JPS59113379A - Counterbalance valve - Google Patents

Abstract

PURPOSE:To improve a hunting preventive function, by providing a control mechanism whose open cross-sectional area is determined depending on pilot pressure and by connecting the control mechanism to a pressure chamber on which one end of a main spool is placed. CONSTITUTION:Both the ends of a main spool 24 are placed on pressure chambers 25, 26. The pressure-receiving areas of the spool 24 on the pressure chambers 25, 26 are made almost equal to each other. The pressure chamber 26 is connected to a control mechanism (a) made of a pilot spool 38 provided with a control orifice 44, the cross-sectional area of which is determined depending on pilot pressure conducted to a pilot chamber 40. Since the pilot pressure does not act to the main spool 24, the change in the pilot pressure does not affect the main spool. A hunting preventive function is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a counterbalance valve that prevents hunting.

(Conventional Counterbalance Valve) The conventional counterbalance valve shown in FIG. ing.

However, if the directional control valve 6 is now switched from the neutral position shown in the figure to the left position, the pressure oil from the pump 7 will flow through the passage 8.
Flows into the bottom side chamber 13 of the cylinder 12 via the first port 9 → check valve 10 → second boat 11.

At this time, the return oil in the rod side chamber 14 of the cylinder 11 returns to the tank 18 via the passage 15 and the directional control valve 6.

Therefore, when the directional control valve 6 is switched to the left-hand position as described above, the cylinder 12 rises into a free flow state, causing the load W to rise.

Next, the directional control valve 6 is switched to the right position in the drawing. Pressure oil from the pump 7 passes through the passage 15 to the port 1. .

At the same time, it flows into the pilot chamber 3 through the pilot passage 4 and the orifice 5. - 2 The pilot pressure flowing into the pilot chamber 3 causes the spool 2 to move against the spring 17 and open its control orifice 18. Thus the control orifice 18
When the control orifice 18 opens, the return oil in the bottom side chamber 13 returns to the tank 16 while being throttled according to the degree of opening of the control orifice 18.

Therefore, when the directional control valve 6 is switched to the right position as described above, the cylinder 12 contracts and enters a counterflow state, thereby lowering the load W.

In the conventional counterbalance valve as described above, the orifice 5 is provided in order to prevent the hunting phenomenon that occurs when pilot pressure is suddenly applied to the spool. However, since the pilot pressure acts directly on the spool, changes in the pilot pressure have an adverse effect on the spool, resulting in the disadvantage that the anti-hunting function cannot be fully demonstrated.

The object of the present invention is to provide a counterbalance valve r which eliminates the above-mentioned conventional drawbacks by providing a pilot spool separate from the main spool and applying pilot pressure only to this pilot spool.

(Embodiment of the Invention) The embodiment of the invention shown in FIG. 2 has a first port 21. ! A second port 22 is formed, and a pore 23 is formed in a direction perpendicular to each of these ports.

A main spool 24 is slidably installed inside the pore 23, and both ends of the main spool 24 are connected to the pressure chamber 2.
It is scheduled for May 26th. The pressure receiving areas of the main spool 24 within the pressure chambers 25 and 26 are made approximately equal.

A spring 27 is interposed in the pressure chamber 26, and the action of the spring 27 normally maintains the main spool in the illustrated position. In this illustrated state, the poppet portion 2 formed on the main spool 24 is
8 is in pressure contact with a seat portion 29 formed in the pore 23, and a control orifice 30 formed in the main spool 24 is closed by an annular protrusion 31 formed in the pore 23. In this way, the normally closed control orifice 30 has its opening area determined in proportion to the amount of movement of the main spool 24.

Furthermore, a notch 32 is formed at the end of the main spool 24 facing the pressure chamber 25 side, and the above-mentioned two The pressure chambers 25 and 26 are communicated with each other.

When the main spool 24 configured as described above moves against the spring 27 from the illustrated state, the first port 24
1 and the second port 22 are in direct communication with each other, but these two ports are also communicated through a check valve 35. However, since this check valve 35 only allows flow from the second port 22 to the first boat 23, flow in the opposite direction to the above is blocked via this check valve 35.

Further, the pressure chamber 26 communicates with the control mechanism a through a passage 36, and the configuration of the control mechanism a is as follows.

That is, the control mechanism a has a body 37 assembled into the valve main body 20, and a pilot I spool 38 is housed inside the body 37.

The pilot spool 38 has a pilot pressure receiving surface 39 at its tip facing the pilot chamber 40, and a poppet portion 4 formed on the opposite side from the pilot pressure receiving surface 39.
1 faces into the spring chamber 42. A spring 43 is interposed in the spring chamber 42, and the pilot spool 38 is normally maintained at the illustrated position by the action of the spring.

A control throttle part 44 is formed in the pilot spool 38 as shown in J-, and the control throttle part 44 is closed in the position shown above. When the control throttle section 44 opens, the inside of the pressure chamber 26 communicates with the second port 22 via the control throttle section 44.

The pilot chamber 40 of the control mechanism a as described above communicates with the master cylinder 45, and the booster cylinder 45 moves in conjunction with the directional control valve 48, and moves to a predetermined position according to the amount of movement thereof. Pressure is allowed to flow into the pilot chamber 40 .

The directional switching valve 4B connects one boat to the second boat 22 via a passage 47, and connects the other boat to the rod side chamber 50 of the cylinder 48 via a passage 48.

Further, the bottom side chamber 51 of the cylinder 48 is connected to the first boat 21 via a passage 52.

When the directional control valve 4B is switched from the neutral position shown in the figure to the right position, the pressure oil from the pump 53 flows through the passage 47 → second boat 22 → check valve 35 → pressure chamber 25 → first port 21. It flows into the bottom side chamber 51 of the cylinder 48.

The oil returned from the rod side chamber 50 at this time returns to the tank 54 via the passage 48 and the directional switching valve 46.

Therefore, when the directional control valve 48 is switched to the right position as described above, the cylinder 48 becomes in a free flow state in which it rises, causing the load W to rise.

When the directional control valve 4G is switched to the left side position contrary to the above, the pressure oil of the pump 53 flows into the rod side chamber 50 of the cylinder 49.

At this time, the pressure in the bottom side chamber 51 flows into the Ml port 21 and one pressure chamber 25, and the pressure in the bottom side chamber 51 flows into the notch ff632.
- It also flows into the other pressure chamber 26 via the detection orifice chair 33 and the passage 34, making both pressure chambers at the same pressure.

Since the master cylinder 45 interlocks with the directional switching valve 46, pilot pressure corresponding to the switching amount of the directional switching valve 4G is supplied to the pilot chamber 40. Pilot room 40
When pressure is supplied to the pilot spool 3, the pilot spool moves in proportion to the pilot pressure, opening the restrictor 44.

When the 11th ill throttle part 44 opens, the other pressure chamber 26
Is the oil controlled? Since it flows into the tank 54 via the Jj constriction part 44 and the second port 22, a pressure difference is generated before and after the detection orifice 33.

This differential pressure causes the main spool 24 to move toward the spring 27.
and opens the control orifice 30 of its main spool 24. When the control orifice 30 opens, the hydraulic power in the bottom side chamber 51 - first port 21 -> control orifice 3
0→seat part 29→tank 5 via second port 22
Return to 4. In such a flow path process, a throttling resistance is provided by the control orifice 30.

Therefore, when the directional control valve 48 is switched to the left position, the cylinder 49 contracts and enters a counterflow state, thereby lowering the load W.

In this case, the differential pressure before and after the detection orifice 33 is determined as follows.

P2 ...Pressure in one pressure chamber 25 Px@φ・Pressure a in the other pressure chamber 26 ...Opening area ax of O detection orifice 33 ...Opening area of control throttle part 44, then, From this equation (1), it becomes.

In the above equation (2), since the open area a of the detection orifice 33 is constant, the differential pressure before and after the orifice (P-P
x) is determined by the aperture area aX of the control aperture section 44. Moreover, the opening area aX of the control aperture section 44
is proportional to the pressure in the pilot chamber 40.

Therefore, since the pilot pressure does not directly act on the main spool 24, the influence of changes in the pilot pressure is small, and therefore hunting can be prevented from occurring. Moreover, the pressure in one pressure chamber 25 can be made sufficiently small by simply adjusting the opening area of the control throttle part 44 of the pilot spool, so that the anti-hunting function can be achieved depending on the purpose of use.

In particular, in this embodiment, pilot pressure is supplied from the master cylinder 45 and pilot pressure is obtained according to manual operation of the directional control valve 4B, so there is almost no change in pilot pressure and stable control is achieved. can.

Note that 1 without using a master cylinder like in the above embodiment.
Pilot pressure may be introduced into the pilot chamber 40 from the passage 47.

Even in this case, the pilot pressure does not directly act on the main spool 24, thus allowing stable control. However, in this case, if a stopper is provided at the stroke position of the pilot spool corresponding to the maximum allowable opening area of the control throttle section 44, the pressure in the one pressure chamber 25 can be prevented from becoming abnormally high. , more effective in preventing hunting.

(Configuration of the present invention) The configuration of the present invention includes a main spool that is slidably provided on the valve body, a pressure chamber that faces both ends of the main spool, and a pressure chamber that is located inside the main spool and that connects both pressure chambers. a detection orifice provided in a path for communication, and a control mechanism communicating with one of the pressure chambers on the side whose volume is reduced when the main spool performs a control operation, While the pressure-receiving area of the main spool is made almost equal, the above-mentioned control 4J'j&'l structure allows the pilot pressure-receiving surface to face the biro I chamber, and the opening area is adjusted according to the pilot pressure introduced into the pilot chamber. It is characterized in that it consists of a pilot spool and a pilot spool in which a control throttle part is formed.

Under configuration '-2, no pilot pressure acts on the main spool.

In other words, a pilot pressure acts on the control mechanism, and the opening degree of the control throttle section of the control mechanism is determined in proportion to this pilot pressure. The pressure difference before and after the detection orifice is determined according to this opening degree, and the main spool is operated by the action of this pressure difference.

(Effects of the Present Invention) Since the configuration is as shown in (2), the pilot pressure does not act on the main spool, and even if the pilot pressure changes, the change does not affect the main spool.

Therefore, the anti-hunting function is improved compared to the conventional system in which pilot pressure is applied to the main spool through a damper orifice.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a sectional view showing an embodiment of the present invention. 20... Valve body, 24/e11 main spool, 25
．． 26...Pressure chamber, 33@・Conflict detection orifice, a・
...Control mechanism, 3 days...Pilot spool, 39φ
... Pilot pressure receiving surface, 40 ... Pilot room, 44
... Control aperture section. Attorney Attorney ± 1111 Nobuyuki

Claims (1)

[Claims] A main spool slidably provided on the valve body, a pressure chamber facing both ends of the main spool, a detection orifice provided in the main spool in a path connecting the two pressure chambers, and the above. a control mechanism that communicates with one of the pressure chambers on the side that reduces the volume when the main spool performs a control operation, the pressure receiving area of the main spool in both pressure chambers being approximately equal, The control mechanism is a counterbalance valve consisting of a pilot spool whose pilot pressure-receiving surface faces the pilot chamber and a control throttle portion whose opening area is determined according to the pilot pressure introduced into the pilot chamber.