JPH0640970Y2 - Valve device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a switching valve operated by pilot pressure, and particularly relates to prevention of shock during return operation of the switching valve and heat-up function of pilot passage. It is a thing.

[Prior Art] FIGS. 5 (a) and 5 (b) show a shock-prevention pilot hydraulic circuit of the prior art, which includes a pilot valve 31 and a switching valve 12.
A shock prevention valve 34 is arranged in a pilot passage communicating with the pilot oil chamber. This shockproof valve 34
Is a pressure-compensated flow control valve with an opening / closing function and a check valve configured in parallel, and when operating the switching valve 12, the pilot pressure generated in the pilot valve 31 is directed toward the pilot oil chamber of the switching valve 12. It flows through the pilot passage, operates the open / close spool of the flow control valve to close the passage, and passes through the check valve in the free flow direction to act on the pilot oil chamber of the switching valve 12. When the pilot valve 31 is returned to neutral, the switching valve 12 is returned to neutral by the spring 13, but at this time, the pilot passage is blocked in the closing direction of the check valve side passage of the shock prevention valve 34, and
The flow control valve returns the open / close spool by a spring to form an open passage, and the return speed of the switching valve is regulated by the throttle provided in the flow control valve, and the hydraulic actuator (not shown) connected to the switching valve 12 is stopped. It has a mechanism that can prevent the shock at the time. However, this mechanism can prevent shock, but the pilot valve
The pressure oil flowing through the pilot passage by the operation of 31 is a small amount corresponding to the stroke amount of the spool of the switching valve 12, and even if the pilot valve 31 is repeatedly operated, the pilot oil chamber of the switching valve 12 And the pressure oil contained in the pilot passage only reciprocates by repeating pressurization and depressurization, so pilot valve 31 and switching valve 12
When the pilot passage that connects the pilot oil chamber is long, the oil temperature in the pilot passage does not rise, and especially in cold regions, the viscous resistance of the oil in the pilot passage increases due to the influence of the outside temperature, and the spool of the switching valve 12 Movement becomes slow and the response is likely to be delayed.

Further, in the configuration of the switching valve disclosed in JP-A-62-2004 and JP-A-62-24080, when the spool of the pilot switching valve is pushed by the pilot pressure from one side, the spool is opposed to the spool of the pilot switching valve. Side pilot oil chamber is provided with a flow passage that connects the drain oil passage of the switching valve, and a throttle hole is provided that always connects the pilot oil chamber and the drain oil passage of the switching valve,
It accelerates the oil outflow from the pilot oil chamber, circulates oil in the pilot oil passage to raise the oil temperature, and reduces the viscous resistance of the oil. It prevents the occurrence of a response delay even when it is easy to increase, but it does not have a shock prevention function.

Further, the valve device of Japanese Utility Model Laid-Open No. 63-42904 is a valve device provided with a pressure compensating flow control valve for adjusting the switching speed of a pilot type switching valve, and includes a relief valve and a pressure compensating flow control valve. Is provided in one block, and a path for transmitting heat generated by the relief valve is provided in the block to have a heat retaining effect.

[Problems to be solved by the invention] In recent years, the combined control valve for civil engineering and construction work machines has rapidly changed from conventional manual operation to pilot operation method because of its light operability and free installation position of the combined control valve. Came. However, contrary to the above advantages, it has become indispensable to prevent shocks when the switching valve is stopped and to prevent the pilot passage from heating up in cold regions. There is also a method of delaying the return speed of the switching valve by providing a throttle in the pilot passage for shock prevention, but it has not been put to practical use because it becomes too resistive at a low temperature and a response delay occurs.

Further, although the conventional technique described in FIG. 5 has an effect of preventing a shock, it has no effect of heating up the pilot passage in a cold region.

Further, as described in the above-mentioned prior art, JP-A-62-2004
In the switching valve of Japanese Patent Laid-Open No. 62-24080 and Japanese Patent Laid-Open No. 62-24080, there is an effect of increasing the oil temperature in the pilot oil passage, reducing the viscous resistance of the oil, and eliminating the response delay in cold regions. No protection is provided.

Further, the valve device disclosed in Japanese Utility Model Laid-Open No. Sho 63-42904 has a heat retaining effect on a part of the pilot conduit due to the heat generated by the relief valve, and does not heat up the entire pilot conduit. Absent.

Therefore, an object of the present invention is to have both a shock-preventing effect when the switching valve is stopped and a pilot passage heat-up effect, and has both functions with almost the same component configuration as the valve device having the conventional shock-preventing effect. It is to provide a valve device.

[Means for Solving the Problems] In a valve device including a flow control valve with pressure compensation for adjusting the return speed of a pilot type switching valve, a pilot passage between a pilot oil chamber of the pilot type switching valve and a pilot valve. Is provided with a valve for closing or limiting return oil from the pilot oil chamber, and the flow control valve with pressure compensation is provided in a tank passage branching from the pilot passage between the valve and the pilot oil chamber and communicating with the tank. Is provided and the discharged oil that has passed through the flow control valve with pressure compensation is discharged to the tank.

[Operation] When operating the pilot type switching valve, the pilot passage from the pilot valve to the pilot oil chamber of the switching valve becomes free flow and the switching valve is operated by the pilot pressure for switching valve control generated by the pilot valve, and the pilot valve is operated at the same time. The oil supplied from the valve branches from the pilot passage, passes through the flow control valve with pressure compensation, is discharged to the tank, and is circulated, so that the pilot passage is heated.

When the switching valve returns to the neutral position, the flow of return oil from the pilot oil chamber is blocked or limited by the closing valve, and the flow control valve with pressure compensation that branches from the pilot passage between the closing valve and the pilot oil chamber. Since it is gradually discharged after passing through, the switching valve does not suddenly return, and a shock when the hydraulic actuator connected to the switching valve is stopped is prevented.

[Embodiment] FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.
This will be described.

In the figure, a constant pilot source pressure is guided to the pilot valve 11 by the pilot pump 15 and the relief valve 16, and the control pressure oil generated by the pilot valve 11 passes in the free flow direction of the check valve 17 provided in the pilot passage 20. Reach the pilot oil chamber 18 of the switching valve 12 and switch valve
12 is operated. On the other hand, a flow path control valve 19 with pressure compensation is arranged in a tank passage that branches from a pilot passage 21 between the check valve 17 and the pilot oil chamber 18 of the switching valve 12 and communicates with the tank, and this discharged oil is returned to the tank. Be done. Therefore, the oil supplied from the pilot valve 11 acts on the pilot oil chamber 18 of the switching valve 12 and at the same time branches from the pilot passage 20 and returns to the tank through the flow control valve 19 with pressure compensation, and the tank → pump 15 → Since the circulation to the pilot valve 11 is repeated, the pilot passage 20 is heated up. Since the pilot passage 21 has no heat-up effect due to this circulating oil, the pilot oil chamber 18 and the valve device are practically used.
It is desirable that the pilot passage 21 between 22 be as short as possible and close to zero. Further, the oil supplied from the pilot valve 11 for operating the switching valve 12 is supplied to the pilot passage 20.
The amount of oil that is branched off from and discharged from the flow control valve with pressure compensation 19 is the amount of oil that is regulated to prevent a shock when the switching valve 12 returns to neutral as will be described later, and operates the switching valve 12. There is no problem because the amount of drainage is practically no problem.

Next, when the switching valve 12 is returned to neutral to stop the hydraulic actuator (not shown), the spool of the switching valve 12 is returned to neutral by the spring 13 so that the pilot valve
Even if 11 is suddenly operated, the discharge oil from the pilot oil chamber 18 of the switching valve 12 is closed in the return direction to the pilot valve 11 by the check valve 17 provided in the pilot passage 20 and branched from the pilot passage 21 to generate pressure. Since it is gradually discharged through the compensating flow control valve 19, there is no sudden return, and a shock when the hydraulic actuator (not shown) connected to the switching valve 12 is stopped is prevented.

FIG. 2 shows another embodiment obtained by modifying the embodiment shown in FIG. 1 of the present invention, in which a spool valve 23 is used instead of the check valve 17 in the case of FIG. When the switching valve 12 is operated, the operation of the spool valve 23 is switched by the control pressure oil from the pilot valve 11 at a pilot pressure lower than that of the switching valve 12, and the pilot passage 20 is directed to the pilot oil chamber 18 of the switching valve 12. Opens and communicates in the free flow direction. When the switching valve 12 returns to neutral, the volume of the pilot oil chamber of the spool valve 23 is made smaller than that of the pilot oil chamber 18 of the switching valve 12, so that the pilot valve 11 is rapidly returned to neutral and the pilot pressure becomes zero. Then, the spool valve 23 is returned by the spring and closed by the spring faster than the return speed of the switching valve 12, and the pilot passage 20 is shut off, so the oil discharged from the pilot oil chamber 18 of the switching valve 12 returns to the pilot valve 11. The direction is closed, the flow is branched from the pilot passage 21 and returned to the tank through the flow control valve with pressure compensation 19. Therefore, as in the case of the embodiment shown in FIG. 1 described above, when the switching valve 12 is operated, the oil supplied from the pilot valve 11 is
It acts on the pilot oil chamber 18 of the switching valve 12 and at the same time branches from the pilot passage 20 and returns to the tank through the flow control valve 19 with pressure compensation, and the circulation is repeated, so the pilot passage 20 is heated up and the switching valve 12 Is returned to the neutral position, the oil discharged from the pilot oil chamber 18 of the switching valve 12 is closed in the return direction to the pilot valve 11, and the pilot passage
Since it branches off from 21 and is gradually discharged through the flow control valve 19 with pressure compensation, there is no sudden return and a shock at the time of stop is prevented.

FIG. 3 (a) is still another embodiment of the present invention, which is suitable when the bleeding of the pressure oil from the pilot valve 31 is extremely disliked, and the return oil from the pilot pressure chamber of the pilot type switching valve is used. A switching valve 24 is provided upstream of the flow rate control valve with pressure compensation 19 for adjusting the throttle return speed and discharging to the tank, and the switching valve 24 and the check valve are arranged in parallel to form a pilot passage. This switching valve 24 is a pilot valve
It is switched by the pressure oil from 31 and communicates with the pilot pressure chamber. When the pressure oil runs out, it returns with a spring and communicates with the downstream flow control valve with pressure compensation 19. In this case, the pilot valve
The pressure oil supplied from 31 flows to the flow control valve with pressure compensation 19 and circulates, but there is no heat-up effect, but in the valve device on the opposite side, the oil pushed out from the pilot pressure chamber on the opposite side by the pilot pressure is pressure compensated. When the spool is returned to the tank through the attached flow rate control valve 19 and the spool returns to the neutral state, the oil in the pilot passage is absorbed, and as a result, the oil is circulated, which has a heat-up effect.

FIG. 3 (b) is another embodiment obtained by further modifying the embodiment shown in FIG. 3 (a), in which a flow control valve with pressure compensation is incorporated in the switching valve 24. Since it operates in the same manner as in the case of FIG. 3A, detailed description will be omitted.

FIG. 4 shows still another embodiment of the present invention. In the embodiment shown in FIG. 1, the flow control valve with pressure compensation 19 controls the discharge flow rate when the switching valve 12 returns while heating up the pilot passage with the pressure oil from the pilot valve 11 as a part of the bleed. Adjusting the return speed. But,
When the pilot pump capacity is small and the bleed amount is small, the return speed becomes slow and a response delay occurs. Therefore, it is not sufficient to meet the demand for keeping the return speed as it is.

Therefore, a check valve and a flow control valve with pressure compensation 19A are arranged in parallel in the pilot passage 21, and the switching valve 1
A flow control valve 19B with pressure compensation is provided branching from the pilot passage 21 on the second side, and the discharge oil is connected to the tank passage. For this reason, when the switching valve 12 returns to neutral, the pilot passage 21 is not completely shut off, but there is a control flow rate that returns through the throttle of the pressure compensation flow control valve 19A, and branches from the pilot passage 21 to provide pressure compensation. If you want to reduce the flow rate of the flow control valve 19B with pressure compensation on the bleed side by controlling the total flow rate of the two flow rate control valves together with the control flow rate that returns to the tank through the throttle of the flow rate control valve 19B. The flow rate of the flow control valve with pressure compensation 19A can be increased and the return speed of the switching valve 12 can be the same without changing. The heat-up effect of the pilot passage due to the circulation of the pilot pressure oil and the shock prevention when the switching valve is returned to the neutral state are achieved in the same manner as in the above-mentioned respective embodiments.

[Advantages of the Invention] As described above, according to the valve device of the present invention, the pilot type switching valve is used in a situation where the composite control valve for civil engineering and construction work machines has recently been changed to the pilot operation type. In a valve device equipped with a pressure-compensated flow control valve that adjusts the return speed of the valve, a valve is provided in the pilot passage to close the return oil from the pilot oil chamber, and the valve branches from the pilot passage to the tank to return to the tank. A flow control valve with pressure compensation is installed in the tank passage, and when the switching valve is operated, part of the pilot pressure oil is branched from the pilot passage, discharged to the tank via the flow control valve with pressure compensation, and circulation is repeated. Return oil from the pilot oil chamber is shut off or limited by the valve that closes the pilot passage that returns to the pilot valve, and is branched between this shutoff valve and the pilot oil chamber. It is discharged to the tank through the throttle of the flow control valve with pressure compensation and the return speed is adjusted, so that the pilot passage switching valve's greatest problem is the heat-up effect of the pilot passage in cold regions and the switching. It has the effect of preventing shock when the valve is stopped, and both can be solved at the same time. In addition, it has an effect that it has both functions with almost the same component structure as the valve device having the conventional shock prevention effect.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram showing another embodiment of the present invention, and FIGS. 3 (a) and 3 (b) are the hydraulic circuit diagrams of the present invention. FIG. 4 is a hydraulic circuit diagram showing still another embodiment, FIG. 4 is a hydraulic circuit diagram showing still another embodiment of the present invention, and FIGS. 5 (a) and 5 (b) are prior art shock-preventing pilot hydraulic circuits. It is a figure. 11, 31 ... Pilot valve, 12 ... Switching valve, 13 ... Spring, 15 ... Pilot pump, 16 ... Relief valve, 17 ... Check valve, 18 ... Pilot oil chamber, 19, 19A, 19B ... Pressure compensation flow control valve, 20, 21 ... Pilot passage, 22 ... Valve device, 23 ... Spool valve, 24 ... Switching valve, 34 ... Shock prevention valve.

Claims (1)

[Scope of utility model registration request] 1. A valve device comprising a flow control valve with pressure compensation for adjusting the return speed of a pilot type switching valve, wherein the pilot oil is provided in a pilot passage between a pilot oil chamber of the pilot type switching valve and the pilot valve. A valve for closing or limiting return oil from the chamber is provided, and the flow control valve with pressure compensation is arranged in a tank passage branching from the pilot passage to the tank between the valve and the pilot oil chamber. The valve device is characterized in that the discharge oil that has passed through the pressure compensation flow control valve is discharged to the tank.