)

Claims (1)

(57) [Claims] 1. A forklift comprising a hydraulic transmission interposed between an engine and wheels for continuously changing a speed ratio, and an accelerator disconnected from a throttle valve of the engine. On the other hand, accelerator depression amount detection means, vehicle speed detection means, engine speed detection means, throttle opening degree detection means, first setting means for setting a target vehicle speed for the accelerator depression amount, throttle opening Second setting means for setting a target engine speed that satisfies the optimum fuel efficiency condition with respect to the degree, a first comparison unit that compares the actual vehicle speed with the target vehicle speed and outputs a deviation, The second that outputs the deviation by comparing with the engine speed
And a control means for controlling the speed ratio and the throttle opening in such a direction as to cancel both of the deviations output by the first and second comparison units.