JP2021102392A - Work vehicle - Google Patents

Abstract

To provide a work vehicle configured so that a wheel can be braked properly over a long time when a vehicle is stopped.SOLUTION: A work vehicle A comprises a brake control mechanism BL that makes a brake act by controlling expansions and contractions of a hydraulic brake cylinder BS. In the brake control mechanism BL, pilot check valves PC1 and PC2 which act as check vales when stopping an engine and receive pilot pressure to communicate with each other when activating an engine EN are provided in oil passages L7 and L8 connected to the hydraulic brake cylinder BS. When stopping the engine EN, the pilot check valves PC1 and PC2 close the oil passages L7 and L8 connected to the hydraulic brake cylinder BS.SELECTED DRAWING: Figure 1

Description

The present invention relates to a work vehicle for performing agricultural work.

Conventionally, in a work vehicle such as a tractor equipped with a work machine for agricultural work, a brake mechanism for operating a brake by operating a brake pedal to brake the wheels is provided, and this brake mechanism is a hydraulic brake whose stroke amount can be controlled. There is known a work vehicle in which the brake can be operated independently of the operation of the brake pedal by the cylinder (see, for example, Patent Document 1).

Further, in recent years, the use of a work vehicle called a so-called robot tractor that autonomously travels in a field using a positioning satellite has been increasing, and in this autonomously travelable work vehicle, the hydraulic pressure of the brake mechanism is increased during autonomous travel. It is configured to automatically brake the wheels by controlling the stroke amount of the brake cylinder (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2018-172027 Japanese Unexamined Patent Publication No. 2018-191620

However, according to the work vehicle described in Patent Document 1 and Patent Document 2, when the brake is operated by the stroke of the hydraulic brake cylinder and the vehicle is stopped, the internal leak of the brake oil generated over time causes the wheel to reach the wheel. The braking force of the vehicle could not be maintained for a long time, and as a result, the work vehicle may unintentionally move from the stopped position.

In particular, in a work vehicle configured to be able to run autonomously, when the engine is automatically stopped in an unmanned state, it is possible to maintain a sufficient braking force on the wheels for a long period of time in order to maintain the stopped position. This issue is even more important, which is also desirable from a safety standpoint.

Therefore, an object of the present invention is to solve such a problem and to provide a work vehicle capable of satisfactorily braking wheels for a long time when the vehicle is stopped.

In order to achieve the above object, the invention according to claim 1 is
A brake control mechanism for operating the brake by controlling the amount of expansion and contraction of the hydraulic brake cylinder is provided, and the brake control mechanism acts as a check valve in the oil passage connected to the hydraulic brake cylinder when the engine is stopped, and when the engine is driven. A pilot check valve is provided to obtain pilot pressure and communicate.
Provided is a work vehicle characterized in that an oil passage connected to the hydraulic brake cylinder by the pilot check valve is closed when the engine is stopped.

The invention of claim 2 is the work vehicle according to claim 1.
The brake control mechanism includes an accumulator that accumulates pressure when the engine is driven, and a pilot-type directional control valve that shuts off when the engine is driven and communicates when the engine is stopped.
When the engine is stopped, the accumulator is configured to supply pressure oil to the hydraulic brake cylinder via the pilot type directional control valve in the closed circuit.

The invention according to claim 3 is the work vehicle according to claim 2.
The hydraulic brake cylinder is composed of a left brake cylinder that operates the left brake and a right brake cylinder that operates the right brake.
The accumulator is connected to the inlet side of the pilot type directional control valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side, respectively.

According to the invention of claim 1, when the engine is stopped, the oil passage connected to the hydraulic brake cylinder by the pilot check valve is closed, so that the length is long even when the engine is stopped when the vehicle is stopped. The wheels can be braked well over time.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, when the engine is stopped, the accumulator presses the hydraulic brake cylinder in a closed circuit via a pilot type direction switching valve. Therefore, the wheels can be braked satisfactorily for a longer period of time.

According to the invention of claim 3, in addition to the effect of the invention of claim 2, the accumulator is connected to the inlet side of the pilot type direction switching valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side. By connecting each of them, one accumulator can supply the pressure oil to the two brake cylinder BSs, so that the pressure oil can be efficiently supplied and the manufacturing cost can be reduced.

FIG. 1 is a left side view of a work vehicle according to an embodiment of the present invention. FIG. 2 is an explanatory view of an operation unit of the work vehicle of FIG. FIG. 3 is a block diagram showing a configuration of a control device for the work vehicle of FIG. 4 (A) is a schematic plan view of the braking device of the work vehicle of FIG. 1, and FIG. 4 (B) is a schematic right side view of the braking device of the work vehicle of FIG. FIG. 5 is a circuit diagram showing a hydraulic circuit of the brake control mechanism BL.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, unless otherwise specified, the forward direction of the work vehicle A is the front, the opposite direction is the rear, and the right side is the right side and the left side is the left side when facing forward.

<1. Work vehicle configuration>
FIG. 1 is a left side view of the work vehicle A according to the embodiment of the present invention.
The work vehicle A has a so-called robot tractor configuration in which a work machine WM for performing agricultural work is mounted on the rear portion of a traveling vehicle body a1 provided with autonomous traveling means.

As shown in FIG. 1, in the traveling vehicle body a1, an engine EN and a fuel tank (not shown) serving as drive sources are arranged in the bonnet a11, and the power from the engine EN is used to shift the transmission case a12. The speed is changed by the device TR, and the speed is transmitted to the front wheels a13 and the rear wheels a14, respectively, to travel.

A cabin a15 on which an operator can board is arranged at the rear of the bonnet a11.
The cabin a15 is provided with a driver's seat a16 at the rear of the room, and an inclination sensor s1 for detecting the inclination of the vehicle body of the work vehicle A is arranged at the bottom of the cabin a15.

FIG. 2 is an explanatory view of an operation unit of the work vehicle of FIG.
As shown in FIG. 2, on the dashboard in front of the driver's seat a16, operating members such as the steering handle a17, the main key a18, the forward / backward lever a19, the speed change lever a20, and the vehicle speed and the remaining amount of fuel are displayed. An operation panel SP including a meter panel MP, a rotation speed increase / decrease switch for increasing / decreasing the set value of the engine EN rotation speed, a brake adjustment dial for adjusting the brake pressure, and the like are provided. Further, three operation pedals, a clutch pedal p1, a left brake pedal p2, and a right brake pedal p3, are arranged below the steering handle a17.

When the steering handle a17 is rotated, the front wheel a13 is rotated via a steering device (not shown) according to the direction of rotation and the amount of operation, whereby the work vehicle A is configured to rotate. Steering in the direction of travel is possible. Although not shown, the rotation base of the steering handle a17 is provided with a steering angle detecting means capable of detecting the steering angle (rotation angle) of the steering handle a17. The steering angle detecting means is composed of, for example, an angle sensor such as a rotary encoder.

Further, the rotation shaft (steering shaft) of the steering handle a17 is provided with a steering actuator AC (not shown) that controls the rotation of the steering handle a17 to enable automatic operation. As a result, the work vehicle A can control the traveling direction of the work vehicle A during autonomous traveling by determining the steering angle of the steering handle a17 and controlling the rotation of the steering handle a17 by the steering actuator. ..

Further, although not shown, a PTO clutch, a PTO transmission, and a braking device are housed in the transmission case a12, and are configured to control the transmission of power to the PTO shaft. As a result, the work vehicle A can drive and control the work machine WM.

The work machine WM is connected to the rear part of the traveling vehicle body a1, is driven by receiving power transmission from the engine EN via the PTO shaft, and performs farm work such as tilling on the field. In the present embodiment, the working machine WM is equipped with a cultivator for cultivating the field, but the present invention is not limited to this, and the traveling vehicle body a1 has various fertilizer application machines, grass mowers, sowing machines and the like. It is possible to select and install one.

A GPS device AN that calculates the current position of the work vehicle A is provided on the upper surface of the cabin a15. This GPS device AN is a device that calculates position information indicating the current position of the traveling vehicle A based on a radio wave signal from a GPS satellite received by using a positioning antenna, and the calculated position information is transferred to a communication unit CD described later. It is configured to output.

<2. Work vehicle control device>
FIG. 3 is a block diagram showing a configuration of a control device C of the work vehicle A of FIG. The control device C controls the traveling and autonomous traveling by the steering of the operator, the operation of the working machine WM related to the agricultural work during the autonomous traveling, and the like.

As shown in FIG. 2, the control device C is configured to include a plurality of ECUs (Electronic Control Units), and each ECU can read and write to a CPU that performs arithmetic processing and information necessary for arithmetic processing. Various functions are realized by operating the CPU according to various control programs stored in the memory.

Specifically, the control device C is a vehicle ECU (C1) that controls the running of the work vehicle A, an engine ECU (C2) that controls the engine EN, and a work machine that controls operations such as driving and stopping of the work machine WM. It is equipped with an ECU (C3) and a communication unit CD that connects to an external network such as the Internet or a public network to enable communication with the information terminal IA, and these are configured to be able to send and receive various information to and from each other via the communication bus BA. Further, the input information of the operation panel SP can be acquired via the communication bus BA, and various information can be output to the meter panel MP.

Based on the control command from the vehicle ECU (C1), the engine ECU (C2) operates a starter motor or the like to start the engine EN, or stops the driving engine EN, and while the engine EN is being driven, the engine ECU (C2) starts the engine EN. , The output rotation speed of the engine EN is controlled based on a control program for driving the engine or the like. An engine rotation sensor s2 that detects the rotation speed of the engine EN is connected to the input side of the engine ECU (C2).

The communication unit CD has a communication function capable of wireless communication, which makes it possible to acquire position information from a GPS device, and is connected to an external network such as the Internet or a public line network to connect with the information terminal B. Communication is possible.

The work machine ECU (C3) is connected to the work machine WM and controls operations such as driving and stopping of the work machine WM based on a control command from the vehicle ECU (C1).

The vehicle ECU (C1) sends a control command to the engine ECU (C2), the working machine ECU (C1), and the brake system, thereby controlling various running including autonomous running of the working vehicle A and agricultural work by the working machine WM. I do.

On the input side of the vehicle ECU (C1), a brake pedal switch s3 that detects the amount of depression of each of the left brake pedal p2 and the right brake pedal p3, a vehicle speed sensor s4 that detects the vehicle speed, and a brake pressure of the right brake are detected. Right brake pressure sensor s5, left brake pressure sensor s6 that detects the brake pressure of the left brake, and the tilt (pitch) of the work vehicle A in the front-rear direction, the tilt (roll) and the turn (yaw) in the left-right direction of the machine. The acceleration sensor s7 that detects the angular velocity and the tilt sensor s1 that detects the tilt angle of the work vehicle A with respect to the horizontal direction are electrically connected.

A hydraulic circuit is provided on the output side of the vehicle ECU (C1), and a brake control mechanism BL that controls the pressure oil supplied to the left and right brake cylinders BS and BS is connected.

This brake control mechanism BL includes a left and right brake switching valve b3 which is an electromagnetic direction switching valve having a left brake solenoid b1 and a right brake solenoid b2, and a proportional valve b5 having a brake boosting solenoid b4. The b1, the right brake solenoid b2, and the brake boosting solenoid b4 each operate in response to a control signal from the vehicle ECU (C1).

By operating the left brake solenoid b1 and the right brake solenoid b2, the pressure oil supplied to the left and right brake cylinders BS (left brake cylinder BS1 and right brake cylinder BS2) is controlled by the left and right brake switching valves b3, respectively, and the left and right brake cylinders BS2 are controlled. The brakes BK (left brake BK1, right brake BK2) can be operated independently. Further, by operating the brake boosting solenoid b4, the amount and pressure of the pressure oil supplied to the left and right brake cylinder BSs are controlled by the proportional valve b5.

Regarding the braking of the rear wheel a14 during autonomous traveling of the work vehicle A, the expansion and contraction of the brake cylinder BS in the braking device D, which will be described later, is controlled by the control of the left brake solenoid b1, the right brake solenoid b2 and the brake boosting solenoid b4. This is done by controlling the amount (stroke amount).

<3. Braking device>
4 (A) is a schematic plan view of the braking device D of the work vehicle of FIG. 1, and FIG. 4 (B) is a schematic right side view of the braking device D of the work vehicle A of FIG.
The braking device (brake device) D is provided with a left brake mechanism d1 and a right brake mechanism d2 on the left and right sides of the transmission case a12, respectively. Since the left and right brake mechanisms d1 and d2 have a common configuration for the left and right, the left brake mechanism d1 will be mainly described below, and the right brake mechanism d2 will not be described in detail.

The left brake mechanism d1 includes a left brake pedal p2, a vertically long link rod d11 that moves up and down in conjunction with a stepping operation of the left brake pedal p2, and a front and rear long first brake connected to the lower end of the link rod d11. It has a link d12, and the rear end of the first brake link d12 is rotatably supported on the side of the transmission case a12 about the first rotation shaft d13.

The upper end of the vertically longitudinal second brake link d14 is rotatably supported on the first rotation shaft d13 together with the first brake link d12, and the second brake link d14 is the rotation of the first brake link 46. It is configured to rotate in the same direction as the rotation direction of the first brake link d12 in conjunction with the movement. The front end of the front-rear longitudinal brake operating rod d15 is rotatably connected to the lower end of the second brake link d14.

A brake cylinder BS (BS1) that expands and contracts by flood control is connected to the rear end of the brake operating rod d15, and the upper end of the vertically longitudinal brake operating link d16 rotates at the rear end of the brake cylinder BS (BS1). It is connected freely. Further, the lower end of the brake operation link d16 is rotatably supported on the side of the mission case 23 about the second rotation shaft d17.

When the upper end of the brake actuating link 51 is pulled forward, the brake actuating link d16 rotates counterclockwise (braking direction) in FIG. 4B, and the brake actuating link d16 rotates according to the amount of rotation of the brake actuating link d16. The second rotation shaft d17 also rotates. A brake pad (not shown) built in the left brake BK1 acts according to the amount of rotation of the second rotation shaft d17 to brake the rear wheel a14. The rear wheel a14 is braked with a brake pressure proportional to the amount of rotation of the second rotation shaft d17.

In the left brake mechanism d1 configured in this way, when the left brake pedal p2 is depressed, the vertically longitudinal link rod d11 is pulled up and the front end of the first brake link d12 moves upward, and in conjunction with this, the left brake mechanism d1 is interlocked with this. The second brake link d14 rotates clockwise in FIG. 4B, and the brake operating rod d15 is pulled forward. Then, the upper end of the brake operation link d16 is also pulled forward, whereby the brake operation link d16 rotates counterclockwise in FIG. 4 (B) and the second rotation shaft d17 rotates to the braking side. , The left rear wheel a14 is braked by the left brake BK1. As for the right brake mechanism d2, when the right brake pedal p3 is depressed, the right rear wheel a14 is braked by the right brake BK2 with the same configuration.

The left and right brake pedal switches s3 and s3 are configured to detect the amount of depression of the left and right brake pedals p2 and p3 by detecting the amount of rotation of the first rotation shaft d13. Further, the left and right brake pressure sensors s5 and s6 are configured to detect the brake pressures of the left brake BK1 and the right brake BK2, respectively, by detecting the amount of rotation of the second rotation shaft d17.

Further, a hydraulic control mechanism BL supported on the left side of the transmission case a12 is connected to the left and right brake cylinders BS (BS1, BS2) via pipes d18 and d19. The amount of expansion and contraction (stroke amount) of the left and right brake cylinder BS is controlled by controlling the oil pressure of the hydraulic control mechanism BL. As a result, when the left and right brake cylinders BS (BS1, BS2) are shortened in the front-rear direction, the upper ends of the left and right brake operation links d16 and d16 are pulled forward, and the left and right brake operation links d16 and d16 are operated. It is possible to brake the left and right rear wheels a14 and a14, respectively, by rotating each of them in the braking direction.

On the other hand, when the left and right brake cylinders BS (BS1, BS2) are extended in the front-rear direction, the upper ends of the left and right brake operation links d16 and d16 are pushed backward, whereby the left and right brake operation links are operated. It is possible to release the braking of the left and right rear wheels a14 and a14 by rotating d16 and d16 in the directions opposite to the braking direction, respectively. In this way, when the work vehicle A is autonomously traveling, the left and right rear wheels a14 and a14 do not need to be operated by the expansion and contraction control of the brake cylinders BS (BS1 and BS2) without requiring the operation of the left and right brake pedals p2 and p3. Braking is possible respectively.

<4. Brake control mechanism>

FIG. 5 is a circuit diagram showing a hydraulic circuit of the brake control mechanism BL.
This brake control mechanism BL supplies hydraulic oil to the piston side chambers bs1 and bs2 of the left and right brake cylinders BS (BS1 and BS2) and from the piston side chambers bs1 and bs1 based on the control signal of the vehicle ECU (C1). It is a hydraulic control unit that controls the discharge of hydraulic oil and thereby controls the expansion and contraction of the brake cylinders BS (BS1, BS2).

The brake control mechanism BL includes a hydraulic pump P driven by the engine EN, and a hydraulic circuit Bcil that receives the discharge oil of the hydraulic pump P and controls expansion and contraction of the brake cylinders BS (BS1, BS2).

As shown in FIG. 5, the hydraulic circuit Bcil of the brake control mechanism BL has a proportional valve b5, a left / right brake switching valve b3, and an accumulator arranged in a housing (valve case) BX as main components. It includes an AQ, a pilot type directional control valve PL, a first pilot check valve PC1, and a second pilot check valve PC2. First, each component will be described below.

The housing (valve case) BX has a pump port p1 connected to the hydraulic pump P, a cylinder port p2, p3 connected to the brake cylinder BS (BS1, BS2), and a tank port p4, p5 connected to the tank T in the transmission. p6 is provided.

The hydraulic pump P is composed of a constant-capacity gear pump driven by the power of the engine EN.

The proportional valve b5 changes the opening area and controls the passing flow rate by operating the brake boosting solenoid b5.

The left and right brake switching valve b3 is a direction switching valve at 5 ports and 3 positions, and the right side communication position (g) for flowing pressure oil to the right brake cylinder BS2 and the brake by the operation of the left brake solenoid b1 and the right brake solenoid b2. It is possible to switch between the return position (h) for returning the hydraulic oil of the cylinder BS to the tank T and the left communication position (i) for flowing the pressure oil to the left brake cylinder BS1.

The accumulator AQ is a pressure accumulator that includes a cylinder (not shown), a piston that can slide in the cylinder, and a compression coil spring so that pressure can be accumulated.

The pilot type directional control valve PL is a directional control valve with 3 ports and 2 positions, and is operated by pilot pressure to communicate a communication position (a) between the inlet side and the outlet side and a shutoff position (b) that shuts off the communication position (a). And can be switched.

The first pilot check valve PC1 is operated by pilot pressure and has a communication position (c) that communicates between the inlet side and the outlet side and a check position (d) that prevents the pressure oil from flowing out from the outlet side to the inlet side. Can be switched.

Like the first pilot check valve PC1, the second pilot check valve PC2 has a communication position (e) that communicates between the inlet side and the outlet side and a check position (e) that prevents pressure oil from flowing out from the outlet side to the inlet side (a check valve PC2). It is possible to switch between f) and.

Next, the hydraulic circuit Bcil having the above components will be described below. First, among the hydraulic circuits Bcil, the circuits related to the expansion and contraction of the left and right brake cylinders BS (BS1, BS2) will be described in detail.

The hydraulic pump P is connected to the pressure reducing valve GN by the first oil passage L1, and the discharge oil of the hydraulic pump P controlled to a constant pressure by the pressure reducing valve GN is supplied to the second oil passage L2 via the pump port p1. To.

In the third oil passage L3 branching from the second oil passage L2, a proportional valve b5 is connected to the tip of the line filter FL for filtering oil, and the proportional valve b5 supplies the right and left brake cylinders BS (BS1 and BS2). The amount and pressure of pressure oil is controlled. A return oil passage T1 for returning unnecessary hydraulic oil to the tank T is connected to the proportional valve b5.

A left and right brake switching valve b3 is connected to the downstream of the proportional valve b5 by a fourth oil passage L4, and the left and right brake switching valve b3 controls the flow of pressure oil as hydraulic oil, and either the left or right brake. Whether it is supplied to the cylinder BS (BS1, BS2) is determined. As a result, pressure oil is supplied from the left and right brake switching valves b3 to the piston side chambers bs1 and bs2 of the left and right brake cylinders BS (BS1, BS2), and the amount of expansion and contraction (stroke amount) of the left and right brake cylinders BS (BS1, BS2) is increased. Each is controllable. The left and right brake switching valves b3 are connected to return oil passages T2 and T3 for returning unnecessary hydraulic oil to the tank T.

Next, among the hydraulic circuits Bcil, the circuit related to the maintenance of braking of the rear wheel a14 will be described in detail. The second oil passage L2 is connected to the ninth oil passage L9 via the check valve GS, and the downstream side of the ninth oil passage L9 is branched and connected to the accumulator AQ and the pilot type directional control valve PL, respectively. There is. Further, the ninth oil passage L9 is provided with a pilot oil passage L10 for guiding the pilot pressure to the pilot type directional control valve PL.

Further, a first pilot check valve PC1 is interposed between the fifth oil passage L5 and the seventh oil passage L7 extending from the left and right brake switching valve b3 to the left brake cylinder BS1, and a sixth extending to the left brake cylinder BS1. A second pilot check valve PC2 is interposed between the oil passage L6 and the eighth oil passage L8, and a pilot pressure is applied to the first pilot check valve PC1 and the second pilot check valve PC2 in the second oil passage L2. A guiding pilot oil passage L11 is provided.

The pilot type directional control valve PL is provided so that the inlet side communicates with the accumulator AQ and the outlet side communicates with the seventh oil passage L7 and the eighth oil passage L8 when the communication position (a) is reached. As a result, one accumulator AQ is configured to be able to supply pressure oil to the two brake cylinders BS (BS1, BS2). As a result, the pressure oil can be efficiently supplied and the manufacturing cost can be reduced.

With such a configuration, when the engine EN is driven, the pilot type direction switching valve PL is in the shutoff position (b), the first pilot check valve PC1 is in the communication position (c), and the second pilot is in the communication position (c) due to the pilot pressure in the pilot oil passage L11. The check valve PC2 is in the communication position (e). As a result, the expansion and contraction amount (stroke amount) of the left and right brake cylinders BS (BS1 and BS2) can be controlled by operating the proportional valve b5 and the left and right brake switching valve b3, while the pressure oil from the hydraulic pump P is released. , The first oil passage L1, the second oil passage L2, and the ninth oil passage L9 are stored in the accumulator AQ to accumulate pressure, and the filled state is maintained.

When the engine EN is stopped, the pilot type directional control valve PL is in the communication position (a), the first pilot check valve PC1 is in the check valve position (d), and the second pilot check valve PC2 is in the check valve position (f). As a result, a closed circuit is formed in the 9th oil passage L9, the 7th oil passage L7, and the 8th oil passage L8, and the oil pressure in the closed circuit is maintained by the oil pressure accumulated in the accumulator AQ, so that the brake cylinder BS The oil pressure in the piston side chambers bs1 and bs2 of (BS1, BS2) is also maintained. As a result, the rear wheels a14 and a14 can be braked even when the engine EN is stopped when the work vehicle A is stopped. Further, after the engine EN is started, normal braking operation becomes possible.

In this way, when the engine EN is driven, the accumulator AQ is accumulated, and when the engine EN is stopped, the pilot type direction switching valve PL is automatically set to the communication position (a), and the hydraulic pressure accumulated in the accumulator AQ is used as the brake cylinder BS. According to the configuration in which the rear wheels a14 and a14 are braked by supplying the piston side chambers bs1 and bs2 of (BS1 and BS2), the rear wheels a14 and a14 can be satisfactorily operated even when the engine EN is stopped due to engine staging, for example. Braking is possible, which can improve safety.

Further, by disposing the first pilot check valve PC1 and the second pilot check valve PC2 between the left and right brake switching valve b3 and the brake cylinder BS, the internal leakage of the brake oil of the brake cylinder BS is reduced and the length is increased. The rear wheels a14 and a14 can be satisfactorily braked over time.

In addition, by arranging the check valve GS between the accumulator AQ and the pressure reducing valve GN, it is possible to prevent the oil filled in the accumulator AQ from flowing back at the time of engine stall. Further, the differential pressure required for switching the pilot type directional control valve PL can be generated.

A Work vehicle a1 Traveling vehicle body a11 Bonnet a12 Mission case a13 Front wheel a14 Rear wheel a15 Cabin a16 Driver's seat a17 Steering handle a18 Main key a19 Forward / backward lever a20 Shift lever

b1 Left brake solenoid b2 Right brake solenoid b3 Left and right brake switching valve b4 Brake boost solenoid b5 Proportional valve

s1 Tilt sensor s2 Engine rotation sensor s3 Brake pedal switch s4 Vehicle speed sensor s5 Left brake pressure sensor s6 Left brake pressure sensor s7 Accelerometer

C1 vehicle ECU
C2 engine ECU
C3 work machine ECU

D Braking device (brake device)
d1 Left brake mechanism d2 Right brake mechanism d11 Link rod d12 1st brake link d13 1st rotation axis d14 2nd brake link d15 Brake operation rod d16 Brake operation link d17 2nd rotation axis d18 Piping d19 Piping

AQ Accumulator BS Brake Cylinder BX Housing (Valve Case)
Bcil hydraulic circuit CD communication unit EN engine MP meter panel MS electric motor PL pilot type direction switching valve PC1 1st pilot check valve PC2 2nd pilot check valve SA braking device SP operation panel WM work machine

Claims (3)

Equipped with a brake control mechanism that operates the brake by controlling the amount of expansion and contraction of the hydraulic brake cylinder.
The brake control mechanism is provided with a pilot check valve that acts as a check valve when the engine is stopped and obtains pilot pressure when the engine is driven to communicate with the oil passage connected to the hydraulic brake cylinder.
A work vehicle characterized in that an oil passage connected to the hydraulic brake cylinder by the pilot check valve is closed when the engine is stopped. The brake control mechanism includes an accumulator that accumulates pressure when the engine is driven, and a pilot-type directional control valve that shuts off when the engine is driven and communicates when the engine is stopped.
The operation according to claim 1, wherein when the engine is stopped, the accumulator is configured to supply pressure oil to the hydraulic brake cylinder via the pilot type directional control valve in the closed circuit. vehicle. The hydraulic brake cylinder is composed of a left brake cylinder that operates the left brake and a right brake cylinder that operates the right brake.
The work vehicle according to claim 2, wherein the accumulator is connected to the inlet side of the pilot type directional control valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side, respectively.

Images