JPH032765Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a hydraulically driven vehicle that runs on hydraulic pressure, and particularly relates to alleviating shock when starting or stopping the vehicle.

Prior Art In industrial vehicles such as aerial work vehicles, hydraulic fluid is pumped from a pump and supplied to a hydraulic motor via a control valve, and the wheels are rotationally driven by the hydraulic motor to move forward or backward. There is a hydraulically driven type that can be used. and,
In such hydraulically driven vehicles, when the hydraulic motor is stopped, it is rotated by an external force, and there is a risk that the vehicle may move irrespective of the driver's will. During this period, a counterbalance valve is often installed to prevent the flow of hydraulic oil from the hydraulic motor to the control valve when hydraulic oil is not supplied from the control valve. Unwanted vehicle movement is prevented.

Problems to be Solved by the Invention However, in a hydraulically driven vehicle equipped with the above-mentioned counterbalance valve, the supply of hydraulic fluid is started or stopped by switching the control valve, and when the counterbalance valve is operated, Since the hydraulic motor is suddenly rotated or its rotation is blocked, there is a problem in that the driver is given a large shock when starting or stopping the vehicle.

Means for Solving the Problems The present invention has been made to solve the above problems, and its gist is that in a hydraulically driven vehicle equipped with the above-mentioned counterbalance valve, the forward side of the hydraulic motor is The reason is that a double-acting accumulator is connected between the circuit and the reverse circuit. In addition, here, what is a double-acting accumulator?
This is an accumulator that has pressure accumulators on both sides of a movable member that is held in a neutral position by an elastic member, and both pressure accumulators are connected to a forward circuit and a reverse circuit, respectively.

Function In such a hydraulically driven vehicle, when the control valve is switched to move the vehicle forward or backward and hydraulic oil is pumped from the pump, the counterbalance valve is operated accordingly, and the control valve The hydraulic oil is allowed to flow toward the hydraulic motor, causing the hydraulic motor to rotate, but a portion of the hydraulic oil flows into the pressure accumulator connected to the high-pressure side of the forward and reverse circuits of the accumulator. flows into. Therefore, the amount of hydraulic oil supplied to the hydraulic motor is reduced by that amount, and the hydraulic motor starts rotating smoothly, which alleviates the shock when the vehicle starts.

On the other hand, when a control valve is switched to stop a running vehicle, the supply of hydraulic oil is stopped and the counterbalance valve is activated, blocking the flow of hydraulic oil from the hydraulic motor to the control valve. However, the hydraulic oil discharged from the hydraulic motor flows into one pressure accumulation chamber of the accumulator, and as mentioned above, the hydraulic oil stored in the other pressure accumulation chamber is supplied to the hydraulic motor, so the control valve cannot be switched. Afterwards, the hydraulic motor is allowed to rotate for a while, thereby avoiding a sudden stop of the vehicle.Also, since this invention uses a double-acting accumulator, hydraulic oil is not allowed to flow into one pressure accumulator while driving. Since the movable member of the accumulator is moved from the neutral position to the other pressure accumulation chamber side by the flow, when the vehicle is stopped, the elastic member that biases the movable member toward the neutral position removes the pressure from the hydraulic motor. The discharged hydraulic fluid is actively sucked into the other pressure accumulation chamber. Furthermore, since the movable member is always kept in a neutral position by the elastic member, no hydraulic pressure remains in the hydraulic fluid when the vehicle is stopped due to the presence of the accumulator.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a diagram showing a hydraulic circuit for driving a hydraulically driven vehicle according to the present invention, in which hydraulic oil stored in a tank 10 is pumped up by a pump 14 rotationally driven by an engine 12, and is pumped up by a pipe 16. The water is fed under pressure to the control valve 18 through the. The control valve 18 is an operating lever 20 located at the driver's seat.
It can be switched to three positions, forward, backward, and stopped, by operating the . The hydraulic oil pumped up by the pump 14 is returned to the tank 10 as it is. Also, when the control valve 18 is operated to the forward or backward position, these pipes 1
6 and 22 are connected to two hydraulic systems 24a and 24b, respectively, and are connected to the left and right drive wheels 26.
a and 26b are rotated in the forward or backward direction, respectively. Note that a relief valve 28 is connected between the pipes 16 and 22.

Since the hydraulic systems 24a and 24b are configured in exactly the same way, only the hydraulic system 24a will be described below, and the description of the hydraulic system 24b will be omitted, with reference numerals replacing a with b.

The hydraulic system 24a includes a counterbalance valve 34a connected to the control valve 18 through conduits 30a and 32a, and a hydraulic motor (hereinafter simply referred to as motor) 40 connected to the counterbalance valve 34a through conduits 36a and 38a.
The drive wheel 26a is connected to the motor 40a. As is clear from the figure, the counterbalance valve 34a
The flow of hydraulic oil from 0a to 36a is allowed, but the flow in the opposite direction is only allowed when oil pressure is applied from pipe 32a.
The flow of hydraulic oil from a to 38a is allowed, but the flow in the opposite direction is allowed only when oil pressure is applied from the pipe 30a. A shuttle valve 44a connected to a brake device 42a is also provided in this counterbalance valve 34a, and when hydraulic oil is supplied to either one of the pipes 30a and 32a, the brake device 42a and motor 40a.
rotation is now allowed.

When the control valve 18 is operated to the forward position, the pipe line 16 is moved to the pipe line 3.
0a, and the pipe line 22 is also made to communicate with the pipe line 32a, and the hydraulic oil pumped from the pump 14 is supplied to the counterbalance valve 34a via the pipe line 30a, so that the pipe line 22 is connected to the pipe line 38a. The flow of hydraulic oil toward 32a is allowed, and the brake device 42a is released, allowing the motor 40a to rotate. Therefore, the hydraulic oil is further supplied to the motor 40a through the pipe 36a, and the drive wheel 26a is rotationally driven in the forward direction by the motor 40a.
The hydraulic fluid discharged from the tank 10 is returned to the tank 10 via the pipe 38a, the counterbalance valve 34a, the pipe 32a, and the pipe 22. Further, when the control valve 18 is operated to the backward position, the hydraulic oil pumped from the pump 14 is supplied in the opposite direction to that described above, and the drive wheels 26a are rotationally driven in the backward direction.

Between the forward side circuit and the backward side circuit of the pump 26a, that is, between the pipes 36a and 38a,
A double-acting accumulator 46 is connected.
The accumulator 46 includes a piston 50 fluid-tightly and slidably fitted within a housing 48, and a pair of springs 52 and 54 that bias the piston 50 from both sides and hold it in the neutral position shown in the figure. Pressure accumulating chambers 56 and 58 are formed on both sides of the piston 50 within the housing 48 and communicate with the conduits 36a and 38a, respectively. Note that this accumulator 46 is shared with the other hydraulic system 24b.

In a hydraulically driven vehicle equipped with such an accumulator 46, when the control valve 18 is switched from the stop position shown in the figure to the forward position as described above, the hydraulic fluid pumped from the pump 14 causes the motor 40a to is rotated, but
At this time, since rotational resistance exists in the motor 40a due to the inertia of the vehicle, a portion of the supplied hydraulic oil flows into one pressure accumulation chamber 56 of the accumulator 46 from the pipe 36a. Therefore, the motor 40a
The amount of hydraulic oil supplied to the motor 40a decreases by that amount, and the motor 40a starts rotating smoothly, relieving the shock when the vehicle starts.

Then, while driving, the accumulator 4
The piston 50 of No. 6 is connected to the hydraulic pressure of the pipe 36a and the pipe 3
Based on the pressure difference with the oil pressure of 8a, it is held closer to the pressure accumulation chamber 58 than the neutral position.

On the other hand, when the control valve 18 is switched to the stop position in order to stop the running vehicle, the supply of hydraulic oil is stopped, the counterbalance valve 34a is activated, and the flow is changed from the pipe 38a to the pipe 32a. However, the hydraulic oil discharged from the motor 40a flows into the pressure accumulation chamber 58 of the accumulator 46 through the pipe 38a, and the hydraulic oil stored in the pressure accumulation chamber 56 is blocked. Since it is supplied to the motor 40a through the conduit 36a, the rotation of the motor 40a is allowed for a while thereafter, thereby avoiding a sudden stop of the vehicle. At this time, since the piston 50 of the accumulator 46 is urged toward the neutral position by the urging force of the spring 54, hydraulic oil is actively sucked into the pressure accumulation chamber 58. When the piston 50 is returned to the neutral position, further movement is suppressed by the biasing force of the spring 52, and at this time, the brake device 42a is already in the operating state.
As described above, the motor 40a can be stopped quickly without giving a large shock to the vehicle. Incidentally, since the piston 50 is always held at the neutral position by the springs 52 and 54, if the motor 40a is completely stopped and the piston 50 is held at the almost neutral position, the accumulator 46 No hydraulic pressure remains in the hydraulic circuit due to the presence of.

Further, the shock at the time of starting when the control valve 18 is operated to switch from the stop position to the reverse position, and the shock at the time of stopping when the control valve 18 is operated to switch from the stop position to the stop position are alleviated by the action of the accumulator 46. This is exactly the same as the case of forward movement described above.

Next, another embodiment of the present invention will be described.

The accumulator 60 shown in FIG. 2 is used in place of the accumulator 46 of the previous embodiment, but compared to the accumulator 46, the accumulators 64 and 66 are formed on both sides of the piston 62.
has a larger diameter than the piston 62, and its housing 6
The spring receivers 72 and 74 of the pair of springs 68 and 70 are seated on the stepped portion 7, so that the piston 62 is held at the neutral position. In this way, the piston 62 is stably held at an accurate neutral position based on the biasing forces of both springs 68 and 70. In addition, it is easy to appropriately determine the set load and spring constant of the springs 68 and 70 by taking into account the oil pressure of the hydraulic oil and the force applied to the motor from the outside. Since the piston 62 does not easily move from the neutral position even if the piston 62 is moved, there is an advantage that rotation of the motor and further movement of the vehicle are reliably prevented.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, one accumulator 46 or 60 may be connected to two hydraulic systems 24a and 24.
4b, but each hydraulic system 2
There is no problem in providing separate accumulators 46 or 60 for 4a and 24b. Further, the type of the accumulator is not limited to that of the embodiment described above.

Further, in the embodiment, the counterbalance valve 34
Shuttle valves 44a and 44 at a and 34b
b is attached, but this shuttle valve 44a
and 44b may be provided separately from the counterbalance valves 34a and 34b, and the shuttle valve itself may be omitted. In addition,
These shuttle valves 44a and 44b control the operation of brake devices 42a and 42b,
Especially when the hydraulic circuit is damaged, the motors 40a and 40
The rotation of the motors 40a and 40b and the movement of the vehicle may be prevented by other means, and such means may be omitted. be.

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit thereof.

Effects of the invention As detailed above, in the hydraulically driven vehicle of the invention, a double-acting accumulator is connected between the forward side circuit and the reverse side circuit of the hydraulic motor. As hydraulic oil flows in and out of the accumulator, the motor starts and stops smoothly, easing the shock to the driver and vehicle, and also enables inching operation, which moves the vehicle small distances at a time. Become. Also, compared to the case where single-acting accumulators are provided separately for the forward side circuit and the reverse side circuit,
Not only is the structure of the accumulator and the hydraulic circuit simplified, but also no hydraulic pressure remains in the hydraulic circuit in the stopped state.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a hydraulic circuit for driving a hydraulically driven vehicle according to an embodiment of the present invention. FIG. 2 is a sectional view of an accumulator in another embodiment of the present invention. 14...Pump, 18...Control valve, 26a, 26b...Drive wheel, 34a, 34b
...Counter balance valve, 36a, 36b...Pipe line (forward circuit), 38a, 38b...Pipe line (reverse side circuit), 40a, 40b...Hydraulic motor, 4
6,60...Accumulator.

Claims (1)

[Scope of utility model registration request] In a hydraulically driven vehicle that runs by having hydraulic fluid pumped from a pump controlled by a control valve and supplied to a hydraulic motor via a counterbalance valve, and wheels being driven by the hydraulic motor, A hydraulically driven vehicle characterized in that a double-acting accumulator is connected between a forward side circuit and a backward side circuit of a hydraulic motor.