JPH1082361A - Hydraulic control circuit for viscous fluid pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly reduce pulsation at the time of driving. SOLUTION: A closed circuit to reciprocally feed pressure oil from both tilting main oil pumps to two hydraulic cylinders 1, 2 is made. Change-over of tilting of the main oil pumps 4 is carried out by an actuator 11, change-over of working directions of the actuator 11 is carried out by a servo valve 10, and working of the servo valve 10 is carried out by a solenoid valve 9 for the main circuit. Proximity sensors LS1, LS2 are provided in the neighbourhood of a stroke end of the main oil cylinder 1, and proximity sensors LS3, LS4 are provided at the stroke end. The solenoid valve 9 for the main circuit is neutralized by signals of the proximity sensors LS1, LS2. Intake and discharge valves are changed over to each other in accordance with signals of the proximity sensors LS3, LS4 and the solenoid valve 9 for the main circuit is changed over by its change-over completion signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control circuit for a viscous fluid pump for sucking and discharging a viscous fluid such as concrete.

[0002]

2. Description of the Related Art In a piston type viscous fluid pump, 2
When one of the main hydraulic cylinders for fluid pressure feeding advances and reaches the stroke end, the proximity sensor operates to switch the suction / discharge valve (swing valve, slide valve, etc.), It is known to switch the cylinder in the opposite direction.

[0003] As an example, when the suction and discharge valve is of a swing valve type, as shown in FIG. 3, the head side pressure chambers of two main hydraulic cylinders 1 and 2 are connected by a sealing line 3 and The rod-side pressure chambers of the two main hydraulic cylinders 1 and 2 and the double tilt main oil pump 4 are connected to main pressure oil lines 5 and 6.
And a line 8 connected to the discharge side of the charge pump 7 is tilted through a servo valve 10 which can be operated by switching a main circuit solenoid valve 9 which is an electromagnetic three-position valve. It is connected to an actuator 11 for adjustment so that the direction of pressure oil guided from the charge pump 7 to the actuator 11 can be switched by switching the servo valve 10.

[0004] Further, as the main hydraulic cylinders 1 and 2 alternately advance and retreat, the pressurized oil from the valve discharge pump 14 is supplied to the oscillating cylinders 12 and 13 which switch the oscillating valves which are suction and discharge valves. A four-way valve 17 that is switched by the operation of the valve circuit solenoid valve 16 is provided in the middle of the pressure oil line 15, and the four-way valve 17 is switched. The oscillating cylinders 12 and 13 are moved forward and backward to switch the oscillating valve. Further, the pressure oil line 18 is taken out of the pressure oil line 15 and an accumulator 19 is provided. The line 18 is sequentially connected to the variable throttle valve 2
After passing through the pressure reducing valve 21, the servo valve 10 is guided to the operation section of the servo valve 10 through the main circuit solenoid valve 9. In addition,
Reference numeral 23 denotes a check valve attached to the oil drain line 22 of the actuator 11 to prevent the discharge amount of the main oil pump 4 from increasing rapidly.

In the above configuration, when the proximity sensors LS1 and LS2 provided at the respective forward stroke ends of the two main hydraulic cylinders 1 and 2 are operated alternately by the main hydraulic cylinders 1 and 2 being advanced alternately. , Main circuit solenoid valve 9
Solenoid SOL. 1 or SOL. When the main circuit pump 2 is excited and the main circuit solenoid valve 9 is switched, the main oil pump 4 is reversed, and at the same time, the valve circuit solenoid valve 16 is turned on.
Solenoid SOL. 3 or SOL. When the valve 4 is excited and the four-way valve 17 is switched, the forward / backward movement of the swing cylinders 12 and 13 is switched.

[0006]

However, in the conventional hydraulic control circuit of the viscous fluid pump, the proximity sensor LS1
Alternatively, the main circuit solenoid valve 9 and the valve circuit solenoid valve 16 are switched at the same time as the operation of the LS 2, but their operations are independent of each other and are not controlled at all, and therefore the tilting of the main oil pump 4 is performed. The angle is switched in the opposite direction, and the suction / discharge valve is switched. Even if both operations are completed, the interruption of the pressure oil cannot be eliminated and a large pressure fluctuation occurs. There is a problem that pulsation occurs because the effect cannot be exhibited. That is, when the main circuit solenoid valve 9 is switched, the tilt angle of the main oil pump 4 is gradually reduced, and the suction / discharge valve is switched in the process of increasing the tilt angle in the reverse direction from zero discharge amount. Due to the unstable timing, pressure fluctuations have not been effectively reduced. Furthermore, if any of the operations is delayed, the main oil pump 4 is usually operated to reverse instantaneously, so that there is a problem that the pulsation becomes larger. A check valve 23 is provided in the oil drain line 22 of the actuator 11 in order to prevent the discharge amount of the main oil pump 4 from suddenly increasing. Viscosity, etc.), the operation becomes dependent, and pressure fluctuation cannot be reduced effectively.

Accordingly, an object of the present invention is to provide a hydraulic control circuit for a viscous fluid pump capable of suppressing large fluctuations in pressure during operation and reliably reducing pulsation.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a closed circuit in which pressure oil discharged from a double tilt main oil pump is alternately supplied to two main hydraulic cylinders. And an actuator for switching the tilt direction of the main oil pump, a servo valve for switching the operation direction of the actuator, and a main circuit solenoid valve which is a three-position valve for operating the servo valve. A hydraulic circuit for a viscous fluid pump, further comprising: a solenoid valve for a valve circuit that switches a suction / discharge valve in accordance with the forward / backward operation of the two main hydraulic cylinders. Proximity sensors are provided near each stroke end and at the stroke end, and the main circuit solenoid valve is switched by a signal from the proximity sensor near the stroke end. While, as the switching of the solenoid valve for the valve circuit by a signal of the proximity sensor of the stroke end is performed, further, a configuration that can be switched is a main circuit electromagnetic valve by switching completion signal suction and discharge valves.

When the main hydraulic cylinder reaches the vicinity of the stroke end, the proximity sensor at that position is actuated, and one solenoid of the solenoid valve for the main circuit is changed from the excited state to the demagnetized state so that the solenoid valve for the main circuit is set to the neutral position. , The discharge amount of the main oil pump is reduced to zero. When the main hydraulic cylinder reaches the stroke end near the discharge amount of zero, the suction / discharge valve is switched by the signal of the proximity sensor at that position, and the other solenoid of the main circuit solenoid valve is excited based on the switching completion signal. By switching, the discharge amount of the main oil pump is increased. Therefore, there is no large pressure fluctuation, and pulsation is reduced.

Further, instead of using the signal from the proximity sensor at the stroke end of the main hydraulic cylinder and the switching completion signal of the suction / discharge valve, the operation is performed based on the signal from the proximity sensor near the stroke end of the main hydraulic cylinder. A configuration in which a timer is used may be used.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show an embodiment of the present invention. In a configuration similar to the hydraulic control circuit of the viscous fluid pump shown in FIG. Instead of providing the proximity sensors LS1 and LS2, the proximity sensors LS1 and LS2 are provided at a position slightly before the forward stroke end, and the proximity sensors LS3 and LS4 are provided at the forward stroke end, and the proximity sensor LS1 or LS2 is provided. Is activated when the solenoid SOL. 1 or SOL. 2 is demagnetized so that the main circuit solenoid valve 9 is switched to the neutral position, and when the proximity sensor LS3 or LS4 is operated, the solenoid SOL. 3 or SOL. When the valve 4 is excited and the solenoid valve 16 for the valve circuit is switched, the four-way valve 17 is switched.

An unload valve 25 is provided in the main hydraulic lines 5 and 6 so as to be switched by the operation of an electromagnetic valve 24. The proximity sensors LS5 and LS6 are provided at the stroke ends of the oscillating cylinders 12 and 13. Is provided, and when the proximity sensor LS5 or LS6 operates, the solenoid S
OL. 2 or SOL. 1 is energized so that the two tilt main oil pumps 4 are reversed, and when the proximity sensor LS5 or LS6 is operated, the solenoid SOL. When the solenoid 5 is excited and the solenoid valve 24 is switched, the unload valve 25 is switched to the open position.

In the case where the main hydraulic cylinder 1 moves forward and the main hydraulic cylinder 2 moves backward, when the main hydraulic cylinder 1 reaches a position slightly before the forward stroke end, the proximity sensor LS1 is activated. And the solenoid SOL. By demagnetizing 1, the main circuit solenoid valve 9 is switched to the neutral position. As a result, the supply of the operating pressure oil to the servo valve 10 is cut off, and the actuator 11 is also gradually returned to the neutral position, so that the discharge amount of the main oil pump 4 is gradually reduced to finally reach zero. .

Subsequently, when the main hydraulic cylinder 1 reaches the forward stroke end when the discharge amount of the main oil pump 4 is near zero, the proximity sensor LS3 is operated,
Solenoid SOL. Of solenoid valve 16 for valve circuit. 3 is energized, the solenoid valve 16 for the valve circuit is switched, and the four-way valve 17
Is switched, the forward / backward movement of the swing cylinders 12 and 13 is switched.

Further, when the swing cylinders 12 and 13 are switched between forward and backward movements and the swing cylinder 12 reaches the stroke end, the proximity sensor LS5 is operated, so that the solenoid SOL. 5 is energized and the solenoid valve 24 is switched so that the unload valve 2
5 is switched to the communication position of the main pressure oil lines 5 and 6.
At the same time, the solenoid SO of the solenoid valve 9 for the main circuit is
L. When the main valve 2 is excited and the main circuit solenoid valve 9 is switched to the communication position, the servo valve 10 is operated and the actuator 11 is operated in the opposite direction. The angle is switched in the opposite direction, the pressure oil discharge amount is gradually increased, and the operation shifts to the constant speed operation. Thereby, the forward / backward movement of the main hydraulic cylinders 1 and 2 is switched.

Even after the main hydraulic cylinders 1 and 2 are switched between forward and backward, the same control is performed as shown in the time chart of FIG.

As described above, in the present invention, based on the signals of the proximity sensors LS1 and LS2 of the main hydraulic cylinders 1 and 2, the main circuit solenoid valve 9 is set to neutral once, and the pressure oil discharge amount of the main oil pump 4 is set. , The discharge amount is set to be zero for a certain time, and the proximity sensor L of the swing cylinders 12 and 13 is set.
After receiving the signals S3 and LS4 (valve switching completion signal), the main circuit solenoid valve 9 is switched to supply the pressure oil to the tilt adjustment actuator 11 to start the discharge of the pressure oil of the main oil pump 4. When the set discharge amount is reached, the operation is shifted to the constant speed operation.
The large pressure fluctuation which occurs at the time of switching between forward and backward can be suppressed, and pulsation can be reduced. Incidentally, the command for the tilt angle of the main oil pump 4 is provided by the pressure reducing valve 21.
The rate of increase of the tilt angle can be adjusted by the variable throttle valve 20.

In the above-described embodiment, the time from when the amount of pressurized oil discharged from the main oil pump is reduced to zero once to start discharging again is determined by the proximity sensors LS1, LS3, L
Combination of S5 and proximity sensors LS2, LS4, LS6
, But the proximity sensor L
The functions of S3, LS5 and LS4, LS6 are
A timer that operates on the basis of the signals of S1 and LS2 may be substituted. In the embodiment, the suction / discharge valve is of the swing valve type, but is of the slide valve type. It is needless to say that the present invention can be carried out in the same manner, and that various changes can be made without departing from the gist of the present invention.

[0020]

As described above, according to the hydraulic control circuit of the viscous fluid pump of the present invention, the following excellent effects are exhibited. (1) An actuator having a closed circuit for alternately supplying pressure oil discharged from both tilting main oil pumps to two main hydraulic cylinders, and switching a tilting direction of the main oil pump. A servo valve for switching the operation direction of the actuator, and a main circuit solenoid valve which is a three-position valve for operating the servo valve.
In a hydraulic control circuit of a viscous fluid pump provided with a solenoid valve for a valve circuit for switching a suction / discharge valve in accordance with the forward / backward operation of the two main hydraulic cylinders, the vicinity of each stroke end of the two main hydraulic cylinders and the stroke Proximity sensors are provided at the ends, respectively, so that the solenoid valve for the main circuit can be switched by the signal of the proximity sensor near the stroke end, and the solenoid valve for the valve circuit is switched by the signal of the proximity sensor at the stroke end. In addition, since the main circuit solenoid valve is switched by the switching completion signal of the suction / discharge valve, the stroke of the main hydraulic cylinder is detected by the proximity sensor near the stroke end, and then the main oil pump is switched. The discharge amount is reduced to zero once, and the main hydraulic cylinder strikes near the discharge amount of zero. Switching the suction and discharge valve by a signal of the proximity sensor of the stroke end is reached Kuendo,
Since the main oil pump can start discharging upon receiving the switch completion signal of the suction / discharge valve, large pressure fluctuations can be suppressed, pulsation can be reduced, and the original effect of the closed circuit is exhibited. can do. (2) Using a timer that operates based on a signal from a proximity sensor near the stroke end of the main hydraulic cylinder to substitute the function of the proximity sensor at the stroke end of the main hydraulic cylinder and the proximity sensor at the switching completion position of the suction / discharge valve. With such a configuration, the same operation and effect as the above item (1) can be obtained, and the discharge amount can be surely increased after a predetermined time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a hydraulic control circuit of a viscous fluid pump according to the present invention.

FIG. 2 is a time chart showing an operation.

FIG. 3 is a schematic diagram illustrating an example of a hydraulic control circuit of a conventional viscous fluid pump.

[Explanation of symbols]

 1, 2 main hydraulic cylinder 4 double tilt main oil pump 9 solenoid valve for main circuit 10 servo valve 11 actuator 16 solenoid valve for valve circuit LS1, LS2, LS3, LS4 proximity sensor

Claims (2)

[Claims] 1. A closed circuit for alternately supplying hydraulic oil discharged from two tilting main oil pumps to two main hydraulic cylinders, and for switching a tilting direction of the main oil pump. , A servo valve for switching the operation direction of the actuator, and a main circuit solenoid valve which is a three-position valve for operating the servo valve, and further, the forward and backward operation of the two main hydraulic cylinders In the hydraulic control circuit of the viscous fluid pump including a valve circuit solenoid valve for switching the suction / discharge valve in accordance with the above, proximity sensors are provided near each stroke end and at the stroke end of the two main hydraulic cylinders, respectively. The main circuit solenoid valve is switched by the signal of the proximity sensor near the stroke end, and the signal of the proximity sensor at the stroke end is switched. A hydraulic circuit for a viscous fluid pump, characterized in that the switching of the solenoid valve for the valve circuit is performed, and the solenoid valve for the main circuit is switched by a switching completion signal of the suction / discharge valve. . 2. An operation is performed based on a signal from a proximity sensor near the stroke end of the main hydraulic cylinder, instead of using a signal from a proximity sensor at the stroke end of the main hydraulic cylinder and a switching completion signal of the suction / discharge valve. 2. The hydraulic control circuit for a viscous fluid pump according to claim 1, wherein a timer is used.