JP2022111710A - work vehicle - Google Patents

Abstract

To provide a work vehicle capable of reducing the burden on an operator by eliminating simultaneous operation of an accelerator pedal and a brake pedal required for rise run operation in a dump approach.SOLUTION: A work vehicle 1 includes a target lift speed determination device 21 that determines a target lift speed according to the amount of operation of a lift lever 20, a target vehicle speed determination device 22 for determining a target vehicle speed of the vehicle in accordance with the operation amount of an accelerator pedal 18, a vehicle speed control device 23 that controls a vehicle speed so as to follow the target vehicle speed, and a drive rotation speed control device 24 that controls a rotation speed of a drive source 13. The vehicle speed control device 23 calculates a first requested rotation speed for the drive source 13 so that the vehicle speed follows the target vehicle speed, and outputs the calculated first request rotation speed to the drive rotation speed control device 24. The drive rotation speed control device 24 calculates a second required rotation speed for the drive source 13 based on the target lift speed, and controls the rotation speed of the drive source 13 based on the calculated second required rotation speed and the first required rotation speed.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a working vehicle, and more particularly to a working vehicle equipped with a working machine.

2. Description of the Related Art As a working vehicle equipped with a working machine, for example, a wheel loader is known which has a bucket attached to the tip of a lift arm so as to be able to tilt, scoops up earth and sand, etc., and performs excavation, movement and loading work. Such a working vehicle includes a traveling device for traveling the vehicle together with the working machine, and both the working machine and the traveling device are driven by the driving force from the engine. For this reason, for example, an operator of a working vehicle simultaneously operates the accelerator pedal and the lift lever when lifting the earth and sand scooped up by the bucket of the working machine to the height of the loading platform of the dump truck, which is the transport vehicle. As a result, the work vehicle realizes a so-called "rise run" operation in which the lift arm is raised at the same time as moving forward.

During a rise run, by depressing the accelerator pedal to increase the engine speed, not only the forward speed of the vehicle but also the lifting speed of the lift arm can be increased at the same time. Such a loading operation is also called a "dump approach". However, in loading work in the dump approach, if the distance between the work vehicle and the dump truck is not sufficient, the work vehicle must move to the dump truck before the bucket is raised to a position higher than the dump truck bed. may arrive just before

Therefore, the operator considers the time required to raise the lift arm, and operates the accelerator pedal and brake pedal to balance the speed at which the bucket is raised and the forward speed of the vehicle, so that the work vehicle can move to the side of the dump truck. It is necessary to adjust the time to arrive at In other words, the operator must operate the lift lever, accelerator pedal, and brake pedal while maintaining a delicate balance in order to adjust the forward speed of the vehicle and the lifting speed of the lift arm to realize dump approach. Forced.

As a prior art related to the dump approach, Patent Document 1, for example, describes a work vehicle provided with a forward clutch that can be arbitrarily engaged by a controller between an engine and a travel device. In the work vehicle described in this patent document, on the condition that the brake pedal is operated while at least the accelerator pedal is being operated, the hydraulic pressure of the pressure oil supplied to the forward clutch is adjusted according to the operation amount of the brake pedal. Clutch oil pressure control is performed to lower the

Further, Patent Document 2 describes a working vehicle provided with a variable displacement HST pump connected to an engine and a variable displacement HST motor hydraulically connected to the HST pump in a closed circuit. In the work vehicle described in this patent document, the vehicle speed is limited by controlling the displacement volume of the HST motor according to the amount of depression of the accelerator pedal and the increase in the pilot pressure associated with the lifting operation of the lift lever.

Japanese Patent Application Laid-Open No. 2018-31458 JP 2019-65576 A

However, in the prior art such as the above-mentioned Patent Document 1, it is necessary to add a half-engaged forward clutch to the running device of the vehicle. becomes. In addition, in order to change the degree of engagement of the forward clutch, it is necessary to operate the brake pedal. However, there is a problem that there is no change from the prior art.

On the other hand, in the prior art such as Patent Document 2, by installing an HST type traveling drive system in the traveling device, power distribution between the traveling device and the working machine can be freely controlled by controlling the displacement volume of the HST motor. Since it targets vehicles that can be changed, there is a problem that it cannot be applied to vehicles equipped with a general torque converter type traveling drive system, which has a structure in which the engine and the traveling device are directly connected without a drive system. Furthermore, in order to determine whether the vehicle speed should be suppressed in the dump approach, a large lift lever operation, which is not originally related to vehicle speed determination, is used. There is

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a work vehicle that eliminates the simultaneous operation of an accelerator pedal and a brake pedal, which is required when a rise run operation is performed on a dump approach, thereby reducing the burden on the operator.

A work vehicle according to the present invention includes a vehicle body having wheels, a drive source mounted on the vehicle body, a hydraulic pump driven by the drive source, and a working tool provided at the front end of the vehicle body. a lift arm rotatable in the vertical direction; a lift cylinder driven by pressure oil supplied from the hydraulic pump to raise or lower the lift arm; a lift lever for operating the raising operation of the lift arm; A work vehicle comprising an accelerator pedal that adjusts the vehicle speed of the vehicle and a control device that controls the rotation speed of the drive source, wherein the control device raises the lift arm based on the amount of operation of the lift lever. A target lift speed corresponding to the direction is calculated, a target vehicle speed is calculated based on the operation amount of the accelerator pedal, and the drive source is operated based on the calculated target lift speed and the calculated target vehicle speed. A target rotation speed is calculated, and the rotation speed of the drive source is controlled according to the calculated target rotation speed.

In the work vehicle according to the present invention, the control device calculates the target lift speed corresponding to the lifting direction of the lift arm based on the operation amount of the lift lever, and calculates the target vehicle speed based on the operation amount of the accelerator pedal. , a target rotation speed of the drive source is calculated based on the calculated target lift speed and the calculated target vehicle speed, and the rotation speed of the drive source is controlled according to the calculated target rotation speed. Therefore, the number of revolutions of the drive source can be controlled in consideration of both the amount of operation of the lift lever and the amount of operation of the accelerator pedal. Operation can be saved. As a result, the troublesome operation of simultaneously operating the accelerator pedal and the brake pedal, which is required during a rise run on a dump approach, is eliminated, and simple operation becomes possible, thereby reducing the burden on the operator.

According to the present invention, it is possible to eliminate the simultaneous operation of the accelerator pedal and the brake pedal, which is required during the rise run operation in the dump approach, and to reduce the burden on the operator.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view which shows the vehicle for work which concerns on 1st Embodiment. 1 is a configuration diagram of a work vehicle according to a first embodiment; FIG. 1 is a configuration diagram showing a brake system of a work vehicle according to a first embodiment; FIG. 1 is a configuration diagram of a conventional working vehicle; FIG. 4 is a relational diagram between an operation amount and a target value in the work vehicle according to the first embodiment; FIG. FIG. 2 is a configuration diagram of a work vehicle according to a second embodiment; FIG. 11 is a configuration diagram of a work vehicle according to a third embodiment; FIG. 11 is a configuration diagram of a work vehicle according to a fourth embodiment;

An embodiment of a work vehicle according to the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof will be omitted. Further, in the following description, an example in which the work vehicle is a wheel loader will be described, but the present invention is not limited to the wheel loader, and can also be applied to work vehicles such as forklifts, lift trucks, and telehandlers. . Furthermore, in the following description, the vertical, horizontal, front and rear directions and positions are based on the normal operating condition of the work vehicle, that is, the condition in which the wheels are in contact with the ground.

[First embodiment]
FIG. 1 is a side view showing the work vehicle according to the first embodiment, and FIG. 2 is a configuration diagram of the work vehicle according to the first embodiment. A working vehicle (here, a wheel loader) 1 of this embodiment includes a working machine 11 arranged in the front part of the vehicle, a driver's cab 5 arranged in the substantially central part of the vehicle, and a working machine 1 arranged in the rear part of the vehicle. It has an engine room 6 and wheels 4 that support the entire vehicle. The working machine 11, the driver's cab 5, the engine room 6, and the wheels 4 constitute the "vehicle body" described in the claims.

The work machine 11 includes a pair of left and right lift arms 2 mounted rotatably in the vertical direction, a pair of left and right lift cylinders 7 for raising or lowering the lift arms 2 , and a tip end portion of the lift arms 2 . It has a bucket 3 attached so as to be vertically rotatable, and a bucket cylinder 8 for driving the bucket 3 . The bucket 3 corresponds to the "working tool" described in the claims, and is arranged on the front side of the vehicle body. The bucket 3 is rotated by the expansion and contraction of the bucket cylinder 8 through the bell crank 9, whereby the direction of the bucket 3 can be moved up and down.

The lift cylinder 7 and the bucket cylinder 8 are hydraulic actuators driven by pressure oil supplied from the hydraulic pump 12, respectively. For example, when pressure oil is supplied to the bottom chamber of the lift cylinder 7 by the hydraulic pump 12, the rod 7a of the lift cylinder 7 extends, thereby rotating the lift arm 2 upward (that is, lifting the lift arm). . On the other hand, when pressurized oil is supplied to the rod chamber of the lift cylinder 7, the rod 7a retracts, thereby rotating the lift arm 2 downward (that is, lowering the lift arm).

Further, when pressure oil is supplied to the bottom chamber of the bucket cylinder 8 by the hydraulic pump 12, the rod 8a of the bucket cylinder 8 extends, thereby rotating the bucket 3 upward. On the other hand, when pressurized oil is supplied to the rod chamber of the bucket cylinder 8, the rod 8a retracts, thereby rotating the bucket 3 downward.

The supply of pressure oil to the bottom chambers and rod chambers of the lift cylinder 7 and the bucket cylinder 8 is performed by displacing control valves corresponding to the respective cylinders, and each control valve is displaced by lever operation by the operator. driven by pilot pressure generated by a pilot valve that The hydraulic pump 12 is driven by a drive source 13 such as an engine arranged in the engine room 6 . The drive source 13 is not limited to the engine alone, and may be an electric motor or a hybrid system using both of them.

The working vehicle 1 is equipped with, for example, a torque converter type traveling drive system, and travels by rotating the front and rear wheels 4 . The wheels 4 are rotatably connected via a drive source 13 such as an engine and a drive train, that is, a torque converter 14 , a transmission 15 , a propeller shaft (not shown), and a differential 16 . Further, the drive source 13 described above is connected to both the torque converter 14 and the hydraulic pump 12, so that the rotation speed of each cannot be changed individually.

The work vehicle 1 also includes a brake 10 that applies a braking force to the vehicle by operating a brake pedal 17 . For example, as shown in FIG. 3, the brake 10 has a structure in which hydraulic pressure or the like is used to press a friction material against a rotating member that rotates integrally with the wheel, and the frictional force (i.e., braking force) at that time stops the rotation of the rotating member. have More specifically, in the brake system having the brake 10 shown in FIG. It is controlled by a control valve 103 that

In such a brake system, when the brake pedal 17 is operated (that is, when the brake pedal 17 is stepped on), the pressure oil in the tank 102 is supplied to the brake cylinder 10a, and the urging force of the piston pushes the friction material 10b. It is pressed against the rotating member 10c that rotates integrally with the wheel 4. Thereby, a braking force is generated, the rotation of the wheels 4 is suppressed, and the work vehicle 1 is decelerated.

Therefore, in the work vehicle 1 of this embodiment, the torque generated by the drive source 13 such as the engine is transmitted to the wheels 4 through the power train composed of the torque converter 14 and the like, thereby accelerating the work vehicle 1. On the other hand, the work vehicle 1 can be decelerated by suppressing the rotation of the wheels 4 with the braking force of the brake 10 . The rotational speed of the drive source 13 and the torque of the brake 10 can be controlled by the operator by operating the accelerator pedal 18 and the brake pedal 17 (in other words, the amount of depression).

Further, in the work vehicle 1 using an engine as the drive source 13, the engine ECU controls the fuel injection amount and the like so that the engine speed reaches a target value according to the operation amount of the accelerator pedal 18, thereby increasing the engine output torque. to adjust. As a result, the operator can adjust the vehicle speed by adjusting the operation amount of the accelerator pedal 18 .

Here, based on FIG. 4, the problems of the conventional working vehicle described above will be described in detail. FIG. 4 is a diagram showing the configuration of a conventional working vehicle. Conventionally, the accelerator pedal 18 is connected to the drive source 13, and the drive source 13 is driven so that the number of rotations corresponds to the amount of operation of the accelerator pedal 18 as described above. The drive source 13 is connected to the hydraulic pump 12 and the torque converter 14 and drives both to rotate at the same time. The output of the torque converter 14 is further decelerated by the transmission 15 and the torque is transmitted to the wheels 4 via the differential 16 . The work vehicle is accelerated by this rotational force.

On the other hand, the hydraulic pump 12 pressure-feeds pressure oil by the driving force of the drive source 13 , and the pressure oil is supplied to the lift cylinder 7 via the control valve 19 . The control valve 19 is opened according to the amount of operation of the lift lever 20, and the lift cylinder is opened at a speed corresponding to the amount of pressurized oil supplied in proportion to the rotational speed of the hydraulic pump 12 and the amount of opening of the control valve 19. 7 is extended or retracted. The lift lever 20 is for raising or lowering the lift arm 2 .

That is, in the conventional work vehicle, the amount of operation of the accelerator pedal 18 determines the rotation speed of the drive source 13, so both the extension/retraction speed of the lift cylinder 7 and the vehicle speed are changed. Therefore, even when the operator wishes to increase the expansion/contraction speed of the lift cylinder 7, he steps on the accelerator pedal 18 to increase the rotational speed of the drive source 13. FIG.

However, in this case, the vehicle speed also increases at the same time. Therefore, when the operator wants to keep the vehicle speed low, such as during a rise run on a dump approach, the operator also depresses the brake pedal 17 at the same time to operate the brake 10 so that the vehicle body can move. It is necessary to perform an operation to suppress the acceleration. That is, the operator operates the lift lever 20 while keeping the vehicle speed low while simultaneously balancing the conflicting operations of depressing the accelerator pedal 18, which is an operation to increase the vehicle speed, and depressing the brake pedal 17, which is an operation to decrease the vehicle speed. The complicated operation of doing is forced. Therefore, the burden is heavy especially for an unskilled operator.

In order to solve such a conventional problem, the work vehicle 1 according to this embodiment calculates a target lift speed corresponding to the lifting direction of the lift arm 2 based on the operation amount of the lift lever 20, A target vehicle speed is calculated based on the operation amount of the pedal 18, a target rotation speed of the driving source 13 is calculated based on the calculated target lift speed and the target vehicle speed, and the rotation speed of the driving source 13 is adjusted according to the calculated target rotation speed. is further provided with a control device 27 for controlling the As shown in FIG. 2, the control device 27 includes a target lift speed determination device 21 that determines (in other words, calculates) a target lift speed for raising or lowering the lift arm 2 according to the amount of operation of the lift lever 20; A target vehicle speed determining device 22 that determines (in other words, calculates) the target vehicle speed of the vehicle according to the operation amount of the accelerator pedal 18, and follows (in other words, matches) the target vehicle speed determined by the target vehicle speed determining device 22. ) and a drive rotation speed control device 24 for controlling the rotation speed of the drive source 13 .

The target lift speed determination device 21, the target vehicle speed determination device 22, the vehicle speed control device 23, and the drive rotation speed control device 24 each include, for example, a CPU (Central Processing Unit) that executes calculations, and two programs that record programs for the calculations. It consists of a microcomputer that combines a ROM (Read Only Memory) as a secondary storage device and a RAM (Random Access Memory) as a temporary storage device that saves the progress of calculations and temporary control variables, Control processing such as each determination is performed by executing a stored program.

Specifically, the target lift speed determination device 21 is connected to the lift lever 20 and determines the target lift speed for raising or lowering the lift arm 2 according to the amount of operation of the lift lever 20 . A lift lever 20 is arranged in the driver's cab 5 and raises or lowers the lift arm 2 according to the operation of the operator. Further, in this embodiment, the lift lever 20 is further connected to the target lift speed determination device 21 in addition to the control valve 19 .

The target vehicle speed determining device 22 is connected to the accelerator pedal 18 and determines the target vehicle speed of the vehicle according to the amount of operation of the accelerator pedal 18 . The target lift speed determination device 21 and the target vehicle speed determination device 22 set their respective target values (ie lift arm 2, the target lift speed for raising or lowering or the target vehicle speed of the vehicle) is increased.

Such processing can be realized by performing some function processing in which the output monotonically increases with respect to the input. A configuration may be adopted in which the target value is determined by reference. FIG. 5 shows an example of the relationship between the manipulated variable and the target value set in this table. In FIG. 5, the horizontal axis indicates the input operation amount (for example, the lift lever operation amount or the accelerator pedal operation amount), and the vertical axis indicates the target value to be output (for example, the target lift speed for raising or lowering the lift arm, Alternatively, the target vehicle speed of the vehicle), and it is conceivable to define values such as the line 201, for example. A line 201 is an example of a target value that is a linear function with respect to the amount of operation, and sets a dead zone when the amount of operation is minute and an upper limit value when the amount of operation is excessive.

Other examples of such a table may define values such as lines 202 and 203, for example. An upwardly convex curved table such as the line 202 has characteristics that are sensitive to the initial amount of operation, and a target value that makes the operator feel that the response to the operation is good can be obtained. Conversely, a downwardly convex curved table, such as line 203, has gentle characteristics with respect to the initial amount of operation, and provides target values that make it easy for the operator to make fine adjustments.

By performing table processing for determining the target lift speed of the target lift speed determination device 21 and the target vehicle speed of the target vehicle speed determination device 22 in this way, it is possible to arbitrarily set the operation characteristics. Applications such as switching according to preference or switching according to the work situation are conceivable.

The drive rotation speed control device 24 is arranged, for example, between the target lift speed determination device 21 and the drive source 13, and is connected to the target lift speed determination device 21 and the drive source 13, respectively. Based on the target lift speed determined by the target lift speed determination device 21, the drive rotation speed control device 24 calculates a second required rotation speed for the drive source 13, and combines the calculated second required rotation speed with the vehicle speed control device. Based on the first required rotation speed (described later) output from 23, the target rotation speed of the drive source 13 is further calculated, and the rotation speed of the drive source 13 is controlled according to the calculated target rotation speed. As a method for calculating the second required rotation speed for the drive source 13, for example, the amount of pressure oil required to be supplied to the lift cylinder 7 to achieve the target lift speed for raising or lowering the lift arm 2 is calculated. It is obtained by calculating the number of revolutions of the hydraulic pump 12 that can be supplied.

Specifically, when the expansion and contraction speed of the lift cylinder 7 corresponding to the target lift speed is vc, the piston area of the lift cylinder 7 is S, and the discharge flow rate per revolution of the hydraulic pump in this case is Q, the drive source 13 The second required rotation speed rp to is obtained by equation (1).
rp = (vc · S) / Q (Equation 1)

The vehicle speed control device 23 is arranged between the target vehicle speed determination device 22 and the brake 10, and controls the vehicle speed of the vehicle. Specifically, the vehicle speed control device 23 calculates the first required rotation speed for the drive source 13 so that the vehicle speed follows the target vehicle speed output by the target vehicle speed determination device 22 . As a method of calculating the first required rotation speed of the drive source 13, for example, the rotation speed of the drive source 13 corresponding to the target speed of the vehicle is calculated in the same manner as the target lift speed for raising or lowering the lift arm 2 described above. obtained by

Specifically, since the rotational speed ratio of the torque converter 14 approaches 1 during constant-speed running, the final rotational speed ratio is set to about Gc≈1, the gear ratio of the transmission 15 is set to Gt, and the gear ratio of the differential 16 is set to Gt. When Gf is the radius of the wheel 4, Rt is the radius of the wheel 4, and v is the target vehicle speed, the first required rotational speed re to the drive source 13 is obtained by the formula (2).
re = (v · Gc · Gt · Gf) / (2π · Rt) (Formula 2)

As shown in FIG. 2, the vehicle speed control device 23 is further connected to the drive rotation speed control device 24, and outputs the calculated first required rotation speed re to the drive source 13 to the drive rotation speed control device 24, thereby controlling the speed of the vehicle. A request is made to the drive source 13 via the drive rotation speed control device 24 to follow the target vehicle speed. By doing so, the vehicle speed control device 23 controls the vehicle speed of the vehicle so as to follow the target vehicle speed determined by the target vehicle speed determination device 22 .

Then, the vehicle speed control device 23 inputs a required value of the drive source rotation speed (that is, the first required rotation speed) to achieve the target vehicle speed. In addition to the required value of the drive source rotation speed (i.e., the second required rotation speed) necessary to realize the target lift speed of raising or lowering, the target rotation speed of the drive source is set based on these two required rotation speeds. The rotational speed of the drive source 13 is controlled according to the calculated target rotational speed.

The vehicle speed control device 23 is further connected to the brake 10. For example, when the actual rotation speed of the drive source 13 is higher than the first required rotation speed re, the vehicle speed eventually becomes higher than the target vehicle speed of the vehicle. Therefore, the vehicle speed is suppressed by appropriately outputting a braking request to the brake 10 . In this case, the braking system shown in FIG. 3 is configured so that, for example, a solenoid 103a is added to the control valve 103 so that braking force can be generated even when the vehicle speed control device 23 requests braking. be done.

In the work vehicle 1 of the present embodiment configured as described above, the vehicle speed control device 23 controls the vehicle speed of the vehicle to follow the target vehicle speed determined by the target vehicle speed determination device 22. The required rotation speed is calculated, and the calculated first required rotation speed is output to the drive rotation speed control device 24, and the drive rotation speed control device 24 drives based on the target lift speed determined by the target lift speed determination device 21. A second required rotation speed of the drive source 13 is calculated, and a target rotation speed of the drive source 13 is calculated based on the calculated second required rotation speed and the first required rotation speed output from the vehicle speed control device 23, and this The rotation speed of the drive source 13 is controlled according to the calculated target rotation speed.

That is, as described with reference to FIG. 4, in the conventional work vehicle, the rotation speed of the drive source 13 is controlled only by the accelerator pedal 18, whereas in the work vehicle 1 of the present embodiment, the lift lever 20 is operated. It is possible to control the rotation speed of the drive source 13 by considering both the amount and the operation amount of the accelerator pedal 18 . As a result, unnecessary operations such as operating the accelerator pedal 18 in order to increase the lifting speed of the lift arm 2 can be omitted. As a result, the troublesome operation of simultaneously operating the accelerator pedal 18 and the brake pedal 17, which is required at the time of the rise run on the dump approach, is eliminated, and simple operation becomes possible, so that the burden on the operator can be reduced.

Further, the operation amount of the lift lever 20 and the operation amount of the accelerator pedal 18 can be used to directly instruct the lifting or lowering speed of the lift arm 2 and the vehicle speed, respectively, so that the operator's operation becomes more intuitive. These effects can be expected to further improve the workability and safety of the work vehicle 1 .

[Second embodiment]
A second embodiment of the present invention will be described below with reference to FIG. The work vehicle 1A of this embodiment differs from the above-described first embodiment in that it further has a braking request to the brake 10 by operating the brake pedal 17 . Since other structures are the same as those of the first embodiment, redundant description will be omitted.

Specifically, in the work vehicle 1A of the present embodiment, in addition to the braking request function to the brake 10 by the vehicle speed control device 23 as in the first embodiment, the braking request to the brake 10 by operating the brake pedal 17 It has more functions.

According to the work vehicle 1A of this embodiment, in addition to obtaining the same effects as those of the above-described first embodiment, the function of requesting braking to the brake 10 by operating the brake pedal 17 is further provided. In the event of a pedestrian running out, the operator can operate the brake pedal 17 to limit the vehicle speed, thereby further enhancing safety.

[Third embodiment]
A third embodiment of the present invention will be described below with reference to FIG. The work vehicle 1B of this embodiment differs from the above-described first embodiment in that a vehicle speed detection device 25 is further provided. Since other structures are the same as those of the first embodiment, redundant description will be omitted.

That is, in the above-described first embodiment, the vehicle speed control device 23 sets the first requested rotation speed to the drive source 13 so that the vehicle speed follows the target vehicle speed determined by the target vehicle speed determination device 22 . decided to calculate Specifically, the first required rotation speed was calculated by calculating the rotation speeds of the wheels, the drive train, and the drive source corresponding to the target vehicle speed. On the other hand, in this embodiment, by providing the vehicle speed detection device 25 for detecting the vehicle speed, it becomes possible to control the drive source rotation speed with higher responsiveness to the target vehicle speed.

As shown in FIG. 7 , the vehicle speed detection device 25 is mounted, for example, near the transmission 15 , detects the vehicle speed by detecting rotation pulses of the output shaft of the transmission 15 , and outputs the detected result to the vehicle speed control device 23 . is configured to The vehicle speed detection device 25 may be configured to detect the vehicle speed by directly detecting rotation pulses of the four wheels 4 and averaging them.

Then, the vehicle speed control device 23 calculates the first requested rotation speed for the drive source 13 based on the relationship between the vehicle speed detected by the vehicle speed detection device 25 and the target vehicle speed. As a calculation method, for example, a control value calculation method classified as feedback control, that is, a difference between the detected vehicle speed and the target vehicle speed is calculated, and an appropriate control gain is integrated to obtain the first requested rotation of the drive source 13. A method of calculating a number is mentioned.

In addition, a control value calculation method classified as feedback combined feedforward control, that is, a required rotation speed based on the difference between the detected vehicle speed and the target vehicle speed, and a required rotation speed based on the rotation speed ratio shown in the first embodiment. are combined to obtain the first required rotation speed for the drive source 13 . This method has the effect of improving the responsiveness as compared with the control value calculation method classified as feedback control described above.

According to the working vehicle 1B of the present embodiment, in addition to obtaining the same effects as those of the above-described first embodiment, the following effects can also be obtained. That is, by providing the vehicle speed detection device 25 for detecting the vehicle speed, it becomes possible to control the drive source rotation speed with higher responsiveness to the target vehicle speed. In addition, since the vehicle speed control device 23 calculates the first requested rotation speed to the drive source 13 based on the difference between the detected vehicle speed and the target vehicle speed, responsiveness can be improved. Similarly, in this case, since the difference between the detected vehicle speed and the target vehicle speed is also used for controlling the braking force output to the brake 10, more accurate control is possible. In this manner, the vehicle speed control error and the static stabilization time are calculated by calculating the first requested rotation speed and the braking request to the drive source 13 based on the difference between the vehicle speed detected by the vehicle speed detection device 25 and the target vehicle speed. can be reduced.

[Fourth embodiment]
A fourth embodiment of the present invention will be described below with reference to FIG. The work vehicle 1C of this embodiment differs from the above-described first embodiment in that it further includes a lift speed detection device 26 . Since other structures are the same as those of the first embodiment, redundant description will be omitted.

That is, in the above-described first embodiment, the drive rotation speed control device 24 controls the target lift speed determined by the target lift speed determination device 21 so that the hydraulic pump rotation speed is such that the required flow rate of pressure oil can be secured. , the second required rotation speed to the drive source 13 is calculated. Specifically, the expansion and contraction speed of the lift cylinder 7 corresponding to the target lift speed is multiplied by the piston area to calculate the pressure oil flow rate required per unit time, and the pressure oil flow rate required per unit time is divided by the discharge flow rate per revolution of the hydraulic pump. 2 The required rotation speed was calculated. On the other hand, in the present embodiment, feedback control is performed by providing the lift speed detection device 26, so that control of the drive source rotation speed with high responsiveness to the target lift speed for raising or lowering the lift arm 2 can be performed. be possible.

As shown in FIG. 8, the lift speed detection device 26 is, for example, a stroke sensor that detects the amount of displacement (stroke) of the lift cylinder 7, and detects the extension/retraction speed of the lift cylinder 7 based on the change of the stroke sensor per unit time. By calculating, the lifting or lowering speed of the lift arm 2 is detected. Then, the lift speed detection device 26 outputs the detection result to the drive rotation speed control device 24 . The lift speed detection device 26 is, for example, an angle sensor provided on the rotating shaft 11a on the base end side of the lift arm 2 in FIG. It may be configured to detect the speed of raising or lowering the lift arm 2 by calculating the angular velocity.

Then, the drive rotation speed control device 24 sets the second required rotation speed of the drive source 13 based on the relationship between the lifting or lowering speed of the lift arm 2 detected by the lift speed detection device 26 and the target lift speed. calculate. As a calculation method, for example, in the same manner as in the third embodiment, the difference between the detected lifting or lowering speed of the lift arm 2 and the target lift speed is calculated, and an appropriate control gain is added to the difference to calculate the power supply to the drive source 13. There is a method of calculating the second required rotation speed.

According to the working vehicle 1C of the present embodiment, in addition to obtaining the same effects as those of the above-described first embodiment, the following effects can also be obtained. That is, by providing the lift speed detector 26, it is possible to control the drive source rotation speed with higher responsiveness to the target lift speed for raising or lowering the lift. Further, since the drive rotation speed control device 24 calculates the second required rotation speed for the drive source 13 based on the difference between the detected lifting or lowering speed of the lift arm 2 and the target lift speed, the responsiveness is improved. be able to. Thus, by calculating the second required rotation speed for the drive source 13 based on the difference between the lift arm 2 raising or lowering speed detected by the lift speed detector 26 and the target lift speed, the lift It is possible to reduce the control error of the raising or lowering speed of the arm 2 and the reduction of the stabilization time.

[Fifth embodiment]
In any of the above-described first to fourth embodiments, the drive rotation speed control device 24 controls the drive source 13 based on the calculated second required rotation speed and the first required rotation speed output from the vehicle speed control device 23. In the present embodiment, the drive rotation speed control device 24 uses the larger one of the first required rotation speed and the second required rotation speed to calculate the target rotation speed of the drive source 13. Calculate

In this way, the drive rotation speed control device 24 calculates the target rotation speed of the drive source 13 by adopting the larger one of the first required rotation speed and the second required rotation speed, and further calculates the calculated target rotation speed. By controlling the number of rotations of the drive source 13 according to the number, sufficient driving force can be supplied to both the target lift speed and the target vehicle speed. Allows you to work more efficiently.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the invention described in the claims. Changes can be made.

1, 1A, 1B, 1C Working Vehicle 2 Lift Arm 3 Bucket 4 Wheel 5 Driver's Room 6 Engine Room 7 Lift Cylinder 8 Bucket Cylinder 10 Brake 11 Work Machine 12 Hydraulic Pump 13 Drive Source 17 Brake Pedal 18 Accelerator Pedal 20 Lift Lever 21 Target lift speed determination device 22 Target vehicle speed determination device 23 Vehicle speed control device 24 Drive rotation speed control device 25 Vehicle speed detection device 26 Lift speed detection device 27 Control device

Claims (7)

a vehicle body with wheels;
a driving source mounted on the vehicle body;
a hydraulic pump driven by the drive source;
a lift arm provided on the front side of the vehicle body and having a working tool at its tip and capable of rotating in the vertical direction;
a lift cylinder driven by pressure oil supplied from the hydraulic pump to raise or lower the lift arm;
a lift lever for operating the lifting operation of the lift arm;
an accelerator pedal for adjusting the speed of the vehicle;
A work vehicle comprising a control device that controls the rotation speed of the drive source,
The control device is
calculating a target lift speed corresponding to the lifting direction of the lift arm based on the amount of operation of the lift lever;
calculating a target vehicle speed based on the amount of operation of the accelerator pedal;
A target rotation speed of the drive source is calculated based on the calculated target lift speed and the calculated target vehicle speed, and the rotation speed of the drive source is controlled according to the calculated target rotation speed. work vehicle. The control device calculates a first request rotation speed to the drive source so that the vehicle speed of the vehicle follows the calculated target vehicle speed, and issues a second request to the drive source based on the calculated target lift speed. 2. The working vehicle according to claim 1, wherein the number of revolutions is calculated, and the target number of revolutions of the drive source is calculated based on the calculated first required number of revolutions and second required number of revolutions. The control device calculates the rotation speed of the hydraulic pump based on the flow rate of pressure oil required to be supplied to the lift cylinder to achieve the calculated target lift speed, and calculates the calculated rotation speed of the hydraulic pump. 3. The work vehicle according to claim 2, wherein a second required rotation speed for said drive source is calculated based on the rotation speed. Further comprising a vehicle speed detection device for detecting the vehicle speed of the vehicle,
The work vehicle according to claim 2 or 3, wherein the control device calculates the first required rotation speed for the drive source based on the difference between the vehicle speed detected by the vehicle speed detection device and the target vehicle speed. The work vehicle according to claim 2 or 3, wherein the control device calculates the target rotation speed of the drive source by using the larger one of the first required rotation speed and the second required rotation speed. A vehicle speed detection device for detecting a vehicle speed of the vehicle is further provided, and when the vehicle speed detected by the vehicle speed detection device is higher than the target vehicle speed, the control device controls a brake provided on the vehicle to increase the vehicle speed. The vehicle for work according to any one of claims 1 to 3, which suppresses. further comprising a lift speed detection device that detects the speed of raising or lowering the lift arm;
The control device calculates a second requested rotation speed for the drive source based on a difference between the lift arm raising or lowering speed detected by the lift speed detecting device and the calculated target lift speed. 6. A working vehicle according to Item 2 or 5.

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