JPH0361128B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a bearing structure for supporting a rotary drive shaft used in an instrument having a rotating part.

2. Description of the Related Art Instruments having rotating parts, such as tachometers and speedometers for automobiles, are widely used in various industrial fields. When plain bearings are used in such instruments, the rotating bearing structure is the same as general bearing structures, with bushings made of oil-less metal interposed to reduce friction and improve durability. However, in usage environments where the bearing pressure is very low, such as in instruments, such conventional bearing structures are not necessarily optimal.

The present invention provides that the shaft neck of the bearing structure is divided into a plurality of parts in the circumferential direction and has supported surfaces parallel to the drive axis, and the bearing has a plurality of spiral bearing surfaces. Accordingly, it is an object of the present invention to provide a bearing structure that can reduce costs by omitting bushing, reduce heat generation in the bearing part, and prevent rattling of the bearing part. In addition, when the shaft neck is made of synthetic resin, the shape of the drive cable accommodating portion inside the shaft neck and the shape of the outer surface of the bearing can be formed appropriately to make molding of the resin easier and more precise. By optimizing the rotation direction of the spiral groove provided on the surface, it also has the effect of preventing oil from rising.

An embodiment in which the bearing structure of the present invention is applied to a tachometer will be described below with reference to the drawings.

In the tachometer shown in FIG. 1, the drive shaft 4 has its shaft neck portion 4a supported in the radial direction by a bearing portion 1a of the body 1, and is also supported in the axial direction by a yoke 3 made of a magnetic metal plate. A permanent magnet 5 is also attached. The pointer shaft 7 is rotatably supported by a bearing part of the body 2, and its end is supported by fitting into a hole provided at the center of the drive shaft.The pointer shaft 7 is supported by a hairspring 9 fixed to the yoke 3 It is adapted to receive a restoring torque according to the rotation angle of the shaft 7, and an inductor 8 facing the magnet 5 is attached.

Now, the drive shaft 4 is connected by a drive cable (not shown) inserted into the center hole 4b of the drive shaft 4.
When the inductor 8 is rotated, an eddy current is generated in the inductor 8 by the magnet 5 which is mounted on the drive shaft 4 and rotates together with the inductor 8, giving a rotating torque to the inductor 8. This torque rotates the pointer shaft 7 to a position where this torque and the restoring force of the hairspring 9 are balanced. The rotational torque generated by the eddy current is approximately proportional to the rotational speed of the drive shaft, and the rotational torque and the rotation angle of the pointer shaft are also approximately proportional in accordance with the characteristics of the hairspring. No needle will display the rotation speed on the instrument panel.

A feature of the present invention lies in the shape of the sliding surface between the shaft neck portion 4a of the drive shaft 4 and the bearing portion 1a of the body 1, which is illustrated in FIGS. 2 and 3. As shown in FIG. 2, the shaft neck portion 4a has four surfaces 4d formed in parallel to each side of a hole 4b having a rectangular cross section, and serve as non-contact surfaces during rotation. That is, the thin divided cylindrical surface 4c, which is divided into four parts in the circumferential direction and extends in the direction of the drive shaft, serves as a slidingly supported surface. Further, as shown in FIG. 3, four spiral grooves 1d are provided on the bearing surface, and four spirally elongated surfaces 1c form sliding bearing surfaces. The spiral is the drive shaft 4
The direction of rotation is the same as that of the instrument, and is designed to prevent oil from entering the inside of the instrument.

In the above-described embodiment, the bearing part 1a is made integrally with the body 1, but the bearing part 13 may be made separately from the body 12 and then combined as shown in FIG. Also, as shown in Figure 4, the first
The bushing 14, which is not used in the illustrated embodiment, may be press-fitted into the shaft neck, and the above-mentioned sliding surface shape may be formed on the outer surface of the bushing.

〔Effect of the invention〕

The bearing structure as described above has the following advantages.

(1) Heat generation is prevented by reducing the contact area of the sliding surfaces, and heat dissipation is improved through air flowing through the non-contact surface 4d of the shaft neck of the drive shaft and the groove 1d provided in the bearing section. By doing so, the sliding shaft can be supported without bushing.

(2) By making the direction of the spiral groove 1d provided on the bearing surface the same as the rotational direction of the drive shaft, oil is prevented from entering the inside of the instrument.

(3) By spirally twisting the bearing surface of the bearing part, smooth bearing without play is achieved despite the non-contact recesses provided on both the shaft and neck bearing parts.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a tachometer having the bearing structure of the present invention, Figs. 2a and 2b are a side view and a bottom view of the shaft neck, respectively, and Figs. 3a and 3b are longitudinal cross-sections of the bearing portion, respectively. The figure, the bottom view, and FIG. 4 are longitudinal sectional views of a tachometer showing another embodiment of the present invention. In the figure, 4... drive shaft, 1a... bearing part,
4a...Shaft neck, 1c, 4c...Sliding surfaces.

Claims (1)

[Scope of Claims] 1. In a bearing structure that is used in an instrument having a rotating part and supports a rotary drive shaft, a shaft neck 4a of the drive shaft is divided into a plurality of parts in the circumferential direction and parallel to the drive axis. The bearing 1a has an arc-shaped supported surface 4c and a non-contact surface 4d, and the bearing 1a is in contact with the bearing surface of the shaft neck of the drive shaft and is rotated from the insertion side of the drive shaft in the same direction as the rotation direction of the shaft. A bearing structure characterized by having a plurality of spiral bearing surfaces 1c formed in a direction.