JPH04224301A - Load response type controller - Google Patents

Abstract

PURPOSE:To prevent increase of energy loss even if discharge pressure of a variable discharge pump exceeds a predetermined limit in a controller which is provided with a control mechanism in which discharge pressure of the variable discharge pump is made higher than load pressure by a certain value and in which a pressure compensation valve is connected to an operating valve. CONSTITUTION:A bleed-off flow passage 30 is formed in an operating valve V1 so that a relay flow passage 29 in which high pressure fluid from a pump flows communicates with a tank flow passage 31 via the bleed-off flow passage 30.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load-sensitive control device that detects the load pressure of an actuator and controls the discharge pressure of a pump.

0002

2. Description of the Related Art In the conventional device shown in FIG.
It is connected to the import 5 of the two-operated valves 3 and 4.

When the operation valves 3 and 4 are in the neutral position shown in the figure, the import 5 is closed, but by switching the spool 6 to either the left or right, the variable orifice 7 opens and the switching amount is The opening degree of the variable orifice 7 is controlled according to this. A pressure compensating valve 9 is connected to the downstream side of the variable orifice 7 via a check valve 8. Furthermore, the downstream side of this pressure compensating valve 9 is communicated with the supply port 10 of the operating valves 3 and 4. This supply port 10 is closed when the operation valves 3 and 4 are in the neutral position, but is communicated with one of the actuator ports 11 and 12 by switching the spool 6 to either the left or right side. At this time, the other actuator port communicates with the tank flow path 13.

Furthermore, a load detection port 14 is formed in the operating valves 3 and 4, and this load detection port 14 communicates with the tank flow path 13 when the operating valves 3 and 4 are in the neutral position. When the operating valves 3 and 4 are switched to either the left or right side, they communicate with the actuator port on the high pressure side.

The pressure compensation valve 9 guides the pressure on the upstream side of the pressure compensation valve 9 to one pilot chamber 9a, and guides the pressure on the load detection port 14 side to the other pilot chamber 9b. However, due to the action of the plurality of shuttle valves 15, the operation valve 3
, 4 is selected and guided to the other pilot chamber 9b. The pressure compensation valve 9 thus configured controls the pressure downstream of the variable orifice 7 to be higher than the maximum load pressure by a constant pressure.

Further, the highest load pressure selected by the shuttle valve 15 is guided to one pilot chamber 16a of the control valve 16. The pressure in the high-pressure passage 2, that is, the discharge pressure of the variable discharge pump 1, is guided to the other pilot chamber 16b of the control valve 16. Therefore, the control valve 16 operates according to the relative difference between the discharge pressure of the variable discharge pump 1 and the maximum load pressure. The operation of the control valve 16 causes the control cylinder 17 to operate, and controls the discharge pressure of the variable discharge pump 1 to be always higher than the maximum load pressure by a certain value. Note that the reference numeral 18 in the figure is a main relief valve.

Due to the interaction between the variable discharge pump 1 and the pressure compensating valve 9 as described above, a constant flow rate proportional to the switching amount of the operating valves 3 and 4 is supplied to the actuator.

[0008]

In the conventional device as described above, the discharge pressure of the variable discharge pump 1 is controlled by the action of the highest load pressure among the plurality of actuators. There is a problem in that energy loss becomes large in the following cases.

For example, when the above device is used in a power shovel and the inertial body is used as a load, such as when turning, the moment the operating valve is switched, the load pressure rises rapidly to accelerate the inertial body, causing the circuit pressure to rise. will rise to the set pressure of the main relief valve 18. As mentioned above, this increased circuit pressure is used as a control signal for each operating valve 3, 4 and variable discharge pump 1, so if a circuit system other than the swirl circuit system uses a large flow rate at low pressure. Then, the variable discharge pump 1 is forced to discharge at a high pressure and large flow rate. In other words, since a high pressure and a large flow rate must be supplied to a circuit system that requires a low pressure and a large flow rate for a swirl circuit system that requires a high pressure and a small flow rate, there is a problem in that energy loss becomes extremely large.

In particular, when the variable discharge pump 1 is under constant horsepower control, if its discharge pressure increases, the dischargeable amount of the pump will decrease along the constant horsepower curve. Therefore, there is a problem in that the flow rate supplied to a circuit system that requires low pressure and large flow rate is restricted.

An object of the present invention is to provide load-sensitive control that prevents the discharge pressure of a variable discharge pump from rising rapidly even when a specific actuator requires a low-pressure minute flow rate, and eliminates the above-mentioned conventional drawbacks. The purpose is to provide equipment.

0012

[Means for Solving the Problems] The present invention provides a plurality of actuators each with an operating valve, a spool built into the valve body of each of these operating valves, and a supply flow path and an actuator connected in accordance with the switching amount of the spool. A pressure compensating valve is provided downstream of the variable orifice to maintain a constant pressure difference between the load pressure and the pressure downstream of the variable orifice,
Furthermore, the present invention is based on a load-sensitive control device equipped with a control mechanism that uses the load pressure and pump discharge pressure as pilot pressures to control the pump discharge pressure to a certain pressure or higher than the load pressure. . Based on the above device, the present invention is characterized in that the upstream side of the pressure compensation valve is communicated with the tank flow path while providing resistance.

[0013]

[Operation] Since the present invention is configured as described above, even if the load pressure of a particular actuator increases, a small flow rate of a part of the discharge amount of the variable discharge pump flows into the tank flow path. Even if the flow rate supplied to the actuator is zero, there is no pressure increase.

[0014]

[Embodiment] Fig. 1, which shows the first embodiment, is a sectional view showing a pressure compensation valve V2 incorporated into an operation valve V1.The configuration other than this operation valve and the pressure compensation valve is the same as the conventional one. be. Therefore, components other than these operating valves and pressure compensation valves will be described using the same reference numerals.

The operation valve V1 has a valve body 21 with a
The spool 22 is slidably inserted therein, and first annular grooves 25 and 26 in which notches 23 and 24 are formed are formed on both sides of the spool 22 at a substantially central position. This first
The annular grooves 25 and 26 are always in communication with supply passages 27 and 28 formed on the valve body 21 side. By switching the spool 22 to either the left or right side, the supply channel 27 or 28 and the relay channel 29 communicate with each other via the first annular groove 25 or 26. However, the flow path area when these communicate with each other varies depending on the amount of overlap between the notches 23 and 24 and the relay flow path 29. In other words, this notch 23,
24 and the relay flow path 29 constitute a variable orifice whose opening degree is varied in proportion to the switching amount of the spool 22.

A bleed-off channel 30 is formed in the spool 22 as described above, and this bleed-off channel 30 is formed by a small hole 3 opened in the center of the spool 22.
0a, and a communication hole 3 formed along the axis of the spool 22.
0b, and a small hole 30c that opens on the opposite side to the small hole 30a. As long as the spool 22 is within the fine switching range, the bleed-off channel 30 configured in this way can
The small hole 30a communicates with the relay channel 29, and the small hole 30c communicates with a tank channel 31 formed on the valve body 21 side.

Further, a pressure compensating valve V2 is connected to the relay flow path 29. This pressure compensating valve V2 is integrated into the valve body 21, and its cylindrical spool 32 is slidable relative to the valve body 21. This cylindrical spool 32 has a check valve 33 built therein, and this check valve 33 is configured to only allow flow from the relay flow path 29 to an outflow port 34 formed in the cylindrical spool 32. And this pressure compensation valve V2
In this case, one pilot chamber 35 is located on the side of the relay flow path 29, and the other pilot chamber 36 is formed on the opposite side to this pilot chamber 35. The highest load pressure selected by the plurality of shuttle valves 15 is applied to the other pilot chamber 36 .

A spring 37 is provided in the other pilot chamber 36. Therefore, the pressure in the pilot chamber 35 is equal to the pressure in the other pilot chamber 36 and the spring 3
When the force that is the sum of the spring force of 7 is overcome, the cylindrical spool 3
2 rises. When the cylindrical spool 32 moves up, the amount of overlap between the outflow port 34 and the high pressure channel 38 is controlled depending on the amount of movement. As a result, the pressure difference between the relay flow path 29 and the high pressure flow path 38 becomes equal to or higher than a certain value.

Depending on the direction of movement of the spool 22, the high pressure flow path 38 communicates with one actuator port 40 via a second annular groove 39, or communicates with the other actuator port 42 via a second annular groove 41. communicate with. Note that when one of these actuator ports 40 and 42 communicates with the high pressure flow path 38, the other communicates with the tank flow path 31.

Next, in explaining the operation of this first embodiment, when the spool 22 is moved rightward in the drawing, the notch 2
3 overlaps with the relay flow path 29, and the opening degree of the variable orifice is determined. Therefore, the pressure fluid supplied to the supply flow path 27 flows into the relay flow path 29, and the pressure at that time acts on one pilot chamber 35 of the pressure compensation valve V2, causing the check valve 33 to open.

One pilot chamber 3 of the pressure compensation valve V2
When pressure is applied to 5 as described above, the cylindrical spool 32
increases to a position where the pressure action in one pilot chamber 35, the pressure action in the other pilot chamber 36, and the spring force of the spring 37 are balanced. This determines the amount of overlap between the outflow port 34 and the high pressure channel 38.

Therefore, the pressure fluid flowing into the relay flow path 29 is supplied to the actuator side from one actuator port 40 via the high pressure flow path 38 and the second annular groove 39. At this time, the return fluid from the actuator flows through the other actuator port 42 and the second annular groove 4.
1 and flows out into the tank flow path 31.

A part of the pressure fluid supplied to the relay flow path 29 in the above state flows out to the tank flow path 31 via the bleed-off flow path 30. Therefore, even if the opening degree of this particular operating valve is set to a minute opening degree and the flow rate supplied to the actuator is zero, only the flow rate to be bled off is ensured. In this way, even if the flow rate supplied to the actuator becomes zero, the minimum bleed-off flow rate is ensured, which prevents a sudden increase in pump discharge pressure and allows the pressure on the load side to change continuously. It also becomes possible.

This will be explained in more detail with reference to the constant horsepower curve shown in FIG. If the load pressure P on the actuator side increases, the flow rate Q decreases accordingly. However, as in the first embodiment, even if the load pressure P exceeds a certain limit, the bleed-off flow rate q1
If this is ensured, the pressure p1 will not rise any further. Therefore, the energy loss can be kept small.

The second embodiment shown in FIG.
1, a bleed-off channel 43 that communicates between the relay channel 29 and the tank channel 31 is directly formed, and the others are as follows.
This is the same as the first embodiment.

In the third embodiment shown in FIGS. 3 to 6, a surge set relief valve 44 is provided in a passage that directly communicates the relay passage 29 and the tank passage 31. This surge set relief valve 44 has a cylindrical valve case 4.
A poppet 46 is slidably provided on the valve case 5, and a seat portion 47 is formed on the relay flow path 29 side of the valve case 45. Further, an auxiliary spool 48 is provided in series with the poppet 46, and a spring 49 is interposed between the auxiliary spool 48 and the poppet 46, and a spring 51 is also provided between the auxiliary spool 48 and the plug 50.
is interposed.

Next, the operation of this third embodiment will be explained. If the pressure on the side of the relay flow path 29 is low, the poppet 46 maintains the seat portion 47 in a closed state as shown in FIG. 4 by the action of the springs 49 and 51. When the pressure on the relay flow path 29 side increases, the pressure acts on the auxiliary spool 48 through the orifice 52 formed in the poppet 46, so that the auxiliary spool 48 acts on the springs 49 and 51 as shown in FIG. move against it. If the auxiliary spool 48 moves in this way, the poppet 46 and the auxiliary spool 48
Since the pressure in the chamber 53 formed between the two ends decreases, the poppet 46 also moves, opening the seat portion 47 as shown in FIG. Therefore, the fluid in the relay flow path 29 flows out into the tank flow path 31 via the small hole 54 formed in the valve case 45. When the pressures in the chamber 53 and the relay channel 29 become equal, only the poppet 46 returns to its original position, closing the seat portion 47 as shown in FIG. The configuration other than the above is the same as that of the first embodiment.

[0028]

According to the control device of the present invention, even if the load pressure exceeds a certain limit, the bleed-off flow rate is ensured, so that the pump discharge pressure does not rise above a certain limit. Therefore, energy loss can be kept small.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an operating valve according to a first embodiment.

FIG. 2 is a sectional view of an operating valve according to a second embodiment.

FIG. 3 is a sectional view of an operating valve according to a third embodiment.

FIG. 4 is a sectional view of a main part of the third embodiment, showing a state in which the seat portion is closed.

FIG. 5 is a sectional view of a main part of the third embodiment, showing a state in which the seat portion is opened.

FIG. 6 is a sectional view of a main part of the third embodiment, showing a state in which the seat portion is closed.

FIG. 7 is a fluff showing a constant horsepower curve.

FIG. 8 is a circuit diagram of a conventional device.

[Explanation of symbols]

V1 operation valve 21 valve body 22 spool 23 one notch 24 constituting the variable orifice
The other notch V2 constituting the variable orifice Pressure compensation valve 30 Bleed-off passage 31 Tank passage 44 Surge set relief valve

Claims (4)

[Claims] [Claim 1] Each of the plurality of actuators is provided with an operating valve, a spool is installed in the valve body of each of these operating valves, and the spool is provided in the process of communicating the supply flow path and the actuator according to the switching amount of the spool. While controlling the opening degree of the variable office, on the downstream side of this variable orifice,
A pressure compensation valve is provided to maintain a constant pressure difference between the load pressure and the pressure on the downstream side of the variable orifice.Moreover, by using the above load pressure and pump discharge pressure as pilot pressures, the pump discharge pressure is kept at a constant pressure than the load pressure. In a load-sensitive control device equipped with a control mechanism that controls the above, the load-sensitive control is characterized in that the upstream side of the pressure compensation valve is communicated with a tank flow path while applying resistance. Device. 2. The load sensitive sensor according to claim 1, wherein a bleed-off passage is formed along the axis of the spool, and the upstream side of the pressure compensation valve and the tank passage are communicated via the bleed-off passage. Shape control device. 3. The load-sensitive control device according to claim 1, wherein a bleed-off passage is formed in the valve body, and the upstream side of the pressure compensation valve and the tank passage are communicated via the bleed-off passage. . 4. The load sensitive control device according to claim 1, wherein the valve body has a mounting hole connecting the pressure compensating valve and the tank flow path, and a surge set relief valve is provided in the mounting hole.