JPS6131703A - Control device of counterbalance valve - Google Patents

Abstract

PURPOSE:To prevent generation of hunting surely by detecting valve displacement of a counterbalance valve and controlling displacement of a control spool directly by the valve displacement signal. CONSTITUTION:A pressure detector 43 is connected to a passage 11 and the pressure signal detected by the pressure detector 43 is inputed to a control mechanism D whose main elements are an arithmetic unit 40 and a first delay circuit 41, and displacement of a control spool is computed in the control mechanism D and the valve displacement signal is inputed as an exciting current into a comparison solenoid 23. By this, the valve displacement of the control spool is directly controlled by the exciting current, then generation of hunting can surely be prevented.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a control device for a counterbalance valve used in a load moving device such as a power shovel or a winch, which prevents the load from running away. be.

(Prior Art) FIG. 3 shows a control circuit of a conventional device, in which a rond side chamber 1 of a cylinder S for raising and lowering a load W is connected to a switching valve V via a passage 2.
On the other hand, the bottom side chamber 3 is connected to a switching valve V via a passage 4.

A counterbalance valve C is connected to the passage 4, and this counterbalance valve C is connected to the control valve section 5.
and a check valve section 6 as the main elements.

The control valve section 5 is provided with a pilot chamber 5a, and the pilot chamber 5a communicates with the passage 2 via a damping orifice 5b. The control valve section 5 normally maintains a closed state by the action of a spring 7 provided on the opposite side of the pilot chamber 5a, but the pilot pressure acting on the pilot chamber 5a is set to the set pressure. When the pressure exceeds that level, the opening degree is controlled according to the pilot pressure.

Further, the check valve section 6 is configured to only allow oil to flow from the switching valve V to the bottom side chamber 3.

When the switching valve V is switched to the right position in the figure, the oil discharged from the pump P is supplied to the bottom side chamber 3 via the passage 4 and the check valve section 6, and the oil in the rod side chamber 1 is supplied to the bottom side chamber 3 through the passage 4 and the check valve section 6. Since it returns to the tank T as it is, the cylinder S operates to increase the load W.

Also, if the switching valve ■ is switched to the left position in the drawing, the pump P
The discharged oil is supplied to the rod side chamber 1, and the pressure within this passage 2 acts on the pilot chamber 5a as pilot pressure.

When this pilot pressure becomes equal to or higher than the set pressure, the control valve section 5 opens and the oil in the bottom side chamber 3 is drained from the tank T.
Therefore, the cylinder S operates to lower the load W. When the control valve section 5 opens in this way, the load W decreases, and the rate of descent at that time is proportional to the degree of opening of the control valve section 5.

Eventually, depending on the magnitude of the pilot pressure, the control valve section 5
The opening degree of the bottom chamber 3 is controlled, and the return flow rate from the bottom chamber 3 is regulated to prevent the load from running on its own.

(Problems to be Solved by the Present Invention) In this conventional device, pilot pressure is introduced from the passage 2 side to control the opening degree of the control valve portion 5.
There was a problem that caused a hunting phenomenon.

For example, when the control valve section 5 is opened with the above pilot pressure, the load W suddenly drops at that moment, so the oil supply to the rod side chamber l cannot follow it, and therefore the pressure on the passage 2 side decreases. As the pressure on the 0 passage 2 side decreases, the pilot IJE becomes low, and at that moment the control valve section 5 performs a valve closing action.

By repeating such a valve opening action and a valve closing action, hunting occurs in the control valve part 5, but the more sensitive the control valve part is to react to changes in pilot pressure, the more the load W The larger the value, the more intense the above hunting becomes.

Therefore, if the opening area of the damping orifice 5b is made smaller and the responsiveness of the control valve section 5 to changes in pilot pressure is made worse, hunting can be prevented to some extent, but if the damping orifice 5b is made smaller,
It's easy for trash to get stuck there. If this orifice 5b is clogged with dirt, the valve function will be impaired.
There is a limit to how small the orifice 5b can be, and therefore there is a problem in that the hunting phenomenon described above cannot be completely prevented.

In other words, in this conventional counterbalance valve, the pressure on the supply passage 2 side, that is, the pilot pressure P! Since a control method is adopted in which the cracking pressure Per of the control valve section 5 is made equal to the cracking pressure Per of the control valve section 5, the opening degree of the control valve section 5 can only be controlled indirectly.

Therefore, it has not been possible to solve the problem of hunting occurring when the pilot pressure P1 changes rapidly.

An object of the present invention is to provide a control device that detects the pressure on the supply passage side when a counter load is applied, calculates the valve displacement of the control spool, and directly controls the control spool with this calculation signal. do. (Means for solving the problem) In order to achieve the above object, the present invention adjusts the opening degree of the control section according to the amount of movement of the control spool, and also adjusts the opening degree of the control section according to the amount of movement of the control spool. In a counterbalance valve that prevents load runaway by controlling the flow rate on the return side when a counter load is applied, the control spool has a movement amount that is adjusted according to the excitation current of the proportional solenoid. In addition to detecting the pressure on the supply passage side when the counter load is applied, the pressure signal is input to the calculation section, and based on that signal, the control spool is controlled. In addition to calculating the moving speed, this moving speed signal is input to the first-order delay circuit, which integrates the speed signal to detect the valve displacement of the control spool, and converts this valve displacement signal into an exciting current for the proportional solenoid. The structure is such that the signal is converted and transmitted to the proportional solenoid.

(Operation of the present invention) With the above configuration, the pressure on the supply side when a counter load acts is detected, the valve displacement of the counterbalance valve is detected, and this valve displacement signal is used to control the control spool. Directly control displacement. Since the displacement of the control spool is directly controlled in this way, it is possible to prevent hunting from occurring as in the conventional case.

(Embodiment of the present invention) FIG. 1 is a circuit diagram of the present invention, in which a rod side chamber 10 of a cylinder S for raising and lowering a load W is connected to a switching valve V via a passage 11, while a bottom side chamber 12 is connected to a switching valve V through a passage 11. A passage 13 is connected thereto, and an operating check valve 14 and a counterbalance valve CIr are also connected to this passage 13.

The operated check valve 14 normally only allows flow from the counterbalance valve C to the bottom side chamber 12 and blocks the reverse flow, but when the pressure on the passage 11 side acts on the operated check valve 14. The valve is sometimes opened to allow the reverse flow described above.

Further, the counterbalance valve C has first to fourth boats 18 to 19 formed in its main body 15.

The first port 1B is connected to the switching valve ■ via the passage 2o, and the second port l? is connected to the passage 13, and the third port 18 is connected to the tank T. Furthermore, the fourth boat 19 is connected to a pilot pump PP.

A valve hole 21 is roughly formed in this main body 15, and one end of this valve hole 21 is closed with a closing member 22, while a proportional valve hole 21 is installed at the other end to control the stroke amount of the bushing rod 23a according to the excitation current. There are 23.

A control spool CS is installed in the valve hole 21, and a pilot spool PS is installed in the control spool C8 so as to be relatively movable. The control spool C8 is connected to a spring receiver 24 provided on the closing member 22 side.
A spring 25 is interposed between the proportional solenoid 23 and the proportional solenoid 23, and normally the proportional solenoid 23 is brought into contact with the end surface of the spacer 2B provided adjacent to the proportional solenoid 23.

Furthermore, the pilot spool PS has a spring receiver 24.
A spring 27 is interposed between the pilot spool PS1 and the tip end surface of the rod portion 24a, and the pilot spool PS1 is normally brought into contact with a stepped portion 2fla formed on the inner diameter of the spacer 2B.

A proportional solenoid 2 is attached to the tip of the pilot spool PS, that is, to the end opposite to the spring 27.
Although the bushing rod 23a of No. 3 is in a working relationship, the specific configurations of these two spools PS and C8 are as follows.

That is, the control spool C5 is connected to the first port 1.
A control portion 28 that forms a first annular recess 28 corresponding to 8 and tapers toward the first annular recess 28.
is formed. When the control spool CJ moves against the spring 25, the control section 28 functions according to the movement position to control the opening degree when the first boat 1B and the second boat 17 communicate with each other. ing.

In addition to the first annular four part 28, a second annular four part 30
, while forming the third annular recess 31, the spacer 26
An annular passage 32 is formed that is open to a pilot chamber 38 on the side.

The second annular recess 30 always communicates with the third boat 18 regardless of the movement position of the control spool C8, and via the hole 33 formed at the bottom of the annular recess 30,
It communicates with the hollow portion 34 of the control spool C8.

Further, the third annular recess 31 always communicates with the fourth boat 19 regardless of the movement position of the control spool C8, but the hole 35 formed at the bottom of the annular recess 31 allows the pilot spool PS to move. It opens and closes depending on the position. That is, when both spools C9 and PS are in the normal position shown in the figure, the hole 35 is blocked by the pilot spool PS, but when the pilot spool PS moves against the spring 27, a formation is formed between the hole 35 and the pilot spool PS. The annular groove 38 communicates with the annular groove 38 .

Further, the annular passage 32 is always in communication with the annular groove 38 through a hole 37 formed in the control spool C8.

A communication hole 38 is formed in the pilot spool PS, but since both spools cs and ps are in the positional relationship shown in the figure, only the control spool C8 is connected to the spring 2.
5, the communication hole a8 opens toward the pilot chamber 38.

When the proportional solenoid 23 is excited, the bushing rod 23a strokes in accordance with the exciting current, and the pilot spool PS is moved against the spring 27 in accordance with the stroke amount.

When the pilot spool PS moves in this way, the third
Since the annular recess 31 and the annular groove 3B communicate with each other, the pressure oil from the pilot pump PP flows through the fourth port 19 → the third annular recess 31 → the hole 36 → the annular groove 38 → the hole 37 → the annular passage 32.
The pressure flows into the pilot chamber 38 via the control spool C9, and its pressure acts on the end face of the control spool C9.

When this pilot pressure acts, the control spool C8 moves against the spring 25 and stops at a position where the hole 35 of the control spool C8 is blocked by the pilot spool PS. In this manner, the opening degrees of the first boat 1B and the second boat 17 are determined depending on the position where the control spool C8 is stopped, which is ultimately proportional to the excitation current of the proportional solenoid 23.

That is, the control spool C3 moves following the pilot spool PS, the control spool C8 catches up with the pilot spool PS, and both spools cs
, ps maintain the illustrated relative relationship, the control spool C5 stops, so the amount of movement of the control spool C6 is proportional to the amount of movement of the pilot spool PS. The amount of movement of this pilot spool PS is proportional to the stroke of the bushing rod 23a as described above, but since the stroke of this bushing rod 23a is proportional to the exciting current of the proportional solenoid 23, the amount of movement of the control spool C8 is , is proportional to the excitation current of the proportional solenoid 23.

Now, if the switching valve V is switched from the neutral position shown in the figure to the left position, and the exciting current of the proportional solenoid 23 is maximized to maximize the opening degree in the control section 29, the first
A state of free flow occurs between the boat 1θ and the second port 17.

Therefore, the oil discharged from the pump P passes through the passage 20 → first port 16 → first annular section 28 → fully open control section 28 → second boat 17 → operating check valve 14.
While being supplied to the bottom side chamber 12, the rod side chamber 10
Since the oil returns to the tank via the passage 11, the load W increases.

Also, when the switching valve V is switched to the right position in the drawing, the pump P
Pressure oil is supplied to the rod side chamber 10, and the supply pressure acts on the operating check valve 14 to open it.

At the same time, the proportional solenoid 23 is energized,
If the opening degree of the control section 28 is determined, the return oil from the bottom side chamber 12 will return to the tank T according to the opening degree, so that the load W will be lowered by 6 degrees, and the lowering speed of this load W will be lowered by 6 degrees. is determined according to the opening degree of the control section 28, and the opening degree is controlled by the exciting current of the proportional solenoid 23.

The control mechanism 4 shown in FIG. 1 controls the excitation current for determining the opening degree of the control section 29.

This control mechanism has an arithmetic unit 40 and a first-order lag circuit 41 as main elements, and transmits a signal from the first-order lag circuit 41 to the proportional solenoid 23 via an amplifier 42, so that an excitation current according to the signal is transmitted. I'm trying to get it.

A pressure detector 43 is connected to the passage 11, and a pressure signal P1 detected by the pressure detector 43 is inputted to the calculation unit 40, and the calculation unit 40 combines the pressure signal P1 and the target pressure. Calculate the difference between the signal Pcr and 1.
The calculation result is input to the first-order lag circuit 41.

The first-order delay circuit 41 multiplies the difference by α, which is a coefficient for the moving speed, to obtain the moving speed y. That is,
Find 夛=α(P, 1-Per).

Then, this shift is further integrated to calculate the displacement of the control spool O9, and this valve displacement signal is sent to the amplifier 4.
2, it is input to the proportional solenoid 23 as an exciting current.

Therefore, since the valve displacement of the control spool C5 is directly controlled by the excitation current, hunting as described in the prior art is less likely to occur.

Further, if a portion for electrically adjusting the above-mentioned α is provided, this α can be made sufficiently small, and if this α can be made small, the moving speed of the valve can also be made small. Therefore, hunting can be further prevented.

(Effects of the present invention) This invention adjusts the opening degree of the control section by directly controlling the displacement of the control spool. Unlike conventional methods, which only indirectly control the opening of the
can be reliably prevented from occurring.

Furthermore, since the damping orifice is electrically controlled, there is no need for a damping orifice as in the past, and therefore there is no need for management that takes into account clogging of the damping orifice.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention, with Figure 1 being a circuit diagram, Figure 2 being a sectional view of a counterbalance valve, and Figure 3 being a circuit diagram of a conventional device. . 11.13... Passage, 23... Proportional solenoid, C
8... Control spool, 28... Control section, 40...
Arithmetic unit, 41...first-order delay circuit.

Claims (1)

[Claims] By adjusting the opening degree of the control section according to the amount of movement of the control spool, and adjusting the opening degree of this control section,
In a counterbalance valve that prevents load runaway by controlling the flow rate on the return side when a counterload is applied, the control spool has a configuration in which the amount of movement thereof is controlled in accordance with the excitation current of the proportional solenoid. , detecting the pressure on the side that becomes the supply passage when the counter load is applied, and inputting the pressure signal to the calculation section;
Based on that signal, the moving speed of the control spool is calculated, and this moving speed signal is input to the first-order delay circuit, which integrates the speed signal to detect the valve displacement of the control spool, and then calculates the moving speed of the control spool. A counterbalance valve control device configured to convert a displacement signal into an excitation current for the proportional solenoid and transmit the same to the proportional solenoid.