JP7500076B2 - Rotation detection type LVDT and driving method thereof - Google Patents

Description

The present invention relates to a rotation detection type LVDT and its driving method, and in particular to a new improvement for detecting rotation and rotation angle by the LVDT by rotating and linearly moving the LVDT probe using a rotation/linear conversion mechanism.

As an example of a rotation detection type LVDT of this type that has been used in the past, the configuration disclosed in Fig. 12 of Patent Document 1 is shown in Fig. 4. That is, in Fig. 4, a rotating shaft 2 is rotatably mounted via a bearing 19 inside a cylindrical case 18.

A cam-shaped swash plate 20 is rotatably provided on the rotary shaft 2, and a mounting plate 26 is provided at approximately the center position in the axial direction P of the cylindrical case 18.
A plurality of LVDTs, i.e., differential transformers 22A, 22B, are provided on the right side of the mounting plate 26 as viewed in FIG. 4, and the tips of probes 27A, 27B biased by springs 28, 29 of each of the LVDTs 22A, 22B abut against the inclined surface 20A of the swash plate 20.

In the above-mentioned configuration, when the swash plate 20 is rotated, the linear positions of the probes 27A, 27B of the LVDTs 22A, 22B change in response to the rotation of the swash plate 20, and the rotation angle of the swash plate 20 can be detected using the output values at the positions of the probes 27A, 27B of the LVDTs 22A, 22B. In other words, the output signals of each channel from the probes 27A, 27B are continuously processed by the circuit to convert the rotation angle of the swash plate 20 into a linear signal.

Although no references are given, the configuration of a currently commonly used LVDT is shown in FIG.
The same parts as those in the conventional example of FIG. 4 are denoted by the same reference numerals.
In the LVDT 22A shown in FIG. 3, reference numeral 18 denotes a cylindrical case. Inside this cylindrical case 18, lead wires 40 are connected and a cylindrical stator winding 24 consisting of primary and secondary windings (not shown) is provided, with an outer surface 24B of the cylindrical case 18 filled with potting material 17.
The potting agent 17 is injected between the cylindrical case 18 and the cylindrical stator winding 24 after the cylindrical stator winding 24 , which is wound cylindrically, is inserted and installed in the cylindrical case 18 .

A probe 27A made of a longitudinal rod is arranged on the inside 24A of the cylindrical stator winding 24 to move back and forth along the axial direction P, and a threaded portion 32 is formed at the rear 31 of its outer end 30.

Japanese Patent Publication No. 3-61126

Conventional rotation detection type LVDTs and general-purpose LVDTs are configured as described above, and therefore have the following problems.
That is, in the case of the former conventional configuration using the swash plate 20 shown in FIG. 4, it was necessary to use a rotating cam-shaped swash plate 20, and the precision of the sloping surface 20A of this swash plate 20 had to be increased, which required a lot of cost to be incurred in machining the swash plate 20.
Furthermore, since there are multiple LVDTs, the output signals of each channel must be processed continuously, resulting in a complex circuit configuration.

In addition, in the case of the general-purpose LVDT 22A shown in Figure 3, which has been used in the past, the probe 27A itself only moves linearly, so in order to detect rotational motion with the probe 27A, a highly accurate and complex rotation/linear conversion mechanism must be attached, resulting in a large configuration combining the LVDT 22A and the rotation/linear conversion mechanism, making it extremely difficult to obtain a rotation/linear conversion mechanism with a compact configuration. In addition, to turn the LVDT 22A of the conventional configuration in Figure 3 into a rotation detection type LVDT without using the above-mentioned rotation/linear conversion mechanism, it is necessary to use a separate sensor, for example, and the only option is to use a rotation sensor with a finite angle using a multi-stage reduction gear mechanism, which results in a large size.

The present invention has been made to solve the above problems, and in particular to provide a rotation detection type LVDT and a driving method thereof, in which the LVDT probe is rotated and linearly moved by a small and simple rotary-linear conversion mechanism, so that the rotation and rotation angle are detected by the LVDT.

The rotation detection type LVDT according to the present invention comprises a cylindrical stator winding provided in a cylindrical case, a probe provided on the cylindrical stator winding so as to be capable of rotating and linearly moving, a first screw portion formed on the probe, a case front cover fixed to one end of the cylindrical case and having a second screw portion meshing with the first screw portion, a spur gear provided on the outer end of the probe, and a feed gear meshing with the spur gear and having a spline shape, and by rotating the feed gear, the probe rotates relative to the second screw portion via the spur gear, and the probe and the spur gear rotate while allowing the probe to move back and forth linearly along the first axial direction of the probe, and the feed gear is integrally formed on the rotating shaft of a motor, and the outer end of the probe protruding outward from the case front cover has a protruding portion that engages with the spur gear, and the probe and the spur gear are fixed by a fixing body provided on the protruding portion, and this The method for driving a rotation detection type LVDT according to the invention uses a cylindrical stator winding provided in a cylindrical case, a probe provided on the cylindrical stator winding so as to be rotatable and linearly movable, a first screw portion formed on the probe, a case front cover fixed to one end of the cylindrical case and having a second screw portion meshing with the first screw portion, a spur gear provided on the outer end of the probe, and a feed gear meshing with the spur gear and having a spline shape, and by rotating the feed gear, the probe rotates relative to the second screw portion via the spur gear, and the probe and the spur gear rotate while being freely linearly movable back and forth along the first axial direction of the probe, and the feed gear is integrally formed on the rotating shaft of a motor, and the outer end of the probe protruding outward from the case front cover has a protrusion that engages with the spur gear, and the probe and the spur gear are fixed by a fixing body provided on the protrusion.

Since the rotation detection type LVDT according to the present invention is configured as described above, it is possible to obtain the following effects.
That is, the LVDT comprises a cylindrical stator winding provided on a cylindrical case, a probe provided on the cylindrical stator winding so as to be capable of rotating and translating freely, a first threaded portion formed on the probe, a case front cover fixed to one end of the cylindrical case and having a second threaded portion meshing with the first threaded portion, a spur gear provided on the outer end of the probe, and a feed gear meshing with the spur gear and having a spline shape, and by rotating the feed gear, the probe rotates relative to the second threaded portion via the spur gear, and the probe and the spur gear are configured to be capable of reciprocating and translating freely along the first axial direction of the probe while rotating, thereby making it possible to detect rotation by the LVDT by adding at least three parts (case front cover, feed gear, and spur gear).
Furthermore, there is no need to change the system configuration for processing the output signal from the LVDT, and rotation detection is possible using conventional LVDT signal processing.
In addition, because the rotation speed and sliding range can be adjusted by the thread pitch of the feed gear, spur gear, and first and second threads (reduction mechanism), the size of the LVDT is not an issue, and it can be customized to fit the mounting shape and can also be made smaller. In the future, it is expected to be used as a position detection sensor from the motor shaft when hydraulic pistons are electrified.
Furthermore, since the feed gear is integrally formed with the rotating shaft of the motor, a plurality of feed gears can be prepared in accordance with the specifications of the rotating shaft of the motor.
In addition, the outer end of the probe protruding outward from the front lid of the case has a protrusion that connects with the spur gear, and the probe and the spur gear are fixed by a fixing member provided on the protrusion, so that the spur gear and the probe can be freely disassembled and fixed by attaching and detaching the fixing member.

1 is a cross-sectional view showing a rotation detection type LVDT according to an embodiment of the present invention; FIG. 2 is an enlarged cross-sectional view of the front cover of the case of FIG. 1 . FIG. 2 is a cross-sectional view showing the conventional LVDT of FIG. 1. FIG. 1 is a cross-sectional view showing another embodiment of a conventional LVDT.

The present invention allows the LVDT probe to be rotated and translated using a rotary-linear conversion mechanism, making it possible to detect rotation and the angle of rotation using the LVDT.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a rotation detection type LVDT and a driving method thereof according to the present invention will now be described with reference to the drawings.
In addition, the same parts as those in the conventional example are denoted by the same reference numerals.
In FIG. 1, the reference numeral 22A denotes a well-known differential transformer (hereinafter referred to as an LVDT). This LVDT 22A has a cylindrical case 18. A lead wire 40 is connected to the inside 18A of this cylindrical case 18. A cylindrical stator winding 24 consisting of primary and secondary windings (not shown) is provided, and its outer surface 24B is filled with potting material 17.
The potting agent 17 is injected into the cylindrical case 18, i.e., into the space 18E between the cylindrical case 18 and the cylindrical stator winding 24 after the cylindrical stator winding 24 is inserted and fixed into the inner side 18A.

A probe 27A made of a longitudinal rod is provided on an inner side 24A of the cylindrical stator winding 24 so as to be capable of rotating and of linearly reciprocating along the first axial direction P.
The probe 27A has a probe core 27D at its inner end 27C, and a first screw portion (male screw structure) 25 is formed on the outer periphery of the probe 27A.

A case front cover 50 is fixed to one end 18B of the cylindrical case 18, and a second screw portion (female screw structure) 42 consisting of a through hole 50A is formed at the axis of this case front cover 50 and meshes with the first screw portion 25. In other words, the case front cover 50 has the same function as a nut with respect to the probe 27A, and by rotating the probe 27A with respect to the fixed case front cover 50, the probe 27A moves linearly while rotating via the screwing of the first and second screw portions 25, 42.
The first screw portion 25 of the probe 27A penetrates the through hole 50A while meshing (screwing) with the second screw portion 42.
Therefore, when only the probe 27A is rotated in the above-mentioned state, the first and second screw portions 25, 42 act to allow only the probe 27A to move freely in the linear direction along the first axial direction P. The pitch of the rotation depends on the tooth pitch of the first and second screw portions 25, 42.

A spur gear 60 of a known anti-backlash gear structure is fixed and connected by screw fixing or the like to the outer end 30 of the probe 27A that protrudes outward from the case front cover 50, and a nut-shaped fixing body 62 is fixed by fitting, press fitting or screw fastening to a protruding portion 61 that protrudes outward from the outer end 30. The spur gear 60 and the probe 27A are fixed on the outer end 30 by the fixing body 62 provided on this protruding portion 61.

A feed gear 72 is disposed in the vicinity of the spur gear 60 and has a spline shape formed on a tip 71A of a rotating shaft 71 of a motor 70 (or another rotating device), and meshes with the spur gear 60. This feed gear 72 meshes with the spur gear 60, and when the feed gear 72 is rotated by the motor 70, the spur gear 60 rotates in the direction of an arrow in a rotation direction B opposite to the rotation direction A of the rotating shaft 71, and the probe 27A also rotates relative to the second screw portion 42 and in the direction of the arrow in the rotation direction B. The feed gear 72 is formed integrally with the rotating shaft 71 or is provided separately.
When the probe 27A rotates in the rotation direction B, the first and second threaded portions 25, 42 mesh with each other, and the probe 27A moves linearly to the left or right in the first axial direction P according to the way the threads are cut. Therefore, the probe 27A and the spur gear 60 can move linearly back and forth along the first axial direction P of the probe 27A.
In addition, in the above-mentioned case, the spur gear 60, which moves linearly simultaneously with the probe 27A, moves linearly together with the probe 27A, and therefore moves linearly along either the left or right direction as shown by the second axial direction P' indicated by the arrow along the gear groove 72A of the feed gear 72.

The case front cover 50, the first and second screw portions 25, 42, the spur gear 60, the feed gear 72 and the rotary shaft 71 constitute a rotary-linear motion conversion mechanism 100 for rotating and linearly moving the probe 27A.
Therefore, by removing some of the components of the existing LVDT 22A shown in Fig. 3 and adding the components of the present invention, the rotary-to-linear conversion mechanism 100 can be reproduced as a rotation detection type LVDT according to the present invention as shown in Fig. 1, so that the rotary-to-linear conversion mechanism 100 can be retrofitted to a conventional LVDT 22A. Therefore, the configuration of the present invention makes it possible to detect finite angles and multiple rotations over a wide range. In addition, the output signal is always a linear electrical signal, making signal processing easy.

The rotation detection LVDT of the present invention can be changed to a configuration in which rotation is detected by the LVDT by simply adding a probe, case front cover, spur gear, and feed gear to a conventional LVDT, and can be made much smaller than conventional rotation detection LVDTs, making it applicable as a rotation sensor when converted from a hydraulic piston to an electric motor.

17 potting material 18 cylindrical case 18A inside 18B one end 18E space 22A LVDT
24 Cylindrical stator winding 24A Inner surface 24B Outer surface 25 First screw portion (male screw structure)
27A Probe 27D Probe core 27C Inner end 30 Outer end 40 Lead wire 42 Second screw portion (female screw structure)
50 Case front cover 50A Through hole 60 Spur gear (anti-backlash gear)
61 Protrusion 62 Fixed body 70 Motor 71 Rotating shaft 71A Tip 72 Feed gear (spline shape)
72A Gear groove 100 Rotation-to-linear motion conversion mechanism A, B Rotation direction P First axial direction P' Second axial direction

Claims (6)

the cylindrical case (18) is provided with a cylindrical stator winding (24); a probe (27A) provided on the cylindrical stator winding (24) so as to be capable of rotating and translating; a first threaded portion (25) formed on the probe (27A); a case front cover (50) fixed to one end (18B) of the cylindrical case (18) and having a second threaded portion (42) meshing with the first threaded portion (25); a spur gear (60) provided on an outer end (30) of the probe (27A); and a spline-shaped feed gear (72) meshing with the spur gear (60),
A rotation detection type LVDT characterized in that, by rotating the feed gear (72), the probe (27A) rotates relative to the second threaded portion (42) via the spur gear (60), and the probe (27A) and the spur gear (60) are freely movable back and forth along a first axial direction (P) of the probe (27A) while rotating. The rotation detection type LVDT according to claim 1, characterized in that the feed gear (72) is integrally formed with the rotating shaft (71) of the motor (70). The rotation detection type LVDT according to claim 1 or 2, characterized in that the outer end (30) of the probe (27A) protruding outward from the case front cover (50) has a protruding portion (61) that is coupled to the spur gear (60), and the probe (27A) and the spur gear (60) are fixed by a fixing body (62) provided on the protruding portion (61). a cylindrical stator winding (24) provided in a cylindrical case (18), a probe (27A) provided on the cylindrical stator winding (24) so as to be rotatable and translatable, a first screw portion (25) formed on the probe (27A), a case front cover (50) fixed to one end (18B) of the cylindrical case (18) and having a second screw portion (42) meshing with the first screw portion (25), a spur gear (60) provided on an outer end (30) of the probe (27A), and a spline-shaped feed gear (72) meshing with the spur gear (60),
a driving method for a rotation detection type LVDT, characterized in that by rotating the feed gear (72), the probe (27A) rotates relative to the second screw portion (42) via the spur gear (60), and the probe (27A) and the spur gear (60) are freely moved back and forth in a linear motion along a first axial direction (P) of the probe (27A) while rotating. The method for driving a rotation detection type LVDT according to claim 4, characterized in that the feed gear (72) is integrally formed with the rotating shaft (71) of the motor (70). The method for driving a rotation detection type LVDT according to claim 4 or 5, characterized in that the outer end (30) of the probe (27A) protruding outward from the case front cover (50) has a protruding portion (61) that is coupled with the spur gear (60), and the probe (27A) and the spur gear (60) are fixed by a fixing body (62) provided on the protruding portion (61).