JP7688545B2 - mobile agricultural machinery - Google Patents

Description

The present invention relates to a mobile agricultural machine equipped with a power steering hydraulic circuit that hydraulically controls a power steering mechanism and a front wheel speed increasing hydraulic circuit that hydraulically controls a front wheel speed increasing mechanism.

Conventionally, when mobile agricultural machinery such as tractors are making a sharp turn, if the steering angle exceeds a predetermined value, the transmission mechanism drivingly connected to the front wheels is hydraulically controlled to reduce the gear ratio and increase the rotational speed of the front wheels, thereby increasing the relative speed difference between the front and rear wheels and reducing the turning radius.

In such mobile agricultural machinery, the hydraulic pressure generated by the hydraulic pump must be diverted to be supplied not only to the front wheel speed doubling hydraulic circuit that supplies the front wheel speed doubling mechanism, but also to the power steering hydraulic circuit and the lift mechanism hydraulic circuit, etc., but this can lead to a complicated diverter valve. Therefore, a proposal has been made to simplify the diverter valve by supplying the back pressure of the power steering hydraulic circuit to the front wheel speed doubling hydraulic circuit (see Patent Document 1).

JP 2003-205851 A

In the cited document 1, when the back pressure of the power steering hydraulic circuit exceeds a certain pressure, there is a risk of load being placed on the components of the power steering hydraulic circuit and the components of the front wheel double speed hydraulic circuit to which the back pressure is supplied, so a relief valve (44) is provided as a safety valve to maintain the back pressure at a constant pressure. However, this relief valve does not open until the back pressure exceeds a certain pressure, meaning that the back pressure of the power steering hydraulic circuit is always maintained at a constant pressure. This constantly prevents the hydraulic pressure from being discharged from the power steering hydraulic circuit, which constantly places a load on the hydraulic pump, resulting in problems such as output loss in the drive system to which the hydraulic pump is connected, an increase in oil temperature, an impact on the life of the hydraulic pump, and increased noise from the hydraulic pump. In addition, small engines are often used, particularly in mobile agricultural machines such as small tractors, and there is also the problem that the load on the hydraulic pump has a large impact on the engine output.

The present invention aims to provide a mobile agricultural machine that can reduce the load on the hydraulic pump.

A mobile agricultural machine (1) according to one embodiment of the present invention comprises:
a power steering mechanism (30) that hydraulically applies steering force to the front wheels (2);
a front wheel speed increasing mechanism (9B) that hydraulically switches a transmission path based on a steering angle of the front wheels (2) reaching a predetermined value or more, thereby increasing the rotation speed of the front wheels to be faster than the rotation speed of the rear wheels (3);
A hydraulic pump (21) that generates hydraulic pressure;
a hydraulic control circuit (20) including a power steering hydraulic circuit (40) that hydraulically controls the power steering mechanism (30) based on hydraulic pressure supplied from the hydraulic pump (21), and a front wheel acceleration hydraulic circuit (60) that hydraulically controls the front wheel acceleration mechanism (9B) based on back pressure supplied from the power steering hydraulic circuit (40),
The front wheel acceleration hydraulic circuit (60)
a safety valve (62) that discharges hydraulic pressure when the back pressure exceeds a predetermined pressure;
The front wheel acceleration mechanism (9B) is characterized by having a switching valve (61) that switches between a first state (61A) in which the back pressure is supplied to a hydraulic servo (51) of the front wheel acceleration mechanism (9B) to switch the transmission path and increase the rotational speed of the front wheels (2), and a second state (61B) in which the back pressure and the hydraulic pressure of the hydraulic servo (51) are discharged.

In addition, the mobile agricultural machine (1) according to one embodiment of the present invention is
A lifting mechanism (13) capable of controlling the lifting state of a work machine,
The hydraulic control circuit (20) is characterized by having a branching section (22) that branches the hydraulic pressure supplied from the hydraulic pump (21) to the power steering hydraulic circuit (40), and a lifting mechanism hydraulic circuit (80, 90) that hydraulically controls the lifting mechanism (13) based on the hydraulic pressure supplied from the hydraulic pump (21) via the branching section (22).

And, the mobile agricultural machine (1) according to one embodiment of the present invention is as follows:
The lifting mechanism (13) is capable of controlling the horizontal state of the working machine,
The hydraulic circuit for the lifting mechanism is characterized by having a horizontal control circuit (80) that hydraulically controls the horizontal state of the working machine, and a lifting control circuit (90) that hydraulically controls the lifted state of the working machine.

The symbols in parentheses above are for comparison with the drawings, but this is for convenience to make the invention easier to understand and does not affect the structure of the claims in any way.

According to the present invention, in the second state in which the front wheels are not accelerated, the load on the hydraulic pump can be reduced, improving the output of the PTO shaft, suppressing the rise in oil temperature, extending the life of the hydraulic pump, reducing the noise of the hydraulic pump, etc.

1 is an overall view showing a tractor according to an embodiment of the present invention; 1A is a top view showing a drive system according to the present embodiment, and FIG. 1B is a side view showing the drive system according to the present embodiment. FIG. 2 is a perspective view showing a rear portion of a drive system according to the present embodiment. FIG. 2 is a diagram showing a hydraulic control circuit of the tractor according to the present embodiment.

The following describes an embodiment of the present invention with reference to Figures 1 to 4. First, the general configuration of a tractor 1 according to the present embodiment is described with reference to Figures 1 to 3.

[General configuration of tractor]
A tractor 1 as a mobile agricultural machine according to this embodiment is, for example, a small tractor, and as shown in Fig. 1, has a body 5 supported by front wheels 2 and rear wheels 3 having a front wheel turning angle sensor (not shown) that detects the amount of longitudinal movement of a tie rod, and this body 5 has a driver's seat 7 disposed in the upper center portion, an engine 6 disposed in front, and a transmission 9 disposed behind the engine 6. Also, at the rear of the body 5, a lifting mechanism 13 is disposed to enable a working machine (not shown) that is drive-coupled to a PTO shaft (not shown) to which driving force is output from the transmission 9 to be raised and lowered and its horizontal state to be adjusted.

The driver's seat 7 is provided with a steering wheel 7a as a steering wheel, a main speed change lever 10 for operating the main speed change device (not shown) of the transmission 9, and an auxiliary speed change lever 11 for operating the auxiliary speed change device (not shown) of the transmission 9. The driver's seat 7 is also provided with a driving force switching lever (not shown) for switching the transmission 9 between a two-wheel drive state in which driving force is transmitted only to the rear wheels 3 and a four-wheel drive state in which driving force is transmitted to the rear wheels 3 and the front wheels 2, and a quick turn switching lever (not shown) for switching between the four-wheel drive state and a front-wheel double speed state in which a rotation speed approximately twice that of the rear wheels 3 is transmitted to the front wheels 2.

[Configuration of Tractor Drive System and Hydraulic Path]
Next, the details of the drive system and hydraulic paths of the tractor 1 will be described with reference to Figures 2 and 3. As shown in Figures 2(a), 2(b) and 3, in the drive system of the tractor 1, the engine 6 is disposed at the front, and a transmission 9 drivingly connected to the engine 6 is disposed behind it. The transmission 9 is provided with a travel speed change mechanism 9A that changes the speed of the rotation of the engine 6 and transmits it to the rear wheels 3 or to the rear wheels 3 and the front wheels 2, and is provided with a front wheel speed increase mechanism 9B that increases (doubles) the speed of the rotation of the front wheels 2 on the transmission path to the front wheels 2 forward of the travel speed change mechanism 9A.

Above the transmission 9, there is disposed a power steering mechanism 30 that applies a steering force to the front wheels 2 by rotating the steering wheel 7a. The power steering mechanism 30 is provided with a power steering hydraulic circuit 40, which is a so-called orbit roll.

Meanwhile, behind the transmission 9 is a lifting mechanism 13 that can control the lift and horizontal state of a work machine (not shown) that is drive-connected to a PTO shaft (not shown), i.e., raises and lowers the work machine and adjusts its horizontal position. As shown in FIG. 3, the lifting mechanism 13 is equipped with a lifting arm 13A that raises and lowers the work machine, and a horizontal arm 13B that adjusts the work machine horizontally.

As shown in Figures 2(a), 2(b), and 3, an oil passage L0 consisting of a pipe that supplies oil from the transmission 9 to the hydraulic filter 19 is connected to the lower right side of the aircraft body 5, and an oil passage L1 that connects the hydraulic filter 19 to the hydraulic pump 21 is arranged so as to pass under the aircraft body 5. The hydraulic pump 21 supplies the generated hydraulic pressure to the oil passages L3 and L4 through a branch valve 22 that serves as a branching section that branches and supplies hydraulic pressure. The oil passage L4 passes under the left side of the aircraft body 5 and is connected to the lifting mechanism 13, and one of the oil passages L3 is connected to the power steering hydraulic circuit 40. The back pressure of the power steering hydraulic circuit 40, which will be described in detail later, is output to the oil passage L5 connected to the power steering hydraulic circuit 40 and is connected to the front wheel acceleration hydraulic circuit 60 located on the rear right side of the aircraft body 5. The front wheel acceleration hydraulic circuit 60 and the front wheel acceleration mechanism 9B are connected via the oil passage L15.

[Details of hydraulic control circuit]
Next, the hydraulic control circuit 20 of the tractor 1 according to this embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the hydraulic pump 21 is driven by being drivingly connected to the engine 6, and draws in oil via an oil passage L0, a hydraulic filter 19, and an oil passage L1 to generate hydraulic pressure, which is then discharged to an oil passage L2. The hydraulic pressure of the hydraulic pump 21 supplied to the oil passage L2 is supplied to an oil passage L3 and an oil passage L4 by a branch valve 22.

(Hydraulic circuit for lifting mechanism)
First, the horizontal control circuit 80 and the lift control circuit 90 constituting the hydraulic circuit for the lift mechanism will be described in detail. The hydraulic pressure supplied to the oil passage L4 is input to the horizontal lift switching valve 71 of the horizontal lift switching unit 70. The spool of the horizontal lift switching valve 71 is located at a horizontal control position 71A by the biasing force of a spring, and is switched to a horizontal lift control position 72B against the biasing force of the spring by the drive of a solenoid (not shown). That is, the horizontal lift switching valve 71 supplies hydraulic pressure to the horizontal control circuit 80, which is one of the hydraulic circuits for the lift mechanism, at the horizontal control position 71A, and supplies hydraulic pressure to the horizontal control circuit 80 and the oil passage L6 at the horizontal lift control position 71B, that is, also supplies hydraulic pressure to the lift control circuit 90 described later.

In the horizontal control circuit 80, the hydraulic pressure input by the safety valve 81 is adjusted to a certain pressure or less while supplying hydraulic pressure to the left-right switching valve 82. The spool of the left-right switching valve 82 is switched to the right-up position 82A, the middle position 82B, and the left-up position 82C by being driven by a solenoid (not shown). That is, when the spool of the left-right switching valve 82 is switched to the left-up position 82C, hydraulic pressure is supplied to the oil chamber 84b of the opposed hydraulic servo 84, and the hydraulic pressure in the oil chamber 84a is discharged, so that the horizontal arm 13B (see FIG. 3) is raised. Conversely, when the spool of the left-right switching valve 82 is switched to the right-up position 82A, hydraulic pressure is supplied to the oil chamber 84a of the opposed hydraulic servo 84, and the hydraulic pressure in the oil chamber 84b is discharged through the check valve 83 that is opened by the hydraulic pressure in the oil chamber 84a, so that the horizontal arm 13B (see FIG. 3) is lowered. While the spool of the left/right switching valve 82 is switched to the intermediate position 82B, hydraulic pressure from the horizontal lift switching unit 70 is not supplied to the opposed hydraulic servo 84, but is instead discharged, and the horizontal state of the work machine is maintained.

When the spool of the horizontal lift switching valve 71 is switched to the horizontal lift control position 71B, hydraulic pressure is supplied from the oil passage L6 to the lift control unit 100, and the hydraulic pressure input by the safety valve 91 is adjusted to a certain pressure or less while supplying hydraulic pressure to the lift control circuit 90. The lift control circuit 90 is configured with a lubrication switching valve 93, a discharge switching valve 94, and a lubrication cutoff switching valve 95.

In detail, when the spool of the horizontal lift switching valve 71 is switched to the horizontal lift control position 71B, the oil pressure adjusted to a certain pressure or less by the safety valve 91 is supplied from the oil passage L6 to the lubrication switching valve 93. The spool of the lubrication switching valve 93 is switched to the first lubrication stop position 93A, the second lubrication stop position 93B, the first lubrication supply position 93C, and the second lubrication supply position 93D by driving the lever 112 by a solenoid (not shown). The lubrication switching valve 93 supplies oil pressure to the check valve 96 regardless of the position of the spool, and enables the oil pressure to be supplied to the hydraulic servo 98 that presses the lift arm 13A in the upward direction via the oil passage L7 and the discharge adjustment valve 97 that has a check valve and a variable orifice and adjusts the discharge amount.

In addition, hydraulic pressure is also supplied from the lubrication switching valve 93 to the lubrication cutoff switching valve 95. The spool of the lubrication cutoff switching valve 95 can be switched between a lubrication supply position 95A in which lubrication oil is supplied to the lifting mechanism 13 via the oil passage L8, and a lubrication cutoff position 95B in which the hydraulic pressure is cut off to stop the supply of lubrication oil. When the spool of the lubrication switching valve 93 is in the first lubrication stop position 93A and the second lubrication stop position 93B, hydraulic pressure is input to the lubrication cutoff switching valve 95, and the spool is in the lubrication cutoff position 95B against the spring force, and when the spool of the lubrication switching valve 93 is in the first lubrication supply position 93C and the second lubrication supply position 93D, the hydraulic pressure to the lubrication cutoff switching valve 95 is cut off and the spool is in the lubrication supply position 95A by the spring force. In addition, in the second lubrication stop position 93B, the hydraulic pressure supply to the lubrication cutoff switching valve 95 and the oil passage L7 is throttled by throttling the port of the lubrication cutoff switching valve 95.

The discharge switching valve 94 has its spool switched to the hydraulic discharge stop position 94A or the hydraulic discharge position 94B by driving the lever 111 by a solenoid (not shown). When the spool of the discharge switching valve 94 is switched to the hydraulic discharge stop position 94A, the built-in check valve blocks the path for discharging the hydraulic pressure of the hydraulic servo 98 through the oil passage L7, that is, the hydraulic pressure supplied to the hydraulic servo 98 is not discharged, and the lifting arm 13A is raised. When the spool of the discharge switching valve 94 is switched to the hydraulic discharge position 94B, the hydraulic pressure of the hydraulic servo 98 is discharged through the oil passage L7, and the lifting arm 13A (and the work machine) is lowered by its own weight. The position of the lever 112 is restricted by the lever 111, and when the spool of the discharge switching valve 94 is switched to the hydraulic discharge stop position 94A, the spool of the lubrication switching valve 93 is configured not to move to the second lubrication supply position 93D.

(Power steering hydraulic circuit)
Next, the power steering hydraulic circuit 40 will be described. The hydraulic pressure supplied from the hydraulic pump 21 to the oil passage L3 via the branch valve 22 is supplied to the power steering hydraulic circuit 40, which is a so-called orbital roll, and is adjusted to a certain pressure or less by the pressure regulating valve 41 and supplied to the steering pressure control valve 44 as pilot pressure, while the surplus pressure adjusted by the pressure regulating valve 41 is supplied to the oil passage L5 as back pressure discharged from the power steering hydraulic circuit 40. The back pressure is adjusted by the check valve 42 so that it does not exceed the supplied pilot pressure.

The spool of the steering pressure control valve 44 is moved between the right assist position 44A, the intermediate position 44B, and the left assist position 44C by the steering shaft 32 connected to the steering wheel 7a. In other words, when the steering wheel 7a is turned to the right, the spool of the steering pressure control valve 44 moves to the right assist position 44A, and conversely, when the steering wheel 7a is turned to the left, the spool of the steering pressure control valve 44 moves to the left assist position 44C.

When the steering pressure control valve 44 moves to the right assist position 44A, pilot pressure is supplied to the metering pump 45 with servo feedback and to the power steering cylinder 31 via the oil passage L31, turning the front wheels 2 to the right via a steering rod (not shown). Conversely, when the steering pressure control valve 44 moves to the left assist position 44C, pilot pressure is supplied to the metering pump 45 with servo feedback and to the power steering cylinder 31 via the oil passage L32, turning the front wheels 2 to the left via a steering rod (not shown). A turning angle sensor (not shown) is disposed on this steering rod, and when the turning angle of the front wheels 2 reaches a predetermined value, a solenoid is driven by a control unit (not shown) to switch the spool of the front wheel acceleration switching valve 61, which will be described in detail later, to the acceleration position 61A.

(Front wheel acceleration hydraulic circuit)
Next, the front wheel acceleration hydraulic circuit 60 will be described. The back pressure of the power steering hydraulic circuit 40 is supplied to the front wheel acceleration hydraulic circuit 60 via an oil line L5 and input to an oil line L11. The back pressure of the power steering hydraulic circuit 40 supplied to the oil line L11 is supplied to a front wheel acceleration switching valve 61 as a switching valve, and is also supplied to a safety valve 62 via an oil line L12.

The spool of the front wheel acceleration switching valve 61 is moved and switched between an acceleration position 61A as a position for forming the second state and a normal position 61B as a position for forming the first state. That is, as described above, a solenoid (not shown) is driven based on the position of the steering rod, i.e., the turning angle of the steering wheel 7a, becoming equal to or greater than a predetermined value, and the spool of the front wheel acceleration switching valve 61 is switched to the acceleration position 61A. In the acceleration position 61A state, the oil passage L11 and the oil passage L14 are blocked and the oil passage L11 and the oil passage L15 are connected, and the back pressure of the power steering hydraulic circuit 40 is supplied as operating pressure to the hydraulic servo 51 of the front wheel acceleration mechanism 9B via the oil passage L15. As a result, in the front wheel speed increasing mechanism 9B, the transmission path that passes through gears with a normal speed ratio (a speed ratio that makes the front wheels 2 rotate at approximately the same speed as the rear wheels 3) is cut off, and a transmission path that passes through gears with a speed ratio that increases the speed of the front wheels 2 relative to the rear wheels 3 (approximately double the speed in this embodiment), i.e., the rotational speed of the front wheels 2 is increased relative to the rear wheels 3, reducing the turning radius of the tractor 1 and allowing it to make sharp turns.

When the spool of the front wheel acceleration switching valve 61 is in the acceleration position 61A, the safety valve 62 acts to keep the back pressure of the power steering hydraulic circuit 40 below a predetermined pressure. In other words, when the back pressure of the oil passage L12 becomes greater than the predetermined pressure, the safety valve 62 opens against the spring force, discharging the oil pressure through the oil passage L13 and maintaining the oil pressure in the oil passages L12, L11, and L15 below the predetermined pressure.

After that, when the steering angle of the steering wheel 7a falls below a predetermined value, a solenoid (not shown) is driven and the spool of the front wheel acceleration switching valve 61 is switched to the normal position 61B. Then, the oil lines L15 and L14 are connected, and the oil lines L11 and L14 are connected, meaning that the operating pressure of the hydraulic servo 51 is discharged and the back pressure of the power steering hydraulic circuit 40 is also discharged as is. As a result, in the front wheel acceleration mechanism 9B, the transmission path that accelerates the front wheels 2 relative to the rear wheels 3 is returned to the transmission path of the normal gear ratio, meaning that the front wheels 2 are made to run at approximately the same speed as the rear wheels 3, enabling normal driving.

As described above, in the front wheel acceleration hydraulic circuit 60, when the spool of the front wheel acceleration switching valve 61 is in the normal position 61B, that is, in the normal driving state in which the tractor 1 is not accelerating the front wheels, the back pressure of the power steering hydraulic circuit 40 is discharged from the oil passage L14, so that the power steering hydraulic circuit 40 is not loaded by the back pressure. This reduces the load on the hydraulic pump 21 that supplies hydraulic pressure to the power steering hydraulic circuit 40, and reduces the output loss of the drive system due to the drive of the hydraulic pump 21, so that the driving power of the engine 6 and the output of the PTO shaft during normal driving can be improved. Furthermore, since the drive load of the hydraulic pump 21 is reduced, the increase in oil temperature caused by the hydraulic pump 21 is also reduced, and the hydraulic pump can be made to have a longer life and reduce noise. In particular, in a small tractor 1 like the present embodiment, where the engine 6 is small and has low maximum output performance, the engine output reserve is not very large, but by reducing the load on the hydraulic pump 21, the engine 6 reserve can be secured, improving the driving output and the output of the PTO shaft.

In addition, the hydraulic control circuit 20 is configured to supply hydraulic pressure from the hydraulic pump 21 to the horizontal control circuit 80 and the lift control circuit 90 as hydraulic circuits for the lift mechanism via the branch valve 22. This means that one hydraulic pump 21 supplies hydraulic pressure to the power steering hydraulic circuit 40, the front wheel acceleration hydraulic circuit 60, the horizontal control circuit 80, and the lift control circuit 90. However, since the load on the power steering hydraulic circuit 40 due to back pressure is reduced, there is a margin in the hydraulic pressure supply for the horizontal control and lift control of the work machine, making it possible to perform these hydraulic controls with high precision.

[Possible other embodiments]
In the above-described embodiment of the tractor 1, the front wheels are accelerated, but the invention is not limited to this. For example, the inside of the front wheels 2 may be braked to stop rotation during a sharp turn. In this case, a brake hydraulic circuit may be provided to supply hydraulic pressure to the brake, and the back pressure of the power steering hydraulic circuit 40 may be supplied to the brake hydraulic circuit.

In addition, in the present embodiment, the tractor 1 is described as having a horizontal arm that adjusts the horizontal position of the work implement and a horizontal control circuit 80 that hydraulically controls it, but the present invention is not limited to this, and it is also possible for the tractor 1 to only adjust the elevation position of the work implement and not have a horizontal control circuit 80.

In addition, in this embodiment, a tractor 1 has been described as an example of a mobile agricultural machine, but this is not limited to this, and it may be, for example, a rice planter, or any other mobile agricultural machine as long as it is equipped with a power steering mechanism and a front wheel acceleration mechanism.

1...Mobile agricultural machinery (tractor)
2...Front wheels 3...Rear wheels 7a...Steering (steering wheel)
9B: Front wheel acceleration mechanism 13: Lifting mechanism 20: Hydraulic control circuit 21: Hydraulic pump 22: Branching section (branching valve)
30... Power steering mechanism 40... Power steering hydraulic circuit 60... Front wheel acceleration hydraulic circuit 61... Switching valve (front wheel acceleration switching valve)
61A: First state (speed increasing position)
61B: Second state (normal position)
62: Safety valve 80: Hydraulic circuit for lifting mechanism, horizontal control circuit 90: Hydraulic circuit for lifting mechanism, lifting control circuit

Claims (3)

a power steering mechanism that applies steering force to the front wheels by hydraulic pressure;
a front wheel acceleration mechanism that hydraulically switches a transmission path based on a steering angle of the front wheels reaching a predetermined value or more, thereby increasing the rotational speed of the front wheels to be faster than the rotational speed of the rear wheels;
A hydraulic pump that generates hydraulic pressure;
a hydraulic control circuit including a power steering hydraulic circuit that hydraulically controls the power steering mechanism based on the hydraulic pressure supplied from the hydraulic pump, and a front wheel acceleration hydraulic circuit that hydraulically controls the front wheel acceleration mechanism based on the back pressure supplied from the power steering hydraulic circuit,
The front wheel acceleration hydraulic circuit includes:
a safety valve that discharges hydraulic pressure when the back pressure exceeds a predetermined pressure;
a switching valve that switches between a first state in which the back pressure is supplied to a hydraulic servo of the front wheel acceleration mechanism to switch the transmission path and increase the rotational speed of the front wheels, and a second state in which the back pressure and the hydraulic pressure of the hydraulic servo are discharged.
A mobile agricultural machine characterized by: Equipped with a lifting mechanism capable of controlling the lifting state of the work machine,
The hydraulic control circuit includes a branching section that branches the hydraulic pressure supplied from the hydraulic pump to the power steering hydraulic circuit, and a lifting mechanism hydraulic circuit that hydraulically controls the lifting mechanism based on the hydraulic pressure supplied from the hydraulic pump via the branching section.
2. The mobile agricultural machine according to claim 1. The lifting mechanism is capable of controlling a horizontal state of the work machine,
The lifting mechanism hydraulic circuit has a horizontal control circuit that hydraulically controls the horizontal state of the working machine, and a lifting control circuit that hydraulically controls the lifting state of the working machine.
3. The mobile agricultural machine according to claim 2.

Images