WO2005111467A1

WO2005111467A1 - Harmonic drive transmission, especially for a steering effort aid of a vehicle steering system

Info

Publication number: WO2005111467A1
Application number: PCT/EP2005/004943
Authority: WO
Inventors: Siegmar Gilges; Matthias Mendel; Michael Schaffer
Original assignee: Harmonic Drive Ag
Priority date: 2004-05-10
Filing date: 2005-05-06
Publication date: 2005-11-24

Abstract

The invention relates to a harmonic drive transmission (1), especially for a steering effort aid of a vehicle steering system, said transmission comprising at least two rotatable components (2, 3) which are meshed together and can be respectively coupled to a shaft (4; 5), for example a drive shaft or an output shaft. At least one of the components (2, 3) is embodied in a pot-shaped manner with a bottom surface (7) located at a distance from the region (6) of the meshing. The component (2) can be connected to the shaft (4) in a rotationally fixed manner on the bottom surface by means of at least one connection element (8). According to the invention, the connection element (8) is essentially arranged inside the pot-shaped component (2). The invention also relates to a corresponding shaft (4) and a vehicle steering system, especially comprising a steering effort aid, provided with said harmonic drive transmission (1) and said shaft (4).

Description

Description: Tension shaft gear, especially for eir.e power steering of a vehicle steering system

description

The invention relates to a voltage shaft transmission, in particular for a power steering aid of a vehicle steering system, with at least two rotatable components which are in mesh with one another, each of which can be coupled to a shaft, for example an input shaft or output shaft, at least one of the components being cup-shaped with one in the region of the Tooth engagement of the components at a spaced bottom surface is formed, on which the cup-shaped component can be connected in a rotationally fixed manner to the shaft by means of at least one connecting element.

State of the art

Such a voltage wave gear, which is also referred to as a harmonic drive gear, is already known from the construction manual, Harmonic Drive Antriebstechnik GmbH, Li burg / Lahn, 3rd edition, April 1999. The stress wave gear has a wave generator (wave generator) which drives a movable, elastically deformable gear ring (Flexspline) with external teeth, which meshes with the internal teeth of a cylindrical gear ring (circular spline). The shaft generator, the flexspline and the circular spline are each connected to a shaft, which can act as an input or output shaft. The Flexspline is pot-shaped. To connect the Flexspline to the shaft, the bottom of the pot is designed as a flange, which is screwed to a counter flange of the shaft using screws. Such a flange connection is relatively complex to assemble and builds up space due to the counter flange.

task

Proceeding from this, the invention has for its object to provide a voltage shaft gear of the type mentioned, which is compact in terms of its dimensions, in particular with regard to its axial length. According to a side aspect of the invention, a backlash-free and secure connection between the pot-shaped component of the stress wave transmission and the shaft connected to this component is also to be achieved.

Invention and advantageous effects

To solve the problem, a voltage wave transmission is proposed, which has the features mentioned in claim 1. The voltage wave transmission is characterized, among other things, by the fact that the connecting element lies essentially within the pot-shaped component. By this measure, the stress wave gear can be made particularly compact, since the free volume of the pot-shaped component that is present anyway is used between the area of the tooth engagement and the pot base or the base surface. This makes it a compact Design of the voltage shaft gearbox achieved in both the axial and radial directions.

For example, the Flexspline or the Circular Spline are suitable as rotatable, tooth-meshing components of the stress wave transmission. Such a component can also relate to the dynamic spline, which corresponds to the circular spline and differs from it in that it has the same number of teeth as the flex spline. The Circular Spline, on the other hand, has a larger number of teeth than the Flexspline.

According to a first embodiment of the invention, it is provided that the connecting element is a hub attached to the bottom surface of the pot-shaped component, which is supported on the shaft in the assembled state. As a result, a rotationally fixed connection between the cup-shaped component and the shaft can be achieved in a simple manner by plugging the hub onto the shaft or onto a shaft end without additional components, such as screws or the like.

According to a further embodiment of the invention, it is provided that the connecting element and the cup-shaped component are arranged coaxially to the central axis of the stress wave transmission. As a result, the shaft, which is connected to the connecting element in a rotationally fixed manner, can be held coaxially with the pot-shaped component, thereby creating a structurally simple and compact arrangement of the shaft and the pot-shaped component. According to a further embodiment of the invention, it is provided that the connecting element and the shaft can be positively connected for the transmission of a torque. As a result, a connection between the shaft and the cup-shaped component can be realized, by means of which particularly high torques can also be transmitted without causing the shaft to slip, that is, to slip through the connecting element.

It is advisable that the positive connection is formed by a multi-spline profile on the inner circumference of the connecting element designed as a hub, which engages in a corresponding counter profile on the outer circumference of the shaft in the assembled state of the voltage shaft gear. As a result, a positive connection is realized, which is produced in a simple manner by pushing the hub onto the shaft and can also be released again simply by pulling the hub and shaft apart.

An advantageous embodiment of the invention further provides securing means against axial displacement of the connecting element designed as a hub with respect to the shaft, in order to avoid an unwanted release of the hub from the shaft.

It is advantageous if the hub is braced in the axial direction with the shaft by means of the securing means in the assembled state. This measure creates a frictional connection between the hub and the shaft, which also enables the transmission of high torques between the hub and the shaft. The securing means thus has a dual function, namely in addition to the axial function Locking of the connecting element against the shaft also the function of torque transmission. If the bracing is provided in addition to a positive connection between the hub and the shaft, the design-related play in the transmission of the torque between the shaft and the hub can be compensated in this way. As a result, a backlash-free torque transmission between the shaft and the cup-shaped component can be achieved at least for the load cases that usually occur during operation of the stress wave gear.

This double function can be implemented in a simple and effective manner by the securing means having a screw element, such as a nut, which can be screwed onto the shaft and presses the hub against a shoulder of the shaft in the assembled state. As a result, a particularly durable and high-tension connection is produced.

According to an advantageous embodiment of the invention, it is provided that at least one with the corresponding end face of the parts causing the axial bracing (shaft, hub, shoulder) is at least partially provided with a friction-increasing coating. This measure increases the frictional connection between the shaft and the connecting element, so that a backlash-free torque transmission is achieved by this frictional connection alone even at higher torques.

It is advantageous to have a disk coated on both sides to increase the friction value between the corresponding end faces of the axial bracing parts are provided. As a result, the contact area between the end faces can be enlarged and thus the torque that can be transmitted by the force-locking connection can be increased.

As an alternative to the axial bracing of the shaft and hub, provision can also be made for the securing means to be formed by at least one securing element which can be latched into at least one circumferential groove on the shaft and by means of which, in the assembled state, the hub is held axially against a shoulder of the shaft is. In this way too, a simple and inexpensive securing against axial displacement of the hub relative to the shaft is realized. Because only one securing element is pulled open, the axial securing of the position can also be produced with little effort.

In the same direction, the measure aims that the securing means are formed by two securing elements which can be snapped into circumferential grooves in the shaft, between which the hub is held axially on the shaft in the assembled state.

It is advisable for the hub to have a recess on the side, in which the securing means is received in the assembled state. This measure also aims in the direction of providing a tension shaft gear with a particularly compact design in the axial direction.

According to an embodiment of the invention, it is further provided that the hub and the cup-shaped component are separate Are parts which are preferably connected to one another by welding, in particular laser welding or electron beam welding. As a result, the cup-shaped component with the hub can be produced in a simple and inexpensive manner, since the cup-shaped component, which is usually of relatively complex design, can be produced separately from the hub. In addition, existing pot-shaped components without a hub can be used.

The cup-shaped component of the flexspline of the tension shaft transmission is preferably. In principle, this has a relatively large internal volume in order to have sufficient elastic deformability in the region of its toothing in spite of the shape of the pot for proper gear function.

The tension shaft gear is preferably designed as a superposition gear and has an input shaft, which is designed as a hollow shaft and drives the shaft generator of the tension shaft gear, in which the shaft for the flexspline runs.

To achieve the object, a shaft, in particular an output or drive shaft, is also provided for the rotationally fixed connection to the voltage shaft gear.

The tension shaft transmission and the shaft are preferably used in a vehicle steering system, in particular in a vehicle steering system with a steering aid. embodiments

Further objectives, advantages, features and possible uses of the present invention result from the following description of two exemplary embodiments with reference to the drawing. All of the described and / or illustrated features, alone or in any meaningful combination, form the subject matter of the present invention, regardless of how they are summarized in the claims or their relationship.

Show it:

Figure 1 shows a possible embodiment of the tension shaft transmission according to the invention in a power steering system as a sectional view and

Figure 2 shows another embodiment of the voltage shaft transmission in a power steering system as a sectional view.

In Figure 1, a voltage wave transmission 1 is shown, which is part of a power steering system of a vehicle steering system. The stress wave gear 1 serves there as a superposition gear for superimposing steering movements. It is connected on the one hand to a shaft or steering input shaft 4 which executes a main steering movement and is connected to the steering wheel of the vehicle via the steering spindle, and to a steering output shaft 5 in a rotationally fixed manner. Beyond that it is Tension shaft gear 1 is connected in a rotationally fixed manner to a further input shaft 20, which forms the output shaft of an electric motor 19 and generates an auxiliary steering movement. The tension shaft transmission 1 enables the main steering movement and the auxiliary steering movement to be superimposed and generates a resulting steering movement via the steering output shaft 5 onto the wheels.

In this steering aid, the steering input shaft 4 with the elastically deformable gear ring (Flexspline) and the steering output shaft 5 with the circular spline 3 of the tension shaft gear 1 are each rotatably connected. In addition, the further input shaft 20 is connected to the shaft generator 21 of the voltage shaft transmission 1 in a rotationally fixed manner. The known principle of operation of the tension shaft transmission 1 as well as the mode of operation of the steering assistance shown in FIG. 1 will not be explained in more detail here. In this regard, reference is made to the applicant's parallel international patent application entitled "Device for superimposing steering movements for a power steering aid and method for operating the device" with the same seniority.

The Flexspline 2 is cup-shaped and has an external toothing which meshes with the internal toothing of the circular spline 3. In order to ensure sufficient elastic deformability of the flexspline 2, which is necessary for the tension shaft transmission 1 to function properly, the flexspline 2 inherently has a certain minimum distance between the area 6 of the external toothing or the tooth engagement with the Circular spline 3 and the bottom surface 7 provided by the pot shape. This freely available volume, which is inherent to the principle, is used to produce a connecting element 8 for the rotationally fixed connection of the steering input shaft 4 to the Flexspline 2.

In the exemplary embodiment, the connecting element 8 is a hub fastened to the bottom surface 7 of the Flexsplines 2, which is supported on the steering input shaft 4 in the assembled state. The hub 8 and the Flexspline 2 are arranged coaxially to the central axis 9 of the stress wave transmission.

The hub 8 and the steering input shaft 4 are positively connected to one another for the transmission of a torque. This ensures in particular the transmission of torque peaks. Torque peaks of this type can occur, for example, in the event of misuse when blocking or when the steering output shaft 5 is stiff

The positive connection is formed by a splined profile 10 on the inner circumference of the hub 8, which engages in a corresponding counter profile 11 on the outer circumference of the steering input shaft 4.

In addition, securing means 12 against axial displacement of the hub 8 with respect to the steering input shaft 4 are provided. The securing means 12 are formed by a securing element 16, such as, for example, a locking washer, circlip, snap ring, which is engaged in a circumferential groove 17 of the steering input shaft 4 and by means of which the hub 8 against one Paragraph 14 of the steering input shaft 4 is held axially. The securing element 16 is underlaid in relation to the hub 8 with a disk element 22 pushed over the shaft 4.

The hub 8 has a recess 18 on the side, in which the securing element 16 and the disk element are received. This enables a particularly compact design of the voltage shaft transmission 1 in the axial direction. The flexspline 2 and the hub 8 are made in one piece in the present exemplary embodiment.

FIG. 2 shows a further exemplary embodiment of the tension shaft transmission 1, which is also used in a power steering system of a vehicle steering system according to FIG. 1. Components in FIG. 2 which are identical to those in FIG. 1 are provided with the same reference symbols; in this respect reference is made to the description of FIG. 1.

The exemplary embodiment of the voltage wave transmission 1 according to FIG. 2 differs from the exemplary embodiment in FIG. 1, inter alia, in that the connecting element 8 and the flexspline 2 are separate components which are connected to one another by means of welding, preferably laser welding or electron welding.

In addition, in the exemplary embodiment according to FIG. 2, instead of a locking ring, a shaft nut 13 is provided as securing means 12, which is screwed onto the steering input shaft 4 and presses the hub 8 against the shoulder 14 of the steering input shaft 4. It is because of it by means of the shaft nut 13, both securing against axial displacement of the hub 8 with respect to the steering input shaft 4 and, at the same time, a frictional connection for transmitting a torque between the steering input shaft 4 and the hub 8 are realized. This frictional connection enables in particular a torque transmission between the steering input shaft 4 and the hub 8 without play. If such a connection were not provided, the connecting element 8 would be rotated relative to the steering input shaft 4 by the multi-spline connection between the hub 8 and the steering input shaft 4 Game come.

In addition, the corresponding end faces 15 of the shoulder 14 of the steering input shaft 4 and the hub 8 each have a friction-increasing coating, by means of which even higher torques can be transmitted.

LIST OF REFERENCE NUMBERS

1 tension shaft transmission 2 component, flexspline 3 component, circular spline 4 shaft, steering input shaft 5 shaft, steering output shaft 6 area 7 floor surface 8 connecting element, hub 9 central axis 10 multi-spline profile 11 counter profile 12 securing means 13 nut, shaft nut 14 heel, shaft shoulder 15 end faces 16 securing element 17 groove 18 Recess 19 motor 20 further input shaft 21 shaft generator 22 disk element

Claims

claims

1. Tension shaft transmission (1), in particular for a power steering aid of a vehicle steering system, with at least two rotatable components (2, 3) which mesh with one another and which can each be coupled to a shaft (4; 5), for example a drive shaft or output shaft, wherein at least one of the components (2, 3) is pot-shaped with a bottom surface (7) spaced from the area (6) of the tooth engagement, on which the pot-shaped component (2) is rotatably fixed to the shaft (4) by means of at least one connecting element (8) is connectable, characterized in that the connecting element (8) lies essentially within the pot-shaped component (2).

2. Voltage shaft transmission according to claim 1, characterized in that the connecting element (8) is a on the bottom surface (7) of the pot-shaped component (2) attached hub, which is supported in the assembled state on the shaft (4).

3. Voltage wave transmission according to claim 1 or 2, characterized in that the connecting element (8) and the cup-shaped component (2) are arranged coaxially to the central axis (9) of the voltage wave transmission (1).

4. Voltage shaft transmission according to one of the preceding claims, characterized in that the connecting element (8) and the shaft (4) for the transmission of a torque can be positively connected.

5. Tension shaft transmission according to claim 4, characterized in that the positive connection is formed by a multi-spline profile (10) on the inner circumference of the hub (8), which in the assembled state of the tension shaft transmission (1) in a corresponding counter profile (11) on the outer circumference of the shaft ( 4) intervenes.

6. Voltage shaft transmission according to one of the preceding claims 2 to 5, characterized by securing means (12) against axial displacement of the connecting element designed as a hub (8) relative to the shaft (4).

7. voltage shaft transmission according to claim 6, characterized in that in the assembled state by means of the securing means (12) the hub (8) with the shaft (4) is braced in the axial direction.

8. Voltage shaft transmission according to claim 6 or 7, characterized in that the hub (8) has a screw element, such as a nut (13), which can be screwed onto the shaft (4) and in the assembled state, the hub (8) against presses a shoulder (14) of the shaft (4).

9. voltage wave transmission according to claim 7 or 8, that at least one of the corresponding end faces (15) of the parts causing the axial bracing (shaft (4), hub (8), paragraph 14)) is at least partially provided with a friction-increasing coating and / or a disk coated on both sides to increase friction the corresponding end faces (15) is arranged.

10. Tension shaft transmission according to claim 6, characterized in that the securing means (12) is formed by at least one securing element 16, such as, for example, a locking washer, locking ring, snap ring, which can be latched into at least one circumferential groove (17) of the shaft (4) , and mitteis which in the assembled state the hub (8) is held axially against a shoulder (14) of the shaft (4).

11. Voltage shaft transmission according to claim 10, characterized in that the securing means (12) are formed by two securing elements which can be snapped into circumferential grooves in the shaft (4), between which in the assembled state the hub (8) axially on the shaft ( 4) is held.

12. Voltage shaft transmission according to one of claims 6 to 11, characterized in that the hub (8) laterally has a recess (18) in which the securing means (12) is received in the assembled state.

13. Voltage wave transmission according to one of the preceding claims, characterized in that the hub (8) and the cup-shaped component (2) are separate parts which are preferably connected to one another by means of welding, in particular laser welding or electron beam welding.

14. Voltage wave transmission according to one of the preceding claims, characterized in that the cup-shaped component (2) of the flexspline of the voltage wave transmission (1).

15. Voltage wave transmission according to claim 14, characterized in that it is designed as a superposition gear and has a hollow shaft, the shaft generator (21) of the voltage wave transmission (1) driving input shaft (20), in which the shaft (4) for the Flexspline ( 2) runs.

16. shaft, in particular output or drive shaft, for a voltage shaft transmission according to one of the preceding claims.

17. Vehicle steering system, in particular with a steering aid, comprising at least one transmission according to one of the preceding claims 1 to 15 and / or at least one shaft according to claim 16.