JP3752350B2 - Hydraulic control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic control circuit that combines a control valve that is manually switched and a control valve that is switched by a pilot pressure.
[0002]
[Prior art]
In a hydraulic control circuit used for a work vehicle such as a snowplow, a hydraulic control circuit that combines a control valve that is manually switched and a control valve that is switched by a pilot pressure may be used because of cost and mounting.
In the hydraulic control circuit shown in FIG. 3 , the first to third control valves 1 to 3 that are switched by a manual lever and the fourth to eighth control valves 4 that are switched by a pilot pressure are connected to a pump P linked to the engine via a sequence valve 9. ~ 8 are connected.
[0003]
When all of these first to eighth control valves 1 to 8 are in the neutral position, the pump P communicates with the tank T via the neutral flow path 10.
The recirculation ports 11 to 18 of the first to eighth control valves 1 to 8 are connected to the tank passage 19, and the inflow ports 21 to 28 are connected to each other via the parallel feeder 20. When any one of the control valves 1 to 8 is switched, the neutral flow path 10 is closed and the pump discharge oil is supplied to the actuator via the parallel feeder 20.
[0004]
A pilot passage 29 is connected upstream of the sequence valve 9, and the hydraulic pressure reduced by the pressure reducing valve 30 is guided to the pilot chambers 31 to 35 of the fourth to eighth control valves 4 to 8 as pilot pressure. In the fourth to eighth control valves 4 to 8, the pilot pressure guided to the pilot chambers 31 to 35 is individually controlled by the solenoids 36 to 40 so as to act on the spools of the control valves 4 to 8. Yes.
A relief valve 41 is provided to determine the maximum discharge pressure of the pump P.
[0005]
Next, the operation of this hydraulic control circuit will be described.
When all the control valves 1 to 8 are in the neutral position, the pump P is communicated with the tank T through the neutral flow path 10.
However, when pressure is generated on the upstream side of the sequence valve 9, a pilot pressure that causes the fourth to eighth control valves 4 to 8 to perform a full stroke by the pressure reducing valve 30 is generated in the pilot passage 29. Therefore, for example, when any one of the fourth to eighth control valves 4 to 8 is to be switched, pilot pressure enough to make a full stroke has already been generated, and this is individually controlled by the solenoids 36 to 40. These fourth to eighth control valves 4 to 8 can be switched by acting on the spool.
[0006]
In the hydraulic control circuit shown in FIG. 4 , an unload valve 42 is connected to the pump P.
The unloading valve 42 is normally by a spring 43, which maintains the open position shown in FIG.
When the solenoids 36 to 40 of any of the fourth to eighth control valves 4 to 8 are energized, the solenoid 44 is also energized at the same time to switch to the closed position. Further, sensors 45 to 47 for detecting the switching of the first to third control valves 1 to 3 are provided, and when the first to third control valves 1 to 3 are to be switched, the solenoid 44 is energized and closed. The position is switched.
Incidentally, other configurations are the same as the hydraulic control circuit shown in FIG. 3, a detailed description thereof is omitted.
[0007]
Next, the operation of this hydraulic control circuit will be described.
When all the control valves 1 to 8 are in the neutral position, the pump discharge oil is returned to the tank T via the unload valve 42. Accordingly, at this time, no pressure is generated on the upstream side of the sequence valve 9, and no pilot pressure is generated in the pilot passage 29.
When one of the control valves 1 to 8 is to be switched, the solenoid 44 is energized as described above, and the unload valve 42 is switched to the closed position. Therefore, pump discharge oil can be supplied to the actuator side, pressure is generated on the upstream side of the sequence valve 9, and the fourth to eighth control valves 4 to 8 can be fully stroked in the pilot passage 29 by the pressure reducing valve 30. Pilot pressure can be generated.
[0008]
[Problems to be solved by the invention]
In the hydraulic control circuit shown in FIG. 3 , even when all the control valves 1 to 8 are in the neutral position, the pilot pressure is always sufficient to cause the pilot passage 29 to fully stroke the fourth to eighth control valves 4 to 8. Is generated. For this reason, even when the actuator is not operated, the pump P consumes energy for generating the pilot pressure, causing an energy loss and raising the oil temperature.
[0009]
In the hydraulic control circuit shown in FIG. 4 , since the unload valve 42 is provided, the above problem can be solved. However, when the first to third control valves 1 to 3 are switched, the unload valve 42 is closed. It is necessary to switch to the position. Therefore, the sensors 45 to 47 must be provided for the first to third control valves 1 to 3, respectively, which increases the cost. In addition, since these sensors 45 to 47 are attached to a work vehicle that generates vibrations, there is a problem in their reliability.
An object of the present invention is to provide a hydraulic control circuit that does not cause energy loss and that does not require a sensor to be manually switched.
[0010]
[Means for Solving the Problems]
The present invention relates to a hydraulic control circuit, and includes a pump, a flow dividing valve that supplies a part of the pump discharge oil to the first port side, and a flow rate other than that to the second port side, A plurality of control valves connected in parallel to the second port, a neutral flow path communicating the second port of the diversion valve with the tank when these control valves are in the neutral position, and a first port of the diversion valve communicating with the tank The relief valve connected to the downstream side of the first port, the pilot passage connected to the upstream side of the flow dividing valve via the pressure reducing valve, and a number of control valves. And a solenoid for controlling the pilot pressure in the pilot passage to switch the remaining one of the control valves. The unload valve normally communicates the first port of the flow dividing valve with the tank. It is, above When energized solenoid, while blocking the first port of the diverter valve from the tank, when the first port and the tank flow dividing valve is shut off, the oil flowing out from the first port to bypass the unloading valve, It is characterized in that it flows out to the tank via a relief valve .
[0011]
Delete [0012]
DETAILED DESCRIPTION OF THE INVENTION
In the hydraulic control circuit of the embodiment shown in FIG. 1, a diversion valve 48 is connected to the pump P. The diversion valve 48 always supplies a part of the flow rate of the pump discharge oil to the first port 49 side, and supplies the other flow rate from the second port 50 to the first to eighth control valves 1-8. is there.
[0013]
[0014]
[0015]
[0016]
[0017]
[0018]
In the hydraulic control circuit of this embodiment, the pilot passage 29 is connected to the upstream side of the flow dividing valve 48, and the hydraulic pressure reduced by the pressure reducing valve 30 is used as the pilot pressure for the pilot chambers of the fourth to eighth control valves 4-8. 31-35.
Further, the first port 49 of the diverter valve connects the relief valve 51 in series on the downstream side of the unload valve 42. The flow path changing valve 52 is connected in parallel with the unload valve 42.
[0019]
The flow path changing valve 52 normally closes the inflow port 54 with a spring 53 and connects a passage 55 connected to the downstream side of the unload valve 42 and the upstream side of the relief valve 51 to the tank passage 19. ing.
From this state, when the unload valve 42 is in the closed position, the pressure on the upstream side of the flow path changing valve 52 is increased and switched, and the inflow port 54 is communicated with the passage 55. The position of the flow rate change valve 52 is determined so that the upstream pressure and the downstream pressure maintain a pressure difference corresponding to the initial load of the spring 53.
[0020]
Next, the operation of the hydraulic control circuit of this embodiment will be described.
When all the control valves 1 to 8 are in the neutral position, the unload valve 42 is in the open position shown in FIG. 2, so that the pump discharge oil has a partial flow rate of the first port 49 → the unload valve 42. In addition, the other flow rate is returned to the tank via the second port 50 → the neutral flow path 10. Accordingly, at this time, no pilot pressure is generated in the pilot passage 29.
[0021]
From this state, for example, when the first to third control valves 1 to 3 are switched, the unload valve 42 remains open.
However, since a part of the flow rate is only supplied from the shunt valve 48 to the first port 49 side, the other flow rates are supplied to the first to eighth control valves 1 to 8. Therefore, if the first to third control valves 1 to 3 are switched, the pump discharge oil can be supplied to the actuator side to operate the actuator.
In this case, since pressure is generated on the upstream side of the diversion valve 48, the pressure is reduced by the pressure reducing valve 30, and pilot pressure is generated in the pilot passage 29. However, since the pilot pressure is generated using the pressure generated to operate the actuator, no energy loss occurs in the pump P.
[0022]
When the solenoids 36 to 40 are energized to switch the fourth to eighth control valves 4 to 8, the solenoid 44 is energized at the same time, and the unload valve 42 is switched to the closed position. When the unload valve 42 is switched to the closed position, the pressure on the upstream side of the flow path changing valve 52 increases, and the flow path changing valve 52 is switched as described above. As a result, the oil flowing out from the first port 49 of the diverter valve 48 bypasses the unload valve 42 and flows to the tank via the relief valve 51.
Therefore, a pressure determined by the relief valve 51 is generated on the downstream side of the diversion valve 48, and the pressure is increased on the upstream side of the diversion valve 48 corresponding to the pressure determined by the relief valve 51. . The pressure reducing valve 30 reduces the pressure to generate a pilot pressure in the pilot passage 29. And if this pilot pressure is individually controlled by the solenoids 36 to 40, the fourth to eighth control valves 4 to 8 can be switched.
[0023]
The hydraulic control circuit of this embodiment can eliminate the energy loss, also, there is no need to provide a sensor in each of the first to third control valve 1-3, ensuring the reliability of the hydraulic control circuit Can do .
In the hydraulic control circuit of the above embodiment, the pilot passage 29 may be connected to the downstream side of the first port 49 of the flow dividing valve 48. At this time, the pilot passage 29 is connected to the upstream side of the relief valve 51, for example, the passage 55 and the like.
[0024]
In the above embodiment, the unload valve 42 is in the open position by the spring 43 at the normal time. However, the solenoid 44 may be in the open position by keeping the solenoid 44 energized at the normal time. When the solenoids 36 to 40 are energized, the energization of the solenoid 44 may be stopped and the unload valve 42 may be switched to the closed position by the spring 43.
Further, as the unloading valve, as shown in FIG. 2, it may be used three-port valve 56. However, normally, the first port 49 is communicated with the tank T, and when the solenoids 36 to 40 are energized, the first port 49 is communicated with the relief valve 51 in the same manner as the unload valve 42. .
[0025]
【The invention's effect】
According to the present invention, since the pump does not consume energy for generating the pilot pressure, no energy loss occurs and the oil temperature does not rise. Further, it is not necessary to provide a sensor on the control valve that is switched by the manual switching means, so that the cost is not increased. In addition, reliability as a hydraulic control circuit can be ensured.
[Brief description of the drawings]
1 is a diagram showing a hydraulic control circuit of the embodiment.
FIG. 2 is a diagram illustrating a circuit using a three-port valve as an unload valve in the hydraulic control circuit according to the embodiment.
FIG. 3 is a diagram illustrating a conventional hydraulic control circuit.
FIG. 4 is a diagram showing another conventional hydraulic control circuit.
[Explanation of symbols]
1-8 Control valve 10 Neutral flow path 20 Parallel feeder 29 Pilot passage 30 Pressure reducing valve 31-35 Pilot chamber 36-40 Solenoid 42 Unload valve 48 Diverging valve 49 1st port 50 2nd port 51 Relief valve

Claims (1)

A pump, a flow dividing valve for supplying a part of the pump discharge oil to the first port side, and a flow dividing valve for supplying the other flow rate to the second port side, and a plurality of parallel connections to the second port of the flow dividing valve When the control valves are in the neutral position, the neutral flow path that connects the second port of the flow dividing valve to the tank, and the first flow port of the flow dividing valve that communicates with the tank or shuts off from the tank. A load valve; a relief valve connected to the downstream side of the first port; a pilot passage connected to the upstream side of the shunt valve via a pressure reducing valve ; a manual switching means for switching some of the control valves; and a pilot passage by controlling the pilot pressure, and a solenoid for switching the remaining ones of the control valve, the unloading valve is normally allowed to communicate with the first port of the diverter valve to the tank, when energized to the solenoid, the shunt While blocking the first port from the tank, when the first port and the tank flow dividing valve is shut off, the oil flowing out from the first port to bypass the unloading valve, the outflow through the relief valve to the tank A hydraulic control circuit characterized by being configured to perform.

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