JPH0226002Y2 - - 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 absolutely detect the position of a cylinder. This purpose is
A plurality of 1s arranged in a predetermined arrangement shifted in the axial direction
A coil assembly including a primary coil and a secondary coil provided corresponding to the primary coil is arranged so that the coil space is approximately concentric with the rod of the cylinder, and the rod can be freely slid into the coil space. The rod is fixed at a predetermined location on the cylinder in a state where the rod is penetrated, and on the other hand, a plurality of magnetic rings are provided around the rod at predetermined intervals in the axial direction, and the primary coil is energized so that the rod is attached to the secondary coil side. This is achieved by a cylinder position detection device which obtains an output signal depending on the linear position of the rod. The linear position is determined by exciting the primary coil so that a signal whose phase is shifted according to the linear position of the rod is obtained on the secondary side, and by measuring the amount of phase shift of this output signal (for example, by counting it with a counter). The absolute data shown is obtained.

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

In FIG. 1, a coil assembly 1 includes four primary coils 2, 3, 4, and 5 arranged in a predetermined arrangement shifted in the axial direction, and a secondary coil 6 provided correspondingly. , 7, 8, 9 and the casing 10
The rod 12 is fixed at a predetermined location of one end 11a of the cylinder 11 in such a manner that the rod 12 is slidably passed through the coil space so that the cylindrical space of the coil is concentric with the rod 12. ing. The rod 12 is a cylindrical shaft 12 with a piston 13 in the cylinder 11 attached to one end.
a, and a plurality of annular magnetic rings 12b having a predetermined width that are alternately fitted in the axial direction around the mandrel 12a.
and an annular non-magnetic spacer 12c, and a cylindrical non-magnetic sleeve 12d fitted on the outermost periphery of these spacers. Non-magnetic spacer 12
c is a solid nonmagnetic substance or air. As an example, the length (width) of each magnetic ring 12b is "P/2" (P is an arbitrary number), the same is true for the spacer 12c, and the interval for one pitch in the alternate arrangement is "P". . In this example, the coils are 4
It is arranged to operate in two phases. For convenience, these phases are distinguished using symbols A, B, C, and D. The reluctance generated in each phase A to D is shifted by 90 degrees depending on the position of the magnetic ring 12b of the rod 12. For example, if phase A is a cosine phase, phase B is a sine phase and phase C is a negative cosine phase. The phase and D phase are designed to be negative sign phases. In the embodiment of FIG. 1, each phase A~
Primary coils 2 to 5 and secondary coil 6 individually for each D
-9 are provided. The secondary coils 6 to 9 of each phase A to D are wound outside the corresponding primary coils 2 to 5, respectively. The length of each coil is approximately equal to the length of the magnetic ring 12b, which is "P/2". In the example shown in Fig. 1, the A-phase coils 2, 6 and the C-phase coils 3, 7 are installed adjacent to each other, and the B-phase coils 4, 8 and the D-phase coils 5, 9 are also installed adjacent to each other. It is set up. Further, the interval between the A-phase and B-phase or C-phase and D-phase coils is "P(n±1/4)" (n is any natural number). With this configuration, the rod 12
The reluctance of the magnetic circuit in each phase A to D changes according to the linear displacement of the magnetic ring (more specifically, the magnetic ring), and the phase of the reluctance change shifts by 90 degrees for each phase (therefore, the phase A and C are There is a 180 degree shift between the B phase and D phase. Primary coils 2-5 and secondary coils 6-
9 is connected as shown in Figure 2. Figure 2 shows
A sine signal for primary coils 2 and 3 of A phase and C phase
This shows a wiring configuration in which the secondary coils 6 and 7 are excited in opposite phases by sinωt, and the outputs of the secondary coils 6 and 7 are added in the same phase. Similarly to the above, for the B phase and D phase, the primary coils 4 and 5 are excited in opposite phases with the cosine signal cosωt, and the outputs of the secondary coils 8 and 9 are added in phase.
The outputs of the secondary coils are finally summed to obtain the output signal Y. On the other hand, the present invention is not limited to this, and one of the A phase and C phase
The secondary coils 2 and 3 are excited in the same phase by the sine signal sinωt, the secondary coils 6 and 7 are connected in opposite phases, and the primary coils 4 and 5 of the B phase and D phase are excited in the same phase by the cosine signal cosωt. The secondary coils 8 and 9 may be connected in reverse phase, and the outputs of the secondary coils may be finally added.

In short, the wiring format shown in FIG. 2 can be expressed as follows. In other words, two phases (A and C or B and D) whose reluctance changes are shifted by 180 degrees are operated in opposite phases, and two pairs whose reluctance changes are shifted by 90 degrees (a pair of A and C and a pair of B and One of the pair D) is excited by a sine signal sinωt, and the other is excited by a cosine signal cosωt. In other words, the two pairs (the pair A and C or the pair B and D) are the same as two differential transformers whose reluctance changes are out of phase by 90 degrees; Each of them is individually excited by two types of alternating current signals (sinωt, cosωt) having electrical phase shifts corresponding to . The output signal Y is the sum of the secondary coil outputs of the A, C phase pair and the B, D phase pair.
becomes. This output signal Y is obtained by phase-shifting the reference AC signal (sinωt or cosωt) by a phase angle φ corresponding to the linear position of the magnetic ring 12b in the rod 12. The reason for this is that the reluctance of each phase A to D is shifted by 90 degrees, and the electrical phases of the excitation signals of one pair (A, C) and the other pair (B, D) are shifted by 90 degrees. It's for a reason. This point can be expressed briefly as follows.

That is, if the phase corresponding to the linear position of the magnetic ring 12b is φ, the function of reluctance change according to the linear position is cosφ for the A phase, sinφ for the B phase,
The C phase can be expressed as -cosφ and the D phase as -sinφ. The A and C phases are operated in opposite phases to each other by a sine signal sinωt, and the B and D phases are operated in opposite phases to each other by a cosine signal cosωt, and the resulting secondary coil output is additively Therefore, 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 magnetic ring 12b according to a predetermined proportionality coefficient (or function),
Reference signal sinωt (or
By measuring the phase shift φ from cosωt), the linear position l can be detected. However, when the phase shift amount φ is 2π in full width, the linear position l corresponds to the distance P described above. 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. When it is desired to obtain an absolute linear position beyond the distance P, an appropriate arbitrary means (the detection accuracy may be coarse with the distance P being one unit) is installed to detect each magnetic ring 12b on the rod 12.
It is sufficient to find the absolute address of each ring 12b and use a combination of the absolute address of each ring 12b and the detected linear position value based on the above-mentioned phase shift φ. 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. FIG. 3 shows an example of a circuit in which the phase shift φ is determined as a digital quantity. Although not particularly shown, the phase shift φ can be determined as an analog quantity by determining the time difference of a predetermined phase angle (for example, 0 degrees) between the reference AC signal sinωt and the output signal Y=Ksin(ωt+φ) using an integrating circuit. You can also do it.

In FIG. 3, 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 sent to the amplifier 25
A square wave signal corresponding to the positive/negative polarity of the signal Y is outputted from the comparator 26 via 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.

Note that the method of providing each phase A to D is not limited to the method described above. For example, as shown in FIG.
Each coil 2-5, 6-9 is connected at a predetermined interval "P" in order of phase.
(n±1/4)". Further, the primary coils 2 to 5 and the secondary coils 6 to 9 of each phase may be wound together by bifilar winding. Alternatively, as shown in Fig. 5, the A phase and C phase may share the primary coil 2 (or secondary coil), and the secondary coils 6 and 7 (or primary coils) may be connected in opposite phases. . Similarly, the B phase and the D phase share the primary coil 4, and the secondary coils 8 and 9 are connected in opposite phases.

In addition, phases A and C or B and D forming a pair
contributes to increasing precision by differentially deepening the output signal level. If accuracy is not required, it is also possible to omit the C-phase and D-phase coils. Further, the number of coils (number of phases) is not limited to four or two, but may be more.

In FIG. 1, the shaft 12a of the rod 12 may be made of either a magnetic material or a non-magnetic material. When the mandrel 12a of the rod 12 is made of a magnetic material, a plurality of annular protrusions having a predetermined width are formed at predetermined intervals in the axial direction on the outer circumference of the magnetic mandrel, thereby forming the annular protrusions as the magnetic ring 12b. You can also do that. Even in that case, it is preferable to provide a non-magnetic sleeve 12d on the outermost periphery to ensure smooth sliding of the rod 12.

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 the invention, FIG. 2 is a circuit diagram showing an example of the coil connection type in the embodiment of FIG. 1, and FIG. A block diagram showing an example of a circuit for measuring the phase shift between the secondary coil output signal and the reference AC signal in the coil assembly shown in FIG. 1 as a digital quantity, and FIGS. 4 and 5 show other embodiments of this invention. FIG. 1...Coil assembly, 2-5...Primary coil, 6-9...Secondary coil, 10...Casing, 11...Cylinder, 12...Rod, 12a
...Mandrel, 12b...Magnetic ring, 12c...Nonmagnetic spacer, 12d...Sleeve, 13...Piston.

Claims (1)

[Claims for Utility Model Registration] 1. A ring-shaped magnetic material and a non-magnetic material having equal axial lengths are arranged around a shaft attached to one end of a piston in a cylinder at a predetermined pitch P in the axial direction. and a reference AC signal fixed to the cylinder so as to be displaced relative to the rods and having a predetermined phase difference (360°/D) other than 180° or 360°. Therefore, at least two rods are individually excited and provided around the rod and separated from each other by a predetermined distance P×{n±(1/D)} (where n is an arbitrary integer) in the axial direction. a primary coil, and a primary coil provided corresponding to the primary coil,
A cylinder position detection device comprising: a coil assembly including a secondary coil for detecting an output signal whose phase is shifted due to a change in reluctance caused in response to displacement of the rod in the axial direction. 2. The mandrel is made of a magnetic material, and annular protrusions of a predetermined width are formed on the outer periphery of the mandrel at predetermined intervals in the axial direction as the ring-shaped magnetic material. Cylinder position detection device as described in . 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. 4 The primary and secondary coils are composed of 4-phase coil groups, and the phase of reluctance change of each phase according to the linear position of the ring-shaped magnetic body is 90°.
The reluctance changes are arranged so as to be shifted by 180 degrees, and the two phases in which the reluctance change is 180 degrees apart are operated in opposite phases using a sine wave signal as the reference AC signal, and the reluctance change is 180 degrees apart. Utility model registration claim 3 in which two separate phases are operated in opposite phases by using a cosine wave signal as the reference AC signal.
Cylinder position detection device as described in .