JP5626128B2 - 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 device is configured as shown in FIG. 9, 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 according to 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 speed reducer 7 and a torque measuring device 8 (see FIG. 10 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 10). 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. 9 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. 10 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 construction shown in FIG. 10, the front end portion of a cylindrical steering column 6a made of metal, by externally fitted to the cylindrical portion 22 formed on 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, a through hole is formed in the front end portion of the steering column so that the inner and outer peripheral surfaces of the steering column communicate with each other. Further, a screw ring having a male screw formed on the outer peripheral surface is cast or injection molded in a state where the portion including the through hole is embedded inside the front end portion of the steering column. The housing is connected to the steering column by screwing the screw ring into a female screw formed on the inner peripheral surface of the stepped large-diameter portion formed on the inner peripheral surface of the rear end portion of the housing. It is fixed.

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.
Further, in the case of the present invention, the male thread formed on the outer peripheral surface of the screw ring coupled and fixed to the front end portion of the steering column and the front end portion of the steering column and the rear end portion of the housing; The steering column and the housing can be easily attached and detached because they are screwed and tightened with the female screw formed on the inner peripheral surface of the stepped large diameter portion formed on the inner peripheral surface of the rear end portion of the housing. For this reason, it is possible to reduce the labor and cost of repairing the electric power steering apparatus.

The principal part sectional view showing one example of an embodiment of the invention. The perspective view which shows the front-end part of the steering column which provided the screw ring. The A section enlarged view of FIG. The perspective view which shows the front-end part of the steering column before providing a screw ring. The figure similar to FIG. 3 which shows 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. 6 which shows the 3rd example . The end view (a) and sectional drawing (b) of the front-end part of a steering column which show the same 4th 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.

[ Example of Embodiment]
1 to 4 show an example of an embodiment of the present invention . The feature of the present invention lies in the structure of the connecting 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.

  The column unit for the electric power steering apparatus of this example is a screw ring 24 in which the front end portion of the steering column 6b and the rear end portion of the main portion 23 constituting the housing 9b are coupled and fixed to the front end portion of the steering column 6b. The joint is fixed through. The housing 9b is formed by hollow molding by bonding and fixing the main portion 23 and the lid portion 25, 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 26a and 26b inside the housing 9b. A worm wheel 27 is externally fixed to the output shaft 13 by serration engagement or the like between the two rolling bearings 26a and 26b. The worm wheel 27 and a worm 28 that is rotationally driven by the electric motor 10 (see FIG. 9) 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 (drawer tube or electric sewn tube) made of an iron alloy such as carbon steel or an aluminum alloy, and has a plurality of through holes 29, 29 at the front end. Such a steering column 6b and the screw ring 24 are integrally coupled and fixed when the screw ring 24 is injection-molded with 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 screw ring 24, 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 screw ring 24. At this time, a part of the molten resin enters the through holes 29 and 29 and solidifies in the through holes 29 and 29. As a result, a portion of the synthetic resin constituting the screw ring 24 that is present on the outer diameter side of the front end portion of the steering column 6b and a portion that is present on the inner diameter side are integrally coupled. At the same time, the screw ring 24 and the steering column 6b are firmly coupled. A male screw 30 that is a thread groove is formed on the outer peripheral surface of the screw ring 24. The tip surface of the screw ring 24 is a flat surface that exists in a direction perpendicular to the central axis. 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.

  In the inner peripheral surface of the rear end opening portion of the cylindrical portion 31 provided at the rear end portion of the main portion 23 of the housing 9b in order to couple and fix the front end portion of the steering column 6b to which the screw ring 24 as described above is coupled and fixed. A stepped large diameter portion 32 having an inner diameter larger than that of the front portion is formed. On the inner peripheral surface of the stepped large diameter portion 32, a female screw 33, which is another screw groove, is formed. Further, the rear end portion of the stepped large diameter portion 32 is a step surface 34 that exists in a direction perpendicular to the central axis of the cylindrical portion 31.

  The cylindrical portion 31 provided at the rear end portion of the main portion 23 of the housing 9b and the front end portion of the steering column 6b are coupled and fixed concentrically with each other via the screw ring 24. For this purpose, the male screw 30 on the outer peripheral surface of the screw ring 24 and the female screw 33 on the inner peripheral surface of the stepped large diameter portion 32 are screwed together and further tightened, and the tip surface of the screw ring 24 is moved to the step. Press strongly against surface 34. As a result, the screw ring 24 and the main portion 23 are firmly coupled and fixed, and the steering column 6b coupled and fixed to the screw ring 24 and the main portion 23 are firmly coupled and fixed. In order to facilitate the tightening of the screw ring 24 with a sufficiently large torque, a locking portion for locking the tightening tool can be formed on a part of the screw ring 24.

  As described above, the column unit for the electric power steering apparatus of this example wraps the front end portion of the iron-based alloy steering column 6b, in which the plurality of through holes 29, 29 are formed, in the screw ring 24 made of synthetic resin. Since the screw ring 24 and the main portion 23 are screwed together, the strength and rigidity of the coupling 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.

  In the case of this example, the steering column 6b and the housing 9b can be easily attached and detached. That is, the steering column 6b and the housing 9b can be attached to and detached from each other by rotating the steering column 6b and the housing 9b relative to each other to engage and disengage the male screw 30 and the female screw 33. And with this attachment and detachment, it is not necessary to damage any part. For this reason, it is possible to reduce the labor and cost of repairing the electric power steering apparatus.

[ First example of reference example ]
FIG. 5 shows a first example of a reference example relating to the present invention . In the case of this reference example , the screw ring 24a is a cap nut. That is, the screw ring 24a is a cap nut formed with an inward flange-shaped flange portion 35 at the rear end portion of the inner peripheral surface and a female screw 33a at the intermediate portion or the front end portion. Further, a stepped small diameter portion 36 having an outer diameter smaller than that of the front portion is formed on the outer peripheral surface of the rear end portion of the cylindrical portion 31a formed in the housing 9c. A male screw 30a, which is another screw groove, is formed on the outer peripheral surface of the stepped small diameter portion 36. Further, the rear end portion of the stepped small diameter portion 36 is a step surface 34a that exists in a direction perpendicular to the central axis of the cylindrical portion 31a. A large diameter portion 38 is provided on the front end portion of the steering column 6 c via an inclined step portion 37, and a plurality of through holes 29 are formed in the large diameter portion 38. And when the said screw ring 24a is injection-molded with a synthetic resin, the said large diameter part 38 is embedded in this screw ring 24a. Since the configuration and operation other than the point where the radial direction positions of the screw ring 24a and the cylindrical portion 31a are reversed are the same as those in the first example of the above-described embodiment, overlapping illustration and description are omitted. .

The present invention is not limited to a structure in which the housing and the screw ring are made of a synthetic resin, but can be implemented in a structure made of an aluminum alloy.
In addition, as a structure for embedding and supporting the front end portion of the steering column in the screw ring and improving the coupling strength between the steering column and the screw ring, structures as shown in FIGS. Among these, the structure of the 2nd example of the reference example shown in FIG. 6 makes the shape of the large diameter part 38a provided in the front-end part of the steering column 6d into the waveform regarding the circumferential direction. The structure of the third example of the reference example shown in FIG. 7 is such that embossed projections 39 are formed on the front end portion of the steering column 6e. Furthermore, the structure of the fourth example of the reference example shown in FIG. 8 is formed on the outer peripheral edge portion of the bent raising portion 40 formed by bending the front end edge portion of the steering column 6f outward in the radial direction and bending substantially at a right angle. A plurality of cutouts 41, 41 are formed. In the examples shown in FIGS. 6 to 8, the large-diameter portion 38a, the protrusions 39 and 39, and the bending raised portion 40 are embedded in a screw ring.

  In any structure, the coupling strength between the steering column and the screw ring can be improved, but the apparent thickness of the portion embedded in the screw ring at the front end of the steering column (related to the cross-sectional shape) 1/2) of the difference in diameter between the circumscribed circle and the inscribed circle is increased. As a result, the thickness dimension of the screw ring is partially reduced (at the top of the corrugation, the top of the protrusions 39 and 39, or the portion corresponding to the outer peripheral edge of the bent raised portion 40), and the thickness and weight are reduced. It may be difficult to achieve both durability and durability. 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, 9c Housing 10 Electric motor 11 Torsion bar 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 Main part 24, 24a Screw ring 25 Cover part 26a, 26b Rolling bearing 27 Worm wheel 28 Worm 29 Through hole 30, 30a Male thread 31, 31a Cylindrical part 32 Stepped large diameter part 33, 33a Female thread 34, 34a Stepped surface 35 Gutter part 36 Stepped small diameter part 37 Inclined step part 38 Outs 38a large diameter portion 39 projection 40 bent-up portion 41 cut

Claims (1)

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,
In the front end portion of the steering column, a through hole is formed to connect the inner and outer peripheral surfaces of the steering column, and the portion including the through hole is embedded inside the front end portion of the steering column. A screw ring having a male screw formed on the outer peripheral surface is cast or injection-molded, and this screw ring is screwed onto a female screw formed on the inner peripheral surface of the stepped large diameter portion formed on the inner peripheral surface of the rear end portion of the housing. A column unit for an electric power steering apparatus in which the housing and the steering column are coupled and fixed by further tightening.

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