JP2509092B2 - Torque sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque sensor, and particularly to a torque sensor suitable for being applied to an electric power steering device of an automobile.

[Prior art]

2. Description of the Related Art Electric power steering devices for assisting a force for operating a steering wheel of an automobile are being developed. This has a structure in which the torque applied to the steered wheels is detected and the electric motor provided in the steering mechanism is rotated according to the detected torque.

By the way, as this torque detecting means, for example, a torque detecting device disclosed in JP-A-59-208431 is known. FIG. 4 is a partially cutaway perspective view of this torque detection device. A shaft 10 to be measured having a joint structure that meshes two shafts 11 and 12 connected via a spline-fitted torsion bar 16 with a predetermined gap d, and an outer circumference of a connecting portion of the shaft 10 to be measured. Along with covering, a tubular body 15 of a magnetic body fixed to both shafts 11 and 12, and an exciting coil (not shown) arranged outside the tubular body 15 to alternately magnetize the tubular body 15 in a certain direction. , And a detection coil (not shown) that outputs a magnetostrictive component corresponding to torque from the magnetic flux flowing through the tubular body 15.

When the torque acting on the shaft to be measured 10 is relatively small, this torque detecting device causes a twisting moment due to the play existing between the meshing claws 13 and 14 of the shafts 11 and 12 to show the tubular body 15 and the torsion bar 16 as illustrated. It works on the small-diameter portion, and the amount of twist greatly changes with a slight torque change. On the other hand, when the torque is relatively large, the engaging claws 13 and 14 contact each other, and the torsional moment also acts on the tubular body 15 and the small diameter portion of the torsion bar 16 and the shafts 11 and 12. Therefore, the strength with respect to the torsion moment increases rapidly, and the change in the twist amount of the tubular body 15 with respect to the change in torque decreases. Then, at a torque equal to or lower than the torque at which the engaging claws 13 and 14 contact each other, the rate of change in the detection output of the magnetostrictive component is increased to perform accurate detection.

[Problems to be solved by the invention]

By the way, in the torque sensor having such a structure, there is a problem that the inductance of the exciting coil or the detecting coil changes due to temperature change, and accurate torque measurement cannot be performed. In addition, the measurement accuracy may decrease due to the influence of the magnetic flux that strays through the shafts 11 and 12.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a torque sensor capable of highly accurate measurement without being affected by temperature changes and external magnetic flux.

[Means for solving problems]

The torque sensor according to the present invention is made of a magnetic material, which is externally fitted and fixed to one of the two shafts connected via a torsion bar with a gap in the axial length direction to keep the magnetic resistance state unchanged. The first and second cylinders and the second cylinder are externally fitted and fixed to the other of the shafts with a gap in the axial direction of the second cylinder. The relative rotation of the two shafts causes the magnetic resistance between the second cylinder and the second cylinder. The third cylinder made of magnetic material that makes the state of the variable, and the first and second cylinders.
A first cylinder made of a magnetic material, which is arranged so as to form a magnetic circuit with the cylinder and has a first coil wound in a circumferential groove formed on the inner circumference thereof, and second and third cylinders. A second tubular body made of a magnetic material, which is juxtaposed with the first tubular body in the axial direction to form a magnetic circuit, and a second coil is wound around a circumferential groove formed on the inner periphery thereof; A non-magnetic sleeve fitted between the cylinder and the shaft is provided, and the torque applied between the two shafts is temperature-compensated and detected by the difference in the amount of electricity related to the first and second coils. The feature is that it is done.

[Action]

When a rotational torque is applied between two shafts connected via a torsion bar, the torsion bar twists according to the torque, and the second and third cylinders fixed to the different shafts rotate relatively. On the other hand, the facing gaps of the edges of the first and second cylinders fixed to the same shaft do not change, the magnetic resistance state does not change, and the self-inductance of the first coil does not change. On the other hand, the opposing gaps at the edges of the second and third cylinders change due to a slight relative rotation of the shaft, and the state of the magnetic resistance changes significantly, so that the second and third cylinders and the second cylinder body The magnetic flux in the constructed magnetic circuit changes significantly, and the self-inductance of the second coil changes significantly.

The magnetic circuits of the magnetic flux generated by the first and second coils are in the same temperature atmosphere. Therefore, the difference between the outputs of both coils represents the temperature-compensated torque. In order to achieve the purpose of this temperature compensation, the difference between the outputs of both coils when the torque is zero needs to be zero. To this end, when assembling this torque sensor, the gap between the first and second cylinders and / or the gap between the second and third cylinders is adjusted so that the output difference between both coils becomes zero, and then the fixing is performed. To do.

The second cylinder is included in both the magnetic circuit of the magnetic flux generated by the first and second coils, but a non-magnetic sleeve is interposed between the second cylinder and the shaft. Therefore, the magnetic circuit does not spread inward from here, and the stray magnetic flux from the outside that passes through the shaft does not enter the magnetic circuits of the first and second coils, which enables highly accurate measurement.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing its embodiments. FIG. 1 is a half sectional view showing a structure of a torque sensor according to the present invention, and FIG. 2 is a perspective view of an inner member thereof. The input shaft 1 is composed of an upper shaft 1a to which steering wheels (not shown) are attached and a lower shaft 1c to which a pinion (not shown) of a steering mechanism is attached, which are coaxially connected via a torsion bar 1b. The upper shaft 1a is rotatably supported via a bearing 3 in a cylindrical case 2 fixed to the vehicle body.

The outer diameter of the lower end of the upper shaft 1a (left side in the drawing) is small for insertion into the hole in the upper end of the lower shaft 1c (right side in the drawing), and is not on the lower end of the large diameter part of the upper shaft 1a. The first sleeve 4a made of a magnetic material is externally fitted and fixed, and the first and second cylinders 5 and 6 made of a magnetic material are axially slightly separated from each other on the outer periphery thereof and externally fixed to the input shaft 1 concentrically. There is.

The upper and lower edges of the upper first cylinder 5 are planes perpendicular to the axis of the input shaft 1, and all positions in the circumferential direction are of equal length. The lower second cylinder 6 has a top edge that is a plane perpendicular to the axis of the input shaft 1 like the first cylinder 5, but the bottom edge is not perpendicular to the axis, and , Is an asymmetric plane.

That is, in the cylinder 6, the half-circumferential side R1 from one side A to the other side (not shown), which is symmetrical in the radial direction, goes from the portion having the longest axial length of the one side to the other side. The axial length gradually decreases, and the shortest dimension on the other side.
The other half-circumferential side R2 from the other side to the one side A gradually decreases in length from the portion having the longest axial length on the other side toward the one side A, and has the shortest dimension on the one side A. That is, the lower end edge of the cylinder 6 is inclined at the same angle in the same direction with respect to the axis on each of the semicircular sides R1 and R2, and has a ratchet gear-like structure having two tooth portions. Then, on the lower end side of the cylinder 6, a large number of notches 6a are formed at equal intervals in the circumferential direction, the notches 6a having the same width dimension and having the bottom part at the same length position from the upper end edge of the cylinder 6 and parallel to the axis.

A second sleeve made of a non-magnetic material on the upper end of the lower shaft 1c
4b is externally fitted and fixed, and a third cylinder 7 made of a magnetic material is externally fitted and fixed to the outer periphery thereof concentrically with the input shaft 1. This cylinder 7
Has the same shape as the cylinder 6 and is mounted with the vertical direction opposite to the cylinder 6. In addition, at the upper edge of the cylinder 7,
The notch 7a having the same width dimension as the notch 6a formed in
Are formed in the circumferential direction at the same intervals as, and the bottoms of the respective cutouts 7a are located at equal lengths from the lower edge of the cylinder 7. Further, in order to reduce eddy current loss, a large number of narrow grooves 5b, 6b, 7b parallel to the axial direction are arranged side by side on the outer peripheral surfaces of the cylinders 5, 6, 7 in the circumferential direction. These second and third cylinders 6 and 7 are
As shown in Fig. 2 and Fig. 2, they are separated by a predetermined gap,
In addition, the cylinder 6 has the longest axial length and the cylinder 7 has the shortest axial length facing each other so that the cylinders 6 and 7 are engaged with each other. The end faces face each other, and the circumferential edges of the portions where the axial lengths of the cylinders 6 and 7 are the longest face each other.

Then, in the state where no torque acts on the torsion bar 1b, the respective opposed edges are parallel to each other with an appropriate length apart, and the widthwise centers of the cutout portions 6a, 7a of the cylinders 6, 7 are circumferential. They are facing each other with a slight displacement. When the lower end edge of the cylinder 6 and the upper end edge of the cylinder 7 are in contact with each other, the cylinders 6 and 7 are arranged so that the notches 6a and 7a are on the same line.
It is fitted on a and 4b.

Inside the case 2, magnetic body cylinders 8A and 8B having a U-shaped cross section and having a peripheral groove are fitted and fixed. First
The cylindrical body 8A has an axial length dimension capable of straddling the first and second cylinders 5 and 6 so that the center position in the axial direction substantially coincides with the facing position of the cylinders 5 and 6. It is arranged. The second cylindrical body 8B has an axial length dimension that can sufficiently straddle the second and third cylinders 6 and 7, and the central position of the axial length dimension is the axial length direction of the axial lengths of the cylinders 6 and 7. It is arranged so as to substantially coincide with the center.
The first coil 21 is provided in the groove of the first tubular body 8A, and the second tubular body 8B is provided.
A second coil 23 is wound around the groove. The first of these
The coil 21 and the second coil 23 are arranged so as to surround the cylinders 5, 6 and 6, 7.

As a result, the first coil 8A and the second cylinder 8B form the magnetic circuits of the cylinders 5 and 6, respectively, and the second cylinder 8B and the cylinders 6 and 7 of the second coil 23, respectively. These coils 21,23
The number of windings of is appropriate.

FIG. 3 is a block diagram schematically showing an electric circuit of the torque sensor of the present invention. The first coil 21 and the second coil 23 are connected in parallel to form a closed circuit.
Oscillator 22 is connected to. One side 22a of the oscillator 22 and the first
Of the coil 21 is connected to the first rectifying / smoothing circuit 24 at one side 21a, and the one side 22a of the oscillator 22 is connected to the first side 23a of the second coil 23 at the connection intermediate point. It is connected to the rectifying / smoothing circuit 25 of 2. First and second rectifying / smoothing circuit
The outputs of 24 and 25 are applied to the differential amplifier 26. The output of the differential amplifier 26 is used as the torque output.

 Next, the operation of the torque sensor of the present invention will be described.

The magnetic flux generated in the first coil 21 and the second coil 23 by the oscillation operation of the oscillator 22 is linked to the cylinders 5, 6 and 6, 7.
A voltage is induced in the coils 21 and 23.

The number of turns of the first and second coils 21 and 23 is made equal, and the cylindrical body 8A
Also, even if the magnetic resistance of the magnetic circuit formed by the cylinders 5 and 6 and the magnetic resistance of the cylindrical body 8B and the magnetic circuit formed by the cylinders 6 and 7 are set to the same level in design, the first and second coils 21 and 23 of the first and second coils 21 and 23 in the state of no torque It is practically difficult to make the outputs equal. Therefore, when the parts are assembled in the state shown in FIG. 1, the gap between the cylinders 5 and 6 and / or the gap between the cylinders 6 and 7 is provided as a circuit connection shown in FIG. 3 under the condition that no torque acts on the torsion bar 1b. Is adjusted so that the output difference between the coils 21 and 23 becomes zero, and the cylinders 5, 6 and 7 are fixed on the output difference. By thus balancing the magnetic circuit, high accuracy is ensured.

It should be noted that the complementary balance adjustment electrically performed after the circuit connection as shown in FIG. 3 is also effective for further improving the accuracy or for correcting the imbalance on the wiring.

The torque sensor of the present invention is used with the outputs thus balanced.

As shown in FIGS. 1 and 2, when the upper edge (or lower edge) of the cylinder 7 (or 6) is an inclined surface that is displaced upward (or downward) in the clockwise (or counterclockwise) direction. When the steered wheels are rotated in the clockwise direction (solid arrow direction), the cylinder 6 rotates in the clockwise direction relative to the cylinder 7 by the action of the torsion bar 1b, and the lower end edge of the cylinder 6 rotates.
The facing interval with the upper edge of the cylinder 7 is shortened, and the notch
The facing area between 6a and 7a increases. As a result, cylinders 6 and 7
And the magnetic resistance between them becomes small, and the output voltage of the second coil 23 becomes high. On the other hand, since the magnetic resistance with the first coil 21 does not change, the output voltage of the first coil 21 is constant, so that the output of the differential amplifier circuit 26 has a positive value corresponding to the relative rotation difference described above. It becomes a value.

On the other hand, when the steered wheels are rotated in the counterclockwise direction (the direction of the broken arrow), the facing distance between the lower end edge of the cylinder 6 and the upper end edge of the cylinder 7 increases and the facing area between the cutouts 6a and 7a decreases.
Contrary to the case described above, the magnetic resistance becomes large and the output of the differential amplifier circuit 26 becomes a negative value corresponding to the relative rotation amount.

Since the relative rotation amount is determined by the rotation torque applied to the input shaft 1 by the steered wheels, the torque can be detected by the output of the differential amplifier circuit 26 in the end.

The magnetic flux generated in the first coil 21 flows through the closed magnetic path formed by the first cylindrical body 8A and the first and second cylinders 5 and 6, and
Since the magnetic flux generated in the coil 23 flows through the closed magnetic circuit formed by the second cylindrical body 8B and the second and third cylinders 6 and 7, the respective speeds do not interfere with each other. Even if a magnetic flux due to an external magnetic field flows through the input shaft 1, it does not enter the magnetic circuits of the first coil 21 and the second coil 23 due to the presence of the non-magnetic material sleeves 4a and 4b.

Thus, by the relative rotation of the cylinders 6 and 7,
The facing distance between the axial edges and the facing positions of the notches 6a and 7a change, and the magnetic resistance state between the cylinders 6 and 7 changes significantly. Therefore, even if the relative rotation amount is small, the torque detection signal greatly changes according to the change of the rotation torque.

By forming the notches 6a, 7a and the grooves 6b, 7b, the magnetic flux flowing in the cylinders 6, 7 blocks the flow path of the eddy current flowing in the circumferential direction to reduce the eddy current loss and reduce the loss of heat, etc. Decrease.

Separately from this, even when the temperature of the first coil 21 and the second coil 23 changes, as long as the respective coils 21 and 23 have the same temperature, the influence on the output change is equal, so the output of both Temperature compensation can be performed by obtaining the difference between

The shape of the opposing edges of the cylinders 6 and 7 made of a magnetic material is not limited to the above-mentioned embodiment, and the magnetic resistance with the second coil 23 can be changed by the relative rotation thereof. In other words, it is sufficient if it is not center-symmetric with respect to the axis of the input shaft 1.

The torque sensor of the present invention is not limited to the electric power steering device of an automobile, but can be widely and generally used. It goes without saying that it can also be applied to the measurement of the rotation amount itself.

〔The invention's effect〕

According to the present invention as described above, due to the magnetic flux generated by the first coil, the magnetic circuit (first, second cylinder and first cylinder) and the magnetic flux generated by the second coil are generated. A magnetic circuit (second, third cylinder, and second cylinder) is provided for the purpose of determining the torque by the amount of electricity related to these first and second coils. Alternatively, unlike the case of using a magnetic circuit, it is possible to compensate for the effect of temperature that the two coils or the magnetic circuit receive equally, and it is possible to improve the measurement accuracy.

In addition, the magnetic circuit provided for temperature compensation and the magnetic circuit for torque detection can be balanced by adjusting the gap between the cylinders 5 and 6 and / or the gap between the cylinders 6 and 7. Accuracy measurement is ensured.

In addition, the stray magnetic flux from the shaft can be blocked by the sleeve made of a non-magnetic material, and the accuracy can be improved in this respect as well.

Further, since the present invention detects a change in the self-inductance of the coil due to a change in the magnetic resistance of the magnetic circuit, in contrast to the conventionally known method for detecting the leakage magnetic flux (for example, Japanese Patent Laid-Open No. 62-247220). The present invention has excellent effects such as high sensitivity and high S / N ratio.

[Brief description of drawings]

FIG. 1 is a half sectional view showing the structure of a torque sensor according to the present invention, FIG. 2 is a perspective view showing the internal structure thereof, and FIG. 3 is a block diagram schematically showing an electric circuit of the torque sensor of the present invention. FIG. 4 is a partially cutaway perspective view of a conventional torque sensor. 1 …… input shaft, 1a …… upper shaft, 1b …… torsion bar,
1c …… Lower shaft, 5,6,7 …… Cylinder, 6a, 7a …… Notch, 5b, 6
b, 7b ... Groove, 21 ... First coil, 22 ... Oscillator, 23 ...
... second coil

Front Page Continuation (72) Inventor Takuchi Kyoya 2 Nishinomachi Nishinomachi, Minami-ku, Osaka City, Osaka Prefecture Mitsuyo Seiko Co., Ltd. (56) Reference JP 62-247220 (JP, A) Patent 161799 (JP) , C1)

Claims (1)

(57) [Claims] 1. A first and a first member made of a magnetic material, which is externally fitted and fixed to one of two shafts connected via a torsion bar with a gap in the axial length direction to make the magnetic resistance state invariable. The second cylinder and the second cylinder are externally fitted and fixed to the other of the shafts with a gap provided in the axial direction between the second cylinder and the second cylinder, and the relative rotation of the two shafts causes a state of magnetic resistance with the second cylinder. The third cylinder made of a variable magnetic material and the first and second cylinders are arranged to form a magnetic circuit, and the first coil is wound around the circumferential groove formed on the inner circumference of the first and second cylinders. The first cylinder made of a magnetic material and the second and third cylinders are juxtaposed in the axial direction with the first cylinder to form a magnetic circuit. A second cylindrical body made of a magnetic material wound with two coils, and a sleeve made of a non-magnetic material fitted between the cylinder and the shaft,
A torque sensor characterized in that the torque applied between the two shafts is temperature-compensated and detected by the difference in the amount of electricity associated with the first and second coils.