JPS6388304A - Piston speed controlling method of air cylinder and control valve thereof - Google Patents

Abstract

PURPOSE:To allow the smooth stop of a piston even if the inertia of a load is large by combining an air cylinder with air flow control valves and a controller which automatically controls sensors and the openings of air flow control valves. CONSTITUTION:Air flow control valves 20 and 20a are constructed such that the passage of needle valve 21 whose opening is manually adjusted and the passage of needle valve 23 whose opening is adjusted with a piezoelectric element 22 are respectively and independently provided to one inflow port 26. On a double acting air cylinder 3 are installed sensors 30-35, which sense the position of a piston 2, and whose signals are inputted to a controller 24. An output from the controller 24 controls the voltage to be given to the piezoelectric element 22. Since this constitution makes it possible to decrease a pressurizing force before the piston 2 reaches the end of the air cylinder 3 and to decelerate the piston 2, it is possible to make a smooth stop even if the inertia of a load is large.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is capable of adjusting the piston operating speed of an air cylinder, which is often used as a driving part of industrial machinery, to an arbitrary speed at the start and end positions of the piston. The present invention relates to a method of deceleration and control and a control valve used therefor.

[Prior art] The basic directional control method for double-acting air cylinders is as follows:
As shown in Figure 4, an air cylinder ■ having a piston rod ■ and a piston ■, a flow rate regulating valve ■■a having a check valve ■ and a manual needle valve ■, and an air inlet that can be switched by operating the spool [phase] ■■a and outlet■■a and exhaust port■■
A control circuit is used consisting of a four-way control valve (1) with a.

In addition, 0. [Phase] is the air inlet and outlet of the air cylinder ■.

Further, FIG. 5 is a longitudinal cross-sectional view of the flow ffi adjusting valve (■■a).

Now, when moving the piston ■ of the air cylinder [3] to the right in Fig. 4, air flows through the inlet ■→outlet of the four-way control valve 0→the check valve ■of the flow rate adjustment valve■. The air passes through the manual needle valve (■) in parallel and is supplied to the air inlet (@) of the air cylinder, and moves to the position indicated by the two-dot chain line in the figure. At this time, the air on the right side of the piston (2) passes from the air inflow/outlet port 0 of the air cylinder to the manual needle valve (2) of the flow rate adjustment valve (2), and is exhausted to the atmosphere from the exhaust port (2) of the four-way control valve [21].

When moving the piston ■ to the left, the inlet ■a, outlet ■a, and exhaust port ■a move to the left by switching the spool [phase] of the four-way control valve [21], and the air flows in the opposite direction. flows to

In such a configuration, the flow rate of the exhaust air is regulated according to the opening degree of the manual needle valve ■■, so the moving speed of the piston ■ can be set arbitrarily, except in the acceleration range at the beginning of piston operation. The speed can be set to a constant speed.

[Problems to be Solved by the Invention] In the configuration shown in FIG. acts on the piston ■, the piston rod ■, and the load (not shown) connected to it to exert a force to move it in the right direction against the inertial resistance and load resistance, thereby causing the piston ■
is accelerated until its movement speed reaches a constant speed. Furthermore, even when the piston ■ reaches near the right end of the air cylinder [3], the air pressure acting on the left side of the piston ■ does not change, so there is a problem that the piston ■ violently collides with the right end of the air cylinder [3]. Ta. The relationship between the piston position and piston speed in such a conventional case is shown by a broken line in FIG.

Conventionally, cushions of various types have been installed just before the piston ■ collides with the left and right ends of the air cylinder [3] to alleviate the impact force, but the inertia of the load If it was too large, it would not be possible to stop smoothly.

[Means for solving the problems] As shown in FIG.
Air flow control valve [phase] [phase] a as shown in the figure, sensors [phase] to @ and the air flow control valve [phase] [phase] a
The conventional problems are solved by using a control device that automatically controls the opening degree of the valve.

In other words, as shown in Fig. 2, the air flow total control valve [phase] [phase] a is a flow path of a needle valve [21] whose opening degree is manually adjusted for one inlet [phase]. A needle valve 0 whose opening degree is adjusted by a piezoelectric element C or the like is provided independently, and such an air flow control valve [phase] @la is shown in Fig. 1. The double-acting air cylinder [3] has a permanent magnet on its outer periphery, and is installed symmetrically at the air outlet 0■ at the left and right ends of the double-acting air cylinder [3]. A sensor [phase] ~0 is provided to detect the position of piston ■, and a sensor ~Q is provided at the right end to detect the position of piston ■. The control device controls the voltage applied to the piezoelectric element 0 of the air flow control valve [phase] [phase] a to control the opening degree of the needle valve 0, using the signals sent from these sensors. It is configured to be adjustable so that the moving speed can be controlled to be reduced to an arbitrary speed at the start and end positions of the piston (2).

For the sensors [phase] to ■, for example, reed switches that are sensitive to magnetism are used, and the switches open and close when the permanent magnet @ attached to the piston ■ approaches, and the sensors [phase] The signal obtained from ~■ is
The voltage is transmitted to a transistor-type electronic or microcomputer-type control device, where it is converted into a DC voltage and supplied to the piezoelectric element Oo of the control valve. Piezoelectric element O
o is not shown because it is a general type, but its length extends in the vertical direction in proportion to the supplied voltage, and this serves to change the opening degree of the needle valve ■ [21] using appropriate amplification means. are doing. (2) is a known four-way control well.

In the above explanation, the piezoelectric element 0 that functions to change the opening degree of the needle valve [21] refers to a ceramic element that has the property of causing distortion when a voltage is applied to it. Even with a solenoid type device in which the core moves when voltage is applied, the same effect as a ceramic piezoelectric element can be obtained as long as the time from application of voltage to the core movement is short.

[Function] In FIG. 1, based on the piston position information obtained by the sensors [phase] to @, the air flow control valve [ shown in FIG.
The first example shows an example of controlling the opening degree of the needle valve [21] of phase] @1a.
Table 3 shows the piston movement speed diagram at that time.
As shown in the figure. What is shown by a solid line in FIG. 3 is the characteristic obtained as a result of the present invention, and what is shown by a broken line is the characteristic of the conventional method explained in FIG.

Table 1 Example of opening degree (%) of needle valve 0 when the piston moves 8 to the right At times, the sensor [phase] sends its signal to the electronic control unit 0, and the air flow control valve 0 and the needle valve 0 of [phase] a are 100% open (fully open). At this time, the needle valves of both control valves [phase] [phase] a are set to predetermined opening degrees.

Therefore, the maximum amount of compressed air is sent to the left side of the piston ■ in the air cylinder ■, and the piston ■ is rapidly accelerated as shown at the start of the curve at the left end of the graph in Figure 3 (indicated by a in the figure). Ru.

When the piston ■ moves to the position of the sensor ■, the air flow control valve [phase] remains at 100% opening, but the needle valve of the air flow control valve [phase] a is closed to the sensor [21]. Since the opening degree is changed to 50% via the control device 0 in response to the signal, the pressurizing force on the piston (■) decreases slightly, and in Fig. 3, the curve that curves between the straight line of rapid increase and the straight line of low speed ( (not shown in the figure).

When the piston ■ moves to the position of the sensor @, the needle valve Φ of the air flow control valve [phase] remains at 100% due to the signal of the sensor @, and the needle valve of the air flow control valve [phase] a can be changed to 0% (fully closed), so in the section from sensor 0 to Q, the opening degree of the preset manual needle valve [21] in the air flow control valve [phase] @laO is regulated. Perform speed movement (indicated by C in the figure).

When the piston ■ moves to the position of the sensor ■, the opening degree of the needle valve @ of the air flow control valve [phase] changes to 50%, and the opening degree of the needle valve @ of the air flow control valve [phase] A changes to 0% opening. As it remains the same, the pressure applied to the piston ■ decreases slightly.

When the piston ■ moves to the position of sensor 0, the needle valve 00 opening degree of the air flow control valve [phase] changes to 0% (fully open), and the needle valve of the air flow control valve [phase] a changes to 0% (fully open). Since the opening remains at %, the pressure applied to the piston (■) further decreases. As a result, between the sensor position 0 and @, the moving speed of the piston ■ is limited only by the opening degree of the needle valve [21] and becomes small.
The piston ■ serves to reduce the impact force that collides with the right end of the air cylinder [3].

When the piston ■ moves from the right to the left of the air cylinder [3] in the opposite way to the above, the sensors listed in Table 1 operate left and right, and the air flow control valve operates in reverse order. . Therefore, the piston speed also changes from left to right in FIG.

[Effects of the Invention] In the present invention, since the pressing force is reduced and the piston (3) is decelerated before reaching the end of the air cylinder [3], it is possible to stop the piston smoothly.

Furthermore, as is clear from Fig. 3, since the acceleration when the piston (2) starts moving from the end of the air cylinder [3] is gradual, there is an advantage that the starting impact force is small and the movement of the machine is smooth.

Furthermore, in the air flow control valve [phase] of the present invention, the same manual adjustment needle valve ■ as the conventional one is placed together with the needle valve 0, so that the air flow rate control valve [phase] is located in the constant speed range (between sensor @ and Q in Fig. 1). Delicate speed adjustments are made manually, and experienced technicians who place importance on experience and intuition can operate this manual valve in the conventional manner, so there is little psychological resistance.

[Brief explanation of the drawing]

FIG. 1 is a system diagram illustrating a method for controlling piston speed by combining an air flow control valve according to the present invention with an air cylinder. FIG. 2 is a longitudinal sectional view of the air flow control valve according to the present invention. FIG. 3 is a graph showing the relationship between piston stroke and moving speed. FIG. 4 is a system diagram illustrating a conventional method for controlling the piston speed of an air cylinder. FIG. 5 is a longitudinal sectional view of a conventional flow rate regulating valve. ■...Piston rod, ■...Piston, ■...
Air cylinder, ■...Check valve, ■...Manual needle valve,
■■a...Flow rate adjustment valve, ■■a...Inlet, ■■a・
・・Outlet, ■■a...Exhaust port, [phase] spool, ■・
・・4-way control valve, @■・・・Air inlet/outlet, [phase] [
Phase] a... Air flow rate control valve, ■... Manually operated needle valve, ■... Piezoelectric element, ■... Needle valve operated by piezoelectric element, ■... Control device, @ ...Permanent magnet, [Stock]...Inlet, 0@...Communication port, 0...Outlet,
[Phase]~■ is a sensor.

Claims (2)

[Claims] (1) For one inlet [26], the flow path of the needle valve [21] whose opening degree is adjusted manually and the flow path of the needle valve [23] whose opening degree is adjusted by a piezoelectric element [22] etc. Air flow control valves [20] and [20]a, each having an independent channel, are installed symmetrically to the air inlets and inlets [12] and [13] at both ends of the double-acting air cylinder [3]. A four-way control valve [11] is provided between the flow control valves [20] and [20]a, and a plurality of sensors [11] for detecting the piston position are provided near the left and right ends of the piston [2] in the air cylinder [3]. 30]～
[35] is provided, and the piezoelectric element [2
2] By controlling the voltage applied to [22], the needle valve [23][
23] A piston speed control method for an air cylinder, characterized in that the piston [2] is gradually moved from the beginning to the end of its operation by adjusting the opening degree of the piston [2]. (2) Two independent communication ports [27] [28] are formed for one inflow port [28], and the communication ports [27] [2
A valve seat is formed at the outlet of [8], and both communication ports [27
] [28] is provided, a needle valve [21] whose opening degree is manually adjusted is provided on one valve seat side, and a piezoelectric valve is provided on the other valve seat side. A control valve characterized by being provided with a needle valve [23] whose opening degree is adjusted by an element [22].