Suspension system for a vehicle

Abstract: A suspension system for a vehicle includes an axle shaft (8) for rotatably supporting a wheel (2); a strut assembly (28) for vertically supporting the axle shaft (8) on a vehicle body (10); and a cam assembly (13) for coupling a vehicle body side end of the axle shaft (8) to the vehicle body (10) such that the vehicle body side end contacts the vehicle body with a contacting curvature (12) identical to an instantaneous center line of the wheel. The cam assembly (13) includes a cam (14) disposed between the vehicle body and the vehicle body side end of the axle shaft, the cam having a cam-surface (12) curved toward the wheel, a curvature of cam surface being identical to the instantaneous center line of the wheel, and wherein the vehicle body side end of the axle shaft is designed to tightly contact the cam surface.

Description: The present invention relates to a suspension system according to the preamble of claim 1. Generally, a suspension system for a vehicle connects an axle to a vehicle body, and absorbs vibrations and impacts from a road surface while the vehicle is being driven to enhance safety and ride comfort. To absorb impacts, the suspension system is connected flexibly in a vertical direction, and to withstand driving, braking and centrifugal forces transmitted from wheels. The suspension system is connected firmly in a horizontal direction. The conventional suspension system is comprised of a plurality of links and joints, making an assembly process complicated and increasing manufacturing costs. US-A-2 094 824 discloses a suspension system comprising an axle shaft for rotatably supporting a wheel, and a cam assembly for coupling a vehicle body to a vehicle body side end of the axle shaft, wherein the wheel is constrained to move substantially in a straight-line path. CA-A-2 194 251 describes a suspension system comprising an axle shaft for rotatably supporting a wheel, wherein a vehicle body is pivotably coupled to a vehicle body side end of the axle shaft by bearings. Therefore, there is a need for a suspension system which is designed having a small number of parts to reduce manufacturing costs, while providing improved performance. According to the invention, this is achieved by the features in the characterizing part of claim 1. Advantageous further embodiments are described in the subclaims. The present invention provides a suspension system for a vehicle, comprising an axle shaft for rotatably supporting a wheel; a strut assembly for vertically supporting the axle shaft on a vehicle body; and a cam assembly for coupling a vehicle body side end of the axle shaft to the vehicle body such that the vehicle body side end contacts the vehicle body with a contacting curvature identical to an instantaneous center line of the wheel. The cam assembly comprises a cam disposed between the vehicle body and the vehicle body side end of the axle shaft, the cam having a cam-surface curved toward the wheel, a curvature of cam surface being identical to the instantaneous center line of the wheel, and wherein the vehicle body side end of the axle shaft is designed to tightly contact the cam surface. The cam assembly further comprisesa cam contacting member disposed between the cam and the vehicle body, the cam contacting member having a cam contacting surface, a curvature of which is larger than that of the cam surface. An insulating member is disposed between the cam contacting member and the vehicle body, and the axle shaft may be biased toward the vehicle body by a tension spring. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention; Fig. 1 is a schematic diagram of a suspension system according to a first embodiment of the present invention; Figs. 2 and 3 are schematic views illustrating the operation of the suspension system depicted in Fig. 1; Fig. 4 is an exploded perspective view of a cam assembly depicted in Fig. 1; Fig. 5 is a partial sectional view of a cam assembly depicted in Fig. 1; Fig. 6 is a schematic diagram of a suspension system according to a second embodiment of the present invention; Fig. 7 is an exploded perspective view of a cam assembly depicted in Fig. 6; Fig. 8 is an sectional view taken along line I-I of Fig. 7; and Fig. 9 is a schematic view illustrating the operation of a suspension system depicted in Fig. 6. A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Fig. 1 shows a suspension system according to a first embodiment of the present invention. A suspension system comprises an axle shaft 8 for supporting a wheel 2, and a cam assembly 13 disposed between the axle shaft 8 and a vehicle body 10. The cam assembly 13 comprises a cam 14 having a cam-surface, a curvature of which is identical to a trace drawn along instantaneous centers of the wheel 2 when the wheel 2 bumps and rebounds. Describing more in detail, an inner end of the axle shaft 8 is rounded such that that it complementary surface-contacts the cam surface of the cam 14. The inner end of the axle shaft 8 is connected to the vehicle body 10 by a tension spring 18. The vehicle body 10 is provided at a portion contacting the cam 14 with an arc-shaped contacting member 20. An insulating member 22 is provided between the vehicle body 10 and the contacting member 20. Since the axle shaft 8 is connected to the vehicle body 10 by the tension spring 18, the axle shaft 8 can actively operate with respect to the movement of the cam 14 while being biased by the tension spring 18. The insulating member 22 prevents impact from directly transmitting to the vehicle body 10 through the cam 14. In addition, a strut assembly 28 having a shock absorber 26 and a spring 24 is vertically disposed between the axle shaft 8 and the vehicle body 10. The strut assembly 28 absorbs impact which is vertically transmitted to the vehicle body 10 from the wheel 2. The operation of the above-described suspension system will be described hereinafter with reference to Figs. 2 and 3 When the wheel 2 bounds, as shown in Fig. 2, the axle shaft 8 rotates counterclockwise in the drawing as the wheel ascends as shown by the broken line. At this point, the axle shaft 8 is biased toward the vehicle body 10 by the tension spring 18, thereby receiving a load in a longitudinal direction thereof. As a result, the cam 14 rotates clockwise as shown by the broken line. At this point, due to the curvature of the cam surface 12, the cam 14 is declined downward. The declination of the cam 14 allows the axle shaft 8 surface-contacting the cam surface 12 to move inner-downward. That is, the axle shaft 8 does not move along the trace of the instantaneous center of the wheel 2 but along the cam surface 12 of the cam 14 by the clockwise rotation the cam 14. When the wheel 2 rebounds, as shown in Fig. 3, the axle shaft 8 rotates clockwise as shown by broken line. At this point, the axle shaft 8 is biased toward the vehicle body 10 by the tension spring 18, thereby receiving a load in a longitudinal direction thereof. As a result, the cam 14 rotates counterclockwise as shown by the broken line. At this point, due to the curvature of the cam surface 12, the cam 14 is declined upward. The declination of the cam 14 allows the axle shaft 8 surface-contacting the cam surface 12 to move inner-upward. That is, the axle shaft 8 does not move along the trace of the instantaneous center of the wheel 2 but along the cam surface 12 of the cam 14 by the counterclockwise rotation the cam 14. In the above described suspension system, since a plurality of links and joints are not used, manufacturing costs are kept as a minimum. In addition, by properly adjusting the curvature of the cam 14, the instantaneous center of the wheel 2 can be accurately adjusted. Figs. 4 and 5 show detailed views of the cam assembly 13 depicted in Fig. 1. The cam assembly 13 comprises a bracket 34 for mounting on the vehicle body 10. The insulating member 22 and the cam-contacting member 20 are inserted inside the bracket 34. Upper and lower ends of the insulating member 22 are fixed on the bracket 34 by bolts 40 and nuts 42. The cam 14 is disposed contacting the cam contacting member 20. The cam 14 is provided with a cam guide slot 44 having a curvature in a direction opposite to that of the cam surface 12. The cam 14 is fixed on the bracket 34 by a guide pin 46 penetrating the cam guide slot 44 and holes formed in side plates 36 and 38 of the bracket 34. The cam guide slot 44 allows the cam 14 to smoothly rotate when the wheel ascends and descends. Axle shaft guide slots 48 having a curvature similar in direction and overall shapeinversely identical to the guide slot 44 are formed in the side plates 36 and 38 of the bracket 34. Assembled through the guide slots 48 and an inner end center hole 16 of the axle shaft 8 is a guide pin 50 to which one end of the tension spring 18 is fixed. Fig. 6 shows a suspension system according to a second embodiment of the present invention. A suspension system according to this embodiment comprises an axle shaft 80 for supporting a wheel 2, and a cam assembly 130 disposed between the axle shaft 80 and a vehicle body 100. The cam assembly 130 comprises a cam 120 integrally formed on an inner end of the axle shaft 80 and having a cam-surface 140, a curvature of which is identical to a trace drawn along instantaneous centers of the wheel 20 when the wheel 20 bumps and rebounds, a cam contacting member 200 contacting the cam 120, and an insulating member 240 disposed between the cam contacting member 200 and the vehicle body 100. The cam-contacting member 200 has a curvature larger than that of the cam surface 140 of the cam 120. The cam 120 is biased toward the vehicle body by tension springs 180. That is, the tension springs 180 connects the vehicle body 100 to a spring fixing member 220 formed on the cam 120 such that the axle shaft 8 is biased toward the vehicle body 100 in a direction of its longitudinal axis. The cam 20 is curved toward the wheel 20 so that it is provided with a hook portion 260. The vehicle body 100 is extended toward the wheel 20 at its lower portion below the cam contacting member 200, then curved toward the vehicle body 100 to form a hook portion 280. The hook portion 260 of the cam 260 is hooked to the hook portion 280 of the vehicle body 100 in such a manner that the hook portions 260 and 280 do not interfere with each other when the wheel 20 ascends and descends. Figs. 7 and 8 show detailed views of the cam assembly 130 depicted in Fig. 6. The insulating member 240 is embedded into the vehicle body 100, and the cam contacting member 200 is also embedded into the vehicle body 100 in a state contacting the insulating member 240. The cam contacting member 200 is provided with a vertical groove 300 in which the cam 120 is fitted so that the cam 120 does not move in a longitudinal direction of the vehicle body 100. The insulating member 240 prevents impact force from directly transmitting to the vehicle body 100 when wheel 20 ascends and descends. Referring again to Fig. 6, the axle shaft 80 is vertically supported on the vehicle body 100 by a strut assembly 360 having a spring 320 and a shock absorber 340 to absorb impact force which is vertically transmitted to the vehicle body 100 from the wheel 20. The operation of the above described suspension system will be described hereinafter with reference to Fig. 9. When the wheel 20 bounds, the axle shaft 80 rotates counterclockwise as shown in Fig. 9. At this point, a contact point between the cam 120 and the cam contact member 200 moves upward. That is, since the curvature of the cam surface 140 is formed to be identical to the line drawn along instantaneous centers of the wheel 20, the substantial instantaneous centers of the wheel 20 varies along the curvature of the cam contacting member 20. While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims: A suspension system for a vehicle, comprising: an axle shaft (8; 80) for rotatably supporting a wheel (2) ; a strut assembly (28; 360) for supporting the axle shaft (8; 80) on a vehicle body (10; 100); a cam assembly (13; 130) for coupling a vehicle body side end of the axle shaft (8; 80) to the vehicle body (10; 100) such that the vehicle body side end of the axle shaft (8; 80) contacts the vehicle body (10; 100); the cam assembly (13; 130) comprising a cam (14; 120) disposed between the vehicle body (10; 100) and the vehicle body side end of the axle shaft (8; 80), the cam (14; 120) having a cam surface (12; 140) with a curvature curving towards the wheel (2); and a cam contacting member (20; 200) disposed between the cam (14; 120) and the vehicle body (10; 100), the cam contacting member (20; 200) having a cam contacting surface tightly contacting the cam surface (12; 140) of the cam (14; 120), characterized in that the cam contacting member (20; 200) has a curvature curving towards the wheel (2), the curvature being larger than that of the cam surface (12; 140) of the cam (14; 120), said cam contacting member (20; 200) is supported by an insulating member (22; 240) disposed between the cam contacting member (20; 200) and the vehicle body (10; 100) for preventing direct transmission of an impact force to the vehicle body (10; 100) through the cam (14; 120). The suspension system of claim 1, further comprising a bracket (34) coupled to the vehicle body (10) and having two opposite side plates (36, 38), wherein the cam contacting member (20) is mounted between the side plates (36, 38). The suspension system of claim 2, further comprising: a first guide slot (44) formed through the cam (14) and having a curvature curving in a direction opposite the curvature of the cam surface (12) of the cam (14); a first guide pin (46) penetrating the first guide slot (44) and a hole formed in each side plates (36, 38); a second guide slot (48) formed in each side plates (36, 38) and having a curvature curving in a direction opposite the curvature of the cam surface (12) of the cam (14); and a second guide pin (50) penetrating the second guide slots (48) and a hole (16) formed through the axle shaft (8). The suspension system of claim 1, wherein the cam (120) is integrally formed on a vehicle body side end of the axle shaft (80). The suspension system of claim 4, wherein the vehicle body (100) is extended toward the wheel (2), then curved toward the vehicle body (100) to define a hook portion (280), the cam (120) being hooked to the hook portion (280) of the vehicle body (100) in such a manner that the hook portion (280) and the cam (120) do not interfere with each other when the wheel (2) ascends and descends. The suspension system of any of claims 1-5, wherein the axle shaft (8; 80) is biased toward the vehicle body (10; 100) by a tension spring (18; 180). The suspension system of claim 6, wherein the tension spring (18; 180) is coupled to the vehicle body (10; 100) and a spring fixing member (50; 220) formed on the vehicle body side end of the axle shaft (8; 80).

Inventors: LEE UN-KOO, LEE, UN-KOO
Applicants: HYUNDAI MOTOR CO LTD, HYUNDAI MOTOR COMPANY
Application year: 1999
Main classification: B60G7
IPC codes: B60G3, B60G7