JPH06193605A - Hydraulic driving device and control valve - Google Patents

Abstract

PURPOSE:To provide a hydraulic driving device and a control valve which can prevent occurrence of hunting with certainty. CONSTITUTION:A meter-in spool 1 controls a flow rate of pressure oil which is supplied to a running motor 32. A meter-out spool 2 controls a pressure on a supplying side of the running motor 32. A multiplier 24 multiplies the pressure on the supplying side of the running motor 21, which pressure is controlled by the meter-out spool 2, by a pressure gain beta. A subtracter 25 subtracts a computation value of the multiplier 24 from a command flow rate Qc. An electromagnetic actuator 10 operates the meter-in spool 1 according to the computation value of the subtracter 25, and controls its opening. It is thus possible to prevent occurrence of hunting with certainty, attain smooth operation of a hydraulic actuator compared to a conventional case, and improve durability of whole of a circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive device for a hydraulic machine such as a hydraulic excavator, which drives a hydraulic motor such as a traveling motor and a hydraulic actuator such as a hydraulic cylinder such as an arm cylinder, and the hydraulic drive device. The present invention relates to a control valve provided in, and particularly to a hydraulic drive device and a control valve suitable for driving a hydraulic actuator whose load pressure direction changes.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing an example of a conventional hydraulic drive system for driving a hydraulic actuator in which the direction of load pressure changes. For example, the hydraulic drive system provided in a hydraulic shovel is shown. This hydraulic drive system includes a hydraulic pump 34.
And a hydraulic actuator driven by the pressure oil supplied from the hydraulic pump 34, for example, the traveling motor 32,
A flow rate control means, which is disposed between the hydraulic pump 34 and the traveling motor 32 and controls the flow rate of the pressure oil supplied to the traveling motor 32, that is, a direction switching valve 33, and a meter-in side which is a supply side of the traveling motor 32. It has a pressure control means for controlling the pressure, that is, brake valves 31a and 31b.

Generally, in a hydraulic excavator, a resistance load is applied to the traveling motor 32 when traveling on a flat surface or an ascending slope, but a negative load is applied to the traveling motor 32 when traveling down a slope. In the case of this slope descending traveling, the traveling motor 32 acts as a pump, which tends to cause a negative pressure on the meter-in side of the traveling motor 32. In order to prevent such a negative pressure, the brake valve 31
a and 31b are provided.

Now, it is assumed that the traveling motor 32 receives a negative load while the pressure oil discharged from the hydraulic pump 34 is flowing as shown in FIG. At this time, the pressure P ₁ on the meter-in side of the traveling motor 32 decreases as compared with that before. When this pressure P ₁ becomes smaller than a predetermined set pressure determined by the force of the spring of the brake valve 31a, the brake valve 31a operates toward the throttle side, and the braking force is applied to the travel motor 32 accordingly, and the meter-in side is operated. The pressure P ₁ is controlled so as to be maintained above a predetermined set pressure.
By this control, the occurrence of cavitation due to the pressure P ₁ on the meter-in side of the traveling motor 32 becoming a negative pressure is prevented.

[0005]

However, in the above-mentioned prior art, since the brake valves 31a and 31b are provided, the entire circuit has a structure in which vibration easily occurs. That is, the pressure drop on the meter-in side →
Cyclical movement of the corresponding brake valve in the closing direction → increase of the pressure on the meter-in side → corresponding brake valve in the opening direction occurs continuously, and hunting is likely to occur. If such hunting occurs, smooth operation of the traveling motor 32 cannot be realized. In order to prevent the occurrence of such hunting, it is necessary to carefully tune the brake valves 31a and 31b over time when manufacturing them. However, there was a concern that the above-mentioned hunting would occur.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to provide a hydraulic drive device and a control valve capable of reliably preventing the occurrence of hunting.

[0007]

To achieve this object, the invention according to claim 1 of the present invention comprises a hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, In a hydraulic drive device comprising a flow rate control means for controlling the flow rate of pressure oil supplied to the hydraulic actuator and a pressure control means for controlling the pressure on the supply side of the hydraulic actuator, the flow rate control means is the hydraulic pump. A meter-in spool valve arranged between the hydraulic actuator and the pressure control means comprises a meter-out spool valve arranged between the hydraulic actuator and the tank, and is controlled by the meter-out spool valve. The meter spool valve is opened according to the magnitude of the pressure on the supply side of the hydraulic actuator. Are the configuration in which the opening control means for controlling.

The invention according to claim 6 is a meter-in spool arranged in one valve body between a hydraulic pump and a hydraulic actuator to control the flow rate of pressure oil supplied to the hydraulic actuator. A valve and a meter-out spool valve that is arranged between the hydraulic actuator and the tank and that controls the pressure on the supply side of the hydraulic actuator are provided.

[0009]

Since the invention according to claim 1 of the present invention is configured as described above, the spool opening degree of the meter-in spool valve according to the commanded flow rate to the meter-in spool valve is set to X _MI , the flow rate. When the gain is α, the load pressure on the supply side of the hydraulic actuator is P ₁ , and the pressure gain is β, the opening of the meter-in spool valve is controlled by the operation of the opening control means so as to decrease according to the load pressure P _1. If the flow rate supplied to the hydraulic actuator is Q _MI , then Q _MI = αX _MI −βP ₁ . Therefore, when the load pressure P ₁ is lower than a predetermined value set in advance is larger flow rate Q _MI than the flow rate Q _MI when the load pressure P ₁ is kept at a predetermined value is supplied to the hydraulic actuator, the The load pressure P ₁ is controlled to a predetermined value, and damping is applied to this hydraulic system, so that hunting can be reliably prevented.

Further, according to the invention described in claim 6, since the meter-in spool valve and the meter-out spool valve for performing the above-mentioned operation are integrated into one valve body, an integrated structure is provided. It is applicable to the invention, compact, and easy to handle.

[0011]

Embodiments of the hydraulic drive system and control valve of the present invention will be described below with reference to the drawings. 1 is a circuit diagram showing an embodiment of a hydraulic drive system and a control valve of the present invention, FIG. 2 is a diagram showing characteristics obtained in the embodiment shown in FIG. 1, and FIG. 3 is a control system of the embodiment shown in FIG. It is a block diagram showing.

The hydraulic drive system shown in FIG. 1 is provided, for example, in a hydraulic excavator, and in the figure 32 is a hydraulic actuator whose load direction can change during operation, such as a traveling motor. A control valve of the present invention is provided to control the drive of the traveling motor 32. The control valve is disposed in the valve body 3 forming the main body and is supplied to the traveling motor 32. Flow rate control means for controlling the flow rate of the pressure oil, that is, the meter-in spool 1 forming a meter instrument valve, and pressure control means for controlling the pressure on the supply side of the travel motor 32, which are arranged in the valve body 3. A meter-out spool 2 forming a meter-out spool valve, and a pump-out pressure Ps and a maximum load pressure P _L m of the circuit provided on the discharge side of the meter-in spool valve.
It is provided with pressure compensating valves 4a and 4b which are driven according to the pressure difference from ax.

The meter-in spool valve described above is located between the pump port 22 connected to a hydraulic pump (not shown) and the load passages C ₁ and C ₂ connected to the traveling motor 32. , The load passages C ₁ and C ₂ connected to the traveling motor 32, and the tank port T connected to a tank (not shown).

In the valve body 3 described above, the oil passages 7 for introducing the load pressures P ₁ and P ₂ of the traveling motor 32, respectively.
a, 7b, a shuttle valve 23 for selectively taking out the larger one of the load pressures P ₁ , P ₂ guided to these oil passages 7a, 7b, and the drive piston portion 8 of the meter-in spool 1 for operating Control oil passages 20a, 20b for guiding the pressure oil of
And control oil passages 21a and 21b for guiding pressure oil for operating the drive piston portion 9 of the meter-out spool 2. The meter-in spool valve is provided with a spring 6 at the end of the meter-in spool 1 and has a pump port 22.
And the meter-in spool 1 portion located between the outlet side port where the pressure compensation valves 4a and 4b are provided, and the meter-out spool valve 2
Is provided with a spring at the end of the meter-out spool 2, and is provided with orifices 2a and 2b at the portion of the meter-out spool 2 located between the port connected to the load passages C ₁ and C ₂ and the tank port T. There is.

In the valve body 3 described above, the control oil passage 20 is filled with pressure oil according to the commanded flow rate Qc of the traveling motor 32.
a, an electromagnetic actuator 10 to be supplied to 20b, the travel motor 32 meter-pressure is the pressure oil supply side of, for example, the load pressure P ₁ to determine meter command pressure P ₁₀ in the pressure oil to control oil passage 21a corresponding, 21b The electromagnetic actuator 11 to be supplied to and the pressure sensor 5 for detecting the pressure selected by the shuttle valve 23, that is, the load pressure are integrally mounted.

Further, in this embodiment, means for controlling the drive of the meter-out spool valve in accordance with the signal output from the pressure sensor 5, that is, the load pressure detected by the pressure sensor 5 from the meter-in command pressure P ₁₀ , for example, A subtractor 26 is provided which subtracts P ₁ and outputs a drive signal to the electromagnetic actuator 11.

Further, the load pressure detected by the pressure sensor 5,
For example, a multiplier 24 that multiplies P ₁ by a pressure gain β that is a damping element, a subtractor 25 that subtracts βP ₁ obtained by the multiplier 24 from a command flow rate Qc that determines the flow rate to be supplied to the traveling motor 32, and this subtractor The electromagnetic actuator 10 is driven according to the calculated value of 25 and controls the operation of the meter-in spool 1.

The pressure sensor 5, the multiplier 24, the subtracter 25, and the electromagnetic actuator 10 described above constitute an opening control means for controlling the opening of the meter-in spool valve according to the load pressure P ₁ .

The control system in this embodiment is constructed as shown in FIG. In FIG. 3, α is the flow rate gain, X _MI is the opening degree of the meter-in spool valve, and Q _MI is
_MI is a control flow rate actually supplied to the traveling motor 32.

The operation of the embodiment thus constructed is as follows. That is, when the command flow rate Qc and the meter-in command pressure P ₁₀ (for example, 15 atmospheric pressure) are given to drive the traveling motor 32, the command flow rate Qc
Accordingly, the electromagnetic actuator 10 is driven, and as a result, an effective differential pressure is generated in the control oil passages 20a and 20b, and the meter-in spool 1 including the drive piston portion 8 resists the force of the spring 6a, for example, as shown in FIG. Move to the right. With this,
Pressure oil discharged from a hydraulic pump (not shown) flows out through the pump port 22 and the orifice 1a. This pressure oil pushes up the poppet of the pressure compensating valve 4a to load the load passage C.
Guided to ₁ . At this time, the poppet of the pressure compensating valve 4b is kept closed.

On the other hand, the electromagnetic actuator 11 is driven in accordance with the meter-in command pressure P ₁₀ , thereby generating an effective differential pressure in the control oil passages 21a and 21b, and the meter-out spool 2 including the driving piston portion 9 has the spring 6b. Against force
Move to the right in FIG. Accordingly, the traveling motor 32
The load passage C ₂ is connected to a tank (not shown) via the orifice 2b and the tank port T. As a result, the traveling motor 32 is driven, and the load pressure P ₁ is generated in the load passage C _1, that is, the meter-in side. This load pressure P ₁ is applied to the passage 22a.
Is taken out from the shuttle valve 23 via the pressure sensor 5
Detected in. The load pressure P detected by the pressure sensor 5
₁ is given to the subtractor 26 and [meter-in command pressure P ₁₀
The drive signal is output to the electromagnetic actuator 11 so that the load pressure P ₁ ] becomes 0, that is, the load pressure P ₁ matches the meter-in command pressure P ₁₀ . Along with this, the meter-out spool 2 slightly moves to the left in FIG. 1, for example, and the load passage C _{2 is} slightly throttled, whereby the load pressure P ₁ on the meter-in side keeps the command pressure P _10. Controlled.

On the meter-in spool valve side, the pressure P ₁ detected by the pressure sensor 5 in the multiplier 24 is multiplied by the pressure gain β, and the command flow rate Qc (=
βP ₁ multiplied by the multiplier 24 is subtracted from αX _{M 1} ), the electromagnetic actuator 10 operates according to the subtracted value, and the meter-in spool 1 slightly moves to the left in FIG. It moves and the opening degree of the orifice 1a is controlled. At this time, the control flow rate Q _M1 supplied to the traveling motor 32 is expressed by the following equation. Q _M1 = αX _M1 −βP ₁ Therefore, when the hydraulic excavator equipped with the traveling motor 32 is traveling on level ground, the load pressure P ₁ should be kept at the meter-in command pressure P ₁₀ (constant value). The control flow rate Q _M1 supplied to the traveling motor 32 depends on the opening X _M1 of the meter-in spool 1, and the opening X _M1 is determined by the command flow rate Qc. The traveling speed can be controlled.

Further, the hydraulic excavator descends on the slope, and the traveling motor 32 acts as a pump.
When the load pressure P ₁ on the meter-in side decreases, the value of βP _{1 in} the above equation becomes smaller than that on the level ground running until then, so the electromagnetic actuator 10 causes the meter-in spool 1 to output a signal from the subtractor 25. The operation is performed so as to increase the opening degree, whereby the control flow rate Q _M1 is controlled to increase. FIG. 2 shows the characteristics of the control flow rate Q _M1 at this time. In this way, the control flow rate Q _M1 is increased as the load pressure P ₁ is decreased, and the meter-out spool is adjusted so that the load pressure P ₁ decreased by the subtractor 26 and the electromagnetic actuator 11 becomes a predetermined meter-in command pressure. By driving the valve 2, the lowered load pressure P ₁ rises to become the command pressure P _10, and the occurrence of cavitation in which the load pressure P ₁ on the meter-in side becomes a negative pressure is prevented. Further, at this time, the control flow rate Q _M1 supplied to the traveling motor 32 increases in proportion to the pressure gain β, so that damping is given to the hydraulic system, thereby preventing hunting.

Although not shown in FIG. 1, the hydraulic excavator is provided with various hydraulic actuators such as a swing motor, a boom cylinder, an arm cylinder, and a bucket cylinder in addition to the traveling motor 32. Although not particularly shown in the present embodiment, a pressure compensating valve is provided corresponding to each of these hydraulic actuators. Traveling motor 3
In the combined drive of 2 and another hydraulic actuator, the corresponding hydraulic actuator and all the pressure compensating valves including the pressure compensating valves 4a and 4b having the maximum load pressure P _L max of the load pressures of the traveling motor 32 are pumped. It is given so as to face the discharge pressure. As a result, combined drive of the corresponding hydraulic actuators can be realized without being affected by fluctuations in the load pressure of the other actuators. Such pressure compensating valve and pump discharge pressure control device are known.

In the embodiment configured as described above,
Since the occurrence of hunting can be prevented, the traveling motor 32
It is possible to realize smooth driving of the.

Further, in particular, the control valve is compact and easy to handle because the meter-in spool valve and the meter-out spool valve are arranged inside the valve body 3.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention. In the second embodiment, the pump discharge pressure Ps and the traveling motor 3 taken out by the shuttle valve are integrated with the control valve.
_No. 2 load pressure P ₁ or P ₂ , a differential pressure sensor 50 for detecting a differential pressure, for example, a differential pressure ΔP _L = Ps−P ₁ , and a spool position for detecting the spool displacement x of the meter-in spool 1. A sensor 60 is provided. In addition, the differential pressure sensor 5
The arithmetic unit 70 that squares the differential pressure ΔP _L detected at 0 and the functional relationship A (x) between the spool displacement x and the opening of the meter-in spool valve are set in advance, and the spool position sensor 6
It is supplied to the traveling motor 32 by multiplying the computing unit 80 for obtaining the corresponding opening of the meter-in spool valve from the spool displacement x detected at 0, and the computing value of the computing unit 70 and the computing value of the computing unit 80. And a multiplier 90 for obtaining the flow rate Q. The flow rate Q is represented by the following formula. Q = A (x) √ (2ΔP _L / ρ) It is known that the flow rate can be obtained by such an equation.

In the subtractor 25, the commanded flow rate Q is set as described above.
An operation of subtracting βP ₁ from c is performed, and an operation of subtracting the flow rate Q obtained by the multiplier 90 from the commanded flow rate Qc is performed.

The spool position sensor 60, the differential pressure sensor 50, the calculator 70, the calculator 80, the multiplier 90, and the subtracter 25 described above open the meter-in spool valve so that the flow rate Q matches the command flow rate Qc. It constitutes a flow rate feedback means for controlling the flow rate. That is, the electromagnetic actuator 10 controls the drive of the meter-in spool 1 so that the difference between the commanded flow rate Qc and the flow rate Q obtained by the subtractor 25 becomes zero.

In the second embodiment, the pump discharge pressure sensor 65 for detecting the pump discharge pressure Ps and the pump discharge pressure Ps detected by the pump discharge pressure sensor 65 are detected by the differential pressure sensor 50 described above. is provided with a subtracter 27 for obtaining the load pressure P ₁ of the meter-in the differential pressure [Delta] P _L by subtracting the difference, the subtractor 27 in the embodiment similarly to the subtracter 26 to the load pressure P ₁ is above obtained Given to the subtractor 2
In step 6, a calculation for subtracting the load pressure P ₁ from the meter-in command pressure P ₁₀ is performed, the electromagnetic actuator 11 is driven according to the difference, and the opening of the meter-out spool 2 is controlled. The other structure is almost the same as that of the embodiment shown in FIG.

The second embodiment constructed as described above is different from the embodiment shown in FIG. 1 except that the flow rate servo for the commanded flow rate Qc is constructed and more accurate flow rate control can be performed. The same effect is obtained.

That is, even in the second embodiment,
The electromagnetic actuator 11 and the meter-out spool 2 are driven such that the load pressure P ₁ on the meter-in side corresponding to the meter-in command pressure P ₁₀ is obtained. The load pressure P ₁ thus controlled by the meter-out spool valve and the pressure gain β are multiplied by the multiplier 24, and the value is supplied to the subtractor 25 which gives the command flow rate Qc as in the above-described embodiment. Therefore, the equation Q _M1 = αX _M1 −βP ₁ described above also holds in the second embodiment, and the load pressure P ₁ on the meter-in side of the traveling motor 32 is obtained.
Is lower than the predetermined meter-in command pressure P _10, the opening degree of the meter-in spool 1 is increased, a larger flow rate is supplied than before, and the meter-out spool 2 is also actuated to operate the meter-in side. Since the load pressure P ₁ is increased to the meter-in command pressure P ₁₀ ,
It is possible to prevent the occurrence of cavitation and the occurrence of hunting, and it is possible to realize smooth driving of the traveling motor 32.

[0033]

As described above, the hydraulic drive system of the present invention has the following features.
The meter-in spool valve can control the flow rate of the hydraulic actuator independently and the meter-out spool valve can control the pressure of the hydraulic actuator independently, and the opening of the meter-in spool valve can be controlled according to the pressure controlled by the meter-out spool valve. Since it is configured to be controlled by the above, it is possible to reliably prevent hunting that was easy to occur in the past, and realize smoother operation of the hydraulic actuator compared to the conventional one.
Further, there is an effect that the durability of the entire circuit can be improved.

Further, the control valve of the present invention can be applied to the above-mentioned hydraulic drive system, and the whole is compact and easy to handle.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic drive system and a control valve of the present invention.

FIG. 2 is a diagram showing characteristics obtained in the embodiment shown in FIG.

FIG. 3 is a block diagram showing a control system of the embodiment shown in FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an example of a conventional hydraulic drive device that drives a hydraulic actuator in which the direction of load pressure changes.

[Explanation of symbols]

1 Meter-in spool 2 Meter-out spool 3 Valve body 4a Pressure compensation valve 4b Pressure compensation valve 5 Pressure sensor 10 Electromagnetic actuator 11 Electromagnetic actuator 20a Control oil passage 20b Control oil passage 21a Control oil passage 21b Control oil passage 22 Pump port 24 Multiplier 25 subtractor 26 subtractor 27 subtractor 32 traveling motor (hydraulic actuator) 50 differential pressure sensor 60 spool position sensor 65 pump discharge pressure sensor 70 calculator 80 calculator 90 multiplier C ₁ load passage C ₂ load passage P ₁ load pressure Qc Command flow rate P ₁₀ Meter-in command pressure T Tank port α Flow rate gain β Pressure gain

[Procedure amendment]

[Submission date] January 27, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (6)

[Claims] 1. A hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, flow rate control means for controlling a flow rate of the pressure oil supplied to the hydraulic actuator, and a supply side of the hydraulic actuator. In the hydraulic drive device including pressure control means for controlling the pressure of the pressure control means, the flow rate control means is a meter-in spool valve arranged between the hydraulic pump and the hydraulic actuator, and the pressure control means is the hydraulic actuator. A meter-out spool valve disposed between the tank and the tank, and the meter-in spool valve opening corresponding to the magnitude of the pressure on the supply side of the hydraulic actuator controlled by the meter-out spool valve. A hydraulic drive device comprising an opening control means for controlling the. 2. The hydraulic drive according to claim 1, wherein a pressure compensating valve is provided on the discharge side of the meter-in spool valve, the pressure compensating valve being driven according to the differential pressure between the pump discharge pressure and the maximum load pressure of the circuit. apparatus. 3. The opening degree of the meter-in spool valve so as to match a predetermined command flow rate in accordance with the differential pressure between the pump discharge pressure and the load pressure on the supply side of the hydraulic actuator, and the spool displacement of the meter-in spool valve. The hydraulic drive system according to claim 1, further comprising a flow rate feedback means for controlling the above. 4. A pressure sensor for detecting a load pressure on a supply side of a hydraulic actuator, and means for controlling driving of a meter-out spool valve according to a signal output from the pressure sensor. The hydraulic drive system according to claim 1. 5. A differential pressure sensor for detecting the differential pressure between the pump discharge pressure and the load pressure on the supply side of the hydraulic actuator, a pump discharge pressure sensor for detecting the discharge pressure of the hydraulic pump, the differential pressure sensor, and pump discharge. The present invention is characterized by including a calculating means for obtaining a load pressure on the supply side of the hydraulic actuator from a signal output from the pressure sensor, and a means for controlling the drive of the meter-out spool valve according to the load pressure obtained by the calculating means. The hydraulic drive system according to claim 1 or 3. 6. A meter-in spool valve, which is arranged in one valve body between a hydraulic pump and a hydraulic actuator and controls the flow rate of pressure oil supplied to the hydraulic actuator, the hydraulic actuator and a tank. And a meter-out spool valve that controls the pressure on the supply side of the hydraulic actuator.