JP2539013Y2 - Overload prevention device for electric steering system - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention includes a power transmission circuit that transmits the rotational force of a motor to a steering gear via a speed reduction mechanism, and prevents overload transmitted to the power transmission path from the overload. The present invention relates to an overload prevention device in an electric steering device for protecting a speed reduction mechanism.

(Prior Art) As this kind of apparatus, one described in Japanese Utility Model Laid-Open No. 2-15576 is conventionally known.

This conventional device relates to an electric steering device, and connects an input shaft and a pinion shaft which is an output shaft via a torsion bar, and detects an input torque of the input shaft in accordance with a relative rotation amount of both shafts. Like that.

The output of the electric motor is transmitted to the pinion shaft according to the detected torque. That is, the output of the electric motor is transmitted to the second small gear via the first small gear and the first large gear, and the second large gear is meshed with the second small gear. . The second large gear is press-fitted to a pinion shaft. Therefore, when the electric motor rotates, it is transmitted to the pinion shaft while being decelerated by the gears. Since the pinion formed on the pinion shaft engages with the rack shaft, the driving force of the electric motor moves the rack shaft, and steers wheels provided at both ends of the rack shaft.

The reason why the second large gear is pressed into the pinion shaft as described above is to protect the electric motor when an overload is applied to the electric motor. For example, when an overload acts on the electric motor, the pinion shaft, which is the press-fit portion, and the second large gear slip. If the two slip as described above, no overload acts on the electric motor.

(Problem to be Solved by the Present Invention) In the conventional device as described above, the overload is prevented from acting on the electric motor only by the frictional force of the press-fit portion between the second large gear and the pinion shaft. Therefore, there were the following problems.

That is, as described above, preventing overload only by the friction force depends on the friction coefficient of the press-fitted portion. However, since this friction coefficient changes according to the conditions at the time of press-fitting the second large gear and the pinion shaft, the set value of the slip torque when both start to slip also changes.

If the set value of the slip torque is smaller than the expected set value, the output of the electric motor is not transmitted when necessary,
Conversely, if the value is larger than the desired set value, an unnecessary load acts on the electric motor.

It is also known that the friction coefficient includes a static friction coefficient and a dynamic friction coefficient, and that the static friction coefficient is larger than the dynamic friction coefficient. Therefore, even if the initial slip torque is sufficiently increased, there is a problem that once the slip starts, the slip does not stop easily and the slip continues.

An object of the present invention is to provide an overload prevention device in an electric steering device that can accurately specify a slip torque.

(Means for Solving the Problems) The present invention includes a power transmission path for transmitting the rotational force of a motor to an output side via a speed reduction mechanism. An overload transmitted to this power transmission path is provided in the power transmission path. It is premised on an overload prevention device in the electric steering device that absorbs with the provided torque limiter.

In the first invention, on the premise of the overload prevention device, the torque limiter includes a main body, a driven body coaxially receiving the main body and relatively rotatably arranged, and a main body and a driven body. And a click mechanism that links
The click mechanism includes a pad rotating integrally with one of the main body and the driven body, a plurality of recesses formed in the pad, and a recess formed in the other of the main body and the driven body, and a recess formed in the pad. A plurality of recesses opposed to each other, a plurality of balls interposed between the opposed recesses, and a presser spring for applying a pressing force to press the pad against the ball, and a load acting on the power transmission path is set at a set value. If the load is equal to or less than the set value, while the main body and the driven body rotate integrally via the ball,
The present invention is characterized in that the ball is pushed away from the pad to be disengaged from the concave portion of the pad, and the main power and the driven body are relatively rotated.

According to a second aspect of the present invention, on the premise of the overload prevention device, the torque limiter includes a main moving body, a driven body coaxially receiving the main moving body and arranged to be relatively rotatable, and A click mechanism that links the body with the body. The click mechanism includes a plurality of recesses formed on the outer peripheral surface of the main body, a pad provided in the driven body, a notch formed in the driven body, and a cut formed in the pad. A notch formed in combination with the notch, and a concave portion facing the concave portion of the main moving body,
A ball interposed between these opposing concave portions, and a pressing spring for applying a pressing force to press the pad against the ball; if a load acting on the power transmission path is equal to or less than a set value, the main moving body and the driven body While the ball rotates integrally via the ball, if the load exceeds a set value, the ball pushes away the pad and separates from the notch formed in the driven body and the notch formed in the pad, and the main power And the driven body are relatively rotated.

(Operation of the present invention) In the overload prevention device of the electric steering device of the present invention, the main body and the driven body of the torque limiter are linked via the click mechanism. When a slip torque enough to get over acts, in other words, when an overload acts on the electric motor, the main body and the driven body relatively rotate. Then, in the process of the relative rotation, the ball is again accommodated in the concave portion. At this time, if the slip torque is small, the ball remains in the concave portion, and the slip between the main moving body and the driven body ends. .

If the slip torque is still large while the ball is in the recess, the main body and the driven body continue to rotate relative to each other.

(Effect of the present invention) According to the overload prevention device in the electric steering device of the present invention, the desired slip torque can be specified by the size of the concave portion and the strength of the holding spring, so that the set value is accurately determined. be able to.

Further, there is no problem that the initial values such as the dynamic friction and the static friction are different from the subsequent values as in the related art.

(Embodiment of the present invention) In this embodiment, as shown in FIG. 1, a hypoid pinion 41 and a hypoid wheel 42 are used as a reduction mechanism 40 of a reduction gear for reducing the rotation of the electric motor 6 to a predetermined reduction ratio. Using hypoid gears. The pinion 7 that meshes with the rack 4 is provided integrally with the hypoid wheel 42. Therefore, the rotation of the electric motor 6 is transmitted in the order of the hypoid pinion 41 → the hypoid wheel 42 → the pinion 7 → the rack 4.

In such a power transmission path, a torque limiter 43 is interposed between the electric motor 6 and the hypoid pinion 41. The torque limiter 43 connects the output shaft 17 of the electric motor 6 and the shaft 44 of the hypoid pinion 41.
The configuration of the torque limiter 43 will be described later with reference to FIG.
3, the relationship between the load and the set value is as follows. That is, if the load on the power transmission path is equal to or less than the set value, the rotational force of the electric motor 6 is transmitted to the hypoid pinion 41. When an overload equal to or more than a predetermined value acts, the overload is absorbed.

Here, the torque limiter 43 is provided between the electric motor 6 and the hypoid pinion 41, but the torque limiter 43 may be provided between the hypoid wheel 42 and the pinion 7. Further, the torque limiter 43 may be provided both between the electric motor 6 and the hypoid pinion 41 and between the hypoid wheel 42 and the pinion 7.

Although the hypoid gear including the hypoid pinion 41 and the hypoid wheel 42 is used as the speed reduction mechanism 40, a bevel gear, a worm gear, or the like may be used.

Based on FIGS. 2 and 3, the torque limiter
The specific structure of 43 will be described.

The torque limiter 43 includes a main moving body 45, a driven body 46 that transmits to the main moving body 45, and a click mechanism 47 that links the main moving body 45 and the driven body 46.

The main moving body 45 is a rotating shaft. The driven body 46 is a housing having a bottom wall 52 for accommodating the main driven body 45 on the axis.

The click mechanism 47 includes a pad 49 fixed to the distal end of the main moving body 45 and rotating integrally with the main moving body 45, and a plurality of (at least 3) arranged on the same circumference centered on the axis of the main moving body 45.
) Balls 48, a pressing spring (coil spring) 50 for applying a predetermined pressing force to the pad 49, and a pressing spring
A spring receiver 51 for setting an initial load of 50 is provided.

Further, a recess 53 having a V-shaped cross section for fitting and holding each ball 48 is formed on the inner surface of the bottom wall 52 of the driven body 46. These recesses 53 are arranged at equal intervals on the same circumference. Each ball 48 fitted into each recess 53 is pressed by a pad 49 provided at the inner end of the main body 45.

A concave portion 54 having a V-shaped cross section for fitting and holding each ball 48 is formed on the outer surface of the pad 49. These recesses
54 are arranged at equal intervals on the same circumference. FIG. 3 shows the pad 49 as viewed from below in FIG. 2, and these recesses 54 are connected by annular guide grooves 55 which are shallower than this.

An annular stopper member 56 for restricting movement of the pad 49 in the axial direction is fixed to the opening end side of the driven body 46. Further, a spring receiver 51 is provided at the axial center of the stopper member 56.
Is screwed. A presser spring 50 is interposed between the spring receiver 51 and the pad 49.

Reference numeral 57 in the figure denotes a bearing that supports the main moving body 45 rotatably and movably in the axial direction.

The torque limiter 43 configured as described above includes a concave portion 53,
When the ball faces each other and the ball 48 is held in the opposed concave portions 53 and 54, the main moving body 45 and the driven body 46 rotate integrally. In other words, the output of the electric motor 6 is transmitted to the rack shaft on which the rack 4 is formed.

When each ball 48 pushes back the pad 49 against the pressing spring 50 and comes out of the concave portion 54 of the pad 49, the ball 48 rolls on the guide groove 55, so that the main moving body 45 and the driven body 46 relatively rotate. . In other words, the output of the electric motor 6 is not transmitted to the rack shaft.

 Next, the operation of this embodiment will be described.

If the load acting on the power transmission path is equal to or less than the set value, the main body 45 and the driven body 46 rotate integrally as described above. Even if the ball 48 is disengaged from the recess 54 at the initial stage, the ball 48 is fitted and held in the recesses 53 and 54 during the relative rotation between the main body 45 and the driven body 46.
Thereafter, the main moving body 45 and the driven body 46 are integrally rotated.

On the other hand, if the load acting on the power transmission path is equal to or more than the set value, the ball 48 cannot be pressed down by the spring force of the pressing spring 50, so that the ball 48 is pushed out of the pad 49 and is pushed out to the guide groove 55 side. When the ball 48 is pushed out into the guide groove 55, the driven body 46 and the main moving body 45 fixed to the pad 49 become relatively rotatable.

As described above, when the load applied to the power transmission path is equal to or less than the set value, the torque limiter 43
The main body 45 and the driven body 46 are relatively rotated if the set value is equal to or more than the set value. As a result, the torque limiter 43 can absorb the overload transmitted to the power transmission path.

The set value of the slip torque is determined by the size and depth of each of the recesses 53 and 54 and the initial load of the presser spring 50. The initial load of the presser spring 50 can be set to some extent by turning the spring receiver 51.

When the torque limiter 43 is provided between the electric motor 6 and the hypoid pinion 41, the main moving body 45 is connected to the output shaft 17 of the electric motor 6, and the driven body 46 is connected to the shaft 44 of the hypoid pinion 41. Is also good. However, in this case, the follower 46 is formed by a boss formed on the axial center of the outer surface of the bottom wall 52.
It must be connected to shaft 44 via 58.

FIG. 4 shows another example of the structure of the torque limiter 43. In the case of this structure, the same overload prevention function as that of the structure shown in FIG. 2 is achieved.

In this structure, a plurality of recesses 54
Is formed. In addition, the notch formed on the inner surface of the pad 49 and the notch formed on the inner surface of the bottom wall 52 of the driven body 46 combine to form a plurality of recesses 53 facing the recesses 54.
Then, a pressing force is applied to the pad 49 by the pressing spring 50, and the notch of the pad 49 is pressed against the ball 48.

Even with the torque limiter 43 configured as described above, if the load acting on the power transmission path is equal to or less than the set value, the main driving body 45 and the driven body 46 rotate integrally. If the load acting on the power transmission path is equal to or greater than the set value, the ball 48 pushes away the pad 49 and separates from the recess 53, so that the driven body 46 and the main moving body 45 are relatively rotatable.

Here, a disc spring is used as the pressing spring 50, but it is obvious that this may be a coil spring.

[Brief description of the drawings]

FIGS. 1 to 4 show an embodiment of the present invention. FIG. 1 is an overall structural view, FIG. 2 is a sectional view showing a specific structure of a torque limiter used in the present invention, FIG. 3 is a plan view showing a pad of the torque limiter, and FIG. 4 is a sectional view showing another example of the structure of the torque limiter. 6 electric motor, 40 reduction mechanism, 43 torque limiter,
45: Main body, 46: Follower, 47: Click mechanism, 48: Ball, 49: Pad, 50: Presser spring, 51: Spring receiver.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-137255 (JP, A) JP-A-2-15576 (JP, U)

Claims (2)

(57) [Scope of request for utility model registration] An electric power transmission path for transmitting a rotational force of a motor to an output side via a speed reduction mechanism, wherein an overload transmitted to the power transmission path is absorbed by a torque limiter provided in the power transmission path. In the overload prevention device for a steering device, the torque limiter includes a main moving body, a driven body that coaxially receives the main moving body and is relatively rotatably disposed, and a click mechanism that links the main moving body and the driven body. Consisting of
The click mechanism includes a pad rotating integrally with one of the main body and the driven body, a plurality of recesses formed in the pad, and a recess formed in the other of the main body and the driven body, and a recess formed in the pad. A plurality of recesses opposed to each other, a plurality of balls interposed between the opposed recesses, and a presser spring for applying a pressing force to press the pad against the ball, and a load acting on the power transmission path is set at a set value. If the load is equal to or less than the set value, while the main body and the driven body rotate integrally via the ball,
An overload preventing device in an electric steering device, wherein a ball pushes away a pad and comes off a concave portion of the pad, so that a main power and a driven body relatively rotate. A power transmission path for transmitting the rotational force of the motor to an output side via a speed reduction mechanism, and an overload transmitted to the power transmission path is absorbed by a torque limiter provided in the power transmission path. In the overload prevention device for a steering device, the torque limiter includes a main moving body, a driven body that coaxially receives the main moving body and is relatively rotatably disposed, and a click mechanism that links the main moving body and the driven body. Consisting of
This click mechanism is formed by combining a plurality of recesses formed in the outer peripheral surface of the main body, a pad provided in the driven body, a notch formed in the driven body, and a notch formed in the pad, together with the main body. A concave portion facing the concave portion, a ball interposed between the concave portions facing the concave portion, and a pressing spring for applying a pressing force to press the pad against the ball, and a load acting on the power transmission path is equal to or less than a set value. For example, while the main body and the driven body rotate integrally via the ball, if the load exceeds a set value, the notch formed in the driven body and the notch formed in the pad by the ball pushing away the pad and the pad are combined. An overload prevention device in an electric steering device, wherein a main power and a driven body are configured to rotate relative to each other outside a recess formed.