GB2329936A

GB2329936A - A starter motor with needle bearings between pinion shaft and output shaft

Info

Publication number: GB2329936A
Application number: GB9820975A
Authority: GB
Inventors: Stefan Renner; Roger Ferwagner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-09-30
Filing date: 1998-09-25
Publication date: 1999-04-07
Anticipated expiration: 2018-09-25
Also published as: GB2329936B; FR2769049A1; DE19743122A1; GB9820975D0; FR2769049B1

Abstract

A starter motor 10 for starting an internal combustion engine comprising a meshing pinion 15 supported by a pinion shaft 14 and a output shaft 20 from an electric motor 24 on which the pinion shalt 14 is mounted, characterised in that at least one, more particularly the front bearing site of the pinion shaft 14 and the output shaft 20 is constructed as a needle bearing 32 whose needle sleeve is pushed into a bearing bore on the pinion shaft 14 and whose needles 32a rest upon a hardened section of the output shaft 20. Preferably a second rear bearing site is also constructed as a needle bearing 33 whose needle sleeve is pushed into a bearing bore on the pinion shaft 14 and whose needles 33a rest upon a hardened section of the output shaft 20. Another preferable feature is that the pinion shaft 14 is mounted on another needle bearing 13 at bearing bracket 11.

Description

2329936 1 Fr - -.)., starter State of the art Tle invention relates to

improved mounting of the pinion shaft on the output shaft on the front bearing bracket of a free-projecting starter for internal combustion engines. For cases such as this, bearing bushes are used today (cf EP 0 518 895 B 1), which deflect in particular in the case of high starter capacities in heavy duty operation as a result of high transverse force loading. In addition, as a result of the relatively large bearing clearance which is necessary in this case, there is an undesirable build-up of noise and increased wear to the pinion as well as the outer bearing of the pinion shaft.

According to the proposal of the present invention, in free-projecting starters the bearing bush which has been used to date is replaced by a needle bearing for mounting the pinion shaft on the output shaft of the starter, at least in the front region. Since the needles only roll upon the output shaft when the pinion meshes with and disengages from the toothed rim of the internal combustion engine, and the bearing otherwise only needs to ensure axial displacement between these parts, it is necessary to guarantee that the needles do not produce longitudinal grooves on the output shaft over time, which would impede or prevent a rolling of the bearing. This is reliably prevented in that the bearing region of the output shaft is surface-hardened. The needles of the needle bearing are embedded 'm a needle sleeve, which is pressed into the bearing bore of the pinion shaft. In anadvantageous manner, the rear bearing bush between the pinion bearing and output shaft is also constructed in like manner as a needle bearing. This type of solution results in quiet, almost wear-free running, the needles running or being axially displaced directly on the 2 hardened regions of the output shaft. This results in a substantially increased service life as compared with sinter or pocket bushes, 'm which lubricant is accommodated in moulded pockets. In contrast, the solution according to the invention offers reduced noise production and above all improved guidance of the pinion shaft by means of a smaller bearing clearance.

The solution accordmig to the invention can be particularly advantageously used in combination with needle bearings or roller bearings in the front bearing bracket, which cooperate with the outside of the pinion shaft.

Drawings An embodiment of the invention is illustrated in the drawmgs. Figure 1 is a longitudinal section through a starter for motor vehicles. Figure 2 is a longitudinal section through the pinion shaft with a front and rear needle bearing for the output shaft of the starter.

Description of the embodiment

The free-projecting starter 10 illustrated in the longitudinal section in Figure 1 for staffing internal combustion engines in motor vehicles has a front bearing bracket 11, in whose bearing bore 12 a needle bearing 13 for receiving a pinion shaft 14 is fitted. At its front end, the pinion shaft 14, also referred to as a pinion axle, supports a meshing pinion 15 for engaging in the toothed rim, not shown, of the internal combustion engine. At its rear end, the pinion shaft 14 supports an idler 16 and a meshing mechamism 17, which is actuated via an engaging lever 18 by a starter relay 19. The pinion shaft 14 is mounted so as to be rotatable and axially displaceable with its meshing mecharnism 17 on the output shaft 20 of the starter.

3 Arranged at the rear end of the output shaft 20 is a planetary gearing 2 1, on whose drive side a sun wheel 22 engages, which is arranged on the rotor shaft 23 of a starter motor 24. The planetary gearing 21 is accommodated via an elastic intermediate bearing 25 in the housing 26 of the starter motor 24.

It can be seen in Figure 1 that the pinion shaft 14 is mounted on the output shaft 20 by means of two bearing points 30 which are spaced apart axially. Figure 2 shows that a front needle bearing 32 and a rear needle bearing 33, each with a needle sleeve, are pressed into the spaced-apart regions in the bearing bore 3 1 of the pinion shaft 14, the needle sleeves preventing an axial displacement of the respective needles 32a and 33a. In this respect, the needles rest upon hardened sections of the output shaft 20 'm each case. During the starting procedure, the starter relay 19 is firstly switched on and the pinion shaft 14 together with the idler 16 is axially and rotatably rolled forwards by means of the engaging lever 18 via a helical slide at the rear end of the output shaft. During this procedure, the needles 32a and 33a of the needle bearings 32 and 33 roll upon the output shaft 20 and are thereby simultaneously axially advanced. Following closure of the switching contacts of the starter relay 19, the starter motor 24 is switched on, so that the starter pinion 16 meshes with the toothed rim of the internal combustion engine and starts the engine. In this respect the needle bearings 32 and 33 remain unchanged on the output shaft 20, since the output shaft and the pinion shaft are driven with the same rotational speed by the starter motor 24 during the starting procedure. As soon as the internal combustion engine starts, it in turn drives the pinion shaft 14 via its toothed rim, the idler 16 being released. Until the starter motor 24 is switched off, the pinion shaft 14 rotates more rapidly than the output shaft 20, so that the needles 32a and 33a continue to roll upon the output shaft. When the starter 10 is switched off, the pinion shaft 14 is finally moved back into 4 the inoperative position by a restoring spring, the needle bearings 32 and 33 again being axially displaced on the output shaft 20.

Claims

Claims

1. Free-projecting starter for starting internal combustion engines in motor vehicles with a front bearing bracket, in whose mounting bore a bearing for receiving a pinion shaft is fitted, the pinion shaft at its front end supporting a meshing pinion and at its rear end being connected via a meshing mechanism to an electric starter motor, and the pinion shaft being mounted on an output shaft of the starter motor at two points axially spaced apart, characterised in that at least one, more particularly the front bearing site of the pinion shaft on the output shaft is constructed as a needle bearing, whose needle sleeve is pushed into the bearing bore of the pinion shaft and whose needles rest upon a hardened section of the output shaft.

2. Free-projecting starter according to claim 1, characterised 'm that a second, more particularly the rear bearing site is also constructed as a needle bearing, which is pressed with its needle sleeve into the rear section of the bearing bore of the pinion shaft and whose needles rest upon a hardened, further section of the output shaft.

3. Free-projecting starter according to claim 1 or 2, characterised in that the pinion shaft is mounted with a further needle bearing on its outer side in the bearing bore of the bearing bracket.

5. A free-projecting stater for starting internal combustion engmies in motor vehicles substantially as herein described with reference to the accompanying drawings.