JP2007015449A - Electric power steering device and connection structure of rotating shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly quiet electric power steering device and a coupling structure of a rotating shaft capable of realizing such quietness. <P>SOLUTION: A coupling member 17 is provided with a ring member 25 with engagement grooves 26 which is intervened between a first shaft and a second shaft and which is inserted with respective engagement protruding portions of the first shaft and the second shaft respectively. The ring member itself is formed out of elastic material. The respective engagement protruding portions 41, 42 are engaged without gaps in the peripheral direction (rotational direction) within the corresponding respective engagement grooves 26. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric power steering device and a connecting structure of a rotating shaft.

  2. Description of the Related Art Conventionally, a rack shaft provided so as to be able to reciprocate according to a steering operation, and a hollow shaft that is arranged coaxially with the rack shaft and rotated by a motor drive, the rotation of the hollow shaft is racked by a ball screw mechanism. A so-called rack assist type electric power steering device (EPS) is known which applies an assist force to a steering system by converting the shaft into a reciprocating motion.

In such rack assist type EPS, a so-called coaxial type having a hollow motor shaft coaxially arranged with the rack shaft (see Patent Document 1), or a motor as a drive source is mounted on the rack shaft (hollow There is a so-called rack cross type in which the axis (motor shaft) is arranged obliquely with respect to the shaft (see, for example, Patent Document 2).
JP 2003-335249 A JP 2002-225734 A

  By the way, in many cases, strengthening measures such as quenching are applied to the rack shaft, and its bending rigidity is extremely high. However, in an actual usage environment, a very large external input may be applied to the steered wheels, such as when a collision with a curb. Therefore, although the rack shaft has high rigidity, when such an excessive stress is applied, it is inevitable that a certain amount of bending occurs in the rack shaft.

  However, in the rack assist type EPS as described above, the rack shaft is connected to a hollow shaft via a ball screw mechanism, and the hollow shaft is pivotally supported by the housing. That is, these members are extremely rigidly connected. Therefore, even if a stress that causes the rack shaft to bend is input, the deflection cannot be allowed, and the stress is transmitted directly to the housing via the hollow shaft. Sound may be generated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering device with high quietness and a connecting structure of a rotating shaft that enables the electric power steering device.

  In order to solve the above problems, the invention according to claim 1 is characterized in that a rack shaft provided so as to be capable of reciprocating in an axial direction, a hollow shaft through which the rack shaft is inserted and rotated by a motor drive, An electric power steering apparatus comprising: a ball screw mechanism that converts rotation of a hollow shaft into reciprocating movement of the rack shaft; and a housing that houses the hollow shaft and the ball screw mechanism, wherein the hollow shaft is attached to the housing. The first shaft is pivotally supported and the second shaft is provided with the ball screw mechanism. The first shaft and one end of the second shaft extend in the axial direction at positions facing each other across the axis. A pair of engaging protrusions are provided, and the first shaft and the second shaft are arranged so that the straight lines connecting the engaging protrusions are orthogonal to each other. In addition, a connecting member having a ring member in which an engaging groove into which each engaging protrusion of the first shaft and the second shaft is inserted is interposed between the first shaft and the second shaft. The ring member is made of an elastic material, and the engagement protrusions of the first shaft and the second shaft are inserted into the corresponding engagement grooves, so that the circumference of the engagement protrusions is inserted into the engagement grooves. The gist is to be engaged in the direction without any gap.

  According to the above configuration, the second shaft can be coupled to the first shaft so as to be rotatable integrally with the first shaft without being pivotally supported by the housing, and to be swingable in the radial direction. It becomes possible to allow the shaft to bend. Therefore, even when a stress that deflects the rack shaft is applied, it is possible to prevent the stress from being directly transmitted to the housing and to prevent the generation of abnormal noise. Further, by eliminating the gaps between the respective engagement grooves and the respective engagement protrusions, i.e., the rotational play, it is possible to prevent the occurrence of a hitting sound resulting therefrom. By forming the ring member itself from an elastic material, it is possible to achieve both appropriate radial displacement between each engagement groove and each engagement protrusion and durability of the elastic member. Therefore, the first shaft and the second shaft can be more preferably pivotably connected without impairing the durability thereof, and the quietness thereof can be further improved.

  According to a second aspect of the present invention, the relative displacement in the circumferential direction between the first shaft and the second shaft is set at a predetermined angle by restricting the circumferential movement of at least one of the engagement protrusions. The gist is to provide a restricting means for limiting within the range.

  According to a third aspect of the present invention, at least one of the engagement protrusions on the first shaft side or the second shaft side is formed such that an axial length thereof is longer than an axial length of the ring member. The first shaft or the second shaft is formed with an engagement recess into which the engagement protrusion is inserted at a position opposite to the elongated engagement protrusion. It is formed by setting the circumferential width of the concave portion to be wider than the circumferential width of the engaging protrusion corresponding to the predetermined angle range.

  According to a fourth aspect of the present invention, the connecting member is provided with a restricting member having an insertion hole formed corresponding to the engaging protrusion of the first shaft and the second shaft, and the restricting means includes: The gist is that the insertion hole is formed by setting at least one circumferential width of the insertion hole wider than the circumferential width of the engagement protrusion corresponding to the predetermined angle range.

  According to each of the above configurations, even when a circumferential relative displacement, that is, a twist, occurs between the first shaft and the second shaft due to the rotational torque, the relative displacement is within a predetermined angle by the regulating means. Limited to Therefore, when an excessive rotational torque is transmitted, it is possible to suppress the relative displacement in the circumferential direction that occurs between the first shaft and the second shaft, and to prevent a rotational transmission delay associated therewith.

The gist of the invention described in claim 5 is that a metal layer is formed on a circumferential wall surface of each engagement groove.
According to the said structure, it can prevent that a ring member wears by friction with each engaging protrusion, Thereby, the durability can be improved more.

  According to a sixth aspect of the present invention, a pair of engaging projections extending in the axial direction are provided at opposite positions of a pair of rotating shafts arranged coaxially at positions facing each other across the axis. Both rotating shafts are arranged so that the straight lines connecting the engaging protrusions are orthogonal to each other, and a ring member having an engaging groove into which the engaging protruding portions of the both rotating shafts are respectively inserted between the rotating shafts. The ring member is made of an elastic material, and the respective engaging protrusions are inserted into the corresponding engaging grooves to thereby form the engaging grooves. And the relative displacement in the circumferential direction between the two rotating shafts is set at a predetermined angle by restricting the circumferential movement of at least one of the engaging protrusions. The provision of a restricting means for limiting within the scope; That.

  According to the said structure, generation | occurrence | production of the contact sound resulting from it can be prevented by eliminating the clearance gap between each engagement groove | channel and each engagement protrusion, ie, rotation backlash. By forming the ring member itself from an elastic material, it is possible to achieve both appropriate radial displacement between each engagement groove and each engagement protrusion and durability of the elastic member. Therefore, the two rotary shafts can be more preferably pivotably connected without impairing the durability thereof, and the quietness thereof can be further improved. Further, even if a relative displacement in the circumferential direction, that is, a twist occurs between the two rotation shafts due to the rotational torque, the relative displacement is limited within a predetermined angle by the restricting means. Therefore, when excessive rotational torque is transmitted, the relative displacement in the circumferential direction generated between the two rotation shafts can be suppressed, and the accompanying rotation transmission delay can be prevented.

  According to the present invention, it is possible to provide an electric power steering device with high silence and a connecting structure of a rotating shaft that enables the electric power steering device.

Hereinafter, an embodiment in which the present invention is embodied in a rack cross type electric power steering device (EPS) will be described with reference to the drawings.
As shown in FIG. 1, the EPS 1 of the present embodiment includes a rack shaft 2 that reciprocates in the axial direction in response to a steering operation, a hollow shaft 3 that is inserted through the rack shaft 2 and that is rotated by a motor, And a ball screw mechanism 4 that converts the rotation of the hollow shaft 3 into the reciprocating motion of the rack shaft 2. That is, the EPS 1 of the present embodiment is a so-called rack assist type EPS that applies assist force to the steering system by reciprocating the rack shaft 2 in accordance with a steering operation by motor driving. This is a so-called rack-cross type EPS in which a certain motor 5 is arranged so that its axis is oblique to the rack shaft 2 (hollow shaft 3).

  More specifically, the EPS 1 of the present embodiment includes a housing 7 that houses the hollow shaft 3, the ball screw mechanism 4, and the input shaft 6 that transmits the rotation of the motor 5 to the hollow shaft 3. The housing 7 is formed with a first storage chamber 8 and a second storage chamber 9 which are formed in a substantially cylindrical shape, and the axis of the second storage chamber 9 is oblique to the axis of the first storage chamber 8. At the same time, one end thereof opens into the first storage chamber 8 and the other end opens to the outside of the housing 7. And the hollow shaft 3 is rotatably accommodated in the 1st accommodating chamber 8 along the axis line, and the input shaft 6 is accommodated rotatably in the 2nd accommodating chamber 9 similarly.

  In the present embodiment, a motor 5 as a drive source is attached to the external opening end 9 a of the second storage chamber 9, and one end of the output shaft 5 a of the motor 5 is in the second storage chamber 9. It is connected to the outer end 6a of the accommodated input shaft 6. Further, a bevel gear 12 is provided at the other end side of the input shaft 6, that is, the inner side end portion 6 b extended to the inner side opening end 9 b opened in the first housing chamber 8. A bevel gear 13 corresponding to the bevel gear 12 is attached to the outer periphery of the hollow shaft 3 accommodated in the chamber 8. The input shaft 6 and the hollow shaft 3 are coupled so that the rotation of the input shaft 6 can be transmitted to the hollow shaft 3 by meshing the bevel gear 12 and the bevel gear 13.

  On the other hand, the rack shaft 2 penetrates through the first housing chamber 8 in the axial direction and penetrates through the housing 7 so as to be inserted into the hollow shaft 3 housed in the first housing chamber 8. By being supported by a slide bearing 14 and a rack guide (not shown) provided in the housing 7, the housing 7 is supported by the housing 7 so as to be able to reciprocate along the axial direction. The rack shaft 2 is connected to the hollow shaft 3 via a ball screw mechanism 4 provided at one end of the hollow shaft 3.

  That is, the rotation of the motor 5 (the output shaft 5a) serving as the drive source is transmitted to the hollow shaft 3 through the input shaft 6 arranged obliquely. Then, the rotation of the hollow shaft 3 is converted into a reciprocating motion of the rack shaft 2 by the ball screw mechanism 4, and the rack shaft 2 moves in a direction corresponding to the steering operation, whereby an assist force is applied to the steering system. It is like that.

  In the present embodiment, the hollow shaft 3 includes a first shaft 15 provided with the bevel gear 13 and a second shaft 16 provided with the ball screw mechanism 4, and the first shaft 15 and the second shaft are provided. 16 is connected through a connecting member 17 interposed between the first shaft 15 and the second shaft 16 so as to be integrally rotatable and radially swingable. The ball screw mechanism 4 includes a cylindrical nut member 18 having a screw groove formed on the inner peripheral surface, a screw portion 19 formed on the outer periphery of the rack shaft 2, and both screws of the nut member 18 and the screw portion 19. A plurality of balls 20 are arranged in the rolling path formed by the grooves, and in this embodiment, the second shaft 16 is constituted by the nut member 18. The hollow shaft 3 is rotatably supported by the housing 7 by the first shaft 15 being pivotally supported by bearings 21 a and 21 b provided in the first storage chamber 8.

  That is, in the present embodiment, the bearing 22 is fixed to the outer periphery of the second shaft 16, but the bearing 22 is not fixed to the housing 7. A gap is formed between the outer ring and the inner peripheral surface of the housing 7. Accordingly, when a stress that causes the rack shaft 2 to bend is input to the rack shaft 2 by an external input or the like, the second shaft 16 swings in the radial direction, that is, the second shaft 16 is moved relative to the first shaft 15. The axial line of the shaft 16 can be shifted in the radial direction (radial displacement), thereby preventing the impact load from being transmitted to the housing 7.

(Rotating shaft connection structure)
Next, the connection structure of the 1st shaft and the 2nd shaft as a rotating shaft in EPS of this embodiment is demonstrated. 2A and 2B are perspective views showing a connection structure between the first shaft and the second shaft, FIG. 3 is an exploded perspective view of the connection member, FIG. 4 is a radial sectional view of the connection portion, and FIG. 5 is a schematic diagram showing the relationship between the engaging recess and the engaging protrusion that constitute the restricting means.

  As shown in FIGS. 2A and 2B, the connecting member 17 of this embodiment includes an annular ring member 25 formed of an elastic member, and the ring member 25 is provided along the circumferential direction thereof. Engaging grooves 26 penetrating the ring member 25 in the axial direction are formed at intervals of 90 °.

  As shown in FIG. 3, in this embodiment, the ring member 25 includes four rubber springs 31 formed in an arc shape and each of the rubber springs 31 arranged in an annular shape at equal intervals along the circumferential direction ( And a holder member 32 held at an interval of 90 °. In the present embodiment, the ring member 25 formed by each of the rubber springs 31 and the holder member 32 is formed by being accommodated in a substantially cylindrical cover 33.

  Specifically, the holder member 32 includes a pair of first holders 35 that are opposed to each other so as to straddle two adjacent rubber springs 31 that are annularly disposed, and abut against the inner peripheral surface 31a, and the first holder 35. One holder 35 and a pair of second holders 36 that abut on the outer peripheral surface 31b so as to straddle two adjacent rubber springs 31 at positions shifted by 90 ° in the circumferential direction are provided. In the present embodiment, the first holder 35 and the second holder 36 are made of metal (iron-based material). Then, holding pieces 35b and 36b are formed at both ends of each of the holder main bodies 35a and 36a of the first holder 35 and the second holder 36 each having an arc shape so as to come into contact with the circumferential end surface 31c of the corresponding rubber spring 31. ing. That is, in this embodiment, each rubber spring 31 is sandwiched between the first holder 35 and the second holder 36, and the movement of each rubber spring 31 in the circumferential direction is regulated by the holding pieces 35b and 36b. Thus, a ring member 25 is formed. And the engagement groove | channel 26 is formed of the clearance gap between each rubber spring 31 arrange | positioned cyclically | annularly at the equal intervals.

  On the other hand, as shown in FIGS. 2 (a) and 2 (b), a pair of engagement protrusions extending outward in the axial direction are provided on the connection side end portions 15a and 16a of the first shaft 15 and the second shaft 16, respectively. Portions 41 and 42 are provided, and the respective engaging projections 41 and 42 are disposed opposite to each other with the axes of the first shaft 15 and the second shaft 16 interposed therebetween (disposed at intervals of 180 ° in the circumferential direction). Yes. And in this embodiment, the 1st shaft 15 and the 2nd shaft 16 will be in the position which each engagement protrusion part 41 and 42 shifted | deviated 90 degree | times to the circumferential direction, ie, both linkage by the side of the 1st shaft 15 The straight line m connecting the mating protrusions 41 and the straight line n connecting the two engaging protrusions 42 on the second shaft 16 side are opposed to each other (see FIG. 4). The engaging protrusions 41 and 42 are inserted into the engaging grooves 26 of the corresponding connecting member 17 (ring member 25), so that they can rotate integrally via the connecting member 17 and in the radial direction. It is connected so that it can swing.

  More specifically, as shown in FIG. 4, in this embodiment, the circumferential width W0 of each engagement groove 26 on the ring member 25 side, the first shaft 15 inserted into each engagement groove 26, and the first shaft The circumferential widths W1 of the engaging protrusions 41 and 42 of the two shafts 16 are set to be substantially equal (specifically, slightly, W1> W0). In the present embodiment, each engagement groove 26 is formed by bringing the holding pieces 35b, 36b of the first holder 35 and the second holder 36 into contact with the circumferential end surface 31c of each rubber spring 31. The circumferential width W0 of each engagement groove 26 is the distance between the holding pieces 35b and the holding pieces 36b facing each other in the circumferential direction.

  In other words, in the present embodiment, in a state where the respective engagement protrusions 41 and 42 are inserted into the respective engagement grooves 26 and engaged with the respective engagement grooves 26, the circumferential clearance is zero. Thus, the engagement protrusions 41 and 42 are engaged with each other in the corresponding engagement groove 26 without any gap in the circumferential direction (rotation direction). And when the stress which displaces the 1st shaft 15 and the 2nd shaft 16 to radial direction generate | occur | produces, each rubber spring 31 which comprises the ring member 25 is elastically deformed by the stress.

  That is, in the connecting member 17 according to the present embodiment, the elastic deformation of each rubber spring 31 causes the known Oldham coupling operation principle, that is, the sliding (sliding in the radial direction) of each shaft engagement protrusion in the engagement groove. It corresponds to the even number). The elastic deformation allows the radial displacement of the first shaft 15 and the second shaft 16, that is, the radial swing of the second shaft 16 relative to the first shaft 15.

  Further, as shown in FIG. 5, in the present embodiment, the axial length L1 of each engaging protrusion 42 on the second shaft 16 side is set to be longer than the axial length L0 of the ring member 25. (L1> L0), each engaging protrusion 42 penetrates the ring member 25 in its assembled state, and its tip 42a protrudes toward the first shaft 15 side. The connecting side end 15a of the first shaft 15 has a circumferential width W2 (W2> W1) wider than the circumferential width W1 of each engaging protrusion 42 at a position corresponding to each engaging protrusion 42. An engaging recess 43 having a recess is formed.

  That is, in the present embodiment, in the connected state, each engagement protrusion 42 on the second shaft 16 side penetrates the ring member 25 and its tip 42a is inserted into the engagement recess 43 on the first shaft 15 side. ing. The relative displacement in the circumferential direction between the first shaft 15 and the second shaft 16 is limited within a range of a predetermined angle θ by the tip 42a of the engagement protrusion 42 and the circumferential wall surface 43a of the engagement recess 43. It is like that. In the present embodiment, the circumferential width W2 of the engaging recess 43 is set so that the predetermined angle θ is about ± 1 °.

(Action / Effect)
Next, the operation and effect of the EPS of the present embodiment configured as described above will be described.
As described above, when a stress that causes the rack shaft to bend is input to the rack shaft, the rack shaft, the hollow shaft, and the housing that supports and accommodates them are rigidly connected to each other in the rack structure. The shaft cannot be allowed to bend, and abnormal noise may be generated by transmitting the stress directly to the housing.

  In view of this point, in this embodiment, the hollow shaft 3 includes a first shaft 15 that is pivotally supported by the housing 7 and a second shaft 16 that is provided with the ball screw mechanism 4. The second shaft 16 is a housing. 7 is connected to the first shaft 15 via the connecting member 17 so as to be rotatable together with the first shaft 15 so as to be swingable in the radial direction. Therefore, it is possible to allow the rack shaft 2 to bend, and even when a stress that causes the rack shaft 2 to be bent is applied, the stress is prevented from being directly transmitted to the housing 7. Occurrence of abnormal noise accompanying this can be prevented.

  An Oldham coupling is generally used as a structure for connecting a pair of coaxially arranged rotating shafts so that they can rotate together and swing in the radial direction. However, the Oldham joint is based on the sliding principle of each engagement protrusion in the engagement groove, that is, the sliding pair, and is engaged with the wall surface of the engagement groove in the engagement groove. A certain amount of gap (backlash) exists in the circumferential direction (rotation direction) between the protrusions. For this reason, when applied to an application where the start and stop and the reversal of the rotation direction are frequently repeated as in the rack assist type EPS hollow shaft, a hitting sound is generated due to this play and the silence is impaired. There is a problem.

  Therefore, conventionally, for example, in Japanese Patent Application Laid-Open No. 2004-324780 and Japanese Patent Application Laid-Open No. 2004-44709, an elastic member is interposed between the engagement groove and the engagement protrusion, and the wall surface of the engagement groove is formed by this elastic member. And the clearance between the engagement protrusions is eliminated. That is, the elastic deformation of the elastic member secures the radial displacement between the engagement groove and the engagement protrusion, and the hit sound caused by the rotation play between the engagement groove and the engagement protrusion. It prevents the occurrence.

  However, in such a configuration, since the elastic member interposed between the engagement groove and the engagement protrusion is thin, an appropriate radial displacement between the engagement groove and the engagement protrusion is obtained. It is difficult to achieve both the durability of the elastic member. That is, if the elastic member is made soft so as to ensure an appropriate radial displacement between the engagement groove and the engagement protrusion, the durability of the elastic member will be reduced, and conversely the elastic member If the elastic member is made hard in order to improve the durability, there is a problem that appropriate radial displacement between the engaging groove and the engaging protrusion cannot be ensured. Therefore, the actual situation is that it is difficult to apply to applications that require high durability such as EPS.

In this regard, in the EPS 1 of the present embodiment,
(1) The coupling member 17 is interposed between the first shaft 15 and the second shaft 16, and the engaging grooves into which the engaging protrusions 41 and 42 of the first shaft 15 and the second shaft 16 are inserted, respectively. A ring member 25 having 26 is provided. The ring member 25 itself is formed of an elastic material, and the engagement protrusions 41 and 42 are engaged with each other in the corresponding engagement groove 26 without any gap in the circumferential direction (rotation direction).

  With such a configuration, it is possible to eliminate the rotation play between the respective engagement grooves 26 and the respective engagement protrusions 41 and 42, and to prevent the occurrence of a hitting sound resulting therefrom. Then, by forming the ring member 25 itself from an elastic material, it is possible to achieve both appropriate radial displacement between the engagement grooves 26 and the engagement protrusions 41 and 42 and durability of the elastic member. be able to. Therefore, the first shaft 15 and the second shaft 16 can be more preferably pivotably connected without impairing the durability thereof, and the quietness thereof can be further improved.

  (2) The axial length L1 of each engaging protrusion 42 on the second shaft 16 side is set to be longer than the axial length L0 of the ring member 25 (L1> L0), and each engaging protrusion 42 is In the assembled state, the ring member 25 is penetrated, and the tip 42a protrudes toward the first shaft 15 side. The connecting side end 15a of the first shaft 15 has a circumferential width W2 (W2> W1) wider than the circumferential width W1 of each engaging protrusion 42 at a position corresponding to each engaging protrusion 42. An engagement recess 43 having a recess is provided, and the tip 42 a of the engagement protrusion 42 penetrating the ring member 25 is inserted into the engagement recess 43.

  With such a configuration, even when a relative displacement in the circumferential direction occurs between the first shaft 15 and the second shaft 16 due to the rotational torque, the engagement with the tip 42a of the engaging protrusion 42 is engaged. The circumferential wall surface 43a of the joint recess 43 comes into contact. As a result, the relative displacement is limited within a predetermined angle θ defined by the circumferential width W2 of the engaging recess 43 and the circumferential width W1 of each engaging protrusion 42. Therefore, when an excessive rotational torque is transmitted, the relative displacement in the circumferential direction, that is, the twist generated between the first shaft 15 and the second shaft 16 can be suppressed, and the accompanying rotation transmission delay can be prevented.

  (3) The ring member 25 is made of metal that holds four rubber springs 31 formed in an arc shape and the annularly arranged rubber springs 31 at equal intervals (90 ° intervals) along the circumferential direction. The first holder 35 and the second holder 36 are configured. Each engagement groove 26 is formed by bringing the holding pieces 35 b and 36 b of the first holder 35 and the second holder 36 into contact with the circumferential end surface 31 c of each rubber spring 31.

  With such a configuration, a metal layer is formed on the circumferential wall surface 43 a of each engagement groove 26. Accordingly, it is possible to prevent the rubber springs 31 constituting the ring member 25 from being worn by friction with the engagement protrusions 41 and 42, and to further improve the durability thereof.

In addition, you may change each said embodiment as follows.
In the present embodiment, the present invention is embodied in a rack cross type electric power steering device (EPS), but may be embodied in a coaxial EPS. Further, the rotating shaft coupling structure may be applied to uses other than the rack assist type EPS.

  -In this embodiment, between the 1st shaft 15 and the 2nd shaft 16 by the front-end | tip 42a of each engagement protrusion 42 by the side of the 2nd shaft 16, and the engagement recessed part 43 provided in the 1st shaft 15 side. The restriction means for limiting the circumferential relative displacement is configured. However, the present invention is not limited to this, and it is possible to extend the axial length of each engaging protrusion 41 on the first shaft 15 side to provide an engaging recess on the second shaft 16 side, and to include both. Also good. That is, the restricting means only needs to restrict the circumferential movement of at least one of the engaging protrusions 41 and 42.

  -Furthermore, you may provide the control member which comprises a control means in the connection member side. Specifically, as shown in FIGS. 6 and 7, four rubber springs 51 formed in an arc shape and each of the rubber springs 51 arranged in an annular shape are equally spaced along the circumferential direction (90 °). A connecting member 53 (ring member 54) is constituted by a substantially bottomed cylindrical holder member 52 held at an interval. The bottom 52a of the holder member 52 is provided with a through hole 52b through which the rack shaft 2 is inserted, and the insertion hole 55 through which each engagement protrusion 41 on the first shaft 15 side is inserted, and the second shaft 16 side. An insertion hole 56 through which each of the engaging protrusions 42 is inserted is formed. The restricting means may be configured by at least one of the insertion holes 55 and 56 and the engaging protrusions 41 and 42 inserted therethrough.

  More specifically, as shown in FIG. 8, in the connection member 53, the circumferential width W <b> 3 of the insertion hole 56 through which the engagement protrusion 42 on the second shaft 16 side is inserted in the holder member 52 as the restricting means. It is set wider than the circumferential width W1 of the engaging protrusion 42 (W3> W1). As a result, the relative displacement in the circumferential direction between the first shaft 15 and the second shaft 16 corresponds to a predetermined angle θ (corresponding to the circumferential width W3 of the insertion hole 56 and the circumferential width W1 of the engaging protrusion 42. For example, it is limited within about ± 1 °.

  That is, by setting the circumferential width of the insertion hole 55 through which the engagement protrusion 41 on the first shaft 15 side is inserted substantially equal to the circumferential width (L1) of the engagement protrusion 41, the connecting member 53 is The first shaft 15 and the first shaft 15 rotate integrally with no rotation delay. Accordingly, the insertion hole 56 through which the engagement protrusion 42 on the second shaft 16 side is inserted can have the same function as the engagement recess 43 provided on the first shaft 15 side in this embodiment. As a result, as in the present embodiment, even when a large rotational torque is transmitted, the relative displacement in the circumferential direction between the first shaft 15 and the second shaft 16, that is, the twist, is suppressed and accompanied. Rotation transmission delay can be prevented. The circumferential width of the insertion hole 55, not the insertion hole 56, may be set wider, and at least one circumferential width of the insertion holes 55, 56 may be set wider.

  -Moreover, as shown in FIG. 9, it is good also as a structure using the cyclic | annular ring member 57 integrally shape | molded by the elastic member.

The schematic block diagram of EPS (electric power steering device) of this embodiment. (A) (b) The perspective view which shows the connection structure between a 1st shaft and a 2nd shaft. The disassembled perspective view of the connection member of this embodiment. The radial direction sectional view of the connecting member of this embodiment. The schematic diagram which shows the relationship between an engagement recessed part and an engagement protrusion. The disassembled perspective view of the connection member of another example. The radial direction sectional drawing of the connection member of another example. The schematic diagram which shows the relationship between an insertion hole and an engagement protrusion. The perspective view of the connection member of another example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device (EPS), 2 ... Rack shaft, 3 ... Hollow shaft, 4 ... Ball screw mechanism, 5 ... Motor, 7 ... Housing, 15 ... 1st shaft, 16 ... 2nd shaft, 17, 53 ... Connection member, 18 ... nut member, 25, 54, 57 ... ring member, 26 ... engagement groove, 31, 51 ... rubber spring, 35 ... first holder, 36 ... second holder, 35b, 36b ... holding piece, 41 , 42 ... engaging protrusion, 42 a ... tip, 43 ... engaging recess, 43 a ... circumferential wall surface, 55, 56 ... insertion hole, L0, L1 ... axial length, W0, W1, W2, W3 ... circumferential direction Width, θ: predetermined angle, m, n: straight line.

Claims (6)

A rack shaft provided so as to be capable of reciprocating in an axial direction; a hollow shaft through which the rack shaft is inserted and rotated by a motor drive; and a ball screw mechanism for converting rotation of the hollow shaft into reciprocating motion of the rack shaft; An electric power steering device comprising a housing for housing the hollow shaft and the ball screw mechanism,
The hollow shaft includes a first shaft that is pivotally supported by the housing and a second shaft that is provided with the ball screw mechanism, and an axial line is interposed between one end of the first shaft and the second shaft, respectively. A pair of engaging protrusions extending in the axial direction are provided at opposing positions, and the first shaft and the second shaft are arranged so that straight lines connecting the both engaging protrusions are orthogonal to each other, and Between the first shaft and the second shaft, a connecting member having a ring member in which an engaging groove into which each engaging protrusion of the first shaft and the second shaft is inserted is interposed,
The ring member is made of an elastic material, and the engagement protrusions of the first shaft and the second shaft are inserted into the corresponding engagement grooves, thereby causing the engagement grooves in the circumferential direction. An electric power steering device characterized by being engaged without a gap. The electric power steering apparatus according to claim 1, wherein
Restricting means for restricting relative displacement in the circumferential direction between the first shaft and the second shaft within a predetermined angle range by restricting movement in the circumferential direction of at least one of the engagement protrusions. An electric power steering device characterized by that. The electric power steering apparatus according to claim 2,
At least one of the engaging protrusions on the first shaft side or the second shaft side has an axial length longer than an axial length of the ring member, and the first shaft or the second shaft. Is formed with an engagement recess into which the engagement protrusion is inserted at a position opposite to the elongated engagement protrusion,
The restricting means is formed by setting a circumferential width of the engaging recess to be wider than a circumferential width of the engaging protrusion corresponding to the predetermined angle range;
An electric power steering device. The electric power steering apparatus according to claim 2,
The connecting member is provided with a restricting member having an insertion hole formed corresponding to the engaging protrusion of the first shaft and the second shaft,
The restricting means is formed by setting at least one circumferential width of the insertion hole wider than a circumferential width of the engaging protrusion corresponding to the predetermined angle range;
An electric power steering device. In the electric power steering device according to any one of claims 1 to 4,
A metal layer is formed on a circumferential wall surface of each engagement groove;
An electric power steering device. A pair of engaging protrusions extending in the axial direction are provided at opposite positions of the pair of rotating shafts arranged coaxially at positions facing each other across the axis, and straight lines connecting the both engaging protrusions are mutually connected. Both rotating shafts are arranged so as to be orthogonal to each other, and a rotating shaft coupling structure in which a ring member having an engaging groove into which each engaging protrusion of each rotating shaft is inserted is interposed between the rotating shafts. Because
The ring member is made of an elastic material, and the engagement protrusions are engaged with the engagement grooves without any gaps in the circumferential direction by being inserted into the corresponding engagement grooves.
Restricting means for limiting relative displacement in the circumferential direction between the two rotation shafts within a predetermined angle range by restricting movement in the circumferential direction of at least one of the engaging protrusions. The rotating shaft connection structure.

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