JPH05240244A - Bearing pre-load device - Google Patents

Abstract

PURPOSE:To provide a bearing pre-load device capable of adding a sufficient pre-load of a fixed value to an arm deflection. CONSTITUTION:An arm 21 receiving a moment load is rotatably supported to a link shaft 22 through two thrust bearings 23a, 23b provided at an axial interval with an arm part 21a between and a deep groove ball bearing 24 in the middle part, and the lower surface of the lower thrust bearing 23b is fastened by a pre-loading nut 26 through a disc spring 25. On the upper surface of the pre-loading nut 26, a projection part 26a is provided. At fastening, the nut 26 is screwed until the projection part 26a makes contact with one end part of a collar 27 the other end of which makes contact with the different diameter stepped part 22a of a link shaft at fastening, whereby a fixed deflection is given to the disc spring 25 so that a fixed pre-load is added to the thrust bearings 23a, 23b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing preloading device for reducing play in the thrust direction of a link shaft portion that receives a moment load, and is particularly suitable for use in a transfer arm link shaft portion of an ultra-high vacuum robot. It is a thing.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a frog leg type in-vacuum transfer robot has a first robot mounted on an inner shaft 1a and an outer shaft 2a of two concentric motors 1 and 2, respectively.
The arms 3 and 4 are connected to the second arms 6 and 7, respectively, via a link shaft 5, and the tips of the second arms 6 and 7 are transferred to a transfer tray (transfer section) 9 for the wafer 8. It is connected via a similar link shaft (not shown). The first arm 3, 4 and the second arm 6, 7 form a link mechanism.

During operation, by rotating the shafts 1a and 2a of the concentric biaxial motors 1 and 2 within the angular range of θ ₁ and θ ₂ , the transfer tray 9 is linearly reciprocated in the direction of arrow b. It is like this.

FIG. 4 is a sectional view of a main part of a fixing device using a link shaft (5 in FIG. 5) of an arm link part of the above-mentioned vacuum transfer robot. It is the same. In the figure, reference numeral 11 denotes a first arm driven by an actuator such as a motor, and the first arm 11 is fixed to a link shaft 13 by a set screw 12. A second arm 15 is attached to the link shaft 13 via upper and lower deep groove type radial ball bearings 14a and 14b provided at intervals in the axial direction, and the radial ball bearings 14a and 14b are attached. Is a nut 1 that is screwed into a screw 13a formed on the link shaft 13.
6 is fixed to the link shaft 13 so as to prevent a combined load in both radial and axial directions due to a moment load by applying a preload.

In operation, two radial ball bearings 14 are mounted axially spaced apart to support the second arm 15.
The shaft shake of the link shaft 13 is prevented by a and 14b,
The drive from the first arm 11 is transmitted to and supported by the second arm 15.

[0006]

When applied to the above-described arm supporting device and the frog leg type ultra-high vacuum wafer transfer robot shown in FIG. 5, the first arm 11 and the second arm 15 are connected to each other at the intersection thereof. The moment load of the load coming from the tip of the two arms 15 is applied. Therefore, the bearing 14
The second arm 15 bends in the direction of gravity due to backlash such as axial and radial clearances of a and 14b.

Further, when a transferred object is normally placed on a transfer tray attached to the tip of the second arm 15 via a similar link mechanism, the arm itself bends due to its weight.

In order to reduce the above-mentioned bending, a preload is usually applied to the bearing portion. Conventionally, as a method of applying a preload, as shown in FIG. 4, a screw 13a is cut at one end of a link shaft 13,
The nut 16 was tightened to give a preload.

However, the above structure has the following problems.

(I) It is difficult to apply a constant preload due to variations in assembling method and friction of threaded portions.

(Ii) In particular, in a bearing used in a vacuum, since the lubricating oil cannot be used, if the preload is excessively applied, the bearing portion is immediately worn out and reaches the end of its life.

(Iii) In deep groove type ball bearings and angular type ball bearings, sufficient preload cannot be applied to arm deflection due to the life.

The present invention solves the above-mentioned problems and extends the life of each bearing while preventing the arm from flexing by allowing the thrust bearing to receive the axial load which was conventionally prevented by applying a preload to the radial ball bearing. The object of the present invention is to provide a bearing preload device that can apply a sufficient preload at a constant value.

[0014]

In order to achieve the above-mentioned object, the present invention provides a bearing device for rotatably supporting an arm member, which receives a combined load in both radial and axial directions due to a moment load, about an axis. One end portion of two thrust bearings, which are provided at intervals in the axial direction by inserting the arm member, is fitted to a predetermined position of the shaft through an elastic body such as a disc spring and has a predetermined length. It is characterized in that the protrusion contacting the end face of the collar is tightened by a preload nut formed on the front surface in the screwing direction so as to apply a constant preload to the thrust bearing.

Further, a deep groove ball bearing is mounted between two thrust bearings which are axially spaced from each other by inserting the arm member.

[0016]

Since the present invention is configured as described above, a preload nut having a protrusion formed on the front surface in the screwing direction is
The thrust bearing is tightened in the axial direction by screwing it toward the end surface of one thrust bearing through an elastic body such as a disc spring, and an axial preload due to the elastic force of the elastic body such as a disc spring is applied to the thrust bearing. In addition, it plays a role of preventing looseness in the fitting portions of the arm member, the thrust bearing, and the shaft portion that receive the moment load.

The tightening operation of the preload nut is carried out until the protrusion of the preload nut comes into contact with the end portion of the collar fitted and attached at the predetermined position of the shaft. As a result, the strain amount of the elastic body such as the disc spring becomes constant, so that a constant preload due to the constant strain amount can be applied to the thrust bearing. Further, the amount of strain of the elastic body such as the above-mentioned fixed disc spring is
It is determined only by the mechanical dimensions such as the protrusion of the preload nut and the axial length of the collar. Therefore, a constant preload can be applied to the thrust bearing regardless of how to assemble it.

Further, by mounting the radial bearing between the two thrust bearings which are provided with the arm member inserted therebetween and are spaced apart in the axial direction, it is not necessary to apply a large preload to the radial bearing. Therefore, the life of the radial bearing can be extended.

[0019]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view of a main part of a bearing preloading device showing an embodiment of the present invention.

In the figure, reference numeral 21 denotes one of two arms constituting a link mechanism which crosses each other, and
The first arm 21 is supported by a link shaft 22, and upper and lower thrust bearings 23 are attached to the supporting portion with a part 21a of the arm 21 inserted therein and spaced apart in the axial direction.
a, 23b and these two thrust bearings 23a23b
A deep groove ball bearing 24 is provided between the two, and the lower end surface of the lower thrust bearing 23b is tightened by a preload nut 26 via a disc spring 25.

A protrusion 26a is formed on the upper surface (tip portion) of the preload nut 26, and the protrusion 26a is
Link shaft 22 formed near the lower end of the deep groove ball bearing 24
The other end (lower end) of the collar 27, one end of which contacts the different diameter step portion 22a, contacts the other end (lower end) of the collar 27. 2 in the figure
Reference numeral 7 is a locking nut for the preload nut 26.

Next, the operation will be described. When the preload nut 26 having the projection 26a on one side (upper surface) is screwed into the threaded portion 22b of the link shaft 22 with the projection 26a first, the lower end of the collar 27 will be described. Depending on the position and the length of the protrusion 26a, the disc spring 25 is compressed until the upper end of the collar 27 comes into contact with the different diameter step 22a of the link shaft 22.

The disc spring 25 has a height dimension h in a natural state where no pressure is applied, and a strain amount δ when pressure is applied (normally h dimension is 0.5h, 0.75h, etc.). Is displayed), the above preload nut 2
The disc spring 25 can be provided with a certain amount of strain determined by the length of the protrusion 26a of No. 6 and the axial dimension of the collar 27 and the position of the different diameter stepped portion 22a of the link shaft 22. The disc spring 25 includes two upper and lower thrust bearings 23.
Axial preload can be applied to a and 23b via the arm portion 21a.

According to this embodiment, the axial preload can be applied only to the thrust bearings 23a and 23b, and the deep groove ball bearing 24 is not subjected to unnecessary axial preload, so that the service life is increased accordingly. Therefore, the operating life of the bearing device in vacuum also increases.

2 and 3 are a plan view and a side view of a main part of an ultra-high vacuum wafer transfer robot as shown in FIG. 5 which uses the bearing preload device of FIG. 1 described above. 1 and the same reference numerals as those shown in FIG. 5 indicate the same or similar parts.

In the figure, the first arms 3 and 4 attached to the inner shaft 1a and the outer shaft 2a of the concentric two-shaft motor 1 are respectively connected to the second arm 6 and the second arm 6 via link shafts 22 and 32, respectively. 7 are connected. The second arm 7 is not shown in the drawing because it is located behind the first arm 3.

The second arms 6 and 7 are connected to a tray 9 for conveyed objects such as wafers via a similar bearing preload device and gear 10. The gear 10 uses the meshing of the gears fixed to the second arm by the reverse rotational movement of the two first arms to perform the action of moving the conveyed product straight.

In operation, shafts 1a and 2 of a concentric two-axis motor
By rotating a within a predetermined angle range, a predetermined linear reciprocating motion is performed on the conveyed product tray 9 via the first arms 3 and 4 and the second arms 6 and 7 connected by the link shafts 22 and 32, respectively. To be given.

In the above embodiment, the link shaft of the in-vacuum transfer robot has been described, but the bearing preload of the present invention is applied to a portion where it is desired to apply a constant preload by using the thrust bearing in a portion which receives moment load and is required to reduce backlash. A device is available.

It is also possible to use another elastic body instead of the disc spring 25.

[0031]

As described above, according to the present invention, in a bearing device that rotatably supports an arm member that receives a moment load around an axis, the arm member is inserted and provided at intervals in the axial direction. One end of each of the two thrust bearings is fitted to a predetermined position of the shaft through an elastic body such as a disc spring, and a protrusion that comes into contact with the end surface of the collar having a predetermined length is attached to the front surface in the screwing direction. By tightening with the preload nut formed in the above, the prescribed strain amount can be applied to the elastic body such as the disc spring with only the mechanical size, so that a constant preload can be applied regardless of how to assemble. Can be added to bearings.

Further, by mounting a deep groove ball bearing between two thrust bearings which are axially provided with an arm member interposed therebetween, a moment load is separated into a radial load and an axial load. Since the thrust bearing and the radial bearing can receive the radial bearing without applying unnecessary axial preload to the radial bearing, the operating life in a vacuum where the lubricating oil cannot be used can be extended by that amount.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a bearing preloading device showing an embodiment of the present invention.

FIG. 2 is a plan view of an essential part of an ultra-high vacuum wafer transfer robot using the bearing preload device of the present invention.

FIG. 3 is a side view of a main part of the ultra-high vacuum wafer transfer robot of FIG.

FIG. 4 is a cross-sectional view of a main part of an arm link support portion showing a conventional example.

FIG. 5 is a perspective view of a conventional vacuum transfer robot.

[Explanation of symbols]

 21 Arm 22 Link Shaft 22a Different Diameter Steps 23a, 23b Thrust Bearing 24 Deep Groove Ball Bearing 25 Disc Spring 26 Preload Nut 26a Projection 27 Locking Nut

Claims (2)

[Claims] 1. A bearing device for rotatably supporting an arm member that receives a moment load around a shaft, wherein one end portion of two thrust bearings that are provided at intervals in the axial direction by inserting the arm member is provided. The thrust bearing is tightened by a preload nut formed on the front surface in the screw-in direction by tightening a projection that is fitted to a predetermined position of the shaft and contacts the end surface of the collar having a predetermined length through an elastic body such as a disc spring. A bearing preload device characterized in that a constant preload is applied to the bearing. 2. The bearing preloading device according to claim 1, wherein a deep groove ball bearing is mounted between two thrust bearings which are provided with an arm member interposed therebetween and which are provided at intervals in the axial direction.