JP5112280B2 - Travel system control circuit - Google Patents

Description

  The present invention relates to a travel system control circuit for driving a pair of travel motors.

As this type of control circuit, those shown in FIGS. 2 and 3 are conventionally known. This conventional control circuit includes a pair of travel motor connection passages 1 and 2 connected to one of the travel motors, and a pair of travel motor connection passages 3 and 4 connected to the other travel motor. In addition, the travel motor connection passages 1, 2 and 3, 4 are connected to the first and second control valves V1, V2.
Since the first and second control valves V1 and V2 have the same configuration, the following description will be given with the same reference numerals.

As shown in FIG. 3, the first and second control valves V1, V2 are provided with a pair of actuator ports 5, 6 communicating with the travel motor connection passages 1, 2, 3, 4, and A connected pump port 7 and a tank port 8 connected to the tank T are provided.
Further, the first and second control valves V1 and V2 include an outflow port 11 connected to an inlet of first and second pressure compensation valves 9 and 10 provided separately from the control valve, and these first and second pressure compensation valves. Inflow ports 12 and 13 connected to the outlet sides of 9 and 10 are provided.

The first and second control valves V1 and V2 as described above normally maintain the neutral position shown in the figure by the action of the spring force of the centering springs 14 and 15, but either of the pilot chambers 16 and 17 provided on the left and right sides. On the other hand, the pilot pressure is applied to switch to the switching position.
When the first and second control valves V1 and V2 are in the illustrated neutral position, the pump port 7 and the inflow ports 12 and 13 are closed, and the actuator ports 5 and 6 and the outflow port 11 communicate with the tank port 8. .

When the first and second control valves V1 and V2 are switched to the switching position, the pump port 7 and the outflow port 11 are communicated with each other, and either the inflow port 12 or 13 is connected to either of the actuators. The other actuator port 6 or 5 communicates with the tank port 8.
When the first and second control valves V1 and V2 are switched as described above, the pressure fluid from the pump mechanism P is supplied to the pump port 7 → the outflow port 11 → the pressure compensation valve 9 (10) → one inflow port. 12 or 13 → supplied to the traveling motor via one of the actuator ports 5 or 6.
The return fluid from the traveling motor is returned to the tank T via one of the actuator ports 6 or 5 and the tank port 8.
Therefore, the traveling motor connected to the traveling motor connection passages 1 and 2 (3, 4) rotates forward or reverse depending on the switching direction of the first and second control valves V1 and V2.

Further, as shown in FIGS. 2 and 3, the outflow ports 11 of the first and second control valves V <b> 1 and V <b> 2 are always communicated with each other via a communication path 18, and a throttle 19 is provided in the communication path 18.
The reason why the outflow ports 11 of the first and second control valves V1 and V2 are communicated with each other via the communication path 18 as described above is to maintain the traveling system running straight. That is, in order to maintain the straight traveling of the traveling system, the amount of pressure fluid supplied to both traveling motors must be equal. Therefore, the process of supplying the pressure fluid to both the traveling motors is communicated as described above so that the amount of pressure fluid supplied to both traveling motors is made equal.

  In order to maintain straight traveling as described above, for example, a control circuit described in Patent Document 1 is also known. The control circuit described in Patent Document 1 is provided with a communication valve between a pair of travel motor connection passages. This communication valve normally connects both the travel motor connecting passages via a throttle so as to maintain a straight travel of the travel system. And when the load of any one traveling motor becomes large, it is set as the structure which a communication valve detects the load and interrupts | blocks communication of both traveling motor connection passages.

As described above, the load of one traveling motor becomes large, for example, when one traveling motor side gets over an obstacle on the road surface. In such a situation, the load of the other travel motor that is not related to the obstacle becomes relatively light. Therefore, when the travel motor connection passages are left in communication, most of the pressure fluid flows to the light travel motor side. It will flow and pressure fluid will not be supplied to the traveling motor side which is going to get over the obstacle. Therefore, when the load pressure balance between the two traveling motors is lost as described above, the communication of the traveling motor connection passage is blocked.
JP 2005-76237 A

  In the conventional control circuit shown in FIGS. 2 and 3, the outflow ports 11 of the first and second control valves V1 and V2 are always in communication with each other via the communication path 18 in order to maintain straight traveling. In order to make the traveling system bend, for example, when the second control valve V2 is kept in the neutral position and only the first control valve V1 is to be switched, it is supplied to the outflow port 11 of the first control valve V1. A part of the pressure fluid is returned to the tank T via the communication path 18 and the second control valve V2. As described above, when the pressure fluid to be supplied to one of the traveling motors is returned to the tank T, although it is a part thereof, there is a problem that an operator who operates the operation lever is uncomfortable.

Moreover, in the control circuit described in Patent Document 1, when the load balance of the travel motor is lost, the communication valve is closed. Therefore, for example, in a state where the load balance of the traveling motor is lost, there is a problem that it is impossible to maintain straight traveling.
An object of the present invention is to provide a traveling system control circuit that reliably communicates the first and second control valves when traveling straight, and blocks the communication between them when not traveling straight.

The present invention includes a pair of travel motors, first and second control valves that control the travel motors and that include a centering spring and that switch according to the amount of operation of an operation lever of a pilot pressure control mechanism, The first and second pressure compensation valves are connected to the two control valves. The first and second control valves are connected to the traveling motor, a pump port connected to the pump mechanism, a tank port connected to the tank, and a process of guiding the pump port to the pressure compensation valve. An outflow port is provided, and a pair of inflow ports for guiding the pressure fluid that has passed through the pressure compensation valve to the actuator port.
Furthermore, when the first and second control valves are in the neutral position, the pump port and the pair of inflow ports are closed, both actuator ports and the outflow port are led to the tank port, and are in a switching position other than the neutral position The pump port and the outflow port are communicated, the inflow port is communicated with one of the actuator ports, and the other actuator port is communicated with the tank port, while the outflow port of the first and second control valves is Communicate through the communication path.

In the first aspect of the present invention, the on-off valve is provided with an on-off valve that closes the on-off passage at the normal position and opens the on-off passage at the switching position, and the on-off valve is provided with a spring for holding the neutral position In addition, a pilot chamber that exerts a pressure action against the spring force of the spring is provided, and a pilot pressure for switching the first and second control valves is introduced into the pilot chamber. The first and second control valves are characterized in that they are configured to switch from the normal position to the switching position with the pilot pressure when switching to the fully open position or a position close to the fully open position.
The second invention is characterized in that the on-off valve is provided with a throttle that opens when it is in the switching position.

According to the first invention, the on-off valve is configured to switch from the normal position to the switching position with the pilot pressure when the first and second control valves are switched to the fully open position or a position close to the fully open position. During straight running, that is, when the first and second control valves are switched to the fully open position or a position close to the fully open position, the on-off valve maintains the open position and maintains straight running.
In addition, when the first and second control valves are in a position other than the fully open position or a position close to the fully open position, the open / close valve maintains the closed position, so that the operator feels uncomfortable even when only one control valve is switched. Do not have.

In addition, since the on-off valve is switched by the action of the pilot pressure, the straight traveling state can be maintained even when the load balance of the traveling motor is lost.
According to the second aspect of the invention, since the communication path is communicated with the throttle provided in the on-off valve, the pressure fluid on the one traveling motor side does not flow much on the other traveling motor side.

The embodiment shown in FIG. 1 differs from the conventional example shown in FIGS. 2 and 3 only in the presence or absence of the on-off valve 20, and the configuration of the first and second control valves V1, V2 and the first and second pressure compensation valves. 9 and 10 are the same as in the prior art.
Therefore, the following description will focus on the on-off valve 20, omitting a detailed description of the first and second control valves V1 and V2 and the first and second pressure compensating valves 9 and 10, and regarding the same components as in the prior art. Are described with the same reference numerals.

  The on-off valve 20 is provided in the communication passage 18 and is provided with springs 21 and 22 at both ends thereof and pilot chambers 23 and 24. The pilot chambers 23 and 24 are always in communication with the pilot chambers 16 and 17 of the first and second control valves V1 and V2. Therefore, when pilot pressure is introduced into the pilot chambers 16 and 17 of the first and second control valves V1 and V2, the same pilot pressure is also introduced into the pilot chamber 23 or 24 of the on-off valve 20. .

However, the initial load of the springs 21 and 22 of the on-off valve 20 is larger than the initial load of the centering springs 14 and 15 of the first and second control valves V1 and V2. Therefore, when a relatively low pilot pressure is applied to the pilot chambers 16 and 17 of the first and second control valves V1 and V2 and the pilot chambers 23 and 24 of the on-off valve 20, the on-off valve 20 maintains the illustrated normal position. Only the first and second control valves V1 and V2 are switched.
When the pilot pressure increases until the first and second control valves V1, V2 are switched to the fully open position or a position close thereto, the on-off valve 20 is switched to the switching position by the pilot pressure at that time. When the on-off valve 20 is in the normal position, the on-off valve 20 is kept closed to block communication of the communication path 18. Further, when the on-off valve 20 is switched to the switching position, the open state is maintained and the communication path 18 is communicated through the throttle 25.

  Note that the initial loads of the centering springs 14 and 15 and the springs 21 and 22 are different from each other as described above in most cases when the traveling system is traveling straight ahead, the first and second control valves V1 and V2 are in the fully open position. Alternatively, it is normal to switch to a position close to it and run at full speed. In other words, the on-off valve 20 maintains the switching position only when traveling at full speed and allows the communication path 18 to communicate.

According to the embodiment as described above, when the vehicle is not traveling straight ahead, the on-off valve 20 maintains the closed position and blocks communication of the communication path 18. Therefore, for example, when the vehicle travels while the second control valve V2 is kept in the neutral position and only the first control valve V1 is switched, the pressure fluid of the pump mechanism P returns to the tank T via the second control valve V2. It will not be. In other words, since the entire amount of the controlled pressure fluid is supplied to the traveling motor, the operator does not feel uncomfortable with the operation.
Further, at the time of turning as described above, even if the load balance between both the traveling motors is lost, the on-off valve 20 is not switched.

During straight running, if the pilot pressure is increased by almost full stroke of the operating lever to switch the first and second control valves V1, V2 to the fully open position or a position close thereto, the pilot pressure at that time causes The on-off valve 20 is switched to the switching position to maintain the open state, and the communication path 20 is communicated.
Therefore, the flow rates of the pressure fluid supplied to both the traveling motors are also equal, and the traveling system can reliably maintain the straight traveling state.

  In the above embodiment, the initial loads of the springs 21 and 22 of the on-off valve 20 are made larger than the initial loads of the centering springs 14 and 15 of the first and second control valves V1 and V2, but these initial loads are equal. Then, the pressure receiving areas in the pilot chambers 23 and 24 of the on-off valve 20 may be relatively smaller than the pressure receiving areas in the pilot chambers 16 and 17 of the first and second control valves V1 and V2. In any case, if the on-off valve 20 is switched to the switching position only when the first and second control valves V1, V2 are largely switched during straight running, the spring force of the springs 21, 22 is increased, or Either of the pressure receiving areas in the pilot chambers 23 and 24 may be reduced.

It is a circuit diagram of a traveling system. It is a circuit diagram of the conventional traveling system. It is an enlarged view of the symbol of a 1st, 2 control valve.

Explanation of symbols

V1, V2 First and second control valves 5, 6 Actuator port P Pump mechanism 7 Pump port 8 Tank port T Tank 9, 10 First and second pressure compensation valve 11 Outflow port 12, 13 Inflow port 14, 15 Centering spring 18 station Passage 20 On-off valve 21, 22 Spring 23, 24 Pilot chamber 25 Restriction

Claims (2)

  A pair of travel motors, a first and a second control valve that control these travel motors and that have a centering spring and switch according to the amount of operation of the operation lever of the pilot pressure control mechanism; A first and second pressure compensation valve connected, the first and second control valves are a pair of actuator ports connected to the travel motor, a pump port connected to the pump mechanism, a tank port connected to the tank, An outflow port provided in the process of guiding the pump port to the pressure compensation valve, and a pair of inflow ports for guiding the pressure fluid via the pressure compensation valve to the actuator port, wherein the first and second control valves have a neutral position. When holding, close the pump port and the pair of inflow ports, lead both actuator ports and the above outflow port to the tank port, other than the neutral position When in the switching position, the pump port and the outflow port communicate with each other, the inflow port communicates with one of the actuator ports, and the other actuator port communicates with the tank port, while the first and second controls In the control circuit of the traveling system in which the outflow port of the valve is communicated via the communication path, the communication path is provided with an opening / closing valve that closes the communication path at the normal position and opens the communication path at the switching position. The valve is provided with a spring for maintaining a neutral position, and a pilot chamber that exerts a pressure action against the spring force of the spring is provided. In this pilot chamber, a pilot for switching the first and second control valves is provided. This open / close valve switches the first and second control valves to the fully open position or a position close to the fully open position. Pilot pressure, the traveling system of the control circuits to the configuration switches from the normal position to the switching position of the time.   2. The travel system control circuit according to claim 1, wherein the on-off valve is provided with a throttle that opens when it is in a switching position.

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