JPS5941042B2 - Servo mechanism - Google Patents

Description

[Detailed Description of the Invention] The present invention does not require the use of so-called high-grade servo valves.
This relates to a servo mechanism constructed using a very ordinary control valve.

In the conventional servo mechanism (for example, the one described in "Hydraulic and Pneumatic Handbook" published April 20, 1975, published by Ohmsha, page 533), the actuator 61 is connected by a servo valve 62 as shown in FIG. Drive.

The output displacement of the actuator 61 is fed back by the detector 63.

Thereby, the deviation from the command signal 64 is amplified by the amplifier 65, and the servo valve 62 is controlled by the output current.

The servo valve in such a servo mechanism is equipped with a torque motor 6 that converts an electrical signal into a mechanical signal, as shown in FIG.
6. Opposing nozzle flapper systems 67 and 68 that serve as hydraulic amplification, a four-way guide valve 70 that constitutes a control orifice 69, and a fixed orifice 7 that regulates the flow rate to the nozzle 67.
1. Since it is composed of a feedback spring 73 for positioning the spool 72, etc., it has a complicated structure, requires a high degree of processing accuracy, and cannot easily carry out maintenance such as maintenance and inspection.

Furthermore, if the nozzle 67, fixed orifice 71, etc. become clogged, the performance will be extremely degraded.

Therefore, in order to prevent the influence of dust, filters 74 are installed before and after the nozzle 67° fixed orifice 71, but this filter 74 also becomes clogged with dust, so the problem caused by dust cannot be solved. .

Also, one driving direction of the actuator 61 is set to the servo valve 62.
When the actuator 61 is switched, the pressure on the actuator 61 changes rapidly, causing shock and making it difficult to operate smoothly.

This problem cannot be solved by the servo valve itself, but only by the electric control circuit that drives the servo valve.

The present invention was invented in view of the above points, and by using a directional control valve equipped with a flow rate control section without using a conventional servo valve, the structure is simplified, the influence of dust is reduced, and maintenance and inspection are easier. maintenance is easy,
A further object of the present invention is to provide a servo mechanism that can smoothly switch actuators using hydraulic means without shock.

In order to achieve this object, the present invention has a configuration in which a first mainstream line branched from the discharge side of the hydraulic power source is connected to the rod side chamber of the actuator, and an element for controlling the pressure at a constant value is arranged in the mainstream line. At the same time, the second main flow line is connected to the P port of a three-port directional control valve having a transient all-port open characteristic, and the A port of the directional control valve is connected to the head side chamber of the actuator, The spool of the control valve switches and communicates the A boat with the P port and the T port, while connecting the addition point of the input signal transmission element and the actuator displacement feedback transmission element with the directional control valve as a deviation signal transmission element. A first flow control section is formed between the P port and the A port of the directional control valve, and a second flow control section is formed between the A port and the T port, and the first flow control section A servo mechanism in which a normally open pressure compensation valve that controls the differential pressure between the front and rear at a constant level is provided in the second main line, and the servo mechanism moves in a direction corresponding to the polarity of the deviation signal and moves in proportion to the deviation signal. The pressure in the head side chamber of the actuator is raised and lowered by adjusting the opening degrees of the first and second flow control parts using the spool of the directional control valve, which is set to The actuator is driven in the direction corresponding to the polarity of the deviation signal by the difference between the pressing force on the rod side and the actuator is driven in the direction corresponding to the polarity of the deviation signal, and when the input value of the input signal transmission element and the output value of the feedback transmission element match, the directional control valve is activated. Since the spool returns to a position where the pressing force on the rond side and the pressing force on the head side are balanced, the actuator stops at a position corresponding to the input value.

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, two main flow lines 2.3 are branched on the discharge side of the constant volume fluid pump 1 corresponding to the hydraulic power source device, and the first main flow line 2 is connected to the rod side chamber 5 of the actuator 4. The two main flow lines 3 are connected to the head side chamber 8 of the actuator 4 via a normally open pressure compensation valve 6 and a three port directional control valve T, and
An IJ IJ-) valve 11 is provided in a branched line 10 extending from the first main stream line 2 to the tank 9.

The IJ valve 11 is an example of an element that controls the pressure acting on the rod side chamber 5 to a constant value.

Further, the pressure compensating valve 6 pushes the main valve 14 to the left with a spring 13 provided in the back pressure chamber 12, so that the pressure control section 15 is opened in a normal state, and the pressure compensation valve 6 is connected to the first flow control section 24, which will be described later. The rear part of the first flow rate control part 24 is connected to the pilot chamber 17 at one end of the main valve 14 through the passage 16, and the rear part of the first flow rate control part 24 is connected to the passage 18.
The main valve 14 is configured to communicate with the back pressure chamber 12 at the other end of the main valve 14 through the respective back pressure chambers 12 .

Furthermore, the directional control valve 7 has a P port P, an A port A,
Equipped with three ports, T port T, and spool 2
A spring 21 is provided at the left end of the spool 20, and an electromagnetic portion 22 is provided at the right end of the spool 20. Also, during the switching transition period of the spool 20, the three ports P, A, and T are all connected to each other as shown in FIG. In other words, it has an all-port open characteristic during the switching transition period.

Therefore, the directional control valve 7 is a 3-port directional control valve with all ports open during the switching transition period, and between the P port P and the A port A, the left land 2
A first flow rate control section 24 is formed at the corner of the land 25 on the right side between the A port A and the T port T, and a second flow rate control section 26 is formed at the corner of the land 25 on the right side. Port 2 of said passage 18 between portions 24 and 26
7 is left open.

On the other hand, the output section of the actuator 4 is provided with a displacement detector 28 such as a potentiometer that transmits an electrical signal proportional to the displacement amount of the output section, and the detector 28 and an electrical addition/subtraction amplification device 29 are connected to each other. are connected via an electrical feedback circuit 30.

In addition, an electrical input circuit 3 is provided on the input side of the width increasing device 29.
1 is connected.

Further, the output side of the width increasing device 29 is connected to the electromagnetic section 22 of the switching transition period all-port open type three-port directional control valve 7 through an electric circuit 32.

The illustrated embodiment is constructed as described above.

The action will be explained below.

Since there is a pressure receiving area difference on both sides of the piston 4a corresponding to the piston rod 4b, when the pressures in both flow lines 2.3 are the same, the piston 4a moves to the left.

Therefore, as a result, the piston 4a can be stopped at an appropriate position by creating a pressure difference between the two flow lines 2 and 3 and balancing the forces acting on both sides of the piston 4a.

The control function of adjusting the pressure difference between the bidirectional flow lines 2 and 3 is performed by the directional control valve 7 as described below.

That is, on the discharge side of the hydraulic power source device (corresponding to this fluid pump 1), the first mainstream line 2 is sealed by the rod side chamber 5,
Since the second main flow line 3 is throttled by the pressure control section 15 and the first flow rate control section 24, the discharge pressure of the fluid pump 1 is controlled to the set pressure of the IJ IJ-) valve 11, and the rod side chamber 5 is A constant pressure controlled by the IJ-IJ valve 11 always acts.

Therefore, we temporarily set the set pressure of the IJ leaf valve 11 to 100.
kg/i, and if the both receiving areas of the piston 4a are 1:2, then the head side chamber 8 is 50 kg/cr? When the position reaches L, the piston 4a comes to rest.

In order to maintain the head side chamber 8 at 50 kg/cIl, the first
This is possible by communicating the head side chamber 8 with both the fluid pump 1 and the tank 9 at the same time as shown in FIGS.

Therefore, when the piston 4a is stationary, the directional control valve 7
As shown in FIGS. 1 and 3, all ports are open.

On the other hand, the displacement detection section 28 detects the displacement amount of the output section of the actuator 4, that is, the displacement amount of the piston rod 4b in the linear direction, and sends an electric signal with a numerical value proportional to the position of the output section via the feedback circuit 30. and transmits it to the addition/subtraction amplification device 29.

Therefore, if the value when the piston 4a is located at the right end of the actuator 4 is 0, and the value when the piston 4a is located at the left end of the actuator 4 is 100, then in the drawing, the piston 4a is located at the center of the actuator 4. Because it's located.

In the illustrated state, the displacement detector 28 is connected to the amplification device 29 at a
It sends a numerical signal.

Therefore, when a signal with a numerical value of, for example, 10 is applied from the input circuit 31 to the amplification device 29, a deviation of a numerical value of -40 is detected by the addition/subtraction amplification device 29, and the deviation signal of a numerical value of -40 is sent to the electric circuit 32. The electromagnetic part 22c is sent through the electromagnetic part 22c.

The directional control valve 7 has a function of controlling the position of the spool 20 in proportion to the current value applied to the electromagnetic part 22, and when a current corresponding to the deviation signal of the numerical value -40 as described above is sent, the spool 20 is displaced to the right from the neutral position.

Therefore, the directional control valve 7 is switched from the state shown in FIG. 3 to the state shown in FIG. It will be released.

As a result, the fluid discharged from the fluid pump 1 is supplied only to the rod side chamber 5, and the head side chamber 8 is opened to the tank 9', creating a force difference on both sides of the piston 4a, so the piston 4a moves rightward. Start moving.

Note that at this time, since the space between the back pressure chamber 12 and the tank 9 is wide open, the pressure control section 15 in the pressure compensation valve 6 is almost in a closed state.

As described above, when the piston 4a starts to displace to the right, the position of the piston 4a is sent moment by moment to the amplification device 29 by the displacement amount detector 28, and is added or subtracted from the input signal to the electromagnetic section 2.
Give commands to 2.

Therefore, in FIG. 1, the spool 20 is connected to the piston 4a.
Following this movement, the directional control valve 7 is switched from the state shown in FIG. 2 to the state shown in FIG.

Even if the directional control valve 7 is in the state shown in FIG. No jumping phenomenon occurs in the flow to port A.

After the P port P and the A port A communicate with each other as shown in FIG. 4, the opening ratio between both flow rate control units 24 and 26 is 50 kg/clI! When the relationship value reaches L and there is no difference in the forces acting on both the piston 4a, the piston 4a stops.

At this time, the position at which the piston 4a stops is the position 10 previously commanded via the input circuit 31.

In such a state, when a numerical value signal of, for example, 50 is applied by the input circuit 31, the addition/subtraction amplification device detects a deviation signal of +40 and sends a current corresponding to the deviation signal to the electromagnetic section 22. Since the transmission is made, the directional control valve 7 is switched to the state shown in Fig. 4, and the P port P and the A port A are
The A port A and the T port T are closed.

At the same time, the opening degree of the pressure control section 15 becomes larger, and the piston 4a begins to move to the left.

Initially, the opening degree of the first flow rate control section 24 is relatively large, but the feedback signal from the displacement amount detector 28 and the input circuit 3
The opening degree of the first flow rate control section 24 gradually decreases depending on the deviation signal from the input signal from the first flow rate control section 24.

During this time, the differential pressure before and after the first flow rate control section 24 is controlled to be kept constant by the action of the pressure control section 15.

Therefore, the flow rate supplied to the head side chamber 8 acts proportionally to the change in the opening degree of the first flow rate control section 24, and as shown in FIG. 3, all ports are opened, and the forces on both sides of the piston 4a are balanced. When this happens, the piston 4a stops.

In this way, as the opening degree of the first flow rate control section 24 decreases due to the action of the pressure control section 15, the flow rate from the P port P to the A port A is decreased in proportion to the decrease in the opening degree of the first flow rate control section 24 due to the action of the pressure control section 15. Since the supply amount is decreased in accordance with the opening degree of the first flow rate control section 24, the piston 4a stops gradually.

Note that the flow rate from A port A to T port T at this stop position is equal to the flow rate from P port P to A port A.
Needless to say, it is under pressure compensation operation.

Furthermore, as an element for controlling the pressure in the first mainstream line 2 to a constant value, a variable displacement type fluid pump 1a is used as shown in FIG. 6, and the pressure in the first mainstream line 2 is controlled by a control cylinder 1b. A structure that provides feedback can be considered.

1 to 4 show an input signal transmission element formed by an electrical input circuit 31, and a feedback transmission element formed from a displacement detector 28 engaged with the output section of the actuator 4 and an electrical feedback circuit 30. , the electrical addition/subtraction/amplification device 29 performs addition/subtraction/amplification and performs feedback control such as transmitting the results to the electric circuit 32, and this configuration is entirely electrical.

On the other hand, FIG. 5 shows an embodiment in which each of these elements is mechanically constructed.

That is, the oscillating operation bundle 37 can be oscillated about the substantially intermediate shaft 38 as a fulcrum, while the intermediate fulcrum 40 of the lever 39 whose one end is engaged with the output portion of the actuator 4 and the lower end of the operation bundle 37 The other end of the lever 39 and one end of the spool 20 of the directional control valve 7 are connected via a connecting rod 42.

Therefore, when the bundle 37 is operated in the direction of the arrow with the shaft 38 as a fulcrum and the lever 39 is displaced as shown in the imaginary line, the spool 20 moves to the right.

The space between P boat P and A boat A is sealed off, and the space between A port A and T port T is opened.

Therefore, the piston 4a moves rightward and rotates the lever 39 counterclockwise about the intermediate support 40.

As a result, the spool 20 returns to the illustrated state, and the piston 4a stops when the pressures acting on both sides of the piston 4a are balanced.

As described in detail above, the present invention connects the first mainstream line 2 branched from the discharge side of the hydraulic power source device to the Rondo side chamber 5 of the actuator 4, and includes an element for controlling the pressure at a constant value in the mainstream line 2. At the same time, the second main flow line 3 is connected to the P port PQ of a three-port directional control valve 7 having an all-port open characteristic during a transition period, and the A port of the directional control valve 7 is connected to the
Port A is connected to the head side chamber 8 of the actuator 4.

The spool 20 of the directional control valve 7 switches the A port A to the P port P and the T port T, and connects the addition point of the input signal transmission element and the actuator displacement feedback transmission element to the direction. The first flow rate control section 24 is connected to the control valve 7 via a deviation signal transmission element, and the first flow rate control section 24 is connected between the P port P and the A port A of the directional control valve 7, and the first flow rate control section 24 is connected between the A port A and the T port T of the directional control valve 7. A normally open pressure compensating valve 6 is provided in the second main flow line 3 to form a second flow rate control section 26 therebetween, and to control the differential pressure before and after the first flow rate control section 24 to a constant value. These valves 6 and 7 are different from so-called high-grade servo valves and are composed of very ordinary control valve elements. In particular, the directional control valve 7 has both flow control parts 24 and 26 underlapping. Because all ports are open during the transition period, the amount of underlap is zero (rubbing).There is no need for high processing precision like with conventional servo valves.

The structure can be simplified, and maintenance such as maintenance and inspection can be made easier.

Moreover, it has the advantage that the influence of dust is small.

Moreover, the pressure compensating valve 6 constantly compensates the pressure of the first flow rate control section 24, and at the time of switching, the three ports P, A, T
Since these are in communication with each other, the pressure change in the head side chamber 8 of the actuator 4 is small.

Therefore, there is an effect of alleviating the shock caused when the actuator 4 is started or stopped.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS.
This figure is an explanatory view of the operation in which both figures are illustrated symbolically, and FIGS. 5 and 6 are explanatory views of other embodiments. FIGS. 7 and 8 are explanatory diagrams of conventional examples. 1... Fluid pump, 2, 3... Mainstream line, 4... Actuator, 5...
Rod side chamber, 6...Pressure compensation valve, 7...
・3-port directional control valve, 8...Head side chamber,
11... Relief valve, 15... Pressure control section, 20... Spool, 24... First flow rate control section, 26... second flow control section, P;
A, T...Port.

Claims (1)

[Scope of Claims] 1. A first mainstream line 2 branched from the discharge side of the hydraulic power source device is connected to the Rondo side chamber 5 of the actuator 4, and an element for controlling the pressure to a constant value is provided in the mainstream line 2. At the same time, the second main stream line 3 is connected to the P port of a three-port directional control valve 7 having a transient all-port open characteristic, and the A port of the directional control valve 7 is connected to the actuator 4.
The spool 20 of the directional control valve 7 connects the A port to the P port. The addition point of the input signal transmission element and the actuator displacement feedback transmission element is connected to the directional control valve 7 via the deviation signal transmission element, and the directional control valve 7 A first flow control section 24 is formed between the P port and the A port, and a second flow control section 26 is formed between the A port and the T port, and the differential pressure before and after the first flow control section 24 is controlled to be constant. A servo mechanism characterized in that a normally open pressure compensation valve 6 is provided in the second main flow line 3. 2. The servo mechanism according to claim 1, wherein the element for controlling the pressure in the first mainstream line 2 to a constant value is constituted by an IJ valve 11 connected to the first mainstream line 2. 3. A structure that connects the addition point of the human power signal transmission element and the actuator displacement feedback transmission element and the directional control valve 7 via the deviation signal amplification transmission element is connected to the electrical input circuit 31 and the output part of the actuator 4. An electrical feedback circuit 30 connected to the provided displacement detector 28 is connected to an electrical addition/subtraction amplification device 29, and the amplification device 29 and the electromagnetic portion 22 of the directional control valve 7 are connected via the electric circuit 32. The servo mechanism according to claim 1, which is configured in a connected manner. 4. A structure that connects the addition point of the human power signal transmission element and the actuator displacement feedback transmission element and the directional control valve 7 via the deviation signal transmission element is connected to one end of the swing type operation bundle 37 and the output of the actuator 4. One end is connected to the intermediate fulcrum 40 of the lever 39, which has one end engaged with the part, via a link 41. Claim 1: One end of the spool 20 of the directional control valve 7 and the other end of the lever 39 are configured via a connecting rod 42.
Servo mechanism described in section.