STEERING SHAFT CONNECTING STRUCTURE OF ELECTRIC POWER STEERING

Abstract

According to the present disclosure, there is provided a structure of an electric power steering device in which its steering shafts are connected includes a torsion bar connected to a steering wheel; an input shaft surrounding the torsion bar on an input side of the torsion bar;

and an output shaft surrounding one end of the input shaft and the torsion bar on an output side of the torsion bar, wherein the one end of the input shaft is inserted into and coupled to one end of the output shaft, and a copper bush and a needle bearing are disposed side by side between an outer circumferential surface of the one end of the input shaft and an inner circumferential surface of the one end of the output shaft.

Claims

1. A steering shaft connecting structure of an electric power steering device, comprising: a torsion bar connected to a steering wheel; an input shaft surrounding the torsion bar on an input side of the torsion bar; and an output shaft surrounding one end of the input shaft and the torsion bar on an output side of the torsion bar, wherein the one end of the input shaft is inserted into and coupled to one end of the output shaft, and a copper bush and a needle bearing are disposed side by side between an outer circumferential surface of the one end of the input shaft and an inner circumferential surface of the one end of the output shaft.

2. The steering shaft connecting structure of claim 1, wherein the other end of the input shaft is externally supported by a column lower bearing.

3. The steering shaft connecting structure of claim 2, wherein the output shaft is externally supported by a gearbox housing bearing.

4. The steering shaft connecting structure of claim 1, wherein, when a low weight is applied at room temperature, only the needle bearing supports the weight.

5. The steering shaft connecting structure of claim 4, wherein, when a high weight is applied at room temperature, the copper bush comes into contact with the outside of the input shaft so that both the needle bearing and the copper bush support the weight.

6. The steering shaft connecting structure of claim 1, wherein the rotational frictional force increases as the copper bush thermally contracts at a low temperature.

7. A steering shaft connecting structure of an electric power steering device, comprising: a torsion bar connected to a steering wheel; an input shaft surrounding the torsion bar on an input side of the torsion bar; and an output shaft surrounding one end of the input shaft and the torsion bar on an output side of the torsion bar, wherein the one end of the input shaft is inserted into and coupled to one end of the output shaft, and a needle bearing and a copper bush surrounding the needle bearing are disposed between an outer circumferential surface of the one end of the input shaft and an inner circumferential surface of the one end of the output shaft.

8. The steering shaft connecting structure of claim 7, wherein the other end of the input shaft is externally supported by a column lower bearing.

9. The steering shaft connecting structure of claim 8, wherein the output shaft is externally supported by a gearbox housing bearing.

10. The steering shaft connecting structure of claim 7, wherein, when a low weight is applied at room temperature, only the needle bearing supports the weight.

11. The steering shaft connecting structure of claim 10, wherein, when a high weight is applied at room temperature, the copper bush comes into contact with the outside of the needle bearing so that both the needle bearing and the copper bush support the weight.

12. The steering shaft connecting structure of claim 7, wherein the rotational frictional force increases as the copper bush thermally contracts at a low temperature.

13. The steering shaft connecting structure of any one of claim 7, wherein two needle bearings are disposed side by side.

14. The structure of claim 13, wherein the copper bush surrounds both the two needle bearings.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a view showing an example of the conventional internal shaft connecting structure of the EPS device.

[0032] FIG. 2 is a view showing another example of the conventional internal shaft connecting structure of the EPS device.

[0033] FIG. 3 is a view showing a modeling of an internal shaft connecting structure of the EPS device where an input shaft and an output shaft are connected by a needle bearing.

[0034] FIG. 4 is a view showing a modeling of an internal shaft connecting structure of the EPS device where the input shaft and the output shaft are connected by a copper bush.

[0035] FIG. 5 is a view showing an internal shaft connecting structure of the EPS device according to an embodiment of the present disclosure.

[0036] FIG. 6 is a view showing an internal shaft connecting structure of the EPS device according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

[0037] When needle bearings are applied to an internal shaft connecting structure of an electric power steering (EPS) device, excessive popping noise may be generated when steering is reversed at low temperatures. In the present disclosure, an enhanced internal shaft connecting structure of the EPS device is suggested by analyzing a mechanism in which such noise is generated.

[0038] FIG. 3 shows a simplified modeling of an internal shaft connecting structure of the EPS device where an input shaft and an output shaft are connected by a needle bearing, and FIG. 4 shows a simplified modeling of an internal shaft connecting structure of the EPS device where the input shaft and the output shaft are connected by a copper bush.

[0039] When a worm wheel 200 contracts at a low temperature, a gap may appear in a reducer. As a unit rotational torque is lowered, the gap in the reducer may widen.

[0040] When the needle bearing 52 is applied at a low temperature (FIG. 3), the change in the rotational frictional force may be insignificant, and, when the copper bush 51 is applied (FIG. 4), the frictional force may greatly increase due to the shrinkage of the inner diameter of the copper bush.

[0041] When the needle bearing 52 is applied as shown in FIG. 3, a gap in a reducer may widen at low temperatures so that the worm wheel 200 on the output side may easily vibrate, resulting in popping noise and rattling noise during steering reversal. In this case, the bushing frictional force at room temperature and low temperature may be the same.

[0042] When the copper bush 51 is applied as shown in FIG. 4, no noise may be generated at low temperatures because the frictional force of the copper bush 51 may increase. When the frictional force of the bushing increases at low temperatures, a steering wheel 100 may hold the worm wheel 200 so that the mass of the shaft of the worm wheel may increase. That is, with the same gap in a reducer, when the frictional force of the bushing increases at a low temperature, the inertia of the steering wheel may affect the shaft of the worm wheel so that the mass of the shaft of the worm wheel may increase.

[0043] In the present disclosure, there may be proposed a shaft connecting structure, which is to prevent noise at low temperatures when the needle bearing is applied to an internal shaft connecting structure of the EPS device.

[0044] Hereinafter, with reference to FIGS. 5 and 6, an internal shaft connecting structure of the EPS device having an improved function of preventing noise at low temperatures according to the present disclosure will be described in detail. FIG. 5 shows an internal shaft connecting structure of the EPS device according to an embodiment of the present disclosure, and FIG. 6 shows an internal shaft connecting structure of the EPS device according to another embodiment of the present disclosure.

[0045] FIG. 5 shows an internal shaft connecting structure of the EPS device in which an input shaft 120 and an output shaft 130 are coupled by a copper bush 151 and a needle bearing 152 arranged side by side.

[0046] A torsion bar 110 connected to a steering wheel (not shown) may be surrounded by the input shaft 120 on the input side, and may be surrounded by the output shaft 130 together with one end (on the left in FIG. 5) of the input shaft 120 on the output side. The one end of the input shaft 120 may be inserted into and coupled to one end of the output shaft 130 (a right side of the output shaft in FIG. 5), and, between an outer circumferential surface of the one end of the input shaft 120 and an inner circumferential surface of the one end of the output shaft 130, the copper bush 151 and the needle bearing 152 may be arranged side by side.

[0047] The assembly of the input shaft 120 and the output shaft 130 may be externally supported by a column lower bearing 141 at the other end of the input shaft 120 (on the right in FIG. 5), and may be externally supported by a gearbox housing bearing 142 at the output shaft 130. Between the outer circumferential surface of the input shaft 120 and the inner circumferential surface of the output shaft 130, there may be the copper bush 151 and the needle bearing 152 inserted side by side.

[0048] When a low weight is applied at room temperature, only the needle bearing 152 may serve to support the weight, and the rotational frictional force may be low. When a high weight is applied at room temperature, the copper bush 151 may come into contact with the outside of the input shaft 120 so that both the needle bearing 152 and the copper bush 151 may serve to support the weight.

[0049] On the other hand, since the copper bush 151 may thermally contract at a low temperature so that the rotational frictional force may increase, it may be possible to prevent noise and vibration that may occur at a low temperature.

[0050] That is, in the internal shaft connecting structure of the EPS device according to the embodiment in FIG. 5, the input shaft 120 and the output shaft 130 may be coupled by the copper bush 151 and the needle bearing 152; when a high weight is applied at room temperature, both the needle bearing 152 and the copper bush 151 may support the weight so that it may be possible to sufficiently support the weight; and it may possible to prevent noise and vibration by thermal contraction of the copper bush 151 at low temperatures.

[0051] FIG. 6 shows an internal shaft connecting structure of the EPS device in which the input shaft 120 and the output shaft 130 may be coupled by a needle bearing 162 and a copper bush 161 surrounding the needle bearing 162.

[0052] The needle bearing 162 and the copper bush 161 surrounding the needle bearing 162 may be press-fitted between the outer circumferential surface of the input shaft 120 and the inner circumferential surface of the output shaft 130. Here, one needle bearing 162 may be disposed, or two may be disposed side by side. FIG. 6 shows an embodiment in which two needle bearings 162 are disposed side by side. When two needle bearings 162 are disposed side by side, it may be desirable to from the copper bush 161 surrounding them to a size sufficient to surround both of the two needle bearings 162.

[0053] The assembly of the input shaft 120 and the output shaft 130 may be externally supported by the column lower bearing 141 at one end of the input shaft 120, and may be externally supported by the gearbox housing bearing 142 at the end of the output shaft 130.

[0054] When a low weight is applied at room temperature, only the needle bearing 162 may serve to support the weight, and the rotational frictional force may be low. When a high weight is applied at room temperature, the copper bush 161 may come into contact with the outside of the needle bearing 162 so that both the needle bearing 162 and the copper bush 161 may serve to support the weight.

[0055] Meanwhile, since the copper bush 161 may thermally contract at a low temperature so that the rotational frictional force may increase, it may be possible to prevent noise and vibration that may occur at a low temperature.

[0056] That is, in the internal shaft connecting structure of the EPS device according to the embodiment in FIG. 6, the input shaft 120 and the output shaft 130 may be coupled by the needle bearing 162 and the copper bush 161 surrounding the needle bearing 162; when a high weight is applied at room temperature, both the needle bearing 162 and the copper bush 161 may support the weight so that it may be possible to sufficiently support the weight; and it may possible to prevent noise and vibration by thermal contraction of the copper bush 161 at low temperatures.

[0057] In terms of product cost reduction, the embodiment of FIG. 5 may be more desirable than the embodiment in FIG. 6 because the unit price of the copper bush is lower than that of the needle bearing.

[0058] The description above is only an exemplary description of the technology of the present disclosure, and various modifications, changes, and substitutions within the scope of the essential characteristics of the present disclosure will be possible to a person having ordinary skill in the technical field to which the present disclosure belongs. Therefore, the embodiments described above are not intended to limit the technology of the present disclosure, but to explain, and the scope of the technology of the present disclosure is not limited by the embodiments. The scope of the present disclosure should be determined based on the following claims, and all technologies within the scope equivalent thereto should be deemed to be included in the scope of the present disclosure.