GB2317136A

GB2317136A - A bolt-holework process for forming bolt holes in a flange of a hub unit bearing

Info

Publication number: GB2317136A
Application number: GB9719542A
Authority: GB
Inventors: Shinichirou Kashigawi; Yoshiyuki Minami; Yasuhiro Miyata; Shinji Morimoto
Original assignee: Koyo Seiko Co Ltd
Current assignee: Koyo Seiko Co Ltd
Priority date: 1996-09-13
Filing date: 1997-09-12
Publication date: 1998-03-18
Anticipated expiration: 2017-09-12
Also published as: KR19980024632A; JP3992161B2; DE19740171A1; JPH1085880A; GB2317136B; KR100498105B1; GB9719542D0

Abstract

The invention has an object to provide a bolt-hole work process for forming bolt holes in a flange of a hub unit bearing. Cores 1w are formed at multiple places circumferential of a flange 1f of an outer race 1 of the hub unit bearing. The cores 1w are punched by a punching press 11, 12, 13 and then are directly serrated by a serration punching press 31, 32, 33 for forming serrated holes 1p. Alternatively, the cores are formed with chamfers 1h, k, i at their respective opposite circumferential edges and then are serrated by the serration punching press utilising a female die with die holes and serrating punches so as to be formed with serrated holes therein.

Description

2317136

SPECIFICATION

A BOLT-HOLE WORK PROCESS FOR FORMING BOLT HOLES IN A FLANGE OF A HUB UNIT BEARING BACKGROUND OF THE INVENTION

The present invention generally relates to a work process for forming bolt holes In a flange of a hub unit bearing, on which hub unit an automotive wheel is mounted, and more particularly to a bolt-hole work process for forming bolt holes in the flange of the hub unit bearing which is adapted to negate the need f or reaming the produced bolt holes and to prevent decrease in the slip torque between the bolt holes and bolts fitted therein.

As seen In Fig. 9, the hub unit mounted with the automotive wheel comprises an outer race 1 on which the wheel (not shown) is mounted. split-type inner races 2a and 2b to be securely f itted around an axle (not shown). a plurality of balls (rollers) 3-3, cages 4-4 and sealing members 5 and 6. The outer race 1 is formed with a flange if in which 4 or 5 bolts 7 are normally squeezed and fixed at places circumferential thereof. The bolts 7 are inserted through bolt holes defined in a hub portion of the unillustrated wheel thereby securing the wheel by way of nuts.

The bolts 7 are so f ixed to the flange if of the outer race 1 as to be prevented from rotating during the rotation of the wheel. Such a fixing of the bolts is accomplished by means of serration fitting. More specifically, bolt holes la are f irst produced in the f lange lf of the outer race 1 and subsequently the bolts 7 formed with serrations 7s at the proximal ends thereof are squeezed into the bolt holes la, respectively, the serrations having a slightly greater diameter than the bolt holes. Thus, the bolts 7 themselves are f ixed to the flange lf of the outer race 1 for the mounting of the wheel.

In general, the bolt holes la produced by drilling the flange lf of the outer race 1 may sometimes suffer work-hardening on the drilled surfaces thereof.

Unfortunately. If the bolts 7 are squeezed into such work-hardened bolt holes la, the serrations 7s at the proximal ends of the bolts 7 may be crushed, becoming Incapable of accomplishing a sufficient fixing torque. In this connection. the drilled holes are subsequently finished by reaming the surfaces thereof.

In the art. there has been proposed a serration work process f or f orming the bolt holes la in the f lange lf of the outer race 1 In the hub unit, as shown in Fig. 10, which process comprises the steps of transferring serrations la, to the bolt holes by means of a half press- cutting of the f lange using serrating punches, and punching through the 2 remaining thickness of the flange on a die by means of punches so as to f orm cores 1a2 beneath the serrations la, (see, for example, Japanese Unexamined Patent Publication No.07(1995)-314071).

As described above, the work process wherein the bolt holes la are drilled in the f lange lf of the outer race 1 and then are subject to the reaming requires a relatively long work time and also additional working machines if the number of workpieces increases. This results in increased costs. In addition. the reaming subsequent to the drilling of the bolt holes la in the outer race 1 results in the work-hardening to further increase the hardness of the hole surfaces. Accordingly, If the bolts 7 are squeezed into the reamed bolt holes, the serrations 7s of the bolts 7 are crushed to impair mesh with the bolt holes and hence, an insufficient slip torque results. Additionally, hard metal drills are employed for drilling and reaming works so as to enhance the working precision. accounting for the increase In the working costs.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present:Invention ls to provide a work process f or f ormIng bolt holes in a f lange of a hub unit bearing. which process is adapted to negate the need for the reaming and reduce the work time, to provide f or a positive serration f itting between the bolt holes and the bolts and to reduce costs for the cutting tools.

In a f Irst aspect of the invention f or achieving the above object, provided Is the bolt-hole work process for forming a plurality of serrated holes circumferentially of the flange formed around the outer race of the hub unit bearing so as to allow serrated bolts to be squeezed thereinto, the process comprising the steps of: producing the cores of the aforesaid bolt holes by press-cutting by means of a female die with die holes in cooperation with punches to be fitted into the corresponding die holes.. and directly serrating the resultant cores or otherwise, previously forming chamfers at the respective upper circumferential edges of the cores or at the respective opposite circumferential edges thereof or forming bolt seats together with chamfers at the respective upper circumferential edges of the cores and subsequently press-cutting the cores by means of the female die with the die holes in cooperation with the serrating punches to be fitted into the corresponding die holes, whereby the serrated holes are formed.

In a second aspect based on the first aspect of the invention, provided Is the bolt-hole work process for f ormIng the bolt holes In the f lange of the hub unit bearing 4 further characterized in that each serrated hole has teeth numbering by an integral multiple of those of the serration of each bolt squeezed into the serrated hole.

In a third aspect based on the first or second aspect of the invention. provided is the bolt-hole work process for forming a plurality of bolt holes in the flange of the hub unit bearing further characterized in that each serrated hole. as the bolt hole, has slightly smaller dimensions than the serration of each bolt fitted in the serrated hole.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 (A) of Fig. 1 is a f ragmentary f ront elevation showing an outer race of a hub unit bearing, the outer race worked according to the bolthole work process of the invention f or f orming bolt holes In a f lange of the hub unit bearing, whereas Fig. l(B) is a vertical sectional view showing one of the bolt holes; Fig. 2 diagramatically illustrates various types of work processes f or producing cores in the f lange of the outer race, Fig. 2A illustrating a case where each core is produced simply by press-cutting with a core punch, Fig. 2B illustrating a case where a chamfer Is formed at the upper end of each core by pressing only on the surf ace thereat, Fig. 2C illustrating a case where chamfers are formed at the opposite ends of each core by pressing on the corresponding surfaces, and Fig. 2D Illustrating a case where a bolt scat together with a chamf er are f ormed at the upper end of the core by pressing only the corresponding surfaces; Fig. 3 diagramatically illustrates the construction of a working machine for producing the cores in the flange of the outer race; Fig. 4 is a fragmentary sectional view showing a surface pressing machine for forming chamfers at the respective upper sides of the cores in the flange of the outer race; Fig. 5 is a fragmentary sectional view showing a surface pressing machine for forming chamfers at the respective opposite sides of the cores in the flange of the outer race; Fig. 6 is a fragmentary sectional view showing a surface pressing machine for forming seats together with chamfers at the respective upper sides of the cores in the flange of the outer race; Fig. 7 diagramatically illustrates the construction of a serration working machine for forming serrated holes in the cores previously produced in the flange of the outer race; Fig. 8A of Fig - 8 is a f ragmentary sectional view of a serrated hole in the flange of the outer race, whereas Fig. 8B is a fragmentary sectional view of a male serration formed on the bolt squeezed Into the serrated hole in the flange of the outer race; Fig. 9 is a vertical sectional view showing the prior-art automotive hub unit; and Fig. 10 is a sectional view showing the bolt hole in the prior-art automotive hub unit, the hole including the serration fitted with the bolt.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now. specific embodiments of the invention will hereinbelow be described with ref erence to the accompanying drawings.

Fig. 1 (A) of Fig. 1 is a f ragmentary front elevation showing an outer race of a hub unit bearing, the outer race worked according to the bolthole work process of the invention f or f orming bolt holes in a f lange of the hub unit bearing. Fig. 1B Is a vertical sectional view of one of the bolt holes. It is to be noted that in order to avoid redundant description, like parts will be denoted by like reference characters used in the description of the prior art.

Normally, a flange lf of an outer race 1 includes 4 or 5 bolt holes lp produced by drilling and circumferentially arranged at regular intervals. The prior- art bolt holes la (see Fig. 9) are, as described above, subject to reaming subsequent to the drilling work and thereafter, the bolts are squeezed into the respective bolt holes for carving (transferring) in the holes serrations corresponding to those formed at the proximal ends of the bolts, respectively.. According to the work process of the invention, serrated holes lp are formed beforehand in the bolt holes 1P in the f lange lf of the outer race 1 in a manner which will be described hereinbelow (Since the serrated holes are identical to the bolt holes lp, they are denoted by the same reference characters 1p).

To form the serrated holes lp as the bolt holes in the f lange lf of the outer race 1 of the aforesaid bearing, cores 1w (see Fig. 2 and 3) are first produced by a press cutting utilizing core punches 11. and the resultant cores 1w are subject to a press cutting using serrating punches 31 having a slightly greater diameter than the core punches 11 (see Fig. 7). Next, description will be made on the work process for formIng the serrated holes lp.

Fig. 2 dlagramatically illustrates various types of works for producing a plurality of cores at places circumferential of the flange lf of the outer race 1. The cores 1w are first produced in the flange lf of the outer race 1 by the press cutting. The cores 1w thus produced may include the following types: a core lw, as shown in Fig. 2A, produced simply by punching through the f lange with the core punches 11; a core 1w, as shown in Fig. 2B, having a chamf er 1h f ormed by pressing only on a surf ace at the upper end thereof; a core, as shown in Fig. 2C, having chamfers 1h and 1I formed by pressing on surfaces at the opposite ends thereof; and a. core 1w, as shown in Fig. 2D, having a bolt seat 1J and a chamfer 1k formed by pressing only on a surface at the upper end thereof. Subsequent to any one of the above work processes, the serrations are f ormed in the respective bolt holes.

Next, description will be made on the process for press-cutting the cores 1w with the core punches 11 and the process for forming the chamfers.

Fig. 3 dlagramatically illustrates the construction of a core working machine for producing the cores 1w in the flange lf of the outer race 1. The machine comprises a female die 12 Including die holes 12a formed at multiple places circumferential thereof for receiving the corresponding punches 11 and serving to set the outer race 1 in place, a stripper 14 serving to hold down the outer race 1 and including a plurality of holes 14a arranged circumferentially thereof and adapted to guide the corresponding punches 11. a punch holder 13 retaining the multiple core punches 11 arranged circumferentially thereof, and a holder 15 for retaining the punch holder 13 by way of a backing plate 16 disposed atop the punch holder 13. The female die further includes holes 12b continuous to the corresponding die holes 12a for receiving scrap pieces R produced during the cutting work, the holes 12a having a diameter slightly greater than that of the scrap pieces R slightly greater in diameter than the cores 1w. Coil springs 18 associated with stripper bolts 19 are circumferentially disposed at multiple places between the stripper 14 and the backing plate 16, the coil springs applying a biasing force during the punching work such as to allow the core punches 11 to readily leave the respective cores 1w In the flange lf when the holder 15 moves from a lower dead point to an upper dead point. The holder 15 is adapted for vertical movement as mounted to an unillustrated slide attached to an eccentric shaf t of the press.

As shown in the lef t half portion f rom the center line of Fig. 3, when the holder 15 reaches the lower dead point, the core punches 11 in coopertion with the female die 12 with the die holes 12a produce the cores lw in the outer race 1. In this case, 4 or five cores lw may be produced at a time, or otherwise, the cores may be sequentially produced as the outer race 1 is rotated. Since the cores lw are produced by the press-cutting, there occurs no work-hardenIng on the surfaces of such cores lw. This allows for a smooth serration work for forming the serrated holes, which will be described hereinbelow. Incidentally, the outer race 1 is formed by forging into a predetermined shape in advance while the flange lf Is also formed by forging so as to have a flat surface and a surface of a predetermined curve.on its opposite sides bef ore the outer race is subject to the punching work by the press. However, detailed description thereof is omitted.

The cores 1w In the flange lf of the outer race 1 are further subject to the serration work. As seen in Fig. 2A, the serration work may be performed on the cores lw not chamfered by pressing on their respective surfaces. In the case of Fig. 2B where the chamfers 1h are f ormed by pressing only on the surfaces at the respective upper ends of the cores lw prior to the serration work. the outer race 1 with the cores lw formed in the flange lf is set In a female die 2 3 so that chamfering punches 21 mounted to an upper holder 22 may press on the corresponding surfaces at the edges of the cores lw, as shown in Fig. 4. In the case of Fig. 2C where the chamfers 1h and 1I are formed by pressing on the surf aces at the opposite ends of the cores 1w prior to the serration work, respectively, the chamfering punches 21 mounted to the upper holder 22 and chamfering punches 25 mounted to a lower holder 24 press on the corresponding surfaces at the opposite edges of the cores lw at the same time, as shown In Fig. 5.

In the case of Fig. 2D where the seats l j together with the chamfers lk are each formed at the upper ends of the cores lw prior to the serration work, the outer race 1 is set in a f emale die 28 subsequent to the production of the cores lw In the flange lf of the outer race 1 so that chamfering punches 27 mounted to an upper holder 26 form the bolt seats lj and the chamfers 1k at the corresponding edges of the cores lw.

Fig. 7 diagramatically illustrates the construction of a serration work machine for serrating the cores lw previously produced in the flange of the outer race 1. The machine comprises a female die 32 including die holes 32a cIrcumf erentially formed at multiple places for receiving corresponding serrating punches 31 and serving to set the outer race 1 in place, a stripper 34 serving to hold down the outer race 1 and including holes 34a circumferentially formed at multiple places for guiding the corresponding serrating punches 31, a punch holder 33 for circumferentially retaining the serrating punches 3 1, and a holder 35 for retaining the punch holder 33 by way of a backing plate 36 disposed atop the punch holder 33. The female die 32 further includes holes 32b continuous to the corresponding die holes 32a as formed therebeneath and having a diameter slightly greater than that of the die holes 32a for receiving scrap pieces produced during the cutting work. A plurality of coil springs 38 associated with stripper bolts 39 are circumferentially disposed at places between the stripper 34 and the backing plate 36, the coil springs applying a biasing force during the punching work such as to allow the- serrating punches 31 to readily leave the serrated holes lp in the f lange lf when the holder 35 moves from the lower dead point to the upper dead point. The holder 35 is adapted for vertical movement as mounted to the slide attached to the eccentric shaft of the unillustrated press.

In the serration work machine, at least 2 positioning pins 37 are disposed in the female die 32. The positioning pins 37 are used f or positioning some cores lw in the f lange lf of the outer race 1. When the outer race 1 is set in position, some cores 1w are each fitted about the positioning pins 37 for positioning. When the outer race 1 set in place, which cores lw to receive the positioning pins 37 are determined. For the serration work on the cores 1w used for the positioning, the outer race 1 is disengaged from the die to be rotated so that such cores lw are set in position by fitting the serrated holes lp about the positioning pins 37 (the serrated hole lp has the same Inner diameter as the core and therefore, is usable for the positioning). Alternatively, the positioning pins 37 may be drawn from the bottom of the female die. Otherwise, the positioning pins may be carried on springs (not shown), respectively, so as to be resiliently retracted by the serrating punches 31 descending for the press -cutting work whereby all the cores are rendered into the serrated holes lp by one press work-. The serration work machine has such a construction that, as illustrated by the lef t half portion f rom the center line of Fig. 7, the holder 35 reaching the lower dead point allows the serrating punches 31 to form the serrated holes lp in the cores 1w. The serrated holes are formed by the press, too and theref ore, no workhardening occurs on the surf aces of the serrated holes. This, as will be described hereinbelow, provides for a smooth f IttIng with male serrations 7s f ormed at the proximal ends of the bolts 7., Fig. 8A is a fragmentary enlarged view of the serrated hole lp for receiving the bolt. the hole produced in the flange lf of the outer race 1 in the aforementioned manner. Fig. 8B is a fragmentary enlarged view of the serration 7s (hereinaf ter referred to as "male serration 7 s") on the bolt 7 to be fitted in the serrated hole lp. The bolts 7 are fitted in the serrated holes lp formed in the flange lf of the outer race 1 by squeezing the male serrations 7s of the bolts 7 into the serrated holes, respectively. In this case.

- 14 the serrated holes lp and the male serrations 7s are worked based on a given relationship therebetween.

The serrated hole lp in the flange If of the outer race 1 is so formed as to have teeth numbering an integral multiple of teeth of the male serration 7s of the bolt 7. This assures that the male serration 7s of the bolt 7 can be f itted in the serrated hole lp in the f lange If of the outer race 1 at any position.

That is, this negates the need for bringing the bolts 7 in phase with the serrated holes lp In the flange If of the outer race 1. when the bolts are squeezed therein. When the bolts are each squeezed into the serrated holes, the serrations of the both properly fit each other thereby maintaining a satisfactory slip torque. In the art, it is difficult to bring the serrtIon of the bolt in mesh with the serrated hole lp which is great in length of the teeth thereof, and therefore, the both need to be brought into phase with each other. On the other hand, the serrated hole lp with teeth numbering an integral multiple of those of the male serration 7s of the bolt 7 makes it easy to bring the both Into mesh with each other, thus negating the need for bringing the both into phase with each other.

The serrated holes lp in the flange If and the male serration 7s of the bolts 7 are so dimensioned as below in consideration of that the bolts 7 are squeezed into the - is - respective serrated holes lp, as the bolt holes, formed in the flange lf of the outer race 1.

More specif ically, the male serration 7s of the bolt 7 is formed to have a major diameter slightly greater than a minor diameter of the serrated hole lp. That is, DI>D2 where D, denotes the major diameter of the male serration 7s of the bolt 7 and D2 denotes the minor diameter of the serrated hole lp. Furthermore, each groove of the serrated hole lp has a width slightly smaller than that of each tooth crest of the male serration 7s. That is, provided that the width of the tooth crest of the male serration 7s is represented by "Ba, the width of the groove of the serrated hole lp is represented by %B-ao. In short, the serration formed in the bolt hole in the f lange lf of the outer race 1 has dimensions slightly smaller than those of the serration of the bolt 7. It is preferred that the opposite side surfaces of a tooth of the male serration 7s of the bolt 7 form the same angle 0 as that f ormed by the opposite side surfaces of a groove of the serrated hole lp in the flange lf but there may be allowed some variations.

The foregoing description indicates that the production of the serrated hole lp with teeth numbering an integral multiple of those of the serration 7s of the bolt 7 and the f orming of the serrated hole in dimensions smaller than those of the serration of the bolt produce ef f ect in the work process wherein the cores are first produced by punching followed by chamfering and then serrating for forming the serrated holes. The above features are also applicable to the following work processes:

1) A work process comprising the steps of producing the cores by the punching press, followed by chamfering, shaving and serrating for forming the serrated holes.

2) A work process comprising the steps of producing the cores by the punching press, followed by serrating for forming the serrated holes.

3) A work process comprising the steps of producing the cores by the punching press, followed by shaving and serrating for forming the serrated holes.

4) A work process comprising the steps of producing the cores by the punching press, followed by shaving, chamfering and serrating for forming the serrated holes.

5) A work process comprising the steps of producing the serrated holes by a punching press employing the serrating punches.

As described in the forigoing, the bolt-hole work process f or producing the bolt holes in the f lange of the hub unit bearing according to the invention negates the need for drilling and reamIng which are required by the prior art and also allows all the bolt holes to be worked at a time. Therefore, a notable cost reduction can be achieved.

1 The outer race of the hub unit bearing fabricated according to the work process of the invention does not require the serration bolts to be brought into phase with the bolt holes and besides, provides for positive press-fitting of the bolts.

Additionally, the bolts squeezed into the flange of the outer race notably decreases the adverse possibility of the reduced slip torque, thus contributing to a dramatic decrease in the incidence of defective products.

Furthermore, costs for the cutting tools such as drills and reamers and for the equipment for the cutting work are dramatically decreased.

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Claims

CLAIM

1. A bolt-hole work process for forming serrated holes, or bolt holes, for receiving serration bolts at multiple places circumferential of a flange formed around an outer race for use in a hub unit bearing, the process comprising the steps of press-cutting cores for said bolt holes by means of a press utilising a female die including a die hole and a punch to be fitted in the corresponding die hole, and directly punching serrated holes in said cores by means of a press work or otherwise, optionally forming chamfers at the respective upper circumferential edges or the respective opposite circumferential edges of said cores or forming bolt seats together with chamfers at the respective upper circumferential edges of the cores and then punching the serrated holes in said cores by. a press work or otherwise utilising a female die including a die hole and serrating punch to be fitted in the corresponding die hole.

2. A bolt-hole work process for forming bolt holes in the flange of a hub unit bearing as set forth in claim 1, wherein the serrated hole has teeth numbering an integral multiple of those of the serration of the bolt squeezed into the serrated hole.

3. A bolt-hole work process for forming bolt holes in the flange of a hub unit bearing as set forth in claim 2, wherein the serrated hole, as the bolt hole, is formed in dimensions slightly smaller than those of the serration of the bolt squeezed into the serrated hole.

4. A process for forming bolt holes in a hub unit bearing, comprising press-cutting a core for a said bolt hole, and subsequently forming serrations in the wall of the bolt hole by a punching operation.

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5. A process as claimed in claim 4, wherein a chamfer is formed at an end of the core prior to forming the serrations.

6. The combination of a hub unit bearing and a bolt. the hub unit bearing having a bolt hole for receiving the bolt and having a serrated inner surface, and the outer surface of the bolt being serrated, wherein the number of serrations on the inner surface of the bolt hole is an integral multiple of the number of serrations on the bolt.

7. The combination of claim 6, wherein the outer diameter and thickness of the serrations on the bolt are slightly greater respectively than the diameter of the bolt hole measured at the recess between serrations and the space between the serrations on the wall of the bolt hole.

8. A process for forming bolt holes in a hub unit bearing, substantially as hereinbefore described with reference to Figures 1 to 8 of the accompanying drawings.

9. A hub unit bearing formed by the process of any one of claims 1 to 5 and 8.

10. The combination of a hub unit bearing and bolt, substantially as 1 -hereinbefore described with reference to Figures la, 1b and 8 of the accompanying drawings.

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