JPH04290604A - Fluid pressure servo system - Google Patents

Abstract

PURPOSE:To dissolve flow unablance between a discharge side and an intake side and conduct high precision control at the time of the servo pump control of a rod cylinder whose piston pressure receiving area is different. CONSTITUTION:At a system in which a rod cylinder 3 is subjected to drive control by means of a servo pump 1, a control valve 14 having ports 14a, 14b, 14c is provided between oil passages 21a, 21b. And, when the piston 5 of the rod cylinder 3 is moved in a rod 4b opposite direction, all of ports 14a, 14b, 14c are intercepted, and a shortage flow is supplied to the oil passage 21b through a check valve 9b from a tank 13, and when the piston 5 is moved in a rod 4b direction, ports 14a, 14c are connected to each other, and an excessive flow in the oil passage 21a is returned to the tank 13.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a fluid pressure servo system that uses a fluid servo pump to control the displacement, speed, force, etc. of a cylinder. The present invention relates to a fluid pressure servo system suitable for controlling.

0002

2. Description of the Related Art In a conventional fluid pressure servo system, for example, as shown in FIG.
, 3a are formed, and the single rod cylinder 3 and the oil chambers 3a, 3
A control valve 42 is provided to connect or cut off communication between the oil pressure source 41 and the oil pressure source 41 or the tank 13. Hydraulic source 41
always generates hydraulic power at a constant pressure and constant flow rate. This oil power is transferred to the oil chamber 3a or the oil chamber 3 by the control valve 42.
b, thereby controlling the operation of the rod 4b formed integrally with the piston 5 and controlling the load.

[0003] In a fluid pressure servo system, a single rod cylinder 3 is generally used as shown in FIG. This is because it can be operated effectively when there is an imbalance in the magnitude of the pushing and pulling forces. Therefore, when configuring such a hydraulic system, it becomes necessary to control the single rod cylinder with high precision.

[0004] Information regarding these fluid pressure servo systems can be found in "Hydraulic and Pneumatic Handbook", Ohmsha, February 2, 1989.
5th, page 399.

[0005]

However, in the above-mentioned prior art, when trying to control a single rod cylinder with a servo pump, the area Aa of the pressure receiving surface 5a of the piston 5 and the area Ab of the pressure receiving surface 5b are different (Aa>Ab). Therefore, it cannot be controlled with a servo pump. For example, as shown in FIG. 9, when the piston 5 moves leftward by ΔL, the flow rate flowing into the oil chamber 3a is QLa, and the flow rate flowing out from the oil chamber 3b is QLb.
Then, QLa/QLb=Aa/Ab, so QLa
≠QLb. Further, as shown in FIG. 10, when the piston 5 moves rightward by ΔL, the flow rate flowing out from the oil chamber 3a is QRa, and the flow rate flowing into the oil chamber 3b is QRb. QRa/QRb=
Since Aa/Ab, QRa≠QRb. For this reason, when the single rod cylinder operates, an imbalance occurs between the suction and discharge flow rates of the servo pump, making it difficult to control with high precision.

[0006] An object of the present invention is to provide a fluid pressure servo system that can perform highly accurate control when controlling rod cylinders with pistons having different pressure receiving areas as servo pumps;
The present invention provides a control valve and a rod cylinder used in the fluid pressure servo system.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a servo pump whose discharge side and suction side are mutually switchable, and two oil chambers separated by a piston connected to the servo pump. , and a rod cylinder formed with different pressure receiving areas on both sides of the piston, wherein of the two oil chambers of the rod cylinder, an oil passage is provided in the oil chamber on the side where the pressure receiving area of the piston is larger. control means that connects the tank through the piston and blocks the oil passage when the piston of the rod cylinder moves toward a smaller pressure-receiving area, and opens the oil passage when it moves to a larger pressure-receiving area; It has been established.

The present invention also provides a servo pump whose discharge side and suction side are mutually switchable, two oil chambers separated by a piston are connected to the servo pump, and the pressure receiving areas on both sides of the piston are formed to be different. In a fluid pressure servo system, a tank is connected to the oil chamber on the side having a larger pressure receiving area of the piston out of the two oil chambers of the rod cylinder through an oil passage, and the oil passage Provided with a control valve that opens and closes, and a detector that detects the moving speed of the piston of the rod cylinder, and based on the detection results of the detector, when it is determined that the piston is moving in a direction with a smaller pressure receiving area. A valve control means is provided which closes the control valve and opens the control valve when it is determined that the vehicle is moving in a direction with a larger pressure receiving area.

The present invention also provides a servo pump whose discharge side and suction side can be freely switched, and two oil chambers separated by a piston are connected to the servo pump, and the pressure receiving areas on both sides of the piston are formed to be different. In a fluid pressure servo system, a tank is connected to the oil chamber on the side having a larger pressure receiving area of the piston out of the two oil chambers of the rod cylinder through an oil passage, and the oil passage A control valve for opening and closing is provided, and a pressure detector is provided for detecting the pressure in the two oil chambers of the rod cylinder, and the piston is moved in a direction with a smaller pressure receiving area based on the detection result of the pressure detector. Valve control means is provided which closes the control valve when it is determined that the vehicle is moving in a direction where the pressure receiving area is large, and opens the control valve when it is determined that the vehicle is moving in a direction where the pressure receiving area is large.

Furthermore, the control valve of the present invention includes a cylinder;
a valve body provided reciprocally within the cylinder and having pistons formed at both ends; a first port communicating with an oil chamber formed at one end of the cylinder; and a first port formed at the other end of the cylinder. a second port that communicates with an oil chamber separated by the pistons and that communicates with an oil chamber formed in an intermediate portion of the cylinder; and an oil chamber formed in an intermediate portion of the cylinder. and a passage communicating with the first port, and communication and cutoff between the first port and the third port can be freely switched based on hydraulic pressure applied to the first and second ports. It is characterized by

Further, the rod cylinder of the present invention has two oil chambers separated by a piston, and a rod cylinder portion having different pressure receiving areas on both sides of the piston;
A control valve having three ports, which simultaneously shuts off the three ports when the piston moves toward a smaller pressure-receiving area, and internally communicates two specific ports when the piston moves toward a larger pressure-receiving area. It is characterized by that the part and the part are integrally formed.

0012

[Function] According to each of the above configurations, even if there is an imbalance between the discharge amount from the rod cylinder and the supply amount to the rod cylinder due to the movement of the piston of the rod cylinder, the excess flow is returned to the tank and the insufficient flow is returned to the tank. Since the flow rate is supplied, abnormal high pressure or abnormal low pressure does not occur in the passage connecting the servo pump and the rod cylinder, and the piston of the rod cylinder can be smoothly moved.

Furthermore, since no abnormally high or abnormally low pressure is generated within the passage, energy loss can be minimized, and an energy-efficient system can be constructed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings. (First Embodiment) FIG. 1 is an overall configuration diagram of a fluid pressure servo system showing a first embodiment of the present invention. Reference numeral 1 denotes a servo pump (for example, a swash plate pump), which is driven by a motor 2. The suction port or the discharge port of this servo pump 1 has oil passages 21a and 2 constructed of piping or conduits.
It is connected to one of the oil chambers 3a and 3b of the single-rod cylinder 3 via 1b, respectively. A piston 5 is provided inside the single rod cylinder 3, and the piston 5 forms oil chambers 3a, 3b inside the single rod cylinder 3. One surface 5a of the piston 5 is flat, but a rod 4b is formed on the other surface 5b.

A piston 6 for controlling the swash plate angle of the servo pump 1 is connected to a servo valve 7, and these are connected to the servo pump 1.
It constitutes a discharge amount control mechanism that controls the discharge amount of. 8
is an auxiliary pump that supplies pressure oil to the piston 6 of the discharge amount control mechanism. The auxiliary pump 8 is connected to check valves 9a, 9b and a relief valve 10 of the auxiliary circuit of the single rod cylinder 3. Auxiliary pump 8, check valves 9a, 9b,
The relief valve 10, motor 11, filter 12, and tank 13 constitute a hydraulic pressure source. A control valve 14 having ports 14a, 14b, and 14c is provided in the middle of the oil passages 21a and 21b. Port 14a of control valve 14,
14b is connected to oil passages 21a and 21b, respectively, and port 14c is connected to tank 13. Port 14a
, 14b, and 14c have a structure in which they are communicated with each other and cut off within the control valve 14.

In such a configuration, when the piston 5 is moved to the right in the figure, the servo pump 1 is moved through the oil passage 21.
Oil is sucked in from the oil chamber 3a through the oil passage 21b, and is discharged into the oil chamber 3b through the oil passage 21b. In this case, as mentioned above, due to the difference in the pressure receiving areas on both sides of the piston 5, the flow rate discharged from the oil chamber 3a is greater than the flow rate supplied to the oil chamber 3b, and in the servo pump 1, the flow rate on the suction side is becomes excessive. Therefore, the control valve 14 is operated to cause the ports 14a and 14c to communicate with each other within the control valve 14. At this time, port 14b is blocked from both port 14a and port 14c. When controlled in this manner, the surplus flow supplied from the oil chamber 3a to the suction side of the servo pump 1 passes through the control valve 14 from the port 14a to the port 14c of the control valve 14, and returns to the tank 13, causing the piston 5 to move to the right. It becomes possible to move smoothly in the direction.

On the other hand, when moving the piston 5 to the left, the flow rate discharged from the oil chamber 3b is smaller than the flow rate supplied to the oil chamber 3a due to the difference in the pressure receiving area of the piston 5. Flow rate to the suction side is insufficient. Therefore, the control valve 14 is operated and the ports 14a, 14
b, 14c are all cut off from each other. Then, the insufficient flow rate is sent from the auxiliary pump 8 to the suction side of the servo pump 1 through the check valve 9b. As a result, a sufficient flow rate to the oil chamber 3a is ensured, so that the piston 5 can move smoothly to the left.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention. This embodiment is an example in which the moving direction of the piston 5 is detected by detecting the speed of the rod 4b. As shown in the figure, a detector 31 for detecting the moving speed of the rod 4b is provided on the tip side of the rod 4b. A control device 32 is connected to the detector 31, and the control device 32 is further connected to the control valve 14. The detector 31 detects the speed, displacement, or acceleration of the rod 4b and transmits the detection signal to the control device 32. Control device 3
2 takes in the detection signal from the detector 31 and outputs an opening/closing command to the control valve 14 based on the detection signal, and the control valve 14 performs the valve opening/closing operation according to the opening/closing command.

For example, when the piston 5 is moving to the right, the speed is positive, and when the piston 5 is moving to the left, the speed is negative. If the speed of piston 5 is now positive, piston 5
is moving in the right direction, at this time the detector 31 detects that the speed is positive as described above, and the control device 32 also controls the port 14a of the control valve 14 and the port 14
The operation of the control valve 14 is controlled by outputting a command to the control valve 14 to communicate the port 14b within the control valve 14 and to shut off the port 14b. Thereby, surplus flow from the oil chamber 3a can be returned to the tank 13.

On the other hand, when the piston 5 is moving to the left, the speed of the piston 5 is negative, so the control device 32 outputs a command to shut off the ports 14a, 14b and 14c, The control valve 14 performs a valve closing operation in response to the opening/closing command.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention. This embodiment is an example in which the moving direction of the piston 5 is detected by detecting the pressure in the oil chambers 3a and 3b. As shown in the figure, rod cylinder 3
Pressure detectors 34a and 34 are installed in the oil chambers 3a and 3b, respectively.
b is provided. And pressure detectors 34a, 34
A control device 35 is connected to b, and the control device 35 is further connected to the control valve 14.

Now, when moving the piston 5 to the right, the servo pump 1 sucks oil from the oil chamber 3a.
b, the pressure Pa in the oil chamber 3a is sufficiently lower than the pressure Pb in the oil chamber 3b. At this time, pressure detector 3
4a and 34b detect pressures Pa and Pb, and the control device 35 compares and calculates the pressure signals to issue a command to the control valve 14. As a result, the ports 14a and 14c of the control valve 14 are communicated with each other, and the port 14b is cut off, allowing excess flow to be returned to the tank 13.

On the other hand, when moving the piston 5 to the left, the pressure Pb is sufficiently lower than the pressure Pa, so
The pressures Pa and Pb at that time are detected by the pressure detectors 34a and 34b.
The pressure signal is compared and calculated by the control device 35, and then the pressure signal is detected by the control device 35, and then the control valve 14 ports 14a, 14b, 14c
are cut off from each other. Then, in the same manner as described above, the insufficient flow rate is replenished through the check valve 9b.

(Fourth Embodiment) FIG. 4 is an overall configuration diagram of a control valve showing a fourth embodiment of the present invention. In the figure, ports 14a, 14b, 14c are similar to the three previous embodiments. A spool 15 is provided within the control valve 14, and a piston 15a is formed at the right end of the spool 15, and a piston 15b is formed at the left end. An oil chamber 17a formed on the right end side of the piston 15a is a passage 14a.
' is opened to the port 14a. piston 15
An oil chamber 17b formed on the left end side of b is open to the port 14b. An oil chamber 17c provided between the pistons 15a and 15b opens to the port 14c, and further opens to the tank 13.
is connected to. Also, a passage 1 is located near the right end of the oil chamber 17c.
4a'' is provided, and the passage 14a'' communicates with the oil chamber 17a via a passage 14a'. Further, a spring body 16a is inserted into the oil chamber 17a.

In the above configuration, when the piston 5 is moved to the right, the port 14a becomes the suction side and the port 14b becomes the discharge side, so the pressure in the oil chamber 17a decreases and the pressure in the oil chamber 17b increases. As a result, the piston 15 moves to the right against the biasing force of the spring body 16a. When the piston 15 moves to the right, the ports 14a'' and 14c communicate with each other via the oil chamber 17c, so the oil in the oil passage connected to the port 14a passes through the port 14a'' and flows from the port 14c to the tank 13. You can go back to

Furthermore, when the piston 5 is moved to the left, the port 14a becomes the discharge side and the port 14b becomes the suction side, so the pressure in the oil chamber 17a increases and the pressure in the oil chamber 17b decreases, and the spring body The biasing force of 16a is also added, and the piston 1
5 is pushed to the left. Then port 14
The gap a'' is completely closed, and the port 14a and the tank 13 are cut off.

(Fifth Embodiment) FIG. 5 is a fifth embodiment of the present invention, showing another embodiment of the control valve. The structure of this embodiment is generally similar to that of the embodiment shown in FIG. 4, but the difference is that the diameters of the piston 15a and the piston 15b are different. The pressure receiving area of the piston 15a is Sa, the pressure receiving area of the piston 15b is Sb, and the leftward spring force of the spring 16a is Fsp. Assuming that the piston 15 is now balanced with left and right pressure, PaSa + Fsp
=PbSb holds true. Moreover, if the piston 15 is pressed to the left, PaSa+Fsp>Pb
The relationship Sb holds true. In this state, port 14a''
is in a closed state, and ports 14a and 14c are in a blocked state. When moving the piston 5 to the right, the oil chamber 1
Since the pressure Pa of 7b decreases, the pressure balance becomes PaS
a+Fsp<PbSb, the piston 15 moves to the right, and the ports 14a and 14c communicate with each other.

According to this embodiment, since the diameters of the piston 15a and the piston 15b are different, the return of the piston 15 when shutting off the port 14a'' can be made faster.

(Sixth Embodiment) FIG. 6 shows a sixth embodiment of the present invention, which is still another embodiment of the control valve. In this embodiment, the port 14b is connected to the hydraulic pressure source 18, and the oil chamber 17b is maintained at a certain pressure Pb. In this case, the force pushing the piston 15 to the right is PbSb
, and the force pushing to the left is PaSa+Fsp. PbS
Since b is constant, the piston 15 moves left and right depending on the magnitude of PaSa+Fsp. The pressure Pa is Pa>(Pb
When the relationship is Sb-Fsp)/Sa, the piston 15
is pressed to the left, the port 14a'' is closed, and the ports 14a and 14c are blocked. When the piston 5 is moved to the right, the pressure Pa decreases, so Pa≦(PbSb-Fsp )/Sa, and the piston 15 moves rightward, so the port 14a'' opens and the ports 14a and 14c communicate with each other.

According to this embodiment, since a constant pressure is supplied from the hydraulic source 18, the influence of disturbances can be reduced when controlling the control valve 14.

(Seventh Embodiment) FIG. 7 shows a seventh embodiment of the present invention, and shows an example of a rod cylinder incorporating a control valve. The configuration is as described above, and the oil chambers 3a and 3b of the rod cylinder 3 are the oil chambers 17a and 1 of the control valve 14, respectively.
It communicates with 7b. When the piston 5 moves rightward, the pressure in the oil chamber 3a of the rod cylinder 3 decreases, and at the same time the pressure in the oil chamber 17a of the control valve 14 decreases. When the pressure in the oil chamber 17a decreases, the piston 15 moves to the right, so the port 14a'' opens, and the excess flow of oil in the oil chamber 3a and the oil chamber 17a can return to the tank 3.

Furthermore, when the piston 5 moves to the left, the pressure in the oil chamber 3b and the oil chamber 17b decreases, so the piston 15 moves to the left. As a result, the port 14a'' is closed and the oil chamber 3a and the oil chamber 17c are shut off.

In the embodiments described above, a case was shown in which a single rod cylinder was controlled, but the present invention can also be applied to a case in which a double rod cylinder is controlled.

The fluid pressure servo system of the present invention can be applied to a hydraulic elevator or a rolling device of a rolling mill.

[0035]

[Effects of the Invention] As explained above, according to the present invention,
Even if there is an imbalance in the flow rate required by the rod cylinder due to its operation, the surplus flow is returned to the tank and the insufficient flow is supplied, so there is no abnormal high pressure or abnormality in the passage connecting the servo pump and the rod cylinder. Low pressure does not occur, the fluid pressure servo system can be controlled with high precision, and the reliability of the fluid pressure servo system can be dramatically improved.

Furthermore, since energy loss can be minimized, it is also possible to increase the output of the cylinder.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a fluid pressure servo system showing a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a fluid pressure servo system showing a second embodiment of the present invention.

FIG. 3 is an overall configuration diagram of a fluid pressure servo system showing a third embodiment of the present invention.

FIG. 4 shows a fourth embodiment of the present invention and is a configuration diagram of a control valve.

FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention and another embodiment of the control valve.

FIG. 6 is a configuration diagram showing a sixth embodiment of the present invention and showing still another embodiment of the control valve.

FIG. 7 shows a seventh embodiment of the present invention and is a configuration diagram of a rod cylinder.

FIG. 8 is a configuration diagram of a conventional fluid pressure servo system.

FIG. 9 is a schematic diagram showing the operation of a single rod cylinder.

FIG. 10 is a schematic diagram showing the operation of a single rod cylinder.

[Explanation of symbols]

1 Servo pump 3 Single rod cylinder 3a, 3b Oil room 4b Rod 5 Piston 8 Auxiliary pump 9a, 9b Check valve 13 Tank 14 Control valve 14a, 14b, 14c port 21a, 21b oil passage 31 Detector 32, 35 Control device 34a, 34b Pressure detector

Claims (7)

[Claims] 1. A servo pump whose discharge side and suction side are mutually switchable; and a rod cylinder in which two oil chambers separated by a piston are connected to the servo pump, and the pressure receiving areas on both sides of the piston are different. In the fluid pressure servo system, a tank is connected to the oil chamber on the side where the piston has a larger pressure receiving area among the two oil chambers of the rod cylinder through an oil passage, and the piston of the rod cylinder receives pressure. A fluid pressure servo system characterized by comprising a control means for closing the oil passage when moving to a side with a smaller area and opening the oil passage when moving to a side where a pressure receiving area is larger. 2. A servo pump whose discharge side and suction side are mutually switchable; and a rod cylinder in which two oil chambers separated by a piston are connected to the servo pump, and the pressure receiving areas on both sides of the piston are different. In a fluid pressure servo system, a tank is connected via an oil passage to the oil chamber on the side where the pressure receiving area of the piston is larger among the two oil chambers of the rod cylinder, and control is performed to open and close the oil passage. A valve is provided, and a detector is provided to detect the moving speed of the piston of the rod cylinder, and when it is determined that the piston is moving in a direction with a smaller pressure receiving area based on the detection result of the detector, the control valve is A fluid pressure servo system characterized in that the fluid pressure servo system is provided with a valve control means that closes the control valve and opens the control valve when it is determined that the control valve is moving in a direction with a large pressure receiving area. 3. A servo pump whose discharge side and suction side are mutually switchable; and a rod cylinder in which two oil chambers separated by a piston are connected to the servo pump, and the pressure receiving areas on both sides of the piston are different. In a fluid pressure servo system, a tank is connected via an oil passage to the oil chamber on the side where the pressure receiving area of the piston is larger among the two oil chambers of the rod cylinder, and control is performed to open and close the oil passage. When a valve is provided and a pressure detector is provided to detect the pressure in the two oil chambers of the rod cylinder, and based on the detection results of the pressure detector, it is determined that the piston is moving in a direction with a smaller pressure receiving area. The fluid pressure servo system is characterized in that the fluid pressure servo system is provided with a valve control means that closes the control valve and opens the control valve when it is determined that the movement is in a direction with a larger pressure receiving area. 4. The fluid pressure servo system according to claim 2, wherein the control valve is operated using hydraulic pressure from the servo pump as a driving force. 5. The fluid pressure servo system according to claim 2, wherein the control valve operates using hydraulic pressure from the servo pump and hydraulic pressure from a hydraulic source other than the servo pump as driving force. Features a fluid pressure servo system. 6. A cylinder, a valve body provided reciprocally within the cylinder and having pistons formed at both ends, a first port communicating with an oil chamber formed at one end of the cylinder, and a first port communicating with an oil chamber formed at one end of the cylinder; a second port that communicates with an oil chamber formed at the other end of the cylinder; a third port that communicates with an oil chamber that is separated by both pistons and formed in the middle of the cylinder; A passage is provided that communicates an oil chamber formed in an intermediate portion with the first port, and the communication between the first port and the third port is provided based on the hydraulic pressure applied to the first and second ports. A control valve characterized in that communication and cutoff can be switched freely. 7. A rod cylinder having two oil chambers separated by a piston, having a rod cylinder portion formed with different pressure receiving areas on both sides of the piston, and three ports, wherein the piston is directed toward the one with the smaller pressure receiving area. A control valve section that shuts off three ports at the same time when moving, and internally communicates two specific ports when moving to the one with a larger pressure receiving area;
A rod cylinder characterized by being integrally formed.