JP2010196781A - Hydraulic control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control system which supplies a constant control flowing capacity to a steering system circuit when steering is operated, and a surplus flowing capacity to a working machine system circuit while minimizing pressure loss when the steering is not operated. <P>SOLUTION: As shown in Fig.1, a spring 12 extended/contacted by a control piston 14 is provided in one side of a flowing rate control valve CV; when a steering wheel 6 is not operated, its pressure loss is minimized with respect to a flow led to a working machine system flowing channel 20 by keeping a length of the spring 12 roughly free; and when the steering wheel 6 is operated, the surplus flowing capacity is led to a working machine system circuit W by leading the constant control flowing capacity to a steering system circuit S by bending the spring 12 with the control piston 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic control system used for, for example, a work machine having a steering mechanism.

  As this type, a hydraulic control system disclosed in Patent Document 1 is conventionally known. In this conventional hydraulic control system, a flow control valve is connected to a steering system circuit and a work machine system circuit. The flow control valve is provided with a spring (not shown) in one of the pilot chambers, and the differential pressure before and after the control orifice provided in the process of communicating with the steering system circuit is equal to the spring force of the spring. In this way, a constant control flow rate is supplied to the steering circuit system, and an excessive flow rate other than the control flow rate is supplied to the work machine system circuit.

JP 2004-352466 A

In the conventional hydraulic control system as described above, even when the steering operation is not performed and the actuator of the work machine system circuit is not used, at least a constant control flow rate is supplied to the steering system circuit. There was a problem that became larger.
The object of the present invention is to unload the hydraulic oil from the main pump by causing the flow control valve to exhibit an unload function when the steering system is not operated and the work machine system actuator is not used. It is to provide a hydraulic control system with reduced energy loss.

  The present invention relates to a main pump, a flow control valve having an inflow port connected to the main pump, a steering system circuit connected to the control flow port of the flow control valve, and a work machine connected to the surplus flow port of the flow control valve. The flow control valve is provided with a pair of pilot chambers. Then, the pressure downstream of the control orifice provided in the communication process between the steering system circuit or the control flow port and the steering system circuit is guided to one pilot chamber, and the upstream of the control orifice is supplied to the other pilot chamber. I try to guide the pressure on the side. In addition, a spring is provided in the one pilot chamber. The flow control valve configured as described above controls the differential pressure across the control orifice to be equal to the spring force of the spring, preferentially leads a constant control flow rate to the steering system circuit, and supplies the surplus flow rate to the working machine. I try to guide it to the system circuit.

  Furthermore, the present invention provides a sub-pump, a control piston for controlling the spring force of the spring of the flow rate control valve, a pilot passage for connecting the control piston and the sub-pump, a pilot passage provided in the pilot passage and a steering system circuit. A switching valve that switches in accordance with either one of the operation signal or the operation signal of the work machine system circuit, and the flow control valve has a first position that communicates the inflow port and the control flow port; There is a second position where the inflow port and the surplus flow port communicate with each other, and a third position where the inflow port communicates with the unload port. When the switching valve is in the normal position, the pressure acting on the control piston is set to the tank pressure and the spring force of the spring is minimized to keep the flow control valve at the third position, while the steering operation signal or work When the switching valve is switched according to one of the operation signals of the mechanical circuit, the pressure of the sub pump is applied to the control piston of the flow control valve and the spring force of the spring is increased to The control valve is balanced between the first position and the second position, and a constant control flow rate from the control flow port is guided to the steering system circuit, while an excessive flow rate from the surplus flow port is guided to the work machine system circuit. ing.

When the steering operation is not performed and when the actuator of the work machine system circuit is not operated, the flow rate control valve functions as an unload valve, so that energy loss can be minimized.
In addition, since the flow control valve has an unloading function as described above, it is not necessary to provide an unloading valve, and the overall cost can be reduced accordingly.

It is a circuit diagram of a 1st embodiment. It is a circuit diagram of a 2nd embodiment. It is a circuit diagram of a 3rd embodiment.

The first embodiment shown in FIG. 1 is a hydraulic control system applied to a forklift, in which a main pump MP and a sub pump SP are linked to an engine E. Therefore, when the engine E is driven, the main pump MP and the sub pump SP rotate accordingly.
Note that the sub-pump SP in this embodiment is for supplying pressure oil to a brake system or the like (not shown).

  The main pump MP is connected to the inflow port 2 of the flow rate control valve CV via the main flow path 1, and this flow rate control valve CV has a first position (a ), A second position (b) where the inflow port 2 communicates with the surplus flow port 4, and a third position (c) where the inflow port 2 communicates with the unload port 5.

The control flow port 3 as described above is connected to the steering system circuit S, the surplus flow port 4 is connected to the work machine system circuit W, and the unload port 5 is connected to the tank T.
The steering system circuit S includes a metering unit 7 that controls the amount of oil in proportion to the rotational speed of the steering wheel 6, and a rotary valve 8. The rotary valve 8 includes a control orifice 9.
The control flow port 3 of the flow rate control valve CV communicates with the port 8a of the rotary valve 8 via the flow path r. The port 8a is closed when the steering is not operated.

  The flow rate control valve CV has one pilot chamber 10 connected to the downstream side of the control orifice 9 and the other pilot chamber 11 connected to the upstream side of the control orifice 9. Further, a spring 12 is provided in the one pilot chamber 10, and a control piston 14 provided in the piston chamber 13 is linked to the spring 12. When no pressure is applied to the piston chamber 13, the spring 12 maintains a substantially free length so that its spring force becomes almost zero. When pressure is applied to the piston chamber 13, the spring 12 is deflected by the thrust of the control piston 14 to exert a predetermined spring force.

  When the spring 12 is deflected and exerts a predetermined spring force as described above, the flow control valve CV balances between the first position (a) and the second position (b), and the control orifice The control flow rate is controlled to be constant so that the differential pressure around 9 is equal to the spring force of the spring 12. Then, the surplus flow rate equal to or higher than the control flow rate is supplied from the surplus flow port 4 to the work machine system circuit W.

Further, when the spring 12 maintains a free length, the steering system circuit S is not operated, and the downstream side of the supply flow path r is closed by the port 8a of the rotary valve 8. Accordingly, the switching pressure of the spool of the flow control valve CV acts on the pilot chamber 11.
When pressure is applied to the pilot chamber 11, since the spring 12 maintains the free length as described above, the flow control valve CV is switched to the third position (c), and almost the entire discharge amount of the main pump MP. Is unloaded from the unload port 5.
When the flow control valve CV is in the third position (c), the unload port 5 is kept fully open, but the control flow port 3 is slightly opened so as to keep the pressure in the other pilot chamber 11. I have to.

On the other hand, the work machine system circuit W has a switching control valve 16 for controlling the lift cylinder 15 from the upstream side, a switching control valve 18 for controlling the tilt cylinder 17, and a switching control valve 19 for controlling an attachment actuator (not shown). Is provided.
These switching control valves 16, 18, 19 are configured to guide the work machine system flow path 20 connected to the work machine system circuit W from the surplus flow port 4 to the tank T when in the illustrated neutral position.

  The sub-pump SP is connected to the piston chamber 13 of the flow rate control valve CV via the pilot flow path 21 and the switching valve 22, and the switching valve 22 is provided with a solenoid 23 on one side thereof and the solenoid. The spring force of the spring 24 is applied to the opposite end opposite to the head 23. Therefore, if the solenoid 23 is in a non-excited state, the switching valve 22 maintains the normal position shown in the figure by the action of the spring 24. When the solenoid 23 is energized, the switching valve 22 switches to the switching position on the right side of the drawing against the spring force of the spring 24.

  When the switching valve 22 is in the illustrated normal position, the piston chamber 13 is communicated with the tank T, and the spring 12 of the flow control valve CV is kept free. When the switching valve 22 is in the switching position, the piston chamber 13 and the sub pump SP are communicated with each other via the pilot flow path 21. When the pressure of the sub pump SP is guided to the piston chamber 13, the spring 12 is bent by the thrust of the piston 14.

Further, the solenoid 23 of the switching valve 22 is connected to a sensor 25 that electrically detects the operation of the steering wheel 6 and a piezoelectric transducer 26 that converts pressure into an electrical signal.
When the sensor 25 outputs an electrical signal that is a steering operation signal, the solenoid 23 is excited. The piezoelectric transducer 26 detects the pressure in the branch path 21a branched from the pilot flow path 21. When the piezoelectric converter 26 detects the pressure in the pilot flow path 21, an electrical signal is output. The solenoid 23 is excited.

  Further, the branch passage 21a that communicates with the pilot passage 21 communicates with the tank T via the switching control valves 16, 18, and 19 when the switching control valves 16, 18, and 19 are in the illustrated neutral positions. At the same time, the switching control valve 16 is switched to the lift position on the right side of the drawing, or the switching control valves 18 and 19 are switched from the neutral position to the switching position, thereby blocking the communication between the pilot flow path 21 and the tank T. Yes.

Reference numeral 27 in the figure denotes a throttle provided in the branch passage 21a. The throttle control 27 is also provided when the switching control valves 16, 18, 19 are kept in the neutral position and the branch passage 21a is communicated with the tank T. This is to maintain the upstream pressure.
Reference numeral 28 is a damper orifice, 29 is a check valve that functions when pressure is released from the other pilot chamber 11, and 30 is a relief valve.

Further, a safety valve 31 is connected to the downstream side of the throttle 27 of the branch path 21a. When the safety valve 31 maintains the illustrated normal position by the action of the spring force of the spring 32, the safety path 31 is connected to the branch path 21a. Communicate with the tank T. A solenoid 33 is provided on the side opposite to the spring 32. When the solenoid 33 is excited, the safety valve 31 is switched to the closed position against the spring force of the spring 32, and the branch path 21a. The communication with the tank T is cut off. The solenoid 33 is connected to a seat switch of a driver's seat (not shown). When the operator is not seated on the driver's seat, the solenoid 33 is kept in a non-excited state to keep the safety valve 31 in the normal position. Therefore, even if the operator operates the switching valve 16, 18 or 19 without sitting on the driver's seat, the lift cylinder 15, the tilt cylinder 17 or the actuator for attachment does not operate, and safety is maintained.
If the operator is seated in the driver's seat, the solenoid 33 is excited to cut off the communication between the branch path 21a and the tank T, so that the actuators can be operated.

Next, the operation of the first embodiment will be described.
If the operator is not seated in the driver's seat now, the safety valve 31 is in the illustrated normal position and the branch path 21a communicates with the tank T, so the pressure downstream of the throttle 27 becomes the tank pressure. If the pressure on the downstream side of the throttle 27 becomes the tank pressure, the piezoelectric transducer 26 does not operate, so that the solenoid 23 does not operate with a signal from the piezoelectric transducer 26.
Therefore, the switching valve 22 is not switched as long as the safety valve 31 maintains the normal position without the operator sitting in the driver's seat.
Further, when the operator operates the steering wheel 6 without sitting in the driver's seat, the steering operation can be performed as usual, so that safety is maintained.

If the switching valve 22 is not switched and maintains the normal position as described above, the piston chamber 13 of the flow rate control valve CV communicates with the tank T, so that the spring 12 maintains the free length.
Accordingly, as described above, almost all of the discharge oil of the main pump MP is unloaded from the unload port 5.

  Further, when the operator is seated in the driver's seat and the safety valve 31 is switched to the closed position, the switching control valve 16 is switched to the lift position on the right side of the drawing or any one of the switching control valves 18 and 19 is switched. Then, the communication between the branch path 21a and the tank T is blocked, and a pilot pressure is generated downstream of the throttle 27. Since this pilot pressure acts on the piezoelectric transducer 26, the piezoelectric transducer 26 excites the solenoid 23 and switches the switching valve 22 to the switching position.

When the switching valve 22 is switched to the switching position, the pressure on the upstream side of the throttle 27, that is, the discharge pressure of the sub pump SP is guided to the piston chamber 13 of the flow control valve CV. Therefore, the control piston 14 moves to deflect the spring 12, and the unload function of the flow control valve CV is stopped.
Thus, the flow control valve CV whose unload function is stopped balances between the first position (a) and the second position (b), and a constant control flow rate is supplied from the control flow port 3 to the steering system circuit S. The surplus flow rate is supplied from the surplus flow port 4 to the work machine system circuit W.

  Furthermore, regardless of the operation of the switching control valves 16, 18, 19, if the steering wheel 6 is operated, the sensor 25 detects that, and the solenoid 23 of the switching valve 22 is detected by the steering operation signal output from the sensor 25. Is switched, the switching valve 22 is switched to the switching position, and the unload function of the flow control valve CV is stopped. Accordingly, as described above, the flow control valve CV balances between the first position (a) and the second position (b) and supplies a constant control flow rate from the control flow port 3 to the steering system circuit S. Then, the surplus flow rate is supplied from the surplus flow port 4 to the work machine system circuit W.

  In any case, in the first embodiment, the flow control valve CV is in the third position (c) as long as the steering operation is not performed and the switching control valves 16, 18, and 19 are kept in the neutral position. Since the unloading function is exhibited, the load on the main pump MP can be reduced and the energy loss can be minimized.

  The second embodiment shown in FIG. 2 includes a main pump MP and a sub pump SP, and connects the main pump MP to the inflow port 2 of the flow control valve CV via the main flow path 1. The main pump MP, sub pump SP, and flow control valve CV are exactly the same as in the first embodiment. Moreover, it is the same as that of 1st Embodiment that the switching valve 22 provided with the solenoid 23 and the spring 24 is connected to the piston chamber 13 of the flow control valve CV. And the sensor 25 is provided in the steering system circuit S, and the point which has connected this sensor 25 to the said solenoid 23 is the same as that of 1st Embodiment.

  In the second embodiment, the point at which the safety valve 31 is connected to the work machine system flow path 20 and the switching operation of the switching control valves 16, 18, 19 are electrically detected, and the electrical signal is switched to the switching valve 22. This is different from the first embodiment in that it is input to the solenoid 23.

In order to electrically detect the switching operation of the switching control valves 16, 18 and 19 as described above, in the second embodiment, a controller C is connected to the solenoid 23 provided in the switching valve 22.
The controller C is connected to each of limit switches 34 to 36 provided on the switching control valves 16, 18, and 19. These limit switches 34 to 36 are kept off when the switching control valves 16, 18, and 19 are kept in the neutral position, and the switching control valves 16, 18, and 19 are switched from the neutral position to the switching position. Sometimes it is turned on in relation to it.
When the switching control valve 16 for controlling the lift cylinder 15 is switched to the left side of the drawing in order to lower the lift cylinder 15, the limit switch 34 is kept off.

As described above, when each of the switching control valves 16, 18, 19 is in the neutral position and the limit switches 34 to 36 are off, the controller C does not output a signal to the solenoid 23 of the switching valve 22. Therefore, the switching valve 22 does not switch to the switching position by the signal from the controller C, but maintains the normal position.
It is the same as in the first embodiment that the flow control valve CV exhibits the unload function when the switching valve 22 holds the normal position.

  Further, the switch control valve 16 for controlling the lift cylinder 15 is switched to the lift position on the right side of the drawing, or any one of the switch control valves 18 and 19 is switched to turn on one of the limit switches 34 to 36. Then, the controller C excites the solenoid 23 by outputting an electric signal to the solenoid 23 of the switching valve 22. When the solenoid 23 is excited in this way, the switching valve 22 is switched to the switching position, and the discharge pressure of the sub pump SP is guided to the piston chamber 13 to bend the spring 12, but the flow rate control when the spring 12 is bent. The function of the valve CV is the same as in the first embodiment.

In the third embodiment shown in FIG. 3, the switching valve 22 is switched by the pilot pressure. That is, the switching valve 22 is provided with a pilot chamber 37 at the end opposite to the spring 24.
The pilot chamber 37 is connected to the downstream side of the control orifice 9 through the high pressure selection valve 38 in the same manner as the pilot chamber 10 of the flow control valve CV. Accordingly, when a load pressure is generated by operating the steering wheel 6, the pressure acts on the pilot chambers 10 and 37 as a steering operation signal. If the pressure acts on the pilot chamber 37 in this way, the switching valve 22 is switched from the normal position to the switching position.
Further, the high-pressure selection valve 38 is connected to the branch path 21a on the downstream side of the throttle 27, but the other configuration is the same as that of the first embodiment.

  Therefore, when the steering wheel 6 is operated or the switching control valves 16, 18, 19 are switched, the switching valve 22 is switched and the flow control valve CV supplies a constant control flow to the steering system circuit S. The surplus flow rate is supplied to the work machine system circuit W.

  When the hydraulic control system as described above is used for a forklift or the like, a great energy saving effect can be expected.

MP Main pump SP Sub pump CV Flow control valve 1 Main flow path 2 Inflow port 3 Control flow port 4 Surplus flow port S Steering system circuit W Work machine system circuit 9 Control orifice 10, 11 Pilot chamber 12 Spring 14 Control piston 16 Switching control valve 18 Switching control valve 19 Switching control valve 21 Pilot flow path 22 Switching valve

Claims (1)

  A main pump, a flow control valve having an inflow port connected to the main pump, a steering system circuit connected to a control flow port of the flow control valve, and a work machine system circuit connected to an excess flow port of the flow control valve. And the flow control valve is provided with a pair of pilot chambers, and one pilot chamber has a pressure downstream of a control orifice provided in the communication process between the steering system circuit or the control flow port and the steering system circuit. In the other pilot chamber, the pressure upstream of the control orifice is guided, and in addition, the one pilot chamber is provided with a spring, and the flow control valve has a differential pressure before and after the control orifice. By controlling to equal the spring force of the spring, a constant control flow rate is preferentially guided to the steering system circuit, and the surplus flow rate is supplied to the work equipment. In the hydraulic control system configured to lead to the circuit, the sub-pump, the control piston for controlling the spring force of the spring of the flow control valve, the pilot flow path for connecting the control piston and the sub-pump, and the pilot flow path are provided. A switching valve that switches in response to either the steering operation signal of the steering system circuit or the operation signal of the work machine system circuit, and the flow control valve communicates the inflow port with the control flow port. The control piston when the switching valve is in the normal position, the second position communicating the inflow port and the surplus flow port, and the third position communicating the inflow port to the unload port. The pressure acting on the tank is the tank pressure and the spring force of the spring is minimized to keep the flow control valve in the third position. On the other hand, when the switching valve is switched in accordance with either the steering operation signal or the operation signal of the work machine system circuit, the pressure of the sub pump is applied to the control piston of the flow control valve and the spring The spring force is increased, the flow control valve is balanced between the first position and the second position, and a constant control flow rate from the control flow port is guided to the steering system circuit, while the surplus flow rate from the surplus flow port is reduced. Hydraulic control system configured to lead to work machine system circuit.

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