JPH0318721Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an unloading mechanism in a valve with a pressure compensation mechanism used in various hydraulic circuits.

(Prior Art) Conventionally, a hydraulic circuit using a valve with a pressure compensation (PC) mechanism generally has a system in which oil discharged from a hydraulic pump 1' is supplied to an actuator via a control valve 2', as shown in Fig. 3. The oil discharged from the pump 1' is guided from the pump passage 4' provided in the valve body 3' to the hydraulic chamber 8' at one end of the pressure compensating spool 6' via the communication passage 7', while the load pressure of the actuator is is introduced into the spring chamber 9' at the other end of the spool 6' from the control valve 2' through the throttle 12' and the load pressure introduction passage 11', thereby balancing the spool 6' and increasing the pressure of the pump 1'. The pressure difference between the discharge pressure of the actuator and the load pressure of the actuator is always kept constant in accordance with the set pressure by the spring 10' in the spring chamber 9', so that the pressure of the hydraulic pump is maintained constant without being affected by the load pressure of the actuator. The flow rate determined by the control valve 2' can always be stably supplied to the actuator from the control valve 1'.

The above-mentioned conventional valve with a pressure compensation mechanism does not have an unload passage when in neutral, and when the control valve 2' is in neutral, the discharge pressure of the pump 1' becomes higher than the set pressure of the spring 10'. The spool 6' is pushed rightward in the drawing to communicate the pump passage 4' with the tank passage 5', so that the oil discharged from the pump 1' is unloaded into the tank 13'.
In this case, in order to move the spool 6' to the right by the discharge pressure of the pump 1', the oil in the spring chamber 9' is discharged from the passage 11' through the control valve 2' to the tank 13'. However, since the control valve 2' generally uses a multiple valve consisting of a large number of directional control valves connected, the discharge passage from the spring chamber 9' to the tank 13' is quite long. Therefore, when the viscosity of the hydraulic oil becomes high, especially at low temperatures, the pressure drop of the oil discharged from the spring chamber 9' to the tank 13' becomes high.
Unless the discharge pressure of the pump 1' exceeds the sum of the force of the spring 10' and the pressure loss (back pressure), it is not possible to unload from the pump passage 4' to the tank passage 5'. Also, due to this, when starting the engine at low temperatures, the pump 1'
After the discharge pressure suddenly increases, it fluctuates greatly and does not stabilize until after a while.As a result, an overcurrent acts on the starter when starting the engine, and the cracking rotation does not increase, resulting in poor starting performance. There are other problems.

(Problems to be solved by the invention) The present invention solves these conventional problems and has a pressure compensation function, which minimizes fluctuations in the pump load when starting the engine at low temperatures, etc., and improves the starter performance. It is an object of the present invention to provide a mechanism that can prevent overcurrent from occurring to reduce failures, quickly stabilize the oil discharged from the pump, and improve startability.

(Means for Solving the Problems) The present invention provides a pressure compensating spool slidably in the axial direction on a valve body having a pump passage and a tank passage, and one end of the spool communicates with the pump passage. A hydraulic chamber is provided, a spring chamber is provided at the other end,
A spring for biasing the spool toward the hydraulic pressure chamber is provided in the spring chamber, and a passage for introducing the load pressure of the actuator is provided in communication with the spring chamber, and a damper is provided at the other end of the spool in communication with the tank passage. A damper chamber is provided, a damper spool slidable in the axial direction is provided between the damper chamber and the spring chamber, and a spring is provided that biases the damper spool toward the spring chamber. It is.

(Function) With the above configuration, when the hydraulic pump is started and oil discharged from the pump flows into the hydraulic chamber through the pump passage, the pressure compensated spool is moved toward the spring chamber. Here, when the viscosity of the hydraulic oil is high and the discharge resistance (back pressure) from the spring chamber to the tank is high, such as at low temperatures, the damper spool is retreated by the back pressure, and this retreat causes the spring chamber to An amount of hydraulic oil commensurate with the amount of oil to be discharged from the damper chamber is discharged into the tank via the tank passage. This discharge lowers the pressure in the spring chamber, reduces the back pressure applied to the pressure compensated spool, quickly unloads the pump discharge oil input into the pump passage, and quickly stabilizes the pump discharge pressure. This prevents the generation of surge pressure and prevents overcurrent from acting on the starter when starting the engine, thereby reducing failures and improving startability.

(Embodiment) FIG. 1 shows an embodiment of the present invention. In FIG. 1, a control valve 2 connected to a hydraulic pump 1 is used for, for example, traveling, swinging, boom 2nd speed, and arm 1 of a hydraulic excavator. It is composed of a multiple valve that connects a plurality of directional control valves that supply pressure oil to an actuator of a hydraulic motor or a hydraulic cylinder, and a valve with a pressure compensation mechanism is provided on the upstream side of the valve. This valve with a pressure compensation mechanism has a pressure compensation spool (hereinafter referred to as a PC spool) inside a valve body 3 that includes a pump passage 4 and a tank passage 5.
A hydraulic chamber 8 is provided at one end of the PC spool 6, and a spring chamber 9 is provided at the other end of the PC spool 6. The hydraulic chamber 8 is connected to the pump passage 4 through a communication passage 7 provided in the PC spool 6, and is connected to the spring chamber 9.
is provided with a spring 10 that biases the PC spool 6 toward the hydraulic chamber 8 side. Further, a control valve 2 is connected to the spring chamber 9 via a load pressure introduction passage 11 and a throttle 12 so that load pressure is introduced from an actuator or communicated with a tank 13.

In such a valve with a pressure compensation mechanism, the present invention particularly provides a damper chamber 14 at the end of the PC spool on the spring chamber 9 side, and a damper spool 15 is installed in the axial direction at the opening of the damper chamber 14 on the spring chamber 9 side. A spring 16 is provided in the damper chamber 14 to be slidable and bias the damper spool 15 toward the spring chamber 9, and the damper chamber 14 is communicated with the tank passage 5 through a communication passage 17. In addition, spring 1
For spring 6, a spring having a weaker spring force than the spring 10 is used. 18 is the stopper part of the damper spool 15;
19 is a stopper ring.

With the above configuration, when the hydraulic pump 1 is started, that is, when the engine is started, when the discharge oil of the pump 1 flows into the pump passage 4 of the valve with pressure compensation mechanism, the discharge oil flows into the hydraulic chamber 8 from the communication passage 7. PC
The spool 6 is moved rightward in the drawing to drain the hydraulic oil in the spring chamber 9 from the passage 11 through the throttle 12 and the control valve 2 into the tank 13. At this time, the control valve 2 is in the neutral position, and the discharge resistance from the spring chamber 9 to the tank 13 is high. Therefore, before the hydraulic fluid is discharged from the spring chamber 9, the pressure in the spring chamber 9 ( As the back pressure) increases, the damper spool 15 moves to the left in the figure by a volume corresponding to the volume of the spring chamber 9 that decreases due to the movement of the PC spool 6, that is, to a position where it hits the stopper part 18. move,
By this movement, a volume of hydraulic oil corresponding to the volume of hydraulic oil to be discharged from the spring chamber 9 is discharged from the damper chamber 14 into the tank 13 via the communication passage 17 and the tank passage 5. In addition, in this case, compared to the length and discharge resistance of the passage from the spring chamber 9 through the passage 11 and the throttle 12, etc.,
Since the length of the passage that discharges from the damper chamber 14 to the tank via the communication passage 17 and the tank passage 5 is short and the discharge resistance is small, even if the viscosity of the hydraulic oil is high at low temperatures, the damper chamber 14 The hydraulic oil inside is smoothly discharged to the tank 13, and this discharge reduces the pressure inside the spring chamber 9, and the back pressure applied to the PC spool 6 is reduced, so that the oil discharged from the pump 1 is quickly discharged. The pump 1 is unloaded, preventing the generation of surge pressure on the pump 1, and quickly stabilizing the discharge pressure of the pump 1.

The experimental results of the discharge pressure of pump 1 at this time are as shown in Figure 2. Figure 2 shows that the pump has a higher It can be seen that the discharge pressure of No. 1 becomes stable immediately after startup.

Thereafter, when the discharge oil of the pump 1 is guided to the actuator by switching the control valve 2, the load pressure of the actuator is introduced into the spring chamber 9 through the throttle 12 and the passage 11. At this time, the damper spool 15 hits the stopper portion 18 and is integrated with the PC spool 16. Therefore, as in the conventional case, the discharge pressure of the pump 1 led from the pump passage 4 to the hydraulic chamber 8 via the communication passage 7 is equal to the load pressure of the actuator introduced into the spring chamber 9 and the set pressure of the spring 10. The pressure rises to a pressure corresponding to This means that the required flow rate can always be stably supplied.

Note that the present invention is applicable not only to the hydraulic excavator shown in the above embodiment, but also to construction machines such as hydraulic cranes and other various hydraulic circuits.

(Effects of the invention) As described above, the present invention has a simple structure by providing a damper mechanism to a valve with a pressure compensation mechanism, and can be used even when the viscosity of the hydraulic oil is high, such as at low temperatures. It quickly stabilizes the pump discharge pressure when starting the engine and pump, prevents the generation of surge pressure, and prevents overcurrent from acting on the starter when starting the engine, reducing failures and improving startability. It is possible to improve the

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional structure and circuit explanatory diagram of a valve with a pressure compensation mechanism showing an embodiment of the present invention, Fig. 2 is a diagram showing the characteristics of the discharge pressure at the time of starting the pump according to the invention, and Fig. 3 is a conventional example. FIG. 4 is a diagram equivalent to FIG. 1, and FIG. 4 is a diagram equivalent to FIG. 2. 1... Hydraulic pump, 2... Control valve, 3... Valve body of the valve with pressure compensation mechanism, 4... Pump passage, 5... Tank passage, 6... Pressure compensation spool (PC spool), 7... ...Communication path, 8...
Hydraulic chamber, 9... Spring chamber, 10... Spring, 11...
Load pressure introduction passage, 12... Throttle, 13... Tank, 14... Damper chamber, 15... Damper spool, 16... Spring, 17... Communication path.

Claims (1)

[Scope of utility model registration request] A pressure compensating spool is slidably provided in the axial direction on a valve body having a pump passage and a tank passage, a hydraulic chamber communicating with the pump passage is provided at one end of the spool, and a spring chamber is provided at the other end. A spring for biasing the spool toward the hydraulic chamber is provided in the spring chamber, a passage for introducing load pressure of the actuator is communicated with the spring chamber, and the other end of the spool is communicated with the tank passage. A damper chamber is provided, a damper spool slidable in the axial direction is provided between the damper chamber and the spring chamber, and a spring is provided to urge the damper spool toward the spring chamber. Unloading mechanism for valves with pressure compensation mechanism.