GB2297871A

GB2297871A - Securing bearing in an electrical hand-held machine tool

Info

Publication number: GB2297871A
Application number: GB9601510A
Authority: GB
Inventors: Alfred Frech; Gerd Berner; Michael Knuth; Uwe Engelfried
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-02-08
Filing date: 1996-01-25
Publication date: 1996-08-14
Anticipated expiration: 2016-01-25
Also published as: CN1063879C; CN1136491A; GB2297871B; IT1282090B1; DE29501974U1; GB9601510D0; ITMI960144A0; ITMI960144A1

Abstract

An electrical hand-held machine tool having an electric motor which is arranged in a motor housing and comprising a rotor having a rotor shaft, rear and front rotor bearings (13, 24) and a fan impeller, the motor housing (12) being flange-connected to a gearbox housing (16) which contains a gearbox (18), an air guide ring (34) being arranged between the gearbox housing (16) and the motor housing (12), which air guide ring (34) guides the air flow, which is produced by the fan impeller (22) outwards away from the rotor (14) with minimal flow resistance, and the front rotor bearing being fixed with respect to the gearbox housing (16) by a separate axial securing means, characterized in that the front rotor bearing (14) is resiliently secured axially in position by means of the air guide ring (34), for which reason a separate axial securing ring is unnecessary. <IMAGE>

Description

Electrical hand-held machine tool Prior art The invention is based on an electrical hand-held machine tool of the generic type of Claim 1.

Electrical hand-held tools are already known whose rotor can be placed into the motor housing as a preassembled unit with the front rotor bearing and rear rotor bearing and output drive pinion, the final position of the rotor in the electrical hand-held machine tool being defined by fitting the gearbox housing, in particular with the preassembled main spindle and output drive pinion. In this case, a supporting plate which belongs to the preassembled rotor unit engges behind the front rotor bearing axially, the front rotor bearing engaging with the outer ring into the bearing seating on the gearbox housing side.

The supporting plate, which engages behind the front rotor bearing with its inner edge region, is screwed by means of its outer edge region at the end to the gearbox housing such that the inner region of the plate is supported with a prestressing force on the rotor bearing.

In consequence, the front rotor bearing is fixed in the electrical hand-held machine tool such that it cannot be displaced axially.

Other electrical hand-held machine tools which are designed as angle grinders are known, in which the rotor is not preassembled, that is to say is mounted in the gearbox housing without the front rotor bearing and without the drive pinion, the front rotor bearing having previously been inserted into its bearing seating, which is arranged on that side of the gearbox housing which faces the motor housing. The drive pinion cannot be mounted on the free end of the rotor shaft until the front region of the rotor shaft has been passed through the inner ring of the front rotor bearing. The outer ring of the front rotor bearing is in this case secured in position against axial displacement in the gearbox housing by means of an axial securing ring which is fixed in an incision in the bearing seating.

In the case of these electrical hand-held machine tools, an air guide ring is braced in an axially tight manner between the gearbox housing and the motor housing and passes the motor cooling air out of the motor housing. In the case of these electrical hand-held machine tools, the small bevel gear must be unscrewed in advance for removal of the rotor, in order that the rotor shaft can be axially withdrawn to the rear through the front rotor bearing.

In terms of cooling and silencing, these machines are considerably better than hand-held machine tools having a supporting plate, but they have the disadvantage that the simplified assembly technology with a preassembled rotor cannot be used for them.

In contrast, the electrical hand-held machine tools with a supporting plate have the advantage of favourable assembly technology, although they are clearly inferior to hand-held machine tools having the air guide ring in terms of cooling, noise behaviour and thermal efficiency.

Advantages of the invention The electrical hand-held machine tool according to the invention, having the characterizing features of Claim 1, in contrast has the advantage that a low noise level, better cooling and lower weight are achieved with a favourable assembly technology.

The loudness, which is 3 dB lower, the power yield, which is increased by approximately 10%, a 40 g weight saving and saving of an additional part make it possible to manufacture a high-quality electrical hand-held machine tool as cost-effectively as would otherwise have been possible only by accepting reductions in the quality of the machine.

Complete preassembly of the rotor considerably simplifies the assembly of the electrical hand-held machine tools. In addition, maintenance and repairs are considerably simplified since, after releasing the flange connection between the gearbox housing and the motor housing, the complete armature can be removed without any further assembly measures.

The use of the air guide ring as a retaining element for the front rotor bearing makes it possible to dispense with a separate axial securing ring and corresponding machining of the gearbox housing, for example an annular groove for the insertion of the circlip locking ring.

This results in time savings during assembly.

Further advantageous refinements of the invention result from the dependent claims.

Drawing An exemplary embodiment of the invention is explained in more detail in the following description, with reference to the associated drawing.

Figure 1 shows a longitudinal section of the front region of an angle grinder according to the invention, Figure 2 shows a view of an air guide ring from the front, Figure 3 shows a cross-section of the air guide ring according to Figure 2, Figure 4 shows an enlarged detail from Figure 3, Figure 5 shows the air guide ring according to Figure 2 from the rear, Figure 6 shows the air guide ring according to Figure 5 seen from above, and Figure 7 shows an exploded drawing according to Figure 1.

Description of the exemplary embodiment Figure 1 shows a longitudinal section through an angle grinder 10 having a motor housing 12 which accommo dates a rotor 14. The motor housing 12 is flangeconnected to a gearbox housing 16 which contains an angled drive 18.

The rotor 14 is provided with a rotor shaft 20 which is fitted with a preassembled fan impeller 22, a front rotor bearing 24, a small bevel gear 26 and a lock nut 28.

The front rotor bearing 24 comprises an outer ring 29 and an inner ring 30 with roller bodies which are arranged in between them but are not designated in more detail. The front rotor bearing 24 is seated on the gearbox housing side in a bearing seating 32, being surrounded by a bearing seating ring 25. The latter is made of rubber and is used to prevent the front rotor bearing 24 rotating with respect to the gearbox housing 16, and is used as a vibration damping element as well as a seal between the outer bearing ring 29 and the gearbox housing 16.

A plastic air guide ring 34 is arranged axially between the fan impeller 22 and the front rotor bearing 24, is supported in the ready-assembled angle grinder 10 with a region, which is located radially on the inside, axially on the outer ring 29 of the front rotor bearing 24 and is centered on the gearbox housing side in a selfcentering manner by a stepped internal diameter region 36, which is arranged radially further outwards, on a cylindrical step which is used as the air guide ring seating 38.

The air guide ring 34 is centered by means of the lower edge of its upper air outlet channel 40 on a step 42 of the gearbox housing 16, being clamped by means of its radially outer edge in a sealing manner between the gearbox housing 16 and the flange-connected motor housing 12.

The angle drive 18 on the gearbox housing side comprises a large bevel gear 44, which engages in a rotationally fixed and concentric manner around a main spindle 46. The main spindle 46 is mounted rotatably in the upper region of the gearbox housing 16 in an upper spindle bearing 48 and in the lower region in a lower spindle bearing 52 which is arranged in the neck part 50, which can be flange connected, of the gearbox housing 16.

Figure 2 shows the air guide ring 34 in a view from the front. In this case, the upper air outlet channel 40 and a lower air outlet channel 41 are clearly evident.

The upper air outlet channel 40 has an edge 54, which is drawn forwards. The latter is provided on its lower edge with two reinforcing ribs 55, 56. The stepped internal diameter region 36 is connected via radially extending supporting ribs 58, 59 to an axially set-back supporting wall 66 which is supported, according to Figure 1, axially on the outer ring 29 of the front rotor bearing 24. The supporting ribs 58 to 65 stiffen the supporting wall 66 with respect to the stepped internal diameter 36 and are used for axially securing and for prestressing the bearing seating ring 25 in the gearbox housing 16.

In consequence, the prestressed bearing seating ring 25 can fix the bearing outer ring 29 of the front rotor bearing 24 radially and in a sprung and vibration-damping manner.

The supporting wall 66 is provided with a central aperture 68 whose edge 70 has a sinusoidal contour running in a circle.

In consequence, the edge 70 forms eight radially inwardly projecting supporting tongues 72, 73, 74, 75, 76, 77, 78, 79, each of which is fitted with one of eight central axial studs 80 to 87, the supporting wall 66 acting as a disc spring in the region of the supporting tongues 72 to 79. The axial studs 80 to 87 ensure there is a point contact between the supporting wall 66 and the end of the outer ring 29 of the front rotor bearing 24, and provide tolerance compensation which reduces the accuracy requirements for the bearing and dimensions of the supporting wall 66. The outer ring 29 of the front rotor bearing 24 is in any case axially prestressed by each of the axial studs 80 to 87, it being possible, in detail, for the prestressing force between the supporting tongues 72 to 79 with respect to the outer ring 29 to differ.The air guide ring 34 and its supporting wall 66 are dimensioned such that a minimum prestressing force fixes the outer ring 29 of the front rotor bearing 24 in its intended axial position.

When the angle grinder 10 is started up, the small bevel gear is accelerated, with the rotor 14 and the front rotor bearing 24, axially to the rear by means of the force components between the small bevel gear 26 and the large bevel gear 44. The supporting wall 66 of the air guide ring 34 fixes the front rotor bearing 24, via the outer ring 29, and thus the entire rotor 14 axially in a sprung manner, and minimizes its axial displacement.

In consequence, it is not possible for any excessive tooth play to occur between the small bevel gear 24 and the large bevel gear 44. This has a positive effect on the life of the angle drive 18.

Figure 3 shows a cross-section of the air guide ring 34 according to Figure 2. In this case, the stepped internal diameter region 36, the upper air outlet channel 40, the lower air outlet channel 41, the supporting rings 59, 60, 61, 62, 63 and the axial studs 81, 82, 83 and 84, as well as the reinforcing rib 55, are clear.

Figure 4 shows an enlargement of the detail X according to Figure 3, the supporting ribs 62, 63 and the axial studs 83 and 84 being clear.

Figure 5 shows a view of the air guide ring 34 from the rear. In this case, the sinusoidal contour of the edge 70 of the central aperture 68 in the supporting wall 66 is clear.

The supporting wall 66 is supported in a stiffening manner with respect to the radially outer region of the air guide ring 34 by eight concentrically arranged intermediate ribs 88 to 95, against an axial annular collar 96 which runs concentrically with respect to the stepped internal diameter region 36 on the front side of the air guide ring. Six tie ribs 99, 100, etc., up to 104 are supported between this axial annular collar 96 and a further annular collar 98 which surrounds said axial annular collar 96 concentrically and at a distance from it.

As a result of this large number of ribs, the air guide ring 34 forms a lamellar component which is particularly stiff in torsion.

On the outer circumference, the air guide ring 34 is fitted on its rearward end with twelve studs 106 to 117 which deform axially during the screw-connection process during installation of the angle grinder according to Figure 1 with a motor housing 12 which is flange-connected at the end, and make possible contact without any play between the motor housing 12 and the gearbox housing 16.

Figure 6 shows a view of the air guide ring 34 from above, the upper air outlet channel 40 and the studs 109, 110, etc., to 115 being clear.

Figure 7 shows a three-dimensional exploded illustration of the angle grinder 10 according to Figure 1 with the essential individual parts. Shown sequentially along the motor axis 11 are the motor housing 12, a rear rotor bearing 13, the rotor 14 with the front region of the rotor shaft 20, the fan impeller 22, the air guide ring 34, the front rotor bearing 24 and an elastic bearing seating ring 25, as well as the small bevel gear 26 and a lock nut 27, which is screwed onto a threaded collar, which is not shown in any more detail, of the rotor shaft and secures the axial position of the small bevel gear 26.

The gearbox housing 16 can be identified, being illustrated exploded with respect to the spindle axis 43 and pivoted with respect to the motor axis 11, said gearbox housing 16 being flange-connected to the motor housing 12 by means of four flange screws, of which only one, 15, is shown. Viewed in the direction from underneath, the gearbox housing 16 is followed by the large bevel gear 44, which is followed by the neck part 50, into which the lower spindle bearing 52 is pressed. The main spindle 46 can be seen axially underneath the neck part 50 and is fixed axially in the gearbox housing 16 by means of the large bevel gear 44. In this case, the large bevel gear 44 is axially supported against the lower spindle bearing 52.

The upper spindle bearing 48 can be seen between the large bevel gear 44 and the gearbox housing 16.

Claims

1. Electrical hand-held machine tool having an electric motor which is arranged in a motor housing (12) and comprising a rotor (14) with a rotor shaft (20), rear and front rotor bearings (13, 24) and a fan impeller (22), the motor housing (12) being flange-connected to a gearbox housing (16) which contains a gearbox (18), preferably an angled gearbox, an air guide ring (34) being clamped in axially between the gearbox housing (16) and the motor housing (12), which air guide ring (34) guides the air flow, which is produced by the fan impeller (22) outwards away from the rotor (14) with minimal flow resistance, and the front rotor bearing (24) being fixed by axial securing means with respect to the gearbox housing (16), characterized in that the air guide ring (34) is supported on the front rotor bearing (24), so that it is possible to dispense with further axial securing means for the rotor bearing (24).

2. Electrical hand-held machine tool according to Claim 1, characterized in that the air guide ring (34) is supported by its inner edge (70) in an axially sprung manner on the rotor bearing (14).

3. Electrical hand-held machine tool according to Claim 2, characterized in that the air guide ring (34) is supported by its inner edge (70), at the end, on the outer ring (29) of the rotor bearing (24).

4. Electrical hand-held machine tool according to Claim 2 or 3, characterized in that a supporting wall (66), which supports the inner edge (70), of the air guide ring (34) is designed as a disc spring.

5. Electrical hand-held machine tool according to Claim 2, 3 or 4, characterized in that the air guide ring (34) is fitted on its inner edge (70) with radially inwardly directed supporting tongues (72 to 79).

6. Electrical hand-held machine tool according to one of the preceding claims, characterized in that the supporting studs (72 to 79) are each fitted with an axial stud (80, 81, etc., up to 87), via which they are supported against the outer ring (29) of the rotor bearing (24).

7. Electrical hand-held machine tool according to one of the preceding claims, characterized in that the air guide ring (34) has a plurality of annular regions (96, 98) which are arranged concentrically with respect to one another, form a labyrinth seal on one side together with one end of the fan impeller (22) and form an internal diameter region (36) on the other side, for centering the air guide ring (34) with respect to the gearbox housing (16).

8. Electrical hand-held machine tool according to one of the preceding claims, characterized in that the air guide ring (34) is fitted with axial air outlet channels (40, 41) on radially opposite sides on its radial circumference.

9. Electrical hand-held machine tool according to one of the preceding claims, characterized in that the air guide ring (34) is fitted with supporting ribs (58 to 65), as well as intermediate ribs (88 to 95) and tie ribs (99 to 104) which stiffen the supporting wall (66) with respect to the stepped internal diameter region (36) and/or with respect to an axial annular collar (96) as well as with respect to an annular collar (98), so that axial forces of the rotor (14) which act on the supporting tongues (72 to 79) and are passed via the front rotor bearing (24) are converted via elastic deformation of the supporting studs (72 to 79) without other regions of the air guide ring (34) being deformed.

10. Air guide ring for an electrical hand-held machine tool, preferably for an angle grinder, in particular according to the precharacterizing clause of Claim 1, characterized in that it is clamped in the housing (12, 16) and is supported on the front rotor bearing (24) such that it is possible to dispense with further axial securing means.

11. Air guide ring according to Claim 10, characterized in that the air guide ring (34) is supported by its inner edge (70) in an axially sprung manner on the outer ring (29) of the rotor bearing (24), a supporting wall (66), which supports the inner edge (70), of the air guide ring (34) being designed as a disc spring.

12. An electrical hand-held machine tool substantially as herein described with reference to the accompanying drawings.

13. An air guide ring for an electrical hand-held machine tool, substantially as herein described with reference to the accompanying drawings.