WO2013152955A1

WO2013152955A1 - Helical-toothed gear unit, electrical machine

Info

Publication number: WO2013152955A1
Application number: PCT/EP2013/056575
Authority: WO
Inventors: Martin-Peter Bolz; Lucas Durix
Original assignee: Robert Bosch Gmbh
Priority date: 2012-04-12
Filing date: 2013-03-27
Publication date: 2013-10-17
Also published as: CN104203626A; DE102012205995A1; CN104203626B; EP2836385A1

Abstract

The invention relates to a helical-toothed gear unit (9), particularly for an electrical machine (1), comprising a drive shaft (12) on which a helical-toothed drive pinion (5), particularly a worm (11), is non-rotatably mounted, and comprising an output pinion (15), particularly a worm wheel (13), that is arranged on an output shaft (14) and is engaged with the drive pinion (5). According to the invention, the output pinion (5) is connected by means of a freewheel device (17) to the output shaft (14), the freewheel device (17) being designed to be at least substantially controlled by a rotational direction. The invention further relates to an electrical machine.

Description

description

Helical gear, electric machine

The invention relates to a helical gear, in particular for an electric machine, with a drive shaft on which a helical gear

Drive pinion, in particular a worm, is rotatably disposed, and with an output pinion, in particular worm wheel, which is arranged on an output shaft and is in engagement with the drive pinion. Furthermore, the invention relates to an electrical machine, in particular

Electric motor for motor vehicles, which is a helical gear with a drive shaft on which a helical drive pinion, in particular a worm, is arranged rotationally fixed, and with an output pinion, in particular worm gear, which is arranged on an output shaft and is in engagement with the drive pinion , wherein the drive shaft is formed by a rotor shaft of the electric machine.

State of the art gearboxes and electrical machines of the type mentioned are from the

Known in the art. The construction of electrical machines, and in particular the mounting of a rotor shaft, is a well-established technique today. Usually, the rotor shaft is provided on both sides of a rotor core forming a laminated core with bearings, in particular rolling element bearings, which are fixed in the housing of the electric machine. A free one

The end of the rotor shaft is provided with the drive pinion, via which the torque provided by the electric machine is forwarded. Frequently, a transmission is provided for forwarding the torque, the speed and torque influenced in an advantageous manner. In order to provide particularly high torques on the output shaft, the transmission is often called

Worm gear formed. Due to the helical toothing of the Drive pinion and possibly also of the output pinion or of the worm and worm wheel and axial forces are generated which act, inter alia, on the rotor shaft. To absorb these axial forces in the housing usually the drive pinion associated rolling bearing is pressed onto the rotor shaft and the outer ring beschiled in the housing and axially secured or pressed the outer ring of Wälzkörperlagers in the housing and the inner ring on the rotor shaft beschuppeert and axially secured. In some applications, in normal operation, the axial force on the rotor shaft always or mostly in the same direction affects, so that the

Storage of the rotor shaft is designed essentially for receiving an axial force (in one direction). When reversing the direction of rotation or in the event of a fault, however, the generated axial force can turn around and act in the opposite direction. In this case, the storage is charged unfavorably. An embodiment of the storage such that it can absorb axial forces equally in both directions, is possible only with great design effort.

Disclosure of the invention

The transmission according to the invention with the features of claim 1 has the advantage over the prior art that it is prevented in the event of a fault that an axial force acting in the wrong direction has an effect on the rotor shaft and in particular on its bearing. According to the invention it is provided that the output pinion is connected by means of a freewheel device with the output shaft, wherein the freewheel device is formed at least substantially rotationally controlled. The output pinion is thus not directly rotatably connected to the output shaft. Instead, a freewheel device is provided between the output shaft and the output pinion, which enables or prevents a transmission of power from the output pinion to the output shaft depending on the direction of rotation or the driving direction and optionally on the transmitted and / or counteracting torque. Since the output pinion can continue to be driven due to the freewheel and so far continues to rotate without transmitting forces to the output shaft, there are no axial forces acting on the rotor shaft due to the helical toothing of the drive pinion. Preferably, the freewheel device is designed as a dog clutch.

In this respect, the freewheel device provides a positive transmission of the driving force in a rotational direction, while repealed in a different direction of rotation of the positive connection and thus a power transmission is prevented. The dog clutch requires only a small space and can therefore be well integrated into the transmission.

Preferably, the dog clutch has a first output pinion associated with the clutch element and a second of the output shaft

associated coupling element, wherein the coupling elements each end face a complementary helical toothing and wherein at least one of the coupling elements is arranged axially displaceable. The complementary helical toothing leads to that described above

Mode of operation, in which in one drive direction of rotation is a positive connection, while in the opposite direction of rotation of this positive connection is canceled. This is achieved in that, when driven in the opposite direction, the helical gearing forces apart the coupling elements when a limit torque is exceeded. Since at least one of the coupling elements is arranged axially displaceable, this axial displacement is allowed, so when exceeding the

Limit torque the helical gears is disengaged and inasmuch as no power transmission is possible.

According to an advantageous embodiment of the invention it is provided that the first coupling element is formed by the output pinion or by the worm wheel. The first coupling element is insofar formed integrally with the output pinion or with the worm wheel. This integration of the coupling element in the output pinion a particularly compact design of the transmission is offered. Alternatively, it would of course also conceivable, the first coupling element separately from the

Form output pinion and during assembly output pinion and first

Coupling element at least rotatably connected to each other.

Preferably, the second coupling element is designed as a coupling ring. The annular design of the second coupling element can be pushed onto the output shaft in a simple manner. Preferably, the coupling ring is non-rotatably connected to the output shaft. It is provided in particular that the coupling ring has a radially inwardly projecting driving projection, which with a corresponding

Mitnahmeausnehmung the output shaft cooperates. Of course, several driving projections and driving recesses on the

Coupling ring and the output shaft may be provided. In any case, a positive power transmission is ensured by the coupling ring on the output shaft.

According to a preferred embodiment of the invention it is provided that on the output shaft of the coupling ring axially displaceable and the output pinion or worm wheel is arranged axially fixed and rotatable.

According to this embodiment, it is therefore provided that the coupling ring is axially displaceable, in particular the disengagement of the

To allow helical teeth of the dog clutch. The output pinion is arranged axially fixed on the output shaft, but has a

Degree of freedom in the direction of rotation, so that it is rotatable on the output shaft. In normal operation, the driving force is thus on the

Drive pinion transmitted to the output pinion, which transmits the driving force further on the helical teeth of the dog clutch to the output shaft. If the driving direction of rotation is reversed, the coupling ring becomes at

Exceeding a corresponding torque through the

Helical teeth of the dog clutch axially displaced so that the

Helical teeth of the dog clutch disengaged and thus no force is transmitted to the output shaft. Accordingly, by the

Helical toothing of the input pinion and the output pinion does not exert any axial force on the drive shaft, which could have a negative effect on the bearing of the drive shaft. According to an alternative embodiment of the invention, it is preferably provided that on the output shaft, the worm wheel axially displaceable and rotatable and the coupling ring is axially fixed. In contrast to the embodiment described above, it is therefore alternatively provided that not the coupling ring but the worm wheel itself is arranged so as to be axially displaceable in order to change over when the driving direction of rotation changes Disengage the helical gearing of the dog clutch. Otherwise, the functionality of the above described.

Preferably, the coupling ring and the output pinion or worm wheel are spring-loaded with their helical teeth braced against each other. The spring-loaded bracing is used to hold the dog clutch or the freewheel device in positive engagement during normal operation or after a successful change of direction in which the coupling elements were disengaged to ensure that the coupling elements are brought back into engagement with each other. For spring loading is preferably at least one spring element, in particular a spring washer, more preferably at least one disc spring or coil spring, is provided, which is preferably held biased between an axial stop on the output shaft and the output pinion or the coupling ring. Of the

Axial stop the output shaft is formed in particular by a shoulder, by an increase in diameter of the output shaft

provided. To maintain the bias, a further axial stop is preferably provided, against which the output pinion or the coupling ring is urged by means of the at least one spring element. The second axial stop can be formed for example by a arranged on the output shaft retaining ring, which rests in a circumferential groove of the output shaft.

The electric machine according to the invention with the features of claim 10 has the advantage that the bearing of the rotor shaft can be designed to optimize the direction of rotation, since the formation of unfavorable acting axial forces, against the normal direction of action, is reliably prevented. For this purpose, the electric machine to a transmission, as described above. Further embodiments and advantages therefore also result from the previously described.

In the following, the invention will be explained in more detail with reference to the drawings. Show this Figure 1 is an electrical machine in a simplified

Longitudinal view,

2 shows an advantageous embodiment of a worm gear,

Figure 3 is an exploded view of a freewheel device of

worm gear,

Figure 4 shows another embodiment of the advantageous

Worm gear and

Figure 5 is an exploded view of the second embodiment.

1 shows in a simplified longitudinal sectional view of an electric machine 1, which has a rotatably mounted on a rotor shaft 2 rotor 3, wherein the rotor shaft 2 is rotatably mounted in a housing 4. On the rotor shaft 2, a drive pinion 5 of a not shown in Figure 1 transmission 9 is also provided at its free end, the one

Helical toothing 6 has.

For storage of the rotor shaft 2, two rolling element bearings 7 and 8 are provided. The roller bearing 7 is arranged between the rotor 3 and the drive pinion 6 on the rotor shaft 2, while the roller bearing 8 is provided on the opposite side of the rotor 3. The helical teeth 6 of the drive pinion 5 produced during operation axial forces acting on the rotor shaft 2 and are usually taken up and supported with the rolling element bearing 7. For this purpose, the inner ring of the roller bearing 7 is pressed onto the rotor shaft 2 and the outer ring in the housing 4 shoulders and axially secured, or the outer ring of Wälzkörperlagers 7 is pressed in the housing 4 and the inner ring on the rotor shaft 2 beschbeschert and secured axially.

However, for the present invention, the type of storage is not of further importance. Of importance is only that the type of storage can usually absorb high axial forces in one direction only. Such bearings are particularly suitable for applications in which the electric machine 1 is always operated in the same direction as it

For example, for engines that have a hydraulic plunger over the Power transmission 9, which is the case. However, if the direction of rotation of the drive shaft 2 changes, this ensures that due to the helical gearing, axial forces act on the rotor shaft 2 in the opposite direction. If the bearing is designed to accommodate axial forces substantially in only one direction, this can damage the electrical

Machine lead. A storage, which is acted upon in both directions equally with axial forces, would a high constructive and

mean production engineering effort. Figure 2 shows an embodiment of the advantageously designed transmission 9, which prevents that axial forces on the storage of

Rotor shaft 2 in an unfavorable direction. According to the present embodiment, the gear 9 is formed as a worm gear 10, wherein the drive pinion 5 of a worm 11 which is non-rotatably mounted on the rotor shaft 2, which acts insofar as the drive shaft 12 is arranged. The worm 11 is in engagement with a worm wheel 13 which is arranged on an output shaft 14. The worm wheel 13 is thus a cooperating with the drive pinion 5 output gear 15. The worm wheel 13 may have on its outer shell side a helical toothing or a straight toothing, which cooperates with the worm 11. The worm wheel is rotatable on the output shaft 14 and axially displaceable, as by a

Double arrow 16 indicated, arranged. The on the worm wheel 13th

applied driving force is transmitted by means of a freewheel device 17 to the output shaft 14 substantially rotational direction dependent.

The freewheel device 17 has a dog clutch 18, which is formed by two coupling elements 19 and 20. The first coupling element 19 is formed integrally with the worm wheel 13 and the second coupling element 20 is formed by a separate coupling ring 21 which is rotatably connected to the output shaft 14 and fixed axially thereon.

For this purpose, the coupling ring 21 is on one side on a contact shoulder of the

Output shaft 14 and on the other side of a locking ring 22 which rests in a circumferential groove 23 of the output shaft 14, fixed.

FIG. 3 shows the output-side part of the worm gear 10 for a better understanding in a perspective exploded view. to rotatably connected to the output shaft 14, the coupling ring 21 on its inside a radially inwardly projecting driving projection 24 which rests in the mounted state in a Mitnahmeausnehmung 25 of the output shaft 14, wherein seen in the circumferential direction formed a positive connection between driving projection 24 and Mitnahmeausnehmung 25 for power transmission becomes.

The coupling ring 21 has on its side facing the worm wheel, a helical toothing 26, which is characterized in that the teeth seen in a rotational direction have oblique flanks 27 and in the

opposite direction of rotation seen vertical flanks 28. The

Helical teeth 26 thus results from the oblique flanks 27 of the teeth. Basically, the helical gearing 26 is similar to a Hirth gearing, with the teeth having an oblique flank on one side and a vertical or steep flank on the other side.

The worm wheel 13 has on the side facing the coupling ring 21 a recess 29 whose outer diameter exceeds the outer diameter of the coupling ring 21, so that the coupling ring 21 can be completely accommodated in the recess 29. The bottom of the recess 29 is provided with a complementary to the helical teeth 26 helical teeth 30, which is also characterized by teeth with one-sided oblique edges and other side vertical flanks. With the helical gearing 30, the worm wheel 13 itself forms the first coupling element 19, which cooperates with the coupling ring 21.

Due to the complementary design of the helical gears 26 and 30 are in the initial state, the teeth of the coupling ring 21 between the teeth of the coupling element 19. This is supported by that of

Clutch ring 21 is fixed axially on the output shaft 14 and the

Worm wheel 13 by a plurality of disc springs 31, which are supported on a shoulder 32 of the output shaft 14, is urged against the coupling ring 21, as shown in Figure 2. In normal operation, the worm wheel 13 is driven by the worm such that the vertical flanks of the helical gear 30 are urged against the vertical flanks 28 of the helical gear 26. As a result, the coupling ring 21 is positively entrained, and by lying in the Mitnahmeausnehmung 25 driving projection 24, the force is transmitted to the output shaft 14 so that it is set in rotation. If the direction of rotation of the electric machine 1 is changed, this means that now the oblique flanks of the helical gearing 30 are forced against the oblique flanks 27 of the helical gearing 26. As a result, axial forces are generated, which act between the coupling ring 21 and the worm wheel 13 in such a way that they exceed a still transferable

Limit torque are forced apart. Since the coupling ring 21 is fixed axially on the output shaft 14, in this case the worm wheel 13 is displaced away from the coupling ring 21 against the force of the disc springs 31 on the output shaft 14 in the direction of the abutment shoulder 32. As a result, the helical gears 26 and 30 are disengaged and there is no

Driving force transmitted to the output shaft 14 more. Accordingly, the drive shaft is not affected by the helical teeth of worm and

Worm wheel loaded axially in an unfavorable direction. As a result, an overload of the bearing of the rotor shaft or drive shaft 12 is prevented.

Figures 4 and 5 show another embodiment of the electric machine 1 with the worm gear 10, wherein already known elements are provided with the same reference numerals, so that reference is made to the above description. In the following, essentially only the differences will be discussed.

Figure 4 shows the worm gear 10 in a perspective

Sectional view. In contrast to the previous embodiment, it is now provided that the worm wheel 13 is fixed axially on the output shaft 14, while the coupling ring 21 is arranged axially displaceably on the output shaft 14. In addition, the arrangement is changed such that now the coupling ring 21 is held clamped between the axially fixed worm wheel and the plate springs 31. Wrd the electric machine 1 driven in the normal operating direction, so grab the Helical gears 26 and 30 with the vertical and vertical edges into each other and the driving force is positively transmitted to the output shaft 14. If the direction of rotation of the electric machine 1 is changed, the oblique flanks of the helical gears 26 and 30 urge the coupling ring 21 from the worm wheel 13 against the spring force of the

Disc springs 31 away, so that the helical gears 26 and 30 are disengaged and a power transmission to the output shaft is interrupted. Thus, according to this embodiment, in a simple manner by means of the freewheel device 17, loading of the rotor shaft 2 in an unfavorable direction in the case of an error or an intentional change in direction of rotation is prevented.

The Mitnahmeausnehmung 25 is aligned in this case preferably längsnutartig parallel to the axis of rotation of the output shaft 14, so that the coupling ring 21 can be moved with the driving projection 24 on the output shaft 14 without entrainment projection 24 and

Mitnahmeausnehmung 25 disengaged.

Theoretically, it would also be conceivable to provide the freewheel device 17 on the drive side, that is to say on the drive shaft 12 of the electric machine 1.

The electric machine 1 described above is particularly suitable to be used as a drive device in brake booster, which usually require a normal drive direction of rotation and not or rarely a drive in the opposite direction with little

Torque occurs. By the freewheel device 17, a complex and costly storage of the rotor shaft 2 in the housing 4 can be avoided. Since the freewheel device 17 is almost completely integrated in the worm wheel 13, this can be provided without much additional space requirement.

The output shaft 14 is connected for example via a connecting rod with a hydraulic piston to be driven, wherein the connecting rod linkage converts the rotational movement of the output shaft 14 in a translational movement of the piston. Of course, more or less of the described

Disc springs 31 are provided for clamping the jaw clutch 18. Alternatively, it is also conceivable to replace the disc springs 31 by a coil spring. In principle, the number of springs or the adjustable spring force is freely selectable, however, is by the selected spring force the approved

Torque of the freewheel device 17, which can still be transmitted in the opposite direction of rotation before the helical gears 26 and disengaged determined. The higher the spring force, the later the helical gears 26, 30 are disengaged. Depending on the application, the effect of the freewheel device 17 can thus be adapted in a simple manner.

Claims

Helical gear (9), in particular for an electric machine (1), with a drive shaft (12) on which a helical gear

Drive pinion (5), in particular a worm (11), is arranged in a rotationally fixed manner, and with an output pinion (15), in particular worm wheel (13), which is arranged on an output shaft (14) and is in engagement with the

Drive pinion (5) is located, characterized in that the output pinion

(5) is connected to the output shaft (14) by means of a freewheel device (17), the freewheel device (17) being at least substantially

is designed to be controlled in the direction of rotation.

Transmission according to claim 1, characterized in that the

Freewheel device (17) is designed as a claw clutch (18).

Transmission according to one of the preceding claims, characterized

characterized in that the claw clutch (18) has a first

Coupling element (19) assigned to the output pinion (15) and a second coupling element (20) assigned to the output shaft (14), the coupling elements (19, 20) each having a complementary one on the end face

Have helical gearing (26,30) and at least one of the coupling elements (19,20) is arranged to be axially displaceable.

Transmission according to one of the preceding claims, characterized

characterized in that the first coupling element (19) from the

Worm wheel (13) is formed.

Transmission according to one of the preceding claims, characterized

characterized in that the second coupling element (20) is designed as a coupling ring (21).

6. Transmission according to one of the preceding claims, characterized

characterized in that the coupling ring (21) is connected to the output shaft (14) in a rotationally fixed manner.

Transmission according to one of the preceding claims, characterized

characterized in that the coupling ring (21) is axially displaceable and the worm wheel (13) is arranged axially fixed and rotatable on the output shaft (14).

Transmission according to one of the preceding claims, characterized

characterized in that the worm wheel (13) is axially displaceable and rotatable on the output shaft (14) and the coupling ring (21) is axially fixed.

Transmission according to one of the preceding claims, characterized

characterized in that the coupling ring (21) and the worm wheel (13) are spring-loaded with their helical teeth (26,30) braced against each other. 10. Electric machine, in particular electric motor for motor vehicles, with a rotor shaft (2) rotatably mounted in a housing, and with a gear (9) which has a drive shaft (12) on which a helical drive pinion (5), in particular a worm (11), is arranged in a rotationally fixed manner, and an output pinion (15), in particular a worm wheel (13), which is arranged on an output shaft (14) and engages with the drive pinion

(5), wherein the rotor shaft (2) forms the drive shaft (12) of the transmission (9), characterized by the design of the transmission (9) according to one or more of the preceding claims.