JP2531067Y2 - Electric steering device for vehicles - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] <Industrial application field> The present invention relates to a vehicle steering system, and in particular, an electric motor controlled in response to operation of a steering wheel, and a rotational motion of the electric motor. And a so-called ball screw mechanism for converting a steering motion into a linear motion.

<Prior Art> In this type of vehicle steering system, for example, as disclosed in Japanese Patent Application No. 63-77139 by the present applicant,
Assuming that the rotor shaft of the electric motor is directly rotatably supported on the steering rod over its entire length, a large sliding resistance necessarily occurs between the inner peripheral surface of the rotor shaft and the outer peripheral surface of the steering rod. This may hinder the smooth rotation operation of the electric motor and the smooth steering operation of the steering rod.In addition, high machining accuracy is required for the inner peripheral surface of the rotor shaft and the outer peripheral surface of the steering rod. There are inconveniences such as an increase in price. In order to rotatably support the rotor shaft of the electric motor and slidably support the steering rod with respect to the casing fixed to the vehicle body side, a separate support structure is provided for the rotor shaft and the steering rod. This is necessary, and there is a problem that the entire device becomes longer in the axial direction.

<Problems to be solved by the present invention> The present invention has been devised to solve such problems, and its main purpose is to increase the size of the rotor shaft of the electric motor without increasing the size of the device. It is an object of the present invention to provide an electric steering apparatus for a vehicle, which can greatly reduce the rotational resistance and sliding resistance generated between the steering rod and the steering rod, and can be manufactured relatively easily and at low cost.

[Constitution of the Invention] <Means for Solving the Problems> Such an object is achieved by connecting both ends of a hollow rotor shaft having a ball nut integrally connected to one end thereof to a rolling bearing on an inner surface of a casing supported by a vehicle body. Electric steering device for a vehicle, comprising: an electric motor rotatably supported by the rotor shaft; and a steering rod having a ball screw portion that is inserted and supported by the rotor shaft so as to be movable in the axial direction and that is screwed into the ball nut. Wherein the steering rod is inserted through the hollow rotor shaft in a non-contact manner, and a steel ball of the ball nut and an inner peripheral surface of a portion supported by the casing at the other end of the rotor shaft. The present invention is attained by providing a vehicle electric steering system characterized by being supported by a resin bush provided on a vehicle.

<Operation> In this way, since the steering rod and the rotor shaft come into contact with each other only by the portion of the steel ball of the ball nut and the resin bush, the rotation and sliding resistance between the steering rod and the rotor shaft are greatly reduced. Since it can be reduced, the operation of the electric motor and the steering rod can be smoothed. Moreover, since the ball nut portion and the resin bush portion are matched with the portion supported by the rotor shaft casing, the steering rod is supported without increasing the axial dimension. The support rigidity of the steering rod can be increased without complicating the structure.

<Embodiments> The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 schematically shows the entire front and rear wheel steering device of a vehicle to which the present invention is applied. In the figure, a steering shaft 2 having a steering wheel 1 fixed to one end is shown.
Is mechanically connected to the steering rod 4 of the front wheel steering device 3.

Both ends of the steering rod 4 extending in the vehicle width direction are connected to a tie rod 7 for each knuckle arm 6 supporting the left and right front wheels 5.
Respectively. In a rear wheel steering device 8 arranged at the rear of the vehicle, a steering rod 9 extending in the vehicle width direction is driven by an electric motor 10. Both ends of the steering rod 9 are connected via tie rods 13 to a knuckle arm 12 that supports the rear wheel 11, similarly to the steering rod 4 for the front wheel.

In order to detect the position of the steering rods 4.9 and measure the amount of steering of the wheels 5.11, for example, each of the steering devices 3.8 is provided with a steering angle sensor 14.15 using a differential transformer, for example. Have been. Further, a steering angle sensor 16 composed of, for example, a pulse encoder is attached to the steering shaft 2 in order to detect an operation amount of the steering wheel 1,
In order to detect the rotation amount and direction of the electric motor 10, a steering angle sensor 17 also including a pulse encoder is attached to the rear wheel steering device 8. Further, a vehicle speed sensor 18 is disposed on each of the wheels 5 and 11. These sensors 14 to 18 are electrically connected to a computer unit 19 that drives and controls the electric motor 10.

When the driver operates the steering wheel 1, the steering rod 4 is mechanically driven to steer the front wheel 5, and at the same time, the amount of operation of the steering wheel 1 and the amount of movement of the steering rod 4 are transmitted via the steering angle sensors 16 and 14. Are input to the computer unit 19 respectively. The computer unit 19 appropriately determines the amount of steering of the rear wheel 11 based on the information on the steering of the front wheel 5 and the vehicle speed input from the vehicle speed sensor 18 and drives the electric motor 10 to rotate the rear wheel 11. Steer. The amount and direction of rotation of the electric motor 10 and the steering rod 9
The movement amount of the rear wheel 11, that is, the actual steering amount of the rear wheel 11, is
The computer unit 19 is input to each of the computer units 19 through 17, and the computer unit 19 further optimally controls the steering angle of the rear wheel 11 based on these inputs.

FIG. 2 shows the rear wheel steering device 8 to which the present invention is applied in detail. The rear wheel steering device 8 includes a casing 21 fixed to the vehicle body, in which a steering rod 9 penetrates in a vehicle width direction, that is, a left-right direction in the drawing, and ball joints 22
The tie rods 13 are respectively connected via a and 22b. The electric motor 10 has a rotor shaft 23 rotatably supported on the steering rod 9 coaxially and relatively rotatably, and a rotor 24 formed by winding a coil on the rotor shaft 23 and an inner peripheral surface of a central portion of the casing 21. Stator 25 consisting of fixed permanent magnets
Are provided.

One end 23a of the rotor shaft 23 is rotatably supported by the casing 21 via a ball bearing 27, and the other end 23b is connected to a ball screw mechanism described later. Also ball bearing
One end of a rotor shaft 23 supported on the casing 21 via 27
The steering rod 9 is inserted and supported on the inner peripheral surface of the reference numeral 23a via a bush 26 as a slide bearing.

4, the bush 26 is formed of a thin cylinder 57 made of metal such as aluminum, and a liner 58 made of synthetic resin is adhered to the inner peripheral surface thereof over the entire length. Therefore, the sliding friction generated between the rotor shaft 23 and the steering rod 9 when the rotor shaft 23 rotates, and the generation of sliding noise due to the sliding friction can be greatly reduced.

In this manner, the steering rod 9 does not directly contact the entire inner surface of the hollow of the rotor shaft 23 over the entire length thereof,
Is supported via the bush 26 at one end thereof, so that the sliding contact area between the inner peripheral surface of the rotor shaft 23 and the outer peripheral surface of the steering rod 9 can be reduced, and the rotational resistance of the rotor shaft 23 can be greatly reduced. As a result, the smooth rotation of the electric motor and the improvement of the steering performance can be achieved. Further, since the bush 26 exhibits a sealing effect of blocking the inside of the rotor shaft 23 from the outside air, the durability of the ball screw mechanism mounted on the other end 23b of the rotor shaft is improved. Further, since the steering rod 9 is supported by the casing 21 via the bush 26 and the ball bearing 27 at one end of the rotor shaft 23, there is no need to separately provide a bearing for supporting only the steering rod 9; The entire device can be shortened in the vehicle width direction, that is, in the axial direction of the steering rod 9.

To the other end 23b of the rotor shaft 23, a cylindrical ball nut 30 is connected by a bolt 31 so as to rotate integrally with the rotor shaft 23. The ball nut 30 has a single internal thread groove 32 formed in the inner peripheral surface of the central portion thereof, and a reduced diameter portion 33 formed at an end opposite to a portion connected to the rotor shaft 23.
The inner cylindrical part of the casing 21 is
It is rotatably supported by 28. The steering rod 9 is supported via a so-called ball screw mechanism in which a large number of steel balls 36 are arranged between a male screw groove 35 and a female screw groove 32 formed on the outer peripheral surface of the right half of the steering rod 9. Accordingly, when the electric motor 10 is driven by the computer unit 19 to rotate the rotor shaft 23, the rotation is reduced via the ball nut 30 and converted to linear motion and transmitted to the steering rod 9. Thereby, the steering rod 9 is linearly driven in the left-right direction, and the rear wheel 11 is steered.

A plurality of permanent magnets 38 are fixed to the outer periphery of the cylindrical member 37 integrally connected to the ball nut 30 at regular intervals in the circumferential direction. Correspondingly, the casing 21
The pulse encoder main body 39 constituting the steering angle sensor 17 is attached, and the magnetic sensitive section 40 is located at a position protruding into the casing 21 and close to the magnet 38. As a result, when the electric motor 10 is driven and the ball nut 30 rotates, the magnetic sensing unit 40 detects a magnetic field change due to the rotation of the permanent magnet 38 and outputs a signal, and based on the signal, the computer unit 19 The rotation amount and the rotation direction of the rear wheel 11, that is, the turning direction and the turning angle of the rear wheel 11 are determined.

A ball joint 22a is attached to the end 9a of the steering rod 9 on the side opposite to the side where the male thread groove 35 is provided, and the detent member 41 is held between the ball joint 22a. The detent member 41 is stopped and prevented from coming off by a set screw 42 and is integrally connected to the steering rod 9. FIG. 2 shows the rear wheel rolling with a partial change of direction as shown by the line II-II in FIG. 3 in order to make it easier to understand the mounting structure of the detent member 41 and the steering angle sensor 15. 2 shows a cross section of the rudder device 8.

As shown in FIG. 3, the detent member 41 is
An arm 43 extends radially from the steering rod 9 and a detent shaft 44 extending parallel to the steering rod 9 from its tip. The detent shaft 44 is inserted into a slightly larger diameter guide hole 45 formed in the casing 21. A sleeve 46 made of a synthetic resin is attached to the enlarged inlet portion 45a of the guide hole 45, and functions as a slide bearing that guides the detent shaft 44 that moves in the axial direction integrally with the steering rod 9. . Accordingly, it is possible to eliminate the play between the anti-rotation shaft 44 and the rotation of the anti-rotation shaft 44 when driving the steering rod 9 and to prevent the generation of abnormal noise. Further, as the sleeve 46, a metal cylinder having a synthetic resin layer adhered to each of the inner and outer peripheral surfaces thereof can be used.

The sleeve 46 is provided with two holes 47 and 48 penetrating the center thereof in the lateral direction at symmetrical positions. On the other hand, a lateral hole 49 having the same diameter as one of the through holes 47 is provided in the casing 21 along a tangential direction of the steering rod 9 orthogonal to the arm 43 so as to open to the guide hole entrance 45a. . Further, the sleeve 46 is arranged so that the through hole 47 coincides with the horizontal hole 49 of the casing 21.

In the lateral hole 49, a pressing member 50 having a curved end surface that fits the outer peripheral surface of the rotation preventing shaft 44 is slidably disposed. The pressing member 50 is constantly resiliently biased rightward in the drawing by a coil spring 51 disposed in the horizontal hole 49, and the end surface is brought into contact with the outer peripheral surface of the detent shaft 44 to thereby rotate the detent shaft 44. It is biased in the tangential direction of the steering rod 9. The pressing member 50 is formed of various well-known materials or is formed by sticking a synthetic resin to an end face so as to reduce sliding friction with the rotation preventing shaft 44.

The urging force of the coil spring 51 is adjusted by a set bolt 52 screwed to the casing 21. Further, as shown, since the pressing member 50 is in contact with the outer peripheral surface of the detent shaft 44 through the through hole 47 from the horizontal hole 49, the entrance portion of the guide hole can be used without using a separate means. The sleeve 46 can be retained at a predetermined position of 45a by preventing it from falling off.

A steering angle sensor 15 is mounted on the outer peripheral side of the casing 21. As described above, the steering angle sensor 15 including the differential transformer has a coil and a movable core therein. The sensor shaft 53 that protrudes freely from the tip of the steering angle sensor 15 is always elastically urged outward by a built-in spring.
The bottom surface 55 of the axial groove 54 recessed in the outer peripheral surface of 44 is in contact with the other through hole 48 of the sleeve 46.

As described above, the urging force of the coil spring 51 via the pressing member 50 and the urging force of the built-in spring of the steering angle sensor 15 via the sensor shaft 53 are applied to the detent shaft 44 in the tangential direction of the steering rod 9. Act in opposite directions along
In addition, since the operating position of the urging force and the axial center position of the steering rod 9 are largely separated by the arm 43, even if these urging forces are set small, a relatively large force acts in the rotation direction of the steering rod 9. Can be done. This allows
Sliding friction between the pressing member 50 and the outer peripheral surface of the rotation preventing shaft 44 can be reduced, and the steering rod 9 can be surely prevented from rotating.

As shown in FIG. 2, the axial groove 54 formed in the detent shaft 44 has a bottom surface 55 such that its depth changes at a constant rate in the axial direction, that is, the moving direction of the steering rod 9. Is inclined. Therefore, the stroke of the sensor shaft 53 that always contacts the bottom surface 55 changes at the same ratio following the depth of the groove 54 when the steering rod 9, that is, the detent shaft 44 moves in the axial direction. Based on this displacement, the steering angle sensor 15 outputs a signal, and the computer unit 19 that has received this signal detects the displacement of the steering rod 9 in the axial direction, and determines the actual steering amount and the steering direction of the wheel 11. to decide.

The steering angle sensor 14 of the front wheel steering device 3 shown in FIG.
It has the same configuration as the steering angle sensor 15 of the rear wheel steering device 8. That is, an axial groove 56 having a bottom surface inclined at a fixed ratio is formed on the outer peripheral surface of the steering rod 4, and the sensor shaft urged outward of the steering angle sensor 14 is provided in the groove 56.
Is in contact with the bottom surface. However, since the front wheel 5 usually has a much larger steering range than the rear wheel 11, there is a considerable difference in the movement range of the two steering rods 4. Therefore, the groove 56 of the front wheel steering rod 4 and the groove 54 of the rear wheel steering rod 9 have the same maximum depth, and their axial lengths are proportional to the maximum strokes of the respective steering rods 4 and 10. In this case, a common differential transformer type stroke sensor can be used for each of the steering angle sensors 14 and 15.

As shown in FIG. 2, the rear wheel steering device 8 includes a fail-safe mechanism 61 for returning the steering rod 9 to the neutral position. In the fail-safe mechanism 61, a return spring 62 that has been compressed in advance is mounted on the outer periphery of a cylindrical support member 65 via a pair of sheet members 63 and 64 disposed at both ends thereof. The support member 65 is integrally connected to the steering rod 9 with one side, that is, a disk-shaped mounting portion 66 formed at the right end in the drawing, prevented from falling off by the ball joint 22b.

As described above, since the outer diameter of the bearing 33 that supports the ball nut 30 is reduced, the cylindrical portion of the support member 65 on which the return spring 62 is mounted becomes the steering rod 9 shown in FIG.
In the neutral position, the ball nut 30 is partially overlapped in the axial direction to the vicinity of the reduced diameter portion 32 in the annular space between the inner cylindrical portion 28 and the outer cylindrical portion 29 of the casing 21. Placed in Further, since the diameter of the return spring 62 is relatively large, a large urging force can be obtained even if the length is relatively short. This makes it possible to shorten the rear wheel steering device 8 in the vehicle width direction without increasing the outer diameter.

The sheet members 63 and 64 are slidably fitted on the outer peripheral surface of the support member 65, and a stopper protruded from the inner end of the support member 65.
The movement of the support member 65 is restricted by a stopper 68 formed of a retaining ring screwed to the outer end of the support member 65. Furthermore,
The movement of the sheet members 63 and 64 is restricted by stoppers 69 and 70 provided on the inner periphery of the outer cylindrical portion 29 of the casing 21, respectively. The contractable limit of the return spring 62 is determined by the axial distance between the two seat members 63 and 64 at the neutral position in FIG.

Since the support member 65 has high workability, sufficient accuracy can be easily secured without requiring a separate adjustment mechanism as compared with a case where a stopper is provided directly on the steering rod 9 and the return spring 62 is mounted. it can. Also, sheet members
Sheet-like elastic members 71 and 72 are adhered to both end surfaces of 63 and 64, respectively.
It is designed to alleviate the collision when colliding with ~ 70 and to prevent the hitting sound.

When the steering rod 9 moves rightward in the drawing, the left seat member 63 moves rightward together with the steering rod 9 by the stopper 67 of the support member 65, but the right seat member 64 is locked by the stopper 70 of the casing 21. Is done. Therefore, the return spring 62 is compressed, and an urging force for returning the steering rod 9 to the left is generated. Conversely, when the steering rod 9 moves to the left in the drawing, the right seat member 64 moves to the left together with the steering rod 9 by the stopper 68 outside the support member 65, but the left seat member 63 moves to the casing 21. Is locked by the stopper 69. Therefore, the biasing force of the return spring 62 acts on the steering rod 9 to the right. In this way, even if the steering rod 9 is moved in either the left or right direction, the return force from the return spring 62 acts on the steering rod 9 toward its neutral position.

[Effects of the Invention] As described above, according to the present invention, the steel ball of the ball nut is inserted by supporting the steering rod through the resin bush to the other end of the rotor shaft having one end forming the ball nut of the ball screw mechanism. Since the steering rod and the rotor shaft can be brought into contact with each other only by the portion of the steering motor and the resin bush, the rotation and sliding resistance between the steering rod and the rotor shaft are greatly reduced, and the operation of the electric motor and the steering rod is reduced. The performance of the turning operation can be improved by smoothing. At the same time, since the supporting portions of the steering rod are matched with both ends of the rotor shaft supported on the casing via ball bearings, the rigidity of the steering rod is secured and the axial dimension of the entire device is reduced. Dimensions can improve space efficiency. In addition, since the inner peripheral surface of the rotor shaft has a relatively low machining accuracy, the manufacturing is easy and the cost can be reduced. Further, since the outside air can be shut off by the sealing effect of the bush, the durability of the ball screw mechanism can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an entire steering mechanism of a vehicle to which the present invention is applied. FIG. 2 is a longitudinal sectional view showing a rear wheel steering device to which the present invention is applied. FIG. 3 is a sectional view taken along the line III-III in FIG. FIG. 4 is a sectional view showing the bush used in the present invention. 1 ... steering wheel, 2 ... steering shaft, 3 ... front wheel steering device, 4 ... steering rod, 5 ...
Front wheel, 6 ... Knuckle arm, 7 ... Tie rod, 8 ...
… Rear wheel steering device, 9 …… Steering rod, 9a ・ 9b …… End,
10: Electric motor, 11: Rear wheel, 12: Knuckle arm, 13: Tie rod, 14 to 17: Steering angle sensor, 18 ...
Vehicle speed sensor, 19 Computer unit, 21 Casing, 22a / 22b Ball joint, 23 Rotor shaft, 23a / 23b End, 24 Rotor, 25 Stator, 26 Bush , 27 …… Ball bearing, 28 …… Inner cylinder part, 29
... outer cylinder, 30 ... ball nut, 31 ... bolt, 32 ...
... annular groove, 33 ... diameter reduction part, 34 ... ball bearing, 35 ... thread groove, 36 ... steel ball, 37 ... support member, 38 ... permanent magnet, 39
…… Encoder body, 40 …… Magnetic sensing part, 41 …… Detent member, 42 …… Set screw, 43 …… Arm, 44 …… Detent shaft, 45 …… Guide hole, 46 …… Sleeve, 47 ・48
... through-hole, 49 ... horizontal hole, 50 ... pressing member, 51 ... coil spring, 52 ... set bolt, 53 ... sensor shaft,
54 …… groove, 55 …… bottom, 56 …… groove, 57 …… thin cylinder, 58
Liner, 61 Fail-safe mechanism, 62 Return spring, 63/64 Seat member, 65 Support member, 66 Mounting part, 67-70 Stopper, 71/72 Elasticity Element,

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-172057 (JP, A) JP-A 63-104720 (JP, U) JP-A 61-186825 (JP, U) JP-A 60-104 54839 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. An electric motor having both ends of a hollow rotor shaft having one end integrally connected to a ball nut and rotatably supported via rolling bearings on the inner surface of a casing supported by a vehicle body, and an axial motor. A steering rod having a ball screw portion movably inserted into and supported by the rotor shaft and having a ball screw portion screwed into the ball nut, wherein the steering rod is attached to the hollow rotor shaft. It is inserted in a non-contact manner, and is supported by a steel ball of the ball nut and a resin bush provided on the inner peripheral surface of a portion supported by the casing at the other end of the rotor shaft. Electric steering device for vehicles.