WO1991011843A1

WO1991011843A1 - Hand machine-tool with rapid, internally air-cooled electric motor

Info

Publication number: WO1991011843A1
Application number: PCT/DE1991/000059
Authority: WO
Inventors: Fritz Baumann; Werner Rieker
Original assignee: Robert Bosch Gmbh
Priority date: 1990-02-02
Filing date: 1991-01-22
Publication date: 1991-08-08
Also published as: DE4003031A1

Abstract

A hand machine-tool, in particular a right-angle grinder (1), has a high-speed, internally air-cooled electric motor (5). The windings of the electric motor, in particular the rotor (13) and each of the stator coils (18, 20) of the stator (11), consist of a plurality of coils of wire and are each surrounded by at least one protective sheath (23). To cut the cost of protection against mechanical corrosion, each protective sheath (23) consists of at least two interconnected part shells or half-shells (24, 25).

Description

Hand tool with snow-running, internally ventilated electric motor

State of the art

The invention relates to a handheld power tool according to the preamble of claim 1.

Various hand-held machine tools with an electric motor are already known, the motor parts of which are wound in a coil-like manner and are surrounded by protective covers. These consist of radial, wound dressing-like wound bandages which insulate the motor parts against electrically conductive dust and are intended to protect against the abrasive effect of solid particles impinging on the end windings with the cooling air flow. Such particles that arise when grinding and drilling machines are used strike the end faces of the rotor and stator windings at considerable speed. After impact, these particles can be accelerated considerably again by the high speed of the rotor 13 of up to 30,000 min −1, so that they can easily penetrate through protective coats of the windings and cause shorted turns or interruptions.

The winding bandages have the disadvantage that their production only with complicated z. T. hand-operated winding devices is possible. These work too slowly to fit into an assembly line production line that is common today. The degree of coverage of the areas to be protected is unsatisfactory, particularly in curved areas of the stator windings, and often requires reworking. In addition, due to the partially double-layer winding bandages, the space required for the stator coils is high, which is why the press-in pressure in your seat in the stator lamination stack is very high. This requires a complex manufacturing process and harbors the risk of injury to the coil wires. In addition, the motor cooling of the hand machine tools is made more difficult. One way to avoid these difficulties is to use the

Increase motor size. However, this reduces the portability and manageability. Possible increases in performance through increased cooling are limited. The flow-poor outer shape of the wrapping band also contributes to this. These disadvantages mean that the handheld power tool manufacturers are increasingly attempting to dispense with these protective sleeves, the wear caused thereby being unsatisfactorily manageable even with other means and a reduction in the service life of the handheld power tools being difficult to avoid .

Advantages of the invention

The hand-held power tool according to the invention with the characterizing features of claim 1 has the advantage that its protective covers are in one piece or with multiple layers and can be applied to the parts to be encased by means of assembly line processes without any manual work. Simple technical means are suitable for this purpose, such as, for example, feed devices for the textile material of the protective sleeves and, for example, a punch and an ultrasound or laser welding device. For the hand-held power tool according to the invention, there is also the advantage of the smallest possible size with a long service life and high performance and better handiness. Due to the more streamlined shape of the engine parts and the good thermal conductivity of the protective covers, the cooling is improved and the increased service life and / or improved power output can thus be achieved.

Further advantageous embodiments of the invention result from the subclaims.

drawing

Exemplary embodiments of the invention are explained in more detail in the following description with reference to the associated drawing.

FIG. 1 shows a longitudinal section of an angle grinder, FIG. 2 shows a stator coil of an angle grinder, FIG. 3 shows a cross section of an angle grinder, FIG. 4 shows a rotor of an angle grinder, FIG. 5 shows a manufacturing step when enveloping the stator, and FIG and FIG. 7 shows a tubular casing of a stator coil.

Description of the embodiment

The angle grinder 1 shown in Figure 1 consists of a motor housing 3, which contains an electric motor 5. The motor housing 3 is connected to a gear housing 7 which contains a gear 9. The electric motor 5 consists of a copper wire wound stator and rotor 11, 13. The stator 11 is non-rotatable, the rotor 13 is rotatably arranged in the motor housing 3. A fan wheel 15, which is non-rotatably seated on a rotor shaft 10 near the winding head 14 of the rotor 13, is provided for generating a cooling air flow 16 which is generated by the Cooling inlet openings 17 enter and flow through the gap 12 between rotor 13 and stator 11 for heat transport and can leave motor housing 3 via cooling outlet openings 19. The stator 11 consists of two stator coils 18, 20 which are seated within a stator lamination stack 22.

The following processes take place when using internally ventilated electro-driven machines:

The cooling air flow 16 generated by the movement of the electric motor, like the ambient air, contains the dust-like, solid particles which arise when working with the hand-held machine tool and which strike at high speed against all surfaces and edges located in the area of the cooling air flow. The front faces of the coil-like, copper-wire-wound parts of the electric motors which are exposed to the "sandblasting effect" from the front are particularly sensitive and easily vulnerable. As a result of the abrasive effect, electrically conductive dust particles form undesired electrical contact bridges which can destroy the hand tool. The protective cover 23 shown in the following figures is of particular importance for the end faces of the stator 11 and the rotor 13.

FIG. 2 shows the plan view of a rectangular ring-shaped stator coil 18 in its shape prior to assembly in the angle grinder 1, the electrical connection wires 21 of which emerge from the textile protective cover 23. The protective cover 23 consists, as also made clear in the following FIG. 3, of an upper and a lower, rectangular ring-shaped half-shell 24, 25 which enclose the stator coil 18 in equal parts and which are essentially symmetrical to one another. An angled region of the upper half-shell 24 projecting beyond the outline or the normal projection of the stator coil 18 has an outer weld seam 27 on its outer edge for connection to the lower half-shell 25 An inner weld 28 is arranged in the inner edge of the stator coil 18. The protective sheath 23 can be deformed together with the stator coil 18 in a non-destructive manner to the extent necessary when installing the stator coil 18 in the motor housing 3, in particular when adapting to its cylindrical curvature.

The cross section of the angle grinder 1 shown in FIG. 3 illustrates the arrangement and deformation of the stator coil 18 in the installed state. The stator coil 18 is adapted to the shape of the cylindrical motor housing 3 in that the end faces of the stator coil 18 are curved. The protective sheath 23 surrounding the stator coil 18 is represented by the cross-hatched area. In addition, the weld seam 27 and the lower and upper half-shells 24, 25 connected to each other by it are visible.

In Figure 4, the rotor 13 is shown, which is covered by a protective sleeve 23 in the form of a tube. Whose ends are tied together in an end lacing 31 like sausages. Protrusions are separated by a weld cut between the rotor shaft 10 and the winding head 14. The outer surface of the hose can be gathered and pressed between the rotor laminated cores 22. So that for better heat conduction the cooling air flow 16 can get directly to the rotor core 22, the rotor 13 can be at least partially freed from the protective cover 23 on its outer diameter by grinding. The winding head 14 of the rotor 13 is then reliably protected against the abrasive particle effect.

5 shows the following method steps when applying the protective cover 23 to a stator coil 18, 20 or a rotor 13: A first textile web 33 is arranged on an anvil-like, not shown, cup-shaped recessed counter-holder. The stator coil 18, 20 or the rotor 13, on which a second textile web 35 is placed, is positioned on this. The area of each textile web 33, 35 is more than half the size of the entire surface of the stator coil 18, 20. The two textile webs 33, 35 are rectangular in accordance with the normal projection of the stator coil 18, 20.

A punch stamp, not shown, with a rectangular ring-shaped cutting contour, which is enlarged in comparison to the normal projection of the stator coil 18, 20, is lowered onto the counter-holder via the stator coil 18, 20. The punch hits the counter-holder approximately on the bisecting line of the part to be encased, the textile webs 33, 35 forming an angled edge between the stamp and the counter-holder. At the same time, the cutting starts. This can also be done subsequently with a separate laser cutter. Here, the joining of the half-shells, for example by welding, flanging or gluing, and the separation of excess material can be combined into one process step.

The exemplary embodiment of prefabricated protective sleeves shown in FIG. 6 has a lower textile web 37. Several textile pieces 39 are attached to this side by side by means of a U-shaped peripheral seam 41 in the form of tubular open pockets for receiving the stator coils 18, 20. The stator coils 18, 20 can be inserted into these pockets in order to be fed to a punch or a welding device in a manner similar to an ammunition belt in the subsequent processing and thus to obtain a dimensionally accurate protective cover by assembly line production. In a modified method, an endless fabric tube can be pulled through the center of the stator coil 18, 20. A piece of the fabric hose is pulled over the outer circumference of the stator coil 18, 20 and connected by means of a single weld seam to the tightened piece of fabric hose encompassing the stator coil 18, 20 from the inside. This variant of the method can also be adapted to production line production.

According to FIG. 7, an endless fabric hose 43 can also be filled in the longitudinal direction with stator coils 18, 20 in succession. The filled tube sections are then separated one after the other, punched out and the separating edges and the punched edges welded shut. Only two outer weld seams 47 and one inner weld seam 45 are necessary here. The electrical connection wires 21 can be guided through the fabric hose 43 to the outside.

A further variant of the method according to FIG. 7 consists in inserting the stator coils as described in an endless tube cut on its longitudinal side or in a textile web angled on the longitudinal side and then closing the protective cover 23 by one outer longitudinal seam and two outer transverse seams.

The contradiction to be resolved between the desired, good thermal conductivity and poor electrical conductivity is solved by particularly thin, but high-strength textile material.

An advantageous exemplary embodiment of the invention results if, before the protective sheath 23 is applied to the stator coils 18, 20, these are coated with a layer of baked enamel wire and the protective sheath is also previously impregnated with baked enamel wire.

Claims

Expectations

1. Hand tool, in particular angle grinder (1), with internally ventilated electric motor (5), the motor parts of which are wound in a coil-like manner from a large number of wire windings, in particular the rotor (13) and each of the stator coils (18, 20) of the stator (11 ), each surrounded by at least one protective cover (23), characterized in that each protective cover (23) consists of at least two interconnected partial or half shells (24, 25).

2. Hand tool according to claim 1, characterized in that the half-shells (24, 25) are placed on top of one another in mirror-image fashion and are connected to one another at their angled, joint-like edges.

3. Hand tool according to claim 2, characterized in that the joint-like edges run in an antiline manner along the enveloped motor parts and carry a connecting weld seam (27, 31).

4. Hand tool according to claim 2, characterized in that the abutting edges carry a connecting seam or flare or Ver¬ entanglement or adhesive.

5. Hand tool according to claim 3 or 4, characterized gekennzeich¬ net that electrical connecting wires (21) pass between the half-shells (24, 25).

6. Hand tool according to claim 3 or 4, characterized gekennzeich¬ net that the protective cover (23) made of ultrasonically weldable textile material, such as. Carbon fiber-glass fiber mixture exists.

7. Hand tool according to claim 3, characterized in that the protective cover (23) is thin-walled and of high thermal conductivity.

8. Hand tool according to claim 7, characterized in that two superimposed textile webs (23, 35) are connected with seams running along their length, so that tubular protective sleeves (23) are formed to accommodate motor parts.

9. Hand tool according to the preamble of claim 1, characterized in that the protective cover (23) in the form of a Gewescheschlau¬ ches tightly over the stator coils (18, 20) and / or the rotor (13) is pulled ge.

10. Hand tool according to claim 9, characterized in that the protective sheath (23) is drawn in the form of the fabric hose soaked with baked enamel over the baked enamel coated stator coils (18, 20) or the baked enamel coated rotor (13).