JP5626125B2 - Column unit for electric power steering system - Google Patents

Description

  The present invention is an improvement of a column unit for an electric power steering apparatus, which is a combination of a steering column for rotatably supporting a steering shaft on the inner side and a housing for housing components of the electric power steering apparatus. About.

   The automobile steering apparatus is configured as shown in FIG. 10, and transmits the rotation of the steering wheel 1 to the input shaft 3 of the steering gear unit 2, and a pair of left and right tie rods 4 in accordance with the rotation of the input shaft 3. 4 is pushed and pulled to give a steering angle to the front wheels. The steering wheel 1 is supported and fixed to the rear end portion of the steering shaft 5, and the steering shaft 5 is rotatably supported by the steering column 6 with the cylindrical steering column 6 inserted in the axial direction. Has been. The front end portion of the steering column 6 houses a worm reducer 7 and a torque measuring device 8 (see FIG. 11 described later and FIG. 1 showing the embodiment of the present invention), which are components of the electric power steering apparatus. The housing 9 is connected and fixed to the rear end portion. The housing 9 supports and fixes an electric motor 10 which is a power source of the electric power steering device.

  When the steering shaft 5 is rotated by the steering wheel 1, the direction and magnitude of torque applied to the steering shaft 5 is measured by the torque measuring device 8. The torque measuring device 8 is rotatably supported in the housing 9 and is connected to the input shaft 12 and the output shaft 13 by a torsion bar 11, and the relative displacement amount in the rotational direction between the shafts 12 and 13. Displacement measuring instrument 14 (see FIGS. 1 and 11). Since the configuration and operation of such a torque measuring device 8 are conventionally known, detailed description thereof will be omitted. Based on the measurement result of the torque measuring device 8, the electric motor 10 applies an auxiliary torque in the same direction as the operation direction of the steering wheel 1 to the output shaft 13, and the output shaft 13 is applied to the steering shaft 5. To rotate with a torque larger than the torque input to the input shaft 12.

  The front end portion of the output shaft 13 is connected to the rear end portion of the intermediate shaft 16 via a universal joint 15a, and the front end portion of the intermediate shaft 16 is connected to the input shaft 3 via another universal joint 15b. doing. The structure shown in FIG. 10 incorporates a tilt mechanism for adjusting the vertical position of the steering wheel 1 and a telescopic mechanism for adjusting the front-rear position. For this purpose, the intermediate portion of the steering column 6 is supported on the support bracket 18 supported by the vehicle body 17 so that the vertical position and the front-rear position can be adjusted. Further, in order to constitute the tilt mechanism, a support cylinder 19 provided at the front upper end portion of the housing 9 is supported with respect to the vehicle body 17 so as to be capable of swinging displacement about the horizontal axis. In order to constitute the telescopic mechanism, the steering shaft 5 is a combination of an inner shaft and an outer shaft so that torque can be transmitted and can be extended and contracted, and the steering column 6 is connected to the outer column and the inner shaft. It is a combination of a column and a telescopic combination.

  As described above, the column unit for the electric power steering apparatus in which the steering column 6 and the housing 9 are combined. In order to reduce the weight of the housing 9 and reduce the cost, the housing 9 is made of a synthetic resin. Is described in Patent Document 1. FIG. 11 shows an example of a conventional structure of a column unit for an electric power steering apparatus described in Patent Document 1. In the case of this conventional structure, each of the sensor housing 20 and the gear housing 21 made of a synthetic resin such as polyamide resin is welded to form a hollow housing 9a. Thus, even when the housing 9a is made of a synthetic resin, the steering column 6a needs to be made of a metal such as an iron-based alloy such as carbon steel in order to ensure strength and rigidity. For this reason, in the case of the conventional structure shown in FIG. 11, the front end portion of the cylindrical steering column 6a made of metal is externally fitted to the cylindrical portion 22 formed at the rear end portion of the housing 9a. The rear end portion of the housing 9a and the front end portion of the steering column 6a are coupled.

  However, in the case of the conventional structure as described above, it is difficult to increase the coupling strength between the rear end portion of the housing 9a and the front end portion of the steering column 6a. That is, even when the rear end portion of the housing 9a and the front end portion of the steering column 6a are fitted and fixed, the linear expansion between the synthetic resin constituting the housing 9a and the metal constituting the steering column 6a. Based on the difference in rate, there is a possibility that the fitting strength of the joint fixing portion between the both end portions gradually decreases. In particular, when an increase in the outer diameter of the cylindrical portion 22 due to a temperature rise is larger than an increase in the inner diameter of the front end portion of the steering column 6a, the force (surface pressure) that suppresses the outer peripheral surface of the cylindrical portion 22 is increased. Becomes excessive, and the cylindrical portion 22 is plastically deformed in a direction of decreasing the outer diameter. As a result, the fitting strength of the joint fixing portion is significantly reduced.

  Further, the strength and rigidity of the joint between the two ends based on the interference fit between the metal and the synthetic resin are not necessarily large from the initial stage. Therefore, even when a force in the bending direction is applied to the coupling portion when adjusting the height of the steering wheel 1, the outer peripheral surface of the cylindrical portion 22 is plastically deformed, and the fitting strength of the coupling fixing portion is reduced. there is a possibility. In any case, when this fitting strength is reduced, there is a possibility that a problem such as a loose joint between the steering column 6a and the housing 9a may occur. Such a problem is that the steering column is made of a metal that easily obtains the required strength and rigidity, such as an iron-based alloy, and the housing is made of a metal that constitutes the steering column, such as an aluminum-based alloy, although it is lightweight. It can also occur when made of a soft metal.

JP 2009-298246 A

  In view of the circumstances as described above, the present invention has been invented to realize a structure capable of ensuring the strength and rigidity of the connecting portion between the rear end portion of the housing and the front end portion of the steering column.

The column unit for an electric power steering apparatus of the present invention includes a steering column and a housing.
Of these, the steering column has a steering shaft inserted therein and is made of metal and has a cylindrical shape.
The housing is coupled and fixed to the front end portion of the steering column, and houses at least a part of the components of the electric power steering device, and is softer than the metal constituting the steering column. Cast products or synthetic resin injection molded products.
Furthermore, in the column unit for an electric power steering apparatus according to the present invention, the front end portion of the steering column has a bent raised portion formed by bending the front end portion radially outward and both inner and outer peripheral surfaces of the steering column or A thinning portion is formed which communicates both side surfaces. Then, the housing is cast or injection molded in a state where the thinned portion and the bent raised portion are embedded inside.

Particularly, in the case of the invention described in claim 1, the front end portion of the steering column is provided with the bending raising portion, the large-diameter cylindrical portion, and a plurality of through holes.
Among these, the bending raising part is a partial conical cylinder shape inclined in the direction in which the diameter increases toward the front.
The large-diameter cylindrical portion is bent forward from the large-diameter side end of the bent raising portion.
Moreover, each said through-hole is formed in the circumferential direction several places of the said bending raising part and the said large diameter cylindrical part, and each is the said thinning part.
Then, the rear end portion of the housing, the bent-up portion and the causes are present in the inner diameter side and outer diameter side of the large diameter cylindrical portion, a portion of the metal or synthetic resin constituting the housing, each of said permeable It enters into the hole.

On the other hand, in the case of the invention described in claim 2, the bending raising portion and a plurality of through holes are provided.
Of these, the bent raised portion is provided at the front end edge of the steering column, and has an outward flange shape that is bent outward in the radial direction.
Each of the through holes is formed at a portion closer to the rear than the bent raised portion at the bent raised portion and the front end portion of the steering column.
Then, the rear end portion of the housing is present on both the front and rear sides of the bent raising portion and the inner diameter side and the outer diameter side of the front end portion of the steering column, and a part of the metal or synthetic resin constituting the housing is provided. , It is inserted into each through hole.

  According to the column unit for an electric power steering apparatus of the present invention configured as described above, it is possible to ensure the strength and rigidity of the connecting portion between the rear end portion of the housing and the front end portion of the steering column.

FIG. 3 is a cross-sectional view of a main part showing a first example of an embodiment of the present invention. Sectional drawing which takes out and shows the main part of a housing, and a steering column from FIG. The perspective view which shows the front-end part of a steering column in the state before combining with the main part of a housing. The figure equivalent to the A section of FIG. 2 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 3 which shows the 3rd example of embodiment of this invention. Similarly, the same figure as FIG. The end view (a) and sectional drawing (b) of the front-end part of a steering column which show the 1st example of the reference example regarding this invention . The end view (a) and side view (b) of the front end part of the steering column showing the second example . The figure similar to FIG. 8 which shows the 3rd example . The partial cutting side view which shows an example of an electric power steering device. Sectional drawing which shows the principal part which shows an example of the conventional structure.

[First example of embodiment]
1 to 3 show a first example of an embodiment of the present invention corresponding to claim 1 . The feature of the present invention including this example is the structure of the coupling and fixing portion between the front end portion of the steering column and the rear end portion of the housing for the electric power steering apparatus. The structure and operation of other parts are the same as those of the conventionally known column unit for an electric power steering apparatus including the structure shown in FIG. Therefore, the description of the conventionally known structural portion will be omitted or simplified, and hereinafter, the description will focus on the features of this example and the portions that have not been described previously.

When the column unit for the electric power steering apparatus of this example is formed by injection-molding the main portion 23 with a synthetic resin, the front end portion of the steering column 6b and the rear end portion of the main portion 23 constituting the housing 9b are: It is integrally connected and fixed.
The housing 9b is formed by hollow molding by bonding and fixing the main portion 23 and the lid portion 24, each of which is formed by injection molding the same type of synthetic resin, by an appropriate method such as screwing or welding. Yes. A front end portion (left end portion in FIG. 1) of the input shaft 12, a rear end portion (right end portion in FIG. 1) to an intermediate portion of the output shaft 13, a torsion bar 11, a torque measuring device 8, and the like are housed. Further, two positions separated in the axial direction at the intermediate portion of the output shaft 13 are rotatably supported by a pair of rolling bearings 25a and 25b inside the housing 9b. A worm wheel 26 is externally fixed to the output shaft 13 by serration engagement or the like between the two rolling bearings 25a and 25b. The worm wheel 26 and a worm 27 that is rotationally driven by the electric motor 10 (see FIG. 10) are engaged with each other so that auxiliary torque is applied to the output shaft 13.

  On the other hand, the steering column 6b is a metal tube (drawing tube or electric sewn tube) made of an iron alloy such as carbon steel or an aluminum alloy. It has a diameter. That is, a bending raising portion 28, a large-diameter cylindrical portion 29, and a plurality of through holes 30a and 30b, each of which is a thinning portion, are formed at the front end portion of the steering column 6b. Among these, the bending raising part 28 is a partial conical cylinder shape inclined in a direction in which the diameter increases toward the front. The large-diameter cylindrical portion 29 has a cylindrical shape that is concentric with a main body portion of the steering column 6b (a portion closer to the rear of the bending raising portion 28). Further, a plurality of each of the through holes 30a and 30b are formed in the bending raised portion 28 and the large diameter cylindrical portion 29, respectively. In the illustrated example, the numbers of the through holes 30a and 30b formed in the bent raised portion 28 and the large diameter cylindrical portion 29 are the same, and the phases in the circumferential direction are made to coincide with each other. However, the number of these through holes 30a and 30b can be set freely (however, preferably 3 or more, preferably 6 or more in total, respectively) according to the required strength, etc. There is no need to match the phase with the large-diameter cylindrical portion 29.

  The steering column 6b and the main portion 23 of the housing 9b, which are formed with the bent raised portion 28, the large-diameter cylindrical portion 29, and the plurality of through holes 30a and 30b at the front end portion, The housing 9b is bonded and fixed when it is injection-molded with a thermoplastic synthetic resin. That is, in a state where the front end portion of the steering column 6b is positioned at a predetermined position in a cavity of a mold for injection molding the main portion 23, the synthetic resin is heated and melted in the cavity. Send it in. The molten resin fed into the cavity is cooled and solidified in the cavity while embedding the front end portion of the steering column 6b to constitute the main portion 23. At this time, a part of the molten resin enters the through holes 30a and 30b and solidifies in the through holes 30a and 30b. As a result, in the synthetic resin constituting the main portion 23, a portion existing on the outer diameter side and a portion existing on the inner diameter side from the front end portion of the steering column 6b are integrally coupled. At the same time, the main portion 23 and the steering column 6b are firmly coupled. The type of the synthetic resin is not particularly limited as long as the required strength, rigidity, and durability can be secured. For example, polyamide resin (PA), polyethylene terephthalate (PET) or the like in which a reinforcing material such as glass fiber or carbon fiber is mixed can be preferably used.

  As described above, the column unit for the electric power steering apparatus of the present example has a front end portion of the iron-based alloy steering column 6b in which the plurality of through holes 30a and 30b are formed, the main end of the synthetic resin housing 9b. Since it is embedded and fixed at the rear end portion of the portion 23, the strength and rigidity of the joint portion between the steering column 6b and the main portion 23 can be sufficiently increased. For this reason, even if it is used for a long period of time accompanied by a temperature change, there is no problem that the coupling portion between the steering column 6b and the housing 9b is rattled.

[Second Example of Embodiment]
FIG. 4 also shows a second example of the embodiment of the invention corresponding to claim 1 . In the case of this example, the thickness of the rear end portion of the main portion 23a constituting the housing is made thinner than in the case of the first example of the above-described embodiment. Instead, reinforcing ribs 31 are formed at a plurality of locations in the circumferential direction on the outer surface of the main portion 23a.
Since the configuration and operation of the other parts are the same as in the first example of the embodiment described above, overlapping illustrations and descriptions are omitted.

[Third example of embodiment]
5 to 6 show a third example of the embodiment of the invention corresponding to claim 2 . In the case of this example, an outward flange-shaped bent raised portion 28a is formed by bending the front end edge portion of the steering column 6c outward in the radial direction and bending substantially at a right angle. A plurality of through holes 30a and 30b are formed in the bent portion 28a and the front end portion of the steering column 6c in the rear portion of the bent portion 28a. When the main portion 23b constituting the housing is injection-molded, the front end portion of the steering column 6c including the bent raised portion 28a is embedded in the rear end portion of the main portion 23b, and these steering columns 6c and the main part 23b are coupled and fixed.
Since the configuration of the other parts is the same as that of the second example of the above-described embodiment, a duplicate description is omitted.

[ First example of reference example ]
FIG. 7 shows a first example of a reference example relating to the present invention . Also in the case of this reference example , an outward flange-shaped bent raising portion 28a is formed by bending the front end edge portion of the steering column 6d outward in the radial direction and bending substantially at a right angle. Particularly in the case of this reference example , a plurality of cutouts 32, 32 are formed in the outer peripheral edge portion of the bent raised portion 28a. When the housing is injection-molded, the housing and the steering column 6d are coupled and fixed in a state where a part of the synthetic resin constituting the housing is inserted into the notches 32 and 32. .
Since the configuration of the other parts is the same as that of the third example of the above-described embodiment, the overlapping description is omitted.

The present invention is not limited to a structure in which the housing is made of a synthetic resin, but can be implemented in a structure in which the housing is made of an aluminum alloy.
The structure shown in FIGS. 8 to 9 is also considered as a structure for embedding and supporting the front end portion of the steering column in the rear end portion of the housing, and for improving the coupling strength between the steering column and the housing. It is done. Among these, the structure of the 2nd example of the reference example shown in FIG. 8 makes the shape of the large diameter cylindrical part 29a provided in the front-end part of the steering column 6e the waveform regarding the circumferential direction. Further, the structure of the third example of the reference example shown in FIG. 9 does not form a bend raising portion at the front end portion of the steering column 6f, but forms embossed projections 33, 33 at the front end portion of the steering column 6f. Is. In any structure, the coupling strength between the steering column and the housing can be improved, but the apparent thickness (cross section) of the portion embedded in the rear end of the housing at the front end of the steering column. 1/2) of the difference in diameter between the circumscribed circle and the inscribed circle related to the shape is increased. As a result, the thickness dimension of the rear end portion of the housing is partially reduced (at the portion corresponding to the top of the corrugation and the top of the projections 33 and 33), and the thickness and weight are reduced, and the durability of the portion is ensured. It may be difficult to achieve both. On the other hand, in the case of the present invention, it is easy to achieve both.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering gear unit 3 Input shaft 4 Tie rod 5 Steering shaft 6, 6a, 6b, 6c, 6d, 6e, 6f Steering column 7 Worm reduction gear 8 Torque measuring device 9, 9a, 9b Housing 10 Electric motor 11 Torsion bar DESCRIPTION OF SYMBOLS 12 Input shaft 13 Output shaft 14 Displacement measuring instrument 15a, 15b Universal joint 16 Intermediate shaft 17 Car body 18 Support bracket 19 Support cylinder 20 Sensor housing 21 Gear housing 22 Cylindrical part 23, 23a, 23b Main part 24 Lid part 25a, 25b Rolling bearing 26 Worm wheel 27 Worm 28, 28a Bending part 29, 29a Large diameter cylindrical part 30a, 30b Through hole 31 Reinforcing rib 32 Notch 33 Protrusion

Claims (2)

The steering column includes: a cylindrical steering column through which a steering shaft is inserted; and a housing which is coupled and fixed to a front end portion of the steering column and accommodates at least a part of components of the electric power steering device. Is made of metal, and this housing is a column unit for an electric power steering device which is a cast product made of a soft metal or an injection molded product of a synthetic resin compared to the metal constituting the steering column,
Wherein provided on the front end portion of the steering column, comprising causing bending the front end portion radially outwardly, a partially conical tubular bent-up portion inclined in a direction in which the diameter becomes larger toward the front, raised the bending A large-diameter cylindrical portion that is bent forward from the large-diameter side end portion of the portion, and the bending-raised portion and the large-diameter cylindrical portion that are formed at a plurality of locations in the circumferential direction. A plurality of through-holes, which are thinning portions that allow both side surfaces to communicate with each other, and the housing embeds each of the through-holes and the bent raising portion inside , and the rear end portion of the housing is bent. with present on a raised portion and the inner diameter side of the large diameter cylindrical portion and the outer diameter side, a part of metal or synthetic resin constituting itself, the state that has entered into the respective through holes, are cast or injection molded Electric power steering apparatus for a column unit. The steering column includes: a cylindrical steering column through which a steering shaft is inserted; and a housing which is coupled and fixed to a front end portion of the steering column and accommodates at least a part of components of the electric power steering device. Is made of metal, and this housing is a column unit for an electric power steering device which is a cast product made of a soft metal or an injection molded product of a synthetic resin compared to the metal constituting the steering column,
An outward flange-shaped bending raising portion that is bent at the front end portion of the steering column and is bent outward in the radial direction, which is formed by bending the front end portion radially outward, and the bending raising portion and the steering column. A plurality of through holes formed at the front end portion of the steering column at a position closer to the rear than the bent raising portion, each of which is a thinning portion that allows both the inner and outer peripheral surfaces or both side surfaces of the steering column to communicate with each other. Embed each of these through holes and the bent raised portion inside , and the rear end portion of the through hole and the front and rear sides of the bent raised portion and the inner diameter side and the outer diameter side of the front end portion of the steering column. with present, part of the metal or synthetic resin constituting itself, the state that has entered into the hole, the electric power steering instrumentation that is cast or injection molded Use column unit.

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