JP2001065537A - Drive shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a space saving and low cost drive shaft capable of detecting torque with a high precision. SOLUTION: A torque detecting part 6 is provided in an outer periphery of a stem part 2b of an inboard side constant velocity joint 2. The torque detecting part 6 is composed of multiple rows of magnetostrictive films 6a formed on the outer peripheral surface of the stem part 2b of the constant velocity joint 2 and a torque detector 6b placed with facing to the magnetostrictive films 6a in non-contacting condition. The magnetostrictive film 6a is formed of a belt-like magnetostrictive material to be arranged at a same interval in the circumferential direction with being tilted relative to the axial direction. Since a magnetic characteristic of each magnetostrictive film 6a is changed when torque is applied thereto, torque of the drive shaft 1 can be detected under a non-contacting condition when a change in magnetic permeability is detected by the detector 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive wheel axle, that is, a drive shaft, which functions to transmit the power of an automobile engine to wheels. The drive shaft includes a front axle of a front wheel drive vehicle, a rear axle of a rear wheel drive vehicle, and all axles of an all wheel drive vehicle.

[0002]

2. Description of the Related Art In a drive shaft of an automobile employing an independent suspension type suspension, it is necessary to transmit a driving force while following the movement of the suspension. For this reason, one end of the drive shaft is connected to a differential via a constant velocity joint, and the other end is connected to an axle via a constant velocity joint. In this way, the drive shaft is incorporated in a drive system that transmits the power of the engine to the wheels, and the power of the engine is finally transmitted to the wheels by the drive shaft.

[0003] In recent automobiles, electronic control technology has been introduced in all parts, such as an antilock brake system (ABS) and a traction control system (TC).
S), a wheel speed signal is used in running control such as non-slip differential (LSD). For this purpose, the drive shaft usually has an AB on the outboard side (axle side).
An S (anti-lock brake system) control pulsar ring is provided. When the gear-shaped pulsar ring rotates with the rotation of the wheels, a frequency proportional to the number of wheel rotations is supplied to an electromagnetic pickup installed on the vehicle body in proximity to the pulsar ring. Pulse is generated. As another example, there is one in which a magnetic sensor is built in the hub unit to generate a pulse having a frequency proportional to the wheel rotation speed.

[0004] By the way, in recent automobiles, there is a strong demand for real-time detection of not only the above-mentioned wheel rotational speed but also the rotational torque of the drive shaft in order to further optimize travel control. Detecting the torque of the drive shaft can be used, for example, for optimal distribution of the drive torque to each wheel during running on snowy roads or heavy rain, and braking torque control (brake control) of each wheel during deceleration. This can contribute to further improvement of vehicle stability.

In order to detect the torque applied to the drive shaft, for example, as disclosed in Japanese Patent Application Laid-Open No. 07-63628, a pulsar ring is attached to each of outer rings of constant velocity joints attached to both ends of the drive shaft, and the phase difference of the signal is detected. Calculating the torque applied to the drive shaft from the motor, or as disclosed in Japanese Patent Application Laid-Open No. 62-157542, an exciting coil wound around the shaft at a predetermined interval in the longitudinal direction of the shaft and provided in the circumferential direction of the shaft. There is known a device in which a detection coil wound in the length direction of a shaft is provided therebetween, and torque is measured from a voltage generated in the detection coil due to magnetic distortion caused by twisting of the shaft.

[0006]

However, the structure disclosed in Japanese Patent Application Laid-Open No. 07-63628 has a problem in accuracy at low torque. On the other hand, the structure disclosed in Japanese Patent Application Laid-Open No. 62-157542 requires a contact-type brush or the like to extract a signal because the detection coil rotates together with the shaft. Further, since two excitation coils and a detection coil are required, the required space is increased, the cost is increased, and the wiring is complicated.

An object of the present invention is to solve the above-mentioned problems in a conventional drive shaft having a torque detecting function.

[0008]

A drive shaft according to the present invention is connected to a drive system of an automobile, and has a torque detecting portion formed by forming a plurality of belt-shaped magnetostrictive films on the outer periphery of a shaft portion with respect to the axis. Things. The so-called magnetostrictive torque sensor formed by tilting the magnetostrictive film with respect to the axis,
It detects the amount of torque based on the change in the magnetic permeability in the part to be detected, and has the advantages of a simple structure, high sensitivity to low torque, and high operation stability due to non-contact. Therefore, by using this kind of sensor as the torque detecting unit of the drive shaft, not only the drive control can be further optimized, but also stable control can be performed for a long time, and further, the weight of the drive shaft is increased and the structure around the axle is improved. Can be suppressed from becoming complicated.

By providing the torque detector on the inboard side of the constant velocity joint, high-precision torque detection can be performed without being affected by the rotational gap (play) of the constant velocity joint.

The magnetostrictive film can be formed of a giant magnetostrictive material.

[0011] The torque detector can be provided, for example, on an intermediate shaft of the drive shaft. The “intermediate shaft” here refers to a shaft-like member of the drive shaft excluding the constant velocity joint, and is disposed, for example, between the differential and the inboard side constant velocity joint. In addition to the intermediate member, a torque detector may be provided on the outer ring stem of the constant velocity joint.

By providing the torque detector with a function of detecting the number of revolutions, the unit for detecting the torque and the unit for detecting the number of revolutions can be integrated, and the link between the torque signal and the number of revolutions signal can be achieved. It is possible to further optimize the traveling control. Further, compared to the case where these units are individually provided, cost reduction and space saving can be achieved.

If the rotation speed is detected based on the difference in the magnetic permeability between the magnetostrictive film and the surface material between the magnetostrictive films, the rotation speed can be detected with high accuracy as in the torque detection. Simple structure and low cost.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a case where constant velocity joints 2 and 3 are used as a drive shaft 1. The drive shaft here means a drive axle (including constant velocity joints 2 and 3) that transmits power from the final reduction gear device 4 (differential) to the drive wheels. The illustrated drive shaft 1 has constant velocity joints 2, 3 at both ends of a first intermediate shaft 5.
And connected to the drive system of the vehicle via constant velocity joints 2 and 3 at both ends. In this embodiment, the inboard side of the drive shaft 1 is connected to a differential 4 by a double offset type slide joint 2 and the outboard side is connected to an axle (not shown) by a barfield type fixed constant velocity joint 3. Is done.

Incidentally, the constant velocity joints 2 and 3 at both ends of the drive shaft 1 are not limited to the combination as shown in the illustrated example.
For example, in the case of a front axle of a front wheel drive vehicle, that is, a drive wheel front axle, since the front wheels are steered, the wheel side joint is required to have a large operating angle and uniform velocity. In order to satisfy this requirement, a barfield type fixed joint (Zeppa type fixed joint), a tripod type fixed joint, and the like are used. The joint on the vehicle body side is required to have an operating angle that allows the suspension to move. Although this operating angle is not as large as the wheel-side joint, it is necessary to allow the length of the vehicle body to change with the movement of the suspension. For this reason, a bar field type slide joint, a tripod type slide joint, a cross glove type joint, or the like is used as the vehicle body side joint. Since the independent suspension type rear axle of the drive wheel does not require a steering function and does not require a large operating angle, a cardan joint may be used in some cases.

Stem of inboard side constant velocity joint 2
A torque detector 6 is provided on the outer circumference of 2b. As shown in FIG. 2, the torque detector 6 includes a plurality of magnetostrictive films 6a formed on an outer peripheral surface of a shaft-like stem portion 2b, and a torque disposed in a non-contact state facing the magnetostrictive films 6a. And a detector 6b.

The magnetostrictive films 6a are formed of a strip-shaped magnetostrictive material, and are arranged at equal intervals in the circumferential direction while being inclined with respect to the axial direction. In the present embodiment, the rows of the magnetostrictive films 6a are provided at two places separated in the axial direction, and the tilt angle of each row is set to, for example, ± 45 ° with the tilt direction reversed. As a method of patterning the magnetostrictive film 6a, after forming a groove inclined at a predetermined angle with respect to the axial direction, a method of spraying a magnetostrictive material on this groove, or forming a similar pattern on a magnetic ribbon such as an amorphous alloy After that, there is a method of bonding to the shaft surface. Magnetostrictive materials include Fe-Ni alloys and Fe-Co alloys. In place of these magnetic materials, a giant magnetostrictive material (having a deformation of 0.1% or more in a magnetic field) is sprayed. Is also good. Examples of the giant magnetostrictive material include rare earth thiobium Tb and dinadium Dy, and a mixture of these powders and Fe powder is used for thermal spraying.

The torque detector 6b is formed of, for example, a coil that circumscribes the outer periphery of the magnetostrictive film 6a in the circumferential direction, and is disposed at two positions in the axial direction so as to face each of the rows of the magnetostrictive film 6a.
The bobbin 6c of the coil 6b is fixed to the main body cover 4a of the differential 4. A seal 6d is attached to the bobbin 6c to prevent foreign matter from entering the inner peripheral portion of the bobbin 6c.

The material of the shaft portion (stem portion 2b in the present embodiment) forming the magnetostrictive film 6a is not limited as long as it can transmit strain stress to the magnetostrictive film 6a accurately regardless of magnetic permeability or electric resistance. It can be arbitrarily selected in consideration of other design conditions such as sufficient mechanical strength and cost.

When a torque is applied to the stem 2b of the drive shaft 1, a tensile stress or a compressive stress acts on each of the patterned magnetostrictive films 6a. Accordingly, the magnetic characteristics of each magnetostrictive film 6a change. Therefore, if a change in magnetic permeability is detected using the circuit illustrated in FIG. 3, it is possible to detect torque in a non-contact manner. In the above embodiment, the magnetostrictive films 6a are provided in two rows, and the tilt directions of the magnetostrictive films 6a in both rows are reversed, so that if the magnetic permeability in one axial pattern increases, the other pattern in the other pattern. The permeability decreases. Therefore,
If the difference between the two is output by the differential amplifier, torque measurement with high resolution and high accuracy can be performed. If there is no particular problem, the magnetostrictive films in one row may be omitted and the torque measurement may be performed using a single-row magnetostrictive film. In this case, only one torque detector 6b is sufficient. The torque signal detected in this manner can be used for engine control for traction control, control of AT transmission, or control of drive torque and braking torque of an electronic control LSD or the like.

By using the torque detecting portion 6 having the inclined band-shaped magnetostrictive film 6a as described above, it is possible to provide the drive shaft 1 with a torque detecting function with a simple structure and low cost, and the torque can be detected. It can be performed with high accuracy. In addition, by providing the torque detector 6 on the inboard side of the inboard side constant velocity joint 2 (inboard side of the torque transmitting ball) of the drive shaft 1 as described above, the circle in the constant velocity joint 2 is formed. There is no influence of the mechanical play in the circumferential direction, and it is possible to perform highly sensitive torque detection.

FIG. 4 shows a torque detector 6 arranged on the outer periphery of a second intermediate shaft 7 between the differential 4 and the inboard constant velocity joint 2. The structure and function of the torque detector 6 are as described above. This is the same as in the case of FIGS. The second intermediate shaft 7 is an outer ring 2a of the inboard-side constant velocity joint 2.
And is configured separately. One end of the second intermediate shaft 7 is connected to the side gear 4b of the differential 4, and the other end is connected to the constant velocity joint 2 by fixing the flange provided at the end to the flange of the outer ring 2a.

The torque detecting section 6 can be provided with not only the torque detecting function but also a rotational speed detecting function. FIG. 5 shows an example of this, in which a gear-shaped pulsar ring 6e is mounted on the outer peripheral surface of the stem 2b, and an electromagnetic pickup 6f is provided on the inner periphery of the bobbin 5 opposed to the ring. This is to detect a pulse having a proportional frequency.

FIG. 6 shows another example of the torque detecting section 6 having both a torque detecting function and a rotational speed detecting function. The torque detector 6g for detecting the magnetic permeability of the magnetostrictive film 6a detects the magnetic permeability of the drive shaft 1. This is to measure the number of rotations of. The above detector 6g,
Like the torque detection detector 6b, it is composed of a coil, a magnetic head (a coil in this embodiment), and the like.

Detector 6g for rotation speed measurement (detection coil)
Is mounted on the inner peripheral portion of the bobbin 6c so as to face the magnetostrictive film 6a in one row, for example, the row on the outboard side. In the present embodiment, as shown in FIG. 7A, a case where two detection coils 6g are arranged with a phase difference of 90 ° in the circumferential direction is illustrated, but only one detection coil may be used.

The output signal of both detection coils 6g is shown in FIG.
And a pulse signal proportional to the number of rotations. That is, when the drive shaft 1 rotates, an induced current is generated in the two detection coils 6g due to a difference in magnetic permeability between the magnetostrictive portion 6a and the surface material (base material of the stem portion 2b) between the magnetostrictive portions 6a. As shown in FIG. 7 (c), the amplitude of the signal changes in each system (A, A ′).
Part signal). This signal is converted into a rectangular wave through a rectifier, a low-pass filter, and a comparator (C and C 'part signals), then edges are detected (D and D' part signals), and the signals of both systems are logically ORed (E Signal), and a pulse proportional to the number of rotations is obtained. This pulse signal is input to, for example, an ABS control device as a rotation speed signal. As described above, the resolution of the rotation speed signal can be improved by arranging the plurality of detection coils 6g with shifted phases or detecting the edges of the rectangular wave.

It should be noted that a pulse proportional to the number of rotations can be obtained similarly by replacing the resistor in FIG. 7B with a capacitor and detecting a difference in magnetic permeability as a resonance circuit.

[0029]

As described above, according to the present invention, the torque of the drive shaft can be detected with a simple structure with high accuracy and high sensitivity. Therefore, when mounted on a car,
Further optimization of various traveling controls can be achieved, and stable control can be performed for a long period of time. Further, the increase in the weight of the drive shaft and the complexity of the structure around the axle can be minimized.

Further, by providing the torque detector with a function of detecting the number of revolutions, the torque signal and the number of revolutions signal can be utilized for various vehicle traveling controls.

[Brief description of the drawings]

FIG. 1 is a sectional view of a drive system including a drive shaft according to the present invention.

FIG. 2 is an enlarged sectional view of a torque detector.

FIG. 3 is a circuit diagram of a torque detection circuit.

FIG. 4 is a cross-sectional view showing another embodiment of the drive shaft.

FIG. 5 is a sectional view showing another embodiment of the drive shaft.

FIG. 6 is a sectional view showing another embodiment of the drive shaft.

7A is a cross-sectional view of a rotation speed detection means, FIG. 7B is a circuit diagram of a rotation speed detection circuit, and FIG. 7C is a diagram showing signal waveforms in the detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive shaft 2 Constant velocity joint (inboard side) 2b Stem part 3 Constant velocity joint (outboard side) 4 Differential 6 Torque detector 6a Magnetostrictive film 6b Torque detector 6g Rotational speed detector 7 Intermediate shaft (second intermediate shaft) )

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Koike 1578 Higashikaizuka, Iwata-shi, Shizuoka F-term in NTN Corporation (reference) 2F051 AA01 AB05 BA03 3J033 AA01 BA15

Claims (8)

[Claims] 1. A drive shaft which is connected to a drive system of an automobile and has a torque detecting portion formed on a shaft outer periphery with a plurality of belt-shaped magnetostrictive films inclined with respect to an axis. 2. The drive shaft according to claim 1, wherein the torque detector is provided on the inboard side of the constant velocity joint. 3. The drive shaft according to claim 1, wherein said magnetostrictive film is formed of a giant magnetostrictive material. 4. The drive shaft according to claim 1, wherein the torque detector is provided on an intermediate shaft. 5. The drive shaft according to claim 4, wherein the intermediate shaft is disposed between the differential and the inboard constant velocity joint. 6. The drive shaft according to claim 1, wherein the torque detector is provided on an outer ring stem of the constant velocity joint. 7. The drive shaft according to claim 4, wherein the torque detector has a function of detecting a rotation speed. 8. The rotation speed is detected based on a difference in magnetic permeability between the magnetostrictive film and a surface material between the magnetostrictive films.
Drive shaft as described.