JPS6138201A - Control device for counterbalance valve - Google Patents

Abstract

PURPOSE:To prevent generation of hunting, by indexing a target value of displacement of a control spool and directly controlling the target displacement to adjust an opening of a control unit. CONSTITUTION:A flow sensor 43 is provided in a passage 11, and a pressure sensor 44 is provided in a passage 13. A flow signal and a pressure signal are applied to an operating unit 40. A target flow rate of return oil from a bottom chamber 12 is calculated in the operating unit 40, and a target opening of a control unit is computed on the basis of the target flow rate to directly control a control spool of a counterbalance valve C. Accordingly, when a counter load is applied, the control spool may be controlled irrespective of pressure on the side of a supply passage. Therefore, even when fluctuation in the pressure on the side of the supply passage is large, it is possible to prevent generation of hunting.

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. Ah A.

(Prior Art) FIG. 3 shows a control circuit of a conventional device in which a rod 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 volume 3 is connected to the switching valve V via the - 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 due to 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 exceeds the set pressure. When this happens, 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 tank T. Since it returns, the cylinder S operates to increase the load W.

Also, when the switching valve V 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 in this passage 2 acts as pilot pressure on the pilot chamber 5a via the damping orifice 5b.

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, the pilot chamber is guided 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 passage 2 side decreases, the pilot pressure decreases, 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, this conventional counterbalance valve employs a control method that makes the pressure on the supply passage 2 side, that is, the pilot pressure PI, equal to the cracking pressure Par of the control valve section 5. The opening degree can only be controlled indirectly.

Moreover, since the pressure fluctuation of the pilot pressure P1 is very large, the skin opening of the control valve portion 5 tends to fluctuate due to the fluctuation of the pilot pressure P1.

Therefore, hunting cannot be prevented unless the damping orifice 5b is made very small, but there is a limit to making the damping orifice 5b small as described above, and in the end, conventional counterbalance valve control systems prevent hunting. Could not be prevented.

An object of the present invention is to provide a control device that prevents hunting by adjusting the opening degree of the counterbalance valve regardless of the pressure on the supply passage side when a counterload is applied. .

(Means for Solving the Problems) 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
In the counterbalance valve, the flow rate on the return side when a counter load is applied is controlled by adjusting the opening degree of this control part to prevent the load from running away. hand,
The amount of movement thereof is controlled, and when the counter load is applied, the flow rate on the side that becomes the supply passage and the pressure on the side that becomes the return passage at that time are detected,
inputting these flow rate signals and pressure signals to a calculation unit, calculating a target opening degree of the control unit of the counterbalance valve based on these signals, and inputting this target opening degree signal to a target signal generation unit; The target displacement of the control spool is calculated based on this target opening degree signal, and this target displacement signal is converted into an input electric signal to the electric actuator and transmitted to the electric actuator.

(Operation of the present invention) With the above configuration, the supply flow rate when the counter load acts and the pressure on the return side are detected, and the target opening degree of the control section of the counter: balance valve is determined. Based on this, the target displacement of the control spool is determined. Then, an input electric signal corresponding to this target displacement is supplied to an electric actuator, and the amount of movement of the control spool is controlled by the action of the electric actuator.

Therefore, when a counter load acts, the opening degree of the control section can be adjusted regardless of the pressure on the side that becomes the supply passage.

(Embodiment of the present invention) Fig. 1 is a circuit diagram of the present invention, and Fig. 2 is a counterbalance valve operated by an exciting current to a proportional solenoid. , is connected to the switching valve V via a passage 11, while a passage 13 is connected to the bottom side chamber 12, and an operating check valve 14 and a counterbalance valve C are 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 bows 1B to 19 formed in its main body 15.

The first port 1B is connected to the switching valve V via a passage 20, the second port 17 is connected to the passage 13, and the third port 18 is connected to the tank T. Furthermore, the fourth boat 18 is connected to a pilot pump PP.

This main body 15 is further formed with a valve hole 21, and one end of this valve hole 21 is closed with a closing member 22, while the other end is used to control the stroke amount of the bushing rod 23a according to an excitation current that is an input electric signal. A proportional solenoid 23 is provided as an electric actuator.

In addition to the proportional solenoid, the electric actuator may be a servo motor, a stepping motor, or the like. In addition to current, voltage may also be used as an input signal to the electric actuator.

A control spool C8 is installed in the valve hole 21, and a pilot spool PS is slidably installed in the control spool C8. A spring 25 is interposed between the control spool C8 and a spring receiver 24 provided on the closing member 22 side, and normally, due to the action of this spring 25, the end face of a spacer 26 provided adjacent to the electric actuator 23 is I am in contact with it.

Furthermore, the pilot spool PS has a spring receiver 24.
A spring 27 is interposed between the pilot spool PS and the tip end surface of the rod portion 24a, and the pilot spool PS is normally brought into contact with a stepped portion 28a formed on the inner diameter of the spacer 28.

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 O9 are as follows.

That is, the control spool C8 is connected to the first port 1.
A control portion 29 that forms a first annular recess 28 corresponding to 6 and tapers toward the first annular recess 28.
is formed. When the control spool C5 moves against the spring 25, the control section 28 functions according to the movement position to control the opening degree when the first boat 16 and the second boat 17 communicate with each other. ing.

In addition to the first annular recess 28, a second annular recess 30
, while forming the third annular recess 31, the spacer 26
An annular passage 32 is formed that is open to a pilot chamber 39 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 port 18 regardless of the movement position of the control spool C8, but the hole 35 formed at the bottom of the annular recess 31 allows movement of the pilot spool PS. It opens and closes depending on the position. That is, when both spools cs and ps are in the normal position shown in the figure, the hole 35 is covered by the pilot spool PS, but when the pilot spool PS moves against the spring 27, the hole 35 and the pilot spool PS are closed. The annular groove 36 communicates with the annular groove 36.

Furthermore, the annular passage 32 is always in communication with the annular groove 3B via a hole 37 formed in the control spool C8.

When the proportional solenoid 23 is excited, the bushing rod 23a strokes in response to the input electric signal, and the pilot spool PS is moved against the spring 27 in accordance with the stroke amount.

When the pilot spool PS moves, the third
Since the annular recess 31 and the annular groove 36 communicate with each other, the pressure oil from the pilot pump PP flows from the fourth boat 18 to the third annular recess 31 to the hole 35 to the annular groove 36 to the hole 37 to the annular passage 32.
The pressure flows into the pilot chamber 38 via the control spool OS, and its pressure acts on the end face of the control spool OS.

When this pilot pressure acts, the control spool C5 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 C5 is stopped, which is ultimately proportional to the input electric signal of the proportional solenoid 23. Further, when the excitation current decreases, the pilot spool PS retreats to a position where it balances with the reaction force of the spring 27, and the pilot chamber 39 moves into the communication hole 3.
8, the oil in the pilot chamber 38 flows through the communication hole 3.
8→pilot spool PS→hollow part 45→hole 33 of control spool CS→annular groove 30→short circuit to tank T via third port 18.

That is, the control spool C8 moves following the pilot spool PS, the control spool C8 catches up with the pilot spool PSK, and both spools cs
, ps maintain the illustrated relative relationship, the control spool C8 stops, so the amount of movement of the control spool C9 is proportional to the amount of movement of the pyro/toss spool PS. The amount of movement of this pyro/toss spool PS is proportional to the stroke of the bushing rod 23a as described above, but since the stroke of the bushing rod 23a is proportional to the input electric signal of the proportional solenoid 23, the movement of the control spool C8 is The amount is proportional solenoid 2
It will be proportional to the input electrical signal of 3.

Now, the switching valve V is switched from the neutral position shown in the figure to the left position, and the input electric signal of the proportional solenoid 23 is maximized, and the control section 28. If the opening degree is maximized, the space between the first boat 1B and the second boat 17 will be in a free flow state.

Therefore, the oil discharged from the pump P passes through the passage 20 → first port IG → first annular recess 28 → fully open control section 2θ → 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 lO, 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 returns to the tank T according to the opening degree of the door. Therefore, the load W decreases.

The descending speed of the load W is determined according to the opening degree of the control section 29, and the opening degree is controlled by the input electric signal of the proportional solenoid 23.

The control mechanism shown in FIG. 1 controls the input electrical signal for determining the opening degree of the control section 28.

This control mechanism has a calculation mto and a target signal generator 41 as main elements, and transmits a signal from the target signal generator 41 to the proportional solenoid 23 via an amplifier 42, and outputs an input voltage according to the signal. I'm trying to get a signal.

A flow rate detector 43 is connected to the passage 11, and a flow rate signal Qr detected by the flow rate detector 43 is input to the calculation section 40. In addition, the passage 13
A pressure detector 44 is connected to the pressure detector 44, and a pressure signal P2 detected by the pressure detector 44 is also input to the arithmetic unit 40.

When the flow rate signal Q1 and the pressure signal P2 are input to the calculation section 40 in this way, the calculation section 40 calculates the target flow rate Q2 of the return oil from the bottom side chamber 12, and uses this target flow rate G as a reference. The target opening degree τ of the control section 28 is calculated using the following formula.

Q2 = (A2 / At ) Ql τ = Q2 / C "7T77T In the above formula, A1 is the pressure receiving area of the rod side chamber 10, A
2 is the pressure receiving area of the bottom side chamber 12, τ is the opening degree of the control section 29, C is the orifice flow coefficient, and ρ is the hydraulic oil density.

The target opening degree signal i of the control section 28 calculated based on the supply flow rate Q1 on the passage 13 side and the pressure P2 on the return side of the bottom side chamber 12 is input to the target signal generation section 41.

This target signal generator 4! Now, based on the target opening signal K, the target displacement V of the control spool cs is calculated and output.

The target signal output in this way is applied to the proportional solenoid 23 as an input current to the proportional solenoid 23.
transmitted to.

Therefore, as described above, the amount of movement of the control spool cs is controlled in accordance with the input electric signal, and the opening degree of the control section 29 is adjusted.

In this embodiment, the target displacement y of the control spool cs is determined and the target displacement y is directly controlled. Therefore, when a counter load is applied, the control is controlled regardless of the pressure P1 on the side of the passage 13, which is the supply passage. Can control spool OS.

Therefore, even if the pressure P1 fluctuates, the displacement of the control spool C5 does not fluctuate, thereby eliminating the problem of hunting as in the prior art.

(Effects of the present invention) This invention determines the target value of the displacement of the control spool,
By directly controlling the target displacement and adjusting the opening degree of the control section, control can be performed independently of the pressure on the supply passage side when a counter load is applied, so even if the pressure on the supply passage side is Hunting can be prevented even when fluctuations are severe.

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
3... Control spool, 28... Control section, 40...
Arithmetic unit, 41...Target signal generation unit.

Claims (1)

[Claims] The opening degree of the control section is adjusted according to the amount of movement of the control spool, and by adjusting the opening degree of this control section, the flow rate on the return side is controlled when a counter load is applied, preventing load escape. In this counterbalance valve, the control spool has a configuration in which the amount of movement thereof is controlled according to the input electric signal of the electric actuator, and the flow rate on the side that becomes the supply passage when the counter load is applied. , and the pressure on the side that becomes the return passage at that time, input these flow rate signals and pressure signals to the calculation section, and calculate the target opening degree of the control section of the counterbalance valve based on these signals. , input this target opening degree signal to a target signal generation section, calculate a target displacement of the control spool based on this target opening degree signal, convert this target displacement signal into an input electric signal to the electric actuator, A control device for a counterbalance valve configured to transmit information to the electric actuator.