JPH04117924U - precision shaft - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the lubricity of sliding bearings and precision shafts,
Prevents seizure due to rotational friction and extends service life. [Configuration] At least the outer surface of the precision shaft that contacts the bearing has a diameter of 2 to 100 μm and a depth of 0.5 to 3 μm.
A plurality of substantially circular dimples are formed.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is a capstansha used for feeding magnetic tape in ATR, VTR, etc. This relates to precision shafts used as rotational axes for shafts, spindle shafts, etc. The invention relates specifically to improvements in precision shafts for use with plain bearings.

0002

[Conventional technology]

Traditionally, rolling bearings have been used as bearings for this type of precision shaft. Recently, sliding bearings have been increasingly used to reduce weight and compactness. I came. However, when using a sliding bearing, there is surface contact between the shaft and the bearing. However, even if lubricating oil is injected between the two, the problem is that the oil runs out early and seizes up. was. In order to solve this problem, various self-lubricating bearings have been proposed. . For example, Japanese Patent Application Laid-Open No. 60-96702 describes the use of sintered oil-impregnated bearings. Furthermore, Japanese Patent Application Laid-open No. 62-80242 discloses a copper-based sintered oil-impregnated thrust shaft as shown in FIG. It is disclosed that the shaft 5 is rotated using the receivers 4, 4, respectively.

0003

[Problem that the idea aims to solve]

However, even when using the oil-impregnated bearing 4 above, compared to when using a rolling bearing, If this occurs, rotational friction will cause seizure between the shaft and bearing, which will shorten the service life. The problem is that the length is extremely short.

0004 Therefore, in order to solve the above problem, the inventor of the present invention aimed to improve the service life of shafts and bearings. We are conducting intensive research to understand the cause of the shortening of the time, that is, the cause of burn-in between the two. As a result of repeated tests, it was discovered that there was a problem with the lubrication function between the shaft and bearing. vinegar In other words, an oil film is formed between the shaft and the bearing due to the supply of lubricating oil from the oil-impregnated bearing. However, since the oil film is very thin, it is easy for the shaft and bearing to come into contact and cause friction. This will shorten the service life.

[0005] Based on the above knowledge, the inventor of the present invention has devised a method to create a state in which it is difficult for the shaft and the bearing to come into contact with each other. Various attempts were made. An example of this is using a lubricating oil with a high viscosity to An attempt was made to form a film. In addition, the surface roughness of the shaft is finished to Rmax0.2μm or less. We attempted to prevent localized contact due to surface irregularities. However, in the former case, when the temperature of the lubricating oil increases due to the rotation of the shaft, , the service life will not be extended because the viscosity will decrease and the oil film will become thinner. Also, the latter However, considering productivity and cost, there are limits to reducing surface roughness and it is not practical. It's not useful.

[0006] This invention was developed in view of the above problems, and it is possible to prevent seizure of bearings due to rotational friction. The purpose of the present invention is to provide a precision shaft that can prevent damage and extend its service life.

[0007]

[Means to solve the problem]

This invention has a lubricating oil retention area on the outer peripheral surface of the shaft that comes into contact with the sliding bearing. This creates a thick oil film between the shaft and bearing, reducing contact between the two as much as possible. A roughly circular dimple is used as the lubricating oil retention area. It is something that In other words, this type of shaft generally has a grinding process in its circumferential direction. Because of the machining process, the surface condition of the shaft has multiple grooves in the circumferential direction. Therefore, since the rotation direction of the shaft is also circumferential, the lubricating oil flows inside the grooves. The oil will flow and a thick oil film will not form. Therefore, the grooves should be placed in the longitudinal direction of the shaft. If it is formed in the direction perpendicular to the direction of rotation, the lubricating oil will stay in the groove and a thick oil film will form. However, it is difficult to perform such processing on a circular shaft. be. Therefore, we decided to adopt approximately circular dimples. In other words, the precision system of this invention In precision shafts used with plain bearings, the shaft is at least in contact with the bearing. A plurality of approximately circular dimples are formed on the surface of the outer peripheral portion.

[0008] In the above configuration, in order to obtain a good oil film thickness, the size of the dimples must be It is preferable that the diameter d = 2 to 100 μm and the depth t = 0.5 to 3 μm, which improves productivity. From this point of view, d is preferably in the range of 5 to 30 μm and t is in the range of 1 to 2 μm.

[0009]

[Effect]

The precision shaft with the above configuration has grooves that correspond to the direction in which lubricating oil flows. The approximately circular dimples prevent directionality, and can be fitted into oil-impregnated bearings to create a system. When the shaft rotates, lubricating oil supplied from the oil-impregnated bearing stays inside the dimple. while moving around the inner periphery of the oil-impregnated bearing in the circumferential direction to form a good oil film. therefore , prevents contact between the shaft and bearing, preventing seizure due to friction and friction between the two due to wear. Shakiness is reduced.

0010

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. As shown in Figure 1, it is made of SUS420J2 obtained through the required grinding process. The fitting part 1 of the steel shaft with the bearing has a diameter d = 2 to 100 μm and a depth t = 0.5. A precision shaft 3 is formed by forming a plurality of approximately circular dimples 2 having a size of ~3 μm. Configure. Note that the dimples 2 occupy 10 to 50% of the surface area of the fitting part 1. It is preferable to form it so that

[0011] In the above embodiment, the substantially circular dimple 2 is the fitting part 1 of the shaft with the bearing. Although it is formed only on the shaft, it may be formed on the entire outer periphery of the shaft. However, magnetic tape In this case, the magnetic contact surface may not be suitable for the functionality of the device. It is preferable that the dimples 2 be formed on a portion other than the contact surface with the air tape.

0012 Note that the dimple 2 is formed by a dipping barrel or a roller having multiple small protrusions. It can be formed using means such as rolling.

[0013] Next, we conducted a comparative test on the service life of the conventional precision shaft and the precision shaft of this invention. Ta. In this test, as shown in Fig. 2, each shaft was attached to existing copper-based sintered oil-impregnated bearings 4 and 4. The shaft is rotated continuously at a constant circumferential speed of 5 m/min, and the motor is turned off. The fluctuation value of the current consumption was read, and the point at which it reached a certain predetermined value was determined as the service life limit. As a result, the precision shaft of this invention has a service life approximately 2 to 3 times longer than conventional shafts. Extended.

[0014]

[Effect of the idea]

The precision shaft of the present invention has multiple dimples in the contact area with the bearing. The shaft becomes a stagnation area for lubricating oil and forms a thick oil film between the bearings. This prevents contact with the bearing and prevents seizure due to friction and rattling between the two due to wear. can be significantly reduced. Therefore, the service life can be significantly extended, and uneven rotation of the shaft can be suppressed. This has great effects, such as improving the performance of devices such as ATR and VTR.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the precision shaft of the present invention,
(a) is a front view, and (b) is an enlarged view of the main parts.

FIG. 2 is a sectional view of a main part showing an example of a precision shaft in use.

[Explanation of symbols]

1 Fitting part 2 dimples 3.5 Precision shaft 4 Copper-based sintered oil-impregnated bearing

Claims (2)

[Scope of utility model registration request] 1. A precision shaft used with a sliding bearing, comprising a plurality of substantially circular dimples formed at least on the outer peripheral surface that contacts the bearing. [Claim 2] The size of the dimple is 2 to 100 μm in diameter.
2. The precision shaft according to claim 1, wherein the shaft has a depth of 0.5 to 3 μm.