JPH0218161A - Electrically driven power steering device - Google Patents

Abstract

PURPOSE:To contrive to make a whole assembly small in size and light in weight by enabling an upper bearing and a small gear to be closely arranged in the same plane wherein the upper bearing is one of the upper and a lower bearing pivotally supporting a shaft to which the power of an electric motor is transmitted while being reduced in speed via a speed reduction mechanism, and the small gear is located on the driving side of the speed reduction mechanism. CONSTITUTION:When an electric motor is rotated in the title device based on the output from a torque detecting means 1 composed of magnetic drums 11 and 11 and of a magnetic sensor 12, a lower shaft 5 is rotated via a small gear 4 provided for the end section of the armature shaft 3 of the electric motor, a large gear 7 coupled with a play with the lower shaft 5 and an electromagnetic tooth clutch 8. In this case, an upper bearing 31 out of the upper and a lower bearing 31 and 32 which pivotally support the lower shaft 5 is inserted into a housing 33, and the location of the upper bearing 31 is set up at a position shifted in such a way that the axial lines of the upper bearing 31 and the small gear 4 are not intersected with each other in a plane surface passing through the axial line of the small gear 4. By this constitution, the length of the device can thereby be shortened in the axial direction by the part of the width of the upper bearing 31.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering system for an automobile, and more particularly to the structure of an electric power steering system that assists steering with an electric motor.

[Conventional technology]

In the conventional device, two bearings are arranged above and below the large gear of the reducer as described in Utility Model Application No. 137339/1980, but since the upper bearing is arranged above the small gear, the shaft This has the disadvantage that the length in the direction increases, making the electric power steering device larger.

Electric power steering devices are installed in the engine compartment or passenger compartment of a car, but engine compartments have recently become front-wheel drive (front engine, front drive).
With the spread of technology, density has increased, making it difficult to secure space for new equipment.

Particularly when the device is long in the axial direction, it comes into contact with other devices.

Additionally, when installed inside a vehicle, there are restrictions such as the large size of the electric power steering device causing it to hit the driver's feet.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into consideration the miniaturization of the electric power steering device, making it difficult to install it in a car.

In addition, in order to ensure the safety of electric power steering, an electromagnetic tooth clutch is provided.

When the teeth formed on the sides of the ring and rotor are attracted to each other b1, it is difficult for all the teeth to mesh due to the low precision of the teeth or uneven electromagnetic force, and some of the teeth may not absorb the torque. The transmission torque may be reduced.

Another problem is that conventional torque detection means add a mechanical stopper to the upper limit of torque detection, but this stopper requires high precision in manufacturing and assembly and is extremely expensive. There was a drawback.

An object of the present invention is to reduce the axial length of an electric power steering device, thereby achieving miniaturization and improving the ease of installation in a vehicle.

Another object of the present invention is to improve transmission torque by preventing uneven contact of clutch teeth when an electromagnetic tooth clutch is provided in an electric power steering system to ensure safety.

[Means to solve the problem]

The above object is achieved by the configuration set forth in claim 1.

[Effect]

By using staggered shaft gears such as hypoid gears and spiroid gears as the gears of the reducer of the electric power steering device, the large gears and small gears can be arranged with an offset amount. By increasing the amount of offset within the range where the large gear and small gear mesh, the outer diameter of the bearing housing can be expanded to the extent that it does not come into contact with the small gear.
The bearing can be lowered to a position where the radial position of the pinion and the projection plane overlap.

In addition, if the torque detection means of the electric power steering device is built into the steering column, the torque detection means will be placed outside the conventional electric power steering device, and the axial length will be shortened accordingly. Since the means are placed within the conventional steering column, the axial length remains unchanged, so the overall axial length is reduced.

In order to achieve uniform contact of the electromagnetic tooth clutch, first, crowning is performed in the tooth width direction of the external gear formed on the outer periphery of the large gear to give the tooth tips a crown shape. Due to these, the teeth of the external gear and the internal gear come into spherical contact, and the internal gear can rotate by a small angle relative to the external tooth surface.

When the ring teeth are attracted by the solenoid coil, the ring teeth mesh with the rotor teeth, but the electromagnetic force between the teeth carved on the ring side and the teeth carved on the rotor side is uneven, or the accuracy of the teeth is low. As a result, it was previously difficult for all the teeth to mesh.

In the present invention, all the teeth of the ring are sucked while being rotated by a small angle so as to mesh with all the teeth of the rotor, so that uniform contact can be achieved.

[Embodiment] Hereinafter, an embodiment of the present invention will be explained with reference to FIG.
．． Torsion bar 2. It has an electric motor (not shown), a reduction gear 17 composed of a small gear 4 formed at the end of an armature shaft 3 of the electric motor, and a large gear 7 inserted into a lower shaft 5 via a sliding bearing 6.

The figure shows a large gear 7 and a lower shaft 5, which are the torque transmission path.
A clutch is interposed between the two to ensure stability in the event of a failure of the control device or electric motor.

Although an electromagnetic tooth clutch 8 is used as the clutch in the embodiment, other clutches such as a crocodile-way clutch may also be used.

The electromagnetic tooth clutch 8 has a stator 22. which has a built-in solenoid coil 21. Rotor 23 keyed to lower shaft 5. A ring 24 that is attracted downward when the solenoid coil 21 is energized. A leaf spring 25 whose respective ends are fixed to the ring 24 and the large gear 7. It is composed of a thrust bearing 26 that supports the thrust load of the large gear 7.

An embodiment of the torque detection means 1 includes magnetic drums 11 and 11' that generate pulses and a magnetic sensor 1 that reads the pulses.
Although a method for detecting torque using a combination of the above two methods has been described, a strain gauge method, a potentiometer method, a capacitance method, etc. may also be used.

The operation of the apparatus will be explained below with reference to FIG.

When the driver operates a handle (not shown) in FIG. 1, the torsion bar 2 located between the upper shaft 9 and the lower shaft 5 is twisted. The upper shaft 9 and the torsion bar 2 are fastened together by a pin 10, and the lower shaft 5 and the torsion bar 2 are fastened together by a pin 11. The amount of twist is determined by the magnetic drum 11. Read with magnetic drum 11' and magnetic sensor 12,
A controller (not shown) issues a command to a motor (not shown), causing the motor to rotate. At this time, the solenoid coil 21 also operates, and the ring 24 overcomes the spring force of the leaf spring 25 and is attracted downward, causing teeth 13 formed on the side surface of the ring 24 and teeth 13' formed on the side surface of the rotor 23
The internal gear formed on the inner periphery of the ring 24 and the external gear formed on the outer periphery of the ring 24 are in mesh with each other even when the ring 24 moves downward, so that torque is transmitted. At this time, the tooth surface of the external gear is crowned (Fig. 8).

(Fig. 9), the tooth tips are crown-shaped (Fig. 7), so the ring 24 can rotate at a small angle relative to the large gear 7, and Since the ring 24 is rotatable even when the ring 24 is rotated, the ring 24 moves in a self-centering manner so that all of the teeth 13 and 13' mesh with each other.

The rotation of the electric motor causes a small gear 4 formed at the end of the armature shaft 3 to rotate, which is decelerated by a large gear 7 and transmitted to the lower shaft 5 via an electromagnetic tooth clutch 8. The configuration of the electric steering device is the same whether it is placed in the engine room or in the passenger compartment.

If the electric power steering device is installed in the engine loop (FIG. 3), a pinion is formed at the end of the lower shaft 5 and engaged with the rack shaft. When the binion rotates, the rack shaft moves in the axial direction, changing the direction of the axle via the tie rod and knuckle arm.

In addition, if the device is installed inside the vehicle (Fig. 2),
The rotation of the lower shaft 5 is transmitted to the binion shaft via the joint, and the direction of the wheels is then changed along the same path as in the engine room.

FIG. 6 is a sectional view taken along the line A-AM in FIG. 1.

The lower shaft 5 is supported by an upper bearing 31 and a lower bearing 32. The upper bearing 31 is inserted into the bouncing 33, and the positional relationship between the housing 33 and the pinion 4 is shown in Fig. 1.
As shown by the marks, when viewed on the projection plane, they are arranged so as to overlap each other.

Furthermore, as shown in FIG. 3, the housing 33 and the small gear 4 are arranged so as not to come into contact with each other. Big gear 7
The outer diameter of the housing 33 can be increased by using staggered gears such as hypoid gears and spiroid gears for the small gear 4 and providing a large offset amount.

Since the upper bearing 31 is at the same axial position as the small gear 4 as shown in FIG. 1, the axial length is reduced by the width of the bearing that was conventionally required.

Next, FIG. 10 shows an embodiment in which the torque detection means is disposed inside the steering column.

Although a magnetic sensor method is shown as the torque detection means, strain gauge method, potentiometer method,
The configuration other than the torque detection means, which may be of a capacitive type, is the same as that of the previous embodiment (however, there is no torsion bar 2,
The upper shaft 9 and the lower shaft 5 are integrated. In this embodiment, this is called the upper shaft 9).

The upper shaft 9 and the handle shaft 41 are connected by a pipe 40, and magnetic drums 11' are installed at the upper and lower parts of the pipe.
Place 1. When the handle is operated, the pipe 40 is twisted, and the amount of twist is read by the magnetic drum 11, 11' and the magnetic sensors 12, 12', and the electric motor rotates to assist the handle operation.

The flange 42 bolted to the case 39 and the column housing 43 are connected by an outer pipe 44, and the housing 4
3 has a magnetic sensor 12' facing the magnetic drum 11', and a flange 42 has a magnetic sensor 12 facing the magnetic drum 11.
bury it. The phases of the magnetic sensor outputs are adjusted so that they match when the twist angle is zero, as shown in FIGS. 2, 3, and 4.

As shown in FIG. 5, devices other than the torque detection means may be placed either in the vehicle interior or in the engine room.

〔Effect of the invention〕

According to the present invention, by arranging the upper bearing of the electric power steering device at the same axial position as the small gear of the reducer, the bearing width is divided and the axial length is shortened, resulting in a compact and lightweight device. , it is easier to install in automobiles.

Furthermore, by housing the torque detection means inside the steering column, the axial length required for the torque detection means is eliminated, resulting in a compact and lightweight device that is shortened in the axial direction.

Next, by increasing the number of teeth that mesh with each other in the electromagnetic tooth clutch, the transmitted torque is improved.

Further, by arranging the torque detection means within the steering column, a mechanical stopper is not required, resulting in an electric power steering device that is inexpensive and easy to control.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and FIG. Figures 3, 4, and 5 are schematic diagrams of the types of electric power steering devices, Figure 6 is a sectional view taken along line A-A in Figure 11, and Figure 7 is a vertical sectional view of the large gear. Figure 8 is a top view of Figure 7, Figure 9 is B-B of Figure 7.
FIG. 10, which shows the crowning shape in a line cross-sectional view, is a longitudinal cross-sectional view showing an embodiment of an electric power steering device having a torque detecting means inside the collar 11. 2... Torsion bar, 4... Small gear, 5... Lower shaft, 7... Large gear, 11... Magnetic drum,
12...Magnetic sensor, 13...Tooth%23...
Rotor, 24...ring, 31...upper bearing.

Claims (1)

[Claims] 1. Torque detection means for detecting steering torque, a reduction gear comprising an electric motor driven in accordance with the output signal, a small gear and a large gear for decelerating the output of the electric motor, and torque detection. In an electric power steering device having an upper shaft located above the means and a lower shaft located below the means, the lower shaft is supported by two bearings, an upper bearing and a lower bearing, and the axial position of the upper bearing is controlled. An electric power steering device characterized in that a portion is provided where the radial position of the small gear overlaps. 2. The electric power steering device according to claim 1, wherein the torque detection means is installed inside the steering column. 3. In claim 1, a large gear with an annular external gear formed on the outer periphery, a ring with an annular internal gear formed on the inner periphery, a leaf spring combining the large gear and the ring, a rotor fixed to the lower shaft, and a solenoid coil. An electric power steering device characterized by being equipped with an electromagnetic tooth clutch consisting of a built-in stator. 4. The electromagnetic tooth crack according to claim 3, wherein the tooth surface of the external gear formed on the outer periphery of the large gear is crowned, and the tips of the teeth are crowned in the tooth width direction. Device.