Transmission unit for a motor vehicle transmission with a spur gear arranged rotatably on an intermediate shaft

Abstract

A transmission unit for a motor vehicle transmission includes a spur gear (6) which is arranged rotatably on an intermediate shaft (5) and which can be fixed to the intermediate shaft (5) for the transmission of drive power via clutch means. On one side flank (9) of the spur gear, a first freewheel gear portion (10) is provided which can be connected to a corresponding shaft-side second freewheel gear portion (11) via an internally toothed sliding sleeve (12). On the opposite side flank (13) of the spur gear, a parking lock gear portion (14) is provided for engaging a pawl (15) to block the transmission unit when the vehicle is at a standstill.

Claims

1. A transmission unit for a motor vehicle transmission, with a spur gear which is arranged rotatably on an intermediate shaft and can be fixed to the intermediate shaft for the transmission of drive power, wherein the spur gear is provided on a first side flank with a first freewheel gear portion which can be connected to a corresponding shaft-side second freewheel gear portion via an internally toothed sliding sleeve, and wherein the spur gear is provided on a second side flank opposite the first side flank with a parking lock gear portion to engage with a pawl to block the transmission unit when the vehicle is at a standstill.

2. The transmission unit according to claim 1, wherein an outside diameter of the parking lock gear portion is smaller than a root diameter of the spur gear.

3. The transmission unit according to claim 1, wherein an outside diameter of the first freewheel gear portion is smaller than a root diameter of the spur gear and smaller than an outside diameter of the parking lock gear portion.

4. The transmission unit according to claim 1, wherein the spur gear is rotatably mounted on the intermediate shaft via an at least single-row needle bearing.

5. The transmission unit according to claim 1, wherein the spur gear is a one-piece component with an integrally formed freewheel portion and an integrally formed parking lock gear portion.

6. The transmission unit according to claim 5, wherein the one-piece component is manufactured from steel by machining a drop-forged semi-finished product.

7. The transmission unit according to claim 1, wherein the sliding sleeve coupling the first freewheel gear portion to the second freewheel gear portion is axially adjustable via a shift fork arrangement engaging in an outer radial circumferential groove of the sliding sleeve.

8. The transmission unit according to claim 4, wherein the second freewheel gear portion of the intermediate shaft has a larger outer diameter than a shaft portion adjacent thereto for receiving the at least single-row needle bearing.

9. The transmission unit according to claim 1, wherein the intermediate shaft is supported via a first roller bearing axially adjacent to the parking lock gear portion and a second roller bearing axially adjacent to the shaft-side second freewheel gear portion.

10. An electric axle drive of a motor vehicle, with a motor vehicle transmission arranged between an electric motor and a differential gear for reducing the engine speed, which includes a function-integrated transmission unit according to claim 1.

11. A transmission comprising: a shaft having a shaft-side freewheel gear portion; a gear rotatably supported about the shaft, the gear having a gear-side freewheel portion, a spur gear portion, and a parking gear portion; and a sleeve configured to move axially between a first position in which it rotationally couples the gear to the shaft and a second position in which the gear and the shaft are free to have different rotational speeds.

12. The transmission of claim 11 wherein, in the second position, the sleeve engages the shaft-side freewheel gear portion but does not engage the gear-side freewheel portion.

13. The transmission of claim 11 further comprising a parking pawl configured to engage the parking gear portion such that a rotational speed of the gear is constrained to be equal to zero.

14. The transmission of claim 11 wherein a root diameter of the spur gear portion exceeds an outer diameter of the parking gear portion.

15. The transmission of claim 14 wherein the outer diameter of the parking gear portion exceeds an outer diameter of the gear-side freewheel portion.

16. The transmission of claim 11 wherein an outer diameter of the parking gear portion exceeds an outer diameter of the gear-side freewheel portion.

17. The transmission of claim 11 wherein a root diameter of the spur gear portion exceeds an outer diameter of the gear-side freewheel portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Further measures are shown in more detail below together with the description of a preferred exemplary embodiment based on the figure. In the figures:

[0015] FIG. 1 shows a schematic block diagram representation of an electric axle drive with a motor vehicle transmission containing the transmission unit,

[0016] FIG. 2 shows a longitudinal section through the transmission unit according to FIG. 1,

[0017] FIG. 3 shows a perspective view of a functionally integrated spur gear of the transmission unit according to FIG. 2, and

[0018] FIGS. 4A to 4C show perspective views of the transmission unit in different functional positions of the parking lock and the freewheel.

DETAILED DESCRIPTION

[0019] According to FIG. 1, an electric axle drive of a motor vehicle not shown here essentially consists of an electric motor 1, the driving force of which is transmitted to a differential gear 2 of a wheel axle 3. The engine speed generated by the electric motor 1 is reduced to a slow speed via a motor vehicle transmission 4—here only indicated schematically to achieve the desired wheel speeds of the wheel axle 3. The motor vehicle transmission 4 comprises a function-integrated transmission unit which is arranged in the region of an intermediate shaft 5 and which, among other things, comprises a spur gear 6 for transmitting the drive power from the electric motor 1 to the differential transmission 2.

[0020] According to FIG. 2, the spur gear 6 is in principle arranged rotatably on the intermediate shaft 5 via two needle bearings 7a and 7b arranged to be axially adjacent to one another. To transmit the drive power, however, the spur gear 6 can be fixed on the intermediate shaft 5 by means of the clutch means described below. The intermediate shaft 5 is rotatably supported by roller bearings 8a and 8b arranged on both sides of the spur gear 6 in a gear housing—not shown here.

[0021] To disconnect the power flow in an emergency, the aforementioned clutch means comprises a first freewheel gear portion 10, which is arranged on a side flank 9 of the spur gear 6 and which represents a straight-toothed sprocket which corresponds to a corresponding shaft-side second freewheel gear portion 11 having the same shape. Both freewheel gear portions 10 and 11 can be connected to an axially movable sliding sleeve 12 as a clutch means. In the connected position of the sliding sleeve 12, the drive power is transmitted from the intermediate shaft 5 to the spur gear 6 or vice versa.

[0022] The spur gear 6 also has on the opposite side flank 13 a parking lock gear portion 14 which cooperates with a pawl 15 in a manner known per se to implement the function of a parking lock. The parking lock is used to block the transmission unit in the vehicle state.

[0023] According to FIG. 3, the spur gear 6 used within the scope of the transmission unit consists of a central helical toothing portion 16, the parking lock gear portion 14 formed on one side thereon with a relatively coarse tooth pitch and on the opposite side a freewheel portion 10 formed thereon with a type of straight spline. The outside diameter of the parking lock gear portion 14 is smaller than the root diameter of the helical toothing portion 16 and the outside diameter of the freewheel gear portion 10 is in turn smaller than the outside diameter of the parking lock gear portion 14.

[0024] According to FIG. 4a, the transmission unit is in a functional position in which the parking lock is deactivated. To this extent, the pawl 15 is out of engagement with respect to the parking lock gear portion 14. The sliding sleeve 12 is at the same time in the position close to the spur gear, so that the spur gear 6 is fixed on the intermediate shaft 5 to transfer the drive power.

[0025] In FIG. 4b, in contrast to the functional position described above, the locking blade 15 is engaged with the parking lock gear portion 14. The parking lock is activated when the vehicle is at a standstill, which prevents unintentional vehicle movement.

[0026] FIG. 4c illustrates the transmission unit in a functional position in which the power flow is separated as a result of an emergency when the parking lock is disengaged, that is, while the vehicle is in motion. As a result, the drive power is withdrawn from the vehicle's wheels. For this purpose, the sliding sleeve 12 is switched to the position remote from the spur gear, so that the spur gear 6 can rotate relative to the intermediate shaft 5 in the sense of a freewheel function.

[0027] The transmission unit is not restricted to the preferred exemplary embodiment described above. For example, it is also possible for the freewheel gear portion and/or the parking lock gear portion to be designed as separate gearwheels that are attached to a central spur gear.

LIST OF REFERENCE SYMBOLS

[0028] 1 Electric motor [0029] 2 Differential gear [0030] 3 Wheel axle [0031] 4 Motor vehicle transmission [0032] 5 Intermediate shaft [0033] 6 Spur gear [0034] 7 Needle bearing [0035] 8 Rolling bearing [0036] 9 Side flank [0037] 10 First freewheel gear portion [0038] 11 Second freewheel gear portion [0039] 12 Sliding sleeve [0040] 13 Side flank [0041] 14 Parking lock gear portion [0042] 15 Pawl [0043] 16 Helical toothing portion