JPH0226003Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a device for detecting the linear position of a cylinder rod.

Although various cylinder position detection devices have been considered in the past, there are only a few that can continuously detect the position of movement, and none of them have been able to detect the position in an absolute manner. The purpose of this invention is to provide a device that can continuously and absolutely detect the position of a cylinder.
The purpose is to construct a stator assembly including a stator in which a plurality of magnetic poles formed by winding a primary coil and a secondary coil are arranged at predetermined intervals in the circumferential direction, so that the center space of the stator is approximately concentric with the rod of the cylinder. The rod is slidably penetrated through the central space and fixed at a predetermined location of the cylinder, and the rod is made of a magnetic material,
A plurality of protrusions arranged at a predetermined pitch in the axial direction are provided at least on the surface facing the stator magnetic poles around the rod, and between each of the stator magnetic poles, there is a misalignment in the correspondence between the protruding portions of the rods and the magnetic pole grooves. The primary coils of each of the stator magnetic poles are individually excited by alternating current signals whose phases are shifted from each other, and an output signal is generated by shifting the phase of the alternating current signal to the secondary coil side according to the linear position of the rod. This is achieved by a cylinder position detection device designed to obtain the following. By measuring the amount of phase shift of the signal whose phase is shifted according to the linear position of the rod (for example, by counting with a counter), absolute data indicating the linear position can be obtained.

An embodiment of this invention will be described in detail below with reference to the accompanying drawings.

In FIGS. 1 and 2, the stator assembly 1 has four magnetic poles A, B, C, and D formed by winding primary coils 2 to 5 and secondary coils 6 to 9 at 90 degrees in the circumferential direction. It includes stators 10 arranged at intervals, and the stators 10 are housed in a casing 11. In this stator assembly 1, the center space of the stator 10 is connected to the rod 1 of the cylinder 12.
The rod 13 is fixed to one end of the cylinder 12 with the rod 13 slidably penetrating the central space so as to be concentric with the cylinder 3. Rod 13
includes a core made of a magnetic material around which spiral protrusions 13a are provided at a predetermined pitch, and a cylinder 12 is attached to one end of the core.
The inner piston 14 is attached. and,
A non-magnetic cylindrical sleeve 13b is fitted onto the outermost circumference of the rod 13, allowing the rod 13 to slide smoothly.

The length of one pitch of the spiral protrusion 13a is indicated by P, and the width of the protrusion 13a is approximately equal to the width of the groove 13c. Each pole A to D of the stator 10
The length of the end portion in the axial direction is approximately equal to the width of the spiral protrusion 13a. With this configuration, the reluctance of the gap between the rod 13 and each stator pole A to D changes depending on the linear position of the rod 13,
Moreover, the phase of this change is shifted by 90 degrees for each pole. For example, if the reluctance change of pole A is a cosine, pole B is a sine, pole C is a negative cosine, and pole D is a negative sign.
The reluctance of
Changes differentially.

An example of the connections between the primary coils 2 to 5 and the secondary coils 6 to 9 in the stator 10 is shown in FIG.
The primary coils 2 and 4 of poles A and C are excited in opposite phases to each other by a sine signal sinωt, and the primary coils 3 and 5 of poles B and D are excited in opposite phases to each other by a cosine signal cosωt. Further, the secondary coils 6 and 8 of poles A and C are in phase, and the secondary coils 7 and 9 of poles B and D are also in phase, and the output signal Y is obtained by adding these outputs. In other words, one pair of poles A and C, whose reluctance changes differentially, and another pair of poles B and D are connected to two poles with an electrical phase shift corresponding to the phase shift (that is, 90 degrees) between the reluctance changes of both pairs. They are individually excited by different types of reference AC signals (sinωt, cosωt).
As a result, the output signal Y is obtained by shifting the phase of the reference AC signal by the phase angle φ corresponding to the linear position of the rod 13.
is obtained. The reason is that the reluctance changes of each pole A to D are shifted by 90 degrees, and one pair A,
The electrical phase of the excitation signal of C and the other pair B, D is 90
This is because the degree is off. This point can be expressed briefly as follows.

That is, if the phase corresponding to the linear position of the rod 13 is φ, then the function of reluctance change according to the linear position is cosφ for pole A, sinφ for pole B, and sinφ for pole C.
can be expressed as -cosφ and the pole D as -sinφ. A and C are operated in opposite phases to each other by a sine signal sinωt, and B and D are operated in opposite phases to each other by a cosine signal cosωt, and the resulting 2
Since the outputs of the next coils are additively combined, the output signal Y can be substantially expressed in the following informal formula.

Y=sinωtcosφ−(−sinωtcosφ) +cosωtsinφ−(−cosωtsinφ) =2sinωtcosφ+2cosωtsinφ =2sin(ωt+φ) If we replace the coefficient indicated as “2” in the above formula with a constant K determined according to various conditions, we get It can be expressed as Y=Ksin(ωt+φ). Here, since the phase φ of the reluctance change is proportional to the linear position l of the rod 13 according to a predetermined proportionality coefficient (or function), the phase shift φ from the reference signal sinωt (or cosωt) in the output signal Y is Linear position l by measuring
can be detected. However, the phase shift amount φ
When the full width is 2π, the linear position l corresponds to the above-mentioned distance P (one pitch length of the spiral protrusion 13a). That is, according to the electrical phase shift amount φ in the signal Y, an absolute linear position within the range of the distance P can be detected. If you want to find the absolute straight line position beyond the distance P, use any suitable means (this detection accuracy may be rough with distance P as one unit) and find the absolute address for each distance P. A combination of the absolute address for each distance P and the detected linear position value based on the above-mentioned phase shift φ may be used. By measuring the electrical phase shift φ, it is possible to accurately determine the absolute linear position within the range of distance P with fairly high resolution.

Output signal Y and reference AC signal sinωt (or
cosωt) can be constructed as appropriate. For example, when determining the phase shift φ as a digital quantity, a predetermined phase angle (for example, 0
It is sufficient to use a counter to count the time difference (degrees). A circuit for this purpose is shown in FIG. Further, if this time difference is determined using an integrating circuit, it is also possible to determine the phase shift φ using an analog quantity.

In FIG. 4, the oscillation unit 32 is a reference sine signal.
A circuit for generating sinωt and a cosine signal cosωt, and a phase difference detection circuit 37, is a circuit for measuring the phase shift φ. Clock pulses CP generated by a clock oscillator 33 are counted by a counter 30. The counter 30 is, for example, Modillo M,
The count value is given to register 31. From the 4/M frequency-divided output of the counter 30, a pulse Pc obtained by dividing the clock pulse CP by 4/M is taken out and applied to the C input of a flip-flop 34 for 1/2 frequency division. The pulse Pb output from the Q output of this flip-flop 34 is applied to the flip-flop 35,
The pulse Pa from the Q output is the flip-flop 3
6, and the outputs of these 35 and 36 pass through low-pass filters 21, 22 and amplifiers 23, 24 to obtain a cosine signal cosωt and a sine signal sinωt. The M count in the counter 30 corresponds to the phase angle of 2π radians of these reference signals cosωt and sinωt. That is, one count value of the counter 30 indicates a phase angle of 2π/M radians.

The output signal Y of the coil assembly 1 is applied to a comparator 26 via an amplifier 25, and a square wave signal corresponding to the positive or negative polarity of the signal Y is output from the comparator 26. In response to the rise of the output signal of the comparator 26, a pulse Ts is output from the rise detection circuit 28, and the count value of the counter 30 is loaded into the register 31 in response to this pulse Ts. As a result, a digital value Dφ corresponding to the phase shift φ is taken into the register 31.

The shapes of the spiral protrusions 13a of the stator 10 and the rods 13 can be modified as desired without departing from the gist of this invention. For example, stator 10
The number of magnetic poles is not limited to four, but can be selected as appropriate. Further, the protrusion provided on the rod 13 is not limited to a completely continuous spiral, but has a spiral shape as a whole.
The protrusion may be formed only at the location corresponding to D. Alternatively, as shown in FIG.
d, it is also possible to change the axial position of the teeth T provided at the ends of each magnetic pole A to D on the stator side in a spiral manner to obtain the same effect as when the rod protrusion is spirally shaped. be. Alternatively, the groove of the rod 13 may be filled with a non-magnetic material to make the outer peripheral surface smooth.

As explained above, this invention has the excellent effect of being able to detect the linear position of the cylinder rod absolutely and with high precision.

[Brief explanation of the drawing]

Fig. 1 is an axial sectional view showing an embodiment of the cylinder position detection device according to this invention, Fig. 2 is a sectional view taken along the line - - in Fig. 1, and Fig. 3 is a coil connection in the embodiment of Fig. 1. Circuit diagram showing an example of the format, No. 4
The figure is a block diagram showing an example of a circuit for digitally measuring a phase shift, and FIG. 5 is an axial cross-sectional view showing another embodiment of this invention. 1...Stator assembly, 2-5...Primary coil, 6-9...Secondary coil, 10...Stator, 11...Casing, 12...Cylinder, 1
3... Rod, 14... Piston, 13a... Spiral protrusion, 13b... Non-magnetic sleeve, 13c...
Groove portion, 13d...Ring-shaped protrusion, T...Teeth at the tip of the stator pole.

Claims (1)

[Claims for Utility Model Registration] 1. A magnetic rod that is attached to one end of a piston in a cylinder and has a plurality of protrusions arranged at a predetermined pitch in the axial direction; a stator that is fixedly disposed at a predetermined location of the cylinder and that allows the rod to penetrate in the axial direction; a plurality of magnetic poles provided on the stator so as to cause a deviation in the positional relationship; at least two primary coils energized by the primary coils; and an output wound around the magnetic poles corresponding to the primary coils and phase-shifted by a change in reluctance that occurs in response to the axial displacement of the rod. A cylinder position detection device characterized by comprising a secondary coil that detects a signal. 2. The cylinder position detection device according to claim 1, wherein the rod is provided with spiral protrusions at a predetermined pitch around the rod as the protrusion. 3. The cylinder position detection device according to claim 1 or 2, wherein a sleeve made of a non-magnetic material is fitted around the rod.