JP2000105130A - Potentiometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a potentiometer capable of achieving stable performance for a long period by effectively suppressing the axial displacement of a shaft. SOLUTION: One axial end face 5a of a bearing 5 and a brush stand 7 are opposed near at hand capable of being brought into contact with one another, and the other axial end face 5b of the bearing 5 and a radial face 6d provided on an outer end of an inserting part 62 of a shaft 6 are opposed near at hand capable of being brought into contact with one another. Thus, since the axial displacement of the shaft 6 (brush stand 7) can be suppressed to a small value, the electric resistance value of a contact of resistance tracks 3, 4 and a brush 8 is stabilized and early wears of the tracks 3, 4 are prevented. Since the increase in the rotary torque of the shaft 6 is suppressed, operability of a displacement input to be measured is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type potentiometer used as a displacement detecting means such as a clutch sensor and a vehicle height sensor in an automobile.

[0002]

2. Description of the Related Art As a kind of a contact type potentiometer, for example, a type shown in FIG. 5 has been conventionally known. This potentiometer is comprised of a disk-shaped substrate 102 made of an insulator,
02, a substantially C-shaped resistance track 103 on the outer periphery and an annular resistance track 10 on the inner periphery formed concentrically on the surface
4 and a cylindrical bearing holding portion 101a that is arranged concentrically with the substrate 102 and formed on the body 101.
Shaft 1 rotatably supported by a bearing 105 via a bearing 105
06, and a leaf spring-like brush 108 fixed to a brush stand 107 attached to the shaft 106 and integrally formed of one conductive metal plate.
08 is in contact with the surfaces of the resistance tracks 103 and 104 with an appropriate load.

That is, in this type of potentiometer, resistance tracks 103 and 104 formed on a substrate 102 are
It is electrically connected via a brush 108 moved around its axis by a shaft 106, and the contact position of the brush 108 is variable. Therefore, when the shaft 106 rotates by a rotation angle corresponding to a physical quantity input from the outside, such as displacement or inclination of the measurement target,
Along with this, the contact position of the brush 108 with respect to the resistance tracks 103 and 104 moves in the circumferential direction and the electric resistance changes, so that a voltage corresponding to the physical quantity is output.

A gap δ1 of, for example, about 0.6 mm is set in the axial direction between the end wall of the bearing holding portion 101a of the body 101 and the brush stand 107 to allow the shaft 106 to rotate smoothly. . Also, in this case, when the vibration in the axial direction is input, the shaft 106 is greatly vibrated and displaced in the axial direction due to the existence of the gap δ1, and the contact area of the shaft changes due to a change in the contact pressure of the brush 108 against the resistance tracks 103 and 104. Therefore, the electric resistance value (contact resistance) at the contact point becomes unstable, and the resistance track 1
In order to prevent this from adversely affecting the linearity of the output voltage with respect to the relative rotation angle of the brushes 108 and 03, 104, in order to prevent this, the distance between the end wall of the bearing holding portion 101a and the brush stand 107 is reduced. A ring spring 109 is interposed.

[0005]

In the potentiometer according to the prior art, it is effective to increase the set load of the ring spring 109 in order to improve the suppressing force (vibration resistance) against the axial vibration displacement of the shaft 106. is there. However, in this case, the rotational torque of the shaft 106 increases due to an increase in the contact load between the brush stand 107 and the ring spring 109 and between the bearing 105 and the shaft radial surface 106a, and the operability decreases. In addition, by increasing the set load, the contact seat surface between the ring spring 109 and the end wall of the bearing holding portion 101a and the brush stand 107, the abrasion of the shaft radial surface 106a, the set of the ring spring 109, etc. May occur. Therefore, the vibration resistance achievable by the set load of the ring spring 109 is up to about 10 G of vibration acceleration, and the output is not obtained under the condition of receiving vibration acceleration of 10 G or more, such as around an automobile engine. There is a risk of becoming unstable or causing early wear of the resistance tracks 103 and 104.

In order to suppress the axial vibration displacement of the shaft 106, a thrust washer is interposed between the end wall of the bearing holding portion 101 a of the body 101 and the brush stand 107 instead of the ring spring 109. , Body 10
It is also effective to make the gap δ1 as small as possible by processing the shaft 106, the shaft 10, and the thrust washer with high precision. However, actually, since the processing tolerances of the members such as the body 101, the shaft 106, the shaft 10, and the thrust washer are accumulated, the dispersion of the gap δ1 becomes large, and it is technically necessary to reduce the gap δ1 reliably and sufficiently. Was difficult.

[0007] The present invention has been made under the above circumstances, and the technical problem thereof is to effectively suppress axial displacement of a shaft and exhibit stable performance for a long period of time. To provide a potentiometer that can be used.

[0008]

Means for Solving the Problems The technical problems described above are:
This can be effectively solved by the present invention. That is, the potentiometer according to the present invention includes a substrate having a surface on which a resistance track extending in a circumferential direction is formed, a shaft disposed concentrically with the resistance track and rotatably supported by a bearing, and mounted on the shaft. A brush made of a conductive metal fixed to a brush base and having a tip contacted with the resistance track, and an outer end surface of the bearing and a radial surface provided at an outer end of an insertion portion of the shaft into the bearing. Are in contact with each other, and the inner end face of the bearing and the brush base are directly opposed to each other in a state of being close to each other.

The potentiometer having the above-mentioned configuration basically has a brush fixed to a brush base rotated together with the shaft by rotating the shaft in response to the input of a physical quantity to be measured, similarly to the conventional one. The position of the contact point with the resistance track moves in the circumferential direction to change the electric resistance value, thereby outputting a voltage corresponding to the physical quantity. The axial displacement of the shaft at this time is
It is restricted within the range of the gap between the brush base and the inner end face of the bearing. The clearance is determined only by the axial distance from the radial surface of the shaft abutting on the outer end surface of the bearing to the brush stand, in other words, only by the axial size of the insertion portion of the shaft into the bearing and the axial size of the bearing. According to the processing accuracy of the two parts of the bearing and the shaft, the bearing can be made as small as 0.16 mm or less, and the axial displacement of the shaft due to vibration input or the like can be effectively suppressed.

According to the present invention, the radial surface of the outer end of the insertion portion of the shaft does not always contact the outer end surface of the bearing with the contact load of a spring or the like as in the prior art. When the opposed gap between the inner end surface of the bearing and the brush base becomes zero due to the axial displacement, the brush base comes into sliding contact with the inner end surface of the bearing, so that the rotational torque of the shaft increases. Can be kept small. Therefore, in this case, for example, it is more preferable that the brush stand is made of a low friction material having excellent wear resistance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a potentiometer according to the present invention will be described in more detail with reference to a preferred embodiment shown in FIGS. First, reference numeral 1 in FIG. 1 denotes a body fixed to a predetermined portion of the device. The body 1 includes an outer shell 11 forming a cylindrical working chamber S on an inner periphery thereof, and an outer shell 11 And a cylindrical bearing holding portion 12 axially extending from the inner diameter portion of the bottom wall 11a into the working chamber S.

On the inner periphery of the outer shell 11 of the body 1,
A disk-shaped substrate 2 made of a synthetic resin material having an excellent electrical insulation property such as phenol resin is provided with a working chamber S on the inner periphery of the outer shell 11.
Further, the outside of the substrate 2 is covered with a potting material 13 made of epoxy resin or the like formed on the inner periphery of the opening end 11b on the opposite side of the bottom wall 11a of the outer shell 11 from the bottom wall 11a. Completely sealed. Therefore, intrusion of dust and the like into the working chamber S from the outside is reliably blocked.

As shown in FIG. 2, on the surface of the substrate 2 on the side of the working chamber S, an outer peripheral resistance track 3 extending substantially in a C-shape in the circumferential direction and an annular resistance track 4 extending on the inner peripheral side thereof are formed. Have been. The resistance track 3 on the outer periphery is made of a resistance material obtained by adding a thermosetting resin paste to a conductive material powder such as carbon having a large electric resistance, and the resistance track 4 on the inner periphery is formed of a thermosetting resin powder such as silver. It is made of a conductive material to which a resin paste is added, and is formed to an appropriate thickness (for example, 10 to 12 μm) by a method such as printing. Terminals 3a and 3b are provided at both ends of the resistance track 3.
However, the resistance track 4 is provided with a terminal 4a.

A cylindrical bearing (sliding bearing) made of a sintered alloy or the like is provided on the inner periphery of the bearing holding portion 12 formed on the body 1.
5, the axial end faces 5a, 5b are connected to the bearing holder 1
The bearing 5 is mounted on the bearing 5 so that the shaft 6 is connected to the resistance tracks 3, 4.
It is inserted concentrically and rotatably. The outer end of the shaft 6 extending to the outside of the body 1 is connected to a member to be measured (not shown) via an appropriate link member or the like, that is, the shaft 6 moves linearly of the member to be measured. Alternatively, it is adapted to be rotated in response to inclination or the like.

An inner end portion 61 of the shaft 6 projects from the bearing 5 into the working chamber S and is in close proximity to the substrate 2, and has an outer periphery formed between the shaft 6 and an insertion portion 62 of the shaft 6 into the bearing 5. The brush base 7 is mounted in a state where the brush base 7 is positioned by the mounted mounting seat surface 63. This brush stand 7
Is made of a synthetic resin material such as polyacetal which is a low-friction material having excellent wear resistance and an insulating property. Relative rotation with respect to the shaft 6 is prevented by a suitable detent means (not shown). That is, it is configured to rotate integrally with the shaft 6.

Insertion portion 62 of shaft 6 into bearing 5
Has a radial surface 6 which abuts against an outer end surface 5b of the bearing 5.
4 is formed, whereby the axial displacement of the shaft 6 toward the substrate 2 is restricted. For this reason, the shaft 6 is rotated while maintaining a predetermined distance or more with respect to the surface 2 a of the substrate 2, in other words, the resistance tracks 3 and 4. The inner end surface 5a of the bearing 5 is
The brush 6 is directly opposed to the surface of the brush stand 7 facing the opposite side to the substrate 2, thereby restricting the axial displacement of the shaft 6 toward the opposite side to the substrate 2.

A brush 8 made of, for example, an AgPd-based conductive metal plate is attached to a surface of the brush stand 7 facing the substrate 2. The brush 8 is formed with a pair of multi-contact sliding portions 81 and 82 each of which has a tip divided into a comb-like shape, and is elastically contacted with the surfaces of the resistance tracks 3 and 4 with an appropriate load. I have. The contact load of the multi-contact sliding portions 81 and 82 on the resistance tracks 3 and 4 is set to, for example, about 17.5 g.

That is, this potentiometer is operated by inputting a displacement amount such as an inclination angle or a stroke amount.
When the shaft 6 is relatively rotated with respect to the body 1, the brush stand 7 fixed to the shaft 6 rotates around the axis of the shaft 6. Therefore, the contact positions of the brush 8 attached to the brush stand 7 with the resistance tracks 3 and 4 by the multiple contact sliding portions 81 and 82 continuously change,
Since the resistance value changes as the length of the conductive path in the resistance track 3 changes, a voltage corresponding to the input measurement target amount such as the inclination angle or the stroke amount is output.

As described above, the axial displacement of the shaft 6 toward the substrate 2 is controlled by the radial surface 64 and the bearing 5.
The axial displacement of the shaft 6 toward the side opposite to the substrate 2 is restricted by the contact with the outer end face 5 b of the bearing 5, and the brush base 7 fixed to the inner end 61 and the inner end face 5 of the bearing 5.
Therefore, even if an axial vibration is given, the amount of axial displacement of the shaft 6 is limited by the state where the radial surface 64 and the outer end surface 5b of the bearing 5 are in contact with each other. The gap δ between the inner end surface 5a of the bearing 5 and the brush base 7 is suppressed to the range of δ. According to the configuration of this embodiment, the gap δ is formed between the mounting seat surface 63 of the shaft 6 and the radial surface 64.
By improving the axial dimensional accuracy of the intermediate portion (the insertion portion 62) and the axial dimensional accuracy of the bearing 5, the value can be set to a value (0.16 mm or less) significantly smaller than that of the related art. Therefore, the change in the distance between the brush stand 7 and the substrate 2 is as small as 0.16 mm or less, and the multi-contact sliding portions 81 and 82 of the brush 8 with respect to the resistance tracks 3 and 4 are provided.
The change in the resistance value due to the change in the contact load is suppressed, and a stable output is obtained.

The radial surface 64 of the shaft 6 is not pressed against the outer end surface 5b of the bearing 5 by a conventional ring spring or the like, and even if the shaft 6 is displaced to the opposite side to the substrate 2. The brush base 7 comes into contact with the inner end face 5a of the bearing 5, and the brush base 7 is made of polyacetal or the like having excellent wear resistance and low friction as described above. For this reason, the rotation torque of the shaft 6 does not increase, so that good operability with respect to the displacement input of the measurement target can be exhibited.

Further, as described above, the interposition of the ring spring in the prior art becomes unnecessary, and the gap δ can be obtained only by the axial dimensional accuracy of the two parts of the insertion part 62 of the shaft 6 and the bearing 5.
Can be set to a remarkably small value of 0.16 mm or less, and the shape of the bearing holding portion 12 in the body 1 is a simple cylindrical shape, which is simplified as compared with the related art, thereby facilitating manufacture. be able to.

Next, the results of a vibration resistance evaluation test of the potentiometer having the above configuration will be described. In this test, the gaps δ between the inner end surface 5a of the bearing 5 and the opposing surface of the brush stand 7 in a state where the radial surface 64 of the shaft 6 and the outer end surface 5b of the bearing 5 are in contact with each other have different sizes. With respect to the set potentiometer, an axial vibration displacement was applied to the shaft 6 under the following conditions, and the wear of the resistance track and the stability of the resistance change were evaluated. [Test conditions] Acceleration: 20 G Frequency: 50 to 250 Hz Test time: 180 hrs. Spring load of brush on resistance track ... 17.5g

FIG. 3 shows the evaluation results of this test. In addition, in FIG.
When the wear of the resistance track 3 did not reach the substrate surface within the test time (180 hours), the result was evaluated as ○.時間 indicates that the linearity of the output voltage characteristics was not impaired within a period of time, and × indicates that the linearity of the output voltage characteristics was deteriorated to a level at which the linearity was impaired. As is clear from the evaluation results, δ = 0.1 mm, δ =
In the test samples with 0.15 mm and δ = 0.16 mm, the wear of the resistance track was small and the resistance change was stable, whereas in the test sample with δ = 0.2 mm, the wear of the resistance track was remarkable. It was large and the resistance change was unstable.

FIG. 4 shows the cross-sectional shape of the resistance track 3 at a magnification of 20 times in the X direction and 1000 times in the Y direction. That is, in this figure,
(A) is the cross-sectional shape of the resistance track 3 before the start of the test, (B) is the cross-sectional shape of the resistance track 3 after performing the above test on a test sample with δ = 0.1 mm,
(C) shows the cross-sectional shape of the resistance track 3 after performing the above test on a test sample with δ = 0.2 mm. (B) As is clear from the comparison of (C),
The test sample with δ = 0.1 mm has less wear and δ =
In the test sample of 0.2 mm, it can be seen that large wear reaching the surface level of the substrate 2 occurred in the portion where the resistance track 3 was in sliding contact with the multi-contact sliding portion of the brush.

That is, as is apparent from the above test results, the clearance δ between the inner end face 5a of the bearing 5 and the brush base 7 in a state where the radial face 64 of the shaft 6 and the outer end face 5b of the bearing 5 are in contact with each other is determined. When the thickness is 0.16 mm or less, excellent vibration resistance is exhibited even under use conditions in which an axial vibration with an acceleration of 20 G is given, and the output is stabilized for a long period of time.

[0026]

According to the potentiometer according to the present invention, the axial displacement of the shaft is suppressed to a small value, so that the state of the electric resistance at the contact point between the resistance track and the brush is maintained even when the axial vibration displacement is applied. In addition, premature wear of the contact portion between the resistance track and the brush can be effectively prevented. For this reason, a stable output is obtained, and early deterioration of the linearity of the output due to wear is also prevented.In addition, since an increase in the rotational torque of the shaft is suppressed to a small degree, the operability with respect to the displacement input of the measurement object is good, The reliability of the output value can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a preferred embodiment of a potentiometer according to the present invention by cutting along a plane passing through an axis thereof.

FIG. 2 is a plan view showing a part of the embodiment.

FIG. 3 is an explanatory diagram showing the results of evaluating the wear of the resistance track and the stability of the resistance value in the vibration resistance evaluation test of the potentiometer of the present invention.

FIG. 4 is an explanatory diagram showing a cross-sectional shape of a resistance track before and after the vibration resistance evaluation test.

FIG. 5 is a schematic sectional view showing a typical conventional example of a potentiometer cut along a plane passing through the axis thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body 11 Outer shell part 11a Bottom wall 11b Open end part 12 Bearing holding part 13 Potting material 2 Substrate 3, 4 Resistance track 5 Bearing 5a, 5b End face 6 Shaft 61 Inner end part 62 Insertion part 63 Mounting seat surface 64 Radial surface 7 Brush stand 8 Brush 81, 82 Multi-contact sliding part S Working chamber

Claims (1)

[Claims] 1. A substrate (2) having a circumferentially extending resistance track (3, 4) formed on a surface thereof, and a concentric arrangement with the resistance track (3, 4) and a bearing (5). A shaft (6) rotatably supported, and a brush (8) made of a conductive metal fixed to a brush stand (7) attached to the shaft (6) and having a tip contacting the resistance track (3, 4). ), And an outer end surface (5b) of the bearing (5) and the shaft (6).
The radial surfaces (64) provided on the outer end of the insertion portion (62) into the bearing (5) abut against each other, and the inner end surface (5a) of the bearing (5) and the brush stand (7).
Are directly opposed to each other in the vicinity of each other.