Machine tool having a one-piece transmission housing

Abstract

The present invention relates to a machine tool (100) comprising the following: an electric motor (120) having a rotor and a stator; a transmission (140) which is operatively connected to the rotor of the motor and is received in a transmission housing (142) of the machine tool (100), wherein the transmission housing (142) has a cavity for receiving the transmission and a connecting wall (144), wherein the connecting wall (144) is formed in one piece with the transmission housing (142) and faces the motor, and wherein the connecting wall has a first recess, in particular depression, for receiving a rotor bearing.

Description

[0001] Hilti Aktiengesellschaft in Schaan

[0002] Principality of Liechtenstein

[0003] Machine tool with one-piece gearbox housing

[0004] The present invention relates to a machine tool with an electric motor and a gearbox connected to the motor.

[0005] Background of the invention

[0006] Electric motors, such as those used to drive a machine tool, typically have a bearing plate to hold and support a ball bearing. This ball bearing supports one end of a rotor shaft and is therefore also called a rotor bearing. The rotor shaft protrudes from the laminated core of the electric motor and transmits the torque generated by the motor to other components, such as an attached gearbox.

[0007] The machine tool's gearbox is housed in a gearbox casing. The gearbox casing has a cavity for the gearbox with its gears, shafts, and bearings. This cavity is shaped like a pot, while the aforementioned rotor bearing, acting as a link between the motor and gearbox, is located in the end shield. The end shield is a type of cover that is detachably connected to the pot-shaped gearbox casing. When the gearbox casing is bolted to the end shield, the motor pinion, guided in the rotor bearing, engages with the gearbox and can drive it.

[0008] The function of the bearing shield is therefore to adequately fix the rotor bearing in its position and, on the other hand, to seal the cup-shaped (open) gearbox chamber. For this purpose, the contact surfaces of the bearing shield with the gearbox housing can be sealed using physical sealants (e.g., sealing cord) or without any component, e.g., via a labyrinth seal.

[0009] To ensure the rotor bearing is mounted with sufficient precision and stability, the bearing shield must be manufactured as a post-machined die-cast part. This makes the component complex and expensive. Furthermore, seals and screws are typically required, which further increase costs and assembly effort.

[0010] Based on the above-mentioned problem, it is an object of the present invention to provide a machine tool or a gearbox housing which can be manufactured and assembled in a simple and cost-effective manner.

[0011] The problem is solved by the subject matter of the independent claims. Advantageous embodiments relating to the subject matter of the independent claims are found in the dependent claims.

[0012] Accordingly, the present invention relates to a machine tool comprising: an electric motor with a rotor and a stator; a gearbox which is operatively connected to the rotor of the motor and is housed in a gearbox housing of the machine tool, wherein the gearbox housing has a cavity for receiving the gearbox and a connecting wall, wherein the connecting wall is formed integrally with the gearbox housing and faces the motor, and wherein the connecting wall has a first recess, in particular a depression, for receiving a rotor bearing.

[0013] The one-piece forming of the connecting wall, which is part of the gearbox housing, eliminates the need for the aforementioned bearing shield. This results in significant cost savings in manufacturing, and the inventive solution also eliminates the need for additional seals and screws for attaching a bearing shield. Furthermore, the seamless design of the connecting wall creates a particularly stable mounting for the rotor bearing.

[0014] According to a further embodiment, the first recess is designed to support a first partial area of ​​the rotor bearing, wherein the first partial area comprises less than 80% of the rotor bearing's outer circumference, preferably about 75%. In other words, this embodiment proposes supporting only a portion of the rotor bearing through the connecting wall. It has been found that a partial area of ​​more than 60% of the outer circumference is sufficient to adequately support the rotor bearing. Simultaneously, this embodiment allows for an overlapping area with a further recess in the unsupported portion of the rotor bearing, the further recess being designed to accommodate a gear wheel that is in contact with the motor pinion. For example, the outer circumference of the cylindrical rotor bearing can be supported by the recess along a circular arc corresponding to 270° to 330°.In other words, one side wall of the recess is semi-annular and covers a circular arc with an angle of 270° to 330°.

[0015] According to a further embodiment, the connecting wall has a motor pinion receptacle which extends from the first recess towards the cavity and is designed to receive a motor pinion connected to the rotor. The motor pinion receptacle can, in particular, be designed such that the motor pinion is in contact with a gear wheel also received in the connecting wall.

[0016] According to a further embodiment, the connecting wall has a second recess, in particular a depression, for receiving a gear wheel, and the second recess is arranged parallel to the first recess. The second recess can be open on the side facing the motor, so that the gear wheel can be removed and reinstalled quickly and easily.

[0017] In another embodiment, the connecting wall has an opening that extends through the second recess into the cavity. The second recess can therefore not only serve to accommodate a gear wheel. Rather, according to this example, the second recess can be used to mount the gearbox. For example, a gearbox shaft can be inserted into the cavity through the opening and connected to other parts of the gearbox (e.g., bevel gears) to transmit a rotary motion of the rotor to the gearbox.

[0018] In another embodiment, the first and second recesses overlap. The first and second recesses can be cylindrical and intersect in the space between them. This overlap allows contact between the motor pinion and the gear wheel to be established within the connection wall. The connection wall thus defines the input area of ​​the gearbox. In a further embodiment, a second section of the rotor bearing is accommodated in the second recess.

[0019] According to another embodiment, the machine tool has a cover designed to conceal the second recess. This cover protects the interior (cavity) of the gearbox housing from environmental influences and prevents lubricants from escaping. It was found that the first recess in the connecting wall provides a sufficiently stable support for the rotor bearing. Therefore, the cover of the second recess does not play a load-bearing role; it merely serves to conceal the cavity of the gearbox housing.

[0020] In a further embodiment, the cover has a side surface, preferably arcuate, which is designed to support a second sub-area of ​​the rotor bearing, wherein the second sub-area comprises less than 30% of the outer surface of the rotor bearing, preferably about 25% of the outer surface. According to this embodiment, the cover also serves to support the rotor bearing.

[0021] In another embodiment, the cover is attached to the connection wall by the rotor, in particular by a retaining ring and / or the rotor bearing. The cover can therefore be removed with just a few simple steps, for example to service or repair the gearbox.

[0022] In another embodiment, the cover is made of plastic. This makes the cover particularly cost-effective and allows for manufacturing with tight tolerances. Furthermore, the plastic construction allows the cover to be easily used as a seal for the gearbox housing. Preferably, no additional sealing materials, such as rubber O-rings or similar components, are required.

[0023] In a further embodiment, the second recess has a groove, in particular an annular groove, for attaching the cover. The cover can have at least one snap hook for releasably connecting the cover to the groove of the second recess. Thus, no additional tools are necessary to connect the cover to the second recess. Instead, it can simply be pressed into the second recess, whereupon the snap hooks automatically engage in the annular groove. To release the cover, the snap hooks can be provided with extensions that make it possible to release the snap hooks from the annular groove and remove the cover.

[0024] According to another embodiment, the cover has semicircular ribs on a surface facing the motor.

[0025] According to another embodiment, the connecting wall has semicircular ribs on a surface facing the motor.

[0026] According to another embodiment, the machine tool is an angle grinder.

[0027] Another aspect of the present invention relates to a gearbox housing for machine tools, wherein the gearbox housing has a cavity for receiving the gearbox and a connecting wall, wherein the connecting wall is formed integrally with the gearbox housing and faces the motor, and wherein the connecting wall has a first recess, in particular a depression, for receiving a rotor bearing.

[0028] Further advantages arise from the following description of the figures. The figures, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0029] They show:

[0030] Fig. 1 shows a side view of a machine tool according to an embodiment of the present invention;

[0031] Fig. 2 is an exploded view of the gearbox and motor of the machine tool according to Fig. 1;

[0032] Fig. 3 shows an enlarged view of the gearbox housing according to Fig. 2.

[0033] Detailed Description Figure 1 shows a side view of a machine tool 100 according to an embodiment of the present invention. The machine tool according to Figure 1 is, for example, a cut-off grinding machine. However, it should be mentioned at this point that the present invention is not limited to cut-off grinding machines. Rather, the present invention can generally be applied to any electric machine tool if it includes a gearbox.

[0034] The machine tool 100 has a gear unit 102, which is arranged between a handle 104 and a cutting disc 110. In the embodiment shown here, the machine tool 100 is specifically battery-operated, i.e., equipped with a battery 106. The battery 106 is detachably connected to the machine tool 100. Naturally, the machine tool 100 can have one or more batteries. A protective hood 108 can be arranged over a segment of the cutting disc 110.

[0035] The machine tool 100 has an electric motor which is connected to an output shaft 112 via the gearbox 102. In the embodiment shown here, the machine tool has, for example, a bevel gear transmission arranged between the motor and the output shaft 112. The electric motor is supplied with electrical energy by the accumulator 106. The machine tool 100 can be operated via a switch formed on the handle 104.

[0036] A schematic exploded view of the electric motor and the associated gearbox section is shown in Figure 2. The machine tool 100 has a gearbox 140 arranged in the gearbox section 102, with a gearbox housing 142. The gearbox housing 142 is shown in Figure 2 mainly from its rear side, i.e., the side facing the motor 120. The gearbox housing 142 is essentially a single piece, as will be explained in more detail later. For example, a bevel gear is arranged in the part of the gearbox housing 142 not shown, which transmits the rotation of the motor's rotor shaft 122 to the output shaft 112.

[0037] Inside the gearbox housing 142, a cavity is formed to accommodate the gearbox. The gearbox is thus protected from environmental influences within the gearbox housing 142 and can be lubricated with suitable lubricants. A connecting wall 144 is located on the rear side of the gearbox housing 142, i.e., on the side facing the motor 120. The connecting wall 144 is integrally formed with the gearbox housing 142. In other words, the connecting wall 144 forms part of the gearbox housing 142 that separates the cavity from the motor 120. According to the invention, a rotor bearing 126 of the motor is arranged in the connecting wall 144.

[0038] The rotor bearing 126 is connected to the rotor shaft 122. A motor pinion 128 is arranged on one side of the rotor bearing 126 facing away from the rotor shaft 122. The motor pinion drives the gearbox. For this purpose, the motor pinion 128, when installed, is in operative engagement with a gear wheel 146 of the gearbox. According to the embodiment shown in Figures 2 and 3, the gear wheel 146 is also mounted in the connecting wall 144. A rotary motion of the gear wheel 146 can be transmitted, for example, via a transmission shaft 148 to a bevel gear unit (not shown).

[0039] As can be seen particularly from the enlarged view in Figure 3, the connecting wall 144 has a first recess 147. The first recess 147 is a depression located in the connecting wall 144 and open towards the motor. The first recess 147 serves to accommodate the rotor bearing 126 of the motor 120. The first recess forms a seating surface 152, which serves as a stop for a cover 130, as will be explained in more detail below.

[0040] A motor pinion receptacle 150 extends from the seat surface 152 towards the cavity of the gearbox housing 142. Specifically, the motor pinion receptacle 150 is also a recess located in the connecting wall, which adjoins the first recess 147. The motor pinion receptacle 150 supports the motor pinion 128 of the rotor bearing in such a way that it is freely rotatable within the recess of the motor pinion receptacle 150.

[0041] The connecting wall 144 also has a second recess 149. The second recess 149 is a depression located in the connecting wall 144 and open towards the motor. The second recess 149 serves to receive the gear wheel 146. The second recess forms a seat 146, which serves as a shoulder for the gear wheel 146, as can be seen particularly in Fig. 2. The seat 156 is located at the level of the motor pinion receptacle 150. The seat 156 of the second recess 149 is arranged in a plane parallel to the plane of the first seat 152 of the first recess 147. In particular, the second seat 156 is arranged in a plane that is further away from the motor 120 than the plane of the first seat 152.

[0042] The motor pinion 128, when installed, is arranged in the same plane as the gear wheel 146. The first and second recesses are cylindrical and partially overlap. The motor pinion 128 engages with the gear wheel 146 in the area of ​​overlap between the two recesses 147 and 149.

[0043] The second recess 149 has an opening, in particular a through-opening 154. The through-opening 154 extends from the second seating surface 156 into the cavity of the gearbox housing 142. The through-opening is designed such that the gearbox shaft 148 can extend through the through-opening 154 into the cavity. Preferably, the gearbox shaft 148 can be mounted directly in the cavity via the through-opening 154. For example, the gearbox shaft 148 can be connected via the through-opening 154 to a bevel gear unit (not shown) of the gearbox 140.

[0044] A cover 130 serves to cover the through-opening 154 and thus seal the cavity of the gearbox housing 142. The cover 130 can, for example, be made of plastic. The cover 130 can seal the cavity of the gearbox housing preferably without additional sealing materials such as sealing rings or the like. The cover has a diameter that essentially corresponds to the diameter of the second recess 149. After the gear wheel 146 has been installed, the cover 130 is inserted into the second recess 149 and detachably connected to it. For example, the cover 130 can have one or more snap hooks 162a, 162b, 162c, which engage in an annular groove 158 of the second recess 149 when the cover is inserted.

[0045] The cover 130 is essentially cylindrical, with a circular segment falling within the overlapping area of ​​the two recesses 147, 149 forming a negative shape relative to the rotor bearing 126. In other words, the cover 130 has a concave side surface 131 (Fig. 2) with a radius that essentially corresponds to the radius of the rotor bearing 126. When installed, the side surface 131 of the cover 130 serves to support a portion, for example, about 25% of the outer surface, of the rotor bearing 126. The side surface 131 thus serves as a bearing surface for a portion of the rotor bearing 126. However, a large part of the outer surface of the rotor bearing 126 is supported by the first recess 149. In the embodiment shown here, the inner wall of the first recess 149 surrounds about 75% of the outer surface of the rotor bearing 126.It was determined that a contact area of ​​75% of the outer surface is sufficient to adequately support the rotor bearing. This 75% is formed by the integral connecting wall 144, which is made of metal and thus provides the necessary stability for the rotor bearing 126.

[0046] Accordingly, the cover 130 serves on the one hand to cover the through-opening 154. On the other hand, the cover 130 is designed to surround and thus support a part of the rotor bearing 126.

[0047] The cover 130 has a rim 132 with a through-opening 138. In its installed state, the rim 132 extends from the side surface 131 towards the first recess 147. The rim is dimensioned such that it corresponds to the dimensions of the seating surface 152 of the first recess 147. The through-opening has a diameter that essentially corresponds to the diameter of the motor pinion receptacle 150.

[0048] Alignment means 134, 136 are arranged on the outer circumference of the rim 132. The alignment means 134, 136 extend radially from the outer circumference of the rim 132. The alignment means are designed to be complementary to alignment notches 168 of the seat surface 152. This simplifies the correct insertion of the cover 130 into the first recess 147.

[0049] The alignment means 134, 136 also facilitate the fastening of the cover 130 in the recesses 147, 149. Reference is made here to the exploded view in Fig. 2. The cover 130 is thus inserted into the recesses 147, 149 in front of the rotor bearing 126. The motor pinion 128 extends through the opening 138 of the rim 132, while the rotor bearing 126 sits at least partially on the rim 132. A retaining ring 124 engages in an annular groove 159 of the first recess 147 and thus presses the rotor bearing 126 onto the rim 132, thereby anchoring the cover 130 in the recesses 147, 149.

[0050] The connecting wall 144 has semicircular ribs 160a, 160b, 160c, 160d, which are arranged on a side of the connecting wall 144 facing the motor. The ribs 160a, 160b, 160c, 160d serve to guide the airflow of a fan (not shown here). The ribs 160a, 160b, 160c, 160d are arranged concentrically around the first recess 147. The ribs 160a, 160b, 160c, 160d extend, for example, along a three-quarter circular path, which is interrupted only by the second recess 149. The cover has semicircular ribs 164a, 164b, 164c, 164d, which are arranged on a surface 166 of the cover 130 facing the motor. The ribs 164a, 164b, 164c, 164d are arranged concentrically around the first recess 147. The ribs 164a, 164b, 164c, 164d extend, for example, along a quarter-circle path. The ribs 164a, 164b, 164c, 164d of the cover 130 are complementary to the ribs 160a, 160b, 160c, 160d of the connecting wall 144.In other words, ribs 164a, 164b, 164c.

[0051] 164d of the cover 130 together with the ribs 160a, 160b, 160c, 160d of the connecting wall 144 form circular ribs which extend concentrically around the first recess 147.

[0052] Reference symbol list

[0053] 100 machine tools

[0054] 102 Drive area

[0055] 104 Grip area

[0056] 106 battery

[0057] 108 Protective cover

[0058] 110 T cutting disc

[0059] 112 disc axle

[0060] 120 engine

[0061] 122 Rotor shaft

[0062] 124 retaining ring

[0063] 126 rotor bearings

[0064] 128 motor pinion

[0065] 130 Coverage

[0066] 131 side surface

[0067] 132 wreath

[0068] 134, 136 Alignment aids

[0069] 138 Passage opening

[0070] 140 gearbox

[0071] 142 Gearbox housing

[0072] 144 Connection wall

[0073] 146 Gear wheel

[0074] 147 first exception

[0075] 148 Input shaft

[0076] 149 second exception

[0077] 150 Motor pinion mount

[0078] 152 Seating area

[0079] 154 Opening

[0080] 156 Seating area

[0081] 158 Ring groove

[0082] 160a, 160b, 160c, 160d ribs

[0083] 162a, 162b, 162c Snap hook

[0084] 164a, 164b, 164c, 164d Ribs

[0085] 166 Surface 168 Alignment notch

Claims

Patent claims 1. Machine tool (100) comprising the following: - an electric motor (120) with a rotor and a stator; - a gearbox (140) which is operatively connected to the rotor of the motor (120) and is received in a gearbox housing (142) of the machine tool (100), wherein the gearbox housing (142) has a cavity for receiving the gearbox and a connecting wall (144), wherein the connecting wall (144) is formed integrally with the gearbox housing (142) and faces the motor (120), and wherein the connecting wall (144) has a first recess (147), in particular a depression, for receiving a rotor bearing (126).

2. Machine tool (100) according to claim 1, wherein the first recess (147) is configured to support a first partial area of ​​the rotor bearing (126), wherein the first partial area comprises less than 80% of an outer circumference of the rotor bearing (126), preferably about 75% of the outer circumference.

3. Machine tool (100) according to claim 1 or 2, wherein the connecting wall (144) has a motor pinion receptacle (150) which extends from the first recess (147) in the direction of the cavity and is designed to receive a motor pinion (128) connected to the rotor.

4. Machine tool (100) according to one of claims 1 to 3, wherein the connecting wall (144) has a second recess (149), in particular a depression, for receiving a gear wheel (146), and wherein the second recess (149) is arranged parallel to the first recess (147).

5. Machine tool (100) according to claim 4, wherein the connecting wall (144) has an opening (154) which extends through the second recess (149) into the cavity.

6. Machine tool (100) according to claim 4 or 5, wherein the first and second recesses (149) are cylindrical and the first and second recesses (147, 149) overlap at least partially.

7. Machine tool (100) according to one of claims 4 to 6, wherein a second part of the rotor bearing (126) is received in the second recess (149).

8. Machine tool (100) according to one of claims 4 to 7, wherein the machine tool (100) has a cover (130) which is designed to cover the second recess (149).

9. Machine tool (100) according to claim 8 in combination with claim 2, wherein the cover (130) has a, preferably arc-shaped, side surface (131) which is designed to support a second partial area of ​​the rotor bearing (126), wherein the second partial area comprises less than 30% of the outside of the rotor bearing (126), preferably about 25% of the outside.

10. Machine tool (100) according to claim 8 or 9, wherein the cover (130) is attached to the connecting wall (144) by the rotor, in particular by a retaining ring (124) and / or the rotor bearing (126) of the rotor.

11. Machine tool (100) according to one of claims 8 to 10, wherein the cover (130) is made of plastic.

12. Machine tool (100) according to one of claims 8 to 11, wherein the second recess (149) has a groove, in particular annular groove (158), for fastening the cover (130), and wherein the cover (130) preferably has at least one snap hook (162a, 162b, 162c) for releasably connecting the cover (130) to the groove of the second recess (149).

13. Machine tool (100) according to one of claims 8 to 12, wherein the cover (130) has semicircular ribs (164a, 164b, 164c, 164d) on a surface facing the motor (120).

14. Machine tool (100) according to one of claims 1 to 13, wherein the connecting wall (144) has semicircular ribs (160a, 160b, 160c, 160d) on a surface facing the motor (120).

15. Machine tool (100) according to one of claims 1 to 14, wherein the machine tool (100) is an angle grinder.

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