JPH03237301A - Position detector for liquid pressure cylinder - Google Patents

Abstract

PURPOSE:To obtain the position of this cylinder continuously with high resolution by varying the magnetic resistance of a coil part on the side of a cylinder main body continuously through one cycle and detecting the position of a rod continuously within a range of one cycle correspondingly. CONSTITUTION:Primary coils A1 - D1 and secondary coils A2 - D2 are provided individually for respective groups A - D. A magnetic circuit varies in reactance among respective phases A - D according to th linear displacement of a magnetic ring rod 2 and deviates by 90 deg., phase by phase. The primary coils of the phases A and C excited in mutually opposite-phase relation with a sine wave signal sinomegat and the outputs of secondary coils A2 and C2 are added in in-phase relation. The phases B and D are the same. When the output signal Y of a detection part 20 is Ksin(omegat+phi) and K is a constant, a phase shift phicorresponding to a reference signal sinomegat is measured to detect the position of the rod 21. The absolute linear position within a range of a distance P can be detected with the electric phase shift value phi of the signal Y.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a '3A position for detecting the piston rod position of a pneumatic or other fluid pressure cylinder, and particularly relates to a system capable of absolute position detection.

[Conventional technology]

Conventionally, the operation of six-atmosphere cylinders and other fluid FF cylinders was limited to full stroke motion, but recently, cylinders with brakes have been used to stop the cylinders at arbitrary mid-stroke positions. An example of such conventional technology is shown in FIGS. 1 and 2. A cylinder 1 is provided with a brake 2, and a brake cylinder 4 is actuated by switching a brake solenoid valve 3, whereby a piston rod It is designed to apply the brakes to 5. 6 is a direction control valve for switching the rod driving direction of the cylinder 1; 7 is an air source; 8;
9 is a throttle valve for controlling drive speed. The detection unit 10 for detecting the stroke position of the cylinder is configured to detect a roller Oa which is in constant contact with the rod 5 and rotates following the linear motion of the rod 5, and an incremental pulse in response to the rotation of the roller 10a. It includes an incremental encoder 10b (FIG. 2) that generates .

When the cylinder rod 5 is in the home position, a counter 12 is reset by the home setting switch 11, and thereafter the counter 12 counts incremental pulses given from the encoder 10b.

The count value of the counter 12 indicates the cylinder rod position, and a comparison circuit 14 compares the set position of each actuator operation set by the setting device 13 with this count value. The comparison operation of the comparison circuit 14 and the operation of the drive circuit 16 are controlled by the sequence circuit 15. The output of the comparison circuit 14 is given to the drive circuit 16, and a drive signal for switching the direction control valve 6 and the brake valve 3 is given to the valves 3 and 6 according to the comparison result. The position is set using the setting device 13, and when the current position of the rod 5 measured using the detection unit 10 matches this set position, the brake valve 3 is switched to operate the brake 2,
At the same time, the direction control valve 7 is switched to the neutral position and the rod 5 is stopped.The cylinder piston rod position detection device shown in U.S. Pat. A pulse train responsive to the uneven portion is obtained by a pickup coil in accordance with the linear displacement of the piston rod.

The cylinder position detection device disclosed in JP-A-50-13754 uses primary and secondary coils installed at predetermined positions within the cylinder body instead of a limit switch that mechanically detects contact with a piston rod, etc. The piston is placed in the specified position without contact using the 11! A pair of electromagnetically coupled primary and secondary coils is installed in the cylinder, and a high magnetic permeability member that moves in accordance with the movement of the piston rod connects the primary and secondary coils. Depending on whether or not the piston enters the electromagnetic coupling area of
I.

[This is to detect whether the (stroke end) has been reached.

[Problem to be solved by the invention]

The conventional piston rod position detection device shown in FIG. 1 uses an incremental pulse counting method to detect the position of the piston rod, so there is a problem with the accuracy of position detection. If a blockage occurs, there are problems such as having to return the cylinder to point i. In addition, since displacement is transmitted to the rod-attached detection section 10 by friction between the roller 10a and the rod 5, if slipping occurs.

There was a drawback that position detection was inaccurate.

Further, the cylinder position detecting device disclosed in Japanese Patent Application Laid-Open No. 13754/1980 was only able to detect the end of the stroke, and was unable to continuously detect the piston rod position.

On the other hand, in the method shown in the above-mentioned US patent, the piston rod position can be continuously detected by counting the pulse train obtained by the pickup coil, but it is possible to continuously detect the piston rod position by counting the pulse train obtained by the pickup coil. Since the detection resolution is very low, the detection resolution is extremely coarse. Also,
Same as above.

Since it is an incremental pulse count, when turning on the power or recovering from a power failure, the piston position is -11, initial Q h'
There was the inconvenience of having to go back to ffi.

This invention has been made in view of the above points, and aims to provide a detection device for a fluid bed cylinder that can continuously and absolutely detect the piston rod position with high resolution. It is something.

[Means for solving problem a]

A position detection device for a fluid pressure cylinder according to the present invention has at least a primary coil excited by a predetermined alternating current signal, and is fixed to a cylinder body side of a fluid pressure cylinder, and is arranged relative to a piston rod of the cylinder. a magnetic body consisting of a repeating magnetic part and non-magnetic part provided on the rod in order to change the magnetic resistance in the magnetic circuit of the coil part according to the position of the rod; comprising a scale part and a detection circuit that extracts data indicating the position of the rod from the coil part based on a change in magnetic resistance in the coil part according to the relative stiffness of the magnetic scale part 61i with respect to the coil part, The position of the rod can be continuously detected in accordance with continuous changes in magnetic resistance in the coil portion within the range of one cycle of repetition of the magnetic material portion and the non-magnetic material portion in the magnetic scale portion.

Further, the detection is possible over a plurality of cycles of repeating the magnetic body portion and the non-magnetic body portion.

In one embodiment, the coil section has a plurality of primary coils and a plurality of secondary coils, and the detection circuit has one
A circuit that individually excites each of the construction method coils using a plurality of phase-shifted reference AC signals, and a circuit that excites the respective construction method coils individually, and adds up the outputs of the secondary coils corresponding to each of the primary coils to generate the reference according to the relative linear position of the rod. an output circuit that generates an output signal that is a phase-shifted AC signal, detects a phase difference between a predetermined one of the reference AC signals and the output signal from the output circuit, and converts the detected rI''l phase difference data to the rod position. It has a circuit that outputs it as data.

In a further embodiment, the primary coil is configured to have an i! of the rod. ! At least two primaries arranged at a predetermined distance from each other with respect to the linear displacement direction and individually excited by a reference AC signal having a predetermined phase difference (,60/d degree) other than 180° or 360°. It consists of a coil, and when the pitch of 1 repeated cycle of the magnetic material part and the non-magnetic material part in the magnetic scale part is P, the separation distance of each of the primary coils is PX (n±(1/d ))(
However, n is an arbitrary integer).For example, if two types of reference AC signals, a sine wave signal and a cosine wave signal, are used, the phase difference between them is 9.
0°=360/4 degrees, and the separation distance between each primary coil is set to P×{n±(1/4)).

To show the correspondence with the embodiment described later, what corresponds to the coil part is a part formed by housing the primary coils A1 to D1 and the secondary coils A2 to D2 in the casing 22, and corresponds to the magnetic scale part. These are the magnetic rings 21b and non-magnetic spacers 21c that are alternately and repeatedly provided around the two piston rods, and the parts that correspond to the detection circuit are the circuit parts that excite the primary coils A1 to D1 and the secondary coil. A2
- A circuit section that adds up the outputs of D2 and extracts the output, and a section of the conversion circuit 23 that measures the phase shift.

[For production]

The piston rod is provided with a magnetic scale section consisting of a repeating magnetic material section and non-magnetic material section, and the relative positional relationship of the coil section with respect to the magnetic scale section changes depending on the position of the piston rod. The magnetic resistance in the magnetic circuit of the coil changes in accordance with the change in the relative positional relationship of the coil with respect to the magnetic scale. Based on this change in magnetic resistance, the detection circuit sends data indicating the rod position from the coil. It can be taken out.

When the rod position changes within the range of one repeated cycle of the magnetic material part and the non-magnetic material part in the magnetic scale part, the magnetic resistance in the coil part changes continuously over one cycle, and the rod position changes accordingly. It can be detected continuously over a range of cycles. This attached detection data is given as absolute data within the range of one cycle. Further, since the magnetic body portion and the non-magnetic body portion are repeatedly provided in the magnetic eye sensing portion, the rod position can be detected over a wide range over a plurality of repeated cycles.

Therefore, according to the present invention, the piston rod error can be detected continuously and absolutely with high resolution.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 3, symbols i-4, 6-9 are the same as those shown in FIG. 1.

In FIG. 3, the detection unit 20 for detecting the relative linear placement of the piston rod 21 with respect to the cylinder 1 is a variable magnetic resistance type position detector that detects the position of the rod in a non-contact manner. This detection unit 20 houses four primary coils A1 to D1 arranged in a predetermined arrangement shifted in the axial direction and secondary coils A2 to D2 provided correspondingly to the four primary coils A1 to D1, which are housed in a casing 22. The cylindrical space of the coil is connected to the rod 2 at the end of the cylinder 1.
The rod 21 is fixed in a state where it passes through the slide 7E between the coil chambers so as to be concentric with the coil chamber 1. The rod 21 includes a cylindrical mandrel 21a to which a piston 21c in the cylinder 1 is attached at one end, and this mandrel 21. a plurality of annular magnetic rings 21b and annular nonmagnetic spacers 21c of a predetermined width that are alternately fitted in the axial direction around a, and a sleeve made of a cylindrical nonmagnetic material that is fitted on the outermost circumference of these rings 21b and annular nonmagnetic spacers 21c; 21d. The non-magnetic spacer 21c is a solid non-magnetic material or air. - For example, P is an arbitrary number), and the same applies to the spacers 21c, and the interval of one pitch in the alternate arrangement is rPJ. In this embodiment, the coils are arranged to operate in four phases. 9 of these phases! Gijo A, B, C, p
7; Use the following symbols to differentiate.

Each phase A- according to the position of the magnetic ring 21b of the rod 21
The reluctance generated in D is shifted by 90 degrees. For example, if the human face is a cosine phase, the B phase is a sine phase, the C phase is a minus cosine phase, and the D phase is a minus sine phase. There is. In the example of Shinobu 3 diagram,
Individual coils A1 to D1 and secondary coils A2 to D2 are provided for each phase A to D. In the example shown in Figure 3, the human-phase coils A 1 and -A 2 and the C-phase coils CI and C2 are provided adjacent to each other, and the B-phase coils B1, . B2 and D phase coil DI, L)2
They are also set up in tandem. Also, A phase and B phase or C
The interval between the phase and υ phase coils is rP(n!1)J (n is an arbitrary random number). With this configuration, the reluctance of the magnetic circuit in each phase A-D changes according to the direct a displacement of the rod 21 (more specifically, the magnetic ring), and the phase of the reluctance change shifts by 90 degrees for each phase (therefore, There is a 180 degree shift between the human face and C phase, and 18 degrees between B phase and D phase.
0M shift). For example, physiognomy and C phase 1
The secondary coils A1 and C1 are excited in opposite phases to each other by a sine signal sinωt, and the outputs of the secondary coils A2 and C2 are added in phase. Similarly to the above, for the B phase and D phase, the primary coils B1 and DI are excited in opposite phases with the cosine signal COSωt, and the two missing coils B2. The outputs of D2 are added in phase. The outputs of the secondary coils are finally summed to obtain the output color code Y. on the other hand,
The present invention is not limited to this, and the human-phase and C-phase primary coils AI and (l are excited in the same phase by a sine signal sinωt, the secondary coils A2 and C2 are connected in opposite phases, and the B-phase and D-phase primary coils Bl
, DI is excited in the same phase by all 5XM e03ωt,
Secondary coil B2. It is also possible to connect D2 in reverse phase and finally add the secondary coil output.

Each output Y of the detection unit 20 is determined by the reference AC signal (ainωt or cosωt
) with a phase shift.

The reason for this is that the reluctances of each phase A-D are shifted by 90 degrees, and one pair (A, C) and the other pair (B, D
) is out of phase with the excitation signal by 90 degrees.

Y=K sin (ωt + +Is) K is a constant determined according to the conditions of the glaze. The position of the rod 21 can be detected by measuring the phase shift φ corresponding to the reference signal sinωtr of the output gY expressed by the above equation.

When the phase shift piece φ is 2π for all the pieces, the displacement step of the rod 21 corresponds to one pitch length P of the magnetic ring 21b. In other words, times 4! fYll! According to the four phase shift values φ in :, it is possible to detect the absolute iLQ position I device within the range of distance P. If you want to find the absolute direct spring position beyond the distance P8, you can use any appropriate means (this detection accuracy may be rough with distance P in units of 1) and place the rod 21]. individual magnetic rings 2
1b, and use a combination of this absolute address of each ring 21b and the above-mentioned direct/direct position detection f-direction based on the phase shift rLφ.

In the fourth factor, the output 4N Y of the detection section 20 is applied to the conversion circuit 261, and the above-mentioned four-dimensional phase shift amount φ is measured. This measured value is output as data DX indicating the current position of the rod 21 (cylinder stroke position).

In order to detect the moving speed and acceleration angle of the rod 21, a speed detection amount @24 and an acceleration detection circuit 25 are provided. In this embodiment, a dedicated sensor for detecting speed and acceleration is provided, rod position detection data Dx is used to detect the continuous movement, and detected speed data Dv is used to detect acceleration. ing. For this purpose, the position data Dx is input to the speed detection circuit 24, and the speed data Dv output from the speed 7f detection circuit 24 is input to the acceleration detection circuit 25.

When the rod 21+ is stationary at an arbitrary position, the position data Dx maintains the value indicating that position and does not change. When the rod 21 is moving at the same speed, the value of the position data Dx changes over time in accordance with changes in the rod position. Therefore, the speed data Dv is determined by calculating the change in position data per predetermined unit time (or period) in the speed detection circuit 24. Furthermore, acceleration data Dα is obtained by calculating the change in velocity data Dv per predetermined unit time (or period) using ε in the acceleration detection circuit 25.

The overrun ROM (or RAM) 26 stores in advance overrun amounts corresponding to various speed values. Similarly, the overrun ROM (or RAM) 27 stores in advance overrun amounts corresponding to various acceleration values. Here, the overrun amount is the brake 2
This is the distance FM from the starting position to the position where the rod 21 actually stops (this overrun amount is measured and learned in advance in response to various speeds and accelerations), and this is determined by RO.
Memorize 26,271 M (or RAM).

R according to the current speed data and acceleration data DcL
The overrun data 0VR1 and 0VR2 read from the OM26 and OM27 are applied to the overrun scene calculation circuit 28. The overrun amount calculation circuit I@28 calculates the predicted overrun amount data OR1 according to the current speed, the predicted overrun data OR2 according to the current acceleration, and the movement setting value (target value) Sx set by the setting device 29. Data OVR, which predicts the actual amount of overrun as a parameter, is obtained through arithmetic operations including calculation, selection, warming, and the like.

The compensation calculation circuit 60 increases or decreases the value of the position data Dx according to the overrun lid prediction data QVRIc,
A value Dx that compensates for the predicted overrun.

Change to The comparison circuit 61 has an overrun compensated I
The SI position data Dxo is compared with the #movement setting value Sx set by the setting device 29, that is, the stop setting position.

This comparison timing, comparison conditions, etc. are controlled by the sequence circuit 32 according to the overall sequence operation of the cylinder 1. The output of the comparison circuit 61 is sent to the drive circuit 3
3, and depending on the comparison result, the directional control valve 6. The brake valve 3 is driven to switch.

〔Effect of the invention〕

As described above, according to the present invention, the piston rod is provided with a magnetic [I horizontal part that is made up of repetitions of a magnetic part and a non-magnetic part. When the position changes, the magnetic resistance in the coil section provided on the cylinder body side changes continuously over one cycle, so that the position of the rod can be continuously detected within the range of one cycle. Therefore, this abduction ID detection data is treated as -ti- as absolute data within the range of the l cycle.
In addition, it is possible to detect the piston rod position in a wide range over multiple repeated cycles of magnetic and non-magnetic parts, and therefore it is possible to continuously and absolutely detect the piston rod position with high resolution. It has an excellent effect.

[Brief explanation of drawings]

Fig. 1 is a side sectional view, fluid I'F, and circuit diagram of a conventional pneumatic cylinder with a brake, and Fig. 2 is an electrical block diagram showing a conventional example of a control system for position determination of the pneumatic cylinder with a brake shown in Fig. 1. 3 is a side sectional view and a fluid pressure circuit diagram of an air cylinder with a brake according to an embodiment of the present invention, and FIG. 4 is an electrical block diagram showing an example of a positioning control system in the embodiment. It is. 1... Cylinder, 2... Brake, 3... Brake valve, 4... Brake cylinder, 5.21... Piston rod, 6... Direction control valve, 7... Air source ,
8, 9... Throttle valve, 20... Position detection section, 21a.
...Rod stem, 21b...Magnetic ring, 21c.
...Non-magnetic spacer, 21cl...Non-magnetic sleeve,
21e...Piston, A1-D1...Primary coil,
A2 to D2... Secondary coil 22... Casing of the coil section, 23... Conversion circuit.

Claims (1)

[Claims] 1. A coil that has at least a primary coil excited by a predetermined alternating current signal, is fixed to the cylinder body side of a fluid pressure cylinder, and is movable relative to the piston rod of the cylinder. a magnetic scale section formed by repeating a magnetic section and a non-magnetic section provided on the rod in order to change the magnetic resistance in the magnetic circuit of the coil section according to the position of the rod; a detection circuit that extracts data indicating the position of the rod from the coil section based on a change in magnetic resistance in the coil section according to a relative position of the scale section with respect to the coil section; The position of the rod can be continuously detected according to continuous changes in the magnetic resistance in the coil part within the range of one repeated cycle of the magnetic part and the non-magnetic part, and A position detection device for a fluid pressure cylinder, characterized in that the detection is possible over a plurality of repeated cycles. 2. The coil section includes a plurality of primary coils and a secondary coil, and the detection circuit includes a circuit that individually excites each of the primary coils using a plurality of phase-shifted reference AC signals; an output circuit for summing outputs of secondary coils corresponding to each primary coil to generate an output signal that is phase-shifted from the reference AC signal according to the relative linear position of the rod; The fluid pressure cylinder according to claim 1, further comprising a circuit for detecting a phase difference between the output signal and the output signal from the output circuit, and outputting the detected phase difference data as the rod position data. Position detection device. 3. The primary coils are arranged apart from each other by a predetermined distance with respect to the linear displacement direction of the rod, and are arranged at a distance of 180°.
Alternatively, it consists of at least two primary coils that are individually excited by a reference AC signal having a predetermined phase difference (360/d degrees) other than 360°, and is non-contact with the magnetic body part in the magnetic scale part. When the pitch of one repeated cycle of the magnetic body portion is P, the separation distance between each of the primary coils is set to P×{n±(1/d)} (where n is an arbitrary integer). A position detection device for a fluid pressure cylinder according to claim 2.