JPH036715A - Switch controller for open loop solenoid valve - Google Patents

Abstract

PURPOSE:To ensure a stable cycle action regardless of the environmental condition and the using condition by dynamically controlling each arrival time of the repeating actions. CONSTITUTION:When the first reciprocation of a load 12 is over, an internal memory 2a of a time counter circuit 2 stores the actual arrival times Ta and Tb of the initial valve Ts and the reciprocation of the load 12 respectively. At the second going movement, the circuit 2 produces an output equivalent to the time difference DELTATa = Ta - Ts. Then the gain control of the input signal applied to an amplifier 4 is carried out with the correcting operation of a correction circuit 3. Hereafter the arrival times Ta and Tb are constantly controlled with repetition of said gain control and by the energizing current control of a control valve 14 based on the result of comparison obtained between the value Ts and the corresponding actual result preceding by one cycle for each cycle of each reciprocation. As a result, a stable cycle action is attained regardless of the environmental condition and the using condition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an open-loop solenoid valve switching control device, and in particular to a hydraulic control device using a pair of position detectors and an electromagnetic directional control valve in an open-loop control system. The present invention relates to an electromagnetic valve switching control device for moving a load connected to the hydraulic actuator between a first position and a second position by controlling the positioning of the actuator.

[Prior art] When using a hydraulic cylinder to reciprocate a load such as a machining table on a machine tool, start and stop positioning is performed by incorporating position detectors such as limit switches and proximity switches at the start and stop positions. Generally, the output is used to open and close an electromagnetic switching valve.

FIG. 2 shows an example of the configuration of a conventional general device.

In FIG. 2, hydraulic cylinder 21 drives a load 22, and limit switches 23a and 23b are actuated by load 22 to detect when it reaches a first position and a second position. The hydraulic cylinder 21 is connected to the electromagnetic directional control valve 24 and the flow rate i! The solenoid devices a and b of the electromagnetic directional control valve 24 are connected to a hydraulic power source 26 via an electric circuit 20 and a start/stop command signal and detection signals from the limit switches 23a and 23b. It is designed to control excitation switching.

Now, when the solenoid device a is excited via the electric circuit 20 by the start command signal S1, the piston rod of the cylinder 21 is extended and the load 22 is moved forward. When the load 22 reaches the limit switch 23b, the limit switch 23
The signal from b deenergizes solenoid device A via electric circuit 20, and energizes solenoid device a instead. As a result, the direction of the pressure oil to the cylinder 21 is reversed, and the cylinder 21 retracts its piston rod, so that the load 2
2 is set back. When the load 22 reaches the limit switch 23a, the solenoid device a is deenergized by a signal from the limit switch 23a, and the solenoid device A is energized instead. In this way, the load 22 is repeatedly moved back and forth until the stop command signal S2 is given. The operating speed of the hydraulic cylinder 21 during this time is controlled by the flow rate control valve 25.

[Problems to be Solved by the Invention] In the device shown in Fig. 2, in order to perform smooth operation without shock when starting and stopping, the electromagnetic switching valve itself has a change in opening when switching. It is common to use a cylinder with a hydraulic throttle added so that the operation is performed gradually, but in this case, the speed pattern of the cylinder operation is uniquely determined by the switching characteristics of the electromagnetic switching valve, and it is possible to avoid shocks. It is not possible to perform the operation at an arbitrary speed pattern.Also, the start and stop positions are detected by limit switches, so it is possible to keep them within a certain accuracy range, but for example, when controlling a cycle operation, it is difficult to control the reciprocating period. If temporal reproducibility is also expected, the flow rate supplied to the cylinder must be strictly controlled against changes in temperature, which is troublesome.

That is, in this method, the accuracy of the reached position is maintained by the limit switch, but as shown in Figure 3, there is a restriction that the time integral value of the flow rate Q is constant for the arrival time T1 from the starting point ○. , when the flow rate Q slightly changes by ΔQ, the arrival time also changes, for example, T2 (=TI +ΔT)
becomes. In controlling this flow rate Q, the longer the arrival time, the longer the integral, and the smaller the pressure-receiving area of the cylinder, the more it appears as a time error, so ΔT must be strictly controlled to zero due to the limit of oil pressure fz amount control. That is impossible.

This can be achieved by using a proportional electromagnetic directional flow control valve as the electromagnetic switching valve shown in Fig. 2 to achieve a shock-free switching operation, or by generating a desired speed pattern with an electric circuit so that the starting and stopping positions can be adjusted to the desired position. The so-called open-loop control method using a detector has a fatal flaw in that the arrival time varies each time during repeated operation.

In this way, in conventional methods, in order to suppress variations in the arrival time of each retraction operation, it is necessary to control the temperature of the hydraulic oil in the hydraulic circuit very strictly, reduce drift in the electric circuit system, etc. I was forced to change the system to AM, and I was disappointed that it was less effective.

The purpose of this invention is to dynamically control the arrival time of each repeated operation in the open-loop control system described above, thereby realizing stable cycle operation unaffected by environmental and usage conditions. An object of the present invention is to provide a solenoid valve switching control device.

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the oven-lube solenoid valve switching control device of the present invention employs an open-loop control system using a pair of position detectors and a solenoid directional control valve. A load connected to the hydraulic actuator is moved between a first position and a second position by controlling the positioning of the hydraulic actuator, wherein the electromagnetic directional control valve electrically inputs the flow rate of passing pressure oil. A control valve means such as a proportional electromagnetic control valve or a servo valve is provided to control the signal to a value proportional to the signal, and as a control system for the input signal to the control valve means, the control valve means is provided with a control valve means that controls the signal to a value proportional to the signal, and as a control system for the input signal to the control valve means, the control valve means is provided with a control valve means that controls the signal to a value proportional to the signal. a time measuring means for measuring the arrival time of and outputting a correction signal corresponding to the time difference with the initial value of the internally stored information; and a predetermined signal change for giving a speed pattern between starting and stopping of the hydraulic actuator. a pattern generating means for generating a control signal that changes over time in a pattern; an amplifying means for amplifying the control signal output from the pattern generating means and supplying it as the input signal to the control valve means; and gain correction means for correcting the gain for the control number 43 so that the time difference is reduced by the correction signal.

[Function] The open loop solenoid valve switching control device of the present invention includes a pair of position detectors and a control valve such as a proportional type 68 control valve or a servo valve that controls the flow rate of passing pressure oil to a value proportional to an electrical input signal. means for controlling the positioning of a hydraulic actuator in an open-loop control manner, thereby repeatedly moving a load coupled to the hydraulic actuator between a first position and a second position. For reciprocating movement, the direction of the pressure oil of the υ control valve means is switched by switching the input terminal of the control valve means to an electro-hydraulic drive system such as a solenoid device or a force motor. The speed pattern of the hydraulic actuator during the stroke period is controlled over time by changing the change over time of the input terminal during each period in accordance with a control signal of a predetermined signal change pattern generated from the pattern generating means. be done.

The time measuring means measures the arrival time between the first and second positions due to the movement of the load based on, for example, signals from the pair of position detectors, and stores an initial value of this arrival time as internally stored information. can be memorized. This initial value may be programmed in advance and written into memory, or may be the arrival time between the first and second positions for a predetermined period of the reciprocating motion of the load. The time measuring means itself may measure the value and store it as an initial value. In this case, the period may preferably be one period or a plurality of periods in a stable operating state; The average value between them may be taken as the initial value. The time measuring means further takes in each arrival time and outputs a correction signal corresponding to the time difference from the initial value.

The gain correction means corrects the gain for the control signal so that the time difference is reduced by the correction signal from the time measurement means, thereby keeping the arrival time of each time substantially constant with the corresponding initial value of the outbound or return trip. Gain correction of the electrical system is performed so that the Of course, the initial values may be the same for the outbound and return trips, or may be different.

In this way, in the device of the present invention, the arrival time of each cycle of the reciprocating movement of the load by the hydraulic actuator is taken into the electrical system of the control valve means as an actual value every time, and when a difference from the stored initial value occurs. correct this in the next cycle,
In this way, the arrival time each time is kept almost constant.

In order to further clarify the features and advantages of the present invention, preferred embodiments of the present invention will be described below with reference to the drawings.

[Embodiment] Fig. 1 shows an embodiment of the present invention, in which a hydraulic cylinder 11 drives a load 12, and limit switches +3a and 13b are actuated by the load 12 to bring it into the first position. Detecting that the second position has been reached. The hydraulic cylinder 11 is connected to a hydraulic power source 16 via a proportional electromagnetic directional flow control valve 14, and the electric control circuit 10 switches the excitation current to the solenoid devices a and b of the control valve 14 to supply the hydraulic cylinder 11. The direction of the pressure oil and therefore the reciprocating movement of the load 12 is controlled.

The electric control circuit 10 includes a pattern generator 1, a time measurement circuit 2, a gain correction circuit 3, a drive amplifier 4, and a timing control circuit 5, and controls the control valve 14 when receiving a start signal S. The switching operation is started and stopped when the stop signal S2 is received.

When the pattern generator 1 receives the start signal S or the pulse signal from the timing control circuit 5, the pattern generator 1 changes in a predetermined setting pattern over time, which is set the same or separately during the round trip of the load movement. A control signal is outputted with a desired gain set and adjusted by an internal gain setter 1a.

In this embodiment, the time measurement circuit 2 is constituted by a microcomputer such as a programmable controller having an internal memory 2a, and can programmably set the arrival time of the load 12 between the two limit switches to a desired value as an initial value Ts. be. The time measuring circuit 2 also has a function of receiving load arrival detection signals from the limit switches 13a and 13b and detecting the arrival time of the load at that time between the two limit switches using an internal clock, and for example, detects the arrival time of the load at that time between the two limit switches. For example, when a load that has started reciprocating operation with the start signal Sl reaches the desired stable operating state with the program set, the load at that time can be changed by giving the start signal or another write command signal at any time. It has a function of rewriting the contents of the internal memory 2a by taking in the value for one cycle of the arrival time or the average value for a plurality of cycles as the initial value Ts.

Furthermore, this time measurement circuit 2 compares the arrival time T detected each time the load 12 is moved with an initial value T5 stored in the memory 2a separately for each period of the forward and return trips, and determines the actual time. It has a function of outputting a correction signal corresponding to the time difference ΔT=T−T between the arrival time and the stored initial value every time for each period of the forward and backward paths.

The gain correction circuit 3 multiplies the control signal from the pattern generator 1 and the correction signal from the time measurement circuit 2 by a predetermined gain adjustment performed by an internal adjuster 3a using a multiplier 3b. The gain correction is performed by adding the correction amount obtained by the adder 3c to the control signal. The correction gain by the adjuster 3a is set in advance to a value that can provide a correction amount commensurate with the time lag of six teeth. In the illustrated example, the gain correction is obtained using the multiplier 3b, but
Almost the same effect can be obtained even if it is constructed using an adder circuit in a pseudo sense.

The control signal corrected by the gain correction circuit 3 is current-amplified by the drive amplifier 4, and is then applied to each solenoid device a, b.
given alternately. Switching of the excitation 6B current to the solenoid devices a and b is performed by controlling the switching circuit 4a in the amplifier 4 using a pulse signal from the timing control circuit 5 which operates in response to contact signals from the limit switches f3a and 13b. be exposed. The timing control circuit 5 also serves to reset the pattern generator 1 with its output pulse signal.

The operation of the embodiment device having the above configuration is as follows.

First, it is assumed that two limit switches 13a and 13b are arranged at a predetermined distance ML, and the load 12 moves between them for a predetermined time T. This time Ts is written in the memory 2a in the time measuring circuit 2 as an initial value, and the load 12 starts without shock during the time T, and the distance l! Set a smooth flow control pattern to stop without shock at IL.

When the load 12 is in a position where the limit switch 13a is actuated, when a start signal s1 is applied to the control circuit 10, an excitation current that changes over time according to the control signal from the pattern generator 1 is transmitted from the amplifier 4 to the solenoid device a. given to. In this case, since the time measurement circuit 2 is programmed so that its output correction signal is zero for the first movement period of the load 12 in the direction of No corrections are required. The excitation current flows through the solenoid device a, which causes the control valve 14 to supply pressure oil from the pressure oil supply source 16 to the hydraulic cylinder 11 according to the time-varying pattern of the control signal.
This causes the load 12 to start smoothly without shock and head toward the limit switch 13b.
Limit switch 1 when load 12 starts at this time
Upon receiving the contact signal 3a, the time measuring circuit 2 starts measuring time.

The load 12 moves at a predetermined speed pattern according to the above pattern, and when it reaches near the limit switch 13b, it gradually decelerates according to the set speed pattern and switches the limit switch! 3b and when it is activated, the time required up to that point, that is, the arrival time T of the outward journey, is detected within the time measuring circuit 2 and stored in the internal memory 2a. At this time, the switching circuit 4a in the amplifier 4 is actuated by a pulse signal from the timing control circuit 5 based on the contact signal from the limit switch 13b, which de-energizes the solenoid device a and brings the control valve 14 to the neutral position. Returning, the pattern generator 1 is also reset.

The same goes for the return trip, but in order to start the load 12 on the return trip, the pattern generator l outputs a control signal according to the corresponding setting pattern in response to a start signal or a pulse signal from the timing control circuit 5, and the switching circuit 4a This is done by energizing the solenoid device. Let T be the actual arrival time measured on this return trip and stored in the memory 2a.6 When the first round trip of the load is completed, the initial value TS and the load 12 are stored in the internal memory 2a in the time measuring circuit 2. The actual arrival times T1 and T, respectively, for the round trip will be stored.

The start of the second outward movement is initiated by a pulse signal from the timing control circuit 5 caused by the load actuating the limit switch 13a at the end of the first return movement. In this case, the control of the excitation 61i current is almost the same, but the time measurement circuit 2 generates an output corresponding to a time difference of ΔT-=T--Ts, which is corrected by the gain adjuster 3a in the correction circuit 3. After being given a gain K, it is multiplied by the control signal from the pattern generator 1 by the multiplier 3b and added to the control signal by the adder 3C as a correction signal. This correction operation controls the gain of the input signal to the amplifier 4. For example, if ΔT is positive, the gain is increased and the flow rate to the cylinder 11 is relatively increased with a similar pattern compared to the forward movement in the previous cycle. As you do,
Conversely, when ΔT1 is negative, automatic control is performed such that the gain is reduced and the flow rate to the cylinder 11 is relatively reduced while maintaining a similar pattern compared to the forward movement in the previous cycle.

The same goes for the second return trip, and at the end of the second outbound trip, the load activates the limit switch 13b, causing the switching circuit 4a to turn off the solenoid device a with a pulse signal from the timing control circuit 5. b is excited and the pattern generator 1 is reset to invert the load 12. In this case as well, the control of the excitation current is almost the same, but it goes without saying that the correction operation is performed based on the signal corresponding to the time difference of ΔT b =T b −T s output from the time measurement circuit 2. .

Thereafter, by repeating this process, for each cycle of each round trip, the arrival time is determined based on the result of comparing the internally stored initial value Tg with the actual value of the corresponding previous cycle. Constantly controlled by current control.

In this embodiment, a proportional electric 61-way flow rate control valve is used as the control valve 14, but the same effect can be obtained by replacing it with another proportional valve or an electro-hydraulic servo valve.

Furthermore, although this embodiment shows a case where the correction operation is performed for each of the reciprocating movements of the load, the present invention does not exclude the case where the correction operation is applied only to either the outward or return movement, and It is also applicable to a case where the current is controlled by a pattern generator so that the control flow rate to the actuator is changed stepwise for each position detected by a plurality of position detection means during movement of the actuator.

[Effects of the Invention] As described above, the present invention is effective in simultaneously accurately controlling the position and operation time in hydraulic control of a hydraulic actuator that repeatedly moves a load between three positions at a predetermined speed pattern. By using control valve elements such as proportional electromagnetic flow control valves in open-loop control, the operating time of each repeated operation can be dynamically controlled, resulting in stable cycles regardless of environmental and usage conditions. It is possible to realize the operation.

4: Drive amplifier lO: Electrical control circuit 12: Load 16: Hydraulic supply source 5: Timing control circuit ll: Hydraulic cylinder 13a, 13b: Limit switch 14: Proportional electromagnetic directional flow control well

Claims (1)

[Claims] By controlling the positioning of a hydraulic actuator in an open-loop control method using a pair of position detectors and an electromagnetic directional control valve, a load connected to the hydraulic actuator is moved between a first position and a second position. The electromagnetic directional control valve has a control valve means such as a proportional electromagnetic control valve or a servo valve that controls the flow rate of the passing pressure oil to a value proportional to an electrical input signal, and the electromagnetic directional control valve As a control system for input signals to the valve means, a time for measuring the arrival time between the first and second positions due to the movement of the load and outputting a correction signal corresponding to the time difference from the initial value of the internally stored information. a measuring means; a pattern generating means for generating a control signal that changes over time in a predetermined signal change pattern to provide a speed pattern between starting and stopping of the hydraulic actuator; and a pattern generating means output from the pattern generating means. comprising an amplifying means for amplifying a control signal and supplying it as the input signal to the control valve means; and a gain correcting means for correcting the gain for the control signal so that the time difference is reduced by a correction signal from the time measuring means. An open-loop solenoid valve switching control device featuring: