JP3815960B2 - Torque sensor and steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensor for accurately detecting rotational torque applied to a shaft body with a simple configuration. The present invention relates to a steering apparatus for a vehicle provided with this torque sensor as a means for detecting steering torque.
[0002]
[Prior art]
Electric type configured to drive a steering assist motor based on a detection result of a steering torque applied to a steered wheel (steering wheel) for steering and transmit the rotational force of the motor to a steering mechanism to assist steering The power steering device has been put into practical use. In this type of power steering apparatus, in order to detect the steering torque, a steering shaft that communicates between the steering wheel and the steering mechanism is used as an input shaft (first axis) on the steering wheel side and an output shaft on the steering mechanism side. (Second axis) is connected via a small-diameter torsion bar, and based on the detection result of the relative angular displacement caused by twisting of the torsion bar between the first and second axes. A torque sensor that obtains the steering torque (rotational torque) is widely used.
[0003]
Such a steering torque detection result is used for driving control of a motor for assisting steering in an electric power steering apparatus, and in control of each part of the vehicle such as engine output control, traction control, ABS control, etc. There is a need to realize a torque sensor having a simple configuration that can be used as information indicating the steering state of the steering device and can detect the steering torque with high accuracy.
[0004]
[Problems to be solved by the invention]
In this type of torque sensor, it is necessary to detect the relative angular displacement generated between the first axis and the second axis with high accuracy. A general configuration for this detection is to detect the rotation angle of the first axis and the second axis by different rotation angle sensors, and obtain the relative angular displacement by the difference between these detection angles. is there.
[0005]
However, in this configuration, there is a possibility that an error may occur in the calculation result of the relative angular displacement due to the difference in the output characteristics of the two rotation angle sensors for the first and second axes, thereby enabling highly accurate detection. Therefore, it is necessary to adjust the outputs of the two rotation angle sensors at the time of assembling, and there is a problem that this adjustment work requires a lot of labor. The detection accuracy is inevitably lowered due to various characteristic changes.
[0006]
Further, as another configuration for detecting the relative angular displacement, discs opposite to each other are attached in the vicinity of the connecting portion of the first shaft and the second shaft, and a resistance portion provided around one of these discs is attached. A potentiometer is configured by slidingly contacting a contact projecting on the other side, and a relative angular displacement between a first axis and a second axis is detected using an output change of the potentiometer as a medium.
[0007]
In this configuration, since the output of the potentiometer directly corresponds to the relative angular displacement of the first and second shafts, adjustment during assembly is easy and detection with high accuracy is possible. However, there is a problem that wear of the sliding contact portion between the resistance portion and the contact is inevitable and the durability is inferior.
[0008]
As yet another configuration for detecting the relative angular displacement, a plurality of teeth are juxtaposed on the opposing surfaces of the cylinders fitted in the vicinity of the connecting portions of the first shaft and the second shaft, and detected on the outside thereof. A coil is arranged, and the impedance of the magnetic circuit formed in the cylindrical body according to the excitation of the detection coil is changed depending on the facing state of teeth arranged in parallel on the facing surface. Some of them detect a relative angular displacement between the first axis and the second axis.
[0009]
In this configuration, since the change in impedance of the magnetic circuit directly corresponds to the relative angular displacement of the first and second axes, adjustment during assembly is easy and detection with high accuracy is possible. In addition, although there is no sliding contact portion and the durability is excellent, there is a problem that the configuration of each part including the detection coil and the impedance change detection means becomes complicated.
[0010]
The present invention has been made in view of such circumstances, and can directly detect the relative angular displacement of the first and second shafts connected via the torsion bar without forcing a complicated adjustment operation. The torque sensor having a simple configuration capable of detecting the rotational torque applied to the first shaft and the second shaft with high accuracy without causing a change in accuracy over time, and the torque sensor as a steering torque detection means An object of the present invention is to provide a steering apparatus for a vehicle.
[0011]
[Means for Solving the Problems]
A torque sensor according to a first aspect of the present invention generates rotational torque applied to a first shaft and a second shaft that are coaxially connected via a torsion bar, with the torsion bar being twisted between the two shafts. in a torque sensor for detecting based on the relative angular displacement, said first constrained axially and one to the rotation of the second shaft, movable and fitted on the holding cylinder on the other, before Symbol first shaft in the axial direction And an engagement groove formed on the other outer peripheral surface of the second shaft with a predetermined inclination with respect to the axial direction, and an engagement that is eccentrically held inside the holding cylinder and is provided around the inner peripheral surface thereof. A feed bearing in which the mating protrusion is engaged with the engagement groove at one place in the circumferential direction, and the action of the inclination of the engagement groove with rolling of the feed bearing along the engagement groove detecting the axial displacement of the holding cylinder occurs with the feed bearing by Characterized in that it comprises left and means.
[0012]
In the present invention, when a rotational torque is applied to the first and second shafts connected via the torsion bar and a relative angular displacement occurs between the two shafts, the holding cylinder whose rotation is constrained to one shaft is eccentric. The held feed bearing rolls along an engagement groove formed on the outer peripheral surface of the other shaft, and the holding cylinder moves along the inclination of the engagement groove by the action of a reaction force accompanying the rolling. Displaces smoothly in the axial direction. Since the direction and magnitude of this axial displacement corresponds to the direction and magnitude of the relative angular displacement between the first and second axes, the rotational torque applied to the first and second axes via this displacement is highly accurate. Can know.
[0013]
In the torque sensor according to the second invention of the present invention, the detecting means of the first invention engages the tip with an annular groove provided on the outer surface of the holding cylinder, and the axial direction of the first and second shafts And a means for supporting a base portion of the detection arm and detecting the swing angle thereof.
[0014]
In the present invention, the detection arm having its tip engaged with an annular groove provided on the outer surface of the holding cylinder is swung in a plane substantially parallel to the axial direction as the holding cylinder moves in the axial direction. The swing angle is detected by a detection means that supports the base of the detection arm, and the rotation torque applied to the first shaft and the second shaft is obtained using the detection result. The detection means may be, for example, a rotary potentiometer in which a base portion of a detection arm is connected to an input end, and the output of the potentiometer is changed by swinging the detection arm due to the axial movement of a holding cylinder. It is realizable by the structure taken out as.
[0015]
The steering device according to the third aspect of the present invention is configured so that an input shaft connected to the steering wheel is the first shaft to detect a steering torque applied to the steering wheel for steering the vehicle. A torque sensor according to the first or second invention is provided, wherein the connected output shaft is used as the second shaft.
[0016]
In the present invention, the torque sensor according to the first or second invention that can detect the rotational torque with high accuracy while having a simple configuration is applied to the steering device of the vehicle, and the rotational torque (steering torque) applied to the steering shaft. This accurate detection value is obtained, and this result is used for various controls such as drive control of a steering assist motor.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a rack and pinion type steering apparatus provided with a torque sensor according to the present invention as a means for detecting steering torque. As shown in the figure, an input shaft (first shaft) 1 connected to a steering wheel (not shown) for steering operation and an output shaft (first shaft) in which a rackion 21 is engaged with a pinion 20 integrally formed at the lower portion. 2 shafts) 2 are connected on the same axis via a torsion bar 3, and these are rotated around the axis by a pair of bearings B ₁ and B ₂ inside a cylindrical housing H partially shown in the figure. A rack and pinion type steering device is configured to be movably supported.
[0018]
The lower end portion (left end portion in the figure) of the input shaft 1 which is a hollow shaft is inserted into a cylindrical portion 22 provided with the upper portion of the output shaft 2 having a larger diameter, and is a short support interposed between the two. The bush 23 is supported on the same axis. The torsion bar 3 is a small-diameter round bar provided with large-diameter connecting portions 3a and 3b at both ends and inserted into the hollow portion of the input shaft 1, and one connecting portion 3a is connected to the upper end of the input shaft 1 (see FIG. And the other connecting portion 3b is splined to a mounting hole formed in the upper end surface of the output shaft 2 to connect the input shaft 1 and the output shaft 2 coaxially. is doing.
[0019]
Thus, when the steering wheel is operated for steering, the input shaft 1 connected to the steering wheel rotates about the axis, and this rotation is applied to the output shaft 2 connected via the torsion bar 3. The rotation of the output shaft 2 is converted into a movement in the axial direction of the rack shaft 21 meshing with the pinion 20, and steering is performed. At this time, the torsion bar 3 is twisted by the action of the steering torque applied to the input shaft 1 via the steering wheel, and a relative angle corresponding to the torsion bar 3 is twisted between the input shaft 1 and the output shaft 2. Displacement occurs.
[0020]
The torque sensor according to the present invention is configured in the vicinity of the connecting portion between the input shaft 1 and the output shaft 2 so as to detect the steering torque through the relative angular displacement as described above, and is connected via a thin support bush 40. A holding cylinder 4 that is externally supported by the input shaft 1, a feed bearing 5 that is internally fitted and held by the holding cylinder 4, and a displacement sensor 6 that is fixed to the housing H so as to face the outside of the holding cylinder 4. It has.
[0021]
As shown in the drawing, the holding cylinder 4 includes a thick cylindrical holding portion 41 and a thin cylindrical connecting portion 42 integrally connected to one side thereof. An engagement groove 43 formed by notching one portion in the circumferential direction with an appropriate width is formed in the connecting portion 42 facing the output shaft 2 side, and an opening is formed in the end surface. The dowel pin 44, which is driven in the axial direction, is closely engaged with the end face of the cylindrical portion 22 at the upper end of the output shaft 2. By this engagement, the holding cylinder 4 including the connecting portion 42 is And can move in the axial direction.
[0022]
On the other hand, the holding portion 41 is formed with a holding hole 45 that opens to the end surface opposite to the connecting portion 42 and is eccentric to a predetermined length on one side with respect to the shaft center. 5 is held internally. The feed bearing 5 is a ball bearing in which a large number of balls are interposed between an inner ring and an outer ring, and an engagement protrusion 50 having a semicircular cross section is provided on the inner peripheral surface of the inner ring as shown in the drawing. Has been.
[0023]
An engagement groove 10 having a semicircular cross-sectional shape corresponding to the engagement protrusion 50 is inclined at a predetermined angle with respect to the axial direction on the outer peripheral surface of the input shaft 1 positioned inside the holding portion 41. The engagement groove 10 has an engagement protrusion 50 provided around the inner periphery of the feed bearing 5. The engagement protrusion 50 is arranged around the input shaft 1 due to the eccentricity with respect to the holding cylinder 4. It is engaged at the directional position.
[0024]
FIG. 2 is an operation explanatory view of the holding cylinder 4 and shows a cross section in a direction orthogonal to FIG. As described above, the holding cylinder 4 engages the engagement groove 43 provided in the connecting portion 42 with the dowel pin 44 provided at the end of the output shaft 2, and rotates integrally with the output shaft 2. It is possible to move in the axial direction. On the other hand, the holding cylinder 4 has an engagement protrusion 50 on the inner periphery of the feed bearing 5 fitted and held in the holding portion 41 engaged with an engagement groove 10 on the outer periphery of the input shaft 1 at point A in the figure. An axial position with respect to the input shaft 1 is determined.
[0025]
Here, when a steering torque is applied to the input shaft 1 and relative angular displacement occurs between the output shaft 2 and the torsion bar 3 due to the action of the steering torque, a holding cylinder that rotates integrally with the output shaft 2 is produced. The feed bearing 5 that is internally fitted and held by 4 is arranged along the engagement groove 10 on the outer periphery of the input shaft 1 in accordance with the relative rotation of the input shaft 1 that occurs as indicated by the arrows in the figure with respect to the output shaft 2. The holding cylinder 4 is pushed in the axial direction in accordance with a change in the position of the engagement point A along the inclination of the engagement groove 10, and is axially moved as indicated by white arrows in the figure. It is displaced to. Since the direction and magnitude of this axial displacement corresponds to the direction and magnitude of the relative angular displacement between the input shaft 1 and the output shaft 2, the input shaft 1 can be detected by detecting the axial displacement of the holding cylinder 4. The steering torque applied to the can be known with high accuracy.
[0026]
In the holding cylinder 4, an annular groove 46 is provided around one part of the outer peripheral surface of the holding portion 41, and the displacement sensor 6 is fixedly supported on the circumference of the housing H facing the outside of the annular groove 46. ing. The displacement sensor 6 is a rotary potentiometer that changes its output in accordance with the rotation angle of the input end that is provided in the housing H in a direction orthogonal to the axis of the displacement sensor 6. A base portion of the detection arm 60 is fixed to the input end, and a distal end of the detection arm 60 extending in the circumferential direction of the holding cylinder 4 is engaged with the annular groove 46 through an engagement protrusion 61. is there.
[0027]
The output of the displacement sensor 6 is given to the arithmetic processing unit 7, and the steering torque applied to the input shaft 1 by the predetermined calculation using the output of the displacement sensor 6 in the arithmetic processing unit 7. Is calculated.
[0028]
FIG. 3 is an operation explanatory diagram of the displacement sensor 6. As described above, the detection arm 60 attached to the output end of the displacement sensor 6 extends in the circumferential direction of the holding cylinder 4 and is engaged with the annular groove 46 on the outer periphery of the holding cylinder 4. With the end as an axis, it can swing in the axial direction of the holding cylinder 4, that is, in a plane substantially parallel to the axial direction of the input shaft 1 and the output shaft 2.
[0029]
Therefore, as shown in FIGS. 3 (a) and 3 (b), when the holding cylinder 4 moves toward both sides in the axial direction, the detection arm 60 swings in the directions indicated by the arrows in the drawing, This swinging causes the output end of the displacement sensor 6 to rotate, and the displacement of the holding cylinder 4 including the direction thereof can be known from the output of the displacement sensor 6 that changes according to this rotation. .
[0030]
The swing angle of the detection arm 60 is proportional to the axial displacement of the holding cylinder 4 when the length is long and the swing radius is sufficiently large. Calculation of the axial displacement of the holding cylinder 4 using the output, that is, calculation of the steering torque is facilitated. However, in this case, the absolute change amount of the swing angle of the detection arm 60 with respect to the relative angular displacement between the input shaft 1 and the output shaft 2 is small, and the relative angular displacement itself is small (about ± 5 °). Therefore, detection with high accuracy is difficult.
[0031]
Therefore, in practice, a relatively short detection arm 60 is used as shown in the figure, and the correspondence between the swing angle of the detection arm 60 and the axial displacement of the holding cylinder 4, that is, the output and detection of the displacement sensor 6. A table showing the correspondence relationship of the target steering torque is prepared in advance, and the calculation processing unit 7 is configured to calculate the steering torque by applying the output of the displacement sensor 6 sequentially taken to the table. Is desirable.
[0032]
As described above, in the torque sensor according to the present invention, the engagement protrusion 50 on the inner periphery of the feed bearing 5 that is fitted and held in the holding cylinder 4 whose rotation is restricted by the output shaft 2 is formed on the outer periphery of the input shaft 1. The relative angular displacement caused by the torsion bar 3 being twisted between the input shaft 1 and the output shaft 2 is converted into the axial displacement of the holding cylinder 4 by being engaged with the engaging groove 10, and the input shaft 1. The applied steering torque is detected.
[0033]
At this time, the axial displacement of the holding cylinder 4 is caused by rolling of the feed bearing 5 using a ball bearing along the inclination of the engaging groove 10, and this rolling occurs in a large number between the inner ring and the outer ring. Therefore, the relative angular displacement between the input shaft 1 and the output shaft 2 is converted without resistance to the axial displacement of the holding cylinder 4, and the detection result of this axial displacement is detected. Based on this, it becomes possible to detect torque with high accuracy.
[0034]
In contrast to the embodiment shown in FIG. 1, the holding cylinder 4 of the feed bearing 5 is connected to the output shaft 1, and an engagement groove 10 is formed on the outer periphery of the output shaft 2. Needless to say, the feed bearing 5 may be engaged. Moreover, it is good also as a structure which provided the some feed bearing 5 in the inside of the holding | maintenance cylinder 4, and engaged these with the common engagement groove | channel or each separate engagement groove | channel.
[0035]
Further, the axial displacement of the holding cylinder 4 is converted into a swing of the detection arm 60 engaged with the annular groove 46 on the outer periphery of the holding cylinder 4 and is detected using an existing displacement sensor 6 such as a rotary potentiometer. The torque can be detected with high accuracy by a simple configuration.
[0036]
As the displacement sensor 6, other sensors for angle detection such as a rotary encoder can be used. Furthermore, a configuration in which a magnet fixed to the outer surface of the holding cylinder 4 is detected by a magnetic sensor (MR sensor), It is good also as a structure which detects the said axial direction displacement directly, such as the structure which detects the label | marker provided in the outer surface of the holding cylinder 4 with a linear scale.
[0037]
In the above embodiment, the use example as the steering torque detecting means in the rack and pinion type steering device has been described. However, the torque sensor according to the present invention can be used in other types of steering devices. As a matter of course, it can be used conveniently as a detection means for the above-mentioned, and further, it can be widely adopted in various industrial fields that require detection of rotational torque.
[0038]
【The invention's effect】
As described above in detail, in the torque sensor according to the first aspect of the present invention, the torque sensor is held eccentrically in a holding cylinder whose rotation is constrained to one of the first shaft and the second shaft that are coaxially connected via a torsion bar. The relative angular displacement between the first and second shafts is converted to the axial displacement of the holding cylinder by a simple configuration in which the feed bearing is engaged with a helical engagement groove formed on the other outer periphery. Since the axial displacement is detected, the rotational torque applied to the first and second shafts can be detected with high accuracy.
[0039]
Further, in the torque sensor according to the second aspect of the present invention, the axial displacement of the holding cylinder is determined based on the swing angle of the swing arm whose tip is engaged with an annular groove provided on the outer surface of the holding cylinder. Since the detection is performed as an intermediary, high-precision torque detection is possible using inexpensive detection means widely used for angle detection, such as a rotary potentiometer.
[0040]
In the steering apparatus according to the third aspect of the present invention, the steering torque applied to the steering shaft that connects the steering wheel and the steering mechanism is detected with high accuracy by the torque sensor of the first aspect or the second aspect. The present invention has an excellent effect such that various controls such as drive control of a steering assist motor performed based on the detection result can be performed with high reliability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a rack and pinion type steering apparatus provided with a torque sensor according to the present invention as a steering torque detection means.
FIG. 2 is an operation explanatory view of a holding cylinder.
FIG. 3 is an operation explanatory diagram of a displacement sensor.
[Explanation of symbols]
1 Input shaft (first axis)
2 Output shaft (second shaft)
3 Torsion bar 4 Holding cylinder 5 Feed bearing 6 Displacement sensor 7 Arithmetic processing section
10 Engaging groove
46 annular groove
50 engaging protrusion
60 detection arm

Claims (3)

In a torque sensor that detects rotational torque applied to a first shaft and a second shaft that are coaxially connected via a torsion bar based on a relative angular displacement caused by twisting of the torsion bar between these two shafts,
A holding cylinder that is constrained to rotate by one of the first shaft and the second shaft and is externally fitted to the other so as to be movable in the axial direction;
An engagement groove formed on the other outer peripheral surface of the first shaft and the second shaft with a predetermined inclination with respect to the axial direction;
A feed bearing which is eccentrically held inside the holding cylinder and has an engaging protrusion provided on its inner peripheral surface engaged with the engaging groove at one circumferential position;
Detecting means for detecting an axial displacement of the holding cylinder that occurs together with the feed bearing due to an inclination of the engagement groove as the feed bearing rolls along the engagement groove. Torque sensor.   The detection means includes a detection arm that engages a tip with an annular groove provided on an outer surface of the holding cylinder and swings in a plane substantially parallel to the axial direction of the first and second shafts; The torque sensor according to claim 1, further comprising means for supporting a base portion of the detection arm and detecting a swing angle thereof.   In order to detect the steering torque applied to the steering wheel for steering the vehicle, the input shaft connected to the steering wheel is the first shaft, and the output shaft connected to the steering mechanism is the second shaft. A steering apparatus comprising the torque sensor according to claim 1.

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