Gear box body, gear box of machining center and machining center

Abstract

The utility model relates to the field of gear box body structures, in particular to a gear box body, a gear box of a machining center and the machining center, which comprises a box body, a first end face of the box body comprises a first axial face and a second axial face, the first axial face is provided with a first shaft hole for installing an input shaft, and the second axial face is provided with a second shaft hole for installing an output shaft. According to the gear box, the step structures of the first axial surface and the second axial surface are arranged, so that the distance between the second axial surface and the fourth axial surface is shortened in the gear box with the same size specification, the distance between the two shaft holes used for installing the output shaft is further shortened, and therefore the shorter output shaft can be used to reduce vibration of the gear box.

Description

Technical Field

[0001] The utility model relates to the field of gear box structure, in particular to a gear box, a gear box of a machining center and a machining center. Background Art

[0002] In the operation process of the existing gearbox, the length of the shaft will affect the vibration of the gearbox. The longer the shaft is, the more likely it is that the gearbox will vibrate too much. For example, in the Chinese patented combined speed gearbox (patent number CN203272638U), the distance from one end face to the other opposite end face of the housing (equivalent to the box body of the present application) is roughly equal. This structure is prone to cause gearbox vibration due to the excessive length of the output shaft.

[0003] Therefore, how to make the output shaft in a certain specification of gearbox shorter is of great significance to reducing the vibration of the gearbox and improving the rigidity of the output shaft. Utility Model Content

[0004] To solve the above problems, the purpose of the utility model is to provide a gear box body, a gear box for a machining center and a machining center. Under a gear box of a certain specification, the distance between two holes for installing the output shaft is shortened to reduce the length of the output shaft and reduce the vibration of the gear box.

[0005] The purpose of this utility model is achieved through the following technical solutions:

[0006] The utility model provides a gear box body, comprising: a box body with a cavity inside, the box body comprising a first end face and a second end face opposite to each other, the first end face comprising a first axial face and a second axial face, the second end face comprising a third axial face and a fourth axial face, the first axial face is provided with a first axial hole for installing an input shaft, the second axial face is provided with a second axial hole for installing an output shaft, a third axial hole for inserting a transmission shaft is provided between the first axial hole and the second axial hole, and the fourth axial face is provided with a first through hole coaxial with the second axial hole;

[0007] The first axial surface and the second axial surface are arranged in steps, and the first axial surface is higher than the second axial surface. The third axial surface and the fourth axial surface are arranged in steps, and the third axial surface is higher than the fourth axial surface.

[0008] In one embodiment, a fifth axial surface located between the first axial surface and the second axial surface is provided on the first end surface, and the first axial surface, the fifth axial surface and the second axial surface are arranged in steps from high to low; and the third axial hole is arranged on the fifth axial surface.

[0009] In one embodiment, a fourth axial hole coaxial with the second axial hole is provided in the box body.

[0010] In one embodiment, a sixth axial surface located between the third axial surface and the fourth axial surface is disposed on the second end surface, and the third axial surface, the sixth axial surface and the fourth axial surface are arranged in steps from high to low; and / or,

[0011] A straight-line distance from the second axial plane to the fourth axial plane is smaller than a straight-line distance from the first axial plane to the third axial plane.

[0012] In one embodiment, the hole wall of the first shaft hole is provided with a first bearing portion for bearing the bearing, and the hole wall of the second shaft hole is provided with a second bearing portion for bearing the bearing.

[0013] In one embodiment, a fifth axial hole coaxial with the first axial hole is provided in the box body, a sixth axial hole coaxial with the third axial hole is provided in the box body, the aperture of the first axial hole is not smaller than the aperture of the fifth axial hole, the aperture of the second axial hole is not smaller than the aperture of the fourth axial hole, and the aperture of the third axial hole is not smaller than the aperture of the sixth axial hole.

[0014] In one embodiment, reinforcing ribs are provided on the inner wall of the cavity; and / or,

[0015] An axle seat is arranged in the cavity of the box body, the fifth axle hole is located on the axle seat, and an oil hole arranged in the direction from the first axle surface to the second axle surface is arranged at the bottom of the axle seat, the oil hole includes a first oil hole, a second oil hole and a third oil hole which all pass through the axle seat, wherein the first oil hole is a runway-shaped structure and passes through the fifth axle hole, and the second oil hole and the third oil hole are located on both sides of the first oil hole;

[0016] A bearing plate is arranged in the box body, the fourth axial hole and the sixth axial hole are arranged on the bearing plate, and the surface for mounting the shaft seat is coplanar with the bearing plate.

[0017] A gearbox for a machining center comprises an input shaft, a transmission shaft, an output shaft and a gearbox body as described in any one of the above items, which are connected in sequence with gears, wherein the input shaft is inserted in the first shaft hole, the transmission shaft is inserted in the third shaft hole, and the output shaft is inserted in the second shaft hole and the fourth shaft hole and passes through the first through hole.

[0018] In one embodiment, the input shaft is provided with a first gear, the transmission shaft is provided with a second gear and a third gear respectively, the pitch circle diameter of the second gear is larger than that of the third gear, the output shaft is provided with a fourth gear and a fifth gear respectively, the pitch circle diameter of the fourth gear is smaller than that of the fifth gear;

[0019] The second gear is meshed with the first gear. In a first meshing state, the second gear is meshed with the fourth gear, and the third gear is disengaged from the fifth gear. In a second meshing state, the second gear is disengaged from the fourth gear, and the third gear is meshed with the fifth gear. The gearbox achieves speed change by switching between the first meshing state and the second meshing state.

[0020] A machining center comprises the gear box of the machining center described above.

[0021] The beneficial effect of the utility model is that the first end surface of the box body includes a first axial surface and a second axial surface, the first axial surface is provided with a first axial hole for installing the input shaft, and the second axial surface is provided with a second axial hole for installing the output shaft. Through the step structure setting of the first axial surface and the second axial surface, in a gearbox with the same size specification, the distance from the second axial surface to the fourth axial surface is shortened, thereby shortening the distance between the two axial holes for installing the output shaft, so that a shorter output shaft can be used on the second axial hole and the fourth axial hole to reduce the vibration of the gearbox. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0023] Figure 1 It is a structural diagram of the box body of the utility model;

[0024] Figure 2 It is a cross-sectional structural diagram of the box body of the utility model;

[0025] Figure 3 It is a structural schematic diagram of the gear box of the utility model;

[0026] Figure 4 It is another cross-sectional structural diagram of the box body of the utility model.

[0027] The accompanying drawings are denoted as follows:

[0028] 1-box body, 2-first end face, 3-second end face;

[0029] 4-first axial plane, 5-second axial plane, 6-third axial plane, 7-fourth axial plane, 8-fifth axial plane;

[0030] 9-first axial hole, 10-second axial hole, 11-fourth axial hole, 12-third axial hole, 13-fifth axial hole, 14-sixth axial hole, 15-first through hole, 16-second through hole;

[0031] 17-reinforcement rib, 18-axle seat, 19-first oil hole, 20-second oil hole, 21-third oil hole;

[0032] 22-input shaft, 23-transmission shaft, 24-output shaft, 25-first bearing part, 26-second bearing part;

[0033] 27 - first gear, 28 - second gear, 29 - third gear, 30 - fourth gear, 31 - fifth gear, 32 - carrying plate. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0035] In order to make the vibration of the gearbox of the same specification less affected by the shaft length, it is necessary to make the shaft length of the gearbox of the specification as short as possible. In addition, shortening the length of the output shaft is conducive to improving the rigidity of the output shaft, and improving the rigidity is conducive to reducing the vibration of the gearbox. Therefore, the present application provides a gearbox body with a shorter output shaft stroke.

[0036] refer to Figure 1 to Figure 2 The utility model provides a gear box body, comprising: a box body 1 with a cavity inside, the box body 1 is in a square structure, including a first end face 2 and a second end face 3 opposite to the first end face 2, a first axial face 4 and a second axial face 5 in a stepped structure are arranged on the first end face 2, and the first axial face 4 is higher than the second axial face 5, and the second end face 3 includes a third axial face 6 and a fourth axial face 7 in a stepped structure, and the third axial face 6 is higher than the fourth axial face 7 (herein, reference Figure 1direction), the first axial surface 4 is arranged opposite to the third axial surface 6, and the second axial surface 5 is arranged opposite to the fourth axial surface 7. A first axial hole 9 for installing the input shaft 22 is arranged on the first axial surface 4, a second axial hole 10 is arranged on the second axial surface 5, and a fourth axial hole 11 coaxial with the second axial hole 10 is arranged in the box body 1, and a first through hole 15 coaxial with the second axial hole 11 is arranged on the fourth axial surface 7. The second axial hole 10, the fourth axial hole 11 and the first through hole 15 are used to insert the output shaft 24, and the output shaft 24 extends from the box body 1 through the first through hole 15. By arranging the first axial surface 4 and the second axial surface 5 in a step-like manner, in the gearbox of the same size, the distance from the second axial surface 5 to the fourth axial surface 7 is shortened, thereby shortening the distance between the two axial holes (the second axial hole 10 and the fourth axial hole 11) for installing the output shaft 24, so that a shorter output shaft 24 can be used on the two axial holes to reduce the vibration of the gearbox. In the gearbox of the same size, Figure 3 A shorter output shaft 24 can be used in the box body 1. A relatively shorter output shaft 24 is easier to process, lighter, and reduces costs; the shorter bearing spacing also improves the rigidity of the output shaft 24. High rigidity means high natural frequency, and a structure with a high natural frequency is not easy to resonate.

[0037] In one embodiment, reference Figure 1 and Figure 2 A third axial hole 12 for inserting a transmission shaft 18 is provided between the first axial hole 9 and the second axial hole 10. The third axial hole 12 can be provided on the first axial surface 4 or the second axial surface 5 as required.

[0038] Preferably, reference Figure 1 and Figure 2 The first end surface 2 is provided with a fifth axial surface 8 located between the first axial surface 4 and the second axial surface 5. The first axial surface 4, the fifth axial surface 8 and the second axial surface 5 are arranged in steps from high to low; the third axial hole 12 is arranged on the fifth axial surface 8. By setting the three-step arrangement, the distance between the upper and lower end surfaces of the box body 1 is shortened, so that a shorter transmission shaft 18 can be installed in the third axial hole 12.

[0039] For further reference, Figure 1 and Figure 2 The second end surface 3 is provided with a sixth axial surface located between the third axial surface 6 and the fourth axial surface 7, and the third axial surface 6, the sixth axial surface and the fourth axial surface 7 are arranged in steps from high to low (with Figure 1The second end surface 3 is set as a three-step setting, which can further shorten the straight-line distance between the fifth axial surface 8 and the sixth axial surface, and shorten the straight-line distance between the first axial surface 4 and the third axial surface 6, so that a shorter shaft can be installed on the third axial hole 12 and the first axial hole 9, further reducing the vibration of the gear box.

[0040] Further in, refer to Figure 1 and Figure 2 , the straight-line distance from the second axial surface 5 to the fourth axial surface 7 is smaller than the straight-line distance from the first axial surface 4 to the third axial surface 6, so that the length of the output shaft 24 can be set shorter if the needs are met.

[0041] In one embodiment, reference Figure 1 and Figure 2 , the first bearing position includes a coaxial first axial hole 9 and a fifth axial hole 13. The first axial hole 9 is a through hole that penetrates the first end face 2 to the cavity in the box body 1. A first bearing part 25 for bearing the bearing is arranged on the hole wall of the first axial hole 9. The first bearing part 25 is an annular structure protruding from the inner wall of the first axial hole 9. In the prior art, a bearing seat is arranged at the position of the first axial hole 9. The purpose of setting the bearing seat is to support the bearing. In this embodiment, the first bearing part 25 is directly arranged on the inner wall of the first axial hole 9. When installing the input shaft 22, there is no need to use a bearing seat. The input shaft 22 passes through the bearing, and then the bearing is installed on the first bearing part 25. This arrangement eliminates the use of the bearing seat, saves the step of installing the bearing seat, and saves the cost of the bearing seat.

[0042] The fifth shaft hole 13 is arranged in the cavity. The input shaft 22 passes through the first shaft hole 9 and is inserted into the fifth shaft hole 13. The fifth shaft hole 13 supports and positions the input shaft 22. In actual work, the supporting force for the input shaft 22 is avoided to be provided by the box part at the first shaft hole 9.

[0043] In one embodiment, reference Figure 1 and Figure 2 The second bearing position passes through the box body 1 to form two coaxial axial holes for installing the output shaft 24. The two axial holes are the second axial hole 10 and the fourth axial hole 11. The second axial hole 10 is located on the second axial surface 5, and the fourth axial hole 11 is located on one side of the second end surface 3. After the output shaft 24 passes through the second bearing position, its two ends are correspondingly located in the second axial hole 10 and the fourth axial hole 11, and the output end of the output shaft 24 extends out of the box body 1 from the fourth axial hole 11, and the output end is connected to the external structure to drive the external structure to move.

[0044] The second bearing portion 26 for bearing the bearing is provided on the hole wall of the second shaft hole 10. When installing the output shaft 24, there is no need to use a bearing seat. The output shaft 24 passes through the bearing, and then the bearing is installed on the second bearing portion 26. The second bearing portion 26 supports and positions the bearing of the output shaft 24. This arrangement eliminates the use of the bearing seat, saves the steps of installing the bearing seat, and saves the cost of the bearing seat.

[0045] In one embodiment, reference Figure 1 and Figure 2 A third axial hole 12 penetrating into the cavity of the box body 1 is provided on the first end surface 2, and a sixth axial hole 14 penetrating into the cavity of the box body 1 is provided on the second end surface 3. The third axial hole 12 and the sixth axial hole 14 are coaxial.

[0046] In the prior art, due to the structure of the box body 1 itself, when processing the bearing position (including the first shaft 9 hole to the sixth shaft hole 14), it can only be processed from top to bottom. In the processing of the box body 1, the five holes of the first shaft hole 9 and the fifth shaft hole 13 for installing the input shaft 22, the second shaft hole 10 and the fourth shaft hole 11 for installing the output shaft 24, and the third shaft hole 12 for installing the transmission shaft 23 can be clamped and processed at one time. However, since the aperture of the third shaft hole 12 is much smaller than the aperture of the sixth shaft hole 14, the tool cannot pass through the third shaft hole 12 to process the sixth shaft hole 14, so it is necessary to clamp twice or use a machine tool with a turntable to move the tool again to process the sixth shaft hole 14, which makes the processing inconvenient, that is, the prior art cannot complete the processing of the above six holes by clamping at one time.

[0047] In order to solve the problem that the six holes of the bearing position and the guide installation position cannot be conveniently processed at one time, the aperture of the first shaft hole 9 is set to be not less than the aperture of the fifth shaft hole 13, and preferably the first shaft hole 9 is larger than the aperture of the fifth shaft hole 13; the aperture of the second shaft hole 10 is not less than the aperture of the fourth shaft hole 11, and preferably the second shaft hole 10 is larger than the aperture of the fourth shaft hole 11; the third shaft hole 12 is not less than the sixth shaft hole 14, and preferably the aperture of the third shaft hole 12 is larger than the aperture of the sixth shaft hole 14. Therefore, during processing, the six holes of the bearing position and the guide installation position can be processed from top to bottom, and the six holes of the bearing position and the guide installation position can be processed in one clamping. A second through hole 16 coaxial with the sixth through hole 14 is provided on the second end face 3, and a cover plate is provided on the second through hole 16 to close the box body 1, and the transmission shaft 23 is connected to the cover plate against the top.

[0048] In one embodiment, reference Figure 2 A reinforcing rib 17 is arranged on the inner wall of the cavity. The arrangement of the reinforcing rib 17 can enhance the rigidity of the box body 1. The box body 1 with high rigidity has a high natural frequency, and the high natural frequency can prevent the box body 1 from easily resonating.

[0049] Furthermore, the reinforcing ribs 17 are arranged vertically along the direction from the first end surface 2 to the second end surface 3 to enhance the rigidity of the box body 1 in the up-and-down direction (direction 2 in the figure).

[0050] In one embodiment, reference Figures 2 to 4 , an axle seat 18 is arranged in the cavity of the box body 1, and the output shaft 24 is inserted from the first axle hole 9 into the fifth axle hole 13, and the fifth axle hole 13 is located on the axle seat 18. An oil hole is arranged on the axle seat 18, and the oil holes include a first oil hole 19, a second oil hole 20 and a third oil hole 21, and all of them penetrate the axle seat 18 in the direction from the first axial surface 4 to the second axial surface 5. The first oil hole 19 is in a runway-shaped structure and penetrates the axle seat 18, and the second oil hole 20 and the third oil hole 21 are located on both sides of the first oil hole 19, and the second oil hole 20 and the third oil hole 21 are both arranged close to the inner wall of the cavity.

[0051] A bearing plate 32 is arranged in the box body 1, and the fourth shaft hole 11 and the sixth shaft hole 14 are arranged on the bearing plate 32. The shaft seat 18 is located in the box body 1, and the surface for mounting the shaft seat 18 is parallel to the bearing plate 32, and one side surface of the bearing plate 32 and the surface for mounting the shaft seat 18 are located at the same height in the box body 1, so that the surface for mounting the shaft seat 18 and one side surface of the bearing plate 32 are coplanar, with reference to Figure 2 .

[0052] The existing box body 1 has only one circular oil hole at the oil hole 19 of the shaft seat 18, which makes the oil return speed slow. The present application has three oil holes arranged on the shaft seat 18, making full use of the position space of the shaft seat 18, improving the utilization rate of the shaft seat 18 space and the oil return speed.

[0053] In addition, when the side wall of the fifth shaft hole 13 contacts the bearing of the input shaft 22, the fifth shaft hole 13 provides bearing support for the input shaft 22. Therefore, the side of the fifth shaft hole 13 used to install the bearing cannot be greatly damaged, that is, the circular oil hole can only be located below the surface used to install the bearing, so it is not appropriate to enlarge the circular oil hole by increasing the diameter. Therefore, the utility model sets the existing circular oil hole into a runway-shaped structure (the first oil hole 19). In this way, the first oil hole 19 is only on the left and right sides of the shaft seat 18 (with Figure 4 As a benchmark), the oil hole area is increased to increase the oil return speed.

[0054] The second aspect of the utility model provides a gear box for a processing center, referring to Figure 2 and Figure 3 The gearbox includes: an input shaft 22, a transmission shaft 23, an output shaft 24 and a gearbox body of any of the above items, the input shaft 22 is inserted in the first shaft hole 9 and the fifth shaft hole 13, the transmission shaft 23 is inserted in the third shaft hole 12 and the sixth shaft hole 14, and the output shaft 24 is inserted in the second shaft hole 10 and the fourth shaft hole 11.

[0055] The input shaft 22 is provided with a first gear 27, the transmission shaft 23 is provided with a second gear 28 and a third gear 29 which are distributed up and down, and the output shaft 24 is provided with a fourth gear 30 and a fifth gear 31 which are distributed up and down; wherein, the second gear 28 is a larger gear than the third gear 29, and the fourth gear 30 is a smaller gear than the fifth gear 31, that is, the pitch circle diameter of the second gear 28 is larger than that of the third gear 29, and the pitch circle diameter of the fourth gear 30 is smaller than that of the fifth gear 31. The second gear 28 and the first gear 27 are normally kept in meshing. In the first meshing state, the second gear 28 is meshed with the fourth gear 30, and the third gear 29 is disconnected from the fifth gear 31. In the second meshing state, the second gear 29 is disconnected from the fourth gear 30, and the third gear 29 is meshed with the fifth gear 31. By switching between the first meshing state and the second meshing state, the gearbox realizes speed change. That is, by moving the transmission shaft 23 up and down, the second gear 28 is meshed with the fourth gear 30 , or the third gear 29 is meshed with the fifth gear 31 .

[0056] A third aspect of the utility model provides a machining center, which comprises the gear box of any one of the above-mentioned machining centers.

[0057] The above are only preferred implementations of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A gear housing, characterized in that: include: A box body (1) having a cavity inside, the box body (1) comprising a first end face (2) and a second end face (3) opposite to each other, the first end face (2) comprising a first axial face (4) and a second axial face (5), the second end face (3) comprising a third axial face (6) and a fourth axial face (7), the first axial face (4) being provided with a first axial hole (9) for mounting an input shaft (22), the second axial face (5) being provided with a second axial hole (10) for mounting an output shaft (24), a third axial hole (12) for inserting a transmission shaft (23) being provided between the first axial hole (9) and the second axial hole (10), and the fourth axial face (7) being provided with a first through hole (15) coaxial with the second axial hole (10); The first axial surface (4) and the second axial surface (5) are arranged in steps, and the first axial surface (4) is higher than the second axial surface (5); the third axial surface (6) and the fourth axial surface (7) are arranged in steps, and the third axial surface (6) is higher than the fourth axial surface (7).

2. The gear housing according to claim 1, characterized in that: The first end surface (2) is provided with a fifth axial surface (8) located between the first axial surface (4) and the second axial surface (5); the first axial surface (4), the fifth axial surface (8) and the second axial surface (5) are arranged in a stepped manner from high to low; and the third axial hole (12) is arranged on the fifth axial surface (8).

3. The gear housing according to claim 2, characterized in that: A fourth axial hole (11) coaxial with the second axial hole (10) is provided in the box body (1).

4. The gear housing according to claim 3, characterized in that: The second end surface (3) is provided with a sixth axial surface located between the third axial surface (6) and the fourth axial surface (7), and the third axial surface (6), the sixth axial surface and the fourth axial surface (7) are arranged in steps from high to low; and / or, The straight-line distance from the second axial plane (5) to the fourth axial plane (7) is smaller than the straight-line distance from the first axial plane (4) to the third axial plane (6).

5. The gear housing according to claim 3, characterized in that: The hole wall of the first shaft hole (9) is provided with a first bearing portion (25) for bearing the bearing, and the hole wall of the second shaft hole (10) is provided with a second bearing portion (26) for bearing the bearing.

6. The gear housing according to claim 3, characterized in that: The box body (1) is provided with a fifth axial hole (13) coaxial with the first axial hole (9), and the box body (1) is provided with a sixth axial hole (14) coaxial with the third axial hole (12). The aperture of the first axial hole (9) is not less than the aperture of the fifth axial hole (13), the aperture of the second axial hole (10) is not less than the aperture of the fourth axial hole (11), and the aperture of the third axial hole (12) is not less than the aperture of the sixth axial hole (14).

7. The gear housing according to claim 6, characterized in that: A reinforcing rib (17) is provided on the inner wall of the cavity; and / or, An axle seat (18) is arranged in the cavity of the box body (1), the fifth axle hole (13) is located on the axle seat (18), and an oil hole arranged in a direction from the first axle surface (4) to the second axle surface (5) is arranged at the bottom of the axle seat (18), the oil hole comprising a first oil hole (19), a second oil hole (20) and a third oil hole (21) all penetrating the axle seat (18), wherein the first oil hole (19) is a runway-shaped structure and passes through the fifth axle hole (13), and the second oil hole (20) and the third oil hole (21) are located on both sides of the first oil hole (19); A bearing plate (32) is arranged in the box body (1), and the fourth axial hole (11) and the sixth axial hole (14) are arranged on the bearing plate (32), and the surface for mounting the shaft seat (18) is coplanar with the bearing plate (32).

8. A gearbox for a machining center, characterized in that: It comprises an input shaft (22), a transmission shaft (23), an output shaft (24) connected in sequence by gears, and a gear box body as described in any one of claims 3 to 7, wherein the input shaft (22) is inserted in the first shaft hole (9), the transmission shaft (23) is inserted in the third shaft hole (12), and the output shaft (24) is inserted in the second shaft hole (10) and the fourth shaft hole (11) and passes through the first through hole (15).

9. The gearbox of a machining center according to claim 8, characterized in that: The input shaft (22) is provided with a first gear (27); the transmission shaft (23) is provided with a second gear (28) and a third gear (29) respectively, the pitch circle diameter of the second gear (28) is larger than that of the third gear (29); the output shaft (24) is provided with a fourth gear (30) and a fifth gear (31) respectively, the pitch circle diameter of the fourth gear (30) is smaller than that of the fifth gear (31); The second gear (28) is meshed with the first gear (27). In a first meshing state, the second gear (28) is meshed with the fourth gear (30), and the third gear (29) is disengaged from the fifth gear (31). In a second meshing state, the second gear (28) is disengaged from the fourth gear (30), and the third gear (29) is meshed with the fifth gear (31). By switching between the first meshing state and the second meshing state, the gear box realizes speed change.

10. A machining center, characterized in that: A gear box for a machining center comprising the gear box of claim 9.

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