JP2994582B2 - Turning control circuit for construction machinery, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of hydraulic turning control circuits for construction machines.

[0002]

2. Description of the Related Art A hydraulic control circuit used for construction machines, etc.
Various circuits have been proposed as circuits for controlling a rotating body or a revolving body. For example, Japanese Patent Laid-Open Publication No. Hei 6-1
No. 23303 discloses a circuit of a hydraulic control device for keeping the operation speed of an actuator constant irrespective of a change in load pressure and preventing cavitation. Further, Japanese Patent Application Laid-Open No. Hei 6-117406 discloses a fluid pressure for suppressing an increase in load pressure generated at the time of starting an actuator coupled to a large inertial load and for suppressing a decrease in speed of another actuator. A drive circuit for an actuator is disclosed. further,
Japanese Patent Application Laid-Open Publication No. Hei 6-117409 discloses a circuit of a load-sensitive hydraulic control device in which the inching area of the operation lever is limited even when the load pressure increases and the operation feeling does not change. I have.

FIG. 7 shows an example of a hydraulic control circuit for controlling a conventional swing body. In FIG. 7, a hydraulic pump 1 is connected to an oil tank 2 by a center oil passage 3. A switching valve 4 is provided in the center oil passage 3. The switching valve 4 is a center-open type switching valve, and a bleed-off throttle 4a, a meter-in throttle 4b, and a meter-out throttle 4c are provided on an oil passage between input / output ports. Pilot ports 4e, 4 of switching valve 4
f is connected to the pilot valve 5 via pilot oil passages 6 and 7. The pilot valve 5 is configured such that when the operation lever 8 is tilted leftward, pilot pressure appears in the pilot oil passage 7, and when it is tilted rightward, pilot pressure appears in the pilot oil passage 6. A hydraulic motor 9 is connected to a downstream port of the switching valve 4 by oil passages 10 and 11. A revolving unit (not shown) is connected to the hydraulic motor 9. The oil passage 12 branched from the upstream of the switching valve 4 on the center oil passage 3 is connected to an upstream port of the switching valve 4 via a check valve 14, and the remaining upstream port is connected to the oil passage 1.
3 is connected to the oil tank 15.

[0004] Bleed-off diaphragm 4a, meter-in diaphragm 4
b, the relationship between the opening area of the meter-out throttle and the stroke of the spool of the switching valve 4 is shown in the upper graph of FIG. 3, the horizontal axis indicates the stroke of the spool, and the vertical axis indicates the opening area. The opening area of the bleed-off diaphragm 4a sharply decreases at first and gradually decreases in the middle, but the inflection point A
After that, it decreases rapidly and is closed. On the other hand, the opening areas of the meter-in stop 4b and the meter-out stop 4c increase very gradually at the beginning, and increase in the latter half.

A throttle 16 (hereinafter referred to as a negative control throttle) is provided upstream of the oil tank 2 on the center oil passage 3. An oil passage 17 branched from the upstream of the negative control throttle 16 (hereinafter, referred to as a negative control oil passage) is connected to a first input port 18 e of the regulator 18. The regulator 18 controls the discharge amount of the hydraulic pump 1. A second piston 18a and a first piston 18b connected to a connecting rod 18c are provided in a cylinder.
Is pressed by a spring, and the other end of the connecting rod 18c is connected to a swash plate (not shown) for changing the discharge amount of the hydraulic pump 1. The regulator 18 is connected to perform negative control. That is, the hydraulic pressure in the negative control oil passage 17 (hereinafter, referred to as
When the negative control pressure increases, the connecting rod 18c of the regulator 18 moves rightward (in the direction of arrow D), and the discharge amount of the oil pump 1 decreases. Conversely, when the negative control pressure drops, the connecting rod 18c moves to the left (in the direction of arrow I), and the discharge amount increases. FIG. 6 shows the relationship between the negative control pressure p and the discharge amount q. As shown in FIG. 4, when the negative control pressure is equal to or higher than p1, the discharge amount is constant at q1, but the negative control pressure is equal to p1.
When the negative control pressure is equal to or less than p2, the discharge amount becomes constant at q2.

The second input port 18f of the regulator 18
Is connected to an output port of a solenoid valve 20 by an oil passage 19. When a hydraulic pressure higher than the negative control pressure acts on the oil passage 19, as shown in FIG. 5C, the first piston 18a is pressed rightward, thereby restricting the leftward movement of the piston 18b. The input ports of the solenoid valve 20 are connected to a pilot pump 21 and an oil tank 22, respectively. The solenoid 23 of the solenoid valve 20 is connected to a controller 24 by electric wiring, and the controller 24 is connected to a mode selection switch 25 by electric wiring. The selected mode includes a normal operation mode and a finishing operation mode. When the finishing operation mode is selected by the mode selection switch 25, the selection switch 25 outputs the finishing operation mode signal to the controller 2.
4 is output. When the finishing operation mode signal is input, the controller 24 outputs a constant current to the solenoid. When a constant current flows through the solenoid 23, the solenoid valve 20
The state is switched to the state b.

Since the hydraulic control circuit is configured as described above, it operates as follows. First, the case where the normal work mode is selected will be described. When the selection switch 25 selects the normal operation mode, no current is output from the control 24 to the solenoid 23. Therefore, the solenoid valve 20 is in the a state, and the pilot pressure oil from the pilot pump 21 is not supplied to the second port 18f of the regulator 18.

In this mode, when the operating lever 8 is tilted to the right, for example, pilot pressure oil is supplied to the pilot port 4e of the switching valve 4, and the spool starts to move rightward.
In the first stage, the bleed-off diaphragm 4a sharply reduces the aperture, and the resistance sharply increases. The negative control pressure in the negative control oil passage 17 also decreases, and the first piston 18b is pushed to the left by the force of the spring, thereby increasing the discharge amount of the hydraulic pump 1. Accordingly, the resistance of the bleed-off throttle 4a increases rapidly, but the discharge amount of the hydraulic pump 1 increases, so that the negative control pressure drops gradually. On the other hand, since the oil pressure upstream of the switching valve 4 increases rapidly, the pressure oil flows through the check valve 14. However, since the openings of the meter-in stop 4b and the meter-out stop 4c are hardly opened (FIG. 3).
), The hydraulic oil does not flow to the hydraulic motor 9, and the hydraulic motor 9 does not start turning.

Next, when the spool moves further to the right, the opening of the bleed-off diaphragm 4a is gradually closed, but the openings of the meter-in diaphragm 4b and the meter-out diaphragm 4c become large. Then, the hydraulic motor starts turning. Further, the spool moves rightward, and the opening area of the bleed-off stop reaches the inflection point A. The negative control pressure at this time is p4 (see FIG. 4),
The pump discharge amount is q4. During this time, meter-in aperture 4
Since b and the aperture of the meter-out aperture 4c are increasing,
The turning speed of the hydraulic motor 9 gradually increases as shown by the solid line N in the lower graph of FIG.

When the spool further moves to the right, the opening area of the bleed-off stop passes through the inflection point A and sharply decreases in the final stage. Accordingly, the negative control pressure rapidly drops from p4 to p2, and the pump discharge amount changes from q4 to q2.
(See FIG. 4). On the other hand, since the openings of the meter-in throttle 4b and the meter-out throttle 4c are also rapidly increasing, a large amount of high-pressure oil rapidly flows through the hydraulic motor 9. Accordingly, the turning speed of the hydraulic motor 9 is equal to the solid line N in FIG.
As shown by, it rapidly reaches the maximum speed. When the operating lever 8 is tilted to the left, the pilot pressure oil flows through the oil passage 7, the oil passage of the switching valve is connected in reverse, and the hydraulic motor 9
The pressure oil flows in the opposite direction. Accordingly, the hydraulic motor 9 rotates in the reverse direction, but the operation is the same as that when the hydraulic motor 9 is tilted rightward.

Next, a case where the finishing operation mode is selected by the selection switch 25 will be described. Select switch 25
When the finishing operation mode is selected, the mode signal is input to the controller 24, and the controller 24 outputs a constant current to the solenoid 23. Solenoid 23
When the current flows through the solenoid valve 20, the solenoid valve 20 switches to the state b,
The pilot oil pressure of the pilot pump 21 flows to the second port 18f of the regulator 18 via the solenoid valve 20, and the first piston 18a is pushed rightward (see FIG. 5C).

When the operating lever 8 is tilted rightward in this state,
This control circuit performs almost the same operation as in the normal operation mode described above. That is, when the negative control pressure in the negative control oil passage 17 is high, the same operation as the above operation is performed. However, when the negative control pressure decreases, unlike the operation in the normal operation mode, the leftward movement of the first piston 18b is restricted, so that the discharge amount of the hydraulic pump 1 does not reach the maximum discharge amount q2. Therefore, in the finishing mode, the turning speed of the hydraulic motor does not reach the maximum speed and is limited to a constant speed.

[0013]

As described above,
In the normal operation mode, the turning speed of the hydraulic motor varies widely from zero to the maximum speed, and in the finishing operation mode, it changes from zero to a constant speed. However, in the normal operation mode, the operation speed suddenly reaches the maximum turning speed, so that there is a problem that the operation is uncomfortable and the operation is difficult. The present invention
It is an object of the present invention to provide a hydraulic turning control circuit that can be operated smoothly without feeling uncomfortable even in a normal operation mode.

[0014]

According to a first aspect of the present invention, there is provided a hydraulic slewing control circuit provided with a switching valve on an oil passage connecting a variable discharge pump and an oil tank. A hydraulic motor connected to the valve, a throttle provided upstream of the oil tank, and an oil passage branched from the upstream of the throttle connected to a control port of a regulator for controlling the discharge amount of the variable discharge pump. Wherein a detection means for detecting a predetermined time and a control means for smoothing a change in the discharge amount of the variable discharge pump after the detected time are provided. Here, the predetermined time is a time at which the negative control pressure rapidly drops (hereinafter referred to as an inflection point time) or a time related thereto, for example, a stroke end time, or a time between the inflection point time and the stroke end time. At any time. This control circuit detects a predetermined time, and the control means smoothly changes (increases) the discharge amount of the variable discharge pump after that time.

According to a second aspect of the present invention, in the hydraulic swing control circuit according to the first aspect, the detecting means detects a higher one of the two pilot pressures of the switching valve. It is characterized by comprising a pressure sensor and a calculating means for calculating a stroke end time from an output signal of the pressure sensor. The detecting means of the control circuit obtains a time associated with the inflection point time.

According to a third aspect of the present invention, in the hydraulic slewing control circuit according to the first aspect, the detecting means includes a pressure sensor for detecting a hydraulic pressure of an oil passage branched from upstream of the throttle, and the pressure sensor. And an operation means for calculating an inflection point time from the output signal of the above.
The detecting means of the control circuit obtains the inflection point time.

According to a fourth aspect of the present invention, in the hydraulic turning control circuit according to any one of the first to third aspects, the control means makes the discharge amount change after the detected time smooth. Signal generating means for generating a control signal for controlling the regulator, and an electromagnetic proportional pressure reducing valve which is operated by the control signal and supplies pressure oil to a restriction port for restricting the operation of the regulator. In this control circuit, when a predetermined time is detected by the detection circuit, the control signal generating means generates a control signal for smoothing the change in the discharge amount using the data at that time, and the signal is an electromagnetic signal. It is converted to a hydraulic signal by a proportional control valve and applied to a restriction port that restricts the operation of the regulator.

According to a fifth aspect of the present invention, there is provided a hydraulic swing control circuit according to any one of the first to fourth aspects, further comprising a work mode changeover switch for selecting a work mode including a finish work mode. When the mode is selected, a limiting means for limiting the maximum discharge amount of the discharge pump is provided.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 shows the configuration of Embodiment 1 of the present invention. 1, the same components as those of the conventional example shown in FIG. 7 are denoted by the same reference numerals, and detailed description thereof will be omitted. Elements that have been changed from the conventional example and elements that have been newly added are given reference numbers greater than 30.

In FIG. 1, a shuttle valve 31 is interposed between oil passages 6 and 7 by an oil passage 32. The output of the shuttle valve 31 is connected to a pressure sensor 33 by an oil passage. The output end of the pressure sensor 33 is connected to the wiring 36
Is connected to an arithmetic unit 37 of the controller 35 via an A / D converter 38. The operation unit 37 obtains the time when the operation of the operation lever 8 is started and the stroke end time at the moment when the spool of the switching valve 4 reaches the stroke end based on the detected data.
9 is output. The control signal generator 39 generates a control signal i based on these time signals. FIG.
An example is shown (see the solid line i in FIG. 2). The controller 35 causes the control current to flow through the wiring 40 to the solenoid of the electromagnetic proportional pressure reducing valve 41 in accordance with the generated control signal i. The output port of the electromagnetic pressure reducing proportional valve 41 is connected to the regulator 1 by the oil passage 19.
8 is connected to the second port 18f. When the finishing operation mode is selected by the mode changeover switch 25, the controller 35 continues to supply a constant current based on the time signal.

Since the first embodiment is configured as described above, it operates as follows. That is, in the normal operation mode, when the operation lever 8 is tilted rightward, a pilot pressure appears in the oil passage 6, and the spool of the switching valve 4 starts to move rightward.
In this case, at the same time, the oil pressure in the oil passage 6 is changed to the shuttle valve 31, the oil passage 3
4, the pressure is detected by the pressure sensor 33, and it is known that the operation has been started by the arithmetic circuit 37. The control signal generator 39 outputs a signal i of a constant current, as shown in FIG. In accordance with this signal, the proportional pressure reducing valve 41 supplies a constant pressure oil v to the second port of the regulator 18.

In the initial stage immediately after the start of the operation, the negative control pressure is large, so that the second piston 18a is pressed to the left (see FIG. 5A). Next, at an intermediate stage where the spool has moved further to the right, the bleed-off aperture 4a
The second piston 18a moves to the right side, the first piston 18b moves to the left side and approaches, and finally the projection of the second piston 18a comes into contact with the first piston 18b. (See FIG. 5B). In this state, the second piston 18a is in an equilibrium state or is in contact with the left side wall. further,
At the final stage when the spool of the switching valve 4 moves to the right and reaches the state of the point A in FIG. 3, the negative control pressure sharply decreases. Therefore, the second piston 18a comes into contact with the right wall of the cylinder, preventing the left movement of the first piston 18b.

Further, the spool moves rightward to reach the stroke end. When the spool reaches the stroke end, the pilot pressure in the oil passage 6 rises, and this pressure rise passes through the pressure sensor 33, and the arithmetic circuit 37 determines the pressure rise and its time. This time is called a stroke end time. During this time, the second piston cannot move leftward, so that the discharge amount of the hydraulic pump 1 is constant and does not increase. However, since the opening areas of the meter-in restrictor 4b and the meter-out restrictor 4c increase until reaching the stork end, the turning speed of the hydraulic motor gradually increases.

The control signal generator 39 decreases the control signal i at a fixed rate or an appropriate rate after the stroke end time. As the control signal i decreases, the output pressure v of the electromagnetic proportional control valve 41 also decreases (see FIG. 2). Accordingly, the second piston 18b and the first piston 18a gradually move leftward while in contact with each other, and reach the state shown in FIG. 5B again. During this time, the discharge amount of the hydraulic pump 1 also gradually increases, whereby the turning speed of the hydraulic motor 9 also gradually increases to reach the maximum speed. Accordingly, the turning speed of the hydraulic motor smoothly rises as shown by the dotted curve M in FIG.

Next, the case where the finishing operation mode is selected will be described. In this case, the controller 35
Output while maintaining a constant current control signal. Therefore, the output pressure of the electromagnetic proportional control valve is kept constant and the maximum discharge amount of the hydraulic pump 1 is limited, which is the same as the operation of the conventional device. As is known from the above description, the turning speed of the hydraulic motor in the normal operation mode of this embodiment is a curve as shown by a dotted curve M in FIG. 3, and the turning speed does not change rapidly. Therefore, there is an effect that a smooth operation without discomfort becomes possible.

Embodiment 2 FIG. 6 shows the configuration of Embodiment 2 of the present invention. 6, the same components as those in the conventional example shown in FIG. 7 are denoted by the same reference numerals, and the same components as those in the first embodiment in FIG. Omitted. The different elements are given reference numbers greater than 50.

In FIG. 6, an oil passage 56 branched from the negative oil passage 17 is connected to the pressure sensor 51. The output of the pressure sensor 51 is supplied to the A / D
Arithmetic circuit 5 of controller 53 via converter 38
4 is connected. The output of the arithmetic circuit 54 is connected to the control signal generator 55. The arithmetic circuit 54 performs an operation such as differentiation on the output signal of the pressure sensor 51 to obtain the first time of the pressure fluctuation and the last time at which the pressure sharply drops, that is, the inflection point time of the point A in FIG. Ask for. The control signal generator 55 generates a current signal i 'of a constant level at the time of the first pressure fluctuation, and gradually reduces the level of the current signal i' at the inflection point time (see the dotted line graph in FIG. 2).

Embodiment 2 is configured as described above, and operates as follows. In the normal operation mode, the operation lever 8
To the right, pilot pressure appears in the oil passage 6 and the switching valve 4
Starts to move to the right. The opening of the bleed-off diaphragm 4a decreases sharply at first. The negative control pressure first decreases, but does not decrease significantly because the discharge amount of the hydraulic pump 1 increases. The arithmetic circuit 54 calculates the pressure fluctuation by calculating the time, and outputs the time to the control signal generator 55. When receiving the time of the pressure change, the control signal generator 54 causes a current i ′ at a certain level to flow through the solenoid of the electromagnetic proportional control valve 41. As a result, the electromagnetic proportional control valve 41 supplies a constant pressure oil v ′ to the second port 18f of the regulator 18 (see the dotted line graph in FIG. 2). At this time, the first and second pistons of the regulator 18 are in the state shown in FIG. In this state,
The discharge rate of the hydraulic pump 1 is also small, and the meter-in throttle 4b,
Since the meter-out throttle 4c is not open, the hydraulic motor 9
Does not rotate.

When the spool of the switching valve 4 moves further to the right, the bleed-off throttle 4a is in a gently inclined state as shown in FIG. 3, and the electromagnetic proportional valve 41 maintains a constant oil pressure. Since the pressure drops, regulator 1
8 is as shown in FIG. In this state, the discharge amount of the hydraulic pump 1 is maximized, but the meter-in throttle 4b and the meter-out throttle 4c are gradually opened and have not yet fully opened. Therefore, the turning speed of the hydraulic motor 9 gradually increases.

Further, when the spool moves rightward,
The bleed-off throttle 4a reaches the point A in FIG. 3, and the negative control pressure rapidly decreases. At this time, the regulator 18
It is in the state of (C). The arithmetic circuit 54 calculates the inflection point time and outputs it to the control signal generator 55. The control signal generator 55 starts to gradually reduce the level of the control signal as shown by the dotted line graph in FIG. When the control signal becomes zero, the regulator 18 returns to the state of FIG. 5B again. In this state, the discharge amount of the hydraulic pump 1 gradually becomes maximum, and the meter-in throttle 4b and the meter-out throttle 4c also become fully open, so that the hydraulic motor 9 gradually reaches the maximum turning speed.

When the finishing mode is selected by the work mode changeover switch, the operation is the same as in the first embodiment. As can be understood from the above description, also in the control circuit of the second embodiment, the turning speed of the hydraulic motor 9 is as shown by a dotted curve M in FIG. Therefore, a smooth operation can be performed without causing a feeling of strangeness in the operation.

Although the embodiments and examples of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to those described or illustrated above and does not depart from the gist of the present invention. Even if the design of the range is changed, it is included in the present invention. For example, the predetermined time is not limited to the stroke end time and the inflection point time, and may be another time related thereto, and the detection method is not limited to the above-described method.

[0033]

As described above, according to the present invention,
Since the turning speed of the hydraulic motor changes smoothly, there is an effect that the operator can perform a smooth operation without feeling uncomfortable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a control signal.

FIG. 3 is a diagram showing a change in a throttle opening degree of a switching valve and a turning speed of a hydraulic motor.

FIG. 4 is a diagram showing a relationship between a negative control pressure and a pump discharge amount.

FIG. 5 is a view showing a position of a piston of the regulator.

FIG. 6 is a diagram showing a configuration of a second embodiment.

FIG. 7 is a diagram showing a configuration of a conventional hydraulic turning control circuit.

[Explanation of symbols]

 Reference Signs List 1 hydraulic pump (variable discharge pump) 2 oil tank 3 center oil path 4 switching valve 9 hydraulic motor 16 negative control throttle 18 regulator 18a second piston 18b first piston 18e first port (control port) 18f second port (restricted port) 25 Work mode changeover switch 24, 35, 53 Controller 33, 51 Pressure sensor 37, 54 Operation circuit 39, 55 Control signal generator 41 Electromagnetic pressure reducing proportional valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02F 9/22 F15B 11/04

Claims (5)

(57) [Claims] 1. A switching valve is provided on a center oil passage connecting a variable discharge pump and an oil tank, a hydraulic motor is connected to the switching valve, and a throttle is provided upstream of the oil tank. Detecting means for detecting a predetermined time in a hydraulic slewing control circuit connected to the control port of the regulator for controlling the discharge amount of the variable discharge pump, and discharging of the variable discharge pump after the detected time. A hydraulic slewing control circuit for a construction machine or the like, characterized by comprising control means for smoothly changing the amount. 2. The pressure sensor according to claim 1, wherein the detection means detects a higher one of two pilot pressures of the switching valve, and a calculation means calculates a stroke end time from an output signal of the pressure sensor. The hydraulic swing control circuit according to claim 1, wherein 3. The pressure sensor according to claim 1, wherein the detection means includes a pressure sensor for detecting a hydraulic pressure of an oil passage branched from an upstream of the throttle, and a calculation means for calculating an inflection time from an output signal of the pressure sensor. The hydraulic turning control circuit according to claim 1, wherein 4. The control means includes: control signal generating means for generating a control signal for smoothing the change in the discharge amount after the detected time; and operating in accordance with the control signal to control the operation of the regulator. 4. The hydraulic turning control circuit according to claim 1, further comprising an electromagnetic proportional pressure reducing valve for supplying pressure oil to a restriction port to be restricted. 5. The hydraulic swing control circuit according to claim 1, further comprising: a work mode changeover switch for selecting a work mode including a finishing work mode, and when the finishing work mode is selected, limits a maximum discharge amount of the discharge pump. The hydraulic turning control circuit according to any one of claims 1 to 4, further comprising a limiting unit.