JPH10115302A - Method and device for controlling pressure of hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect and control the pressure of a hydraulic cylinder, including a transient pressure during pressurizing, with high accuracy. SOLUTION: A tool horn 4 is moved up and down by a hydraulic cylinder 5 to ultrasonically weld a work. An upper room pressure P1 and a lower room pressure P2 are detected by pressure sensors 19, 20 and a pressure difference between them is determined by a calculation controller 21. The pressure of the hydraulic cylinder 5 is calculated on the basis of the pressure difference. The pressure is compared with a set value F' to control a three-position solenoid valve 15 and an ultrasonic oscillator 22 on the basis of the compared results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling a pressure of a hydraulic cylinder, and more particularly to a method and an apparatus for controlling a pressure of a hydraulic cylinder suitable for application to an ultrasonic machining apparatus.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional hydraulic cylinder applied to an ultrasonic machining apparatus. In FIG. 3, reference numeral 1 denotes a fixed horn to which vibration from an ultrasonic vibrator 2 is transmitted. The fixed horn 1 is fixed to the case 3 via a fixed flange 1a, and a tool horn 4 is connected to a lower end of the fixed horn 1. The hydraulic cylinder 5 that drives these up and down is provided with a piston rod 8
Is connected to the case 3 so that the tool horn 4 is moved up and down by driving the fluid pressure cylinder 5 so that the work 9 is welded.

The fluid pressure cylinder 5 reciprocates in a cylinder body 6 through which an upper chamber 10 and a lower chamber 11 are selectively supplied with pressurized fluid via an upper port 6a and a lower port 6b. A double-acting single-rod cylinder is provided with the piston 7 and the piston rod 8, and a regulator 12 is connected to the upper port 6a, and a speed control valve 13 is connected to the lower port 6b. Have been.

In general, at the time of welding, the timing of applying a pressure to the work 9 and applying ultrasonic waves are very important. In the conventional hydraulic cylinder 5, the pressure of the pressure fluid supplied to the upper chamber 10 is high. Is adjusted by a regulator to adjust the pressing force, and the timing of applying ultrasonic waves is uniquely determined by limit oscillation.

[0005]

In the conventional pressure control method for a hydraulic cylinder, since only the pressure of the fluid in the upper chamber 10 is controlled, the tool horn may be controlled depending on the pressure in the lower chamber 11. 4 may not be able to be applied, and it is difficult to know the transient applied pressure during pressurization. There is also a problem that the control is not easy even in the case of multi-stage pressurization in which the pressure is changed. Further, since the oscillation timing is uniquely determined, there is a possibility that ultrasonic vibration is applied to the work 9 in a state where the pressing force is insufficient, or conversely, ultrasonic vibration is applied to the work 9 in an over-pressurized state. In such a case, there is a problem that a good welding result cannot be obtained.

The present invention has been made in view of such a situation, and it is possible to accurately detect and control the pressurizing force of a fluid pressure cylinder, and to know a transient pressurizing force during pressurization. Provided is a method and apparatus for controlling a pressure of a fluid pressure cylinder, which can sufficiently cope with a case where the pressure needs to be changed frequently or a multi-stage pressurization in which the pressure is changed during pressurization. The purpose is to do.

Another object of the present invention is to control the timing of oscillation and the like in accordance with the pressing force when applied to an ultrasonic processing apparatus, and to control the pressing force of a hydraulic cylinder capable of performing high-quality welding management. A method and an apparatus therefor are provided.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a method for selectively supplying a pressurized fluid to an upper chamber and a lower chamber formed in a cylinder body to reciprocate a piston and a piston rod. In a dynamic type hydraulic cylinder, the pressure in the upper chamber and the lower chamber is detected respectively, the thrust of the hydraulic cylinder is determined based on the differential pressure, and the thrust is changed to control the pressing force. It is characterized by having done. Then, the thrust of the fluid pressure cylinder is obtained based on the pressure difference between the two chambers, and the thrust is changed to control the pressure, so that the pressure of the fluid pressure cylinder can be accurately detected. And
It is possible to know the transient pressure during pressurization, and it is fully compatible with the case where it is necessary to change the pressure frequently and the case of multi-stage pressurization where the pressure is changed during pressurization. It is possible to do.

The present invention is also characterized in that a tool horn for ultrasonic machining is attached to the piston rod. This makes it possible to control the timing of oscillation and the like in accordance with the pressing force during ultrasonic processing, thereby enabling high-quality welding management.

The present invention also relates to a double-acting hydraulic cylinder for selectively supplying a pressurized fluid to an upper chamber and a lower chamber formed in a cylinder body to reciprocate a piston and a piston rod. A pressure sensor for detecting the pressure in the lower chamber and a pressure sensor for detecting the pressure in the lower chamber; a calculating means for calculating the pressure of the fluid pressure cylinder based on the differential pressure based on the detection signals from the two pressure sensors; And control means for controlling supply and discharge and stop of the pressure fluid to and from the chamber. The pressures of the respective chambers are respectively detected by the pressure sensors, and the pressure of the fluid pressure cylinder is calculated based on the pressure difference between the two chambers by the calculating means. Even if it changes, it is possible to accurately detect the pressing force of the fluid pressure cylinder and also to know the transient pressing force during pressurization. In addition, since control means for controlling the supply and discharge and stop of the pressure fluid to and from each chamber based on the output signal from the arithmetic means is provided, it is necessary to frequently change the pressurizing force, Even in the case of multi-stage pressurization that changes the pressure,
It is possible to respond sufficiently.

The present invention is further characterized in that a tool horn for ultrasonic machining is attached to the piston rod. And by this, it becomes possible to control the timing of oscillation and the like according to the pressing force during ultrasonic processing,
This enables high-quality welding management.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows a pressure control device for a hydraulic cylinder according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a fixed horn to which vibration from an ultrasonic vibrator 2 is transmitted. The fixed horn 1 is fixed to the case 3 via a fixed flange 1 a, and a tool horn 4 is connected to a lower end of the fixed horn 1. The lower end of the piston rod 8 of the fluid pressure cylinder 5 that drives these up and down is connected to the case 3, and the tool horn 4 is moved up and down by driving the fluid pressure cylinder 5 to weld the work 9. It is supposed to be.

As shown in FIG. 1, the fluid pressure cylinder 5 includes a cylinder body 6 for selectively supplying a pressurized fluid to an upper chamber 10 and a lower chamber 11 via an upper port 6a and a lower port 6b. The piston rod 7 and the piston rod 8 that reciprocate in the main body 6 constitute a double-acting single rod cylinder.

The upper port 6a of the cylinder body 6 has:
As shown in FIG. 1, a center-closed three-position solenoid valve 15 is connected to the three-position solenoid valve.
7, a fluid pressure source (not shown) is connected via the check valve 18 and the regulator 12. The lower port 6b of the cylinder body 6 is connected to the three-position solenoid valve 15 via a speed control valve 13.
Is connected.

The three-position solenoid valve 15 is shown in FIG.
As shown in the figure, the first solenoid 15a is ON, the second solenoid 15b is OFF, and the regulator 12 is
a, the pressurized fluid is supplied to the upper chamber 10, the piston 7 descends, and the first solenoid 15a
F, the second solenoid 15b is ON, the regulator 12 is connected to the lower port 6b, and the pressurized fluid is supplied to the lower chamber 11 so that the piston 7 rises. Further, when the two solenoids 15a and 15b are OFF, the three-position solenoid valve 15 is in the closed state shown in FIG.
A pressure fluid is sealed in 0, 11 so that the piston 7 stops at a predetermined position.

As shown in FIG. 1, the pressures in the upper chamber 10 and the lower chamber 11 are constantly detected by pressure sensors 19 and 20, and the detection signals are input to an arithmetic and control unit 21. It has become so. The arithmetic and control unit 21 calculates the differential pressure between the two chambers 10 and 11 from the detection signals from the two pressure sensors 19 and 20, and calculates the pressing force of the fluid pressure cylinder 5 based on the calculated differential pressure. It has become.

As shown in FIG. 1, a set value F 'of the pressurizing force is input to the arithmetic and control unit 21. The pressing force of the cylinder 5 is compared, and the ON / OFF signal S ₁ of the first solenoid 15 a, the ON / OFF signal S _{2 of} the second solenoid 15 b, and the ultrasonic oscillator 2 for driving the ultrasonic vibrator 2 according to the comparison result. It has a control signal S ₃ of the wave generator 22 to output respectively.

Next, the operation of the present embodiment will be described. In the initial state shown in FIG. 1, the upper chamber pressure P ₁ is detected by the pressure sensor 19 and the pressure sensor 2
The lower chamber pressure P ₂ is detected by 0, both these detection signals are inputted to the arithmetic and control unit 21.

The arithmetic and control unit 21 obtains a differential pressure between the upper chamber pressure P ₁ and the lower chamber pressure P _{2 based} on the input of the two detection signals, and compares this differential pressure with a set value F ′. Then, a predetermined ON / OFF is determined based on the comparison result.
Signals S ₁ and S ₂ are output.

Incidentally, both signals S ₁ ,
S _2, the first solenoid 15a is ON, the second solenoid 15b is a signal OFF, the three position solenoid valve 15 is switched to the descending side from the position of closing shown in FIG. 1, the pressure fluid supply pressure P _O It is supplied to the upper chamber 10. As a result, the piston 7 descends, and the tool horn 4 is pressed against the work 9 with a predetermined pressing force F. Thereafter, ultrasonic generator 22 is activated by the control signal S ₃ output from the arithmetic and control unit 21 at a predetermined timing, the workpiece 9
Is ultrasonically welded.

Here, assuming that the total weight of the movable parts such as the tool horn 4 attached to the lower end of the piston rod 8 is M, and the pressure receiving area of the piston 7 is S, the pressing force F by the fluid pressure cylinder 5 is

[0022]

(Equation 1)

## EQU2 ## The upper chamber pressure P ₁ and a lower chamber pressure P
_After the upper chamber pressure P ₁ reaches the supply pressure P _O , the differential pressure with respect to 2 starts to change when the tool horn 4 comes into contact with the work 9,
After the lower chamber pressure P ₂ has become zero,

[0024]

(Equation 2)

Is constant. FIG. 2 is a graph showing this state. The upper graph in Figure 2 shows changes in the upper chamber pressure P ₁ and the lower chamber pressure P _2, also lower graph of Figure 2 shows the change in pressure force F corresponding thereto.

As is clear from FIG. 2, the upper chamber pressure P ₁
The three-position reaches the supply pressure P _O in the subsequently rises and time as soon as T ₁ of the solenoid valve 15, becomes constant thereafter.
On the other hand, the lower chamber pressure P ₂ is constant until the time T ₁ at which the tool horn 4 contacts the workpiece 9, gradually decreases after the tool horn 4 contacts the workpiece 9, and coincides with the upper chamber pressure P _1. after passing through the T _3, it becomes zero at time T _4. Therefore,
Pressure F is until time T ₂ begins to rise then zero, after becoming a M at time T _3, at time T ₄ reaches _{(P O · S + M)} . Then, it becomes constant thereafter.

The graph shown in FIG. 2 shows the supply pressure P _O
And shows the change when the pressure fluid supplied continuously to the upper chamber 10 of, for example, by returning the time T ₃ in three positions solenoid valve 15 to the closed state shown in FIG. 1, the pressure fluid both chambers 10 , 11 and the pressure F is constant at M.

The control signal S ₃ from the arithmetic and control unit 21
Is output at any timing are predetermined time T ₂ later. Thereby, for example, the maximum pressing force is set to Fma
x, Fmax is 0%, that is, tool horn 4
There or to start oscillation to output a control signal S ₃ at the time of the contact with the workpiece 9, or the pressure 1 / 2Fmax
It becomes possible to start the oscillation at the time when the state becomes. When the pressure becomes 1/2 Fmax, oscillation starts and welding is performed for 0.5 seconds.
Control such as raising the tool horn 4 after holding for 1 second at ax is also possible.

The inventor of the present invention installed a load cell in place of the work 9 shown in FIG. 1, and performed an experiment for comparing the applied pressure F calculated by the arithmetic and control unit 21 with the actual applied pressure measured by the load cell.

As a result, it was confirmed that the applied pressure F calculated by the arithmetic and control unit 21 and the actual applied pressure measured by the load cell matched very well. The arithmetic and control unit 21
It was also confirmed that the calculated pressurizing force F and the measured actual pressurizing force matched very well even when the set value F ′ input to the sample was variously changed.

Thus, the pressures in the upper chamber 10 and the lower chamber 11 are constantly detected, and based on the differential pressure, the hydraulic cylinder 5
Calculates the applied pressure of the pressure, so that the applied pressure can be accurately detected and controlled, and the transient pressure applied during pressurization can be known. By controlling according to the pressure, high-quality welding management can be performed.

In the above embodiment, the control of the pressure of the hydraulic cylinder 5 applied to the ultrasonic machining apparatus has been described as an example. However, the present invention is generally applied to various devices using the hydraulic cylinder 5. be able to.

[0033]

As described above, the present invention detects the pressures in the upper chamber and the lower chamber, obtains the thrust of the fluid pressure cylinder based on the differential pressure, and changes the thrust to apply the pressing force. Control, it is possible to accurately detect the pressure of the fluid pressure cylinder, to know the transient pressure during pressurization, and to change the pressure frequently. In this case, it is possible to sufficiently cope with a case where the pressing force is changed during the pressurization.

According to the present invention, since a tool horn for ultrasonic machining is mounted on the piston rod, the timing of oscillation and the like can be controlled in accordance with the applied pressure or the applied pressure can be controlled during the ultrasonic machining. It can be changed in multiple stages, so that high-quality welding control can be performed.

According to the present invention, the pressure in each chamber is detected by both pressure sensors, and the pressure of the fluid pressure cylinder is calculated by the calculating means based on the pressure difference between the two chambers. No matter how the pressure changes,
The pressure of the fluid pressure cylinder can be accurately detected, and the transient pressure during pressurization can be known. In addition, since control means for controlling supply and discharge and stop of the pressure fluid to and from each chamber based on an output signal from the arithmetic means is provided, it is necessary to frequently change the pressurizing force or to apply the pressurizing force during pressurizing. It is possible to sufficiently cope with the case where the pressure is multi-stage pressurized.

According to the present invention, since a tool horn for ultrasonic machining is attached to the piston rod, the timing of oscillation and the like can be controlled in accordance with the pressure during the ultrasonic machining, or the pressure can be adjusted in multiple stages. Or the like, whereby high-quality welding management can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a pressure control device for a hydraulic cylinder according to an embodiment of the present invention.

FIG. 2 is a graph showing changes in upper chamber pressure and lower chamber pressure and corresponding changes in pressure.

FIG. 3 is an explanatory view showing a conventional hydraulic cylinder applied to an ultrasonic processing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixed horn 2 Ultrasonic vibrator 3 Case 4 Tool horn 5 Fluid pressure cylinder 6 Cylinder main body 6a Upper port 6b Lower port 7 Piston 8 Piston rod 9 Work 10 Upper chamber 11 Lower chamber 12 Regulator 13 Speed control valve 15 Three-position solenoid valve 15a first solenoid 15b second solenoid 16 filter 17 filter regulator 19 pressure sensor 21 the arithmetic and control unit 22 ultrasonic generator S _1, S ₂ ON / OFF signal S ₃ control signal F 'setpoint P ₁ upper chamber pressure P ₂ Lower chamber pressure P _O supply pressure F Pressure

Claims (4)

[Claims] 1. A double-acting hydraulic cylinder for selectively supplying a pressurized fluid to an upper chamber and a lower chamber formed in a cylinder body to reciprocate a piston and a piston rod, wherein the upper chamber and the lower chamber are provided. A pressure control method for a fluid pressure cylinder, wherein the pressure of the fluid pressure cylinder is determined based on the differential pressure, the driving force of the fluid pressure cylinder is determined, and the pressure is controlled by changing the driving force. 2. A tool horn for ultrasonic machining is attached to a piston rod.
A pressure control method for a hydraulic cylinder according to the above. 3. A double-acting hydraulic cylinder for selectively supplying a pressurized fluid to an upper chamber and a lower chamber formed in a cylinder body to reciprocate a piston and a piston rod, wherein the upper chamber and the lower chamber are provided. Pressure sensor for detecting the pressure of each of the pressure sensors, calculating means for calculating the pressing force of the fluid pressure cylinder based on the differential pressure based on the detection signals from these two pressure sensors, and output signals from the calculating means Control means for controlling the supply and discharge and stop of the pressure fluid. 4. A tool horn for ultrasonic machining is attached to the piston rod.
A pressure control device for a fluid pressure cylinder as described in the above.