Technical field

[0001] The present invention relates to the technical field of motor vehicle manufacture; specifically, the present invention relates to a motor vehicle steering gear, and further relates to a motor vehicle comprising same.

Background art

[0002] Motor vehicles are a common means of transportation in modern life. [0003] The steering gear of a motor vehicle is an important component of the motor vehicle’s steering system; the function thereof is to increase the force or torque transmitted from the steering wheel to the steering drive mechanism, and change the direction of transmission of the force or torque. When the driver performs a steering operation on the motor vehicle by means of the steering wheel, it can provide steering assistance, reducing the force required from the driver to operate the steering wheel, so that driving is more relaxed and convenient for the driver.

Summary of the invention

[0004] An object of one aspect of the present invention is to provide an improved motor vehicle steering gear.

[0005] An object of another aspect of the present invention is to provide a motor vehicle comprising the abovementioned motor vehicle steering gear.

[0006] To achieve the abovementioned objects, one aspect of the present invention provides a motor vehicle steering gear, wherein the motor vehicle steering gear comprises an electric drive unit and a steering gear body, the steering gear body comprising: a hollow housing; an end cap closing an opening end of the housing; a steering screw arranged in the housing, two ends of the steering screw being held at the end cap and the housing respectively; a steering nut, fitted round the steering screw and meshed with the steering screw, and thereby being slidable in the axial direction of the steering screw under the rotational driving action of the steering screw, with axially arranged drive teeth being formed at a peripheral side of the steering nut; an output shaft having a fan-shaped gearwheel part, the drive teeth of the steering nut being meshed with a fan-shaped gearwheel in such a way as to be capable of driving the output shaft, and the fan-shaped gearwheel part driving the output shaft, wherein the end cap and the housing limit a degree of freedom of axial movement of the two ends of the steering screw respectively, and the two ends of the steering screw have a degree of freedom of circumferential rotation and a degree of freedom of radial movement.

[0007] Optionally, in the motor vehicle steering gear as described above, the two ends of the steering screw are mounted to the end cap and the housing respectively by means of thrust bearings.

[0008] Optionally, in the motor vehicle steering gear as described above, the thrust bearing is a needle roller bearing, and a spacer is provided between the needle roller bearing and the end cap and/or the housing.

[0009] Optionally, in the motor vehicle steering gear as described above, the thrust bearing is a thrust ball bearing.

[0010] Optionally, in the motor vehicle steering gear as described above, the steering screw drives the steering nut by means of a ball circulation mechanism. [0011] Optionally, in the motor vehicle steering gear as described above, the steering nut comprises a penetrating axial inner hole, and the ball circulation mechanism comprises: an outer helical groove located at the periphery of the steering screw; an inner helical groove located at an inner circumference of the inner hole of the steering nut, wherein the steering screw passes through the inner hole of the steering nut, and the outer helical groove and the inner helical groove form a raceway; and balls arranged in the raceway.

[0012] Optionally, in the motor vehicle steering gear as described above, a side surface of an inner cavity of the housing provides a slide track for the steering nut, and inner cavity parts at two ends of the steering nut are in fluid communication with each other.

[0013] Optionally, in the motor vehicle steering gear as described above, the electric drive unit has an output shaft for driving the steering screw to rotate. [0014] Optionally, in the motor vehicle steering gear as described above, the two ends of the steering screw are held in a recess at the end cap or the housing respectively, the inner diameter of each recess being larger than the outer diameter of the steering screw at the corresponding end.

[0015] To achieve the abovementioned objects, another aspect of the present invention provides a motor vehicle, wherein the motor vehicle comprises any one of the motor vehicle steering gears described in the previous aspect.

Brief description of the drawings

[0016] The disclosed content of the present invention will become more obvious with reference to the drawings. It should be understood that these drawings merely serve an illustrative purpose, and are not intended to limit the scope of protection of the present invention. In the drawings:

Fig. 1 is a schematic sectional view of a steering gear body in a motor vehicle steering gear according to an embodiment of the present invention; and Fig. 2 is a partial exploded drawing of the steering screw of the steering gear body in Fig. 1.

Detailed description of embodiments

[0017] Particular embodiments of the present invention are described in detail below with reference to the drawings. In the drawings, identical reference labels indicate identical or corresponding technical features. In addition, for simplicity and clarity, in cases where the quantity of a technical feature is more than one, it might only be labelled at one position or a number of positions in the same drawing. [0018] It will be understood that although a description is given herein with reference to a limited number of embodiments, those skilled in the art could expand, alter, replace and/or combine technical features on this basis. Thus, the content herein is descriptive and should not be regarded as limiting the scope of the present invention.

[0019] Fig. 1 is a schematic sectional view of a steering gear body in a motor vehicle steering gear according to an embodiment of the present invention.

[0020] As shown in Fig. 1, the steering gear body 100 may comprise a housing, an end cap, a steering screw, a steering nut, balls and an output shaft, etc. When the steering gear operates, an output shaft of an electric drive unit drives the steering screw to rotate, and the steering screw pushes the steering nut to move axially by means of the balls; in turn, drive teeth on the steering nut are meshed with a fan-shaped gearwheel in such a way as to drive the output shaft, the fan- shaped gearwheel part drives the output shaft, and the vehicle wheels are in turn driven to swing by means of a rod system, thereby steering the motor vehicle. [0021] The electric drive unit of the motor vehicle steering gear is not shown in the figures. In a particular embodiment, the electric drive unit may be disposed at an end of a steering gear body 100, e.g. the right end in Fig. 1, such that the output shaft of the electric drive unit engages with and can drive the steering screw, to provide steering assistance.

[0022] The steering gear body 100 of the motor vehicle steering gear is described in greater detail below with reference to the drawings.

[0023] As shown in the figures, in the embodiment shown, the steering gear body 100 may comprise a housing 111 and an end cap 112. The housing 111 is hollow, and has an opening at one end thereof, e.g. at the left end of the housing 111 as shown in Fig. 1. The end cap 112 is fitted to the opening of the housing 111, and closes a hollow part of the housing 111 at the opening, thereby defining a hollow inner cavity 113 in the housing. As shown in the figure, the end cap 112 may be mounted to the housing 111 by means of a number of bolts 114. Depending on specific needs, the bolts 114 may be designed as anti-loosening bolts.

[0024] In other embodiments, this mounting may also be performed by another suitable common method. In order to achieve better sealing, a gasket may be provided at mating faces of the housing 111 and the end cap 112.

[0025] The housing 111 has a bottom wall 115 opposite the opening thereof, e.g. at the right end of the housing 111 as shown in Fig. 1. At the bottom wall 115, the housing 111 has a penetrating opening 116 to allow the output shaft (not shown) of the electric drive unit to extend in, so as to drive the steering screw 120. A recess 117 is formed, coaxially with the opening 116, on a side of the end cap 112 that faces the housing inner cavity 113; the two are arranged coaxially, to facilitate the installation and efficient operation of the steering screw 120.

[0026] The steering screw 120 is located in the housing of the steering gear body, with two ends of the steering screw being held at the end cap and the housing, respectively. As stated above with reference to Fig. 1, one end of the steering screw 120 may be fitted in the recess 117 of the end cap 112, and the other end may be fitted in the opening 116 of the bottom wall 115 of the housing 111. To facilitate the mounting of the corresponding end of the steering screw 120, a step 118 may be provided in an expanded fashion at the periphery of the opening 116, on a side of the bottom wall 115 that faces the housing inner cavity 113, and said end of the steering screw 120 is mounted at the step 118. At the recess 117 and the step 118, their respective inner diameters may be larger than the outer diameters of the corresponding ends of the steering screw 120, as shown in Fig. 1, so that the corresponding ends of the steering screw 120 will not be gripped tightly. In the embodiment shown, the diameter of each end of the steering screw 120 is the same as the diameter of a body part of the steering screw 120. In another embodiment, a design is also possible whereby a chamfer is formed at each end of the steering screw 120, such that the diameter of the steering screw gradually decreases towards each end, in order to prevent it from interfering with/being gripped tightly by the recess 117 and the step 118 in a radial direction.

[0027] In the embodiment shown, thrust bearings 131, 132 are provided between each end of the steering screw 120 and the bottom wall 115 and end cap 112 of the housing 111 respectively. It will be understood that when the steering screw 120 is mounted in this manner, the housing and the end cap limit the degree of freedom of axial movement of the two ends of the steering screw 120, while retaining the degree of freedom of circumferential rotation and the degree of freedom of radial movement possessed by each of the two ends of the steering screw. Thus, the two ends of the steering screw 120 can rotate in the circumferential direction, and can also both move slightly in upward/downward and forward/rearward directions. Here, the upward, downward, forward and rearward directions are all directions perpendicular to the axial direction of the steering screw 120.

[0028] In the example shown, the thrust bearings 131, 132 are both needle roller bearings, and spacers 141, 142 are provided between each of the bearings and the bottom wall 115 and end cap 112 respectively. For the specific structure of the needle roller bearings and the spacers, see the schematic exploded drawing in Fig. 2.

[0029] Fig. 2 is a partial exploded drawing of the steering screw of the steering gear body in Fig. 1. The figure shows the steering screw 120 to be axially mounted, the thrust bearings 131, 132 in the form of needle roller bearings, and the spacers 141, 142. The spacers 141, 142 are shown as having the shape of round rings in the figure. In particular applications, they may also be round-plate spacers, or the shapes thereof may be adapted to match inner peripheral shapes of the recess 117 and the step 118 respectively. In contrast to the rough-surfaced housing of low hardness manufactured by a process such as casting, the spacers 141, 142 can provide a flat supporting face of high hardness for the steering screw 120.

[0030] In an optional embodiment, thrust ball bearings may be used instead of needle roller bearings. In this case, the spacers 141, 142 may be omitted. Since the thrust ball bearings themselves provide washer-like sleeve rings, the spacers 141, 142 need not be additionally provided.

[0031] It can also be seen from Figs. 1 and 2 that an outer helical groove 121 is formed on a peripheral face of the steering screw 120. Specifically, in this example, the outer helical groove 121 may only be arranged on a peripheral face of a middle section of the steering screw 120. In an optional embodiment, the outer helical groove may be arranged on a partial peripheral face or the entire peripheral face of the steering screw 120 as required. The outer helical groove 121 is adapted to drive the output shaft of the steering gear body. For example, the manner of driving thereof may be direct or indirect. In the embodiment shown, the outer helical groove 121 converts circumferential rotation of the steering screw 120 to axial movement of the steering nut 150, thereby driving the steering nut to move left or right, and then driving the steering gear output shaft indirectly via the steering nut. In an optional embodiment, it is possible to drive the fan-shaped gearwheel of the output shaft of the steering gear directly by means of the outer helical groove of the steering screw.

[0032] The steering nut 150 of the steering gear body 100 is fitted round the steering screw 120 and meshed with the steering screw 120, thereby being able to slide in the axial direction of the steering screw 120 under the rotational driving action of the steering screw 120. In one embodiment, as shown in the figure, a slide track for the steering nut may be provided by a side surface of the inner cavity of the housing of the steering gear body 100, and parts of the inner cavity at two ends of the steering nut may be in fluid communication with each other.

[0033] It can be seen from the figure that the steering nut 150 comprises a penetrating axial inner hole, and an inner circumference of the axial inner hole has an inner helical groove 151. The steering screw 120 passes through the inner hole, and a raceway is formed between the outer helical groove 121 of the steering screw 120 and the inner helical groove 151 of the inner hole of the steering nut 150, the raceway being provided with multiple balls 160. The outer helical groove, inner helical groove and balls, etc. form a ball circulation mechanism, the function thereof being to convert circumferential movement of the steering screw 120 to linear movement of the steering nut 150. When the steering screw 120 rotates, the steering nut 150 is pushed by means of the balls 160; the steering nut 150 is pushed and moves left or right in the axial direction of the steering screw 120. The balls 160 roll in the raceway formed by the outer helical groove 121 and inner helical groove 151, with low friction. [0034] In addition, as shown in the figure, teeth 152 arranged in the axial direction are formed on the periphery of the steering nut 150, the teeth 152 being adapted to engage with the fan-shaped gearwheel 170 of the output shaft of the steering gear and drive the output shaft by means of the fan-shaped gearwheel. The steering screw of the steering gear body is arranged at an angle to the output shaft of the steering gear body. In the embodiment shown, the housing of the steering gear body is formed with a space for accommodating the fan-shaped gearwheel 170; this space is in communication with the inner cavity 113 of the housing, such that the fan-shaped gearwheel 170 can engage with the teeth 152 on the periphery of the steering nut at one side of the steering nut 150. When the steering screw is driven to reciprocate left and right, the fan-shaped gearwheel swings to and fro towards the left and right, thereby driving the output shaft to rotate to and fro. [0035] The fan-shaped gearwheel 170 may be integrally formed on the output shaft. The output shaft can drive the wheels of the motor vehicle to swing by means of the rod system, thus steering the motor vehicle. It will be understood that the force outputted to the steering gear comes from the steering wheel moved by the driver; the steering wheel transmits torque to the steering gear, in which the torque is amplified to a larger torque by electric drive to drive the swinging/steering of the vehicle wheels.

[0036] The rolling friction exerted by the balls 160 on the steering nut 150 is negligible; moreover, the fan-shaped gearwheel 170 and the teeth 152 on the steering nut 150 have a certain thickness. Therefore, the existence of the meshing relationship between the teeth 152 and the fan-shaped gearwheel 170 enables the steering nut 150 to move axially on the steering screw 120 but prevents the steering nut from rotating circumferentially.

[0037] It can be seen from the above description with reference to Figs. 1 and 2 that the degree of freedom of axial movement of the steering screw 120 is defined in the steering gear body 100, and the two ends of the steering screw have a degree of freedom of circumferential rotation and a degree of freedom of radial movement.

[0038] In contrast, in the steering gear body of some motor vehicle steering gears, the manner in which the steering screw thereof is supported inside the steering gear between the housing and the end cap generally comprises: (1) being fixed at both ends, only providing a degree of freedom of circumferential rotation, i.e. the steering screw can rotate, but cannot move upward, downward, forward or rearward; or (2) being fixed at one end, the other end being configured as a free end, and at the fixed end, only circumferential rotation is possible, but all other degrees of freedom are restricted. In these motor vehicle steering gears (because at least one end is excessively restricted in terms of degrees of freedom) it is necessary to precisely process a mounting hole for mounting the steering screw on the housing, to provide a high degree of coaxiality, so the manufacturing cost is increased. In addition, a component force, in a direction perpendicular to the steering screw, of the force arising when the teeth 152 of the steering nut 150 mesh with teeth of the fan-shaped gearwheel 170 will cause the steering screw 120 to bend, possibly causing the balls to stick in the outer/inner helical grooves 121, 151. Furthermore, the outer helical groove 121 on the steering screw 120 might fracture under the action of the bending load, resulting in operational failure of the steering gear.

[0039] In the embodiment shown, the two thrust bearings 131, 132 are used to bear axial forces, and only serve a supporting function. When assembly is performed, the bearing 131 at the left and the bearing 132 at the right may have a minute amount of deformation with the left and right ends of the steering screw 120. After the bearings 131, 132 have been fitted, the steering screw and steering nut, etc. may be regarded as a single piece, which will experience upward movement when subjected to a component force directed vertically upward due to the steering nut 150 engaging with the teeth of the fan-shaped gearwheel 170. For example, if the steering nut 150 moves to the left side or right side, it will tilt to the left or right; this is because, for example, if the steering nut 150 moves to its leftmost position, the force will be applied to the right side of the steering nut 150, because the meshing thereof is via the tooth located farthest to the right. As can be seen, the steering screw mounted in this fashion limits left/right axial play of the steering screw, and will therefore at least have a certain degree of freedom in all directions other than the direction of axial movement, rather than being in a locked state. Thus, when the steering screw 120 and steering nut 150, etc. are regarded as a single piece, this single piece is not locked.

[0040] However, in the case where at least one end of the steering screw is fixed or both ends thereof are fixed, e.g. fixed directly in a hole of the housing or fixed by means of a deep groove ball bearing or angular contact bearing, bending of the steering screw is likely to cause the balls to stick between the steering screw and steering nut, because the left side and/or right side of the steering screw is gripped tightly and cannot move up/down or forward/rearward when subjected to a vertical force.

[0041] As can be seen, in the solution according to the present invention in which the degree of freedom of axial movement of the steering screw is limited, at least one of the following beneficial technical effects can also be achieved: (1) in these motor vehicle steering gears, a high degree of coaxiality can be achieved while there is no longer any need to precisely process a mounting hole in the housing, thus helping to reduce manufacturing costs; (2) when the teeth 152 of the steering nut 150 mesh with the teeth of the fan-shaped gearwheel 170, thus giving rise to a component force in a direction perpendicular to the steering screw, an end of the steering screw can shift appropriately to avoid bending of the steering screw 120, thus preventing the balls from sticking in the raceway; (3) because bending of the steering screw 120 is avoided, possible fracturing of the outer helical groove 121 on the steering screw 120 due to the action of a bending load thereon is also avoided, so the steering gear can be kept in an effective operating state.

[0042] To summarize the description above, the degree of freedom of axial movement of the steering screw of the motor vehicle steering gear in at least one aspect of the present invention is limited, and the specific manner in which this is achieved includes but is not limited to providing thrust bearings and/or spacers at the two ends of the steering screw, which helps to increase the reliability of the entire mechanism.

[0043 ]At least one other aspect of the present invention provides a motor vehicle, which may comprise the motor vehicle steering gear according to any embodiment in the aspect described above. The motor vehicle steering gear can receive and amplify a torque from a steering wheel, and drive vehicle wheels to swing via a rod system. In an optional embodiment, the vehicle wheels to be steered may comprise front wheels and/or rear wheels of the motor vehicle. It will be understood that the corresponding motor vehicle will at least possess the advantages corresponding to the corresponding motor vehicle steering gear in each embodiment described above.

[0044] As stated above, the motor vehicle steering gear according to a number of embodiments of the present invention and the motor vehicle comprising the motor vehicle steering gear according to a number of embodiments of the present invention have been described herein. It should be understood that the scope claimed by the present invention is not limited to the content described above. Those skilled in the art could subject the embodiments above to various expansions, alterations, substitutions and/or combinations without departing from the technical concept of the present invention, and all such expansions, alterations, substitutions and/or combinations should be included in the scope claimed by the present invention.