JP2003261042A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device realizing a protection of an electric motor or the like from jumped water and flying stones at the time of traveling. <P>SOLUTION: The steering gear 11 is constituted by a steering gear case 21 for accommodating a rack/pinion mechanism and a power assist mechanism; an electric motor arranged at a front side of the steering gear case 21 and used for driving of the power assist mechanism; and a gear housing 25, made of aluminum alloy, accommodating a row of gear, i.e., a power transmission means. Bosses 31 are projectingly provided at a front side (in Figure, left side) and a vertical side of the electric motor 23 respectively and a protection cover 33, made of a steel plate, having a C shaped cross section is fixed to these bosses 31 by a bolt 35. In the case of this embodiment, the protection cover 33 extends to a right/left direction of a car body and covers a whole of the electric motor 23 and the gear housing 25. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device, and more particularly to a technique for protecting an electric motor or the like from splashing water and flying stones during traveling.

[0002]

2. Description of the Related Art In a steering system of an automobile, a so-called power steering device is widely used, which assists steering by using an external power source. Conventionally, a vane type hydraulic pump has been used as a power source for a power steering device, and many of these hydraulic pumps are driven by an engine. However, this type of power steering device has a large engine drive loss due to the constant drive of the hydraulic pump (several horsepower to 10 horsepower at maximum load), so it is recommended to be used in light vehicles such as small displacement vehicles. It was difficult and it was unavoidable that the running fuel consumption could not be neglected even in a car with a relatively large displacement.

To solve these problems, an electric power steering device using an electric motor as a power source (Electric Power Steering, hereinafter referred to as EPS)
Has been attracting attention in recent years. Since the EPS uses an on-vehicle battery as a power source of the electric motor, there is no direct engine drive loss, and since the electric motor is started only during steering assist, reduction in running fuel consumption is suppressed and electronic control is performed. It has features such as extremely easy operation.

On the other hand, as a steering gear for passenger cars, a rack and pinion type is now predominant because of its high rigidity and light weight. As the EPS for rack and pinion type steering gear, in addition to the column assist type in which an electric motor is arranged on the column side part to drive the steering shaft and the pinion itself, the rack shaft is driven by an electric ball screw mechanism. A ball screw type rack assist type is also used. In the ball screw type rack assist type EPS (hereinafter, simply referred to as a rack assist type EPS), the assist force does not act on the meshing surface between the pinion and the rack, so that the contact surface pressure between both members that causes wear and deformation. Becomes relatively small.

In the rack assist type EPS, the male screw groove of the ball screw shaft formed on the rack shaft and the female screw groove formed on the ball nut are engaged with each other through a plurality of circulating balls (steel balls). The rack shaft moves in the axial direction by rotationally driving the ball nut with an electric motor. Some electric motors are installed coaxially with the ball nut (outer circumference of the ball nut or rack shaft).
As described in Japanese Patent No. 939, Japanese Utility Model Publication No. 2-46455, etc., it is common to install the ball nut on a separate shaft and to connect the ball nut via a gear train or a belt.

[0006]

In a rack assist type EPS in which the electric motor and the ball nut are separate shafts, the electric motor is located under the vehicle body relatively close to the road surface.
Therefore, it is unavoidable that the electric motor, its electric harness, and the like are splashed with water when traveling in the rain or when passing through a water pool, or colliding with pebbles or the like that have been splashed up on the tire when traveling on a bad road.

As is well known, the output (torque generated) of the electric motor changes depending on its temperature. Therefore, when the electric motor is rapidly cooled by splashing water, the steering assist force of the EPS also changes abruptly. This has been a factor that hinders the smooth operation of the driver and deteriorates the steering feeling. Further, the collision of small stones or the like on the electric motor, the electric harness, the connector, etc. has been a factor that causes rusting due to the coating of the motor body or the plating being peeled off, or the disconnection or short circuit of the electric circuit. On the other hand, gear trains and belts, which are power transmission means between the electric motor and the power assist mechanism, are generally housed in a housing made of aluminum alloy or the like. There was also a risk of infiltration of muddy water.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric power steering device which protects an electric motor and the like from splashing water and flying stones during traveling.

[0009]

In order to solve the above-mentioned problems, in the invention of claim 1, a steering gear case having a built-in power assist mechanism and a drive shaft of the power assist mechanism which is arranged separately from the steering gear case are provided. In a rack assist type electric power steering apparatus having an electric motor provided for the electric motor and a power transmission means interposed between the electric motor and the power assist mechanism, a protective cover for covering the electric motor is provided. Suggest things.

Further, the invention of claim 2 proposes the electric power steering device of claim 1 in which the housing accommodating the power transmission means is covered with a protective cover which is integral with or separate from the protective cover. .

According to the first and second aspects of the invention, the presence of the protective cover prevents splashing of water or collision of flying stones on the housing of the electric motor or the power transmission means.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of an electric power steering device (EPS) according to an embodiment. A member indicated by reference numeral 1 in the figure is a steering column, and rotatably supports the upper steering shaft 3. A steering wheel 5 is attached to an upper end of the upper steering shaft 3, and a lower steering shaft 9 is connected to a lower end of the upper steering shaft 3 via a universal joint 7. The lower steering shaft 9 has a steering gear 1 at its lower end.
1 is connected. In FIG. 1, reference numeral 13 indicates a tie rod connected to the left and right ends of the steering gear 11.

FIG. 2 shows a side view of the steering gear according to the embodiment. As shown in the figure, the steering gear 11 includes a steering gear case 21 that houses a rack and pinion mechanism, a power assist mechanism, and the like, and an electric motor 23 that is disposed in front of the steering gear case 21 and is used to drive the power assist mechanism. And a gear housing 25 made of an aluminum alloy that accommodates a gear train as a power transmission means.

In front of the electric motor 23 (left in FIG. 2)
Bosses 31 are provided on the upper and lower sides, respectively, and a protective cover 33 made of a steel plate and having a C-shaped cross section is fixed to the bosses 31 with bolts 35. In the case of the present embodiment, the protective cover 33 extends in the left-right direction of the vehicle body and covers the electric motor 23 and the front portion of the gear housing 25.

In the present embodiment, by adopting such a configuration, splashing water is not applied to the electric motor 23 even when traveling in the rain or when passing through a water pool, and due to a torque fluctuation of the electric motor 23 due to abrupt cooling. The problem that the EPS steering assist force fluctuates no longer occurs. Also,
Electric motor 23, electric harness and connector (both
In addition to (not shown), the gear housing 25 is prevented from colliding with pebbles and the like that are thrown up by the tire during traveling on a bad road, and the electric motor 23 and the gear housing 25 are damaged and the electric circuit is disconnected or short-circuited. And so on.

The description of the specific embodiment is completed above.
Aspects of the present invention are not limited to the above embodiment.
For example, in the above-described embodiment, one protective cover covers the electric motor and the gear housing, but a protective cover that covers only the electric motor may be adopted, or the electric motor and the gear housing may each have a protective cover. May be provided. Further, as the protective cover, a synthetic resin injection molded product or an aluminum alloy die cast molded product may be adopted,
The shape and the mounting method to the electric motor etc. are not limited to the examples in the above embodiment, and may be appropriately changed depending on the design or specification requirements as long as they do not depart from the gist of the present invention. Is.

[0017]

As described above, according to the electric power steering apparatus of the present invention, the rack assist type electric power steering apparatus is provided with the protective cover for covering the housing of the electric motor and the power transmission means. , Splashing water on the housing of the electric motor or power transmission means, and no collision of flying stones,
The deterioration of the steering feeling of the EPS due to the unnecessary torque fluctuation of the electric motor is eliminated, and the reliability of the electric power steering device is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a steering device according to an embodiment.

FIG. 2 is a side view of the steering gear according to the embodiment.

[Explanation of symbols]

11 ... Steering gear 23 ... Electric motor 25 ... Gear housing 33 ... Protective cover

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Fukuda             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. (72) Inventor Osamu Saito             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. (72) Inventor Jun Okada             Gunma Prefecture Maebashi City 1-8-1 Sojamachi Japan             Within Seiko Co., Ltd. F-term (reference) 3D033 CA02

Claims (2)

[Claims] 1. A steering gear case having a built-in power assist mechanism, an electric motor arranged separately from the steering gear case and used for driving the power assist mechanism, and the electric motor and the power assist mechanism. A rack assist type electric power steering device having power transmission means interposed between the electric power steering device and the electric power steering device, comprising a protective cover for covering the electric motor. 2. The electric power steering apparatus according to claim 1, wherein a housing accommodating the power transmission means is covered with a protective cover which is integral with or separate from the protective cover.