JP4235892B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus.
[0002]
[Prior art]
An electric power steering apparatus (EPS) for automobiles includes a column type EPS in which an electric motor and a control component for driving and controlling the electric motor are arranged in the vicinity of a housing that supports a steering shaft and the like.
Usually, in this type of EPS, the control component is housed in a casing, and the casing is fixed to the housing with a separate heat sink that dissipates heat generated from the control component. Typically, this heat sink has a cutting process on the surface that comes into contact with the casing, so that the contact state with the casing is good and heat from the control unit is easily transferred to the heat sink.
[0003]
Further, a power steering device has been proposed in which a casing is fixed to a housing by sandwiching a sheet having elasticity and thermal conductivity instead of a heat sink (see, for example, Patent Document 1).
Furthermore, an electric power steering apparatus in which a heat sink is integrally formed with the housing has been proposed (see, for example, Patent Document 2).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-24847.
[Patent Document 2]
JP 2002-308122 A.
[0005]
[Problems to be solved by the invention]
However, if the heat sink or the sheet described in Patent Document 1 is formed as a single item, the number of components increases and the component cost increases.
On the other hand, since the electric power steering apparatus described in Patent Document 2 has the heat sink integrally formed with the housing, the number of parts can be reduced and the part cost can be reduced. However, if the heat sink and the housing are simply formed integrally, it is difficult to transfer heat generated from the control component to the heat sink, and there is a possibility that this heat can not be dissipated well.
[0006]
The present invention has been made under such a background, and an object of the present invention is to provide an electric power steering device that can reduce the cost of components and can dissipate heat generated from control components satisfactorily.
[0007]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the first invention includes a first housing that houses a control means for driving and controlling a steering assist electric motor, and a second housing that surrounds the periphery of the steering shaft, The first and second housings include first and second surfaces opposite to each other, respectively, and first and second direct contact portions that are in direct contact with each other over substantially the entire area of the first and second surfaces. Are provided, and the second housing integrally forms a radiator connected to the second direct contact portion, and the second housing houses a torque sensor for detecting torque applied to the steering member. A connecting member for connecting the torque sensor and the control means through the insertion hole provided in the region of the second direct contact portion, the first direct contact portion of the first housing. Connected to the connector provided on the outside to provide an electric power steering apparatus according to claim Rukoto.
[0008]
According to the present invention, since the radiator is provided integrally with the second housing, the number of components can be reduced, and the manufacturing cost can be reduced through the reduction of the component cost. In addition, the areas of the first direct contact portion and the second direct contact portion, that is, the area of the portion capable of transferring heat from the first housing to the second housing are made extremely large. For this reason, the heat generated from the control means can be transmitted well to the radiator via the first and second housings, and the heat generated from the control means can be dissipated well.
[0010]
Et al is, the area of the first direct contact portion can be widely ensured, it is possible to enhance the heat dissipation. Further, the connecting member can be easily attached to the connector without being obstructed by the second housing.
According to a second invention, in the first invention, the first direct contact portion is formed on a flat surface not provided with a groove. According to the present invention, the same effects as those of the first invention can be obtained. Furthermore, the area of the first direct contact portion can be substantially increased to further improve the heat dissipation. Moreover, the component cost of the first housing can be reduced, and the manufacturing cost can be further reduced.
[0011]
A third invention is characterized in that, in the first or second invention, a holding recess for holding a connecting member for connecting the control means and the electric motor is formed on the outer side of the second housing. . According to the present invention, a commonly used holding member such as a clip can be eliminated, and the number of parts can be further reduced to further reduce the manufacturing cost.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, the electric power steering apparatus 1 includes a first steering shaft 3 that is coupled to a steering member 2 such as a steering wheel so as to be integrally rotatable, and a steering member of the first steering shaft 3. 2 is provided with a second steering shaft 5 that is coaxially connected to an end portion on the opposite side to the end portion on which 2 is connected via a torsion bar 4.
[0013]
In addition, an intermediate shaft (not shown) can rotate integrally with the end of the second steering shaft 5 opposite to the end to which the torsion bar 4 is connected via a universal joint 6. It is connected.
As a result, the rotational force generated by the rotational operation of the steering member 2 is a steering mechanism including a pinion, a rack shaft and the like via the first steering shaft 3, the torsion bar 4, the second steering shaft 5, and the intermediate shaft (see FIG. (Not shown) to steer the wheels.
[0014]
In the electric power steering apparatus 1, for example, the axial direction of the first and second steering shafts 3 and 5 (hereinafter referred to as “axial direction”, see arrow S) with the steering member 2 on the upper side. It is installed on the vehicle body (not shown) at an angle. In the following description, for simplification, description will be made based on a state in which the axial direction is horizontal. Regarding the axial direction, the steering member 2 side is referred to as “upper side”, and the universal joint 6 side is referred to as “lower side”.
The first and second steering shafts 3 and 5 are concentrically surrounded by the housing 7. The housing 7 is made of, for example, an aluminum alloy, and includes a sensor housing 8 as a second housing and a gear housing 9 that are fitted together.
[0015]
For example, the first and second bearings 10 and 11 are fitted to the sensor housing 8 at one end and the other end, respectively, with the axial movement restricted, and the gear housing 9 is fitted with a third bearing at one end, for example. 12 is fitted by being restricted from moving in the axial direction. The first steering shaft 3 is rotatably supported by a first bearing 10, and the second steering shaft 5 is rotatably supported by second and third bearings 11 and 12.
[0016]
The gear housing 9 incorporates an electric motor 13 for steering assistance, for example, in the middle thereof, and houses a worm gear mechanism 14 as a speed reduction mechanism. The worm gear mechanism 14 engages with the worm 16 connected to the rotary shaft 15 of the electric motor 13 so as to be integrally rotatable, and meshes with the worm 16 so as to be able to transmit power, and rotates integrally with, for example, an intermediate portion of the second steering shaft 5. And a worm wheel 17 that is capable of being restricted in axial movement. Thus, by driving the electric motor 13, the rotational force (steering assisting force) of the electric motor 13 is applied to the second steering shaft 5 via the worm 16 and the worm wheel 17 to assist the driver's steering. can do.
[0017]
The first and second steering shafts 3 and 5 surround the torsion bar 4. In the vicinity of the torsion bar 4, a torque sensor 18 is provided for detecting the torque applied to the steering member 2 based on the relative displacement amounts of the first and second steering shafts 3 and 5 via the torsion bar 4. ing.
The torque sensor 18 is accommodated in the sensor housing 8. The torque sensor 18 includes a first detection ring 19 connected to the outer periphery of the first steering shaft 3 so as to be integrally rotatable on the outer side in the radial direction of the torsion bar 4, and a second on the outer side in the radial direction of the torsion bar 4. The second detection ring 20 connected to the outer periphery of the steering shaft 5 so as to be integrally rotatable, and the coil assembly 21 surrounding the outer periphery of the first and second detection rings 19, 20.
[0018]
The first detection ring 19 and the second detection ring 20 are disposed to face each other. The coil assembly 21 is connected to the control unit C, and a signal from the coil assembly 21 is input to the control unit C as a detection signal of the torque sensor 18.
A controller housing 25 as a first housing is fixed to the outer periphery of the sensor housing 8, and the controller housing 25 includes a control unit C and a drive circuit 26 as control means for driving and controlling the electric motor 13. Contained.
[0019]
The control unit C includes a CPU, a ROM storing a control program and the like, a RAM used as a work area for arithmetic processing, and the like. Further, a detection signal from the vehicle speed sensor 24 is input to the control unit C.
The control unit C determines a steering assist force to be generated by the electric motor 13 based on detection signals given from the torque sensor 18 and the vehicle speed sensor 24, and outputs a control signal to the drive circuit 26. The drive circuit 26 given a control signal from the control unit C supplies power to the electric motor 13 and drives the electric motor 13 based on the determined steering assist force.
[0020]
FIG. 2 is a sectional view of the sensor housing 8 showing a state where the coil assembly 21 of the torque sensor 18 is accommodated. 1 and 2, the coil assembly 21 includes a detection coil 23 that surrounds the outer circumferences of the first and second detection rings 19 and 20, a coil bobbin 27 that holds the detection coil 23, and a detection coil 23. A coil housing member 22 to be housed and a lead wire 28 are provided.
The detection coil 23 is for detecting the relative displacement of the first detection ring 19 with respect to the second detection ring 20 in a non-contact manner as a change in inductance.
[0021]
The coil bobbin 27 is formed in a cylindrical shape and surrounds the outer circumferences of the first and second detection rings 19 and 20 concentrically with a gap. The detection coil 23 is wound around the outer periphery of the coil bobbin 27.
The coil housing member 22 is formed of a powder compact obtained by compression-molding an insulating-coated soft magnetic powder, and includes a main body 29 and a lid 30. The main body 29 includes a body portion 31 that extends in the axial direction, and an annular edge portion 32 that extends radially inward from one axial end portion of the body portion 31. The lid 30 is formed in an annular shape and is fitted to the other axial end of the body portion 31 of the main body 29. The coil housing member 22 is fixed to the sensor housing 8.
[0022]
The lead wire 28 has one end 28 </ b> A connected to the detection coil 23, and the other end 28 </ b> B extending radially outward of the coil housing member 22. The other end 28 </ b> B of the lead wire 28 is connected to a substrate 36 disposed on the outer periphery of the cylindrical main body 34 of the sensor housing 8.
The coil bobbin 27 is disposed inside the body 31 of the main body 29 of the coil housing member 22 and concentrically with the body 31, one end in the axial direction abuts on the annular edge 32, and the other end is the lid 30. Abut.
[0023]
With the above configuration, the coil housing member 22 and the coil bobbin 27 form a closed space H in which the detection coil 23 is housed. The closed space H is filled with organic resin, and the detection coil 23 is fixed to the coil bobbin 27.
The outer surface portion of the coil housing member 22 is covered and protected by an insulating layer 33 containing a material such as a thermoplastic resin or a thermosetting resin.
[0024]
The coil assembly 21 is press-fitted into the holding hole 60 of the main body 34 of the sensor housing 8. At the time of the press-fitting, the insulating layer 33 and the coil housing member 22 are prevented from being galling and causing damage to the insulating layer 33 and the coil housing member 22.
That is, in the present embodiment, a taper 38 for guiding the coil assembly 21 so as to be concentric with the holding hole 60 is formed on one end 37 side in the axial direction of the holding hole 60. The taper 38 continuously increases in diameter from the one end 37 of the holding hole 60 along the axial direction. The width W of the taper 38 in the axial direction is, for example, 1.5 mm, and the inclination angle θ with respect to the axial direction of the taper 38 when viewed from the side surface of the sensor housing 8 is set to, for example, 20 degrees.
[0025]
As a result, when the coil assembly 21 is press-fitted into the holding hole 60 from the one end 37 side, the coil assembly 21 is moved along the taper 38 toward the holding hole 60, so that the coil assembly 21 is connected to the holding hole 60. Positioned to be concentric. Therefore, the coil assembly 21 can be smoothly press-fitted and damage to the coil assembly 21 due to galling can be minimized. Further, it is only necessary to provide the taper 38, and the cost is low.
[0026]
One end portion 39 of the coil assembly 21 press-fitted into the holding hole 60 is in contact with the annular step portion 40 of the main body portion 34, and movement to the axial one end portion 39 side is restricted. On the other hand, the other axial end portion 78 of the coil assembly 21 is in contact with the disc spring 42. The main body 34 of the sensor housing 8 is formed with a retaining ring retaining groove 43 at the lower end, and a retaining ring 44 made of, for example, a C-shaped retaining ring is retained with its axial movement restricted. Yes. The retaining ring 44 is in contact with the disc spring 42. As a result, the coil assembly 21 is restricted from moving toward the other end 78 in the axial direction by the retaining ring 44 via the disc spring 42.
[0027]
FIG. 3 is a bottom view of the sensor housing 8. FIG. 3 shows a state in which the connection member 45 is connected to the substrate 36. FIG. 4 is a bottom view of the controller housing 25. FIG. 5 is a partial cross-sectional side view of the sensor housing 8 when the controller housing 25 is fixed and viewed from the upper side on the left side. FIG. 6 is a side view of the sensor housing 8 as viewed from the upper side on the right side, showing a state in which the controller housing 25 is fixed.
[0028]
Referring to FIG. 4, the controller housing 25 includes a first surface 46 and a first direct contact portion 47 provided in substantially the entire area of the first surface 46.
The first surface 46 includes most of the bottom surface of the controller housing 25.
The first direct contact portion 47 is for transmitting heat generated from the control portion C and the drive circuit 26 to the outside of the controller housing 25. The first direct contact portion 47 is formed on a flat surface not provided with a groove, and a pair of bolt insertion holes 48 are formed in the region of the first direct contact portion 47.
[0029]
Referring to FIGS. 2 and 3, sensor housing 8 includes an overhanging portion 49 that extends radially outward from main body portion 34. The overhanging portion 49 includes a second surface 50, a second direct contact portion 51 provided almost all over the second surface 50, and an insertion hole 52 provided in the region of the second direct contact portion 51. With.
The second surface 50 includes most of the bottom surface of the sensor housing 8 and is formed as a flat surface.
[0030]
The second direct contact portion 51 is for receiving heat transmitted from the first direct contact portion 47 (see FIG. 4), and is formed in a shape substantially corresponding to the shape of the first direct contact portion 47. ing.
With reference to FIGS. 3 and 4, the controller housing 25 is attached to the overhanging portion 49 such that the first surface 46 faces the second surface 50 of the overhanging portion 49 of the sensor housing 8. . Thereby, the 1st and 2nd direct contact parts 47 and 51 contact mutually directly. Therefore, the heat generated from the controller C and the drive circuit 26 is directly transmitted from the first direct contact portion 47 to the second direct contact portion 51.
[0031]
Further, in the region of the second direct contact portion 51, bolt holes 53 are formed at positions corresponding to the positions of the respective bolt insertion holes 48 of the controller housing 25. As a result, the controller housing 25 is attached to the sensor housing by screwing the bolts 54 (see FIGS. 5 and 6) inserted into the respective bolt insertion holes 48 of the controller housing 25 into the bolt holes 53 of the second direct contact portion 51. 8 is fixed to the overhanging portion 49.
[0032]
With reference to FIGS. 3 and 5, a heat radiator 55 connected to the second direct contact portion 51 is integrally formed on the overhang portion 49 of the sensor housing 8. The radiator 55 is formed over substantially the entire area of the second direct contact portion 51 when viewed from the bottom surface (second surface 50) side of the overhang portion 49, and has a thickness of a certain level (for example, about 8 mm or more). Have.
In addition, the heat radiator 55 significantly improves heat dissipation by exposing a large part of the outer surface to increase the surface area. Specifically, the overhanging portion 49 expands in a planar shape as it extends radially outward from the main body portion 34.
[0033]
With reference to FIGS. 2 and 3, the second surface 50 is formed with an accommodation groove 56 for accommodating the substrate 36 in the region of the second direct contact portion 51. The accommodation groove 56 is covered with the first direct contact portion 47 of the controller housing 25.
The substrate 36 is accommodated in the accommodation groove 56 without protruding from the second direct contact portion 51, and is fixed to the sensor housing 8 with a screw 57. The substrate 36 includes a plurality of (for example, four) output terminals 61, for example.
[0034]
In addition, an insertion hole 52 is formed in the second surface 50, one end 58 is provided in the region of the second direct contact portion 51 and is connected to the accommodation groove 56, and the other end 59 is the first. It extends outside the area of the two direct contact portions 51.
A connection member 45 that connects the torque sensor 18 and the control unit C is inserted through the insertion hole 52. The connection member 45 has one end 62 connected to each output terminal 61. The connection terminal 45 is disposed so as to extend outside the region of the second direct contact portion 51 from the other end portion 59 of the insertion hole 52 through the accommodation groove 56 and the insertion hole 52.
[0035]
Referring to FIG. 5, the other end 63 of the connection member 45 is connected to a connector 64 that protrudes from the controller housing 25 to the outside of the first direct contact portion 47. The connector 64 is connected to the control unit C.
With reference to FIGS. 3 and 5, the first direct contact portion 47 and the second direct contact portion 51 are formed at the upper end (left side in FIGS. 3 and 5) of the second surface 50. A side wall 65 is provided for sealing between the opposing portions. The side wall 65 protrudes substantially vertically downward with respect to the second surface 50, and comes into contact with the upper end portion 66 (see FIG. 4) of the controller housing 25.
[0036]
When viewed from the bottom surface side of the protruding portion 49 of the sensor housing 8, the length N1 of the side wall 65 (the vertical length in FIG. 3) is at least the length N2 of the controller housing 25 (see FIG. 4, see FIG. 4). The length of the first and second direct contact portions 47 and 51 is covered from the upper side.
Thereby, in the state where the electric power steering apparatus 1 is attached to the vehicle body, for example, even if water droplets adhere, the water droplets travel along the surfaces of the main portion 34 and the overhanging portion 49 of the sensor housing 8 and the first and first Intrusion from the upper side between the opposing portions of the two direct contact portions 47 and 51 can be reliably prevented. Therefore, the sealing performance of the accommodation groove 56 can be further improved.
[0037]
Further, when the controller housing 25 is fixed to the sensor housing 8, the one end portion 66 of the controller housing 25 is brought into contact with the side wall 65, whereby the positioning can be performed with respect to the fixed position, and the fixing work can be easily performed. it can.
4 and 6, an output connector 67 connected to the drive circuit 26 (see FIG. 1) further protrudes from the controller housing 25. The output connector 67 is connected to an input connector 69 of a harness 68 as a connecting member for connecting the drive circuit 26 and the electric motor 13. A part of the wiring 70 of the harness 68 (a part of which is shown in cross section in FIG. 6) is held in a holding recess 72 formed in the outer portion 71 of the overhanging portion 49 of the sensor housing 8.
[0038]
The holding recess 72 extends, for example, linearly to the outer portion 71 of the overhang 49, and has a cross-sectional shape that substantially corresponds to the cross-sectional shape of the wiring 70 (for example, a semicircle). Thereby, the wiring 70 can be fixed by pushing the wiring 70 into the holding recess 72, and damage to the harness 68 due to vibration or the like can be prevented.
Thus, according to the present embodiment, since the radiator 55 is provided integrally with the overhanging portion 49 of the sensor housing 8, the number of parts can be reduced, and the manufacturing cost can be reduced through the reduction of the parts cost. it can.
[0039]
Further, the areas of the first direct contact portion 47 and the second direct contact portion 51, that is, the area of the portion capable of transferring heat from the controller housing 25 to the sensor housing 8 are extremely increased. For this reason, the heat emitted from the control part C etc. can be favorably transmitted to the radiator 55 via the controller housing 25 and the sensor housing 8, and the heat emitted from the control part C can be dissipated well.
Furthermore, by connecting the connection member 45 to the connector 64 provided outside the region of the first direct contact portion 47, a large area of the first direct contact portion 47 can be secured, and the heat dissipation can be further improved. . Further, the connection member 45 can be easily attached to the connector 64 without being obstructed by the sensor housing 8.
[0040]
Further, by forming the first direct contact portion 47 on a flat surface not provided with a groove, the area of the first direct contact portion 47 can be substantially increased, and the heat dissipation can be further improved. In addition, by making the first direct contact portion 47 a flat surface that can be easily processed, the component cost of the controller housing 25 can be reduced, and the manufacturing cost can be further reduced.
Furthermore, by holding the wiring 70 of the harness 68 in the holding recess 72, a commonly used holding member such as a clip can be eliminated, and the number of parts can be further reduced to further reduce the manufacturing cost.
[0041]
FIG. 7 is a perspective view of a sensor housing 8 showing another embodiment of the present invention. In the embodiment shown in FIG. 7, the same components as those in the embodiment shown in FIG. 1 to FIG.
Referring to FIG. 7, in the present embodiment, a flexible flat cable 73 (for example, FFC: Flexible Flat Cable) is used as a connecting member for connecting torque sensor 18 and control unit C instead of connecting member 45. ) Is used.
[0042]
The flat cable 73 has a plurality of conductive members 74, and these conductive members 74 are converged in a flat shape by a flexible material layer 75 formed of a material containing a synthetic resin such as vinyl chloride. . The flat cable 73 is directly fixed to the sensor housing 8 with screws 77. The flat cable 73 is connected by soldering one end 76 directly to the other end 28 </ b> B of the lead wire 28 of the torque sensor 18. Further, the other end 75 of the flat cable 73 is connected to a connector 64 protruding from the controller housing 25 as in the embodiment shown in FIGS.
[0043]
Also in this embodiment, the same effects as those of the embodiment shown in FIGS. 1 to 6 can be obtained. Furthermore, the flexible material layer 75 of the flat cable 73 is less likely to sag. For this reason, when fixing the controller housing 25 to the sensor housing 8, there is no possibility of being pinched | interposed between the controller housing 25 and the sensor housing 8, and it can prevent that malfunctions, such as a disconnection, arise.
In addition, by using the flat cable 73 as a connection member, the number of components can be reduced and the component cost can be further reduced as compared with a conventional connection member using a plurality of lead wires.
[0044]
The present invention is not limited to the contents of the above-described embodiments, and various modifications can be made within the scope of the claims.
For example, the controller housing 25 may be attached to the upper surface side of the sensor housing 8. In the embodiment shown in FIG. 7, a flexible printed circuit board called FPC (Flexible Printed Circuit) may be used instead of the flat cable 73.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a sensor housing showing a state in which a coil assembly of a torque sensor is accommodated.
FIG. 3 is a bottom view of the sensor housing.
FIG. 4 is a bottom view of a controller housing.
FIG. 5 is a partial cross-sectional side view of the sensor housing as viewed from the upper side on the left side, showing a state in which the controller housing is fixed.
FIG. 6 is a side view of the sensor housing viewed from the upper side on the right side, showing a state in which the controller housing is fixed.
FIG. 7 is a perspective view of a sensor housing showing another embodiment of the present invention.
[Explanation of symbols]
2 Steering member 3 First steering shaft (steering shaft)
5 Second steering shaft (steering shaft)
8 Sensor housing (second housing)
13 Electric motor 18 Torque sensor 25 Controller housing (first housing)
26 Drive circuit (control means)
45 connection member 46 first surface 47 first direct contact portion 50 second surface 51 second direct contact portion 52 insertion hole 55 radiator 64 connector 68 harness (connection member)
71 Outer part 72 Holding recess 73 Flat cable (connection member)
C Control unit (control means)

Claims (3)

A first housing that houses control means for driving and controlling a steering assist electric motor;
A second housing surrounding the periphery of the steering shaft,
The first and second housings include first and second surfaces, respectively, opposite each other;
First and second direct contact portions that are in direct contact with each other are provided over substantially the entire area of the first and second surfaces, respectively.
The second housing is integrally formed with a heat radiator connected to the second direct contact portion ,
The second housing comprises a sensor housing that houses a torque sensor for detecting torque applied to the steering member,
A connecting member for connecting the torque sensor and the control means is connected to a connector provided outside the region of the first direct contact portion of the first housing through an insertion hole provided in the region of the second direct contact portion. by an electric power steering apparatus according to claim Rukoto. 2. The electric power steering apparatus according to claim 1, wherein the first direct contact portion is formed on a flat surface not provided with a groove. 3. The electric power steering apparatus according to claim 1, wherein a holding recess for holding a connection member for connecting the control means and the electric motor is formed in an outer portion of the second housing.

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