JP2019215231A - Digital micrometer - Google Patents

Abstract

To provide a digital micrometer suitable for measuring a ferromagnetic measuring object.SOLUTION: A digital micrometer comprises: a body frame having an anvil inside one end of a U shape; a spindle provided at the other end of the body frame so as to be able to advance and retreat in the axial direction; a thimble unit that is provided on the other end of the body frame, and converts a rotation operation into a linear motion of the spindle; and an encoder having a main scale that moves integrally with the spindle and a detection head that detects a relative position with respect to the main scale. The body frame and the spindle are formed of a non-magnetic metal material.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a digital micrometer.

  In recent years, development and production of permanent magnet synchronous motors have been spurred due to an increase in demand for hybrid vehicles and electric vehicles. Powerful magnets are indispensable for high-performance permanent magnet synchronous motors. Therefore, the processing accuracy of the magnet incorporated into the permanent magnet synchronous motor becomes a problem.

  Generally, a small measuring instrument such as a micrometer or a vernier caliper is convenient and suitable for measuring the processing accuracy of a small component, but the main components such as the frame of the small measuring instrument are iron (cast iron) products. Then, just by bringing the measuring object, which is a strong magnet, close to the small measuring instrument, the two stick together strongly, and it is difficult to measure as well as to peel off. Therefore, conventionally, when a small part is a strong magnet, a large measuring machine such as a three-dimensional measuring machine has to be used. This has a considerable impact on production efficiency and manufacturing costs.

  Various small measuring instruments suitable for use in a magnetic field have been proposed so far. However, there was no digital type that could withstand practical use.

51-82480 JP-A-60-236001 50-50053 JP 2009-243883 Patent 4072282 Utility Model Registration No. 3184265 JP-A-58-115301

In order to make a small measuring instrument suitable for use in a magnetic field, it is conceivable that a main component of the small measuring instrument is a non-magnetic material. However, strong non-magnetic materials are difficult-to-cut materials. For example, in a micrometer, it is necessary to cut a high-precision male screw on a spindle or to tap a high-precision female screw on a main body frame, but it has been difficult to perform this on a nonmagnetic material.
A digital micrometer capable of measuring a ferromagnetic measurement target and having practical accuracy has been desired.

  An object of the present invention is to provide a digital micrometer suitable for measuring a ferromagnetic measurement target.

The digital micrometer of the present invention is
A body frame having an anvil inside one end of the U-shape;
On the other end side of the main body frame, a spindle that is provided so as to advance and retreat in the axial direction so as to advance and retreat with respect to the anvil, and has a contact on one end surface;
A thimble part provided on the other end of the main body frame, receiving the other end of the spindle, and converting a rotation operation into a linear motion of the spindle;
A digital micrometer comprising: a main scale that moves integrally with the spindle; and an encoder that is disposed on the main body frame and has a detection head that detects a relative position or a relative displacement amount with respect to the main scale,
The main body frame and the spindle are formed of a non-magnetic metal material,
The thimble part is
An inner sleeve having a slit along the axis and fixedly provided on the other end side of the main body frame;
An outer sleeve that is externally fitted in a circumferentially rotatable manner with respect to the inner sleeve, and that has a spiral groove on the inner peripheral surface,
An engagement pin fixedly provided on the spindle is engaged with the spiral groove through the slit.

In the present invention,
The main body frame is formed of austenitic stainless steel, pure aluminum or a nonmagnetic aluminum alloy,
The spindle is preferably made of austenitic stainless steel.

In the present invention,
It is preferable that the anvil and the contact are made of ceramic.

In the present invention,
On the other end side of the main body frame, a guide bush for bearing the spindle is provided on the side close to the anvil,
The guide bush is preferably made of brass.

In the present invention,
The inner sleeve is preferably made of brass, pure aluminum, nonmagnetic aluminum alloy, or austenitic stainless steel.

In the present invention,
The encoder is preferably a capacitance encoder, a photoelectric encoder, an electromagnetic induction encoder, or a magnetic encoder.

In the present invention,
The main body frame is formed of austenitic stainless steel,
The spindle is made of austenitic stainless steel,
The inner sleeve is made of brass,
The encoder is preferably a capacitive encoder.

It is a front view showing the external appearance of a digital micrometer. FIG. 2 is a partial cross-sectional view illustrating an internal structure of a digital micrometer. It is an exploded perspective view of a thimble part. It is a disassembled perspective view of a detection part.

An embodiment of the present invention will be illustrated and described with reference to reference numerals attached to elements in the drawing.
(First embodiment)
A first embodiment according to the digital micrometer 100 of the present invention will be described.
FIG. 1 is a front view showing the appearance of the digital micrometer 100.
FIG. 2 is a cross-sectional view showing the internal structure of the digital micrometer 100.
The digital micrometer 100 includes a main body frame 200, a spindle 300, a thimble unit 400, and a detection unit 500.

The main body frame 200 is generally U-shaped, and an anvil 210 is provided inside one end of the U-shape.
A spindle 300 is provided on the other end side of the main body frame 200 so as to be able to advance and retract. At this time, on the other end side of the main body frame 200, the guide bush 220 is attached to the side close to the anvil 210, and the thimble part 400 is attached to the side far from the anvil 210.
A display panel 201 is disposed on the front side of the main body frame 200. The display panel 201 is provided with a digital display unit 230 and a plurality of operation switches 240. The display panel 201 is formed of a non-magnetic material such as plastic or resin.

  Here, the main body frame 200 is preferably formed of austenitic stainless steel. Austenitic stainless steel is a strong and non-magnetic material.

  Alternatively, the main body frame 200 may be formed of pure aluminum or a non-magnetic aluminum alloy.

  Preferably, the anvil 210 is formed of ceramic. An example of the ceramic composition is zirconia.

The guide bush 220 is preferably formed of brass. Brass is a non-magnetic material and a free-cutting material.
Note that the guide bush 220 may be formed of austenitic stainless steel.
However, it is considered preferable to have a hardness difference in the relationship between the sliding shaft and the hole.
In the case of a micrometer, it is preferable that the hardness of the spindle is increased and the hardness of the guide bush is designed to be low so that the guide bush is worn during durability.
Austenitic stainless steel cannot be hardened. This is because, when quenched, some magnetism occurs or softens. Therefore, austenitic stainless steel cannot control the hardness difference due to the difference in quenching. Therefore, when it is necessary to select different materials for the spindle and the guide bush, and the spindle 300 is formed of austenitic stainless steel, the guide bush 220 is preferably made of brass.

The spindle 300 is generally a long rod-shaped cylindrical body, and is manufactured straight.
A contact 310 is provided on one end surface of the spindle 300. When measuring the object to be measured, the spindle 300 is moved forward and backward, and the object to be measured is sandwiched between the contact 310 and the anvil 210. An intermediate portion of the spindle 300 is supported by a guide bush 220, and the other end of the spindle 300 is inserted into the thimble portion 400.

An engaging piece member 330 is connected to the other end of the spindle 300.
The bridge member is an annular member, and is fixedly fitted to the other end of the spindle 300. Specifically, a taper 320 that reduces the diameter is provided at the other end of the spindle 300, and a taper hole 331 that receives the other end of the spindle 300 is provided in the engagement piece member 330. The engagement pin member 332 is press-fitted into the engagement piece member 330, and the engagement pin 332 is provided so as to project in a direction perpendicular to the axial direction of the spindle 300.

  In the present embodiment, a male screw is not cut in the spindle 300, and the spindle 300 itself does not rotate. The spindle 300 advances and retreats in the axial direction without rotation.

  The spindle 300 is preferably formed of austenitic stainless steel.

  In addition, it is preferable that the contact 310 be a thin chip made of ceramic, like the anvil 210.

  The engagement piece member is preferably formed of brass.

FIG. 3 is an exploded perspective view of the thimble part 400.
The thimble part 400 is an overall cylindrical unit provided on the other end side of the main body frame 200. The other end side of the spindle 300 is received inside the thimble part 400.
The user moves the spindle 300 forward and backward by rotating the thimble unit 400.
The thimble part 400 includes an inner sleeve 410, an outer sleeve 420, and a cover member 430.

The inner sleeve 410 is a cylindrical member having both ends opened, and has one slit 411 along the axis. One end of the inner sleeve 410 is fixedly attached to the other end of the main body frame 200. The other end of the spindle 300 is inserted from an opening on one end side of the inner sleeve 410. At this time, the other end of the spindle 300 is inserted into the inner sleeve 410, and the engaging pin 332 is pressed into the engaging piece member 330 through the slit 411 so that the engaging pin 332 projects from the slit 411.
The inner diameter of the inner sleeve 410 is designed to be the same as the outer diameter of the engagement piece member 330.
The engagement piece member 330 slides inside the inner sleeve 410 together with the spindle 300 in a state where the engagement piece member 330 is supported on the inner peripheral surface of the inner sleeve 410. At this time, since the engaging pin 332 protrudes from the slit 411, the spindle 300 moves forward and backward in a state where the spindle 300 is prevented from rotating by the engaging pin 332.

  A cap 412 is screwed into the opening at the other end of the inner sleeve 410.

  The outer sleeve 420 is a cylindrical member having both ends opened, and the outer sleeve 420 is provided so as to fit outside the inner sleeve 410. At this time, the outer sleeve 420 is rotatable in the circumferential direction with respect to the inner sleeve 410. Here, a single spiral groove 421 is formed on the inner peripheral surface of the outer sleeve 420. The engagement pin 332 is engaged with the spiral groove 421.

  The cover member 430 is a cover that covers the outer side of the outer sleeve 420, and has a knurled surface. There is no slip between the cover member 430 and the outer sleeve 420, and the cover member 430 and the outer sleeve 420 rotate integrally.

  When the cover member 430 is rotated in the circumferential direction, the outer sleeve 420 rotates in the circumferential direction together with the cover member 430. Here, the engagement pin 332 is engaged with the spiral groove 421 on the inner periphery of the outer sleeve 420, and the rotation of the engagement pin 332 is restricted by the slit 411 of the inner sleeve 410. Therefore, the engaging pin 332 is pushed by the spiral groove 421 by the rotation operation of the cover member 430 and moves forward and backward. Since the engagement pin 332, the engagement piece member 330, and the spindle 300 are integrated, the spindle 300 also advances and retreats when the engagement pin 332 advances and retreats.

  Since the spindle 300 is made of austenitic stainless steel, it is difficult to thread the spindle itself as a mechanism for moving the spindle 300 forward and backward. In this regard, in this embodiment, a configuration is adopted in which the rotation-engaged engagement pin 332 is moved by the spiral groove 421 of the outer sleeve 420.

Here, the inner sleeve 410 is preferably formed of brass.
Brass is a non-magnetic material and a free-cutting material. Since the inner sleeve 410 is a bearing material, machining accuracy of the inner diameter is required. In addition, a slit 411 is formed in the inner sleeve 410, and the slit 411 secures the straightness of movement of the spindle 300 and realizes rotation prevention. As will be described later, when the movement of the spindle 300 is detected by the encoder 510, the main scale 511 is directly or indirectly attached to the spindle in this embodiment. Therefore, if the spindle 300 rotates even a little, it affects the detection accuracy of the encoder. From this viewpoint, since it is difficult to process with austenitic stainless steel, it is considered that brass is preferable as the material of the inner sleeve 410.
Alternatively, the inner sleeve 410 may be formed of pure aluminum or a non-magnetic aluminum alloy. In the case of pure aluminum or an aluminum alloy, there are advantages that thermal expansion is large (linear expansion coefficient is large) and rigidity (Young's modulus) is slightly inferior, but easy to process and lightweight. . If the main body frame 200 is formed of austenitic stainless steel, the inner sleeve 410 may be formed of pure aluminum or aluminum alloy in consideration of the overall weight balance. For a small measuring instrument (small tool), it is desirable that it is heavy enough not to be a burden even if it is held with one hand for a long time, and it is hard to break when dropped and is safe.
Conversely, if the body frame 200 is made of pure aluminum or a non-magnetic aluminum alloy, the inner sleeve 410 may be made of brass.
Furthermore, the inner sleeve 410 may be formed of austenitic stainless steel. Austenitic stainless steel can be said to be preferable as a material for a measuring instrument in terms of low thermal expansion and high strength among nonmagnetic materials. However, there is a problem that processing is difficult and weight increases.

  The outer sleeve is a resin molded product (for example, a liquid crystal polymer). The cover member is preferably formed of a resin molded product.

Next, the configuration of the detection unit 500 will be described.
FIG. 4 is an exploded perspective view of the detection unit 500.
The detection unit 500 includes an encoder 510 and a head fixing unit 530. The encoder 510 is a linear encoder 510 and includes a long main scale 511 and a detection head 512.
The main scale 511 and the detection head 512 can be relatively moved along the longitudinal direction of the main scale 511, and the detection head 512 detects a position or displacement with respect to the main scale 511.
In the present embodiment, the detection head 512 is fixed to the main body frame 200, and the main scale 511 moves forward and backward with the spindle 300.

Here, the linear encoder 510 is of a capacitance type. That is, the main scale 511 is provided with grid electrodes arranged on the glass substrate at a predetermined pitch in the longitudinal direction.
The detection head 512 has a plurality of sets of transmission electrodes and reception electrodes provided on a glass substrate. Then, a predetermined AC signal is transmitted from the transmission electrode of the detection head 512 to the grid electrode of the main scale 511, and the potential of the grid electrode induced by the AC signal is read by the reception electrode. Thereby, the detection head 512 detects a position or a displacement with respect to the main scale 511.

  A flat surface is formed on the side surface of the spindle 300, and this flat surface serves as the scale pedestal 520. A main scale 511 is attached and fixed to the scale base 520. As a result, the main scale 511 moves forward and backward with the spindle 300.

  The head fixing section 530 includes a head holding plate 531, a holding plate 533, and a fixing plate 534.

  The detection head 512 is attached to one surface (back surface) of the head holding plate 531. On one surface of the head holding plate 531, a plurality of (three) projections 532 are formed at positions not interfering with the detection head 512, and the tips of the projections 532 slidably contact the main scale 511. As a result, the detection head 512 faces the main scale 511 while positioning a predetermined gap.

  The pressing plate 533 is a leaf spring that presses the other surface (front surface) of the head holding plate 531 to press the head holding plate 531 against the main scale 511. The holding plate 533 pushes the head holding plate 531 from the front surface with a cantilever-like plate spring.

  The fixed plate 534 holds the holding plate 533 in a cantilever shape. Further, the fixing plate 534 is screwed to a mounting base 250 formed on the main body frame 200.

  For example, the head fixing portion 530, the head holding plate 531, the holding plate 533, and the fixing plate 534 are formed of austenitic stainless steel.

  A flexible printed circuit board 540 is provided inside the main body frame 200, and includes an encoder 510 (main scale 511, detection head 512), an external output terminal 541, a GND terminal 542, an arithmetic processing circuit, a digital display unit 230, and operation switches 240. Wiring is done.

In the present embodiment, a configuration in which the engagement pin 332 is moved by rotation of the spiral groove 421 is employed as a movement mechanism of the spindle 300. However, in this configuration, since the accuracy of the spiral groove 421 is limited, it is difficult to accurately obtain the displacement amount of the spindle 300 from the rotation amount of the thimble portion 400.
In this regard, the present embodiment adopts a configuration in which the displacement of the spindle 300 is detected by the encoder 510.

Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.
As the encoder, a capacitance type linear encoder is exemplified.
In addition, a photoelectric encoder, an electromagnetic induction encoder, and a magnetic encoder can be employed.

As the encoder, an encoder using a glass substrate for both the main scale and the detection head, as in the above embodiment, would be better.
However, only the chip of the arithmetic processing circuit may be surrounded by a magnetic shield material (for example, a ferromagnetic metal). If the tip is sufficiently small, the force (magnetic force) generated between the measurement object (work), which is a strong magnet, does not increase so much.

100: Digital micrometer,
200 ... body frame,
210 ... anvil, 220 ... guide bush, 230 ... digital display, 240 ... operation switch, 250 ... mounting base,
300 ... spindle, 310 ... contact, 320 ... taper,
330 ... engaging piece member, 331 ... taper hole, 332 ... engaging pin,
400 ... Thimble part,
410 ... inner sleeve, 411 ... slit, 412 ... cap,
420 ... outer sleeve, 421 ... spiral groove,
430 ... cover member,
500 ... detection part,
510 ... Encoder, 511 ... Main scale, 512 ... Detection head,
520 ... Scale pedestal,
530 ... Head fixing part,
531: Head holding plate, 532: Projection, 533: Presser plate, 534: Fixed plate.
540: Flexible printed circuit board.

Claims (7)

A body frame having an anvil inside one end of the U-shape;
On the other end side of the main body frame, a spindle that is provided so as to advance and retreat in the axial direction so as to advance and retreat with respect to the anvil, and has a contact on one end surface;
A thimble part provided on the other end of the main body frame, receiving the other end of the spindle, and converting a rotation operation into a linear motion of the spindle;
A digital micrometer comprising: a main scale that moves integrally with the spindle; and an encoder that is disposed on the main body frame and has a detection head that detects a relative position or a relative displacement amount with respect to the main scale,
The main body frame and the spindle are formed of a non-magnetic metal material,
The thimble part is
An inner sleeve having a slit along the axis and fixedly provided on the other end side of the main body frame;
An outer sleeve that is externally fitted in a circumferentially rotatable manner with respect to the inner sleeve, and that has a spiral groove on the inner peripheral surface,
An engagement pin fixedly provided on the spindle is engaged with the spiral groove through the slit. The digital micrometer according to claim 1, wherein
The main body frame is formed of austenitic stainless steel, pure aluminum or a nonmagnetic aluminum alloy,
The spindle is formed of austenitic stainless steel. A digital micrometer. The digital micrometer according to claim 1 or 2,
A digital micrometer, wherein the anvil and the contact are formed of ceramic. The digital micrometer according to any one of claims 1 to 3,
On the other end side of the main body frame, a guide bush for bearing the spindle is provided on the side close to the anvil,
The digital micrometer, wherein the guide bush is made of brass. The digital micrometer according to any one of claims 1 to 4,
The digital micrometer, wherein the inner sleeve is made of brass, pure aluminum, nonmagnetic aluminum alloy, or austenitic stainless steel. The digital micrometer according to any one of claims 1 to 5,
The digital encoder is characterized in that the encoder is a capacitance encoder, a photoelectric encoder, an electromagnetic induction encoder, or a magnetic encoder. The digital micrometer according to any one of claims 1 to 6,
The main body frame is formed of austenitic stainless steel,
The spindle is made of austenitic stainless steel,
The inner sleeve is made of brass,
The digital encoder is characterized in that the encoder is a capacitive encoder.