JP2542909B2 - Bearing device and method of manufacturing bearing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bearing device installed in a rotary head device of a VTR (video tape recorder) or a DAT (digital audio tape recorder), and a method of manufacturing the bearing device.

[Prior Art] FIG. 6 is a half sectional view showing a bearing portion of a rotary head device mounted on a conventional 8 mm VTR or the like.

In this rotary head device, a shaft 4 is rotatably supported by bearings 2 and 3 provided at two upper and lower positions in the center of a fixed drum 1. These bearings 2 and 3 are the shaft 4
A plurality of balls 2a and 3a are arranged in the grooves 4a and 4b formed in the ball 2a and the ball 2a by the upper race 2b.
Is configured to be supported by the lower race 3b. A preload spring 5 is interposed between the upper race 2b and the lower race 3b to urge both races 2b and 3b in the outward direction (the directions in which they are separated from each other). The preload spring 5 is provided to apply a preload (thrust load) required to eliminate rattling in the thrust direction of the bearing to the balls 2a and 3a that are in contact with the grooves 4a and 4b. Is.

To assemble the bearings 2 and 3, firstly, the upper race 2b
The outer diameter of the lower race 3b is preliminarily tightly formed with respect to the inner diameter of the fixed drum 1, and the outer diameter of the lower race 3b is loosely formed with respect to the inner diameter of the fixed drum 1 in advance. After the balls 2a, 3a are arranged in the grooves 4a, 4b, the upper race 2b is press-fitted into the fixed drum 1 from above at a high temperature or a room temperature. Next, the lower race 3b is inserted from below. Then, the adhesive 6 is injected into the clearance between the lower race 3b and the fixed drum 1 through the hole 7 to be solidified. In this way, the bearings 2 and 3 are assembled.

As shown in FIG. 6, the bearing device that applies preloads to the balls 2a and 3a in directions away from each other is
It has advantages over bearing devices that apply preload to 3a in directions toward each other.

First, in the bearing device that applies preload to the balls 2a and 3a in the directions approaching each other, it is necessary to provide a race or other member having a shape capable of pressing the balls 2a and 3a inward on the axially outer sides of the balls 2a and 3a. As a result, the distance between the balls 2a and 3a becomes shorter than the dimension of the bearing device in the laying direction, and the supporting span of the shaft becomes shorter. On the other hand, in the case of preloading the balls 2a and 3a in directions away from each other, a member for preloading the balls 2a and 3a on the outer side in the laying direction becomes unnecessary,
The support span of the shaft by 2a and 3a can be lengthened.

In addition, when grease is used for the bearing device, the viscosity of the grease becomes high in a low temperature environment and the rotating load increases,
In the bearing device in which the balls 2a and 3a are preloaded to the outside, if the coefficient of thermal expansion of the fixed drum 1 which is the support side with respect to the shaft 4 is increased, the shaft 4 and the fixed drum in a low temperature environment are increased. Balls 2a and 3a due to the difference in heat shrinkage from
The preload applied to is reduced. As a result, the rotational load due to the preload is reduced, the increase in the rotational load due to the grease is offset, and it is possible to prevent the rotational load from becoming excessive.

[Problems to be Solved by the Invention]

However, the conventional bearing device shown in FIG. 6 has the following drawbacks.

(1) Since the preload spring 5 for applying a preload to the balls 2a and 3a in the outward direction is used, the number of parts constituting the bearing device increases accordingly. Also in the assembly work, the preload spring 5 is inserted into the inner peripheral portion of the fixed drum 1, and then the lower race 3b is inserted, which complicates the process.

(2) In the bearing device shown in FIG. 6, the upper race is attached to the inner peripheral surface of the fixed drum 1 which is a device in which the bearing device is used.
The outer peripheral surfaces of 2b and lower race 3b are the assembly standards. In order to apply preload to both races 2b and 3b by the preload spring 5, the upper race 2b should be tight against the inner diameter of the fixed drum 1 and the lower race 3b should be loose so that it is loose outside the races 2b and 3b. It is necessary to decide the diameter. Since the outer races of the upper race 2b and the lower race 3b having different processing dimensions are inserted into the inner diameter of the fixed drum 1 as a built-in reference, the shaft 4 tilts with respect to the axis of the fixed drum 1. Inevitable. Therefore, the shaft 4 and the reference surface 1a of the fixed drum 1 and the lead step 1b
In order to obtain mutual angle accuracy with the fixed race 1, it is necessary to fix the lower race 3b to the fixed drum 1 and then finish the reference surface 1a and the lead step 1b with the shaft 4 as a reference. Work becomes complicated.

(3) At the time of finishing the reference surface 1a of the fixed drum 1 and the like, the bearing portion is already assembled to the fixed drum 1. Therefore, when the fixed drum 1 is cut, cutting oil and chips are applied to the bearing portion. Inflow is considered, and to prevent it, it becomes necessary to shield or dry process. Furthermore, in the latter case of dry processing, it is necessary to take explosion-proof measures.

It is an object of the present invention to provide a bearing device that eliminates the need to provide a preload spring when preloading balls in directions away from each other, reduces the number of parts, and eliminates the complicated work of inserting the preload spring. There is.

Further, according to the present invention, when the bearing device is incorporated in a device such as a rotary head device, the center of the device and the shaft are unlikely to tilt at the time of incorporation, and post-processing on the device side can be eliminated. It is an object of the present invention to provide a bearing device having the above structure.

Further, the present invention, without using a preload spring,
An object of the present invention is to provide a method for manufacturing a bearing device, which can easily and surely perform a work of applying a preload in a direction in which balls are separated from each other.

[Means for solving the problem]

The bearing device of the present invention supports a shaft in which two grooves are formed on the outer periphery, a plurality of balls arranged in each groove, and these balls supported from the side facing each groove. Two outer races and a housing that holds the two outer races on the inner peripheral portion, and the two outer races are preloaded in a direction in which they are separated from each other by an external force. It is fixed to the inner peripheral portion of the housing, and the outer peripheral portion of the housing is a mounting surface for a device using the bearing.

In the above, it is preferable that the housing is made of a material having a coefficient of thermal expansion larger than that of the shaft.

Further, in the method of manufacturing the bearing device of the present invention, two grooves are formed on the outer periphery of the shaft, and the shaft is supported on the support side.
Two outer races are provided to support a plurality of balls arranged in the two grooves from the side facing each groove,
The outer race is attracted by a magnet to apply a preload to the outer race in a direction away from each other, and each outer race is fixed to the support side in the state where the preload is applied.

[Action]

In the bearing device of the present invention, the outer race provided on the inner peripheral portion of the housing is pre-loaded by an external force in a direction in which the outer races are separated from each other, and the outer race to which the pre-load is applied is attached to the inner peripheral portion of the housing. It is fixed.
Therefore, it is not necessary to incorporate a preload spring in the bearing device as in the conventional case, and the number of parts can be reduced and the assembling work can be simplified.

Further, in the bearing device of the present invention, balls are interposed between the groove of the shaft and the groove of the outer race, and the outer race is held on the inner peripheral portion of the housing. The outer peripheral portion of the housing serves as a mounting surface for a device that uses the bearing device. Therefore, when the shaft, the ball, the outer race, and the housing are assembled, for example, if the outer peripheral portion of the housing is finished by using the shaft as a reference, in the bearing device, the outer peripheral portion and the shaft that are the mounting reference are Concentricity can be secured. Therefore, if the bearing device is incorporated into a device such as a rotary drum device with the outer peripheral portion of the housing as a reference, the center of the device and the shaft can be prevented from tilting or minimized, and post-processing of the device is unnecessary.

Further, in the present invention, in the present invention, attraction by a magnet is used as a method for applying a preload to the outer race in a direction away from each other by an external force. With this method of applying a preload by attraction with a magnet, the work of applying a preload is simple, and it is not necessary to make the outer race a special shape for applying a preload, and if the outer race is made of a magnetically attractable material. Good. Therefore, the outer race is easy to manufacture.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a bearing device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a finishing process of the outer periphery of a housing, and FIG. 3 is a state in which the bearing device is inserted into a fixed drum. 4 is a graph showing the relationship between the environmental temperature and the preload in the present embodiment, and FIG. 5 is a graph showing the relationship between the environmental temperature and the loss torque in the present embodiment.

In FIG. 1, reference numeral 21 is a housing. A reference hole 21a is formed in the center of the housing 21. The shaft 4 is inserted into the reference hole 21a. The shaft 4 is formed with two grooves 4a and 4b, and each groove 4a
And a plurality of balls 22 are installed along the circumferential direction of 4b. An upper race 23 and a lower race 24 are arranged on the sides facing the grooves 4a and 4b, respectively. Grooves 23a, 24a are formed on the inner peripheral surface of each race 23, 24, and the ball 22 is held by the grooves 23a, 24a and the grooves 4a, 4b. Further, the outer peripheral surfaces of the races 23, 24 are fixed to the inner peripheral surface of the reference hole 21a in a state where pressure is applied by an external force in a direction away from each other (outward direction). By this force, the balls 22 arranged above and below are preloaded in the outer direction (in the opening end direction of the housing 21).

 Next, a method of manufacturing this bearing device will be described.

First, attach the ball 22 and the upper race 23 to the shaft 4,
Insert a retainer (ball retainer), not shown, as necessary. Next, the upper race 23, the outer periphery of which is tighter than the inner diameter of the housing 21, is press-fitted into the housing 21 together with the balls 22 and the shaft 4 at room temperature or high temperature. Alternatively, the upper race 23 is fixed to the housing 21 in advance and attached to the shaft 4 together with the ball 22 or in advance of the ball 22. Further, the lower race 24 whose outer circumference is slightly loosened with respect to the inner diameter of the housing 21 is inserted into the housing 21 from below, and the balls 22 and the retainer, if necessary, are inserted into the housing 21 before and after that. The end surface D and the step surface E of the lower race 24 are projected outward from the end surface C of the housing 21.

Next, while rotating the shaft 4, the shaft 4 and each race 23, 24 are made to fit into the ball 22. Then, the lower race 24 is sucked downward (to the right in FIG. 1) with a force equivalent to the appropriate preload. Further in that state, an adhesive is injected from the hole 21b into the clearance between the lower race 24 and the inner diameter of the housing 21 through the hole 21b to fix the same. In this case, as a method for applying a preload to the ball 22, a step E formed on the lower race 24 is used.
It can be done by sucking with a load. Further, it is preferable that the end surface D of the lower race 24 is attracted downward by attracting it with an electromagnet. As a method of fixing the lower race 24 to the housing 21, instead of adhering with the above-mentioned adhesive, the lower race 24 is formed to fit tightly with the inner diameter of the housing 21 at room temperature, and Made of a material with a small coefficient of thermal expansion,
The lower race 24 inserted in the housing 21 may be sucked in a high temperature environment. At that time, in consideration of a decrease in preload that occurs when the housing 21 and the lower race 24 are cooled to room temperature, suction is performed slightly higher than room temperature. In the case of fitting at such a high temperature, the housing 21 and the lower race 24 are strongly pressure-bonded to each other when cooled to room temperature, so that the lower race 24 need not be bonded.

After the housing 21 and the shaft 4 are integrally formed as described above, the outer periphery of the housing 21 is ground by a grindstone 26 while rotating with the housing 21 by a rubber roller 25 with the shaft 4 as a reference, as shown in FIG. And housing 21
To get the coaxiality of. At this time, in the present embodiment, the upper outer diameter A and the lower outer diameter B of the housing 21 are φA> φB.
I have a relationship. The inner diameter of the fixed drum 1 is formed so as to have a tight relationship only with φB, which is one of the outer diameters of the housing 21. Therefore, the sliding area and sliding resistance when the housing 21 is inserted into the fixed drum 1 (see FIG. 3) can be reduced.
Therefore, the length of the housing 21 can be increased and the bearing span can be increased.

A step 1d is provided on the inner circumference of the fixed drum 1, and a recess 21d having a step 21c slightly larger than the step 1d is provided on the outer circumference of the one housing 21. Then, by inserting the bearing device of FIG. 1 including the housing 21 into the fixed drum 1 at room temperature or at high temperature and aligning the steps 1d and 21c, the axial positions of the fixed drum 1 and the bearing device are determined. To be In this case, the reference surface 1a and the lead step 1b (see FIG. 6) of the fixed drum 1 are finally finished before the bearing device is inserted so that the angle accuracy with respect to the inner diameter of the press-fitting portion of the bearing device is obtained. ing. for that reason,
Only by inserting the bearing device into the fixed drum 1, the angular accuracy of the shaft 4, the reference surface 1a and the lead step 1b can be secured. Therefore, after inserting the bearing device, the fixed drum 1
Fixed drum 1
The work of assembling the bearing device to the shaft can be simplified.

Further, in this embodiment, the shaft 4 is made of stainless steel, the housing 21 is made of a combination of materials such as brass, and the housing 21 is made of a material having a thermal expansion coefficient larger than that of the shaft 4. Therefore, in a low-temperature environment, the amount of linear contraction of the housing 21 is larger than that of the shaft 4, and the contraction of the housing 21 causes the races 23 and 24 to move toward each other. Therefore, in a low temperature environment, the preload on the ball 22 toward the opening end of the housing 21 decreases as shown in FIG. However, on the other hand, the grease injected into the installation portion of the ball 22 has a high viscosity in a low temperature environment, and the rotation resistance due to the grease increases. In this way, in a low temperature environment, the preload on the balls 22 is reduced and the rotational resistance due to grease is increased, but both forces are offset and the increase in loss torque of the bearing is suppressed as shown in FIG.

〔The invention's effect〕

As described above, according to the present invention, the effects listed below can be obtained.

(1) In the bearing device of the present invention, the two outer races are preloaded by the external force in the directions in which they are separated from each other, and the outer races are fixed to the housing in this preloaded state. Therefore, a preload spring for applying a preload to the ball in the outward direction (in the direction of the opening end of the housing) is not required, the number of parts of the bearing device can be reduced, and the work of incorporating the preload spring can be eliminated.

(2) The bearing device of the present invention includes a shaft, balls, an outer race, and a housing. Therefore, a bearing device having a very small outer diameter can be constructed.

(3) Further, the bearing device is configured by assembling the shaft, the ball, the outer race, and the housing, and the outer peripheral portion of the housing serves as a mounting surface for a device such as a rotary head device. Therefore, when the bearing device is assembled,
It is possible to finish the outer peripheral portion of the housing with reference to the shaft. If the mounting surface of the outer peripheral part of this housing is used as a reference and it is installed in equipment such as a rotary head device, the coaxiality between the center of the equipment and the shaft can be secured high, and post-processing of equipment such as a rotary head device becomes unnecessary it can.

(4) In the method for manufacturing a bearing device according to the present invention, as a method for applying a preload to the outer races in a direction away from each other as described above, the outer races are attracted by a magnet. Therefore, it is possible to apply a reliable preload to the outer race with a simple operation. If the outer race is made of a magnetically attractable material, its shape is free, and a special shape for applying a preload is unnecessary. Therefore, the shape of the outer race can be simplified.

(5) Further, when the housing is made of a material having a coefficient of thermal expansion larger than that of the shaft, since the outer races are preloaded in a direction away from each other, the preload on the balls may be reduced in a low temperature environment. Therefore, the increase in resistance due to the viscosity of the lubricant such as grease in a low temperature environment can be offset, and the rotation loss can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a bearing device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a finishing process of the outer periphery of a housing, and FIG. 3 is a state in which the bearing device is inserted into a fixed drum. 4 is a graph showing the relationship between the environmental temperature and the preload in the present embodiment, FIG. 5 is a graph showing the relationship between the environmental temperature and the rotation loss of the bearing in the present embodiment, and FIG. FIG. 1 is a half sectional view showing a bearing portion of a conventional rotary head device. 4 ... Shaft, 4a, 4b ... Groove, 21 ... Housing, 21a
…… Reference hole, 22 …… Ball, 23 …… Upper race, 24 ……
Lower race.

Claims (3)

(57) [Claims] 1. A shaft having two grooves formed on its outer circumference, a plurality of balls arranged in each groove, and a ball supporting these balls from the side facing each groove. There are two outer races and a housing that holds the two outer races on the inner peripheral portion, and the two outer races are preloaded in a direction in which they are preliminarily separated from each other by an external force. A bearing device, wherein the bearing device is fixed to an inner peripheral portion, and an outer peripheral portion of the housing serves as a mounting surface for a device using a bearing. 2. The bearing device according to claim 1, wherein the housing is made of a material having a coefficient of thermal expansion larger than that of the shaft. 3. A two outer groove formed on the outer circumference of the shaft, and a plurality of balls arranged in the two grooves are supported on the supporting side of the shaft from a side facing the respective grooves. A bearing device characterized in that a race is provided, the outer race is attracted by a magnet to apply a preload to the outer race in a direction in which the outer race is separated from each other, and each outer race is fixed to the support side in the state where the preload is applied. Manufacturing method.