WO2021182421A1

WO2021182421A1 - Work vehicle

Info

Publication number: WO2021182421A1
Application number: PCT/JP2021/009080
Authority: WO
Inventors: 祐樹抜井; 泰典宮本; 幸次兵藤
Original assignee: 日立建機株式会社
Priority date: 2020-03-09
Filing date: 2021-03-08
Publication date: 2021-09-16
Also published as: JP2023052712A

Abstract

Provided is a work vehicle that is unlikely to undergo drastic deceleration even when a signal line for electronic control of the capacity of a hydraulic pump is interrupted during travel.　A wheel loader 1 that travels using an HST-type travel drive system, the wheel loader 1 being provided with: a controller 5 that controls a travel hydraulic pump 31 and a travel hydraulic motor 32; a pump tilt control device 310 that controls the pump tilt angle of the travel hydraulic pump 31 on the basis of a pump command signal outputted from the controller 5; and a motor tilt control device 320 that controls the motor tilt angle of the travel hydraulic motor 32 on the basis of a motor command signal outputted from the controller 5, wherein when an abnormal state of the pump command signal is determined on the basis of the pump command signal, the controller 5 controls the motor tilt angle so as to become smaller than the motor tilt angle when the pump command signal is outputted normally to the pump tilt control devices 310, 310A from the controller 5 immediately before the abnormal is determined.

Description

Work vehicle

The present invention relates to a work vehicle equipped with an HST type traveling drive system.

As a general running drive system for work vehicles such as wheel loaders and forklifts, the hydraulic pump and hydraulic motor are connected in a closed circuit, and the hydraulic pressure generated by driving the hydraulic pump with the engine is converted into rotational force by the hydraulic motor. An HST type traveling drive system that converts the driving force into traveling driving force is known.

For example, in Patent Document 1, a variable-capacity traveling hydraulic pump driven by an engine and a variable-capacity driving hydraulic pump driven by hydraulic oil discharged from the traveling hydraulic pump are used in a main hydraulic circuit which is a closed circuit. A forklift including a hydraulic motor and traveling a vehicle by transmitting the driving force of the hydraulic motor to wheels is disclosed. In this forklift, the capacity of the traveling hydraulic pump is increased by operating the pump capacity control cylinder with a forward electromagnetic proportional valve and a reverse electromagnetic proportional valve that operate according to a command signal given from the control device via a signal line. (Slanted plate tilt angle) is changed.

In this way, the pump capacity control cylinder can be electronically controlled independently on the forward side and the reverse side by the command signal output from the control device, so that the pump capacity control is hydraulically performed using a throttle or a valve. Compared with the case of controlling the cylinder, the responsiveness of the change of the tilt angle in the traveling hydraulic pump is improved.

Japanese Patent No. 6335340

However, in the forklift described in Patent Document 1, the tilt piston of the traveling hydraulic pump operates quickly as much as the response of the tilt control of the traveling hydraulic pump is good, so that the vehicle speed tends to change suddenly. When the vehicle is operating in a normal state, it is possible to control the tilt of the traveling hydraulic pump according to the command signal output from the control device. If the signal line between the forward electromagnetic proportional valve and the valve is broken, the pressure oil that controls the tilt of the traveling hydraulic pump is returned to the hydraulic oil tank, the tilting piston becomes neutral, and the traveling hydraulic pump becomes neutral. The discharge flow rate of is 0 (zero). As a result, the forklift will suddenly decelerate and easily lose its balance.

Therefore, an object of the present invention is to provide a work vehicle that does not easily decelerate suddenly even when a signal line for electronically controlling the capacity of a traveling hydraulic pump is disconnected.

In order to achieve the above object, the present invention comprises a vehicle body provided with a plurality of wheels, an engine mounted on the vehicle body, a variable displacement traveling hydraulic pump driven by the engine, and the traveling. A variable displacement traveling hydraulic motor that is connected to the hydraulic pump in a closed circuit and transmits the driving force of the engine to the plurality of wheels, a controller that controls the traveling hydraulic pump and the traveling hydraulic motor, and the like. Based on the pump tilt control device that controls the push-out volume of the traveling hydraulic pump based on the pump command signal output from the controller and transmitted via the signal line, and the motor command signal output from the controller. In a work vehicle provided with a motor tilt control device for controlling the push-out volume of the traveling hydraulic motor, the controller is said to be based on the pump command signal transmitted from the controller to the pump tilt control device. When the abnormal state of the pump command signal is determined, the push-out volume of the traveling hydraulic motor when the pump command signal is normally output from the controller immediately before determining the abnormal state to the pump tilt control device is used. It is characterized in that the push-out volume of the traveling hydraulic motor is controlled so as to be small.

According to the present invention, even when the signal line for electronically controlling the capacity of the traveling hydraulic pump is disconnected, sudden deceleration of the vehicle body can be avoided. Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is an external side view which shows one structural example of the wheel loader which concerns on each embodiment of this invention. It is a figure which shows one configuration example of the drive system of the wheel loader which concerns on 1st Embodiment. It is a functional block diagram which shows the function which the controller which concerns on 1st Embodiment has. It is a flowchart which shows the flow of the process executed by the controller which concerns on 1st Embodiment. It is a functional block diagram which shows the function which the controller which concerns on 2nd Embodiment has. It is a flowchart which shows the flow of the process executed by the controller which concerns on 2nd Embodiment. It is a functional block diagram which shows the function which the controller which concerns on 3rd Embodiment has. It is a flowchart which shows the flow of the process executed by the controller which concerns on 3rd Embodiment. It is a functional block diagram which shows the function which the controller which concerns on 4th Embodiment has. It is a flowchart which shows the flow of the process executed by the controller which concerns on 4th Embodiment. It is a flowchart which shows the flow of the process executed by the controller which concerns on 5th Embodiment. It is a figure which shows one configuration example of the drive system of the wheel loader which concerns on 6th Embodiment.

Hereinafter, as one aspect of the work vehicle according to each embodiment of the present invention, a wheel loader that performs cargo handling work of excavating a work object such as earth and sand or minerals and loading it on a dump truck or the like will be described.

<Overall configuration of wheel loader 1>
First, the overall configuration of the wheel loader 1 according to each embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a side view showing the appearance of the wheel loader 1 according to the embodiment of the present invention.

The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center. Specifically, the front frame 1A, which is the front part of the vehicle body, and the rear frame 1B, which is the rear part of the vehicle body, are rotatably connected in the left-right direction by the center joint 10, and the front frame 1A is connected to the rear frame 1B. On the other hand, it bends in the left-right direction.

The vehicle body is provided with four wheels 11, two wheels 11 as front wheels 11A on the left and right sides of the front frame 1A, and the remaining two wheels 11 as rear wheels 11B on the left and right sides of the rear frame 1B. ing. Note that, in FIG. 1, of the pair of left and right front wheels 11A and rear wheels 11B, only the left front wheels 11A and rear wheels 11B are shown. Further, the specific number of the plurality of wheels 11 provided on the vehicle body is not particularly limited.

A hydraulically driven cargo handling work device 2 used for cargo handling work is attached to the front part of the front frame 1A. The cargo handling work device 2 serves as a lift arm 21 having a base end attached to the front frame 1A, two lift arm cylinders 22 for driving the lift arm 21, and a work tool attached to the tip of the lift arm 21. It has a bucket 23, a bucket cylinder 24 for driving the bucket 23, and a bell crank 25 rotatably connected to the lift arm 21 to form a link mechanism between the bucket 23 and the bucket cylinder 24. The two lift arm cylinders 22 are arranged side by side in the left-right direction of the vehicle body, but in FIG. 1, only the lift arm cylinder 22 arranged on the left side is shown by a broken line.

The lift arm 21 rotates upward with respect to the front frame 1A by supplying hydraulic oil to the bottom chambers of the two lift arm cylinders 22 and extending the rod 220, and the rods of the two lift arm cylinders 22 respectively. The hydraulic oil is supplied to the chamber and the rod 220 contracts to rotate downward with respect to the front frame 1A.

Similarly, the bucket 23 is tilted (rotated upward with respect to the lift arm 21) by supplying hydraulic oil to the bottom chamber of the bucket cylinder 24 and extending the rod 240, and enters the rod chamber of the bucket cylinder 24. The hydraulic oil is supplied and the rod 240 contracts to dump (rotate downward with respect to the lift arm 21).

The bucket 23 can be replaced with various attachments such as blades, and the wheel loader 1 performs various operations such as soil pushing work and snow removal work in addition to excavation work using the bucket 23. You can also do it.

In the rear frame 1B, a balance is maintained between the driver's cab 12 on which the operator is boarded, the machine room 13 for accommodating each device necessary for driving the wheel loader 1, and the cargo handling work device 2 so that the vehicle body does not tilt. A counter weight 14 for this purpose is provided. In the rear frame 1B, the driver's cab 12 is arranged at the front, the counterweight 14 is arranged at the rear, and the machine room 13 is arranged between the driver's cab 12 and the counterweight 14.

Hereinafter, the configuration of the traveling drive system of the wheel loader 1 will be described for each embodiment.

<First Embodiment>
The traveling drive system of the wheel loader 1 according to the first embodiment of the present invention will be described with reference to FIGS. 2 to 4.

(Overall configuration of the driving drive system)
First, the overall configuration of the traveling drive system of the wheel loader 1 will be described with reference to FIG.

FIG. 2 is a diagram showing a configuration example of the drive system of the wheel loader 1 according to the first embodiment.

In the wheel loader 1, the traveling hydraulic pump 31 and the traveling hydraulic motor 32 are connected by a pair of

hydraulic pipelines

301 and 302 in a closed circuit, and the traveling hydraulic pump 31 is driven by the engine 30. The vehicle body is driven by the HST type traveling drive system in which the hydraulic pressure is converted into the rotational force by the traveling hydraulic motor 32 and used as the traveling driving force.

In addition to the traveling hydraulic pump 31, the engine 30 operates on a charge pump 31A for supplying hydraulic oil for controlling the traveling hydraulic pump 31 and a cargo handling hydraulic circuit 20 for driving the cargo handling work device 2. A cargo handling hydraulic pump 33 for supplying oil is connected. In FIG. 2, the cargo handling hydraulic pump 33 is a variable capacity type hydraulic pump, but the present invention is not limited to this, and a fixed capacity type hydraulic pump may be used.

The traveling hydraulic pump 31 is a sloping plate type or sloping shaft type variable displacement hydraulic pump in which the push-out volume is controlled according to the tilt angle (tilt amount). The tilt angle is controlled by the pump tilt control device 310 based on the pump command signal output from the controller 5.

The pump tilt control device 310 includes a pump tilt cylinder 311 that moves the tilt of the traveling hydraulic pump 31 by supplying pressure oil discharged from the charge pump 31A, and a pump tilt cylinder 311 when the vehicle body moves forward. The forward side pump tilt control valve 312 for controlling the pump tilt control valve 312 and the reverse side pump tilt control valve 313 for controlling the pump tilt cylinder 311 when the vehicle body is moving backward are provided.

The forward pump tilt control valve 312 is based on a forward pump command signal (hereinafter, simply referred to as “forward pump command signal”) output from the controller 5 and transmitted via the forward signal line 41. , An electromagnetic proportional pressure reducing valve that reduces the pressure on the forward side (acting pressure on the forward side) acting on the pump tilting cylinder 311.

Similarly, the reverse pump tilt control valve 313 is referred to as a reverse pump command signal (hereinafter, simply referred to as "reverse pump command signal") output from the controller 5 and transmitted via the reverse signal line 42. ), It is an electromagnetic proportional pressure reducing valve that reduces the pressure on the reverse side (acting pressure on the reverse side) acting on the pump tilting cylinder 311.

The forward / backward movement of the vehicle body is switched by the forward / backward changeover switch 122 as the forward / backward changeover device provided in the driver's cab 12 (see FIG. 1). Further, when the hydraulic pressure acting on the pump tilting cylinder 311 is balanced (acting pressure on the forward side = acting pressure on the reverse side), the pump tilting cylinder 311 is in a neutral state and is discharged from the traveling hydraulic pump 31. The flow rate of the hydraulic oil to be generated becomes 0 (zero) and the vehicle body stops.

The traveling hydraulic motor 32 is a swash plate type or sloping shaft type variable displacement hydraulic motor in which the push-out volume is controlled according to the tilt angle (tilt amount). The tilt angle is controlled by the motor tilt control device 320 based on the motor command signal output from the controller 5.

The motor tilt control device 320 controls the motor tilt cylinder 321 and the motor tilt cylinder 321 that move the tilt of the traveling hydraulic motor 32 by supplying the hydraulic oil discharged from the traveling hydraulic pump 31. A motor tilt control valve 322 is provided.

The motor tilt control valve 322 has a first switching position 322A for contracting the rod 321A of the motor tilt cylinder 321 and a second for extending the rod 321A of the motor tilt cylinder 321 based on the motor command signal output from the controller 5. The 2 switching position 322B is switched.

When the motor tilt control valve 322 is switched to the first switching position 322A (state shown in FIG. 2), the motor tilt cylinder 321 travels while the hydraulic oil discharged from the bottom chamber 321B flows into the hydraulic oil tank 34. The hydraulic oil discharged from the hydraulic pump 31 flows into the rod chamber 321C. As a result, the rod 321A contracts, and the tilt angle of the traveling hydraulic motor 32 is controlled to decrease.

On the other hand, in the motor tilt cylinder 321, when the motor tilt control valve 322 is switched to the second switching position 322B, the hydraulic oil discharged from the rod chamber 321C and the hydraulic oil discharged from the traveling hydraulic pump 31 are in the bottom chamber. It flows into 321B. As a result, the rod 321A is extended, and the tilt angle of the traveling hydraulic motor 32 is controlled to increase.

In the HST type traveling drive system, first, when the operator depresses the accelerator pedal 121 provided in the driver's cab 12, the engine 30 rotates, and the traveling hydraulic pump 31 is driven by the driving force of the engine 30. Then, the traveling hydraulic motor 32 is rotationally driven by the hydraulic oil discharged from the traveling hydraulic pump 31, and the output torque from the traveling hydraulic motor 32 is transmitted to the four wheels 11 via the transmission 15 and the axle 16. As a result, the wheel loader 1 runs.

At this time, when the forward / backward changeover switch 122 is used to switch to the forward side, the hydraulic oil discharged from the traveling hydraulic pump 31 is sent to the forward side hydraulic line 301 of the pair of

hydraulic lines

301 and 302. It is guided and flows into the traveling hydraulic motor 32, and the traveling hydraulic motor 32 rotates in the forward direction, so that the vehicle body travels forward. On the other hand, when the forward / backward changeover switch 122 switches to the reverse side, the hydraulic oil discharged from the traveling hydraulic pump 31 is guided to the traveling hydraulic pipeline 302 and flows into the traveling hydraulic motor 32. As the traveling hydraulic motor 32 rotates in the reverse direction, the vehicle body travels backward.

The pressure generated in the forward side hydraulic line 301 (HST main circuit pressure at the time of forward movement) is the pressure generated in the reverse side hydraulic line 302 (HST main circuit pressure at the time of reverse movement) by the first pressure sensor 43A. Are detected by the second pressure sensor 43B, respectively. Further, a pair of high-

pressure relief valves

351 and 352 are provided on the connecting pipe 303 connecting the pair of

hydraulic pipes

301 and 302. The connection line 303 is branched from between the pair of high-

pressure relief valves

351 and 352 and connected to the hydraulic oil tank 34, and the low-pressure relief valve 353 is provided on the branch line.

In this HST type traveling drive system, when the rotation speed of the engine 30 decreases, the discharge flow rate from the traveling hydraulic pump 31 decreases and the flow rate of the hydraulic oil flowing into the traveling hydraulic motor 32 decreases, so that the traveling hydraulic motor The number of rotations of 32 is reduced and the vehicle speed of the wheel loader 1 is limited. Further, in this case, if the tilt angle of the traveling hydraulic motor 32 is largely controlled by the motor tilt control device 320, the output torque of the traveling hydraulic motor 32 becomes smaller, so that the vehicle speed of the wheel loader 1 is further limited. Can be done.

On the contrary, when the rotation speed of the engine 30 increases, the discharge flow rate from the traveling hydraulic pump 31 increases and the flow rate of the hydraulic oil flowing into the traveling hydraulic motor 32 increases, so that the rotation speed of the traveling hydraulic motor 32 increases. The vehicle speed of the wheel loader 1 increases. Further, in this case, if the tilt angle of the traveling hydraulic motor 32 is controlled to be small by the motor tilt control device 320, the output torque of the traveling hydraulic motor 32 becomes large, so that the vehicle speed of the wheel loader 1 is further increased. Can be done.

Further, the wheel loader 1 is provided with a speed stage switch 123 as a speed stage selection device for selecting the speed stage of the vehicle body in the driver's cab 12. By operating the speed stage switch 123, the gear combination of the transmission 15 is changed, and a desired speed stage is selected from the four speed stages. The speed stage switch 123 is mainly used for the forward traveling of the wheel loader 1.

The 1st speed stage is the lowest speed stage (lowest speed stage), and is selected at the time of work requiring traction force such as excavation work and hill climbing work. The two speed stages are speed stages set one step larger than the first speed stage, which is the lowest speed stage, and are selected, for example, during a dump approach operation. These 1st speed stage and 2nd speed stage correspond to "low speed stage". The 3rd speed stage is a speed stage set one step larger than the 2nd speed stage, and the 4th speed stage is a speed stage set 1 step larger than the 3rd speed stage and is the maximum speed stage. These 3 speed stages and 4 speed stages are selected, for example, when transporting a load, and correspond to "medium to high speed stages".

The wheel loader 1 controls (shifts) the vehicle speed by continuously increasing or decreasing the discharge flow rate of the traveling hydraulic pump 31, and further electronically controls the traveling hydraulic pump 31 and the traveling hydraulic motor 32 by the controller 5. It improves responsiveness and enables smooth start, deceleration, and stop with less impact.

However, for example, if the forward signal line 41 or the reverse signal line 42 is disconnected, the pump command signal output from the controller 5 is transmitted to the forward pump tilt control valve 312 and the reverse pump tilt control valve 313. The hydraulic oil acting on the pump tilting cylinder 311 is returned to the hydraulic oil tank 34. Along with this, the pump tilting cylinder 311 is in a neutral state and the discharge flow rate of the traveling hydraulic pump 31 becomes 0 (zero), so that a braking force is generated and the vehicle body suddenly decelerates and stops. Therefore, in the present embodiment, when such a situation occurs, the controller 5 controls the tilt angle of the traveling hydraulic motor 32 to avoid sudden deceleration of the vehicle body.

In the following, assuming that the pump command signal is not output from the controller 5 to the pump tilt control device 310, the disconnection of the forward side signal line 41 and the reverse side signal line 42 will be described as an example, but the present invention is not limited to this. , The case where the forward side pump tilt control valve 312, the reverse side pump tilt control valve 313, or the controller 5 fails is also included when the pump command signal is not output from the controller 5 to the pump tilt control device 310. Is done.

Further, in the case of "when the pump command signal is not output from the controller 5 to the pump tilt control device 310", the output of the pump command signal from the controller 5 is stopped, and the pump command signal is output from the controller 5. However, both cases are included in which the output of the pump command signal is cut off in the middle and is not transmitted to the pump tilt control device 310.

(Configuration of controller 5)
Next, the configuration of the controller 5 will be described with reference to FIG.

FIG. 3 is a functional block diagram showing the functions of the controller 5 according to the first embodiment.

The controller 5 is configured by connecting a CPU, RAM, ROM, HDD, input I / F, and output I / F to each other via a bus. Then, various operating devices such as the accelerator pedal 121 and the forward / backward changeover switch 122, and various sensors are connected to the input I / F, and the forward side pump tilt control valve 312, the reverse side pump tilt control valve 313, and the reverse side pump tilt control valve 313, and A motor tilt control valve 322 or the like is connected to the output I / F.

In such a hardware configuration, the CPU reads the control program (software) stored in a recording medium such as a ROM, HDD, or optical disk, expands it on the RAM, and executes the expanded control program for control. The program and the hardware work together to realize the function of the controller 5.

In the present embodiment, the controller 5 is described as a computer configured by a combination of software and hardware, but the present invention is not limited to this, and for example, as an example of the configuration of another computer, the wheel loader 1 side. An integrated circuit that realizes the function of the controller to be executed may be used.

The controller 5 includes a data acquisition unit 50, a pump command signal output unit 51, a disconnection detection unit 52, a motor command signal output unit 53, a time measurement unit 54, an elapsed time determination unit 55, and a storage unit 56. including.

The data acquisition unit 50 acquires data on the amount of depression of the accelerator pedal 121, the forward / backward changeover signal output from the forward / backward changeover switch 122, and the magnitude of the pump command signal output from the pump command signal output unit 51, respectively. ..

The pump command signal output unit 51 sends a forward pump command signal to the forward pump tilt control valve 312 in reverse based on the depression amount of the accelerator pedal 121 and the forward / backward switching signal acquired by the data acquisition unit 50. A reverse pump command signal is output to the side pump tilt control valve 313.

The disconnection detection unit 52 detects the disconnection of the forward side signal line 41 and the disconnection of the reverse side signal line 42 based on the magnitude of the pump command signal acquired by the data acquisition unit 50. That is, the disconnection detection unit 52 pumps from the controller 5 to the pump tilt control device 310 based on the magnitude of the pump command signal transmitted from the controller 5 (pump command signal output unit 51) to the pump tilt control device 310. It detects whether or not the command signal is output and determines the abnormal state of the pump command signal.

More specifically, a constant command current is applied to the forward signal line 41 and the reverse signal line 42, respectively, even when the accelerator pedal 121 and the forward / backward changeover switch 122 are not operated. If the wire is broken, the command current is cut off and becomes 0 (zero). Therefore, the disconnection detection unit 52 can detect the disconnection based on the command current applied to each of the forward signal line 41 and the reverse signal line 42 becoming zero.

The motor command signal output unit 53 detects that the forward signal line 41 or the reverse signal line 42 is disconnected in the disconnection detection unit 52, that is, when an abnormal state of the pump command signal is determined, the traveling hydraulic motor 32 A first motor command signal that reduces the tilt angle θ to the first target angle θ1 is output to the motor tilt control valve 322. This "first target angle θ1" is an angle smaller than the tilt angle of the traveling hydraulic motor 32 when the forward side signal line 41 or the reverse side signal line 42 is disconnected, and is, for example, the maximum tilt of the traveling hydraulic motor 32. It is set to an angle of 1/2 of the turning angle, an angle of 1/2 of the tilting angle at the time of disconnection, a minimum tilting angle of the traveling hydraulic motor 32, and the like.

The "tilt angle of the traveling hydraulic motor 32 when the forward signal line 41 or the reverse signal line 42 is disconnected" is the controller immediately before the disconnection of the forward signal line 41 or the reverse signal line 42 is detected. This corresponds to the tilt angle of the traveling hydraulic motor 32 when the pump command signal is normally output from 5 to the pump tilt control device 310. Therefore, when the motor command signal output unit 53 detects that the forward signal line 41 or the reverse signal line 42 is disconnected (determines an abnormal state of the pump command signal) in the disconnection detection unit 52, the traveling hydraulic motor The pump command signal from the controller 5 immediately before the disconnection of the forward side signal line 41 or the reverse side signal line 42 is detected (the abnormal state of the pump command signal is determined) to the pump tilt control device 310 at the tilt angle θ of 32. Is smaller than the tilt angle of the traveling hydraulic motor 32 when is normally output.

Further, the motor command signal output unit 53 transmits a second motor command signal that increases the tilt angle θ of the traveling hydraulic motor 32 that has been slightly tilted to the first target angle θ1 to the second target angle θ2 (> θ1). Output to the tilt control valve 322. The "second target angle θ2" may be an angle larger than the first target angle θ1, and is set to, for example, the maximum tilt angle of the traveling hydraulic motor 32.

The time measuring unit 54 measures the elapsed time t after the first motor command signal is output to the motor tilt control valve 322 in the motor command signal output unit 53.

The elapsed time determination unit 55 determines whether or not the elapsed time t measured by the time measurement unit 54 is equal to or longer than the predetermined set time T1 (hereinafter, simply referred to as “set time T1”). This "set time T1" is for traveling after the forward side signal line 41 or the reverse side signal line 42 is disconnected (that is, after the pump command signal is no longer output from the controller 5 to the pump tilt control device 310). This is a preset time as the time until the discharge flow rate of the hydraulic pump 31 becomes zero. The set time T1 is stored in the storage unit 56, which is a memory.

The motor command signal output unit 53 sends a second motor command signal to the motor tilt control valve 322 when the elapsed time t becomes the set time T1 or more (t ≧ T1) in the elapsed time determination unit 55. Output. Further, in the present embodiment, the second motor command signal increases the tilt angle θ of the traveling hydraulic motor 32 from the first target angle θ1 to the second target angle θ2 over a predetermined time T2. This "predetermined time T2" is a time longer than the time required to reduce the tilt angle θ of the traveling hydraulic motor 32 to the first target angle θ1 based on the first motor command signal.

(Processing in controller 5)
Next, a specific flow of processing executed in the controller 5 will be described with reference to FIG.

FIG. 4 is a flowchart showing the flow of processing executed by the controller 5 according to the first embodiment.

First, the data acquisition unit 50 acquires the pump command signal output from the pump command signal output unit 51 (step S501). Subsequently, the disconnection detection unit 52 determines whether or not the forward signal line 41 or the reverse signal line 42 is disconnected based on the pump command signal acquired in step S501 (step S502).

When it is determined in step S502 that the forward side signal line 41 or the reverse side signal line 42 is broken, that is, when the disconnection detection unit 52 detects the disconnection of the forward side signal line 41 or the reverse side signal line 42 (step S502 / YES), the motor command signal output unit 53 outputs a first motor command signal that causes the motor tilt angle θ to be slightly tilted to the first target angle θ1 (step S503).

As a result, the wheel loader 1 can suppress the braking force generated by the pump tilting cylinder 311 being in the neutral state at the time of disconnection, and can obtain the braking force according to the first target angle θ1. Therefore, it becomes difficult to decelerate suddenly. Therefore, even if the forward signal line 41 or the reverse signal line 42 is disconnected, the wheel loader 1 avoids sudden deceleration of the vehicle body by the controller 5 and is in a stable state without losing the balance. It will be possible to stop.

In the present embodiment, when the disconnection detection unit 52 detects the disconnection of the forward signal line 41 or the reverse signal line 42, the first motor command signal instantly sets the motor tilt angle θ to the first target angle θ1. Although it is set to be slightly tilted, the present invention is not limited to this, and the motor tilt angle θ may be slightly tilted to the first target angle θ1 over a period of time such that sudden deceleration of the vehicle body does not occur.

When it was not determined in step S502 that the forward side signal line 41 or the reverse side signal line 42 was broken, that is, the disconnection detection unit 52 did not detect the disconnection of the forward side signal line 41 or the reverse side signal line 42. In the case (step S502 / NO), the process returns to step S501, and the process does not proceed to step S503 until the disconnection detection unit 52 detects the disconnection of the forward signal line 41 or the reverse signal line 42 (step S502 / YES).

When the motor command signal output unit 53 outputs the first motor command signal in step S503, the time measurement unit 54 starts measuring the elapsed time t (step S504). Subsequently, the elapsed time determination unit 55 determines whether or not the elapsed time t during measurement is equal to or greater than the set time T1 stored in the storage unit 56 (step S505).

When it is determined in step S505 that the elapsed time t is equal to or greater than the set time T1 (t ≧ T1) (step S505 / YES), the motor command signal output unit 53 sets the motor tilt angle θ over a predetermined time T2. 2 A second motor command signal for large tilting up to the target angle θ2 is output to the motor tilt control valve 322 (step S506), and the process in the controller 5 ends.

If it is determined in step S505 that the elapsed time t has not passed the set time T1 (t <T1) (step S505 / NO), the elapsed time t has passed the set time T1 (step S505). / YES) Do not proceed to step S506.

When the tilt angle θ of the traveling hydraulic motor 32 is slightly tilted in step S503, depending on the value of the first target angle θ1, there is a possibility that the vehicle body may escape before the vehicle stops, or the wheel loader 1 may be on a slope. In that case, the braking force may be insufficient and the vehicle may not be able to stop. Therefore, in the present embodiment, after the set time T1 elapses after the motor command signal output unit 53 outputs the first motor command signal, the motor command signal output unit 53 outputs the second command signal to drive hydraulic pressure. The braking force is increased by making the tilt angle of the motor 32 larger than the tilt angle corresponding to the first motor command signal. As a result, the wheel loader 1 can be reliably stopped.

Further, in the present embodiment, the second motor command signal does not instantly cause the motor tilt angle θ to be greatly tilted to the second target angle θ2, but is to be greatly tilted to the second target angle θ2 over a predetermined time T2. Since the motor tilt angle θ smoothly shifts to a large tilt without leading to sudden deceleration of the vehicle body, the set time T1 can be shortened. For example, the wheel loader 1 is descending a slope. However, the car body does not run away and it becomes easier to stop.

<Second Embodiment>
Next, the controller 5A according to the second embodiment of the present invention will be described with reference to FIGS. 5 and 6. In FIGS. 5 and 6, the same components as those described for the wheel loader 1 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Hereinafter, the same applies to the third to sixth embodiments.

FIG. 5 is a functional block diagram showing the functions of the controller 5A according to the second embodiment. FIG. 6 is a flowchart showing a flow of processing executed by the controller 5A according to the second embodiment.

Unlike the controller 5 according to the first embodiment, the controller 5A according to the present embodiment has the motor tilt angle θ of the traveling hydraulic motor 32 slightly tilted to the first target angle θ1, and then the vehicle speed of the wheel loader 1. On condition of V, the motor tilt angle θ is largely tilted to the second target angle θ2.

As shown in FIG. 5, the controller 5A includes a vehicle speed determination unit 57 in addition to the data acquisition unit 50A, the pump command signal output unit 51, the disconnection detection unit 52, the motor command signal output unit 53, and the storage unit 56A. That is, the controller 5A includes a vehicle speed determination unit 57 instead of the time measurement unit 54 and the elapsed time determination unit 55 in the first embodiment.

As shown in FIG. 6, after the motor command signal output unit 53 outputs the first motor command signal in step S503, the data acquisition unit 50A acquires the vehicle speed V detected by the vehicle speed sensor 44 (step S504A).

Subsequently, the vehicle speed determination unit 57 determines whether or not the vehicle speed V acquired in step S504A is equal to or less than a predetermined vehicle speed threshold value Vth (hereinafter, simply referred to as “vehicle speed threshold value Vth”) (step S505A). Here, the "vehicle speed threshold value Vth" is the vehicle speed at the time when the forward side signal line 41 or the reverse side signal line 42 is disconnected (that is, when the pump command signal is no longer output from the controller 5A to the pump tilt control device 310). Is also a small value and is stored in the storage unit 56A.

When it is determined in step S505A that the vehicle speed V is equal to or less than the vehicle speed threshold value Vth (V ≦ Vth) (step S505A / YES), the process proceeds to step S506 and the motor command signal output unit 53 outputs the second motor command signal. do. On the other hand, when it is determined in step S505A that the vehicle speed V is larger than the vehicle speed threshold value Vth (V> Vth) (step S505A / NO), the process returns to step S504A and the vehicle speed V becomes equal to or less than the vehicle speed threshold value Vth (V ≦). Do not proceed to step S506 until Vth).

Also in this embodiment, the same actions and effects as those in the first embodiment are exhibited.

<Third Embodiment>
Next, the controller 5B according to the third embodiment of the present invention will be described with reference to FIGS. 7 and 8.

FIG. 7 is a functional block diagram showing the functions of the controller 5B according to the third embodiment. FIG. 8 is a flowchart showing a flow of processing executed by the controller 5B according to the third embodiment.

Unlike the controller 5 according to the first embodiment, the controller 5B according to the present embodiment has the forward side signal line 41 or the reverse side signal line 42 disconnected, and the bucket 23 is in a horizontal position at the time of disconnection. When the position is above the position of, the motor tilt angle θ is slightly tilted to the first target angle θ1.

As shown in FIG. 7, the controller 5B includes a data acquisition unit 50B, a pump command signal output unit 51, a disconnection detection unit 52, a motor command signal output unit 53, a time measurement unit 54, an elapsed time determination unit 55, and a storage unit 56B. In addition, the posture determination unit 58 is included.

As shown in FIG. 8, when the disconnection detection unit 52 detects the disconnection of the forward side signal line 41 or the reverse side signal line 42 in step S502 (step S502 / YES), the data acquisition unit 50B is attached to the cargo handling work device 2. The cargo handling work device 2 detected by the attitude sensor 45 (for example, an angle sensor that detects the angles of the lift arm 21 and the bucket 23, a pressure sensor that detects the bottom pressure of the lift arm cylinder 22 and the bucket cylinder 24, and the like). Acquire the posture (step S507).

Subsequently, the posture determination unit 58 determines whether or not the position of the bucket 23 is higher than the position of the bucket 23 in the horizontal posture of the cargo handling work device 2 based on the posture of the cargo handling work device 2 acquired in step S507. Is determined (step S508). The position of the bucket 23 in the horizontal posture of the cargo handling work device 2 is stored in advance in the storage unit 56B. The "horizontal posture of the cargo handling work device 2" is the posture of the cargo handling work device 2 when the wheel loader 1 is in the traveling posture, such as when carrying a load or traveling without a load.

When it is determined in step S508 that the position of the bucket 23 is higher than the position of the bucket 23 in the horizontal posture of the cargo handling work device 2 (step S508 / YES), the motor command signal output unit 53 proceeds to step S503. 1 Outputs a motor command signal. On the other hand, when it is determined in step S508 that the position of the bucket 23 is equal to or less than the position of the bucket 23 in the horizontal posture of the cargo handling work device 2 (step S508 / NO), the process in the controller 5B ends.

For example, in the loading work of loading excavated earth and sand, minerals, etc. into a loading destination such as a dump truck, the wheel loader 1 raises the lift arm 21 and attaches to the loading destination. If the forward signal line 41 is disconnected and the vehicle body suddenly decelerates in this state, the rear wheels 11B tend to float and the vehicle body tends to lose its balance. Therefore, the motor tilt angle control process may be applied only when the balance of the vehicle body is unstable in this way.

<Fourth Embodiment>
Next, the controller 5C according to the fourth embodiment will be described with reference to FIGS. 9 and 10.

FIG. 9 is a functional block diagram showing the functions of the controller 5C according to the fourth embodiment. FIG. 10 is a flowchart showing a flow of processing executed by the controller 5C according to the fourth embodiment.

Unlike the controller 5 according to the first embodiment, the controller 5C according to the present embodiment has a case where the forward signal line 41 or the reverse signal line 42 is disconnected and the speed stage of the vehicle body at the time of disconnection is a low speed stage. In addition, the motor tilt angle θ is slightly tilted to the first target angle θ1.

As shown in FIG. 9, the controller 5C includes a data acquisition unit 50C, a pump command signal output unit 51, a disconnection detection unit 52, a motor command signal output unit 53, a time measurement unit 54, an elapsed time determination unit 55, and a storage unit 56. In addition, the speed stage determination unit 59 is included. That is, the controller 5C includes a speed stage determination unit 59 instead of the attitude determination unit 58 in the third embodiment.

As shown in FIG. 10, when the disconnection detection unit 52 detects the disconnection of the forward signal line 41 or the reverse signal line 42 in step S502 (step S502 / YES), the data acquisition unit 50C is selected by the speed stage switch 123. Acquire the speed stage (step S507C).

Subsequently, the speed stage determination unit 59 determines whether or not the speed stage acquired in step S507C is a low speed stage (step S508C). In step S508C, when it is determined that the speed stage acquired in step S507C is a low speed stage (step S508C / YES), the process proceeds to step S503 and the motor command signal output unit 53 outputs the first motor command signal. .. On the other hand, when it is determined in step S508C that the speed stage acquired in step S507C is not a low speed stage (step S508C / NO), the processing in the controller 5C ends.

In the wheel loader 1, the vehicle speed is lower and the motor tilt angle θ is more likely to be greatly tilted when the speed stage of the vehicle body is a low speed stage (1st speed stage or 2nd speed stage). When the reverse signal line 42 is disconnected, a large braking force is likely to be generated. On the other hand, when the speed stage of the vehicle body is medium to high speed stage (3 speed stage or 4 speed stage), the vehicle speed tends to be high, and the motor tilt angle θ is often used for small tilt. Since the traction force tends to be small even if the motor tilt angle θ is the same due to the difference in the gear ratio of the transmission 15, the braking force is less likely to be generated as compared with the case of the low speed stage. Therefore, only when the speed stage of the vehicle body is the low speed stage as described above, the motor tilt angle control process may be applied.

<Fifth Embodiment>
Next, the controller 5 according to the fifth embodiment of the present invention will be described with reference to FIG.

FIG. 11 is a flowchart showing a flow of processing executed by the controller 5 according to the fifth embodiment.

Similar to the first embodiment, the controller 5 according to the present embodiment has a data acquisition unit 50, a pump command signal output unit 51, a disconnection detection unit 52, a motor command signal output unit 53, a time measurement unit 54, and an elapsed time determination unit. 55, and a storage unit 56 are included.

As shown in FIG. 11, when the disconnection detection unit 52 detects the disconnection of the forward signal line 41 or the reverse signal line 42 in step S502 (step S502 / YES), the disconnection detection unit 52 further increases the data acquisition unit 50. Based on the forward / backward switching signal acquired in the above, it is determined whether or not the forward signal line 41 is disconnected while the vehicle body is moving forward or the reverse signal line 42 is disconnected while the vehicle body is moving backward (step S509).

If it is determined in step S509 that the forward signal line 41 is broken while the vehicle body is moving forward or the reverse signal line 42 is broken while the vehicle body is moving backward (step S509 / YES), the process proceeds to step S503 to output the motor command signal. The unit 53 outputs the first motor command signal. On the other hand, if it is not determined in step S509 that the forward signal line 41 is disconnected during the vehicle body advancement or the reverse signal line 42 is not disconnected during the vehicle vehicle reverse movement, that is, the reverse signal line 42 is disconnected while the vehicle body is moving forward. If the forward signal line 41 is disconnected (step S509 / NO) during disconnection or reverse movement of the vehicle body, the process in the controller 5 ends.

If the reverse signal line 42 is disconnected while the vehicle body is moving forward, or if the forward signal line 41 is disconnected while the vehicle body is moving backward, the pump command signal output from the pump command signal output unit 51 is not affected. Therefore, the motor tilt angle control process may be performed only when the forward signal line 41 is disconnected during the forward movement of the vehicle body or the reverse signal line 42 is disconnected during the reverse movement of the vehicle body.

<Sixth Embodiment>
Next, the wheel loader 1 according to the sixth embodiment of the present invention will be described with reference to FIG.

FIG. 12 is a diagram showing a configuration example of the drive system of the wheel loader 1 according to the sixth embodiment.

In the pump tilt control device 310A according to the present embodiment, unlike the configuration of the pump tilt control device 310 according to the first embodiment, the flow (flow rate and direction) of the hydraulic oil supplied to the pump tilt cylinder 311 is different. It is controlled by one directional control valve 314.

Specifically, the directional control valve 314 has a first switching position L having a pump tilt angle based on a forward pump command signal output from the controller 5 and transmitted via the forward signal line 41, and a controller. The second switching position R that controls the pump tilt angle based on the reverse pump command signal output from 5 and transmitted via the reverse signal line 42, and the hydraulic oil of the pump tilt cylinder 311 are used in the hydraulic oil tank. It has a neutral position N, which returns to 34.

When the forward pump command signal is output from the controller 5, the directional control valve 314 is switched to the first switching position L, whereby the pump tilt cylinder 311 controls the pump tilt angle on the forward side. On the other hand, when the reverse pump command signal is output from the controller 5, the directional control valve 314 is switched to the second switching position R, whereby the pump tilt cylinder 311 controls the pump tilt angle on the reverse side.

When the forward signal line 41 or the reverse signal line 42 is disconnected, the directional control valve 314 returns to the neutral position N (state shown in FIG. 12), and the hydraulic oil in the pump tilting cylinder 311 is the hydraulic oil. It is discharged to the tank 34, and the discharge flow rate of the traveling hydraulic pump 31 becomes zero.

As described above, the pump tilt cylinder 311 does not necessarily have to be controlled by two pump tilt control valves (forward side pump tilt control valve 312 and reverse side pump tilt control valve 313), and one direction control. It may be controlled by valve 314.

The embodiments and modifications of the present invention have been described above. The present invention is not limited to the above-described embodiments and modifications, and includes various other modifications. For example, the above-described embodiments and modifications have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of the present embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of the present embodiment. Furthermore, it is possible to add / delete / replace a part of the configuration of the present embodiment with another configuration.

For example, in the above embodiment, the wheel loader has been described as one aspect of the work vehicle, but the present invention is not limited to this, and the present invention can be applied to other work vehicles equipped with an HST type traveling drive system. be.

Further, in the above embodiment, in the

controllers

5, 5A, 5B, 5C, when the disconnection detection units 52, 52A detect the disconnection of the forward side signal line 41 or the reverse side signal line 42, the motor command signal output unit 53 first. A motor command signal is output, and then a second motor command signal is output. However, when at least the disconnection detection units 52 and 52A detect a disconnection of the forward signal line 41 or the reverse signal line 42, the motor command signal is output. The output unit 53 may output the first motor command signal.

1: Wheel loader (work vehicle)
2: Cargo handling work equipment (work equipment)
5,5A, 5B, 5C: Controller 11A: Front wheels (wheels)
11B: Rear wheel (wheel)
23: Bucket (working tool)
30: Engine 31: Driving hydraulic pump 32: Driving hydraulic motor 44: Vehicle speed sensor 45: Attitude sensor 122: Forward / backward changeover switch (forward / backward changeover device)
123: Speed stage switch (speed stage selection device)
310, 310A: Pump tilt control device 320: Motor tilt control device

Claims

A car body with multiple wheels and
The engine mounted on the car body and
A variable displacement hydraulic pump driven by the engine and
A variable displacement type traveling hydraulic motor that is connected to the traveling hydraulic pump in a closed circuit and transmits the driving force of the engine to the plurality of wheels.
A controller that controls the traveling hydraulic pump and the traveling hydraulic motor,
A pump tilt control device that controls the push-out volume of the traveling hydraulic pump based on a pump command signal output from the controller and transmitted via a signal line.
A motor tilt control device that controls the push-out volume of the traveling hydraulic motor based on a motor command signal output from the controller, and a motor tilt control device.
In a work vehicle equipped with
The controller
When the abnormal state of the pump command signal is determined based on the pump command signal transmitted from the controller to the pump tilt control device, the controller immediately before determining the abnormal state sends the pump tilt control device to the pump tilt control device. A work vehicle characterized in that the push-out volume of the running hydraulic motor is controlled so as to be smaller than the push-out volume of the running hydraulic motor when a pump command signal is normally output.
In the work vehicle according to claim 1,
The controller
The pump command signal is not output for the elapsed time after detecting that the pump command signal is not output from the controller to the pump tilt control device and reducing the push-out volume of the traveling hydraulic motor. When the set time or more set as the time until the discharge flow rate of the traveling hydraulic pump becomes 0 or more, the pushing volume of the traveling hydraulic motor is reduced to reduce the pushing volume of the traveling hydraulic motor. A work vehicle characterized by being larger than.
In the work vehicle according to claim 2.
The controller
It takes a predetermined time longer than the time required to reduce the push-out volume of the traveling hydraulic motor by detecting that the pump command signal is not output from the controller to the pump tilt control device. A work vehicle characterized in that the push-out volume of the traveling hydraulic motor is made larger than the pushing-out volume of the traveling hydraulic motor that has been reduced.
In the work vehicle according to claim 1,
Equipped with a vehicle speed sensor that detects vehicle speed
The controller
When the vehicle speed detected by the vehicle speed sensor becomes a predetermined vehicle speed set to be smaller than the vehicle speed when the pump command signal is no longer output from the controller to the pump tilt control device, the traveling A work vehicle characterized in that the push-out volume of the hydraulic motor for driving is made larger than the push-out volume of the reduced running hydraulic motor.
In the work vehicle according to claim 1,
A work device with a work tool attached to the tip,
A posture sensor for detecting the posture of the work device is provided.
The controller
When the position of the work tool in the posture of the work device detected by the posture sensor is higher than the position of the work tool in the horizontal posture of the work device, the push-out volume of the traveling hydraulic motor is determined. A work vehicle characterized in that it is smaller than the push-out volume of the traveling hydraulic motor when the pump command signal is output from the controller to the pump tilt control device.
In the work vehicle according to claim 1,
A speed stage selection device for selecting the speed stage of the vehicle body is provided.
The controller
When a low speed stage including the lowest speed stage is selected in the speed stage selection device, the pump command signal is output from the controller to the pump tilt control device for the push-out volume of the traveling hydraulic motor. A work vehicle characterized in that it is made smaller than the push-out volume of the traveling hydraulic motor in the case of
In the work vehicle according to claim 1,
A forward / backward switching device for switching the forward / backward movement of the vehicle body is provided.
The controller
When the forward / backward switching device is switched to forward, the pump command signal related to forward is not output from the controller to the pump tilt control device, or the forward / backward switching device is switched to reverse. When the controller does not output the pump command signal related to reverse movement to the pump tilt control device, the push-out volume of the traveling hydraulic motor is transferred from the controller to the pump tilt control device. A work vehicle characterized in that it is smaller than the push-out volume of the traveling hydraulic motor when a command signal is output.