JP2009012555A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device, capable of avoiding an increase in cost and weight, while achieving protection of a driver. <P>SOLUTION: A gear box housing 101 including reducer gears 108 and 107 connected to a motor 109 are disposed between two universal joints 20 and 22 so as to secure a wide space around the knees of the driver. The degree of driving position freedom is thus increased, and a long collapse stroke is secured to achieve protection of the driver. Using a saved space, a storage part or an air discharge port for air-conditioning can be provided to improve amenity of an occupant. Unlike a rack assist type or a pinion assist type, the gear box housing 101 is provided inside a dust panel DP, that is inside the cabin, only simplified dust-proofing/water-proofing measures are necessary, thereby cost and weight can be decreased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering device used in a steering system that constitutes a steering device for an automobile or the like.

  In a general vehicle steering system, when the steering wheel and the steering device are arranged at the optimum positions, there are many cases where they interfere with various parts existing between them, and therefore it is not possible to connect them with a straight steering shaft. Usually difficult. Therefore, by providing two universal joints in the steering system, the degree of freedom in the layout of the steering system is improved.

On the other hand, in recent years, from the viewpoint of energy saving and the like, an increasing number of vehicles adopt an electric power steering device from a hydraulic power steering device. A column assist type in which the motor and the reduction gear are in the column part, a pinion assist type in which the motor and the reduction gear are in the pinion gear part as shown in Patent Document 2, and a motor and a reduction gear in the rack gear as shown in Patent Document 3, respectively. It is classified into the rack assist type in the section.
JP 2007-112240 A JP 2002-234449 A JP 2001-301629 A

  Here, in the case of the column assist type, since the gear box housing having the motor and the reduction gear is in the column portion, the motor interferes with the driver's knee or protects the driver at the time of the secondary collision depending on the vehicle layout. There is a risk that a sufficient collapse stroke cannot be secured. On the other hand, in the rack assist type and pinion assist type, since the motor, reduction gear, torque sensor, etc. are located outside the vehicle compartment, it is necessary to take effective dustproof and waterproof measures compared to the case where they are arranged in the vehicle interior. And tend to increase weight.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric power steering device capable of avoiding an increase in cost and weight while protecting a driver.

An electric power steering apparatus according to the present invention is an electric power steering apparatus used in a vehicle including a steering system having at least two universal joints.
A gear box housing containing a reduction gear connected to a motor is disposed between the two universal joints.

  According to the present invention, since a gear box housing containing a reduction gear connected to a motor is disposed between the two universal joints, a wide space around the driver's knees can be secured. The degree of freedom increases and the collapse stroke can be secured for a long time, thus protecting the driver. In addition, a surplus space can be used to provide a storage unit, an air-conditioner exhaust port, and the like, and passenger comfort can be improved. On the other hand, unlike the rack assist type and pinion assist type, by providing the gear box housing in the vehicle interior, it is sufficient to provide simplified dustproof and waterproof measures, and cost and weight can be reduced.

  The gear box housing is preferably attached to a dash panel that separates the interior of the vehicle from the exterior of the vehicle. By mounting the electric power steering device of the present invention on a dash panel that has conventionally existed as a vehicle component, it is possible to implement the conventional vehicle component without requiring a dedicated component or the like.

  It is preferable that an ECU and a motor are integrally assembled with the gear box housing.

  Of the two universal joints, the upper universal joint is preferably the tilt rotation center.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a layout diagram of a steering system including an electric power steering apparatus 100 according to the present embodiment. In FIG. 1, an upper shaft 16 having a steering wheel (not shown) attached to the upper end is rotatably supported by a bearing unit BU including an upper bracket 14 and a bearing (not shown) with respect to a vehicle body VB. The upper bracket 14 is easily deformed when receiving a large load in the axial direction during a secondary collision or the like, and has a so-called collapsible structure.

  The lower end of the upper shaft 16 is splined to the upper end of the lower shaft 18, thereby rotating integrally but being relatively displaceable in the axial direction. The lower shaft 18 is connected to the input shaft 102 of the electric power steering apparatus 100 attached to the dash panel DP of the vehicle via the universal joint 20.

  On the other hand, the output shaft 103 of the electric power steering apparatus 100 passes through the opening AP of the dash panel DP and is connected to the upper end of the pinion shaft 24 via the universal joint 22. The pinion formed on the pinion shaft 24 meshes with rack teeth of a rack shaft (not shown). Both ends of the rack shaft are connected to a steering mechanism for steering a wheel (not shown) via tie rods.

  FIG. 2 is a cross-sectional view of the electric power steering apparatus 100 used in the present embodiment. A gear box housing 101 in which an ECU (FIG. 1) and a motor 109 are integrally incorporated is formed of aluminum or aluminum alloy, magnesium or magnesium alloy including a main body 101b and a lid member 101a, and a bolt is attached to the dash panel DP. It has been stopped. An input shaft 102 and an output shaft 103 are disposed in the gear box housing 101. The input shaft 102 is rotatably supported with respect to the gear box housing 101 by a bearing (not shown). The hollow output shaft 103 is rotatably supported with respect to the gear box housing 101 by bearings 104 and 110. In FIG. 2, a torsion bar 105 connected by pressing the right end into the input shaft 102 and pin-connecting the left end to the output shaft 103 extends through the output shaft 103.

  A detection device, that is, a torque sensor 106 for detecting a steering torque based on the torsion bar 105 being twisted in proportion to the received torque is provided at a position facing the outer periphery near the right end in FIG. This torque sensor 106 is a rotary non-contact torque sensor, and detects relative angular displacement between the input shaft 102 and the output shaft 103 based on torsion of the torsion bar 105 by a coil as a change in impedance in a predetermined magnetic circuit. As an electrical signal, it is output to an ECU (see FIG. 1) assembled to the gear box housing 101.

  A worm wheel 107 is disposed between the bearings 104 and 110 at the center of the output shaft 103. The worm wheel 107 includes a cored bar 107a attached so as to rotate integrally with the output shaft 103 by press fitting or the like, and a resin tooth part 107b formed by insert molding on the outer periphery thereof. The tooth portion 107 b of the worm wheel 107 meshes with a worm 108 that is formed integrally with a rotation shaft of a motor 109 attached to the gear box housing 101. The worm wheel 107 and the worm 108 constitute a reduction gear.

  Next, the operation of the present embodiment will be described. If the vehicle is in a straight traveling state and no steering force is input to the input shaft 102 from a steering wheel (not shown), the torque sensor 106 does not generate an output signal, and therefore the motor 109 does not generate an auxiliary steering force.

  On the other hand, when the driver operates a steering wheel (not shown) when the vehicle is about to turn a curve, the rotational force is transmitted to the input shaft 102 via the upper shaft 16, the lower shaft 18, and the universal joint 20. Therefore, the torsion bar 105 is twisted according to the rotational force, and relative rotation occurs between the input shaft 102 and the output shaft 103. The torque sensor 106 outputs a torque signal according to the direction and amount of this relative rotation. The ECU supplies a predetermined three-phase motor current to the motor 109 based on this torque signal and a vehicle speed signal from a sensor (not shown) based on a preset control map. Generate power. The torque generated by the motor 109 is decelerated by the reduction gears (108, 107) and transmitted to the output shaft 103, and is transmitted to the pinion shaft 24 via the universal joint 22, and assists the movement of the rack shaft meshing with the pinion shaft 24. To do. As a result, the steering mechanism is operated via the tie rod, and a wheel (not shown) can be steered.

  At the time of the secondary collision, the driver's body collides with a steering wheel (not shown), and the upper bracket 14 formed by pressing the plate material is easily deformed, so that the upper shaft 16 moves toward the lower shaft 18. Since displacement in a nested manner is allowed, impact energy can be absorbed using an energy absorption mechanism (not shown).

  According to the present embodiment, the gear box housing 101 containing the reduction gears (108, 107) connected to the motor 109 is disposed between the two universal joints 20, 22, so As a result, it is possible to secure a large space for the driver, so that the degree of freedom of the driving position is increased and the collapse stroke can be secured for a long time, thereby protecting the driver. In addition, a surplus space can be used to provide a storage unit, an air-conditioner exhaust port, and the like, and passenger comfort can be improved. On the other hand, unlike the rack assist type and the pinion assist type, by providing the gear box housing 101 inside the dash panel DP, that is, in the vehicle compartment, it is sufficient to take simplified dustproof and waterproof measures, and cost and weight can be reduced.

  FIG. 3 is a perspective view of a steering system according to a modification of the present embodiment. By devising the upper bracket (not shown), the upper shaft 16 can be tilted. In this case, as shown in FIG. 3, the upper shaft 16 and the lower shaft 18 can be swung around the universal joint 20 on the upper side.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

1 is a layout diagram of a steering system including an electric power steering apparatus 100 according to the present embodiment. 1 is a cross-sectional view of an electric power steering device 100 used in the present embodiment. It is a perspective view of the steering system concerning the modification of this Embodiment.

Explanation of symbols

14 Upper bracket 16 Upper shaft 18 Lower shaft 20 Universal joint 22 Universal joint 24 Pinion shaft 100 Electric power steering device 101 Gear box housing 101a Lid member 101b Main body 102 Input shaft 103 Output shaft 104, 110 Bearing 105 Torsion bar 106 Torque sensor 107 Worm wheel 107a Metal core 107b Tooth part 108 Worm 109 Motor BU Bearing unit DP Dash panel VB Car body

Claims (4)

In an electric power steering apparatus used in a vehicle having a steering system having at least two universal joints,
An electric power steering apparatus characterized in that a gear box housing containing a reduction gear connected to a motor is disposed between the two universal joints.   2. The electric power steering apparatus according to claim 1, wherein the gear box housing is attached to a dash panel that separates the interior of the vehicle from the interior of the vehicle.   3. The electric power steering apparatus according to claim 1, wherein an ECU and a motor are integrally assembled with the gear box housing.   The electric power steering apparatus according to any one of claims 1 to 3, wherein an upper side universal joint of the two universal joints is used as a tilt rotation center.

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