FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
DIVIDED STABILIZER FEATURING AN OPTIMIZED SPRING CONSTANT
2. APPLICANT(S)
a) Name : ZF FRIEDRICHSHAFEN AG
b) Nationality : GERMAN Company
c) Address : 88038 FRIEDRICHSHAFEN
GERMANY
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

The invention relates to a divided stabilizer according to the features of the preamble of claim 1. Such stabilizers are used in particular in the field of automotive engineering.
Basically, with each axle of a motor vehicle a stabilizer is associated, which operates on the torsion bar principle and is disposed parallel to the vehicle axle and fastened at both ends to a wheel suspension. This stabilizer substantially prevents and/or reduces the transmission of the rolling motions, which are caused by the road conditions and emanate from the wheels, to the vehicle. Such rolling motions occur in particular during cornering or under uneven road conditions.
One-piece stabilizers are designed, in terms of their dimensions and material properties, for a predetermined spring rate so that they are able to take up torsional forces only in a specific order of magnitude and apply corresponding counter forces. One-piece stabilizers therefore react to different loads either too gently or too harshly, this having an adverse effect on driving comfort. For this reason, one-piece stabilizers are basically suitable only to a limited extent for motor vehicles intended for both on- and off-road use. For such applications, therefore, a divided stabilizer is used, which comprises two stabilizer parts that are both connected to one another by an actuator that enlarges the angle of rotation. Such an actuator may be for example a hydraulic swivel motor, a flexible rotary coupling or an engageable clutch.
Each of these actuators basically comprises an outer rotary part, which is connected by a cover and a flange to one of the two stabilizer parts, and an inner rotary part,
which is connected by a shaft to the other stabilizer part. Both rotary parts of the actuator are designed to be rotatable by a limited angle relative to one another. Generally, as connection parts between the flange and the one stabilizer part as well as between the shaft and the other stabilizer part, conventional clamping- or screw bushes are used.
2

Such divided stabilizers meet a wide variety of requirements. They do however have a substantial drawback. Each actuator is namely a compact unit of a considerable linear extension, which to a corresponding extent is detrimental to the effective spring lengths of the two stabilizer parts.
For improving the spring rate, from DE 100 12 915 Al a divided stabilizer with an optimized spring rate is known, in which the outer rotary part of the actuator is constructed integrally with the one stabilizer part and the inner rotary part of the actuator is constructed integrally with the other stabilizer part. Consequently, the one stabilizer part is extended right into the radial plane of the force-generating rotary parts of the actuator, so that the two stabilizer parts are effectively interrupted only by a slight axial clearance relative to one another. This has functional advantages but manufacture is possible only with an increased outlay owing to the length and multi-curved shape of the stabilizer part and owing to the necessary high accuracy of fit of the inner rotary part of the actuator.
From US 5,700,027 a corresponding swivel motor is therefore known, the inner rotary part of which has two axial and opposite blind bores. Both blind bores are designed to differ in depth, wherein the deeper blind bore is equipped with an internal profile for connection to a correspondingly configured first stabilizer part and the shorter blind bore is designed to receive a profile-free end of the second
stabilizer part. The different lengths of the blind bores and their different configuration are intended to prevent a mix-up of the two stabilizer parts during
assembly. In addition, the bases of the two blind bores are designed as stops for the two stabilizer parts. Both blind bores are spaced axially so far apart from one another that there is sufficient installation space left to lead through connection channels for the pressure- and suction chambers of the swivel motor.
Although the two-piece construction and the profile connection of the inner rotary part to the one stabilizer part do eliminate the manufacture-related drawbacks
compared to the one-piece variant, at the same time the need for the second blind
3

bore in the inner rotary part again entails an increase of the manufacturing outlay for the connection of the outer rotary part to the second stabilizer part. An additional factor increasing costs is that the shaping of the force-transmitting profile in the blind bore is inevitably a laborious process. A further drawback is that the profile connection between the inner rotary part and the corresponding stabilizer part is designed purely as a positive engagement connection. Such positive engagement however in principle entails a play between the two components that leads to functional drawbacks and may be minimized only with an unacceptably high manufacturing outlay.
A substantial drawback however arises from the fact that the profile connection of the inner rotary part to the first stabilizer part is disposed outside of the axial centre of the axial length - crucial for the force generation - of the rotary wings. The reason for this is the presence of the opposite blind bore and the radial pressure-chamber connection channels. This eccentricity leads to a shortening of the effective spring length of the first stabilizer part and hence to an impairment of the spring rate.
There is therefore the problem of extending the effective spring length of the one stabilizer part of a stabilizer of the described type.
This problem is solved by the characterizing features of claim 1. Advantageous developments arise from the sub-claims 2 to 7.
The new divided stabilizer eliminates the described drawbacks of the background art.
In this case, the particular advantage lies in the optimum utilization of the spring length of the stabilizer part, because the axial centre of the force-transmitting length of the second stabilizer part and the axial centre of the force-transmitting length of the inner rotary part lie on a common radial plane. Thus, the effective spring length of the second stabilizer part is optimally extended and the effective length of the
4

outer rotary part is optimally shortened. The spring rate of the divided stabilizer is therefore improved relative to the comparable and closest prior art of US 5,700,027 to the extent provided in the case of a one-piece construction between the inner rotary part and the one stabilizer part according to DE 100 12 915 Al cited in the background art.
At the same time, compared to both US 5,700,027 and DE 100 12 915 Al manufacture of the new force-locking connection between the inner rotary part and the stabilizer part is simpler and more economical.
It is namely advantageous to construct the inner rotary part with a through fitting bore and the corresponding stabilizer part with a fitting cylinder and to equip this close-tolerance connection with negative play and shrink fit them to one another. This type of connection is very economical to manufacture because it allows the use of simple and conventional machining techniques.
It is alternatively also very advantageous to connect the inner rotary part by a gear part and a fitting part to a connection spigot of the corresponding stabilizer part, wherein both the gear part and the fitting part are manufactured with negative play and then shrunk on together. In said case, the shrunk gear and the shrunk fit are so designed that both types of connection are equally involved in the force transmission.
The use of a gear part leads first to the advantage that with the positive engagement the torsional safety increases. On the other hand, the gearing allows very precise and easy-to-handle alignment of the stabilizer part with the inner rotary part during assembly of the swivel motor.
This form of construction with a gear part and a fitting part is likewise very simple to manufacture because manufacture of the close-tolerance connection may be
5

effected by the conventional method and manufacture of the gearing in the inner rotary part may be effected by the simple and economical broaching method.
In the case of swivel motors having two or more pressure chambers and/or suction chambers, it is very advantageous for the two radial connection channels between the opposite pressure- and suction chambers of equal pressure to be introduced in the region of the play-free close-tolerance connection because then the radial connection channels are adequately sealed against leakage oil in an outward direction and from one another solely by the interference fit of the components involved. There is therefore no need for additional sealing elements.
For realizing the radial connection channels, for reasons of manufacture it is advantageous to provide the appropriate fitting bore of the inner rotary part with two juxtaposed annular channels and to connect these two annular channels in each case by radial channels to the pressure chambers or suction chambers.
The invention is now described in detail by way of two embodiments. For this purpose, the drawings show:
Fig. 1: a swivel motor in longitudinal section in a first embodiment,
Fig. 2: a swivel motor in longitudinal section in a second embodiment,
Fig. 3: the swivel motor of both embodiments in cross section and
Fig. 4: the swivel motor with a stabilizer part.
According to the said Figs. 1 to 4 a divided stabilizer comprises a first, non-illustrated stabilizer part and a second stabilizer part 1, which are both connected by a hydraulic swivel motor 2. In this case, the first, non-illustrated stabilizer part, the second stabilizer part 1 and the hydraulic swivel motor 2 are disposed on a common axle. The swivel motor 2 comprises an outer rotary part 3 and an inner rotary part 4, wherein the outer rotary part 3 has two outer rotary wings 5, which are connected in a fixed manner to the outer rotary part 3 and directed radially inwards, and the inner
6

rotary part 4 is configured with two adapted inner rotary wings 6, which are directed radially outwards. In this case, the outer rotary wings 5 and the inner rotary wings 6 in terms of their shape are so designed that they form between them
two opposite pressure chambers 7 and two likewise opposite suction chambers 8. In the region of these pressure chambers 7 and suction chambers 8, the outer rotary wings 5 and the inner rotary wings 6 are freely rotatable relative to one another until they come into mutual abutment. Axially, the pressure chambers 7 and the suction chambers 8 are delimited on the one hand by a bearing cover 9 and on the other hand by a flange cover 10, which are preferably welded in a pressure-tight manner to the outer rotary part 3. Shaft sealing elements 11 on the inner rotary part 4 and frame sealing parts 12 in the two outer rotary wings 5 and the two inner rotary wings 6 seal off the pressure chambers 7 and the suction chambers 8 in an outward direction and also from one another in an inward direction. The bearing cover 9 is equipped with an axial bearing bore, in which a corresponding bearing spigot 13 of the inner rotary part 4 is fitted.
In the first embodiment according to Fig. 1, the inner rotary part 4 and the second stabilizer part 1 are connected to one another in a particular manner by means of an interference fit. For this purpose, the inner rotary part 4 has a through fitting bore and the second stabilizer part 1 has a fitting cylinder 14, which is of a reduced diameter compared to the second stabilizer part 1 and extends over the entire axial length of the through fitting bore of the inner rotary part 4. The through fitting bore of the inner rotary part 4 and the fitting cylinder 14 of the stabilizer part 1 are manufactured with negative play relative to one another and connected to one another without play by means of a shrink-fit operation. In addition, the second stabilizer part 1 is connected to the inner rotary part 4 by means of a weld seam 15, which is situated in the front region of the free end of the fitting cylinder 14 of the second stabilizer part 1. By means of the shrunk close-tolerance connection and the welded joint the second stabilizer part 1 and the inner rotary part 4 are connected in
a force-locking manner to one another and are suitable for transmission of a corresponding torque.
7

The inner rotary part 4 has in its through fitting bore in the region of the shrunk-on fit a first radial annular channel 16 and a second radial annular channel 17, which are both spaced axially apart from one another and are covered in an inward direction by the fitting cylinder 14 of the second stabilizer part 1. The first radial annular channel 17 is connected by two radial channels 18 to the two opposite pressure chambers 7 or suction chambers 8 of the swivel motor, and the second radial annular channel 16 is connected by two radial channels 19 to the two opposite suction chambers 8 or pressure chambers 7. Thus, the respective two pressure chambers 7 and the respective two suction chambers 8 are of a pressure-equalized design, wherein the two radial annular channels 16, 17 by means of the interference fit between the fitting cylinder 14 of the second stabilizer part 1 and the inner rotary part 4 are sealed off in an outward direction and from one another in a pressure-tight manner against leakage oil.
In the second embodiment according to Fig. 2, the inner rotary part 4 and the second stabilizer part 1 are connected to one another in a particular manner by an interference fit and gearing. For this purpose, the inner rotary part 4 once again has a through bore and the stabilizer part 1 has a continuous connection spigot 20 of reducing diameter relative to the second stabilizer part 1, which both form a gear part 21 and a fitting part 22. The gear part 21 and the fitting part 22 are disposed axially alongside one another, wherein the gear part 21 is situated on the free end of the second stabilizer part 1. The gear part 21 comprises a suitable internal profile in the through bore of the inner rotary part 4 as well as a matching external profile on
the connection spigot 20 of the second stabilizer part 1, while the fitting part 22 comprises a fitting bore in the inner rotary part 4 as well as a fitting cylinder on the connection spigot 20 of the second stabilizer part 1.
In this case, the profile connection between the second stabilizer 1 and the inner rotary part 4 has a high tooth number in order to obtain, on the one hand, a high load capacity of the force-transmitting teeth and, on the other hand, a precise and sensitive alignment facility for assembly of the second stabilizer part 1 with the inner
8

rotary part 4. The external profile of the second stabilizer part 1 and the internal profile of the inner rotary part 4 as well as the fitting bore in the inner rotary part 4 and the fitting cylinder on the connection spigot 20 of the second stabilizer part 1 are constructed in each case with negative play relative to one another and fitted together without play by means of a shrink-fit operation. Thus, the second stabilizer part 1 and the inner rotary part 4 are connected to one another in a positively engaged and force-locking manner and are suitable for the transmission of corresponding torques. Disposed on the free end of the second stabilizer part 1 is a securing ring 23, which effects an additional axial interlock between the second stabilizer part 1 and the inner rotary part 4.
In this embodiment too, the inner rotary part 4 has in its through bore a first radial annular channel 16' and a second radial annular channel 17', which are both disposed in the fitting part 22 and spaced axially apart from one another. In this case, the first radial annular channel 16' is connected by the two radial channels 18' to the two opposite pressure chambers 7 or suction chambers 8, and the second radial annular channel 17' is connected by the two radial channels 19' to the two opposite suction chambers 8 or pressure chambers 7.
Thus, the respective two pressure chambers 7 and the respective two suction chambers 8 are of a pressure-equalized design, wherein both radial annular channels 16', 17' are covered by the fitting cylinder of the fitting part 22 and are sealed off against leakage oil in a pressure-tight manner in an outward direction and from one another by means of the interference fit between the fitting cylinder of the fitting part 22 and the inner rotary part 4.
9

List of reference characters

1 second stabilizer part
2 swivel motor
3 outer rotary part
4 inner rotary part
5 outer rotary wing
6 inner rotary wing
7 pressure chamber
8 suction chamber
9 bearing cover
10 flange cover
11 shaft sealing element
12 frame sealing element
13 bearing spigot
14 fitting cylinder
15 weld seam
16,16' first radial annular channel
17,17' second radial annular channel
18,18' radial channel
19,197 radial channel
20 connection spigot
21 gear part
22 fitting part
23 securing ring
10

WE CLAIM:
1. Divided stabilizer with optimized spring rate, comprising a first stabilizer part, a second stabilizer part (1) and a swivel motor (2), all of which are disposed on a common axle, wherein the swivel motor (2) comprises an outer rotary part (3) and an inner rotary part (4), which in interaction with a bearing cover (9) and a flange cover (10) form at least one pressure chamber (7) and one suction chamber (8), and the outer rotary part (3) of the swivel motor (2) is connected in a rotationally fixed manner to the first stabilizer part and between the inner rotary part (4) of the swivel motor (2) and the second stabilizer part (1) there is a force-transmitting connection, characterized in that the inner rotary part (4) and the second stabilizer part (1) are connected in a force-locking manner to one another and the force-locking connection is so designed that the axial centre of the force-transmitting length of the second stabilizer part (1) and the axial centre of the force-transmitting length of the inner rotary part (4) lie on a common radial plane.
2. Divided stabilizer according to claim 1, characterized in that the force-locking connection between the inner rotary part (4) and a fitting cylinder (14) of the second stabilizer part (1) comprises a shrink-on fit.
3. Divided stabilizer according to claim 2, characterized in that the inner rotary part (4) and the fitting cylinder (14) are additionally connected by a weld seam (15), wherein the weld seam (15) is situated on the free end of the fitting cylinder (14).
4. Divided stabilizer according to claim 1, characterized in that the force-locking connection between the inner rotary part (4) and a connection spigot (20) of the second stabilizer part (1) comprises a gear part (21) and a fitting part (22), which are both shrunk on.
11

5. Divided stabilizer according to claim 4, characterized in that the inner rotary part (4) and the connection spigot (20) are additionally axially secured by means of a securing ring (23).
6. Divided stabilizer according to claim 2 or 4, in which the swivel motor (2) has two or more opposite pressure chambers (7) and two or more opposite suction chambers (8) and the pressure chambers (7) and the suction chambers (8) are connected in each case by a radial connection channel, characterized in that the radial connection channels are introduced in the region of the play-free close-tolerance connection between the inner rotary part (4) and the second stabilizer part(l).
7. Divided stabilizer according to claim 6, characterized in that the through bore of the inner rotary part (4) has in the region of its fitting part (22) two juxtaposed annular channels (16,16', 17,17'), which are covered by the fitting cylinder (14) or by the fitting part (22) of the connection spigot (20) and which are connected by radial channels (18,18', 19,19') to the corresponding pressure chambers (7) or suction chambers (8).
12
Dated this 9th day of January, 2007


Abstract
To improve the spring rate of a stabilizer of the described type, the spring length of a stabilizer part is to be extended.
For this purpose, it is proposed that the inner rotary part 4 of a swivel motor 2 and the second stabilizer part 1 are connected in a force-locking manner to one another and the force-locking connection is so designed that the axial centre of the force-transmitting length of the second stabilizer part 1 and the axial centre of the force-transmitting length of the inner rotary part 4 He on a common radial plane.
In this case, the force-locking connection between the inner rotary part 4 and a fitting cylinder 14 of the second stabilizer part 1 is formed either by a shrunk-on fit or by a
gear part 21 and a fitting part 22, wherein the gear part 21 and the fitting part 22 are likewise shrunk on.
To
The Controller of Patents
The Patent Office
13
Mumbai