JPS6314231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hydraulic system, and in particular to a motor for maintaining a hydraulic motor in a stopped state in a hydraulic system that drives a load with large inertia such as a rotating body of a hydraulic excavator. The present invention relates to a control device capable of automatically operating a stopping means.

In general, in hydraulic systems in which a hydraulic motor drives a load with large inertia, such as the revolving body of a hydraulic excavator, the motor stopping means that keeps the hydraulic motor in a stopped state is automatically installed without causing wear or damage. In order to operate the hydraulic motor, it is necessary to detect whether the hydraulic motor is stopped or at a speed close to a stopped state. The following, for example, has been proposed as a conventional control device equipped with this type of detection means. That is, (1) A hydraulic pump other than the hydraulic pump that operates the hydraulic motor is connected to the output shaft of the hydraulic motor that operates the load, and the rotational state of the hydraulic motor is detected by the discharged pressure oil. control device.

(2) A throttle valve is installed either before or after the main pipe in which the hydraulic motor is installed, and the flow of pressure oil in the main pipe is detected by the pressure difference between the throttle valves and the hydraulic motor is rotated. A control device that knows the status.

(3) A system designed to detect the relief state of the crossover relief valves installed before and after the hydraulic motor in the main pipeline where the hydraulic motor is installed. In other words, depending on the pumping state of the hydraulic motor,
A control device that detects the rotational state of this hydraulic motor.

However, in the case of the control device (1) above, the structure is complicated and expensive as it requires a separate hydraulic pump, and there is also a problem of power loss. Since the throttle valve is installed in the valve, there is a problem that the power loss due to the pressure loss becomes large, and in the case of the control device (3), crossover in the small flow rate range generally makes the operation of the relief valve unstable. Since it depends on the characteristics of the relief valve, there is a problem that accurate detection results cannot be obtained.

Conventionally, in hydraulic closed circuits, there has been a control device that operates a motor stopping means that keeps a hydraulic motor in a stopped state only when a control lever that adjusts the discharge capacity of a variable displacement hydraulic pump is in a neutral position. Although it has been proposed, when driving a load with large inertia, even if the control lever is in the neutral position, the hydraulic motor may continue to rotate while being relieved by the crossover relief valve. In order to prevent the motor stopping means from operating in this state, a predetermined delay time has conventionally been provided between when the control lever returns to the neutral position and when the motor stopping means starts operating. . This delay time is obtained, for example, by providing a throttle valve on the pipe for operating the motor stop means. However, such a system in which the delay time is set using a throttle valve is inconvenient because the delay time changes due to a significant change in the viscosity of the hydraulic oil due to a change in the temperature of the hydraulic oil. Furthermore, in cases where the magnitude of the inertia of the load applied to the hydraulic motor changes significantly depending on the load and position of the earthmoving machine, such as the revolving body of a hydraulic excavator, Since the duration time of the relief state of the crossover relief valve described above varies significantly, the above delay time is set so that the motor stopping means operates immediately after the hydraulic motor has substantially stopped in compliance with all of these conditions. It is difficult to configure.

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to automatically operate a motor stopping means for holding a hydraulic motor in a stopped state immediately after the hydraulic motor is stopped. An object of the present invention is to provide a control device for a hydraulic system.

In order to achieve this object, the present invention constitutes a hydraulic closed circuit with a variable displacement hydraulic pump and a hydraulic motor, and is provided with a control valve that controls a hydraulic servo mechanism that controls the discharge capacity of the variable displacement hydraulic pump. , this control valve controls the hydraulic servo mechanism according to the pressure of the main pipe connecting the variable displacement hydraulic pump and the hydraulic motor, and also releases the operation of the motor stopping means that holds the hydraulic motor in a stopped state. a first pressure transmission means that transmits the control pressure in accordance with the pressure on the output side of the servo valve constituting the hydraulic servo mechanism; and a second pressure transmission means for transmitting control pressure in connection with the operation of the input means of the hydraulic servomechanism, and the motor is stopped by the operation of at least one of the first pressure transmission means and the second pressure transmission means. The apparatus is configured to deactivate the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydraulic system control device of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a first embodiment of the present invention. In the figure, 1 is a variable displacement hydraulic pump, and 2 is this variable displacement hydraulic pump 1.
Hydraulic motor 3 is driven by hydraulic motor 2.
It is a load operated by The variable displacement hydraulic pump 1 and hydraulic motor 2 described above constitute a hydraulic closed circuit. 16 is a charge hydraulic source that supplies charge pressure oil to this closed circuit; 4 is a hydraulic pump 1;
A check valve 5 is a flushing valve interposed between the main pipe connecting the hydraulic motor 2 and the charge hydraulic pressure source 16. This flushing valve 5 discharges a surplus flow rate corresponding to the charge flow rate from the charge hydraulic power source 16 from the low-pressure side main pipe. Reference numeral 6 denotes a relief valve provided downstream of the flushing valve 5, which sets the minimum pressure of the closed circuit. 7 is a crossover relief valve that sets the maximum pressure in the closed circuit. A check valve 8 supplies hydraulic oil from a tank to the closed circuit when there is no charge from the charge hydraulic power source 16. A servo cylinder 9 operates a discharge capacity adjustment member of the variable displacement hydraulic pump 1. A servo valve 10 controls the servo cylinder 9 in accordance with the operation of an input means such as a control lever 10a. These servo cylinder 9 and servo valve 10 constitute a hydraulic servo mechanism that controls the discharge capacity of the variable displacement hydraulic pump 1. Reference numeral 20 indicates motor stopping means, such as a brake device, for holding the hydraulic motor 2 in a stopped state, and reference numeral 17 indicates a hydraulic power source that supplies control pressure to release the operation of the brake device 20. 11
is a control valve that controls the above-mentioned hydraulic servo mechanism,
Control valve 11 is in communication with a hydraulic power source 17. 12 is a shuttle valve, and the shuttle valve 12 takes out the pressure in the main pipeline on the high pressure side and guides it to the pilot port of the control valve 11. As shown in FIG. 3, when the output side pressure p ₁ of the shuttle valve 12, that is, the pilot pressure of the control valve 11, is lower than the pressure p _1a , the control valve 11 is in position a, and the output of the control valve 11 is lower than the pressure p 1a. The side pressure p ₂ is equal to the discharge pressure p ₃ of the hydraulic source 17, but the pressure
When p ₁ becomes higher than the pressure p _1a , the control valve 11 is in the intermediate position b, and the pressure p ₂ becomes lower as the pressure p ₁ becomes higher. 13 and 14 are switching valves installed in parallel in the middle of a pipe connecting the hydraulic power source 17 and the brake device 20; 22 is a shuttle valve built into the hydraulic servo mechanism; the switching valve 13 operates the servo valve 10; The switching valve 14 operates in conjunction with the operating lever 10a, which operates using the output side pressure of the shuttle valve 22, that is, the output side pressure _p4 of the servo valve 10, as a pilot pressure, so that the pressure _p4 is slightly higher than the tank pressure.
When the pressure becomes lower than p ₅ , the switching valve 14 becomes position a, and when the pressure p ₄ becomes higher than the pressure p ₅ , the switching valve 14
becomes position b. 15 is a shuttle valve, and the shuttle valve 15 selects the higher pressure among the pressures from the switching valves 13 and 14. The switching valve 14 constitutes a first pressure transmitting means for transmitting the control pressure from the hydraulic source 17 to the brake device 20 according to the pressure _p4 , and the switching valve 13 constitutes a first pressure transmitting means for transmitting the control pressure from the hydraulic source 17 to the brake device 20 according to the pressure p4, and the switching valve 13 is connected to the control lever 10a of the hydraulic servo mechanism. It constitutes a second pressure transmission means for transmitting control pressure from the hydraulic power source 17 to the brake device 20 in connection with the operation. A check valve 18 is provided in a pipe connecting the shuttle valve 15 and the brake device 20, and the check valve 18 allows flow from the shuttle valve 15 to the brake device 20. 19 is a throttle valve installed in parallel with the check valve 18;
For example, from the time when both the switching valve 13 and the switching valve 14 communicate the brake device 20 with the tank,
After a delay of 0.2 to 0.3 seconds, the brake device 20 is activated.

FIG. 2 is a diagram showing the configuration of the hydraulic servo mechanism of the control device shown in FIG. 1. In the figure, 9c is a piston of the servo cylinder 9, 9a and 9b are cylinder chambers of the servo cylinder 9, 9d is a piston rod of the servo cylinder 9, and the piston rod 9d is connected to the swash plate of the hydraulic pump 1. 10b is a spool of the servo valve 10, and the spool 10b is connected to the operating lever 10a. 10c is a sleeve of the servo valve 10, 30 is a link connected to the sleeve 10c, 31 is a link whose central portion is rotatably supported, and a piston rod 9d and the link 30 are connected to both ends of the link 31.

In this hydraulic servo mechanism, the operating lever 1
When 0a is operated, the spool 10b moves to the left, pressure oil from the hydraulic source 17 is supplied to the cylinder chamber 9a, and the piston 9c moves to the right.
The discharge capacity of the hydraulic pump 1 increases, and the piston 9
When the sleeve 10c moves to the left in accordance with the rightward movement of the sleeve 10c, and the amount of movement of the sleeve 10c becomes the same as the amount of movement of the spool 10b, the servo valve 10 closes and the pressure oil from the hydraulic source 17 flows into the cylinder chamber 9a. The piston 9c stops at that position, and the discharge capacity of the hydraulic pump 1 becomes a value corresponding to the operating amount of the operating lever 10a. In this state, the operating lever 10a
When the spool 10b is returned to the neutral position, the spool 10b moves to the right,
Since pressure oil from the hydraulic source 17 is supplied to the cylinder chamber 9b, the piston 9c moves to the left, so the discharge capacity of the hydraulic pump 1 decreases, and the sleeve 10c moves to the right in response to the leftward movement of the piston 9c. , sleeve 1
When 0c returns to the neutral position, the servo valve 10 closes, the pressure oil of the hydraulic pressure reducer 17 is no longer supplied to the cylinder chamber 9b, the piston 9c stops at that position, and the discharge capacity of the hydraulic pump 1 becomes zero. becomes.

Next, the operation of the control device shown in FIG. 1 will be explained.

First, when accelerating the hydraulic motor, when the operating lever 10a of the servo valve 10 is operated, the switching valve 13 is switched, and pressure oil from the hydraulic source 17 is immediately supplied to the brake device 20 via the check valve 18. Therefore, the braking action is released, and as described above, the servo piston 9c of the servo cylinder 9 moves, and the discharge flow rate Q of the hydraulic pump 1 increases. Here, if the capacity of the hydraulic motor 2 is D _n , the rotational speed of the hydraulic motor 2 is ω _n , and the moment of inertia of the load 3 is J (note that the pressure in the main pipe on the discharge side of the hydraulic pump 1 is p ₁ ), Equations (1) and (2) hold true.

Q=D _n ·ω _n (1) Jdω _n /dt=D _n ·p ₁ (2) Equation (3) is obtained by rearranging equations (1) and (2).

p ₁ =J/D _n ² ·dQ/dt (3) Since the moment of inertia J and the capacity D _n are constant, the pressure p ₁ is proportional to dQ/dt. Further, if the rotation speed of the drive shaft of the hydraulic pump 1 is constant, the flow rate Q has a value depending on the position of the servo piston 9c, so dQ/dt is proportional to the speed v of the servo piston 9c. Therefore, as shown by line a in Figure 4,
Pressure P ₁ is proportional to velocity v. Furthermore, as described above, as shown in FIG. 3, when the pressure p ₁ is lower than the pressure p _1a , the output side pressure p ₂ of the control valve 11 is equal to the pressure p ₃ , but when the pressure p ₁ is lower than the pressure p _1a , As the pressure increases, the pressure p ₂ decreases, and the velocity v has a value corresponding to the pressure p ₂ , so as shown by line b in Figure 4,
When the pressure p ₁ is lower than the pressure p _1a , the velocity v is the velocity v ₁ according to the pressure p ₃ , but when the pressure p ₁ is lower than the pressure p _1a
Higher, the velocity v decreases as the pressure p ₂ decreases. Therefore, the pressure _p1 increases, and the pressure at the intersection of line a and line b, that is, the set pressure of control valve 11
When p _1b is reached, the relationship between pressure p ₁ and velocity v is balanced, and from then on, pressure p ₁ is kept at pressure p _1b and velocity v is kept at velocity v ₂ . That is, the pressure p ₁ is the pressure
When it becomes higher than p _1b , the velocity v becomes smaller than the velocity v ₂ , so the pressure p ₁ decreases, and the pressure p ₁ becomes the pressure
When it becomes lower than p _1b , the velocity v becomes greater than the velocity v ₂ , so the pressure p ₁ increases, so that the pressure p ₁ is eventually kept at the pressure p _1b and the velocity v is kept at the velocity v ₂ . From the above, when operating the operating lever 10a, as shown in FIG. 5, the pressure p ₁ immediately after the operation is low, so the velocity v is large and the flow rate Q increases rapidly, and as a result, the pressure p ₁ increases. Although it rises rapidly,
When the pressure p ₁ reaches p _1b , the velocity v is kept at v ₂ ,
The flow rate Q increases linearly and the pressure p ₁ is kept at the pressure p _1b . Then, when the flow rate Q reaches a value corresponding to the amount of operation of the operating lever 10a, the servo valve 10 is closed and the flow rate Q is maintained at that value thereafter, so that the pressure _p1 decreases rapidly.

Also, during a hydraulic motor deceleration operation, that is, an operation in which the operating lever 10a of the servo valve 10 is held at a constant operating position and the operating lever 10a is returned to the neutral position from a steady state in which the hydraulic motor 2 is rotating at a constant speed. When the operation lever 10a is returned to the neutral position, the switching valve 13 returns to the neutral position, and the brake device 20 is communicated with the tank via the switching valve 13. 4
Since the relationship shown in the figure, that is, the relationship between pressure p ₁ (pressure in the suction side main pipe of the hydraulic pump 1) and speed v holds, as shown in FIG. 6, the pressure p ₁ immediately after operation is low, so the speed v is large, the flow rate Q decreases rapidly, and as a result, the pressure p ₁ increases rapidly. In this case, immediately after returning the operating lever 10a to the neutral position, the brake device 20 is communicated with the tank via the switching valve 13 and the switching valve 14, but since the servo valve 10 is open, the pressure _p4 is Immediately pressure p ₅
Since the switching valve 14 is switched to the b position, pressure oil from the hydraulic source 17 is supplied to the brake device 20 via the switching valve 14, and the time during this period is 0.2 seconds.
Therefore, the brake device 20 is held in the released state by the throttle valve 19. And the pressure
When p ₁ reaches p _1b , the velocity v is kept at v ₂ , the flow rate Q decreases linearly, and the pressure p ₁ is kept at p _1b .
Then, when the flow rate Q becomes zero, the hydraulic motor 2
In this case, the servo valve 10 is closed, and the pressure _p4 becomes lower than the pressure _p5 , so the switching valve 14 immediately switches to position a, and the brake device 2
0 is communicated to the tank via the switching valve 13 and the switching valve 14, so the brake device 20 is quickly activated.

In this way, the control device of the above embodiment allows the hydraulic motor 2 to be in a substantially stopped state not only when operating the operating lever 10a of the servo valve 10 but also when the operating lever 10a is returned to the neutral position. It is possible to release the braking action of the brake device 20 until the moment when I won't receive it. Furthermore, if the set pressure p _r of the crossover relief valve 7 is set higher than the pressure p _1b , power loss or heat generation due to relief will not occur during acceleration or deceleration.

FIG. 7 is a circuit diagram showing the configuration of a second embodiment of the present invention. Note that the same members as those shown in FIG. 1 above are designated by the same reference numerals. In FIG. 7, reference numeral 21 denotes a motor stop means for keeping the hydraulic motor 2 in a stopped state, such as an on-off valve, which is provided on the main pipe connecting the variable displacement hydraulic pump 1 and the hydraulic motor 2, and is connected to the hydraulic source 17. I have contacted you. Reference numeral 23 denotes an input means of the servo valve 10, for example a pilot valve, which outputs pilot pressure according to the amount of operation of the operating lever, and uses this pilot pressure to control the servo valve 1.
Activate 0. 24 is a shuttle valve that takes out pressure from the pilot valve 23. These pilot valve 23 and shuttle valve 24 are the on-off valve 21
The hydraulic pressure source 17 is interposed on a pipe connecting the hydraulic pressure source 17 and the hydraulic pressure source 17. 25 is a shuttle valve, shuttle valves 22, 24
The pressure is removed from the valve and the on-off valve 21 is operated.
The aforementioned shuttle valve 22 is a first valve that transmits control pressure from the hydraulic source 17 to the on-off valve 21 in accordance with the pressure on the output side of the servo valve 10 constituting the hydraulic servo mechanism.
The shuttle valve 24 transmits the control pressure from the hydraulic source 17 to the on-off valve 21 in connection with the operation of the input means of the hydraulic servomechanism, that is, the pilot valve 23. It constitutes a second pressure transmission means that can be communicated with the tank via. Note that the crossover relief valve 7 is provided closer to the hydraulic motor 2 than the on-off valve 21.

In the control device configured in this manner, when the hydraulic motor is accelerated, the shuttle valve 24,
Since control pressure oil is supplied to the on-off valve 21 via the shuttle valve 25 and check valve 18, the on-off valve 21
makes the main pipe conductive, and pilot pressure from the pilot valve 23 acts on the servo valve 10, thereby operating the hydraulic servo mechanism. Further, when the hydraulic motor is decelerated, the pressure in the suction side main pipe is controlled to a set value by the control valve 11 as in the first embodiment. Furthermore, when the operating lever is returned to the neutral position, the pilot valve 23 also returns to the state shown in FIG.
1 is connected to the tank. However, while the servo valve 10 is in the switching state, that is, when the hydraulic motor 2 is not completely stopped, the servo valve 10, shuttle valve 22, shuttle valve 25, and check valve 18 are used to open and close the valve. Control pressure oil is supplied to the valve 21 from the hydraulic pressure reducer 17, so that the on-off valve 21 maintains the main line in a conductive state. When the servo valve 10 is closed, that is, when the hydraulic pump 1 is in a neutral state and the hydraulic motor 2 is in a stopped state, the on-off valve 21 is immediately activated, and the main pipe is opened as shown in FIG. Continuity becomes impossible.

In addition, in the case where the on-off valve 21 is provided as a motor stop means for keeping the hydraulic motor 2 in a stopped state, as in the second embodiment, the function of restraining the operation of the hydraulic motor 2 is as described above. This is inferior to the brake device 20 in the first embodiment. but,
It is much superior to the restraint function provided by the hydraulic pump 1, and is equivalent to a counterbalance valve used in general open circuits. Furthermore, as shown in this second embodiment, when the crossover relief valve 7 is provided closer to the hydraulic motor 2 than the on-off valve 21, when an excessive external force is applied to the load 3, Since the crossover relief valve 7 operates, it has the function of preventing damage to the power transmission system such as the output shaft of the hydraulic motor 2 and the reduction gear. Although not shown in FIG. 7 showing the second embodiment, a switching valve is provided between the shuttle valve 25 and the on-off valve 21, and the switching valve is operated by pressure from the shuttle valve 25. The on-off valve 21 may be operated by pressure from this switching valve.

Regarding the neutral connection type of the servo valve 10, the input means of the servo valve 10, the connection system between this input means and the motor stop means, the communication system between the input means and the output side pressure of the servo valve 10, etc. The invention is not limited to the embodiments shown in FIGS. 1 and 7. 1 and 7, the neutral function of the servo valve 10 is shown as an example in which the output side communicates with the tank, but it is not limited to this, and the neutral function of the servo valve 10, that is, the neutral function of the hydraulic pump 1 is shown. It is only necessary to provide a mechanism or circuit connection in which the output side pressure of the servo valve 10 becomes substantially the tank pressure in the neutral state of the tank.

As described above, the hydraulic system control device of the present invention is provided with a control valve that controls a hydraulic servomechanism by the pressure of the main pipe, and the control valve is connected to a hydraulic source that supplies control pressure to a motor stopping means. At the same time, a first pressure transmitting means for transmitting control pressure to the motor stopping means in accordance with the pressure on the output side of the servo valve is provided on a pipe connecting the hydraulic pressure source and the motor stopping means, and an input means for the hydraulic servo mechanism. a second pressure transmitting means for transmitting control pressure to the motor stopping means in connection with the operation of the hydraulic motor, and detecting whether the hydraulic motor is in a stopped state by the control valve;
Since the motor stopping means is configured to be deactivated by the control pressure from at least one of the first pressure transmitting means and the second pressure transmitting means, the motor stops immediately after the hydraulic motor is stopped. The stopping means can be activated automatically, eliminating the need for a separate hydraulic pump as in the past.
This has the effect of simplifying the structure, and there is no need to install a throttle valve in the main pipe to detect the rotational state of the hydraulic motor, as in the conventional case, and the set pressure of the control valve mentioned above is crossover. Since the pressure can be lower than the set pressure of the relief valve, there is no power loss, and there is no need to detect the relief state of the crossover relief valve as in the past, and the input means of the hydraulic servo mechanism is Since there is no means for setting a delay time from when the motor returns to the neutral position until the motor stop means starts operating, the motor stop means can be operated very accurately without being affected by changes in the inertia of the load. There are certain effects that can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a first embodiment of a control device for a hydraulic system of the present invention, Fig. 2 is a diagram showing the configuration of a hydraulic servo mechanism of the control device shown in Fig. 1, and Fig. 3 is a diagram showing a shuttle system. A graph showing the opening relationship between the output side pressure p ₁ of the valve and the output side pressure p ₂ of the control valve, Fig. 4 is a graph showing the relationship between the pressure p ₁ and the speed v of the servo piston of the servo cylinder, Fig. 5 a and b are the discharge flow rate Q and pressure of the hydraulic pump during hydraulic motor acceleration operation, respectively.
Graphs showing temporal changes in p ₁ , Figures 6a and b are graphs showing temporal changes in flow rate Q and pressure p ₁ during motor deceleration operation, respectively, and Figure 7 shows the second embodiment of the present invention. FIG. 1... Variable displacement hydraulic pump, 2... Hydraulic motor, 3... Inertial load, 9... Servo cylinder, 1
0... Servo valve, 11... Control valve, 12, 15,
22, 24, 25... Shuttle valve, 13, 14...
...Switching valve, 17...Hydraulic pressure source, 20...Brake device, 21...Opening/closing valve, 23...Pilot valve.

Claims (1)

[Claims] 1 A hydraulic servo that configures a hydraulic closed circuit with a variable displacement hydraulic pump and a hydraulic motor that is driven by the variable displacement hydraulic pump and operates an inertial load, and that controls the discharge displacement of the variable displacement hydraulic pump. A control device for a hydraulic system, comprising a mechanism, a motor stopping means for holding the hydraulic motor in a stopped state, and a hydraulic source connected to the motor stopping means and supplying a control pressure to the motor stopping means to cancel the operation. A control valve is provided for controlling the hydraulic servomechanism according to the pressure in a main line connecting the variable displacement hydraulic pump and the hydraulic motor, and a control valve is provided for controlling the hydraulic servomechanism in accordance with the pressure in a main line connecting the hydraulic power source and the motor stopping means. On the way, first pressure transmitting means transmits control pressure to the motor stopping means in accordance with the pressure on the output side of the servo valve constituting the hydraulic servo mechanism, and the motor and a second pressure transmission means for transmitting control pressure to the stop means, and actuation of the motor stop means by the control pressure transmitted through at least one of the first pressure transmission means and the second pressure transmission means. A control device for a hydraulic system, characterized in that it is configured to release the.