Starting motor

Abstract: A starting motor comprising: an overrunning clutch (40) including an output shaft (7) adapted to receive rotation of an armature shaft (2) of a d.c. motor (1), a clutch outer (41) adapted to be coupled to the output shaft (7) through a helical spline (8), and a clutch inner (22) coupled to the clutch outer (41) through a roller (23) and transmitting a one-way rotation to a pinion (28) provided at a front end side; a retainer (27) fitted to a rear end part of the output shaft (7), and adapted to receive a rear end of the clutch outer (41) which has returned to a backward position; a supporting frame (17) fixed to a fixed part, and supporting the rear end part of the output shaft (7) through a bearing (18); and a shift lever (34) having a lower end part engaged with an annular engagement groove (41c) in an axial direction, and turning to move the overrunning clutch (40) to either one of a forward position and the backward position, the annular engagement groove (41c) provided with a rear side part of the clutch outer (41); wherein the annular engagement groove (41c) in the overrunning clutch (40) is adapted to have a rear end side inner periphery overhung the retainer (27) when the clutch outer (41) is in the backward position, and the inner periphery is formed to have a larger diameter than an outer periphery of an outer end of the bearing supporting part of the supporting frame (17).

Description: The present invention relates to a starting motor which transmits rotation from an armature shaft of a d.c. motor to an output shaft, transmits the rotation of the output shaft to a pinion through an overrunning clutch, and starts an engine. In particular, the invention concerns a starting motor comprising an output shaft adapted to receive rotation of an armature shaft of a d.c. motor, an overrunning clutch including a clutch outer adapted to be coupled to the output shaft through a helical spline, and a clutch inner coupled to the clutch outer through a roller and transmitting a one-way rotation to a pinion provided at a front end side a supporting frame fixed to a fixed part, and supporting the rear end part of the output shaft through a bearing, a shift lever having a lower end part engaged with an annular engagement groove in an axial direction, and turning to move the overrunning clutch to either one of a forward position and a backward position, the annular engagement groove provided with a rear side part of the clutch outer, and a stopper provided on the output shaft before said helical spline to restrict the forward movement of the clutch outer, the annular engagement groove in the overrunning clutch being adapted to have a rear end side inner periphery overhung the retainer when the clutch outer is in the backward position, and the inner periphery being formed to have a larger diameter than an outer periphery of an outer end of the bearing supporting part of the supporting frame. In Figure 3 there is shown a cross sectional view of the essential parts of a conventional starting motor. A d.c. motor 1 has an armature shaft 2 extended from an armature, and the armature shaft 2 has a front end part provided with a sun gear 2a, which is constituted by a small gear. Reference numeral 3 designates a yoke which has field poles (not shown) mounted thereto. Reference numeral 4 designates an intermediate bracket which supports a front part side of the armature shaft 2 through a bearing 5. Reference numeral 6 designates a front bracket which is coupled to the yoke 3 through the intermediate bracket 4. Reference numeral 7 designates an output shaft which is arranged at a front end of the armature shaft 2 through a steel ball 11 to be coaxial with the armature shaft 2, and which has an intermediate part provided with a helical spline 8. The output shaft has a clutch outer stopper 10 formed thereon before the helical spline 8 through an annular groove 9. The helical spline 8 has a plurality of tooth spaces 8a formed therein at equal pitches in the circumferential direction. There is formed a single through tooth space 8b between every adjoining tooth spaces 8a. The stopper 10 has through cutouts 10a formed therein to correspond to the through tooth spaces 8b. The output shaft 7 has a recess of thread portion 7b provided thereon behind the helical spline 8 to have a small diameter. Reference numeral 13 designates a planetary reduction gear which is constituted as follows: Reference numeral 14 designates a plurality of planetary gear which mate with the sun gear 2a, and which are supported by supporting pins 15 through bearings 16. The supporting pins 15 are fixed to a carrier 7a which is formed by a flange at a rear end of the output shaft 7. Reference numeral 17 designates an internal gear frame which is fixed in the front bracket 6, and which has an inner periphery formed with internal teeth 17a, the internal teeth causing the planetary gears 14 meshed therewith to revolve. The internal gear frame 17 has a front end inner periphery supporting the output shaft at its rear end part through a bearing 18. Reference numeral 20 designates an overrunning clutch which is carried on the output shaft 7, and which is constituted as follows: Reference numeral 21 designates a clutch outer which has helical spline threads 21a formed thereon to engage with the tooth spaces 8a of the helical spline 8 on the output shaft 7. Reference numeral 22 designates a clutch inner which transmits one-way rotation to the clutch outer 21 through rollers 23, which is supported by the front bracket 6 through a bearing 24 and which supports the output shaft 7 through a bearing 25. Reference numeral 26 designates an engagement ring which is fitted into a rear end outer periphery of the clutch outer 21. Between the engagement ring and the rear end of an enlarged portion of the clutch outer, there is formed an annular engagement groove 21b. Reference numeral 27 designates a retaining ring which is fitted in the output shaft 7 to receive the clutch outer 21 at a predetermined position when the clutch outer 21 moves backward , and which is constituted by an E-shaped retaining ring. Reference numeral 28 designates a pinion which is carried on a front end of the clutch inner 22 by spline connection, which has a front end held by a stopper 29, and which is urged in a forward direction by a compression spring 30. Reference numeral 31 designates an electromagnetic switch which is mounted on the front bracket 6, which has a plunger 32 forming a movable core, and which has a hook 33 inserted in and supported by the plunger 32 so that the hook 33 has a front end projected. Reference numeral 34 designates a shift levr which has a two-pronged upper end engaged with the hook 33, which has a two-pronged lower end engaged with the annular engagement groove 21b of the overrunning clutch 20 in an axial direction, and which is supported by the front bracket 6 at an intermediate projection 34a to be turnable, using the intermediate projection 34a as a fulcrum. Reference numeral 35 designates a rubber caulk which is fitted in a cutout of the front bracket 6. Mounting the overunning clutch 20 to the output shaft 7 is as follows: The helical spline threads 21a of the clutch outer 21 of the overrunning clutch 20 which has been assembled is passed the through cutouts 10a of the stopper 10, and through the tooth spaces 8b of the helical spline 8 until the threads 21a has reached the recess 7b of the thread portion. The clutch outer 21 is turned by a half pitch of the threads 21a, the threads 21a are engaged with the tooth spaces 8a of the helical spline 8, and the clutch outer 21 is returned in a forward direction. Then, the retaining ring 27 is fitted in the output shaft to restrict the backward position of the clutch outer 21. Under the conditions, when the overrunning clutch 20 moves forwardly, front ends of the threads of the clutch outer 21 hit against the stooper 10 to restrict the forward position of the clutch outer 21. The operation of the conventional starting motor will be explained. When a starting switch for an engine of a vehicle etc., an exciting coil (not shown) of the electromagnetic switch 31 is energized to inwardly attract or withdraw the plunger 32. The shift lever 34 is turned by the plunger counterclockwise (refer to Figure 4) through the hook 33 to move the overrunning clutch 20 forwardly. The forward movement of the overrunning clutch 20 causes the pinion 28 to mate with a ring gear of the engine. The withdrawal of the plunger 32 causes a movable contact (not shown) to get in pressure contact with a pair of fixed contacts (not shown), thereby closing an energizing circuit to the d.c. motor 1. As a result, the armature rotates, the rotation of the armature shaft 2 is transmitted to the pinion 28 through the planetary reduction gear 13 and the overrunning clutch 20 to rotate the ring gear of the engine, thereby starting the engine. When the engine has started, high speed rotation of the engine drives the pinion 28 in the same direction. However the provision of the overrunning clutch 20 prevents the armature shaft 2 from receiving the driving force. When the engine has started and the starting switch has been turned off, the plunger 32 of the electromagnetic switch 31 moves forwardly and returns to the forward position to turn the shift lever 34 clockwise in this figure to return it to the home position, causing the overrunning clutch 20 to move backwardly and return to the home position. In the conventional starting motor as stated above, when the overrunning clutch 20 is at the backward position, the annular engagement groove 21b is located ahead of the retaining ring 27. This means that the distance between the front end of the overrunning clutch 20 and the retaining ring 27 becomes great, which creates a problem in that the external length of the starting motor is enlarged. It is an object of the present invention to solve the problem, and to provide a starting motor wherein the length of an overrunning clutch in a forward side with respect to a retainer fitted in an output shaft is shortened. In this way and in accordance with a general object in relation to the aforesaid US-A-5,028,805, it is possible to reduce the external length of the starting motor. According to the invention there is provided a starting motor in accordance with the opening paragraph of this specification, characterised in that a retainer is fitted to a rear end part of the output shaft and adapted to receive a rear end of the clutch outer which has returned to a backward position, said stopper is located adjacent said helical spline, and the annular engagement groove of the clutch outer is formed with the clutch outer as a one-piece construction. In accordance with the present invention, the length of the overrunning clutch in a forward direction with respect to the retainer is shortened to reduce the external length of the starting motor. In accordance with the present invention, the position of the annular engagement groove of the clutch outer is shifted backwardly with respect to the position of the retainer. The distance between the front end of the overrunning clutch and the retainer is accordingly shortened to make the shape of the starting motor smaller in an axial direction. The invention will now be described by way of example and with reference to the accompanying drawings. In drawings, Figure 1 is a cross sectional view of the essential parts of the starting motor according to a first embodiment of the present invention; Figure 2A is a cross sectional view showing the relation between an annular engagement groove and a retainer of a clutch outer of an overrunning clutch; Figure 2B is a cross sectional view showing the state wherein the clutch outer has been moved backwardly to mount the overrunning clutch to an output shaft; Figure 3 is a cross sectional view showing the essential parts of a conventional starting motor. Referring now to Figure 1, there is shown an axial cross sectional view showing the essential parts of a first embodiment of the starting motor of the present invention. Reference numerals 1-11, 13-18, 22-25, 27-35, 2a, 7a, 7b, 8a, 8b, 10a, 17a and 34a designate parts similar to those shown in Figure 3. Reference numeral 40 designates an overrunning clutch which is mounted onto the output shaft 7 and which comprises a clutch outer 41 and the clutch inner 22, the clutch inner receiving one-way rotation from the clutch outer 41 through the rollers 23. The clutch outer 41 has an inner peripheral portion formed with helical spline threads 41a, which are engageable with the tooth spaces 8a of the helical spline 8 of the output shaft 7. The clutch outer 41 has the inner diameter of a rear end portion formed to be larger than the outer diameter of the retaining ring 27 so that the rear end portion overhangs the retaining ring and is extended. The clutch outer 41 has a rear end outer periphery provided with an engagement projection 41b. Between the engagement portion 41b and a rear end surface of an enlarged portion of the clutch outer 41, there is formed an annular engagement groove 41c, which is engaged with a lower end of the shift lever 34 in an axial direction. Because the rear end portion of the clutch outer 41 is extended backwardly to overhang the retaining ring 27 as stated above, the annular engagement groove 41c is formed to be shifted backwardly with respect to the location of the retaining ring 27 in comparison with the conventional starting motor. The distance between the front end position of the clutch outer 41 and the location of the retaining ring 27 is shortened accordingly in companion with the conventional device. As a result, the distance between a front end of the overrunning clutch 40 and the retaining ring 27 is also shortened to reduce the external length of the starting motor. Referring now to Figure 2A, there is shown an arrangement relation between the rear end portion of the clutch outer 41 of the overrunning clutch 40 and a bearing supporting portion of an end plate of the internal gear frame 17. The inner diameter D of the rear end portion of the clutch outer 41 is formed to be greater than the outer diameter d of the bearing supporting portion of the internal gear frame 17. In this manner, the distance t between the rear end of the clutch outer 41 and the end plate of the internal gear frame 17 becomes smaller in comparison with the conventional device. Referring now to Figure 2B, there is shown a state wherein the clutch outer 41 is backwardly inserted in order to mount the overrunning clutch 40 onto the output shaft 7. It is seen that the clutch outer 41 has been backwardly moved while the inner diameter of the rear end portion of the clutch outer 41 evades the outer diameter of the bearing supporting portion of the inner gear frame 17. Reference signs in the claims are intended for better understanding and shall not limit the scope.

Claims: A starting motor comprising: an output shaft (7) adapted to receive rotation of an armature shaft (2) of a d.c. motor (1); an overrunning clutch (40) including a clutch outer (41) adapted to be coupled to the output shaft (7) through a helical spline (8), and a clutch inner (22) coupled to the clutch outer (41) through a roller (23) and transmitting a one-way rotation to a pinion (28) provided at a front end side; a supporting frame (17) fixed to a fixed part, and supporting the rear end part of the output shaft (7) through a bearing (18); a shift lever (34) having a lower end part engaged with an annular engagement groove (41c) in an axial direction, and turning to move the overrunning clutch (40) to either one of a forward position and a backward position, the annular engagement groove (41c) provided with a rear side part of the clutch outer (41); and a stopper (10) provided on the output shaft (7) before said helical spline (8) to restrict the forward movement of the clutch outer (41); the annular engagement groove (41c) in the overrunning clutch (40) being adapted to have a rear end side inner periphery overhung a retainer (27) adapted to receive a rear end of the clutch outer (41) when the clutch outer (41) is in the backward position, and the inner periphery being formed to have a larger diameter than an outer periphery of an outer end of the bearing supporting part of the supporting frame (17), characterised in that the retainer (27) is fitted to a rear end part of the output shaft (7); said stopper (10) is located adjacent said helical spline (8), and the annular engagement groove (41c) of the clutch outer (41) is formed with the clutch outer as a one-piece construction. A starting motor according to Claim 1, wherein the clutch outer (41) has a rear end outer periphery provided with an engagement portion (41b) which is formed with the clutch outer (41) as a one-piece construction. A starting motor according to Claim 2, wherein the annular engagement groove (41c) is formed between the engagement portion (41b) and an enlarged portion of the clutch outer (41).

Inventors: ISOZUMI SHUZO, ISOZUMI, SHUZO, ISOZUMI, SHUZO, MITSUBISHI DENKI KABUSHIKI KAISHA
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: F02N15
IPC codes: F02N15