JPS63251367A - Electromotive power steering device - Google Patents

Abstract

PURPOSE:To realize a compact size by positioning an electric motor at the opposite side of the wheel axis system to the steering axis system in a steering gear, and using a hyperboloidal gear at a reduction gear. CONSTITUTION:An electric motor 8 is positioned at the opposite side of a rack shaft 6 to a pinion shaft 4, and the electric motor 8 and a reduction gear 9 are arranged to keep an interval to avoid the interference each other near the rack shaft 6. The reduction gear 9 to reduce the rotation of the electric motor 8 composes a hyperboloidal gear with the larger gear 20 of a spiroid gear connected at a pinion shaft 3 side and the smaller gear 19 of a spiroid gear connected directly to an armature shaft 18 of the electric motor 8. Between the reduction gear 9 and the pinion shaft 3, a torque one-way clutch 10 is placed to control the application and the release of the steering torque.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electric power steering device, and in particular,
The present invention relates to an electric power steering device suitable for improving the ease of attaching an electric motor and a speed reducer to a vehicle.

[Prior art] A conventional electric power steering device is, for example, disclosed in Japanese Patent Application Laid-open No. 5
As described in 9-63265, it is composed of a steering shaft, an electric motor, a reduction gear, a torque detection means, and a control means. The technology is the first electric power steering device.
The purpose of this is to make it easy to secure installation space.

However, in this embodiment, a two-stage speed reducer with parallel shaft gears is used as the speed reducer, and the space occupied by the speed reduction mode is large.

If you try to obtain the same assist force as a conventional hydraulic power steering device with an electric power steering device,
The torque of the reducer output shaft is approximately 5 kg-m, and in order to ensure durability, the gears must be large, and if parallel shaft gears are used, the reducer will become extremely large.

Further, as another example, there is an electric power steering device described in Japanese Patent Laid-Open No. 57-47251.

In this example, the motor is arranged at the bottom of the steering gear device, but as mentioned earlier, in order to obtain the same assist force as the hydraulic type, the motor is required to have a large output. As the motor becomes larger, there is a risk that it will not be possible to secure mounting space.

In other words, the steering wheel is turned by 1 when the maximum assist force is generated.
Assuming that the rotation is performed at a speed of 1 revolution per second, the output of the motor must be approximately 4.0 mm in order to follow this speed, considering efficiency. According to the catalog, the size of a DC servo motor with this capacity is approximately 100 m in diameter.
m, length 250 nn+.

This also applies to the DC servo motor shown in the embodiment described in JP-A-59-63265.
The motor and speed reducer are so large that it is difficult to store them in the passenger compartment or engine room.

[Problems to be solved by the invention] As mentioned above, the conventional technology does not take into consideration the mountability of the electric power steering device on the vehicle body.
In order to install an electric power steering device on a car body that is currently equipped with a hydraulic power steering device, there is a problem that a major modification of the car body is required and a large amount of cost is required. Although there is no mention of buckle in the gear reducer, if there is buckle in the gear reducer, there will be a delay in the assist force for the driver's steering operation, and there is a risk of hunting when turning the steering wheel. There is a problem with this, and it is necessary to minimize the breakage as much as possible.

Furthermore, in conventional technology, the armature shaft of the electric motor and the steering shaft system are mechanically rigidly attached, but in such a configuration, the electric motor can rotate on its own due to a system failure such as a failure in the control system or electrical system. If this happens, the driver must also drive the inertia load of the armature shaft and reducer when steering, which not only requires a great deal of effort but also has a serious impact on ensuring the running stability of the vehicle. This was a major problem.

The present invention has been made in order to solve the problems of the prior art described above, and is capable of avoiding interference with various equipment in the engine compartment and vehicle interior, is compact, easy to install, has good operability, and has a system. The object of the present invention is to provide an electric power steering device that can be manually handled when the vehicle is down.

[Means for Solving the Problems] In order to achieve the above object, the electric power steering device according to the present invention has a configuration including a torque detection means for detecting the steering torque of the steering shaft system, and an output of the torque detection means. In an electric power steering device having an electric motor driven in accordance with a signal and a reduction gear section for transmitting the rotational force of the electric motor to a steering shaft system, the electric motor is connected to a steering shaft system in the steering gear section. The speed reducer is located on the opposite side of the wheel shaft system, and the reduction gear unit constitutes a stagger shaft gear by a large gear connected to the steering shaft system and a small gear directly connected to the armature shaft of the electric motor. This is what I did.

Further, the steering shaft system is provided with a torque one-way clutch that releases the inertial load of the electric motor and the speed reducer section when the steering shaft system is operated manually.

More details will be explained with reference to FIGS. 2 and 3.

FIG. 3 is a schematic configuration diagram of a general steering device as seen from the front of an automobile.

By imitating the handle 1, the first steering shaft 2-1. is a steering shaft system. The pinion shaft 3 is rotated through the second steering shaft 2-2, and the rack 5 that engages with the pinion 4 is moved in the axial direction, and the rack shaft 6, which is the wheel shaft system, is rotated, and the tire (the wheel) is rotated through the second steering shaft 2-2.
(not shown).

FIG. 2 is a schematic configuration diagram of an electric power steering device showing one embodiment of the present invention.

Third steering shaft 15 between second steering shaft 2-2 and pinion 4
A clutch 10 is provided on the pinion shaft 3, and the electric motor 8
, and a reduction gear 9 to constitute an electric power steering device.

As a means to solve the above-mentioned three problems, in the present invention, first, the reducer 9 is configured with staggered shaft gears, and the axis of the small gear, that is, the axis of the electric motor 8 is aligned with the rack shaft 6 with respect to the center line of the pinion shaft 3. placed in the opposite direction. As a result, the electric motor 8 is positioned almost parallel to the rack axis 6 and slightly above the rack axis 6 when viewed from the vehicle body.
The ease of mounting on the vehicle body is greatly improved.

In FIG. 1, which will be described in detail later in the embodiment, a commonly used spiroid gear with a shaft intersection angle of 90° is shown as an example of a staggered shaft gear, so the rack shaft 6 and the electric motor 8 shaft center are Although they are not parallel to each other, they can be made parallel if the design is made according to the intersection angle between the rack shaft 6 and pinion shaft 3 of the target steering system.An example of such a case will be described later. This is shown in Figure 9.

Spiroid gears are similar to hypoid bevel gears, but their operating state is similar to that of worm gears, making them suitable for connecting diagonal shafts.
Works) product name.

Next, regarding the removal of backlash, in the case of gears such as spiroids and hypoids where at least one of them has an umbrella-shaped pitch surface, the backlash can be adjusted by moving the axis of either one of the meshing gears back and forth. In the case of screw gears, this is possible by changing the center distance.

Furthermore, as a means for removing the inertial load when the electric motor 8 does not rotate by itself, the torque from the electric motor 8 side is transmitted to the pinion shaft 3, but the torque transmission from the pinion shaft 3 to the electric motor 8 is interrupted. This is achieved by installing a one-way clutch.

The configuration of the torque one-way clutch will be explained with reference to FIG.

FIG. 7 is a front view of the clutch portion.

The clutch shown in FIG. 7 has a plurality of wedge-shaped spaces formed by the inner circumferential groove of the clutch outer 21, in which the large gear of the staggered shaft gear is integrally formed, and the outer circumference of the clutch inner 17, which is directly connected to the pinion shaft 3. There is.

The retainer 23 has a plurality of grooves formed around the retainer 23 so as to accommodate the plurality of rollers 22 with a slight gap therebetween. A groove with a semicircular cross section is formed on the outer periphery of the retainer 23, and an arc shaped spring with a circular cross section is formed in the groove.
has been inserted.

This retainer 23 is inserted between the clutch outer 21 and the clutch inner 17, and the end of the spring ring 24 is secured to a fixed case 29 by a rotation stop pin 25.

Its effect will be described later.

[Function] By using staggered gears and arranging them as described above, the electric motor 8 is mounted slightly above the rack shaft 6 and substantially parallel to the rack shaft 6 when viewed from the vehicle body. therefore,
In conventional hydraulic power steering devices, the electric motor can be accommodated by simply expanding the space left open for hydraulic piping.

Further, the adjustment of the backup rate will be described later in the description of the embodiment.

Next, the operation of the torque one-way clutch will be explained with reference to FIG. 7.

When the reducer 9 operates and the clutch outer 21 rotates,
Since the spring ring 24 is stopped, the retainer 23 to which it is frictionally coupled is also momentarily stopped, and the roller 22 bites into the surface of the wedge-shaped space on the opposite side to the rotation direction of the clutch outer 21. , transmits torque to the clutch inner 17.

When the clutch outer 21 rotates in the reverse direction, the roller 22 bites into the surface opposite to the forward rotation due to the same effect, and the clutch inner 1
7 to transmit torque.

Next, when the clutch inner 17 rotates, the retainer 23 applies a force in a direction opposite to the rotating direction of the clutch inner 17 due to the frictional force of the spring ring 24 because the spring ring 24 is locked to the case. The bearing roller 22 rolls and slides out of the groove, and the clutch inner 17 idles. Even if the clutch inner rotates in the opposite direction, it will idle due to the same effect.

Due to this action, even if the handle 1 of the steering shaft system connected to the clutch inner 17 is rotated, torque is transmitted to the pinion shaft 3, the clutch inner 17 idles, and the torque is transmitted to the large gear, small gear, and armature shaft. Since no torque is transmitted, manual steering can be performed even when the electric motor 8 is not operating.

[Embodiments] Hereinafter, each embodiment of the present invention will be described with reference to FIGS. 1, 2, and 4 to 9.

1 is a longitudinal cross-sectional view of an electric power steering device according to an embodiment of the present invention, FIG. 4 is an enlarged cross-sectional view taken along the line A-A in FIG. 1, and FIG. 5 is a clutch shown in FIG. 1. FIG. 6 is a sectional view taken along the line II in FIG. 5, FIG. 7 is a front view of the clutch portion, and FIG. 8 is a partially enlarged view of FIG. 7.

In the figure, 3 is the third steering wheel of the steering shaft system! Pinion shaft directly connected to 11115, 4 is pinion, 5 is pinion 4
The meshing rack 6 is a rack shaft related to a wheel shaft system, and a steering gear portion 11 is configured as shown by a two-dot chain line in FIG.

Reference numeral 7 indicated by a two-dot chain line in FIG. 1 is a torque detector that detects the steering torque of the steering shaft system. This torque detector 7 is 1
When torque is applied manually to the handle 1, the torsion bar 12 twists and the upper sensor 13. Lower sensor 1
4 is configured to detect the amount of twist of the shaft.

Note that a torque detector that detects torque by converting shaft torsion caused by torque into a capacitance change of a capacitor is described in detail in Japanese Patent Application No. 1982-210895, so a description thereof will be omitted.

Reference numeral 8 shown by a two-dot chain line in FIG. 1 is an electric motor that rotates forward or reverse according to the output signal of the torque detector 7. Reference numeral 9 is a reducer section that decelerates the rotation of the electric motor 8. , a large gear 20 of a spiroid gear connected to the pinion shaft 3 side and a small gear 19 of a spiroid gear directly connected to the motor shaft 18 of the electric motor 8 constitute a staggered shaft gear.

As shown in FIG. 4, the electric motor 8 is located on the opposite side of the rack shaft 6 with respect to the pinion shaft 4, and the electric motor 8 and the reducer section 9 are located near the rack shaft 6 and do not interfere with each other. They are spaced apart so that there are no gaps.

Reference numeral 10 shown by a two-dot chain line in FIG. 1 is a torque one-way clutch that is interposed between the speed reducer section 9 and the pinion shaft 3 and relates to a clutch means for attaching and detaching steering torque. The rollers 22 are configured to be built into a large gear 20 which is the output side of the speed reducer section 9. That is, 17 is the pinion shaft 3
The clutch inner 21 fixed to the large gear 20
22 is a plurality of rollers housed between the inner periphery of the clutch outer 21 and the outer periphery of the clutch inner 17; 23 is a retainer that accommodates these rollers 22; 24 is a spring ring; 25 is a It is a rotation stop pin.

The upper part of the torsion bar 12 is connected to the pin 3 on the third steering shaft 15.
4, and the lower part is fixed to the pinion shaft 3 with a pin 35. The upper sensor 13 is a torsion bar 12
The lower sensor 14 is fixed to the side surface of the clutch inner 17 at the end of the pinion shaft 3. Therefore, the phases of the sensors are shifted by the torsion angle of the torsion bar 12, and the upper sensor 13. Torque can be detected by changing the capacitance between the lower sensors 14.

As shown in FIG. 6, the lower end of the third steering shaft 15 has a gap in the circumferential direction so that it can rotate by a certain phase angle with respect to the clutch inner 17. When the torsion bar 12 is twisted by a certain helix angle, it comes into contact with the circumferential groove of the clutch inner 17 and will no longer twist. At this time, the third steering shaft 1
5 and the pinion shaft 3 are mechanically engaged to transmit torque. At this time, the electric motor 8 is instructed and controlled by a control section (not shown) to generate the maximum torque.

When the operating torque of the handle 1 is small and does not contact the circumferential groove, the electric motor 8 is controlled to generate a torque proportional to the torsion angle of the torsion bar 12 to assist the operating torque. When the electric motor 8 rotates according to a command from the control section, a small gear 19 integrally formed at the end of the armature shaft 18 of the electric motor 8 rotates, and is decelerated by a large gear 20 that meshes with the small gear 19. This large gear 20 is a clutch outer 21
is formed integrally with. As shown in FIG. 5, the load acting on the large gear 20 is applied to the sliding bearing 3
6. It is designed to be received by thrust metal 37.

FIG. 7 shows the structure of the clutch section.

A plurality of inner circumferential grooves are formed in the clutch outer 21, and a plurality of rollers 22 are arranged between the inner circumferential grooves of the clutch outer 21 and the clutch inner 17.

When the electric motor 8 rotates and the clutch outer 21 rotates 15 times in the direction of the arrow in FIG. Since it is stopped, the roller 22 is pushed into the wedge-shaped space formed by the left circular arc 26, which is the cam curve of the clutch outer 21, and the clutch inner 17, and the torque is transmitted to the clutch inner 17. Rotate in the direction of the dashed arrow.

The retainer 23 also rotates together with the clutch outer 21.

Since the spring ring 24 is restricted from rotating, the retainer 23
It is sliding between the outer periphery of

When the electric motor 8 rotates in the reverse direction, the retainer 23 has a splash @2.
4 exerts a frictional force in the opposite direction to the rotational direction of the clutch outer, so the roller 22 escapes from the wedge space and bites into the wedge space formed by the opposite circular arc 27 and the clutch inner 17, and torque is applied to the clutch inner 17. communicated.

In this embodiment, the cam curve of the inner circumferential groove of the clutch outer 21 is formed by a series of easily machined circular arcs having two equal radii centered at different points on the same circumference.

With this type of latch, some play may occur between the person and the output shaft during forward and reverse rotation, but if the cam curve is made into an arc and the center of the arc is determined appropriately, this can be avoided. The amount of backlash can be adjusted.

FIG. 8 shows a partially enlarged view of the clutch.

The roller 22 is connected to the clutch outer 21. clutch inner 1
It is in contact with point a and point b of 7. The radius of the clutch inner 17 is ○□b=t, the radius of the roller 22 is 02b=02a
=s, the arc radius of the cam curve is o4a=r, 010. +0
Let 4a=u.

The roller 22 is connected to the clutch inner 17. clutch outer 2
Whether it sticks to 1 or not depends on the friction coefficient. If the frictional force is greater than the tangential component force, there will be no slipping at the contact point, so the following equation (1) is a necessary condition.

μ) tanα・・・・・・(1) Here α: Wedge angle In Fig. 8, 10 hours 0204=2α, and α can be expressed by the following formula (2), so the formula (1) Decide each radius to satisfy.

In addition, each radius is determined based on the strength, and a value that satisfies both is adopted.

If the cam curve is one circular arc (radius r), the play in the rotational direction between the input and output shafts of the clutch, that is, the backlash angle, becomes very large and is not suitable for electric power steering.

In this embodiment, as shown in FIG. 8, the arc center is 0. ．．
A curve made by connecting two circular arcs of 05 was defined as a cam curve. Center of 2 circular arcs O1, ○6. The angle 104o1o5 formed with 0□ is γ
Then, the backlash angle (β) in this case is /a○1
c, and is expressed by the following formula (3).

β=2(θ+W)-γ...(3) Here, (k=s+r+s1〒2-'s (r+s) co
sO) Therefore, by appropriately selecting γ, the backlash angle β can be changed and can be made small.

As another example, a clutch having the same effect can be obtained by integrating two clutch outers having a one-circular cam curve with a radius r and shifting them by a phase angle β. If the phase angle β can be fixed after being adjusted, the rotational backlash angle can be adjusted freely.

The torque transmitted to the clutch inner 17 is transmitted to the pinion 4 via the pinion shaft 3, provides power to the rack shaft 6, and changes the direction of the tire (not shown) via a link (not shown).

When the electric power steering device has a system failure and the electric motor 8 does not rotate, the torque of the steering wheel 1 is transmitted to the pinion shaft 3 via the third steering shaft 15. The clutch inner 17 only idles, the clutch outer 21 is stopped, and the inertial loads on the reducer 9 and armature shaft 18 can be released.

Next, the discrepancy of the staggered shaft gears of the speed reducer section 9 will be explained with reference to FIG.

In this embodiment, as shown in FIG. 1, a spiroid gear is used as a speed reducer. Spiroid gear small gear 19
Since the tooth thickness dimension changes linearly in the tooth trace direction, the backlash amount can be adjusted by moving the small gear 19 in the axial direction.

Bearing 28 and case 29 supporting armature shaft 18
By inserting a shim 41 between the motor case 30 and the motor case 30, the amount of backlash can be adjusted.

Furthermore, the amount of backlash can be adjusted by moving the large gear 20 in the axial direction.

By pushing the bearing 32 with a nut 31 screwed into the upper case 33, the third steering shaft 15 and pinion shaft 3 are moved in the axial direction, and the large gear 20. Adjust the backlash between the small gears 19. The lower end of the pinion shaft 3 is threaded, the bearing 40 is tightened with a nut 38, and the cap nut 39 is tightened.
While pressing the outer race of the bearing 40, attach it to the case 29.

The amount of backlash can be adjusted on the small gear 19 side in a similar manner. By inserting an elastic material into the outer race of the bearing 28 instead of the shim 41, making the motor upper case 42 have the same structure as the upper case 33, and pushing the outer race of the bearing 43 with a nut, the armature shaft 18 is moved in the axial direction. You can adjust the amount of buffering.

The power steering device of this embodiment has the following effects.

That is, it is possible to provide an electric power steering device that is easy to attach to an automobile, has adjustable backlash, and has high responsiveness and reliability that can be used even when the system goes down.

In conventional electric power steering devices, little consideration was given to the size of the electric motor. In FIG. 2, the first steering shaft 2-1. The area near the second steering shaft 2-2 is close to the passenger compartment, and considering securing space around the suspension, it is difficult to place the electric power steering here, and the electric power steering must be placed near the third steering axis 15. Parallelism with the rack shaft 6 is unavoidable, and the configuration of this embodiment using staggered shaft gears can be said to be optimal as an electric power steering device.

In addition, a speed reducer with adjustable backlash is not found in conventional electric power steering devices, and it is possible to improve steering operability.

Furthermore, in the case of an electric power steering device, an electric motor,
Since the reducer is newly added to the rotation transmission system, if the steering wheel is operated only manually, unless the extra inertial load is released, the steering wheel cannot be operated and there is a risk of an accident. usually,
The moment of inertia of the reducer and armature shaft converted to the steering shaft system is larger than the moment of inertia of the handle alone, and is more than twice as heavy, impairing operability.

However, according to this embodiment, when the steering shaft system is operated manually, the inertia load on the reducer and armature shaft can be released by the function of the torque one-way clutch, and manual response is possible when the system goes down.

Furthermore, in conventional hydraulic power steering devices, the oil in the cylinder must be returned to the tank using part of the tire reaction force, resulting in poor restoring force. Here, restorability refers to the property of the steering wheel to return to its original position naturally due to tire reaction force after the steering wheel is turned in order to turn a curve.

Generally, if it is electrically operated, it is possible to provide this restorability by devising a control system, but the cost increases.

On the other hand, in an electric power steering device equipped with a torque one-way clutch like the electric power steering device of this embodiment,
If you let go of the steering wheel after the car has gone around a curve, the torque detector will not detect any torque, so the electric motor will not operate.
It becomes a manual steering state and can ensure restorability.

Next, another embodiment of the present invention will be described with reference to FIG.

FIG. 9 is a longitudinal sectional view showing the main parts of an electric power steering device according to another embodiment of the present invention.

The embodiment shown in FIG. 9 differs from the previous embodiment shown in FIG. 1 in the direction in which the electric motor 8 is arranged, and is otherwise the same as the previous embodiment.

In the previous embodiment shown in FIG. 1, a spiroid gear with an intersecting shaft angle of 90'' was used as the staggered shaft gear of the reducer section 9.
The rack shaft 6 and the axis of the electric motor 8 were not parallel to each other.

In the embodiment shown in FIG. 9, the shaft intersection angle ε (pinion shaft 3
(equivalent to the angle between the axis Y of the motor 8 and the axis X2 of the electric motor 8),
Crossing angle between pinion shaft 3 and rack shaft 6 (axis center Y and axis center
A spiroid gear with an intersecting axis angle of 60 to 90° is used in accordance with the angle formed with □) ε.

As a result, the axial center X2 of the electric motor 8 is located on the opposite side of the rack shaft 6 with respect to the pinion shaft 3.
Since it is located almost parallel to the rack shaft 6 and slightly above the rack shaft 6 when viewed from the vehicle body, the ease of mounting onto the vehicle body is greatly improved.

In this way, the embodiment shown in FIG. 9 is expected to have the same effects as the previous embodiment.

In each of the above-described embodiments, a spiroid gear is used as the staggered shaft gear, but a helicon gear, a hypoid gear, etc. may also be used, or a screw gear may be used to achieve the intended purpose.

In the screw gear, the axis intersection angle can be arbitrarily obtained by changing the respective helix angles, so that the axis of the electric motor and the rack axis can be made parallel.

Also, in order to make the axis of the motor parallel to the rack axis,
A universal joint 1 or a gear coupling may be interposed between the electric motor 8 and the small gear 19 in FIG. 1.

The reduction ratio of the electric power steering device is approximately 5.
~20, and the efficiency of the aforementioned staggered gears is approximately 8
5 to 95%, which is comparable to a two-stage reduction parallel shaft gear or a planetary gear device, so there is no problem.

Further, in the above-described embodiments, a capacitance type torque detector is used, but a strain gauge type torque detector may also be used.

[Effects of the Invention] As described above, according to this embodiment, interference with various equipment in the engine room and vehicle interior can be avoided, it is compact, easy to install, easy to operate, and is easy to operate when the system goes down. It is possible to provide an electric power steering device that can be operated manually.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of an electric power steering device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an electric power steering device according to an embodiment of the present invention, and FIG. FIG. 4 is a schematic configuration diagram of a general steering device.
1, FIG. 5 is a partially enlarged view showing the clutch section in FIG. 1, and FIG. 6 is an I-I diagram in FIG. 5.
7 is a front view of the clutch portion, FIG. 8 is a partially enlarged view of FIG. 7, and FIG. 9 is a main part of an electric power steering device according to another embodiment of the present invention. FIG. 3... Pinion shaft, 6... Rack shaft, 7... Torque detector, 8... Electric motor, 9... Reducer section, 10...
...Torque one-way clutch, 11...Steering gear section, 12...Torsion bar, 13...Upper sensor,
14... Lower sensor, 15... Third steering shaft, 17.
...Clutch inner, 18...Armature shaft, 19,19
A... Small gear, 20.2OA... Large gear, 21...
・Clutch outer, 22...roller, 23...retainer, 24...spring ring, 25...rotation stop pin.

Claims (1)

[Scope of Claims] 1. A steering gear unit that connects a steering shaft system and a wheel shaft system, a torque detection means for detecting the steering torque of the steering shaft system, and a drive unit that is driven in accordance with an output signal of the torque detection means. In an electric power steering device having an electric motor and a reduction gear unit for transmitting the rotational force of the electric motor to a steering shaft system,
The electric motor is located on the opposite side of the wheel shaft system with respect to the steering shaft system in the steering gear section, and the reduction gear section is connected to a large gear connected to the steering shaft system and an armature shaft of the electric motor. An electric power steering device characterized in that a staggered shaft gear is formed by directly connected small gears. 2. In the item described in claim 1, the axis of the electric motor is located on the opposite side of the rack axis related to the wheel axle system with respect to the pinion axis related to the steering axle system, and substantially parallel to the rack axis. An electric power steering device characterized by: 3. An electric power steering device according to claim 1, characterized in that the steering shaft system on the output side of the speed reducer section is provided with a clutch means for attaching and detaching steering torque. 4. In the product described in claim 3, the clutch means is a torque one-way clutch that can release the inertial load on the armature shaft and reduction gear part of the electric motor when the steering shaft system is operated manually. electric power steering device. 5. In the thing described in claim 4, the torque one-way clutch includes a clutch outer integrally formed with a large gear of staggered shaft gears, a clutch inner directly connected to a steering shaft system, and an inner periphery of the clutch outer. A plurality of rollers are housed between the outer periphery of the clutch inner via a wedge space formed by a cam curve on the inner circumferential surface of the clutch outer, and a retainer that houses the rollers and has rotation stopping means. A distinctive electric power steering device. 6. In the item set forth in claim 5, the cam curve of the inner circumferential surface of the clutch outer is formed by connecting two circular arcs having the same radius and having centers at different points on the same circumference. A distinctive electric power steering device.