JPH1026565A - Torque measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the torque measuring device having a torque switch, which can detect the state of the zero torque in high sensitivity. SOLUTION: This is the torque measuring device, wherein a torque sensor is provided at a steering shaft 4 for transmitting the torque. A first engaging part 18 is provided at one-end side of the steering shaft 4, and a second engaging part 19 is provided at the other-end side at the same time. These first and second engaging part 18 and 19 are arranged so as to face each other. Facing surfaces 20A, 20B, 21A and 21B are constituted so that gaps 25A and 25B are mutually held at the non-transmitting time of the torque and the gaps 25A and 25B are closed at the transmitting time of the torque. A pair of or two-pairs of magnetic heads 27A, (27B), 28A and (28B), which detect the presence or absence of the application of the torque on the steering shaft by sensing the magnitudes of the gaps 25A and 25B, are provided furthermore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque measuring device, and more particularly to a torque measuring device used for a power steering device of a self-propelled vehicle such as an automobile, a forklift or an electric cart.

[0002]

2. Description of the Related Art Conventionally, an electric power steering device is used in a small vehicle such as a mini vehicle. This electric power steering device is provided with a torque sensor. As the torque sensor, a combination of a torsion bar and an angle sensor is generally used. As the angle sensor, a sensor composed of a potentiometer, a resolver, or the like is generally used.

[0003] However, in such a conventional configuration, the torsion bar has a relatively low torsional rigidity, so that there is a problem that an unnatural soft feeling is generated in the steering wheel during high-speed running with a small amount of power assist. For this reason, a torque sensor having a high torsional rigidity is required for adopting the electric power steering in a relatively large vehicle such as an ordinary passenger car. As such a high-rigidity torque sensor, a magnetostrictive torque sensor is preferable.

On the other hand, in an electric power steering apparatus for an automobile, the measurement control torque range is 10 Nm.
Despite the degree, when riding on a curb or in the event of a vehicle collision, 300 Nm from the tire side to the steering wheel side
Very large overloads of the order can be applied.

[0005]

However, the above-described magnetostrictive torque sensor has a demerit that if the shaft diameter is increased to increase the overload resistance, the sensitivity is reduced in inverse proportion to the cube of the shaft diameter. Therefore, when using a magnetostrictive torque sensor, it is necessary to adjust the sensitivity and the overload resistance.

That is, in general, the magnetostrictive torque sensor has low sensitivity, and if the shaft diameter is increased in order to provide an overload resistance, the sensitivity is further reduced, and there is a possibility that the instability of the zero point becomes a problem relatively.

In order to eliminate such instability of the zero point, it is preferable to detect the state of zero torque by, for example, a torque switch and correct the zero point of the torque sensor in real time based on this.

Accordingly, an object of the present invention is to provide a torque measuring device provided with a torque switch capable of detecting a state of zero torque with high sensitivity.

[0009]

According to the present invention, there is provided a torque measuring apparatus having a torque transmission shaft provided with a torque sensor, wherein a first engagement portion is provided at one end of the torque transmission shaft. A second meshing portion is provided on the other end side, and the first and second meshing portions are arranged so as to face each other, and their opposing surfaces are positioned with a gap therebetween when torque is not transmitted. At the same time, the magnetic head is configured to be positioned so as to close the gap when transmitting torque, and to detect the magnitude of the gap to detect the presence or absence of application of torque to the torque transmission shaft. is there.

That is, recording of information on a magnetic recording medium
In general magnetic heads used for reproduction, if there is an air gap between the magnetic head and the medium, a lift-off state occurs and the output from the magnetic head decreases, so consideration has been given to avoid this state. On the other hand, the present invention detects the application of torque to the transmission shaft by utilizing the relationship between the magnetic head and the air gap. In addition, since the presence or absence of the application of torque to the transmission shaft is detected by detecting the size of the air gap, that is, the size of the gap using the magnetic head, the output of the magnetic head can be detected only by a small change in the size of the gap. And the presence or absence of torque transmission can be detected with high sensitivity.

Further, according to the present invention, a first magnetic head is provided at a first meshing portion, and a second magnetic head facing the first magnetic head is provided at a second meshing portion; Means for exciting the magnetic head and means for extracting the output of the second magnetic head.

According to such a configuration, the first magnetic head and the second magnetic head face each other, and one is set as the excitation side and the other is set as the detection side. The presence or absence of the application of torque can be detected with higher sensitivity.

[0013]

FIG. 9 shows a schematic configuration of an electric power steering device to which a torque measuring device according to the present invention is applied. Here, reference numerals 1 and 1 denote a pair of steering wheels in a vehicle such as an automobile, which are configured to be simultaneously steered by a tie rod 2. Reference numeral 3 denotes a steering wheel operated by a driver so that an operation force applied to the steering wheel 3 is transmitted to a gear box 5 for operating the tie rod 2 via a steering shaft 4 as a torque transmission shaft. It is configured. The gear box 5 is provided with a motor 6 for power steering. The steering shaft 4 is provided with a torque sensor 7 capable of detecting the direction and magnitude of the torque acting on the steering shaft 4 and a torque switch 8 capable of detecting whether or not torque is applied to the steering shaft 4. . The motor 6, the torque sensor 7, and the torque switch 8 are all connected to the electronic control unit 9.

FIG. 8 shows a main part of the steering shaft 4 in an enlarged manner. The steering shaft 4 is covered by an outer cylinder 11 and is supported by the vehicle body by the outer cylinder 11. The upper end of the steering shaft 4 projects from the outer cylinder 11, and a handle mounting portion 12 is formed at the end of the projection.

The torque sensor 7 includes a pair of magnetic anisotropic parts 13 and 13 inclined in opposite directions to each other.
Excitation coil and detection coil 1 provided around 3, 13
4 and has.

The steering shaft 4 is supported by bearings 15 and 16 at the upper end and the lower end of the outer cylinder 11, respectively. The torque switch 8 is provided at a position near the bearing 15, and in this torque switch 8,
The steering shaft 4 is divided in the length direction, and one end side of the steering shaft 4, that is, an upper portion close to the handle 3, and another end portion, that is, a lower portion far from the handle 3, of the divided portion are respectively provided. Meshing portions 18 and 19 are formed.

As shown in FIG. 2, these meshing portions 18 and 19 are each formed in a half-moon cross section,
20A and 21A and the opposing surfaces 20B and 21B are configured to face each other. A thin shaft 22 is integrally formed at the tip of the lower engagement portion 19 remote from the handle 3, and the thin shaft 22 passes through the center of the upper steering shaft 4 closer to the handle 3. It reaches the position of the handle mounting portion 12, and is concentrically supported inside the steering shaft 4 by a bearing 23 at or near the handle mounting portion 12. Therefore, the steering shaft 4 is supported by the bearings 15 and 24 while the steering shaft 4 is supported by the bearings 15 and 24 in spite of the fact that the steering shaft 4 is divided in the lengthwise direction at the meshing portions 18 and 19 as described above. The tip of the fine shaft 22 is a bearing
Bearing supported by 23 and opposite the small shaft 22
The shaft 4 is supported by the outer cylinder 11
It is rotatable while being supported stably.

As shown in FIG. 2, the opposing surfaces 20A, 20B and the opposing surfaces 21A, 21B are each formed so as to have an angle slightly smaller than 180 degrees.
A and the opposing surface 21A, and between the opposing surface 20B and the opposing surface 21B
Are formed between the gaps 25A and 25B at a slight angle along the circumferential direction. For example, when a torque in a certain direction is applied to the steering shaft 4 in FIG. 2, one gap 25A is opened and the other gap 25B is closed. When a torque in the opposite direction is applied, the gap 25A is closed and the gap 25A is closed.
25B will open. When torque is not applied to the steering shaft 4 by providing elastic bodies 26A and 26B such as springs made of a non-magnetic material between the opposing surfaces 20A and 21A and between the opposing surfaces 20B and 21B, respectively. Gaps 25A and 25B can be reliably formed, and
Despite the presence of 25A and 25B, it is possible to reliably transmit torque even near zero torque, thereby eliminating the dead zone near zero torque.

In FIG. 2, an example is shown in which the opposing surfaces 20A and 20B of the engaging portion 18 and the opposing surfaces 21A and 21B of the engaging portion 19 are both formed at an angle slightly smaller than 180 degrees. Opposing surfaces 20A and 20B and opposing surfaces 21A and 21
One of B and 180 may be formed at 180 degrees, and the other may be formed at less than 180 degrees.

Magnetic heads 27A, 27B, 28A, 28B are embedded in the opposing surfaces 20A, 20B, 21A, 21B, respectively. In detail, the counter surface 20
Holes 29A, 29 toward A, 20B, 21A, 21B
B, 30A, 30B are formed, and the holes 29A, 29B, 30
The magnetic heads 27A, 27B, 28A, 28B are inserted into A, 30B, and are fixed by the resin mold 31 so that the heads are located along the opposing surfaces 20A, 20B, 21A, 21B. The magnetic heads 27A and 28A face each other while approaching each other via a gap 25A.
28B are installed so as to face each other in a state of approaching each other via a gap 25B.

As shown in FIG. 1 and FIG.
The shaft 4 and the outer cylinder 11 corresponding to 18 have a magnetic head
A detection-side rotary transformer 32 connected to 27A and 27B is provided. A rotary transformer 33 on the excitation side, which is connected to the magnetic heads 28A and 28B, is provided on the shaft 4 and the outer cylinder 11 corresponding to the meshing portion 19. FIG.
FIG. 3 shows a circuit diagram of the torque switch 8. The rotary transformer 33 is connected to an AC excitation circuit 34 outside the outer cylinder 11. The rotary transformer 32 is connected to a subtractor 36 via a rectifier circuit 35 using a capacitor outside the outer cylinder 11. The windings of the magnetic heads 27A and 27B are made to have opposite polarities as shown in FIG.
The configuration is such that the difference between the outputs of B can be taken.

Therefore, the magnetic heads 28A and 28B have
An excitation current is supplied from an excitation circuit 34 via a rotary transformer 33. The magnetic heads 27A and 27B are
A and 28B are close to and opposed to each other, so that a detection voltage is generated by electromagnetic induction. This detection voltage is supplied to the subtractor 36 via the rotary transformer 32 and the rectifier circuit 35.

In such a configuration, no torque is applied to the steering shaft 4, and therefore, the air gap, that is, the gaps 25A and 25B are formed, so that the meshing portion is formed.
The opposing surfaces 20A, 20B of the 18 and the opposing surface 21A of the projection 19,
When there are large gaps 25A and 25B between the magnetic heads 21B and 21B, the detection voltage generated in the magnetic heads 27A and 27B by the electromagnetic induction is small, and the value of the detection output voltage from the subtractor 36 is small. . On the other hand, the steering shaft 4
When torque is applied to one of the gaps 25A and 25B and the gap is clogged, the detection voltage of the magnetic head 27A or 27B which has the gap 25A or 25B clogged increases, and the corresponding subtraction is performed. The detection voltage of the detector 36 also increases.

FIG. 4 shows the relationship between the size of the gaps 25A and 25B for one of the magnetic heads 27A and 27B and the output of the subtractor 36.
Shown in 4, the output of the subtractor 36 changes based on the size of the gaps 25A and 25B based on the presence or absence of the application of the torque to the steering shaft 4.
It can be seen that the output of the subtractor 36 increases as A and 25B decrease. Voo indicates the output of the subtractor 36 when the opposing surfaces 20A, 20B and the opposing surfaces 21A, 21B come into contact with each other. Therefore, an appropriate threshold value Vth is set and the subtractor
When the output of 36 is equal to or less than the threshold value Vth, it can be determined that the torque is zero. By doing so, the relationship between the applied torque and the output of the system including both magnetic heads 27A and 27B can be made as shown in FIG. Can be.

Moreover, the magnetic head 27A of the engagement portion 18
Since the magnetic head 27B and the magnetic heads 28A and 28B of the meshing portion 19 are arranged so as to face each other, even if the size of the gaps 25A and 25B slightly changes, the detection voltage changes sensitively. Therefore, the presence or absence of the application of the torque to the steering shaft 4 can be detected with high sensitivity.

It is to be noted that the state of zero torque can be similarly detected by the structure of the torque switch 8 shown in FIG. 8 instead of the structure shown in FIG. That is, one gap
Two magnetic heads 27Aa and 27Bb are provided on one engagement portion 18 corresponding to only 25A, and the other engagement portion 19 is provided corresponding to these magnetic heads 27Aa and 27Bb.
Are provided with two magnetic heads 28Aa and 28Bb. 29Aa, 29Ab, 30Aa, 30Ab are holes for accommodating these magnetic heads 27Aa, 27Bb, 28Aa, 28Bb.

FIG. 9 shows still another configuration of the torque switch 8. Here, corresponding to only one gap 25A,
Magnetic heads 27A and 28A are provided on the meshing portions 18 and 19. With such a configuration, the state of zero torque can be similarly detected. That is, in this case, the timing at which the output of the circuit in FIG. 5 changes from the high level to the low level or the timing at which the output changes from the low level to the high level may be determined to be zero torque.

In the above description, since the transmission and reception of the voltage between the steering shaft 4 as the movable portion and the outer cylinder 11 as the non-movable portion are performed by the non-contact type rotary transformers 32 and 33, Compared to the case where a contact-type one such as a slip ring is used, it is possible to prevent a change with time (low durability) based on the presence of the contact portion and the entry of noise.

When the torque switch 8 detects a state of zero torque, that is, a state in which no torque is applied to the steering shaft 4, the zero point of the torque sensor 7 is corrected in real time by a known method.

[0030]

As described above, according to the present invention, the first and second meshing portions are arranged so as to face each other, and the opposing surfaces are positioned while maintaining a gap when torque is not transmitted. And at the time of torque transmission, the gap is narrowed to be located, and a magnetic head is provided to detect the presence or absence of torque to the torque transmission shaft by detecting the size of the gap. By utilizing the relationship between the magnetic head and the air gap, it is possible to detect the presence or absence of application of torque to the transmission shaft, and since the magnetic head is used, the size of the gap has only slightly changed. As a result, the detection output can be changed, and the presence or absence of torque transmission can be detected with high sensitivity.

According to the present invention, the first magnetic head is provided at the first meshing portion, and the second magnetic head facing the first magnetic head is provided at the second meshing portion; Since means for exciting the first magnetic head and means for extracting the output of the second magnetic head are provided,
With the first magnetic head and the second magnetic head facing each other,
To make one the excitation side and the other the detection side,
The presence or absence of the application of torque due to the change in the size of the gap can be detected with higher sensitivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a main part of a torque measuring device of the present invention.

FIG. 2 is a cross-sectional view of a portion shown in FIG.

FIG. 3 is a circuit diagram of a torque switch in the torque measuring device of FIG.

FIG. 4 is a diagram showing output characteristics of one magnetic head in the torque measuring device of FIG. 1;

FIG. 5 is a diagram showing a relationship between an applied torque and an output of a torque switch in the torque measuring device of FIG. 1;

FIG. 6 is a diagram showing another example of the torque switch.

FIG. 7 is a diagram showing still another example of the torque switch.

FIG. 8 is a diagram showing a main part of a steering shaft to which the torque measuring device according to the present invention is applied.

9 is a diagram showing a schematic configuration of an electric power steering device using the steering shaft of FIG. 6;

[Explanation of symbols]

 Reference Signs List 4 steering shaft 7 torque sensor 8 torque switch 18 meshing portion 19 meshing portion 20A opposing surface 20B opposing surface 21A opposing surface 21B opposing surface 25A gap 25B gap 27A magnetic head 27B magnetic head 28A magnetic head 28B magnetic head

Claims (3)

[Claims] 1. A torque measuring device provided with a torque sensor on a torque transmission shaft, wherein a first engagement portion is provided on one end side of the torque transmission shaft, and a second engagement portion is provided on the other end side, The first and second meshing portions are arranged so as to face each other, and their opposing surfaces are positioned so as to hold a gap when torque is not transmitted, and to close the gap when torque is transmitted. And a magnetic head for detecting presence or absence of torque application to the torque transmission shaft by detecting the size of the gap. 2. A first magnetic head is provided at a first engaging portion, a second magnetic head facing the first magnetic head is provided at a second engaging portion, and a first magnetic head is provided. And means for exciting the output of the second magnetic head.
The torque measuring device as described. 3. A first meshing portion having a half-moon cross section, a pair of first magnetic heads located half a circle apart from each other at the first meshing portion, and a second meshing portion. 3. The torque measuring device according to claim 2, wherein the portion is formed to have a half-moon cross section, and a pair of second magnetic heads located half a circle apart from each other are provided in the second meshing portion.