JP2000018209A - Hydraulic control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize superior responsiveness, with pilot operation for a control valve using a highly reliable remote control valve carried out. SOLUTION: This hydraulic control system guides the secondary pressure of a remote control valve 22 serving as pilot pressure to the pilot ports 14a, 14b of a control valve 14 consisting of a hydraulic pilot type selector valve. In addition to the remote control valve 22, a dither pressure generating means consisting of an electromagnetic valve 32 and the like is provided. The means applies dither to the control valve 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for switching a hydraulic pilot type switching valve by a secondary pressure of a manually operated remote control valve (so-called remote control valve).

[0002]

2. Description of the Related Art Conventionally, as a switching valve used as a control valve in a hydraulic excavator, a hydraulic crane, and the like,
2. Description of the Related Art A so-called direct-acting spool switching valve that is switched directly by an operator's lever operation is well known. However, in such a switching valve, when the power due to the hydraulic pressure increases, the operating force required to switch the control valve also increases, which disadvantageously increases the burden on the operator.

Therefore, in recent years, a hydraulic pilot type switching valve has been used as the control valve, and the switching valve is pilot operated by the secondary pressure of a remote control valve (so-called remote control valve) manually operated by an operator. Is being developed. According to such a device, since the switching valve is switched by the hydraulic pilot,
The burden on the operator is reduced. In addition, since electric means is not used for switching the switching valve, there is an advantage that operation can be reliably performed even if the power supply voltage is reduced, and that the cost is low.

[0004]

In the hydraulic pilot type control circuit as described above, it is preferable that the pilot pressure applied to the switching valve and the spool stroke correspond completely one to one. However, in reality, the static friction force acts on the spool of the switching valve when the pilot pressure rises, so that the operation of the spool is delayed by that much, and the actual pilot pressure and the spool stroke are shown in FIG. Hysteresis α as shown occurs. For this reason, if the operator operates the operating lever in a pattern as shown in FIG. 7A, for example, the pilot pressure changes as shown in FIG. As shown in FIG. 10C, the operation is delayed by the dead zone due to the hysteresis α. That is, a dead time dt as shown in FIG. As a result, a response delay occurs in the actuator controlled by the switching valve, resulting in a disadvantage that the operability is lower than that of the direct-acting type.

[0005] Japanese Patent Application Laid-Open No. 5-79503 discloses that
An electromagnetic proportional pressure reducing valve for electrically controlling the pilot pressure is provided in the pilot line, and an electric signal of an appropriate frequency is input thereto to dither the pilot pressure, thereby reducing the frictional force of the spool. There is disclosed an actuator in which the response of the actuator is improved. However, as shown in this publication, a hydraulic circuit that operates a pilot pressure by an electromagnetic proportional pressure reducing valve is different from a pilot circuit operated by a secondary pressure of a remote control valve as described above,
If the power supply voltage drops and the electromagnetic proportional pressure reducing valve does not operate, there is a disadvantage that the pilot operation cannot be performed.

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a hydraulic control device capable of realizing excellent responsiveness while performing pilot operation of a control valve by a highly reliable remote control valve. And

[0007]

As a means for solving the above problems, the present invention provides a control valve comprising a hydraulic pilot type switching valve for controlling a state of supply of hydraulic oil to a hydraulic actuator; A remote control valve for generating a secondary pressure according to the operation amount, a hydraulic control device in which the secondary pressure of the remote control valve is input as a pilot pressure to a pilot port of the control valve, And a dither pressure generating means for generating hydraulic oil pressure for applying dither to the control valve, wherein the pressure generated by the dither pressure generating means is input to the pilot port. Things.

According to this configuration, since the dither pressure is input to the pilot port of the control valve from a path different from that of the remote control valve, the application of the dither reduces the frictional force acting on the spool of the control valve. I do. As a result, the hysteresis of the pilot pressure-spool stroke characteristic is improved, and the response of the actuator is improved. Further, even if the dither pressure generating means does not operate due to a failure or the like, the pilot operation of the control valve by the remote control valve can be continued, and high reliability is secured.

Specifically, when the control valve is provided with a pair of pilot ports for pilot-operating the spool from opposite directions, a high-pressure selection valve is provided for each pilot port and the high-pressure selection valve is provided. The outlet may be connected to the pilot port, a common remote control valve may be connected to one inlet of each high pressure selection valve, and a common dither pressure generating means may be connected to the other inlet.
In this configuration, when a pilot pressure higher than the dither pressure is supplied to one of the pilot ports, the pilot pressure is selected to be high, and the spool operates. Is applied. Further, even if the dither pressure generating means becomes inoperable, the pilot pressure generated by the remote control valve is reliably input to the pilot port via the high pressure selection valve.

The dither pressure generating means includes a dither generating hydraulic source, an electromagnetic valve provided between the dither generating hydraulic source and the pressure selecting means, and an electric signal for generating dither is input to the electromagnetic valve. It is preferable that the signal input means is provided. In this case, by using a common hydraulic pressure source for the dither generation hydraulic pressure source and the pilot hydraulic pressure source, the configuration of the entire apparatus can be simplified.

The average value and amplitude of the dither pressure generated by the dither pressure generating means may be set as appropriate.
When air is mixed into the hydraulic oil, the amplitude of the dither pressure becomes smaller by that amount, and there is a possibility that sufficient hysteresis improvement cannot be realized. However, by configuring the control valve such that an oil path connecting the pilot port to the tank is formed in a state where the spool of the control valve is in the neutral position, the hydraulic oil supplied into the pilot port is formed. Can be released into the tank, whereby a sufficient dither effect can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described with reference to FIGS.

The hydraulic control device shown in FIG. 1 includes a hydraulic pump 10 as a hydraulic power source and a hydraulic actuator (a hydraulic cylinder 12 in the illustrated example), and a control valve 14 is provided between the two.

The control valve 14 comprises a three-position hydraulic pilot type switching valve in the figure, and has a pair of pilot ports 14a and 14b for inputting pilot pressure to the spool from opposite directions. Have. And any pilot port 14
In a state where the pilot pressure is not supplied to the hydraulic cylinders 12a and 14b, a neutral position (center position in the drawing) for blocking both the head side chamber and the rod side chamber of the hydraulic cylinder 12 is maintained, while the pilot pressure is supplied to the pilot port 14a. When the pilot pressure is supplied to the pilot port 14b, the hydraulic pump 10 is switched to the position (left position in the figure) for guiding the discharge oil of the hydraulic pump 10 to the rod side chamber. (The right position in the figure) for guiding the discharged oil. The control valve 14 is configured so that the spool stroke increases as the pilot pressure increases.

In FIG. 1, reference numeral 16 denotes a main relief valve.

In this apparatus, a pilot hydraulic pressure source 18 and a remote control valve (remote control valve) 20 are provided as means for supplying and adjusting the pilot pressure. The remote control valve 20 includes a lever 22 manually operated by an operator or the like, a cam 23 interlocked with the lever 22, a pair of left and right spools 24A operated by the cam 23,
24B, and the pilot hydraulic pressure source 18 is connected to the inlet ports of the spools 24A, 24B. When the lever 22 is in the neutral position in the figure, no secondary pressure is generated in the spools 24A and 24B, and when the lever 22 is operated in the direction of the arrow A or in the direction of the arrow B, the amount of operation depends on the operation amount. The remote control valve 20 is configured such that the cam 23 is tilted by the amount to generate a secondary pressure of the spool 24A or the spool 24B corresponding to the operation amount.

FIG. 2 shows the relationship between the operation amount of the lever 22 (lever stroke) and the secondary pressure (pilot pressure) of the spools 24A and 24B. This remote control valve 2
At 0, the pilot pressure does not rise until the lever stroke reaches a predetermined minute value R1.
, A pilot pressure P1 is generated. In a region where the lever stroke is larger than the minute value R1, a pilot pressure P that is substantially proportional to the lever stroke R is generated.

The secondary pressure of the spool 24A is
A is connected to a shuttle valve 28A, which is a high-pressure selection valve, via A.
A is introduced into the pilot port 14a via A as pilot pressure. Similarly, the secondary pressure of the spool 24B is
Shuttle valve 28B which is a high-pressure selection valve via oil passage 26B
When a high pressure is selected by the shuttle valve 28B, the pilot pressure is introduced into the pilot port 14b via the oil passage 30B as pilot pressure. Therefore, with the operation of the lever 22, a pilot pressure corresponding to the operation amount is supplied to the pilot port 14a or the pilot port 14b.

Further, this device is provided with an electromagnetic proportional valve (electromagnetic proportional pressure reducing valve) 32 as a dither pressure generating means. The inlet port of the electromagnetic proportional valve 32 is connected to the pilot hydraulic pressure source 18. The outlet port is connected to the shuttle valve 28A via the oil passage 34A, and at the same time, is connected to the shuttle valve 28B via the hydraulic pressure 34B. When the secondary pressure of the electromagnetic proportional valve 32 is selected to be high by the shuttle valve 28A or the shuttle valve 28B, the secondary pressure is transmitted through the oil passage 30A or 30B to the pilot port 14a or the pilot port 14a.
b.

A controller (signal input means) 36 is connected to the solenoid 32a of the electromagnetic proportional valve 32. Then, the controller 36 sends the solenoid 32
When an electric signal having an appropriate frequency is input to a, a hydraulic oil pressure for applying dither (hereinafter, referred to as dither pressure) is generated on the secondary side of the electromagnetic proportional valve 32. I have. As shown in FIG. 3, the waveform of the dither pressure is set to a waveform oscillating at an amplitude ΔP with a pressure P0 smaller than the pressure value P1 (ie, a minimum pilot pressure at which the spool of the control valve 14 operates) as an average pressure. And its maximum pressure (= P
0 + ΔP) is set to be smaller than the pressure value P1.

Next, the operation of this device will be described.

First, when the lever 22 of the remote control valve 20 is in the neutral position, no pilot pressure is generated in any of the oil passages 26A, 26B connected to the spools 24A, 24B. On the other hand, since a small dither pressure is generated in the secondary oil passages 34A and 34B of the electromagnetic proportional valve 32, this dither pressure is applied to the shuttle valves 28A and 28B.
At the same time, and is supplied to both pilot ports 14a and 14b simultaneously. Therefore, the spool of the control valve 14 receives the dither pressure from both sides, but this pressure is very small, and the spool is stopped at the neutral position because equal pressure acts on the spool from both sides in opposite directions. Keep state.

On the other hand, when the lever 22 is rotated, for example, in the direction of arrow A in FIG. 1, the secondary pressure of the spool 24A (ie, the pressure in the oil passage 26A) rises, and this secondary pressure is increased. When the pressure exceeds the dither pressure, the secondary pressure is selected to be high by the shuttle valve 28A, and the pilot port 14
is input to a. On the other hand, the secondary oil passage 2 of the spool 24B
Since the pressure has not risen at 6B, the dither pressure from the electromagnetic proportional valve 32 is still input to the pilot port 14b. As a result, control valve 1
The spool 4 has an average pressure of (P2−P0), and a pilot pressure to which a dither component having an amplitude ΔP is added is applied. Due to this dither component, the frictional force of the spool is reduced, and the hysteresis α shown in FIGS. 6 and 7 is eliminated or greatly reduced. As a result, the dead time dt of the spool movement when the pilot pressure input to the pilot port 14a rises is shown.
Is reduced to a negligible level, and the responsiveness of the actuator (the hydraulic cylinder 12 in the illustrated example) also increases.

Further, in this device, a dither pressure is generated in a route different from the pilot line in which the remote control valve 20 is provided, and the dither pressure and the pilot pressure generated by the remote control valve 20 are selected to a high pressure to select a pilot port. 14a and 14b, the power supply voltage of the controller 36 temporarily drops and the electromagnetic proportional valve 32
Even if a malfunction occurs, the pilot operation of the control valve 14 by the lever 22 can be continued without any trouble, and high reliability is secured.

In the present invention, the detailed structure of the control valve 14 is not particularly limited. However, FIG.
As shown in (a) and (b), when air is mixed in the pilot oil ((b) in the same drawing), the dither pressure waveform has a lower waveform than when no air is mixed ((a) in the same drawing). Since there is a disadvantage that the amplitude is weakened, it is more preferable to provide the control valve 14 with a function of releasing such air into the tank.

FIGS. 5A and 5B show an example of a structure for that purpose.
Shown in In the figure, the pilot port 14a (14
A spool pressing chamber 40 is formed at the back side of b), and the end of the spool 46 faces inside the spool pressing chamber 40. Further, a tank oil passage 44 communicating with the tank is formed further inside the spool pressing chamber 40, and a through hole 42 connecting the two is formed between the tank oil passage 44 and the spool pressing chamber 40. I have.

In a normal control valve, the through hole 42 is always closed by the spool 46 and the spool pressing chamber 4
0 and the oil passage 44 are always isolated from each other. In the control valve 14 shown in this figure, a small diameter having an outer diameter smaller than the diameter of the through hole 42 is provided at an appropriate position of the spool 46. A portion 46a is formed. When the spool 46 is in the neutral position as shown in FIG. 5A, the small diameter portion 46a enters the through hole 42, and the spool pressing chamber 40 and the tank oil passage 44 communicate with each other through the through hole 42. Then, as shown in FIG.
The portion of the spool 46 other than the small-diameter portion 46a is fitted into the through hole 42 at the time when is pressed inward from the neutral position to close the through hole 42.

According to such a structure, while the spool 46 is in the neutral position, the spool pressing chamber 40 is in communication with the tank oil passage 44, so that air is mixed in the pilot oil supplied to the pilot port 38. However, the air escapes to the tank through the through hole 42 and the tank oil passage 44, thereby maintaining a good dither pressure waveform. On the other hand, when the spool 46 starts the stroke from the neutral position, the small-diameter portion 4
The spool pressing chamber 40 and the tank oil passage 44 are isolated from each other by the large-diameter portion other than the pilot port 38a.
Is reliably applied to the spool 40, and the spool 40 operates faithfully with a stroke corresponding to the pilot pressure.

In the above embodiment, the pilot hydraulic pressure source 18 is used as the dither pressure generating hydraulic pressure source. However, these hydraulic pressure sources may be separately prepared.

[0030]

As described above, the present invention comprises a control valve for controlling the supply state of hydraulic oil to the hydraulic actuator and a secondary pressure corresponding to the operation amount of the operation member, which is constituted by a hydraulic pilot type switching valve. And a remote control valve for causing
In a hydraulic control device in which the secondary pressure of the remote control valve is input as a pilot pressure to a pilot port of the control valve, dither pressure is generated by dither pressure generation means provided separately from the remote control valve, and this pressure is generated. Since the input is made to the pilot port, the dither is applied to the control valve to improve the responsiveness of the actuator while ensuring high reliability by performing the pilot operation of the control valve by the remote control valve. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an overall configuration of a hydraulic control device according to the present invention.

FIG. 2 is a graph showing a lever stroke-pilot pressure characteristic of a remote control valve provided in the hydraulic control device.

FIG. 3 is a graph showing a dither pressure waveform formed in the hydraulic control device.

4A is a graph showing a dither pressure waveform when air is not mixed in hydraulic oil, and FIG. 4B is a graph showing a dither pressure waveform when air is mixed in hydraulic oil. is there.

FIG. 5A is a cross-sectional view showing a pilot port of a control valve in the hydraulic control device, showing a state where a spool is in a neutral position, and FIG. 5B is a cross-sectional view of the pilot port, FIG. 7 is a diagram showing a state in which the device is operating from a neutral position.

FIG. 6 shows pilot pressure in a conventional spool switching valve.
5 is a graph showing spool stroke characteristics.

FIGS. 7A, 7B, and 7C are graphs showing a time change of a lever operation amount, a pilot pressure, and a spool stroke in a conventional hydraulic control device.

[Explanation of symbols]

 Reference Signs List 10 hydraulic pump 12 hydraulic cylinder (hydraulic actuator) 14 control valve 14a, 14b pilot port 18 pilot hydraulic source 20 remote control valve (remote control valve) 28A, 28B shuttle valve (high pressure selection valve) 32 electromagnetic proportional valve 36 controller (signal input means) ) 40 Spool pressing chamber 42 Through hole 44 Tank oil passage 46 Spool

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoki Kanno 1-5-5 Takatsukadai, Nishi-ku, Kobe, Japan Inside Kobe Research Institute, Kobe Steel Ltd. No.5 No.5 F-term in Kobe Steel, Ltd. Kobe Research Institute (Reference) 3H002 BA01 BB06 BC01 BD04 BE06 5H316 AA06 BB09 CC03 DD03 EE02 EE08 EE17 ES01 HH01 HH14 JJ03 JJ15 LL01

Claims (5)

[Claims] 1. A control valve comprising a hydraulic pilot type switching valve for controlling a state of supply of hydraulic oil to a hydraulic actuator, and a remote control valve for generating a secondary pressure according to an operation amount of an operation member, In a hydraulic control device in which a secondary pressure of the remote control valve is input as a pilot pressure to a pilot port of the control valve, a hydraulic oil pressure provided separately from the remote control valve and for applying dither to the control valve A hydraulic pressure control device comprising: a dither pressure generating means for generating pressure; and a pressure generated by the dither pressure generating means is input to the pilot port. 2. The hydraulic control device according to claim 1, wherein
The control valve is provided with a pair of pilot ports for piloting the spool from opposite directions, and a high-pressure selection valve is provided for each pilot port, and the outlet of the high-pressure selection valve is connected to the pilot port. A hydraulic control device, wherein a common remote control valve is connected to one inlet of a high pressure selection valve, and a common dither pressure generating means is connected to the other inlet. 3. The hydraulic control device according to claim 2, wherein
As the dither pressure generating means, a dither generating hydraulic source, an electromagnetic valve provided between the dither generating hydraulic source and the high pressure selection valve, and a signal input means for inputting an electric signal for dither generation to the electromagnetic valve A hydraulic control device comprising: 4. The hydraulic control device according to claim 3, wherein
A hydraulic control device using a common hydraulic pressure source for the dither generation hydraulic pressure source and the pilot hydraulic pressure source. 5. The hydraulic control device according to claim 1, wherein an oil passage that connects the pilot port to a tank is formed when a spool of the control valve is in a neutral position. A hydraulic control device comprising a control valve.