JP7235206B2 - work vehicle - Google Patents

Description

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

Conventionally, a work vehicle such as a tractor equipped with a work machine for agricultural work has a brake mechanism that operates a brake by operating a brake pedal to brake a wheel. 2. Description of the Related Art A work vehicle is known in which a brake can be operated independently of operation of a brake pedal by a cylinder (see, for example, Patent Document 1).

In recent years, there has been an increase in the use of work vehicles called robot tractors that autonomously travel across agricultural fields using positioning satellites. By controlling the stroke amount of the brake cylinder, the wheels are automatically braked (see Patent Document 2, for example).

JP 2018-172027 A JP 2018-191620 A

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, internal leakage of the brake hydraulic pressure that occurs over time causes the brake fluid to leak to the wheels. The braking force cannot be sustained for a long time, and as a result, there is a risk that the work vehicle will unintentionally move from the stop position.

In particular, in a work vehicle configured to be able to run autonomously, when the engine is automatically stopped in an unmanned state, sufficient braking force to the wheels can be maintained for a long time in order to maintain the stopped position. It is also desirable from a safety point of view, and this issue is more important.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a work vehicle that solves such a problem and is capable of braking the wheels satisfactorily for a long time while the vehicle is stopped.

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

Furthermore, the invention of claim 1 , in addition to the above configuration,
The brake control mechanism includes an accumulator that accumulates pressure when the engine is running, and a pilot directional switching valve that is closed when the engine is running and communicates when the engine is stopped,
The accumulator is configured to supply pressure oil to the hydraulic brake cylinder via the pilot type directional switching valve in the closed circuit when the engine is stopped.

The invention according to claim 2 is the work vehicle according to claim 1 ,
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 switching valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side, respectively.

According to the first aspect of the invention, when the engine is stopped, the oil passage connected to the hydraulic brake cylinder by the pilot check valve is closed. Good wheel braking over time.

In addition, when the engine is stopped, the accumulator supplies pressurized oil to the hydraulic brake cylinder via the piloted directional control valve in a closed circuit, so that the wheels can be braked well for a longer period of time.

According to the invention of claim 2 , in addition to the effect of the invention of claim 1 , the accumulator is connected to the inlet side of the pilot type directional switching valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side. By connecting them to each other, one accumulator can supply pressurized oil to two brake cylinders , so the pressurized oil can be supplied efficiently and the manufacturing cost can be reduced.

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

Preferred embodiments of the present invention will be described below 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, the right is the right, and the left is the left.

<1. Configuration of Work Vehicle>
FIG. 1 is a left side view of a work vehicle A according to an embodiment of the invention.
The working vehicle A has a configuration of a so-called robot tractor in which a working machine WM for agricultural work is attached to the rear portion of a traveling vehicle body a1 having an autonomous traveling means.

As shown in FIG. 1, the traveling vehicle body a1 has an engine EN serving as a drive source and a fuel tank (not shown) disposed in a bonnet a11. The speed is changed by the device TR and transmitted to the front wheels a13 and the rear wheels a14 to run.

A cabin a15 in which a worker can get in is arranged at the rear portion of the bonnet a11.
The cabin a15 is provided with a cockpit a16 in the rear part of the room, and a tilt sensor s1 for detecting the tilt of the vehicle body of the work vehicle A is arranged at the bottom of the cabin a15.

FIG. 2 is an explanatory diagram of an operation unit of the work vehicle of FIG. 1. FIG.
On the dashboard in front of the cockpit a16, as shown in FIG. 2, operation members such as a steering handle a17, a main key a18, a forward/reverse lever a19, and a gearshift lever a20, as well as vehicle speed, remaining amount of fuel, etc., are displayed. A meter panel MP and an operation panel SP having a rotation speed increase/decrease switch for increasing or decreasing the set value of the engine EN rotation speed, a brake adjustment dial for adjusting brake pressure, and the like are provided. Three operation pedals, ie, 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 turned, the front wheels a13 are turned through a steering device (not shown) in accordance with the turning direction and amount of operation. It is possible to steer in the direction of travel. Although not shown, steering angle detection means capable of detecting the steering angle (rotational angle) of the steering handle a17 is provided at the turning base of the steering handle a17. This steering angle detection means is composed of, for example, an angle sensor such as a rotary encoder.

Further, a steering actuator AC (not shown) is provided on the rotating shaft (steering shaft) of the steering handle a17 to control the rotation of the steering handle a17 to enable automatic operation. As a result, the work vehicle A determines the steering angle of the steering handle a17 and controls the rotation of the steering handle a17 by the steering actuator, thereby enabling control of the traveling direction of the work vehicle A during autonomous travel. .

Although not shown, the transmission case a12 accommodates a PTO clutch, a PTO transmission, and a braking device, and is configured to control 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, and is driven by power transmission from the engine EN via the PTO shaft to perform agricultural work such as plowing on the field. In the present embodiment, a cultivator for cultivating a field is mounted as the work machine WM, but it is not limited to this. It is possible to select and wear items.

A GPS device AN for calculating 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 for calculating position information indicating the current position of the traveling vehicle A based on radio signals from GPS satellites received using a positioning antenna. configured to output.

<2. Control Device for Work Vehicle>
FIG. 3 is a block diagram showing the configuration of the control device C of the work vehicle A of FIG. 1. As shown in FIG. The control device C controls traveling by steering by a worker, autonomous traveling, and operation of the work machine WM related to agricultural work during autonomous traveling.

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

Specifically, the control device C includes 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 WM that controls operations such as drive and stop of the work machine WM. It has an ECU (C3) and a communication unit CD which is connected to an external network such as the Internet or a public line network to enable communication with the information terminal IA, and which are configured to be able to transmit and receive various information to and from each other via a communication bus BA. Further, input information of the operation panel SP can be acquired via the communication bus BA, and various kinds of information can be output to the meter panel MP.

Based on a 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 engine EN in operation. , and controls the output speed of the engine EN based on a control program for driving the engine. An engine rotation sensor s2 for detecting 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 communicate 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 control commands from the vehicle ECU (C1).

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

On the input side of the vehicle ECU (C1) are a brake pedal switch s3 for detecting the amount of depression of each of the left brake pedal p2 and the right brake pedal p3, a vehicle speed sensor s4 for detecting the vehicle speed, and a brake pressure for the right brake. A right brake pressure sensor s5 that detects the brake pressure of the left brake, a left brake pressure sensor s6 that detects the brake pressure of the left brake, a tilt (pitch) in the longitudinal direction of the machine body of the work vehicle A, a tilt (roll) in the horizontal direction of the machine body, and a turning (yaw). An acceleration sensor s7 that detects an angular velocity and an inclination sensor s1 that detects an inclination angle of the vehicle body of the work vehicle A with respect to the horizontal are electrically connected.

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

The brake control mechanism BL includes a left and right brake switching valve b3, which is an electromagnetic directional switching valve having a left brake solenoid b1 and a right brake solenoid b2, and a proportional valve b5 having a brake boost solenoid b4. The b1, the right brake solenoid b2, and the brake boosting solenoid b4 operate according to control signals from the vehicle ECU (C1).

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

Regarding the braking of the rear wheel a14 during autonomous travel of the work vehicle A, the expansion and contraction of the brake cylinder BS in the braking device D described later is performed by controlling 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>
4A is a schematic plan view of the braking device D of the work vehicle of FIG. 1, and FIG. 4B is a schematic right side view of the braking device 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 both left and right sides of the transmission case a12. Since the left and right brake mechanisms d1 and d2 have a common structure, the left brake mechanism d1 will be mainly described below, and a detailed description of the right brake mechanism d2 will be omitted.

The left brake mechanism d1 includes a left brake pedal p2, a vertically elongated link rod d11 that moves up and down in conjunction with the stepping operation of the left brake pedal p2, and a longitudinally elongated first brake connected to the lower end of the link rod d11. 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 a vertically long second brake link d14 is rotatably supported on the first rotation shaft d13 together with the first brake link d12. The first brake link d12 rotates in the same direction as the first brake link d12. A front end of a 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 hydraulic pressure is connected to the rear end of the brake operating rod d15, and the upper end of a vertically long brake operating link d16 rotates to the rear end of the brake cylinder BS (BS1). movably connected. Also, the lower end of the brake actuation link d16 is supported laterally of the transmission case 23 so as to be rotatable about the second rotation shaft d17.

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

In the left brake mechanism d1 configured in this manner, when the left brake pedal p2 is stepped on, the vertically long link rod d11 is pulled up and the front end of the first brake link d12 moves upward. The second brake link d14 rotates clockwise in FIG. 4(B), and the brake operating rod d15 is pulled forward. Then, the upper end of the brake actuation link d16 is also pulled forward, thereby rotating the brake actuation link d16 counterclockwise in FIG. , 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 stepped on, the right rear wheel a14 is braked by the right brake BK2 in a similar manner.

The left and right brake pedal switches s3, s3 are configured to detect the amount of depression of the left and right brake pedals p2, p3 by detecting the amount of rotation of the first rotation shaft d13. 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 by detecting the amount of rotation of the second rotary shaft d17.

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, d19. By controlling the hydraulic pressure of the hydraulic control mechanism BL, the amount of expansion and contraction (stroke amount) of the left and right brake cylinders BS is controlled. As a result, when the left and right brake cylinders BS (BS1, BS2) are contracted in the longitudinal direction, the upper ends of the left and right brake actuation links d16, d16 are pulled forward, and the left and right brake actuation links d16, d16 are pulled forward. are rotated in the braking direction to respectively brake the left and right rear wheels a14, a14.

On the other hand, when the left and right brake cylinders BS (BS1, BS2) respectively extend in the longitudinal direction, the upper ends of the left and right brake actuation links d16, d16 are pushed rearward, thereby pushing the left and right brake actuation links. By rotating d16, d16 in the opposite direction to the braking direction, it is possible to release the braking of the left and right rear wheels a14, a14. In this manner, when the work vehicle A is autonomously traveling, the expansion and contraction control of the brake cylinders BS (BS1, BS2) allows the left and right rear wheels a14, a14 to move without the need to operate the left and right brake pedals p2, p3. Braking is possible.

<4. Brake control mechanism>

FIG. 5 is a circuit diagram showing a hydraulic circuit of the brake control mechanism BL.
The 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 supplies hydraulic oil from the piston side chambers bs1 and bs1 based on a control signal from the vehicle ECU (C1). It is a hydraulic control unit that controls the discharge of hydraulic oil and thereby controls the extension 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 Bcir that receives oil discharged from the hydraulic pump P and controls expansion and contraction of the brake cylinders BS (BS1, BS2).

As shown in FIG. 5, the hydraulic circuit Bcir of the brake control mechanism BL includes, as main components, a proportional valve b5, a left/right brake switching valve b3, and an accumulator, which are disposed in a housing (valve case) BX. AQ, a pilot type directional switching 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 includes a pump port p1 connected to the hydraulic pump P, cylinder ports p2 and p3 connected to the brake cylinders BS (BS1 and BS2), tank ports p4 and p5 connected to the tank T in the transmission, p6 is provided.

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

The proportional valve b5 changes its opening area by the actuation of the brake boosting solenoid b5 to control the flow rate.

The left and right brake switching valve b3 is a directional switching valve with five ports and three positions. It is possible to switch between a return position (h) in which hydraulic oil in the cylinder BS is returned to the tank T and a left communication position (i) in which pressure oil flows to the left brake cylinder BS1.

The accumulator AQ is a pressure accumulating device that includes a cylinder (not shown), a piston slidable in the cylinder, and a compression coil spring, and is capable of accumulating pressure.

The pilot type directional switching valve PL is a 3-port 2-position directional switching valve, and is operated by pilot pressure to communicate between the inlet side and the outlet side in a communication position (a) and in a blocking position (b) to block the communication. and can be switched.

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

As with the first pilot check valve PC1, the second pilot check valve PC2 has a communicating position (e) that communicates the inlet side and the outlet side, and a non-return position (e) that prevents pressure oil from flowing out from the outlet side to the inlet side. f) can be switched.

Next, the hydraulic circuit Bcir having the above components will be described below. First, of the hydraulic circuit Bcir, the circuit 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 through the pump port p1. be.

A third oil passage L3 branched from the second oil passage L2 is connected to a proportional valve b5 at the tip of a line filter FL for filtering oil. The amount and pressure of pressurized oil is controlled. A return oil passage T1 for returning unnecessary hydraulic oil to the tank T is connected to the proportional valve b5.

Downstream of the proportional valve b5, a right/left brake switching valve b3 is connected by a fourth oil passage L4. It is determined whether cylinders BS (BS1, BS2) are supplied. As a result, pressurized oil is supplied from the left and right brake switching valve b3 to the piston side chambers bs1 and bs2 of the left and right brake cylinders BS (BS1 and BS2), and the expansion and contraction amounts (stroke amounts) of the left and right brake cylinders BS (BS1 and BS2) are controlled. Each can be controlled. Return oil passages T2 and T3 for returning unnecessary working oil to the tank T are connected to the left and right brake switching valve b3.

Next, the circuit related to maintaining the braking of the rear wheel a14 in the hydraulic circuit Bcir will be described in detail. The second oil passage L2 is connected to a ninth oil passage L9 via a check valve GS, and the downstream side of the ninth oil passage L9 is branched and connected to an accumulator AQ and a pilot directional switching valve PL. there is The ninth oil passage L9 is also provided with a pilot oil passage L10 that guides the pilot pressure to the pilot type directional switching valve PL.

Further, a first pilot check valve PC1 is interposed between a fifth oil passage L5 and a seventh oil passage L7 extending from the left/right brake switching valve b3 to the left brake cylinder BS1, and a sixth oil passage L7 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 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 pilot oil passage L11 for guiding is provided.

The pilot type directional switching 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 in the communication position (a). Thus, one accumulator AQ is configured to supply pressure oil to two brake cylinders BS (BS1, BS2). As a result, the pressure oil can be supplied efficiently and the manufacturing cost can be reduced.

With this configuration, when the engine EN is driven, the pilot pressure in the pilot oil passage L11 causes the pilot type directional switching valve PL to be in the closed position (b), the first pilot check valve PC1 to be in the open position (c), and the second pilot The check valve PC2 becomes the communicating position (e). As a result, by operating the proportional valve b5 and the left and right brake switching valve b3, it is possible to control the expansion and contraction amount (stroke amount) of the left and right brake cylinders BS (BS1, BS2). , the first oil passage L1, the second oil passage L2, and the ninth oil passage L9, the pressure is accumulated in the accumulator AQ, and the charged state is maintained.

When the engine EN stops, the piloted directional control valve PL is in the communication position (a), the first pilot check valve PC1 is in the check position (d), and the second pilot check valve PC2 is in the check position (f). As a result, a closed circuit is formed by the ninth oil passage L9, the seventh oil passage L7, and the eighth oil passage L8, and the hydraulic pressure in the closed circuit is maintained by the hydraulic pressure accumulated in the accumulator AQ. The hydraulic pressures in the piston side chambers bs1, bs2 of (BS1, BS2) are also maintained. As a result, the rear wheels a14, a14 can be braked even when the engine EN is stopped when the work vehicle A is stopped. Further, after starting the engine EN, a normal braking operation becomes possible.

In this way, when the engine EN is running, pressure is accumulated in the accumulator AQ, and when the engine EN is stopped, the pilot type directional control valve PL is automatically set to the communication position (a), and the hydraulic pressure accumulated in the accumulator AQ is transferred to the brake cylinder BS. (BS1, BS2), the piston side chambers bs1, bs2 are supplied to brake the rear wheels a14, a14. It can be braked, which can improve safety.

In addition, 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, internal leakage of the brake hydraulic pressure of the brake cylinder BS is reduced, The rear wheels a14, a14 can be braked well 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 when the engine stalls. In addition, it is possible to generate the differential pressure necessary for switching the pilot type directional control valve PL.

A Working vehicle a1 Traveling vehicle body a11 Bonnet a12 Transmission case a13 Front wheel a14 Rear wheel a15 Cabin a16 Cockpit seat a17 Steering handle a18 Main key a19 Forward/reverse lever a20 Shift lever

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

s1 tilt sensor s2 engine speed sensor s3 brake pedal switch s4 vehicle speed sensor s5 left brake pressure sensor s6 left brake pressure sensor s7 acceleration sensor

C1 Vehicle ECU
C2 engine ECU
C3 Work equipment ECU

D braking device (brake device)
d1 Left brake mechanism d2 Right brake mechanism d11 Link rod d12 First brake link d13 First rotating shaft d14 Second brake link d15 Brake operating rod d16 Brake operating link d17 Second rotating shaft d18 Pipe d19 Pipe

AQ Accumulator BS Brake cylinder BX Housing (valve case)
Bcir Hydraulic circuit CD Communication unit EN Engine MP Meter panel MS Electric motor PL Pilot type directional switching valve PC1 First pilot check valve PC2 Second pilot check valve SA Braking device SP Operation panel WM Work machine

Claims (2)

Equipped with a brake control mechanism that applies 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 communicates with a pilot pressure when the engine is running, in an oil passage connected to the hydraulic brake cylinder,
The oil passage connected to the hydraulic brake cylinder is closed by the pilot check valve when the engine is stopped;
The brake control mechanism includes an accumulator that accumulates pressure when the engine is running, and a pilot directional switching valve that is closed when the engine is running and communicates when the engine is stopped,
The work vehicle according to claim 1, wherein the accumulator is configured to supply pressure oil to the hydraulic brake cylinder via the pilot type directional switching valve in the closed circuit when the engine is stopped. 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 1 , wherein the accumulator is connected to the inlet side of the pilot type directional switching valve, and the left brake cylinder and the right brake cylinder are connected to the outlet side, respectively.

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