JPH11141696A - Spool type direction selective valve system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an actuator accurately by operating a spool in strict conformity to the command value of an operational signal even in case a force other than the pilot pressure, such as a fluid force or friction force, acts on the spool. SOLUTION: At the two ends of a spool 2, pressure sensors 20a and 20b are installed so as top be in contact through springs 10a and 10b, and from the signals generated, a controller 40 calculates the hydraulic force Fa due to the pilot pressure acting on the spool 2 and the actual driving force Fm acting on the spool 2 actually. The ratio Fa/Fm is multiplied by the command value Voa of an operational signal 50 to calculate the feedback correction value Vr for the hydraulic force, and from the command value of the operational signal, the obtained correction value is subtracted, and thus the command value undergoes a correction. The corrected command values V30a and V30b are fed to solenoid valves 30a and 30b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spool-type directional control valve used in a hydraulic / pneumatic system, and more particularly, to switching an output port of an inputted fluid by changing a pilot pressure by changing a pilot pressure by a solenoid valve. The present invention relates to a spool-type directional switching valve system of a solenoid valve driving type for controlling a flow rate of a fluid.

[0002]

2. Description of the Related Art FIG. 12 shows an example of a conventional spool type directional switching valve system driven by an electromagnetic valve.

In FIG. 12, a spool type directional control valve 2
The housing 201 is provided with a pump port P connected to a main hydraulic pump, tank ports T1 and T2 connected to a tank, and actuator ports C1 and C2 connected to an actuator. Switching is performed by the spool 202.
The spool 202 is operated by introducing pilot pressure from solenoid valves 230a and 230b to pressure chambers A and B provided at both ends of the spool. The pressure chambers A and B are formed in flanges 261 and 262 attached to the housing 201.

A spring 207 for positioning the spool 202 and spring seats 205 and 206 are provided with bolts 20.
It is secured to one end of the spool 202 by 8 and these parts are housed in a flange 262.

The spool 202 has solenoid valves 230a, 230
It moves to the left and right in accordance with the pilot pressures guided from b to the pressure chambers A and B, and the position is determined when it is balanced with the spool positioning spring 207, and stops. At this time, the pump port P is connected to either the actuator port C1 or C2, and a flow rate according to the position of the spool 202 is supplied from the pump port P to the actuator port C1 or C2.

The solenoid valves 230a and 230b are connected to a hose 231.
a, 231b are connected to the flanges 261, 262, respectively, and the solenoid valves 230a, 230b are connected to the hose 2
32 to the pilot pump 233 and the hose 23
4 are connected to the tanks 235 respectively. The solenoid valves 230a and 230b operate according to the current value from the controller 260. For example, when it is desired to move the spool 202 to the left side, the solenoid valve 230a opens by outputting only the command current 251a, the pressure in the pressure chamber A rises, and the spool 202 moves.

FIG. 13 shows details of the controller 260.

In FIG. 13, an operation lever angle signal (operation signal) 250 from the command means is transmitted to a controller 260.
To calculate the command value and determine the output direction of the command value. The amplifiers 246a and 246b output one of the command currents 251a and 251b based on the processing result. With this signal, the spool 2 can be moved as described above.

In this case, a fluid force (flow force) acts on the spool 2, so that a desired flow rate cannot be obtained. As a method for solving this, Japanese Utility Model Laid-Open No. 5-22964 discloses a spring constant of a control spring acting on a spool and an opening degree of a fluid force per unit amount of a differential pressure across a throttle formed by movement of the spool. It has been proposed to select the spring constant of the control spring such that the ratio of the change rate to the control value becomes an optimum value (3.5 Mpa or more).

[0010]

In the conventional spool type directional control valve shown in FIG. 12, the spool 202 is moved by the pilot pressure guided to the pressure chamber A or B as described above. At this time, a fluid force or a frictional force acts on the spool as a disturbance, causing an error in the spool opening.

That is, the spool 202 originally has the pressure chamber A
Or, it moves by the force acting by the product of the pressure acting on B and the pressure receiving area of the spool end portion, and stops at a position where the spring force generated by the deformation of the spool positioning spring 207 is balanced, so that the characteristic becomes linear. Therefore, the opening area (throttle area) between the pump port P and the actuator port C1 or C2 is also uniquely determined by the pressure,
As a result, the flow rate to the actuator can be controlled by the command value to the solenoid valve.

However, if the spool 202 moves to the left, for example, fluid flows from the pump port P to the actuator port C1, and the flow rate reduces the pressure acting on the spool 202 near the port C1.
Therefore, the spool 202 receives a force (fluid force) in the direction in which it is pushed back, and the actual movement amount becomes smaller than the command value of the operation signal 250. Since the fluid force changes greatly depending on the flow rate, and the flow rate changes depending on the load of the actuator, even if the command value is constant, the command value and the moving amount of the spool cannot be uniquely determined.

A directional control valve using a solenoid valve is suitable for controlling an actuator, but has a drawback that the actuator cannot be controlled exactly as instructed for the above-mentioned reason.

In order to control the actuators according to the command value, the movement of each actuator is sensed or
What is necessary is just to sense the stroke of the spool of a direction switching valve. However, the sensing of the movement of the actuator is a method that goes beyond the system of the directional control valve, and the system has to be recreated for each applied product such as a hydraulic shovel, a machine tool, a robot, and the like. In addition, the sensing of the stroke of the spool has problems such as a use environment in which the stroke sensor is put into a high-pressure fluid and a change in pressure receiving area when the stroke sensor is attached to the spool end.

Further, in Japanese Utility Model Laid-Open No. 5-22964,
By optimizing the spring constant of the control spring acting on the spool, an attempt is made to minimize the influence of the fluid force.
However, the method of estimating the fluid force that changes in a steady fluid or an unsteady fluid from a calculation unambiguously involves a lot of errors. Can not respond to.

In view of the above problems, it is an object of the present invention to operate a spool in accordance with a command value of an operation signal to accurately control an actuator even when a force other than pilot pressure such as a fluid force or a frictional force is acting on the spool. It is to provide a spool type directional valve system that can perform the operation.

[0017]

(1) In order to achieve the above object, the present invention drives a solenoid valve based on a command value of an operation signal, and controls the solenoid valve to apply pilot pressure acting on both ends of a spool to the solenoid valve. In the spool type directional control valve system for switching the output port of the input fluid and controlling the flow rate of the fluid by displacing the spool by changing the spool, the first measurement in which the pilot pressure measures the oil pressure pushing the spool Means, a second measuring means for measuring an actual driving force acting on the spool, and a hydraulic pressure measured by the first measuring means and an actual driving force measured by the second measuring means. Control means for correcting the command value of the operation signal so that the hydraulic pressure increases as the difference between the hydraulic pressure and the actual driving force increases, and outputting the corrected command value to the solenoid valve. It shall be provided.

As described above, the hydraulic pressure and the actual driving force are measured and obtained, and the command value of the operation signal is corrected so that the hydraulic pressure increases as the difference between the hydraulic pressure and the actual driving force increases. Even if a force other than the pilot pressure, which has conventionally been a major error factor in flow rate control such as fluid force and frictional force, is acting on the spool, if the force increases, the oil pressure increases by the amount corresponding to the force. Since the correction is performed, the spool can be operated according to the command value of the operation signal, and the actuator can be accurately controlled.

(2) In the above (1), preferably,
The first measuring means includes a first sensor for detecting a pilot pressure on a high pressure side among pilot pressures acting on both ends of the spool, and a first operation for converting a pressure detected by the first sensor into the hydraulic pressure. Means, and the second measuring means is provided so as to abut on at least one end of the spool via an elastic body, and has a second sensor for detecting the actual driving force.

By detecting the pilot pressure with the first sensor in this way, the first measuring means can measure the hydraulic pressure by multiplying that pressure by the spool pressure receiving area stored in advance, and the second sensor can actually measure the hydraulic pressure. , The second measuring means can measure the actual driving force.

(3) In the above (2), for example, the first sensor and the second sensor share two pressure sensors arranged so as to abut on both ends of the spool via elastic bodies. The above 2
Among the two pressure sensors, the pressure sensor on the side corresponding to the command signal from the command means is used as a first sensor, and the other pressure sensor is used as a second sensor.

As described above, the two pressure sensors are alternately switched to the first pressure sensor.
When the pressure sensor is used as the first sensor by using the sensor as the second sensor, the hydraulic pressure can be measured as described in the above (2). When the pressure sensor is used as the second sensor, By converting the detected value into a force, the actual driving force can be measured.

(4) Further, in the above (2), the first sensor may be a differential pressure sensor for detecting a differential pressure of pilot pressure acting on both ends of the spool.

By using the differential pressure sensor as the first sensor in this way, one sensor can detect any pilot pressure at both ends of the spool.

(5) In the above (2), the second sensor is a pressure sensor, and the second measuring means converts a value detected by the pressure sensor into a force to convert the actual driving force. You may ask.

Thus, even if the second sensor is a pressure sensor, the second measuring means can measure the actual driving force.

(6) In the above (2), the second sensor may be a load cell.

Thus, the second measuring means can measure the actual driving force directly with the detection force of the load cell.

(7) In the above (1), for example, the control means calculates a feedback correction value for the oil pressure by multiplying a ratio of the oil pressure to an actual driving force by a command value of the operation signal. Then, the command value of the operation signal is corrected by subtracting the feedback correction value from the command value of the operation signal.

Thus, the control means can correct the command value of the operation signal so that the hydraulic pressure increases as the difference between the hydraulic pressure and the actual driving force increases.

(8) In the above (1), the control means calculates a correction value corresponding to a force other than the pilot pressure from a difference between the hydraulic pressure and the actual driving force, and calculates the correction value of the operation signal. The command value of the operation signal may be corrected by adding to the command value.

The control means can also correct the command value of the operation signal so that the hydraulic pressure increases as the difference between the hydraulic pressure and the actual driving force increases.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram showing an entire spool type directional control valve system according to a first embodiment of the present invention.

In FIG. 1, reference numeral 100 denotes a spool-type directional control valve according to the present invention.
, Pump ports P connected to the tank 35, tank ports T1 and T2 connected to the tank 35, and actuator ports C1 and C2 connected to the actuator 102. The spool 2 switches the communication between these ports. The spool 2 is operated by introducing pilot pressure to pressure chambers A and B provided at both ends of the spool. The pressure chambers A and B are formed in flanges 3 and 4 attached to the housing 1.

The spring 7 and the spring seats 5 and 6 for positioning the spool 2 are bolted to the spool 2.
And these parts are housed in the flange 4.

The solenoid valves 30 are provided in the pressure chambers A and B of the spool 2.
The pilot pressure is guided from a and 30b, and the spool 2 moves to the left and right according to the pilot pressure guided to the pressure chambers A and B. When the spool 2 is balanced with the spool positioning spring 7, the position is determined and stopped. At this time, the pump port P
Is connected to either the actuator port C1 or C2, and the pump port P is connected to the actuator port C1.
Alternatively, the flow rate according to the position of the spool 2 flows into C2,
The actuator 102 is driven.

The solenoid valves 30a, 30b are connected to the hoses 31a, 3
They are connected to the flanges 3 and 4 via 1b, respectively, to the pilot pump 33 via the hose 32, and to the tank 35 via the hose 34, respectively. The solenoid valves 30a and 30b operate according to the current value from the controller 60. For example, when it is desired to move the spool 2 to the left, the solenoid valve 30a is opened by outputting only the command current 51a, the pressure in the pressure chamber A increases, and the spool 2 moves.

The above is the same configuration as the conventional spool type directional control valve. In the present invention, a control system as described below is added to such a spool type directional control valve.

First, a force detecting spring 10a is fixed to the right end of the spool 2 so as to move together with the spool 2, and a sensor contact portion having a spherical projection is provided on the free end side (opposite side) of the spring 10a. 10c is fixed. On the left end side of the spool 2, a similar spring 10b is fixedly mounted on a head 8a of a bolt 8 for holding a spool positioning spring 7, and a spherical end is also provided on the free end side (opposite side) of the spring 10b. A sensor contact portion 10d having a projection is fixedly provided. The respective sensor contact portions 1 of the force detecting springs 10a and 10b
0c and 10d are in contact with the pressure sensors 20a and 20b, respectively.
4 attached. For simplicity of explanation, in the present embodiment, the pressure sensors 20a and 20b and the force detecting springs 10a and 10b
Clearance between the sensor contact portions 10c and 10d is 0 m
m.

FIG. 2 shows the structure of the pressure sensors 20a and 20b. In FIG. 2, the pressure sensors 20a and 20b are represented by reference numeral 20.

In FIG. 2, the pressure sensor 20 has housings 200 and 201.
A diaphragm structure 21 for detecting pressure is fixed between the two. A plurality of strain gauges 21a are provided for the diaphragm surface pressure of the diaphragm
The strain gauge 21a detects that the diaphragm surface of the diaphragm structure 21 is distorted by pressure. An amplifier 22 and a strain gauge power supply 23 are arranged in the housing 200, and these are connected to a cable 24.

An oil passage 202 is formed at the tip of the housing 201, and the pressure P is guided from the oil passage 202, detected by the strain gauge 21a as described above, and the signal is amplified by the amplifier 22 and the signals 52a, 52b. Is input to the controller 40 via the cable 24.

The pressure sensor 20 similarly outputs signals 52a and 52b even when a force is applied to the diaphragm surface of the diaphragm structure 21. In the present embodiment, the actual driving force acting on the spool 2 (hereinafter, simply referred to as driving force) is measured using the signals 52a and 52b.

The principle of measuring the driving force of the spool 2 from the signals 52a and 52b of the pressure sensor 20 will be described with reference to FIG.

In FIG. 3, the following relationship exists between the driving force Fm of the spool 2, the force Fp of the spool 2 pressing the flange 4, and the force Fs of the spool 2 pressing the pressure sensor 20.

Fm = Fs + Fp If the spool 2 is displaced by x due to the driving force Fm, then Fm = (kd−10kp) x. Here, kd is the spring constant of the spring 10b (or 10a), and kp is the spring constant of the spool positioning spring 7. Since Fs = kdx, the displacement x can be obtained by x = Fs / kd. That is, Fp is given by the following equation.

Fp = Fs / kd × kp The force that can be detected by the pressure sensor 20 is Fs, and the spring constants kd and kp are known. Therefore, the driving force Fm of the spool 2 is given by the following equation from the above equation.

Fm = Fs + Fs / kd × kp = (1 + kp / kd) × Fs Since the pressure sensor 20 is a sensor for sensing “pressure”, if the value of the signal 52b (or 52a) of the sensor 20 is V20b, A force corresponding to the pressure of Ps = Co × V20b Co: proportional constant is applied to the pressure sensor 20. This pressure sensor 20
Assuming that the pressure receiving area is Ad, the force acting on the pressure sensor 20 is as follows: Fs = Ps × Ad = Co × V20b × Ad.

From the above, the driving force Fm of the spool 2 is obtained as follows: Fm = (1 + kp / kd) × Fs = (1 + kp / kd) × (Co × V20b × Ad)

The controller 40 is provided with the pressure sensor 20
a, 20b and the operation lever angle signal (operation signal) 50 from the command means, perform predetermined arithmetic processing, and issue a command current 51 to the solenoid valves 30a, 30b.
a and 51b are output.

FIG. 4 shows details of the controller 40.

In FIG. 4, the angle signal (operation signal) 50 of the operation lever from the command means, the pressure sensors 20a, 20
Signals 52a and 52b from b are input to the A / D board 47. The A / D board 47 is connected to a ROM 42, a RAM 43, and a CPU 44 via a common bus 41.
ROM 42 based on the signal input from A / D board 47
Calculation processing is performed by the CPU 44 based on the program stored in the program. The command value calculated here is sent from the D / A board 45 to the amplifiers 46a and 46b, and sent to the solenoid valves 30a and 30b as command currents 51a and 51b.

The contents of the arithmetic processing in the CPU 44 will be described with reference to the flowchart of FIG.

In step S1, the processing routine is started.
In step S2, the value θo of the angle signal 50 of the operation lever is read, and in step S3, the command voltage values Voa, Vob for obtaining the command currents 51a, 51b for the proportional solenoids of the solenoid valves 30a, 30b are calculated according to the following equation. Calculate.

Voa = f (θo) Vob = g (θo) Here, the relationship between the operation lever angle θo and the command voltage values Voa and Vob to the proportional solenoid may be either linear or non-linear.

As an operation example, when the operating lever is moved so as to raise the pressure in the pressure chamber A and bring the pressure chamber B to the atmospheric pressure, V
The command voltage value Voa increases with oa = f (θo), and Vob
= G (θo), the command voltage value Vob is calculated to decrease.

Next, in steps S4, the values V20a and V20b of the signals 52a and 52b of the pressure sensors 20a and 20b are read.

In the above operation example, the pressure of the pressure chamber A acts on the pressure sensor 20a disposed in the pressure chamber A, and the spool 2 moves to the right side as shown in FIG. Force detection spring 10a fixed to the right end of 2
Is not in contact with the pressure sensor 20a. For this reason, the pressure in the pressure chamber A is set as the value V20a of the signal 52a by the controller 4.
Read to 0. In the pressure chamber B, the pressure becomes the atmospheric pressure, and since the spring 10b disposed at the left end of the spool 2 is in contact with the pressure sensor 20b, this force is read as the value V20b of the signal 52b.

In the next step S5, the command voltage value Voa is compared with the command voltage value Vob. If the command voltage value is Voa> Vob, the value V20a of the signal 52a of the pressure sensor 20a can be determined as pressure, and the value V20b of the signal 52b of the pressure sensor 20b can be determined as force. Otherwise, the signal 52a of the pressure sensor 20a can be determined.
The value V20a of a can be determined as force, and the value V20b of the signal 52b of the pressure sensor 20b can be determined as pressure.

In the above operation example, the determination here is Yes, and in step S6a, the hydraulic pressure Fa at which the pilot pressure presses the spool 2 is calculated. First, since the pressure in the left pressure chamber B is atmospheric pressure, the hydraulic pressure Fa for moving the spool 2 is
Is caused by the pressure generated in the pressure chamber A. Now, assuming that the pressure in the pressure chamber A is Pa, this pressure Pa and the pressure sensor 20a
Has the relationship of Pa = Co × V20a Co: proportionality constant. The hydraulic pressure Fa for pressing the spool 2 with the pressure receiving area of the spool 2 as As is calculated as Fa = As × Co × V20a. Here, the relationship between the detected value V20b of the pressure sensor 20 and the pressure Ps is linear (proportional constant Co), but this is not essential.

Next, in step S7a, the actual driving force Fm acting on the spool 2 is calculated. Since a force other than the pilot pressure, such as a fluid force or a frictional force, acts on the spool 2, the spool 2 is not actually displaced by the above-mentioned Fa oil pressure. The driving force Fm of the spool 2 is obtained by subtracting a force other than the pilot pressure such as a fluid force or a friction force from the hydraulic pressure Fa, and the driving force Fm is detected by a pressure sensor 20b provided in the pressure chamber B. The driving force Fm is, as described above, Fm = (1 + kp / kd) × Fs = (1 + kp / kd) × (Co × V20b × Ad) Ad: Pressure receiving area of pressure sensor 20a or 20b kp: Spool positioning spring The spring constant of 7 kd: The spring constant of the force detecting spring 10a or 10b.

As described above, the hydraulic pressure Fa due to the pilot pressure acting on the spool 2 and the actual driving force Fm are obtained.

Next, in step S8a, the actual driving force Fm is converted into the feedback voltage Vr. Hydraulic pressure Fa obtained earlier
Is the force when the output voltage value to the solenoid valve is Voa.
The voltage Vr corresponding to m is as follows: Vr = VoaFm / Fa

If Voa is larger than Vob, the Voa side is the control object, and a feedback correction calculation for Voa is performed in step S10a using the feedback voltage Vr as a correction value. That is, V30a = h (Voa-Vr) V30b = Vob and correction command values V30a and V30b for the solenoid valves 30a and 30b are calculated, and the output value on the Voa side is corrected. Here, the function h may have a proportional, integral, or differential element, or may not.

These command values V30a and V30b are output as signals 51a and 51b to the solenoid valves 30a and 30b in step S11, and the procedure returns to step S2. In this loop, the solenoid valve 30a is controlled so that the hydraulic pressure Fa acting on the spool and the driving force Fm match.
Pilot pressure (pressure in pressure chamber A) Pa
Is adjusted.

If No in step S5, that is, if Voa ≦ Vob, the processes in steps S6b and S7b are executed. in this case,
The calculation of the force by the pilot pressure Pb acting on the spool 2 uses the signal 52b of the pressure sensor 20b, and the calculation of the actual driving force acting on the spool 2 uses the pressure sensor 20a.
Will be used. The correction value is determined in step S8.
In b, Vr = VobFm / Fa. Further, in the calculation of the correction command values V30a and V30b for the solenoid valves 30a and 30b, the procedure S10b is executed, and Vob
, A feedback correction operation is performed.

In the above, the pressure sensors 20a, 20b
And steps S4, S6a, S6b of the controller 40 shown in FIG.
The function of is that the pilot pressure is
a first measuring means for measuring a, and a force detecting spring 10
a, 10b, the pressure sensors 20a, 20b, and the functions of the steps S4, S7a, S7b shown in FIG. 5 of the controller 40 are used to measure the actual driving force Fm acting on the spool 2.
The procedure shown in FIG.
The functions of S2, S3, S5, S8a, S8b, S10a, S10b, and S11 are based on the hydraulic pressure Fa measured by the first measuring means and the actual driving force Fm measured by the second measuring means. The command values Voa and Vob of the operation signal 50 are corrected so that the oil pressure increases as the difference between the pressure and the actual driving force increases, and the corrected command values V30a and V30b are used as the solenoid valves 30a and 30b.
The control means for outputting to 30b is constituted.

FIG. 7 shows the displacement characteristics of the spool 2 by the control system configured as described above, and FIG. 8 shows the flow characteristics due to the displacement of the spool 2. These characteristic diagrams are the results of performing a simulation including the fluid force on the solenoid valves 30a and 30b, the hose, and the direction switching valve 100 shown in FIG. 1, and performing a simulation. The fluid force uses the theoretical value of the literature.

FIG. 7A shows a case where the control shown in FIG. 5 of the present invention is performed when there is a fluid force. In the spool displacement diagram of FIG. 7, the spool 2 strokes to about 6.5 mm. You can see that it is. Further, in the flow characteristic diagram of FIG. 8, a flow rate of about 190 liter / min is obtained.
(B) is a case where control is not performed when there is a fluid force, and the spool 2 is pushed back to 5.2 mm by the fluid force, and the flow rate is reduced to 105 liter / min, which is as much as 45%. (C) shows the spool displacement and flow rate characteristics when there is no fluid force, and it can be seen that the fluid force can be almost canceled by performing the control of the present invention.

Therefore, according to this embodiment, the pressure sensors 20a, 20b, the force detecting springs 10a, 10b, and the sensor contact portions 10c, 10d are added to the pilot pressure chambers A, B of the conventional spool type directional control valve. With a simple configuration, even if a force other than the pilot pressure, which has conventionally been a major error factor in controlling the flow rate, such as a fluid force or a frictional force, acts on the spool 2, the spool 2 is moved in accordance with the command value of the operation signal. The actuator 102 can be operated and accurately controlled.

FIG. 9 shows a modification of the first embodiment shown in FIG. FIG. 9 corresponds to the flowchart shown in FIG. 5 of the first embodiment. The steps up to steps S7a and S7b are the same as those in FIG. Therefore, description of steps S1 to S7b will be omitted, and description will be made from step S8A.

In step S8A, a force Ff other than the pilot pressure such as a fluid force or a friction force (hereinafter, represented by a fluid force) is calculated. The fluid force Ff becomes Ff = Fa-Fm, and can be controlled using this Ff. That is, since the pressure (force) generated in the spool 2 by the command voltage value of Voa or Vob is reduced by the fluid force, the voltage of this fluid force may be further added to the command value Voa or Vob.

In step S8B, the electromagnetic valve 30a or 3 corresponding to the detected fluid force is obtained by Vf = Ff × Cp.
The correction command voltage Vf to 0b is calculated. Here, Cp is a correction coefficient for converting a force into a voltage.

In step S9, the two solenoid valves 30a and 30b
The magnitude of the command values Voa and Vob with respect to is determined, and the solenoid valve for which the feedback correction is performed is specified.
In steps a and S10Ab, the correction command values V30a and V30b for the solenoid valve 30a or 30b are calculated using the correction command voltage Vf as a correction value. In this case, for example, in step S10Aa, V30a = h (Voa + Vf) V30b = Vob

The command values V30a and V30b are output as signals 51a and 51b to the solenoid valves 30a and 30b in step S11, and the procedure returns to step S2.

In the above, the pressure sensors 20a, 20b
And steps S4, S6a, S6b of the controller 40 shown in FIG.
The function of is that the pilot pressure is
a first measuring means for measuring a, and a force detecting spring 10
The functions of steps S4, S7a, and S7b of the pressure sensors 20a and 10b, the pressure sensors 20a and 20b, and the controller 40 shown in FIG.
The configuration of the measuring means is the same as that of the first embodiment. Then, steps S2 and S2 shown in FIG.
The functions of S5, S8A, S8B, S9, S10Aa, S10Ab and S11 are based on the oil pressure Fa measured by the first measuring means and the actual driving force Fm measured by the second measuring means. The command values Voa and Vob of the operation signal 50 are set such that the hydraulic pressure increases as the difference between the pressure Fa and the actual driving force Fm increases.
And the corrected command values V30a and V30b are
Control means for outputting to 0a and 30b is constituted.

According to this embodiment, the same effects as those of the first embodiment can be obtained.

In the above-described embodiment, the force detecting springs 10a and 10b, which are elastic members, are fixed to the spool 2, but these elastic members are used to generate a force corresponding to the amount of movement of the spool 2. And the force detecting springs 10a, 1
0b may be fixed to the pressure sensor 20a, 20b side, or both ends may be fixed to the spool 2 and the pressure sensor 20a, 20b.

FIGS. 10 and 1 show a second embodiment of the present invention.
1 will be described. In the figure, the same reference numerals are given to the same components as those shown in FIGS. This embodiment further simplifies signal processing.

In FIG. 10, reference numeral 100A denotes a spool type directional control valve according to the present invention. Flanges 9 and 4 are attached to a housing 1 of the spool type directional control valve 100A. , C, and a pressure chamber B is formed in the flange 4.

In the pressure chamber B, a force detecting spring 11 is fixed to the end 8a of the spool positioning bolt 8, and a uniaxial load cell 22 is fixed on the extension thereof.
The natural length of the force detecting spring 11 may be adjusted to the length of the positioning bolt 8 and the load cell 22 when the spool 2 is in the neutral position, or a spring force is generated when the spool 2 is moved to the right end with an offset. Thus, the natural length may be larger than the maximum stroke. In the present embodiment, the force detection spring 11
It is assumed that the force detecting spring 11 is compressed and exerts a force on the load cell 22 even when the spool 2 moves to the right end.

The pressure in the pressure chamber B on the left side of the spool is introduced into the pressure chamber C in the flange 9, and a differential pressure sensor 21 is attached to the flange 9. The differential pressure of is detected. When the differential pressure is positive, the spool 2 moves from right to left, and when negative, the reverse is true.

The contents of the arithmetic processing in the controller 40A will be described with reference to the flowchart of FIG.

First, a processing routine is started in step S1. At this time, the pressure applied to both ends of the spool 2 is atmospheric pressure, and the spool 2 is in the neutral position. In order to detect the spring force of the force detecting spring 11 at this time, the value Fm0 of the signal 54 of the load cell 22 is read in step S2A.

Next, in steps S2 and S3, as in the flowchart of FIG. 5, the value θo of the angle signal 50 of the operation lever is read, and the command voltage values Voa and Vob for the proportional solenoids of the solenoid valves 30a and 30b are calculated.

Next, in step S4A, the signal 53 of the differential pressure sensor 21
Is read. In the first loop, no pressure acts on the pressure chambers A and C, but from the second loop, pressure is generated in one of the pressure chambers. Hereinafter, the state after the pressure chambers A and C are acted upon and the spool 2 starts to move will be described.

In step S6A, the signal value V of the differential pressure sensor 21
From step 21, the hydraulic pressure Fa due to the pilot pressure acting on the spool 2 is calculated as Fa = As × Pa = As × Co × V21 in the same manner as in steps S6a and S6b in FIG. Here, in this example, when the pressure is generated in the pressure chamber A and the solenoid valve 30a is operated so that the pressure chamber C becomes the atmospheric pressure, the differential pressure is set so that the signal value V21 of the differential pressure sensor 21 becomes positive. It is assumed that the sensor 21 is installed.

Next, in step S7A, the load cell 2 at this time is
The value Fm1 of the second signal 54 is read. The force Fm1 acting on the load cell 22 is transmitted by the spring 11,
Is in the neutral position, the spring 11 is under compression, so that the load cell 22 is subjected to the force Fm0. The force Fs generated by the movement of the spool 2 is a difference between the force Fm0 and the force Fm1 after the spool is moved when the spool 2 is at the neutral position, and is obtained by Fs = Fm1−Fm0. With this Fs, the actual driving force Fm of the spool 2 can be calculated as Fm = (1 + kp / kd) × (Fm1−Fm0) as in step S7B, similarly to steps S7a and S7b in FIG.

In step S9, the two solenoid valves 30a and 30b
Then, the magnitudes of the command values Voa and Vob are determined to identify the solenoid valve to be controlled.

Steps S8a and S8b and thereafter are the same as those in FIG. 5 described above, and will not be described.

In the above, the functions of the steps S4A and S6A of the differential pressure sensor 21 and the controller 40A shown in FIG.
Step S2 shown in FIG. 11 of the force detecting spring 11, the load cell 22, and the controller 40A constitutes first measuring means for measuring the oil pressure Fa at which the pilot pressure presses the spool 2.
The functions of A, S7A and S7B constitute second measuring means for measuring the actual driving force Fm acting on the spool 2, and the procedures S2, S3, S8a and S8 of the controller 40A shown in FIG.
The functions of b, S9, S10a, S10b, and S11 are based on the hydraulic pressure Fa and the actual driving force based on the hydraulic pressure Fa measured by the first measuring means and the actual driving force Fm measured by the second measuring means. A control means for correcting the command values Voa and Vob of the operation signal 50 so that the hydraulic pressure increases as the difference from the force Fm increases, and outputting the corrected command values V30a and V30b to the solenoid valves 30a and 30b. I do.

In this embodiment constructed as described above, the pressure chamber C, the differential pressure sensor 21, the load cell 22 and the spring 11 are simply added to the pilot pressure chambers A and B of the conventional spool type directional control valve. Even if a force other than the pilot pressure, which has conventionally been a major error factor in controlling the flow rate, such as a fluid force or a frictional force, is acting on the spool 2, the spool 2 can be operated according to the command value of the operation signal. Can control the actuator 102.

In the embodiment shown in FIG. 10, the force acting on the spool 2 and the driving force of the spool 2 are read, and the position of the spool 2 is controlled based on the read force. The spring 11 for the spool is used in place of the spring 7 for positioning the spool, and the bolt 8 is directly connected to the load sensor 2.
You may hit 2. Further, it has an elastic body (spring 11) and a sensor for detecting the force of the spool 2, and has a sensor capable of measuring the differential pressure between the left and right pressure chambers A and B. Based on these signals, the electromagnetic valve 30a , 30b can be used as long as they can be controlled.

If a load cell is used, a pressure sensor may be arranged as shown in the embodiment of FIG. 1 instead of the differential pressure sensor, and this pressure sensor may be used exclusively for detecting the pilot pressure. In this case, the mounting position of the pressure sensor may be a position immediately after the solenoid valve.

[0096]

According to the present invention, the conventional spool type directional control valve has a simple structure in which a pilot pressure chamber, a load cell and an elastic body are simply added to the pilot pressure chamber. Even if a force other than the pilot pressure, which has been a major error factor in the control, is acting on the spool, the spool can be operated according to the command value of the operation signal to accurately control the actuator.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a spool type directional switching valve system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a detailed structure of a pressure sensor.

FIG. 3 is a diagram illustrating the principle of measuring force with a pressure sensor.

FIG. 4 is a diagram schematically showing a processing function of a controller.

FIG. 5 is a flowchart illustrating processing performed by a controller.

FIG. 6 is a diagram showing an operation state of the direction switching valve.

FIG. 7 is a view showing displacement characteristics of a spool by the directional control valve system of the present invention.

FIG. 8 is a diagram showing a flow rate characteristic due to displacement of a spool of the directional control valve system of the present invention.

FIG. 9 is a flowchart showing a modification of the processing content of the first embodiment shown in FIG. 5;

FIG. 10 is a diagram showing an overall configuration of a spool type directional control valve system according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing processing contents of a controller.

FIG. 12 is a diagram showing an overall configuration of a conventional spool type directional control valve system.

FIG. 13 is a diagram schematically showing the processing functions of a controller in a conventional spool type directional control valve system.

[Explanation of symbols]

 Reference Signs List 1 housing 2 spool 3, 4 flange 7 spool positioning spring 8 bolt 9 flange 10a, 10b force detection spring 10c, 10c sensor contact part 11 force detection spring 20a, 20b pressure sensor 30a, 30b solenoid valve 31a, 31b, 32 , 34 Hose 33 Pilot pump 35 Tank 40, 40A Controller 50 Operation signal 51a, 51b Command current 52a, 52b Signal 54 Signal 100, 100A Direction switching valve 101 Hydraulic pump 102 Actuator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Morio Oshina 650, Kandamachi, Tsuchiura-shi, Ibaraki Pref.

Claims (8)

[Claims] An electromagnetic valve is driven based on a command value of an operation signal, a pilot pressure acting on both ends of a spool is changed by the electromagnetic valve, and the spool is displaced.
In a spool type directional control valve system for switching an output port of an input fluid and controlling a flow rate of a fluid, a first measuring means for measuring an oil pressure by which the pilot pressure presses the spool; A second measuring means for measuring the driving force of the motor, and a difference between the hydraulic pressure and the actual driving force based on the hydraulic pressure measured by the first measuring means and the actual driving force measured by the second measuring means. And a control means for correcting the command value of the operation signal so that the hydraulic pressure increases as the pressure increases, and outputting the corrected command value to the solenoid valve. 2. The spool type directional control valve system according to claim 1, wherein the first measuring means detects a pilot pressure on a high pressure side among pilot pressures acting on both ends of the spool; First calculating means for converting the pressure detected by the first sensor into the hydraulic pressure, wherein the second measuring means is arranged to abut at least one end of the spool via an elastic body. And a second sensor for detecting the actual driving force. 3. The spool-type directional control valve system according to claim 2, wherein said first sensor and said second sensor are two pressure sensors arranged so as to abut on both ends of said spool via elastic bodies, respectively. As a common sensor, using a pressure sensor of the two pressure sensors corresponding to a command signal from the command means as a first sensor, and using the other pressure sensor as a second sensor. Characteristic spool type directional valve system. 4. The spool type directional control valve system according to claim 2, wherein said first sensor is a differential pressure sensor for detecting a differential pressure of a pilot pressure acting on both ends of said spool. Type directional valve system. 5. The spool-type directional control valve system according to claim 2, wherein the second sensor is a pressure sensor, and the second measuring means converts a value detected by the pressure sensor into a force to perform the actual operation. A spool-type directional control valve system for determining the driving force of the spool. 6. The spool type directional control valve system according to claim 2, wherein said second sensor is a load cell. 7. The spool type directional control valve system according to claim 1, wherein the control means multiplies a ratio between the hydraulic pressure and an actual driving force by a command value of the operation signal to provide a feedback correction value for the hydraulic pressure. Wherein the feedback correction value is subtracted from the command value of the operation signal to correct the command value of the operation signal. 8. The spool type directional control valve system according to claim 1, wherein the control means calculates a correction value corresponding to a force other than the pilot pressure from a deviation between the hydraulic pressure and an actual driving force, and calculates the correction value. A spool-type directional control valve system for correcting a command value of the operation signal by adding a value to the command value of the operation signal.