Pressure piece for a rack and pinion steering gear for a vehicle

Abstract

Rack and pinion steering gear for a vehicle with a rack (3) axially displaceably mounted in a steering gear housing (2), into which a rotatable drive pinion engages, and at least one pressure piece (5, 15) supported on the steering gear housing (2), which presses the rack (3) against the drive pinion and is mounted on a rack back (6) via at least one rolling element (10) rotatably mounted on the pressure piece (5, 15), characterized in that the rolling element (10) is in contact with the pressure piece (5, 15) and is mounted in a ball socket (14) connected to the pressure piece (5, 15) by means of bearing balls (13) and is held by the ball socket (14), wherein the rolling element (10) together with the bearing balls (13), which are considerably smaller than the rolling element (10), is located within the cavity bounded by the ball socket (14), and wherein the rack back (6) at least one deepened,The rolling element raceway (11) is designed as a groove- or slot-shaped recess extending in the axial direction of the rack (3), in which the rolling element (10), which is designed as a ball, is guided, wherein the rolling element raceway (11) has a width on the circumferential surface of the rack back (6) that is smaller than the diameter of the ball, wherein the ball rolls on the lateral edges or edge sections of the rolling element raceway (11), and wherein the ball socket (14) has an opening with a diameter that is smaller than a diameter of the rolling element (10), wherein the rolling element (10) extends through the opening with that part which is supported on the rolling element raceway (11) of the rack back (6) and rolls on it.

Description

[0001] The present invention relates to a rack and pinion steering gear for a vehicle, in particular a motor vehicle, according to the preamble of claim 1.

[0002] According to the generic KR 10 2008 0 036 474 A, a steering gear for a vehicle has a rack bearing with a hollow cylindrical rack housing, a rack, a pinion, a thrust piece, a plug, a spring, and a ball. The rack slides from one side to the other in the rack housing. The pinion is toothed and engages one side of the rack to transmit the torsional force to the rack. The thrust piece, one surface of which is shaped like an arc, is arranged on a part of the peripheral surface of the rack to press the rack against the pinion. The elastic spring is formed on a surface of the plug and elastically supports the thrust piece. The ball is inserted between the rack and the thrust piece.

[0003] The KR 20 0 285 616 Y1 relates to a support yoke and a rack play damping device for a vehicle, in which a rack which slides laterally according to the rotational movement of a rack and pinion gear and a support yoke which supports the rack, wherein the rack and the support yoke are designed by the combination of balls between support yokes so that the rack can slide.

[0004] A pinion shaft rotated via a steering wheel according to DE 10 2006 008 269 A1 has a gear transmission formed thereon. A rack has a front surface on which a toothed rack portion engages with the gear transmission. A rotating element is arranged to support the rear surface of the rack, which rotates when the rack moves axially. A biasing mechanism biases the rotating element to a momentarily engaged region between the toothed rack portion and the rack transmission. A bearing element is arranged to slidably support the rear surface of the rack.

[0005] DE 101 07 740 A1 discloses a rack and pinion steering system for motor vehicles, comprising a steering housing in which a steering pinion is rotatably mounted, and a rack which is displaceably mounted in the steering housing and which engages with the steering pinion by means of a toothing such that rotation of the steering pinion leads to a displacement of the rack in the direction of its longitudinal axis, and wherein a pressure piece is further provided in the region of the engagement, which pressure piece absorbs a normal force acting on the rack when the engagement is loaded with a torque and urges the rack towards the steering pinion, wherein the pressure piece has at least a first load-bearing region which bears against the rack when the normal force is low, and wherein at least a second load-bearing region is further provided which comes into contact with the rack when the normal force increases and enlarges the load-bearing surface of the pressure piece.

[0006] DE 10 2004 051 494 A1 relates to a steering gear for a motor vehicle, comprising a steering housing, a rack guided displaceably within the steering housing over a steering travel, a rotatable steering pinion meshing with the rack, and a first pressure piece. The rack can be subjected to a force in the direction of the steering pinion by means of the first pressure piece. The rack can be subjected to a force in the direction of the steering pinion by means of a second pressure piece, at least over a portion of the steering travel.

[0007] DE 100 63 877 A1 relates to a rack and pinion steering gear with a steering gear housing, with a rack which is arranged in the steering gear housing so as to be displaceable along a longitudinal axis and which has a first toothing, with a pinion which is arranged rotatably in the steering gear housing and which has a second toothing which engages with the first toothing of the rack, with a linear rolling bearing unit which is arranged between a wall of the steering gear housing and a supporting surface of the rack opposite the pinion and supporting the rack relative to the steering gear housing.

[0008] The abstract of JP 2007 112 276 A describes a rack and pinion steering gear in which rotation of the rack about its own axis is to be prevented. For this purpose, the rack has a groove with a rounded groove base. A barrel-shaped, convex surface of a rolling element fits into the groove so that it is filled.

[0009] US Pat. No. 4,531,603 A discloses a rack-and-pinion steering gear comprising balls arranged in a row. The balls are guided into and out of a linear guide of the rack. This reduces sliding friction between the rack and its bearing, while simultaneously preventing twisting of the rack due to torque loads. The balls are inserted into the linear guide, the base of which is designed to match the radius of the balls, in such a way that this linear guide is filled in the contact area of ​​the balls.

[0010] GB 1 168 191 A also discloses a rack and pinion steering system. A rolling element is designed as a ball, which is mounted in the housing. The ball engages in an axially formed recess in the rack. The recess is complementary, i.e., designed to match the ball. Thus, the ball engages the recess with the corresponding contact section in such a way that it is completely filled.

[0011] Likewise, US 2002 / 0 084 136 A1 discloses in one embodiment that a ball engages in a recess of a rack adapted thereto.

[0012] Rack and pinion steering gears are used in a manner known per se to transmit the rotary movement of a steering wheel, which is connected, for example, via a steering shaft in a rotationally fixed manner to the drive pinion of the rack and pinion steering gear, to the rack which is mounted axially displaceably in the steering gear housing, which rack and pinion moves axially as a result of a rotation of the drive pinion and the toothed engagement between the drive pinion and the rack and pivots the wheels of the vehicle connected to the wheel carriers via a steering linkage coupled to the axial ends of the rack, which in turn is connected to a wheel carrier.

[0013] To prevent separation of the drive pinion teeth and the rack teeth due to the radial forces acting during torque transmission between the drive pinion and the rack, and to keep the meshing engagement as free of play as possible, it is also known to press the rack against the drive pinion using a thrust piece, usually supported on the steering gear housing. To ensure the axial displacement of the rack in the steering gear housing, the thrust piece is conventionally mounted on a plain bearing at the back of the rack. However, this plain bearing naturally causes friction between the thrust piece and the rack during steering movements, which can adversely affect the steering feel perceived by the driver.

[0014] To reduce friction between the thrust piece and the rack, steering gears are also known from the prior art in which the thrust piece is mounted on a roller bearing at the rack back. For example, JP 2001260905 A discloses a rack and pinion steering gear in which rolling elements in the form of balls are arranged between a circumferential surface of a rack back and a concave surface of a thrust piece facing the rack back. The balls are mounted in receiving openings of a bearing seat on the thrust piece, which is axially displaceably accommodated in the thrust piece. The bearing seat can be preloaded against the rack back by means of a spring element.

[0015] A similar rack-and-pinion steering gear is described in JP 2001 328 547 A. Here, too, balls are freely rotatably mounted in a bearing seat, which is axially displaceably accommodated in a thrust piece. The balls are arranged between a circumferential surface of a rack back and a concave surface of the thrust piece facing the rack back. The bearing seat has a conical surface for receiving the balls and can be preloaded against the rack back by means of a spring element.

[0016] Furthermore, a rack and pinion steering gear is known from US Pat. No. 7,032,470 B2, in which a rack is pressed against a drive pinion by means of a ball bearing comprising several balls. The ball bearing has an inner ring with a C-shaped cross section that surrounds the back of the rack. The ball bearing balls are freely rotatably received in holes distributed on the inner ring. They roll between the circumferential surface of the back of the rack and an inner surface of an outer ring surrounding the inner ring. The outer ring is immovably mounted on a steering gear housing. Upon axial displacement of the rack in the steering gear housing, the inner ring of the ball bearing also moves in the axial direction with the rack due to the rolling movement of the ball bearing balls. Rotation of the inner ring around the rack is prevented by a pin formed on the inner ring, which is guided in an axially extending slot in the outer ring.The outer ring of the ball bearing can be preloaded against the rack via a pressure piece that is spring-supported on the steering gear housing.

[0017] The above-described bearings of the thrust piece on the rack are capable of reducing the friction occurring between the thrust piece and the rack compared to a conventional plain bearing. In addition to the problem of friction occurring between the thrust piece and the rack during steering movements, the rack can, however, rotate about its longitudinal axis as a result of forces acting on the meshing between the drive pinion and the rack, which generally depend on the current steering angle, and / or forces transmitted to the rack via the steering linkage. Such rotation of the rack is not prevented by the known bearings of the thrust piece on the rack.However, the rotation of the rack deteriorates the meshing between the drive pinion and the rack, leading, for example, to uneven wear of the respective gears and consequently to faster wear of the rack and pinion steering gear. Likewise, such rotation of the rack around its longitudinal axis can lead to undesirable rattling noises.

[0018] Against this background, the object of the invention is to provide a rack and pinion steering gear for a vehicle, in particular a motor vehicle, which during steering movements, i.e. during axial displacements of a rack in a steering housing, has low friction between a pressure piece urging the rack against a drive pinion and the rack and at the same time reliably prevents rotation of the rack about its longitudinal axis with little structural outlay.

[0019] This object is achieved by a rack and pinion steering gear having the features of claim 1.

[0020] A rack and pinion steering gear for a vehicle is shown, comprising a rack mounted axially displaceably in a steering gear housing, into which a rotatable drive pinion engages, and at least one thrust piece supported on the steering gear housing, which thrusts the rack against the drive pinion and is roller-mounted on a rack back via at least one rolling element rotatably mounted on the thrust piece. The thrust piece is characterized in that the rolling element is contact-free with the thrust piece and is mounted by means of bearing balls in a ball socket connected to the thrust piece and is held by the ball socket. The rolling element, together with the bearing balls which are considerably smaller than the rolling element, is located within the cavity defined by the ball socket. The rack back has at least one recessed rolling element raceway designed as a groove- or slot-shaped recess and extending in the axial direction of the rack.in which the rolling element, which is designed as a ball, is guided, wherein the rolling element raceway on the circumferential surface of the rack back has a width that is smaller than the diameter of the ball, wherein the ball rolls on the lateral edges or edge sections of the rolling element raceway, and wherein the ball socket has an opening with a diameter that is smaller than a diameter of the rolling element, wherein the rolling element extends through the opening with that part that is mounted on the rolling element raceway of the rack back and rolls on it.

[0021] Further, particularly advantageous embodiments of the invention are disclosed in the subclaims.

[0022] A rack and pinion steering gear for a vehicle, in particular a motor vehicle, comprises a rack mounted axially displaceably in a steering gear housing, into which a rotatable drive pinion engages, and at least one thrust piece supported on the steering gear housing, which urges the rack against the drive pinion and is roller-mounted on a rack back via at least one rolling element rotatably mounted on the thrust piece. Furthermore, the rack back of the rack and pinion steering gear has at least one recessed rolling element raceway extending in the axial direction of the rack, in which the rolling element is guided.

[0023] According to the present invention, the rack back is understood to be the area of ​​the rack circumference adjacent to or opposite the rack teeth. The recessed rolling element raceway formed in the rack back is a groove- or slot-shaped recess, whereby the specific cross-sectional shape of the raceway, for example, circular, ellipsoidal, wedge- or trapezoidal, rectangular, etc., as well as its exact width and depth, are expediently selected according to the shape and size of the rolling element(s) guided in the raceway. In principle, all rolling elements known per se, for example those used for conventional rolling bearings, are suitable as rolling elements in the present invention, for example, balls, cylinders, needles, barrels, and the like.

[0024] Since the rolling element raceway in the rack back extends essentially in the axial direction of the rack, i.e., in its longitudinal direction, the rolling element guided in the raceway can roll along the rolling element raceway with low friction when the rack is axially displaced in the steering gear housing. The rolling element is therefore guided by the rolling element raceway in the axial direction of the rack, but rolling of the rolling element on the rack back in the tangential or circumferential direction of the rack is prevented. Accordingly, rotation of the rack about its longitudinal axis is effectively blocked by the rolling element guided in the rolling element raceway.

[0025] Furthermore, the rolling element is also rotatably mounted on the thrust piece. Consequently, the rolling element's degrees of freedom of movement are also restricted at the thrust piece, although rotation of the rolling element at the thrust piece is permitted in the direction in which the rolling element rolls along the rolling element raceway provided on the back of the rack upon axial displacement of the rack, as described above.

[0026] For example, a rolling element raceway could be provided on the thrust piece to guide the rolling element, similar to the raceway formed in the rack back. In this case, the rolling element raceway in the thrust piece would run parallel to the rolling element raceway of the rack back to enable rotation-free axial displacement of the rack. Furthermore, the length of the rolling element raceway provided on the thrust piece would have to be dimensioned such that rolling of the rolling element between the rack back and the thrust piece would be ensured during a maximum axial displacement of the rack to both sides corresponding to a maximum steering angle. Such a mounting of the rolling element on the thrust piece would thus allow a rotational movement of the rolling element and additionally a translational movement of the rolling element in the axial direction of the rack.However, rolling of the rolling element on the thrust piece in the lateral direction (direction perpendicular to the longitudinal axis of the rack) would be prevented by the guidance of the rolling element raceway on the thrust piece and consequently the rotation of the rack about its longitudinal axis.

[0027] On the one hand, the rolling bearing of the thrust piece on the back of the rack ensures low friction between these components during axial displacement of the rack. At the same time, the rolling elements required for the rolling bearing effectively prevent the rack from rotating around its longitudinal axis. This eliminates the need for additional structural measures to prevent rack rotation.

[0028] The rolling element rotatably mounted on the thrust piece exclusively possesses at least one rotational degree of freedom. Since the rolling element therefore has no translational degree of freedom, no installation space needs to be provided in the steering gear housing or on the thrust piece for a linear movement of the rolling element on the thrust piece, as is the case, for example, with the previously described rolling element raceway on the thrust piece. The steering gear housing is thus more compact. The at least one rotational degree of freedom of the rolling element must be designed such that rotation of the rolling element on the thrust piece is always possible in the direction in which the rolling element rolls on the rolling element raceway on the back of the rack upon axial displacement of the rack, as already described.

[0029] As an example of a rotatable bearing of the rolling element on the pressure piece, which has exclusively at least one rotational and no translational degree of freedom, the bearing of the rolling element on a shaft connected to the pressure piece may be mentioned, wherein the direction of rotation of the rolling element is to be determined in the manner described above.

[0030] The rolling element is intended to be a ball that is mounted by means of bearing balls in a ball socket connected to the thrust piece and held by the ball socket. The ball rolls on the bearing balls, with the bearing balls in turn rolling on the inner wall of the ball socket. In this way, the ball used as a rolling element has only rotational degrees of freedom. It can move freely in any direction of rotation, including the direction of rotation in which the ball rolls on the rolling element raceway of the rack back when the rack is axially displaced. Since the ball can rotate freely in all directions in the ball socket, no specific alignment of the rolling element mounted on the thrust piece with respect to the rolling element raceway of the rack running on the rack back is necessary, as is the case, for example, if the rolling element only has one rotational degree of freedom.This significantly simplifies the assembly of the rack-and-pinion steering gear according to the invention. Furthermore, the ball bearings in the ball socket enable a particularly low-friction, low-wear, rotatable mounting of the rolling element on the thrust piece.

[0031] The rolling element is a ball, and the recessed rolling element raceway incorporated into the rack back has a width on the circumferential surface of the rack back that is smaller than the diameter of the ball. Thus, the ball used as a rolling element is not completely accommodated in the rolling element raceway, which may, for example, have a circular cross-section, but rather rolls on the lateral edges or edge sections of the rolling element raceway. This enables a particularly easy-to-manufacture, play-free bearing of the rolling element on the rolling element raceway, which is also particularly advantageously insensitive to production-related component deviations of the rolling element and the rolling element raceway. This ensures precise axial guidance of the rolling element on the rack back during axial displacement of the rack. Furthermore, any rotation of the rack about its longitudinal axis is reliably prevented.Also important in this context is that the rolling element, together with the bearing balls, is located within the cavity defined by the ball socket, with the ball socket having an opening with a diameter smaller than the diameter of the rolling element. The part of the rolling element that is mounted on the rolling element raceway of the rack back and rolls on it extends through this opening.

[0032] A further advantageous embodiment of the invention provides that the thrust piece can be elastically preloaded in the direction of the rack back by means of at least one spring element. This allows the thrust piece to be held in play-free and quiet contact with the rack back via the rolling element. Furthermore, the spring force can be used to adjust the pressure with which the thrust piece presses the rack against the drive pinion. The elastic preload also allows the thrust piece to effectively absorb shock loads, which, if the thrust piece were rigidly mounted, could potentially cause damage to the rolling element raceway, the rolling element, or the thrust piece itself. Furthermore, the elastic preload of the thrust piece against the rack ensures automatic wear compensation.Manual readjustment of the gear engagement, i.e., the drive pinion-to-rack connection, is thus eliminated. Furthermore, the spring-loaded pressure piece allows manufacturing-related tolerances in the drive pinion-to-rack connection to be easily compensated, thereby simplifying the manufacturing process of the rack-and-pinion steering gear according to the invention and significantly reducing assembly and maintenance costs.

[0033] A further advantageous embodiment of the invention provides that the thrust piece is mounted in a support of the steering gear housing so that it can be displaced axially in the direction of the rack back, in particular by means of a sliding bearing, a roller bearing, or a ball bearing. On the one hand, this enables simple installation of the thrust piece in the steering gear housing. On the other hand, this mounting of the thrust piece on the steering gear housing ensures simple and precise positioning of the rolling element mounted on the thrust piece with respect to the rolling element raceway of the rack back. Tilting of the thrust piece and thus of the rolling element mounted on it is effectively prevented. Furthermore, the axial displaceability of the thrust piece in the steering gear housing advantageously allows tolerances in the rack to be compensated for.

[0034] A further advantageous embodiment of the invention provides that the axial movement of the thrust piece away from the rack back is limited by an end stop provided on the thrust piece, which can be supported against the steering gear housing. The end stop ensures that the rolling element mounted on the thrust piece cannot leave the rolling element raceway on the rack back, for example, in the event of high lateral or transverse forces. Furthermore, the end stop determines the maximum compensation travel for the axial displacement of the thrust piece to compensate for the rack tolerances, as mentioned above.For this purpose, the end stop of the thrust piece can be advantageously supported on a closure that can be screwed into the socket of the steering gear housing from the outside. The maximum possible axial displacement of the thrust piece in the socket of the steering gear housing, i.e., the maximum play between the end stop of the thrust piece and a stop surface of the closure, can be adjusted via the screw-in depth of the closure into the steering gear housing. In this way, for example, during assembly of the rack and pinion steering gear according to the invention, the maximum deviation of the rack can first be measured, and then the play between the end stop of the thrust piece and the stop surface of the closure can be adjusted to this value.

[0035] To further reduce wear and friction in the rolling bearing between the thrust piece and the rack, an advantageous embodiment of the invention further provides for the rolling element raceway to be hardened. Furthermore, with a hardened rolling element raceway, higher forces can be transmitted via the rolling element between the rack and the thrust piece. In other words, compared to conventional rack-and-pinion steering gears, the thrust piece can press the rack against the drive pinion with greater force while maintaining relatively low friction between the thrust piece and the rack, thus improving the meshing engagement between the rack and the drive pinion for transmitting higher torques, which can occur, for example, under shock loads.

[0036] Further advantageous details and effects of the invention are explained in more detail below with reference to exemplary embodiments illustrated in the figures. They show: Fig. 1 is a schematic side cross-sectional view of a first embodiment of a rack and pinion steering gear according to the invention, Fig. 2 a schematic side view and a plan view of a pressure piece of a second embodiment of a rack and pinion steering gear according to the invention, Fig. 3 is a schematic side cross-sectional view of a third embodiment of a rack and pinion steering gear according to the invention, and Fig. 4 a schematic side cross-sectional view of a fourth embodiment of a rack and pinion steering gear according to the invention.

[0037] In the different figures, identical parts are always provided with the same reference symbols, so that they are usually only described once.

[0038] In Fig. Figure 1 shows a schematic side cross-sectional view of a rack and pinion steering gear 1 for a vehicle, in particular a motor vehicle, according to a first exemplary embodiment. The rack and pinion steering gear 1 essentially comprises a Fig. 1 not fully shown steering gear housing 2 axially displaceably mounted rack 3, into which a also in Fig. 1, a rotatable drive pinion (not shown) engages. The teeth of the drive pinion engage in a known manner with a toothed section 4 of the rack 3, whereby the drive pinion and the rack 3 form a toothed engagement.

[0039] Although it is in Fig. 1, the drive pinion of the rack and pinion steering gear 1 is connected to a steering wheel of the vehicle, for example, via a steering shaft connected thereto in a rotationally fixed manner. Likewise, the axial ends of the rack and pinion steering gear 3 are coupled to respective wheel carriers of the vehicle, for example, via a steering linkage or tie rods, so that the rack and pinion steering gear 1 initially translates steering movements of a driver on the steering wheel into an axial displacement movement of the rack and pinion 3 and further into corresponding pivoting movements of the vehicle wheels connected to the wheel carriers.

[0040] As in Fig. 1, the rack and pinion steering gear 1 further comprises a pressure piece 5 supported on the steering gear housing 2, which presses the rack 3 against the drive pinion, as shown in Fig. 1 is indicated by a force arrow F arranged on the pressure piece 5.

[0041] In the Fig. In the exemplary embodiment of the rack and pinion steering gear 1 according to the invention shown in Figure 1, the thrust piece 5 is mounted, in particular in a socket of the steering gear housing 2, axially in the direction of the rack 3 or its rack back 6, which is characterized by the area of ​​the rack circumference of the rack 3 adjacent to and opposite the toothed section 4, displaceably mounted, for example in a simple manner with a sliding bearing, wherein the axial movement of the thrust piece 5 away from the rack back 6 is limited by an end stop 7 provided on the thrust piece 5. As Fig. 1, the end stop 7 is supported on the steering gear housing 2 by means of a closure 8 which can be screwed into the socket of the steering gear housing 2 from the outside. In addition, the pressure piece 5 in the Fig. 1, the spring element 9, for example a helical or disc spring, is elastically prestressed in the direction of the rack 3 by a spring element 9 arranged between the pressure piece 5 and the closure 8.

[0042] How Fig. As can be seen in Figure 1, a rolling element 10 in the form of a ball is arranged between the pressure piece 5 and the rack 3 or the rack back 6 of the rack 3. The rolling element 10 is rotatably mounted on the one hand on the pressure piece 5 and on the other hand on the rack back 6. As shown in Fig. As can be clearly seen in Figure 1, the rack back 6 of the rack and pinion steering gear 1 has a recessed rolling element raceway 11 extending in the axial direction of the rack 3. The ball, designed as a rolling element 10, is guided in this raceway.

[0043] The rolling element raceway 11 has in the Fig. 1 has an ellipsoidal cross-sectional shape, wherein the rolling element raceway 11 on the circumferential surface of the rack back 6 has a width that is smaller than the diameter of the ball 10. Consequently, the ball 10 is not completely received in the rolling element raceway 11, but only partially and rolls on the lateral edges 12 or edge sections of the rolling element raceway 11, as also shown in Fig. 1 is represented by corresponding force arrows F on the edges 12. This type of bearing of the rolling element 10 on the rolling element raceway 11 allows a play-free and precise guidance of the rolling element 10 on the rack back 6 during an axial displacement of the rack 3. Rotation of the rack 3 about its longitudinal axis is reliably prevented by the rolling element 10, since it forms a positive connection with the edges 12 of the rolling element raceway 11 with respect to a rotation of the rack 3 about its longitudinal axis.

[0044] In Fig. 1 it can also be seen that the ball used as rolling element 10 in the rack and pinion steering gear 1 is rotatably mounted by means of bearing balls 13 in a ball socket 14 connected to the pressure piece 5. The ball 10 rolls on the bearing balls 13, which have a smaller diameter than the ball 10, with the bearing balls 13 in turn rolling on the inside of the ball socket 14. Furthermore, the ball 10 is held by the ball socket 14. For this purpose, the ball 10, together with the bearing balls 13, is located within the cavity delimited by the ball socket 14, with the ball socket 14 having an opening with a diameter that is smaller than the diameter of the ball 10. That part of the ball 10 which is mounted on the rolling element raceway 11 of the rack back 6 and rolls on this extends through this opening.

[0045] The type of rotatable mounting of the ball 10 on the thrust piece 5 by means of the ball socket 14 and the bearing balls 13 used in the rack and pinion steering gear 1 according to the invention grants the ball 10 exclusively rotational degrees of freedom, but in any desired direction of rotation. Thus, upon axial displacement of the rack 3, the ball 10 can always rotate in the direction in which the ball 10 rolls on the rolling element raceway 11. However, rotation of the rack 3 about its longitudinal axis is prevented because the ball 10 is held by the ball socket 14 and the thrust piece 5, which is only axially guided in the socket of the steering gear housing 2. Lateral tilting of the ball 10 is prevented by the above-described mounting on the thrust piece 5.

[0046] In Fig. 2 is on the left side a schematic side view and on the right side a plan view of a pressure piece 15 of a second embodiment of a Fig. 2 not shown in detail, according to the invention. The pressure piece 15 differs from that shown in Fig. 1 essentially in that, next to the rolling element 10 rotatably mounted on the pressure piece 15, additional support elements 16 are provided, directed in the direction of the rack back 6. As Fig. As can be seen from Figure 2, the support elements 16 are pin-shaped in the illustrated embodiment. They serve to restrict the movements, in particular rotational movements, of the rack 3 and thus to support the rack 3 at its rack back 6 in the event that the rolling element bearing of the thrust piece 15 at the rack back 6 is damaged and its actual function is no longer fulfilled. This could be the case, for example, if the rolling element 10 or its bearing on the thrust piece 15 is damaged, or if the bearing of the thrust piece 15 in the steering gear housing 2 is damaged. The support elements 16 thus represent a safety precaution for the aforementioned case.

[0047] A schematic side cross-sectional view of a third embodiment of a rack and pinion steering gear 17 according to the invention is shown in Fig. 3. The rack and pinion steering gear 17 differs essentially from that shown in Fig. 1 shown rack and pinion steering gear 1 in that two recessed, parallel rolling element raceways 11 running in the axial direction of the rack 3 are introduced into the rack back 6 of the rack 3 and accordingly two pressure pieces 5 are each connected to a rolling element 10 on the rack back 6, as already explained above in the explanation of the Fig. 1, are mounted on roller bearings. The thrust pieces 5 are each mounted on the steering gear housing 2 in the manner described above, for example, on sliding or ball bearings that are displaceable in their respective axial directions.

[0048] In Fig. 4 shows a schematic side cross-sectional view of a fourth embodiment of a rack and pinion steering gear 18 according to the invention. The rack and pinion steering gear 18 differs from that shown in Fig. 1 shown rack and pinion steering gear 1 essentially in that the pressure piece 5, on which the rolling element 10 is rotatably mounted, is accommodated in a further pressure piece 19 and is supported on the steering gear housing 2 via this pressure piece 19. As the Fig. 4, the pressure piece 19 is similar in shape to the pressure pieces known from conventional rack and pinion steering gears. In particular, it has support elements 20 on the surface facing the rack back 6, which are designed in a conventional manner as support surfaces corresponding to the shape of the rack back 6. These support elements or support surfaces 20 also serve, like the Fig. 2 merely as a safety precaution in the event that there is damage to the rolling bearing of the pressure piece 5 on the rack back 6, as already explained in the description of the Fig. 2. The support elements 20 are then able to support the rack back 6 and continue to guide the rack 3 in the same manner as is the case with previously known rack and pinion steering gears.

[0049] In the Fig. In the exemplary embodiment of the rack and pinion steering gear 18 according to the invention shown in Figure 4, the thrust piece 5 is mounted in a central bore of the thrust piece 19 so as to be axially displaceable in the direction of the rack 3 or the rack back 6, for example, with a sliding or ball bearing. The axial movement of the thrust piece 5 away from the rack back 6 is limited by an end stop 7 provided on the thrust piece 5, which, as in the case of the Fig. 1, the pressure piece 5 can be supported on the steering gear housing 2 by means of a closure 8 that can be screwed into the socket of the steering gear housing 2 from the outside. Furthermore, the pressure piece 5 is also elastically prestressed in the direction of the rack 3 by means of a spring element 9 arranged between the pressure piece 5 and the closure 8. In the embodiment shown in Fig. 4, in which the pressure piece 5 is, for example, slide-mounted in the pressure piece 19, the pressure piece 19 can be pressed into the socket of the steering gear housing 2, for example, by means of a press fit. However, it can also be mounted axially displaceably in the socket of the steering gear housing 2, for example, with a slide or ball bearing. In particular, with an axially displaceable mounting of the pressure piece 19 in the socket of the steering gear housing 2, the pressure piece 5 can be pressed into the bore of the pressure piece 19. The further functions of the Fig. 4 have already been explained in connection with the explanation of the Fig. 1 and also apply to this embodiment.

[0050] Another significant advantage of the Fig. 4 is that existing rack and pinion steering gears can be converted to the rack and pinion steering gear 18 according to the invention without any changes to the steering gear housing 2.

[0051] The rack and pinion steering gear according to the invention described above is not limited to the embodiments disclosed herein, but also includes other embodiments with the same effect. In particular, the rack and pinion steering gear according to the invention is not limited to the number of rolling elements described herein or the number of rolling element raceways incorporated in the rack back. For example, a plurality of rolling elements can be rotatably mounted on the pressure piece, which are guided, for example, in a linearly distributed manner in a single rolling element raceway of the rack back or in separate rolling element raceways arranged distributed around the circumference of the rack back. Of course, a combination of a plurality of rolling elements per rolling element raceway and a plurality of rolling element raceways distributed around the circumference of the rack back is also conceivable. Furthermore, the provision of a plurality of pressure pieces, each of which rotatably supports only one rolling element, is also possible, wherein the rolling elements orThe thrust pieces can, in turn, be arranged on the back of the rack in the manner described above. Furthermore, the cross-sectional shape of the rolling element raceway is, of course, not limited to the ellipsoidal cross-sectional shape shown here, but includes any other cross-sectional shape suitable for a rolling element raceway, for example, circular, wedge-shaped, trapezoidal, rectangular, and the like.

[0052] In a preferred embodiment, the rack and pinion steering gear according to the invention is used in a vehicle, in particular a motor vehicle, for transmitting the steering movements of a driver to the steerable vehicle wheels, particularly preferably together with an electrically operated power steering system (EPAS) of the vehicle. List of reference symbols: 1 rack and pinion steering gear 2 steering gear housing, nozzle 3 rack 4 Gear section 5 Pressure piece 6 rack backs 7 End stop 8 Closure 9 Spring element 10 rolling elements 11 Rolling element raceway 12 Side edges of 11 13 bearing balls 14 ball socket 15 Pressure piece 16 support elements 17 Rack and pinion steering gear 18 rack and pinion steering gear 19 Pressure piece 20 support elements F Force Arrow

Claims

[1] Rack and pinion steering gear for a vehicle with a rack (3) which is mounted axially displaceably in a steering gear housing (2) and into which a rotatable drive pinion engages, and at least one pressure piece (5, 15) supported on the steering gear housing (2), which pressure piece urges the rack (3) against the drive pinion and is mounted on a rack back (6) by means of a roller bearing via at least one rolling element (10) rotatably mounted on the pressure piece (5, 15), characterized bythat the rolling element (10) is contact-free with the pressure piece (5, 15) and is mounted by means of bearing balls (13) in a ball socket (14) connected to the pressure piece (5, 15) and is held by the ball socket (14), wherein the rolling element (10) together with the bearing balls (13), which are considerably smaller in relation to the rolling element (10), is located within the cavity delimited by the ball socket (14), and wherein the rack back (6) has at least one recessed rolling element raceway (11) designed as a groove- or slot-shaped recess, running in the axial direction of the rack (3), in which the rolling element (10), which is designed as a ball, is guided, wherein the rolling element raceway (11) has a width on the circumferential surface of the rack back (6) which is smaller than the diameter of the ball, wherein the ball is supported on the lateral edges or edge sections of the Rolling element raceway (11) rolls,and wherein the ball socket (14) has an opening with a diameter which is smaller than a diameter of the rolling element (10), wherein the rolling element (10) extends through the opening with that part which is mounted on the rolling element raceway (11) of the rack back (6) and rolls on this. [2] Rack and pinion steering gear according to claim 1, characterized by that the rolling element (10) rotatably mounted on the pressure piece (5,15) has exclusively at least one rotational degree of freedom. [3] Rack and pinion steering gear according to claim 1 or 2, characterized by that the pressure piece (5,15) can be elastically prestressed in the direction of the rack back (6) by means of at least one spring element (9). [4] Rack and pinion steering gear according to one of the preceding claims, characterized by that the pressure piece (5,15) is mounted in a socket of the steering gear housing (2) so as to be axially displaceable in the direction of the rack back (6). [5] Rack and pinion steering gear according to claim 4, characterized by that the axial movement of the pressure piece (5,15) away from the rack back (6) is limited by an end stop (7) provided on the pressure piece (5,15) which can be supported against the steering gear housing (2). [6] Rack and pinion steering gear according to one of the preceding claims, characterized by that the rolling element raceway (11) is hardened.

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