GB2193539A - Spindle unit - Google Patents

Abstract

A spindle unit for video cassette tape recorders or disc driving devices. Comprises a bearing unit (A) made up of a shaft (1) having a pair of axially spaced semicircular cross- section grooves (1a) functioning as inner ball races, outer races (2a, 2b) respectively provided around the outer peripheries of the grooves (1a, 1b) on the shaft and having similarly shaped inwardly facing grooves, and balls (3A, 3B) provided between each groove on the outer race and the groove on the above mentioned shaft. This bearing unit is fixed within a bearing housing 6 to form a spindle unit. Alternatively the bearing unit A may be fitted into a cylindrical sleeve (8 Fig. 2) which in turn is fitted into the bearing housing (6) to form the spindle unit. <IMAGE>

Description

SPECIFICATION Spindle unit Such rotary structure as a spindle unit used for a video cassette tape recorder or disc driving device has been conventionally formed as shown in Figs. 3 and 4(a) and (b).

That is to say, in the spindle unit shown in Fig. 3, a pair of radial ball bearings 30A and 30B are arranged in the upper and lower parts of a bearing housing 60 and a shaft 10 to which a pulley 70 is fixed in advance is inserted through the holes of the inner diameters of the above mentioned radial ball bearings 30A and 30B and is fixed while adjusting the backlash of the bearing part with a fixing sleeve 50.

In this spindle unit, in order to satisfy the precision against the deflection when the pulley 70 rotates, the parts of fitting the radial ball bearings 30A and 30B, shaft 10 and bearing housing 60 can not help being made high in the precision. As a result, the productivity is low, the assembling steps are many and the cost is high.

The spindle unit shown in Fig. 4(a) is formed as follows. First of all, as shown in Fig. 4(b), outer races 300A and 300B are arranged in the upper and lower parts of a shaft 100, so-called inner races of radial ball bearings are eliminated, ball rolling surfaces are formed on the shaft 100 and a spring 500 is arranged between the outer races 300A and 300B to form a bearing unit A' of a fixed pressure applied type (utilizing the fixed pressure of the spring). The spindle unit is assembled as in Fig. 4(a) by using the bearing unit A'. By the way, in Fig. 4(a), the reference numeral 700 represents a pulley fitted to the shaft 100 and 600 represents a bearing housing.

In this assembly, as the bearing unit A' is of the.fixed pressure applied type, the outer races 300A and 300B are both cemented and fixed or, as in most cases, one of the outer races is pressed in and the other is cemented.

Therefore, a hole 800 through which a cement is to be poured in is made in the bearing housing 600.

In the case of this prior art example, as compared with the prior art example shown in Fig. 3, there are defects that, as the bearing unit A' is of the fixed pressure applied type using the spring 500, the component parts are more and the precision is made so higher in advance that the cost is higher.

Therefore, in order to improve these prior art problems, rotary structures having various advantages have been already filed in Japan by the present applicant as Japanese utility model applications Nos. 162972/1985 and 57328/1986.

However, in these applications, a tapered surface (See Fig. 5(a)) or a curved surface (See Fig. 5(b)) is formed in a part of an outer race, the shape of the outer race is special and therefore an equipment exclusively for its production is required.

The present invention is suggested to solve the above mentioned defects.

An object of the present invention is to provide a spindle unit wherein the bearing unit is of a fixed position pressure applied type (fixed under a fixed pressure in a fixed position), the number of the component parts is reduced and the cost increase is inhibited.

Another object of the invention is to provide a spindle unit wherein an outer race used for already mass-produced conventional radial ball bearings can be used, therefore the production is easy and the cost is reduced.

Brief Description of the Drawings: Fig. 1(a) is a schematic vertically sectioned view of the first embodiment of the present invention.

Fig. 1(b) shows a bearing unit used in the first embodiment.

Fig. 1 (c) is a schematic vertically sectioned view of a spindle unit fitted with a pulley.

Fig. 2(a) is a schematic vertically sectioned view of the second embodiment of the present invention.

Fig. 2(b) is an explanatory view in the course of the assembly.

Fig. 3 is a schematic vertically sectioned view of a prior art example.

Figs. 4(a) and (b) are of another prior art example.

Figs. 5(a) and (b) are explanatory views showing improvements in the prior art examples already filed in Japan by the present applicant.

Fig. 1 (a) shows the first embodiment of the present invention. In this embodiment, a bearing housing 6 is provided outside a shaft 1, a bearing unit A is provided between the shaft 1 and bearing housing 6 and the shaft 1 is formed to be rotatable with respect to the bearing housing 6.

Fig. 1(b) shows the above mentioned bearing unit A. This bearing unit A is formed to include the shaft 1. Grooves 1 a of a semicircular cross-section for receiving balls 3 are formed as separated from each other by cutting or grinding over the entire periphery in the upper and lower parts of the outer peripheral part of the shaft. Outer races 2A and 2B are provided around the peripheries of the respective grooves 1a. Froper numbers of balls 3A and 3B are provided respectively between the outer races 2A and 2B and the grooves 1a of the shaft 1. The balls 3A are held by a retainer 4A and the balls 3B are held by a retainer 4B. By the way, grooves of the same semicircular cross-section as of the grooves 1a are formed on the respective inner peripheral surfaces of the outer races 2A and 2B.

The balls 3A and 3B held respectively by the retainers 4A and 4B as described above are provided respectively between these grooves and the grooves 1 a formed on the outer peripheral surface of the shaft. Seals 5A and 5B preventing dust from entering the ball parts are provided on both sides of the respective balls 3A and 3B.

The outer races 2A and 2B used in this embodiment may be those used conventionally. Therefore, an already existing outer race producing equipment can be utilized and the cost increase of the spindle unit of this embodiment can be prevented.

This bearing unit A in which the inner race of the conventional radial ball bearing is replaced with the shaft 1 is assembled substantially the same as in the conventional radial ball bearing.

Now, an example of assembling the spindle uni shown in Fig. 1(a) by using the bearing unit A assembled as mentioned above shall be explained in the following.

The bearing unit A is inserted into the bearing housing 6, any pressure is applied to the two outer races from outside and the outer races are fixed to the bearing housing 6 with a cement or one outer race is first pressed into the bearing housing 6 so as to be fixed and then the other outer race is pressed under any pressure and is fixed with a cement. The cement is not particularly illustrated but is poured in through a cement pouring hole formed in the bearing housing. Thus, a fixed position pressure applied type spindle unit can be assembled. This spindle unit is light and small and is therefore used as a spindle unit for video cassette tape recorders and disc driving devices.

In fitting a pulley 7 to the bearing unit in Fig. 1(a), the pulley 7is pressed down with the shaft borne on the lower end surface or is pressed down by using a predetermined jig.

Thus a spindle unit shown in Fig. 1(c) is formed.

Fig. 2(a) is of the second embodiment of the present invention. In this embodiment, the confirmation of the precision of assembling the spindle unit provided with the pulley 7 as shown in Fig. 1(c) is improved.

In the spindle unit shown in Fig. 1(c), the upper and lower ball bearing parts can rotate respectively independently. In order to confirm the performance as of a spindle unit, the shaft 1 must be rotatable in the state of Fig. 1(c).

In the spindle unit shown in Fig. 1(c), the bearing housing 6 is precisely worked, another part is fitted, the price is generally high and therefore, in case the performance as of a spindle unit does not satisfy a required performance, a great loss will be caused.

Therefore, as shown in Fig. 2(b), a cylindrical outer bearing 8 is incorporated in the bearing unit A shown in Fig. 1(b), this assembly is assumed to be a spindle unit, the outer bearing 8 is fixed, the shaft 1 is made rotatable, the performance confirmation is made easy and the total cost is reduced.

This assembly is assembled as follows: The bearing unit in Fig. 1 (b) is inserted into the outer bearing 8, has any pressure applied from outside the outer races and is then fixed with a cement or one outer race is first pressed into the outer bearing 8 so as to be fixed and then the other outer race has any pressure applied from outside and is then fixed with a cement.

The performance is confirmed as follows: The outer bearing 8 is fixed with a V-block or the like and the terminal of a measuring instrument is set in any position of the outer bearing 8 to measure the deflection, precision and rotation noise.

When a desired performance is obtained, this assembly is fitted within the bearing housing 6 or, as requird, the pulley 7 is fitted to the shaft 1.

That is to say, a spindle unit provided with the pulley 7 as shown in Fig. 2(a) is assembled by using the assembly in Fig. 2(b) as follows: The bearing unit A is pressed or cemented in the bearing housing 6 so as to be fixed and then the pulley 7 is pressed down or cemented with the shaft 1 borne on the lower end surface.

The embodiment of the present invention shown in Fig. 1(c) has the following merits as compared with the prior art shown in Fig. 3: (1) It is not necessary to use an outer race receiving seat or an intermediate sleeve and therefore the cost is low.

(2) The precision on the bearing housing is easy to detect.

(3) The bearing part is fixed under any applied pressure, is therefore not subjected to any unnecessary force in the later assembling or the like and therefore the once detected precesion of the bearing part is not affected.

It has the following merits as compared with the prior art shown in Fig. 4(a): (1) If a fixed pressure is applied by an intermediate spring, (a) in case one of the outer races is not fixed, the shaft deflection will be detected by the gap part and (b) in case both are fixed, the same as in the present invention, a pressure will be applied in a fixed position, a spring or the like will be useless and therefore there will be no waste.

The embodiment shown in Fig. 2(b) has the following merits as compared with the prior art shown in Fig. 4: That is to say, shown in Fig. 4 is a fixed pressure applied spindle. On the other hand, the one shown in Fig. 2(b) is of a fixed position pressure applied type and is advantageous to a high precision rotor for VCR's and disc driving units. Therefore, (1) the number of the component parts is low, the assembling is easy and the cost is low and (2) the assembly is simple and the precision is easy to obtain.

As in the above, in the spindle unit of the present invention, the rotating mechanism of the outer race parts holding the balls is fixed under a pressure in a fixed position and requires no such pressure applying member as a spring. Therefore, there are advantages that the spindle unit has few component parts, is simple to assemble and is small and light.

This spindle unit is used as a spindle unit for video cassette tape recorders and disc driving devices.

Also, as the shape of the outer race is the same as of the conventional radial ball bearing, the existing production equipment can be used as it is.

Claims (3)

1. A spindle unlt for video cassette tape recorders or disc driving devices characterized in that a bearing unit is assembled of a shaft having a pair of grooves of a semicircular cross-section functioning as ball rolling surfaces formed as separated from each other on the outer peripheral part, outer races respectively provided around the outer peripheries of the grooves on the shaft and having the same grooves as ths grooves on the shaft formed on the inner peripheral surfaces and balls provided between the groove on the outer race and the groove on the above mentioned shaft and the outer races of said bearing unit are fixed by a fixed position pressure application in predetermined positions within a bearing housing to form a spindle unit.

2. A spindle unit for video cassette tape recorders or disc driving devices characterized in that a bearing unit is assembled of a shaft having a pair of grooves of a semicircular cross-section functioning as ball rolling surfaces formed as separated from each other on the outer peripheral part, outer races respectively provided around the outer peripheries of the grooves on the shaft and having the same grooves as the grooves on the shaft formed on the inner peripheral surfaces and balls provided between the groove on the outer race and the groove on the above mentioned shaft, said bearing unit is fixed by a fixed position pressure application within a substantially cylindrical outer bearing for confirming the precision and, in case the performance is as desired, said assembly is fixed in a predetermined position within the bearing housing to form a spindle unit.

3. A spindle unit substantially as herein described with reference to and of Figures 1, 2 or 5 of the accompanying drawings.