JP7740180B2 - Physical quantity detection device - Google Patents

Description

The present invention relates to a physical quantity detection device.

2. Description of the Related Art Physical quantity detection devices are known that detect physical quantities (such as steering angle and steering torque) related to steering of a steering wheel of a vehicle.
The device described in Patent Document 1 has a rotor section that rotates in conjunction with the steering wheel of a vehicle and has a first transmission gear section and a second transmission gear section with different numbers of teeth on the outer peripheral surface thereof, a first output gear that meshes with the first transmission gear section, and a second output gear that meshes with the second transmission gear section. This device detects a steering angle of 360° or more (e.g., 0 to 1440°) at the rotor section by calculating the difference between the output signal of a magnetic sensor provided on the first output gear and the output signal of a magnetic sensor provided on the second output gear.

Patent No. 4562355

However, the device described in Patent Document 1 is large in size because it has two gears, a first output gear and a second output gear, on the outside of the rotor unit. Furthermore, the device described in Patent Document 1 has the problem of low steering angle detection accuracy because the output signals from the magnetic sensors provided on the first output gear and the second output gear are both significantly affected by gear backlash.

In view of the above, the present invention aims to provide a physical quantity detection device that improves detection accuracy and has a compact size.

To achieve the above object, according to the invention of claim 1, a physical quantity detection device for detecting a physical quantity related to steering of a vehicle steering wheel includes a shaft member (1), a first sensor (10), a main gear (2), a sub-gear (3), a second sensor (20), and an electronic control unit (4). The shaft member rotates in conjunction with the steering wheel. The first sensor has a metal target (11) attached to the shaft member and an excitation detection coil (13) attached to the vehicle body, and outputs a signal corresponding to the rotation angle of the shaft member using the principle of electromagnetic induction. The main gear is attached to the shaft member. The sub-gear meshes with the main gear. The second sensor outputs a signal corresponding to the rotation angle of the sub-gear. If the difference between the steering angle calculated from the signal of the first sensor and the steering angle calculated from the signal of the second sensor is greater than a predetermined threshold, the electronic control unit corrects the steering angle calculated from the signal of the first sensor to approach the steering angle calculated from the signal of the second sensor, thereby detecting the true steering angle of the steering wheel.

According to this system, the first sensor, which uses the principle of electromagnetic induction to output a signal corresponding to the rotation angle of the shaft member, is highly accurate but may erroneously detect the electrical angle of the blades of the metal target due to error factors such as noise. On the other hand, the second sensor, which outputs a signal corresponding to the rotation angle of the sub-gear, has a large tolerance for backlash between the main gear and the sub-gear and is therefore less accurate, but does not erroneously detect the number of rotations of the sub-gear. Therefore, the steering angle calculated from the signal of the first sensor is compared with the steering angle calculated from the signal of the second sensor, and a threshold value is used to determine whether the steering angle calculated from the signal of the first sensor has erroneously detected. If the steering angle calculated from the signal of the first sensor has erroneously detected, the steering angle calculated from the signal of the first sensor is corrected based on the steering angle calculated from the signal of the second sensor. Specifically, the steering angle calculated from the signal of the first sensor is corrected to approach the steering angle calculated from the signal of the second sensor by an electrical angle corresponding to the number of erroneously detected blades. This allows the physical quantity detection device to detect the true steering angle with high accuracy. Also, this detection method increases the tolerance for backlash, making it possible to reduce the size of the gear. Therefore, the physical quantity detection device can improve detection accuracy and reduce its size.
Furthermore, since this physical quantity detection device has a large tolerance for backlash, it is possible to increase the number of selectable combinations for the number of teeth of the main gear and sub gear and the number of blades of the metal target of the first sensor.

Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described below.

3 is an explanatory diagram for explaining a method for detecting a steering angle in the physical quantity detection device according to the first embodiment. FIG. FIG. 1 is an exploded perspective view of a physical quantity detection device according to a first embodiment. 2 is a cross-sectional view taken along the axis of a shaft member in the physical quantity detection device according to the first embodiment. FIG. 10 is a graph showing a relationship between an output signal of a first sensor and an output signal of a second sensor with respect to a mechanical angle of a shaft member. 6 is a graph for explaining a method of correcting a steering angle calculated from a first sensor. 10 is an explanatory diagram for explaining a method of detecting steering torque in the physical quantity detection device according to the second embodiment. FIG. FIG. 10 is an exploded perspective view of a physical quantity detection device according to a second embodiment. FIG. 10 is a cross-sectional view taken along the axis of a shaft member in a physical quantity detection device according to a second embodiment. 4 is a graph showing the steering angle of the input shaft detected by the output signals of the first sensor and the second sensor with respect to the mechanical angle of the input shaft. 10 is a graph showing the relationship between an expected value of a third sensor calculated from a steering angle of an input shaft and an actual output signal of the third sensor with respect to a mechanical angle of an output shaft. FIG. 10 is an exploded perspective view of a physical quantity detection device of a comparative example.

Embodiments of the present invention will be described below with reference to the drawings. Note that, in the following embodiments, identical or equivalent parts will be designated by the same reference numerals, and their description will be omitted.

(First embodiment)
A first embodiment will be described with reference to the drawings. The physical quantity detection device of the first embodiment detects the steering angle of a steering wheel of a vehicle as a physical quantity related to the steering of the steering wheel. The steering angle is a rotation angle of 360 degrees or more.

First, the general configuration of the physical quantity detection device of the first embodiment will be described. As shown in Figures 2 and 3, the physical quantity detection device includes a shaft member 1, a first sensor 10, a main gear 2, a sub-gear 3, a second sensor 20, and an electronic control unit 4.

The shaft member 1 is rotatable relative to the vehicle body around its own axis CL1. The shaft member 1 is an input shaft configured to rotate in conjunction with a steering wheel (not shown) when the driver's steering force is input from the steering wheel. In the following description, the direction in which the axis CL1 of the shaft member 1 extends is referred to as the "axial direction of the shaft member 1," and the radial direction of an imaginary circle drawn on a plane perpendicular to the axis CL1 of the shaft member 1 is referred to as the "radial direction."

A cylindrical member 5, which integrally houses the main gear 2 and the metal target 11 of the first sensor 10, is fixed to the radially outer wall of the shaft member 1. The cylindrical member 5 rotates together with the shaft member 1 around the axis CL1 of the shaft member 1.

The first sensor 10 is an inductive sensor that uses the principle of electromagnetic induction to output a signal corresponding to the rotation angle of the shaft member 1. The first sensor 10 has a metal target 11, an excitation detection coil 13, and a transmitter/receiver circuit (not shown). The metal target 11 is composed of multiple blades 12 that protrude radially outward from the cylindrical member 5. The multiple blades 12 are evenly spaced at predetermined intervals around the entire circumference of the cylindrical member 5. The period of the signal output from the first sensor 10 as the shaft member 1 rotates is determined by the number of blades 12 on the metal target 11.

The excitation and detection coil 13 (specifically, the excitation coil and detection coil) and the transmitter/receiver circuit are both mounted on a circuit board 6. The circuit board 6 is fixed to the vehicle body at a position away from the metal target 11 in the direction of the axis CL1 of the shaft member 1. The transmitter/receiver circuit applies an AC current to the excitation coil and utilizes the physical principle of eddy currents generated in the metal target 11 moving above the excitation coil to output a signal corresponding to the rotation angle of the shaft member 1 due to changes in the inductance of the detection coil. The output signal of the transmitter/receiver circuit (i.e., the output signal of the first sensor 10) is transmitted to the electronic control unit 4.

The main gear 2 is provided on the outer wall of the cylindrical member 5, radially outward. The sub-gear 3 is provided at a distance radially outward from the main gear 2. The sub-gear 3 rotates around its own axis CL2 relative to the vehicle body. The main gear 2 and sub-gear 3 are in mesh. The number of teeth of the main gear 2 / the number of teeth of the sub-gear 3 is greater than 1.

The second sensor 20 can be a variety of types of sensor that outputs a signal corresponding to the rotation angle of the sub-gear 3. In this embodiment, a magnetic sensor is used as the second sensor 20. The second sensor 20 has a magnetic circuit unit 21 provided on the sub-gear 3 and a magnetic detection unit 22 mounted on the circuit board 6. The magnetic circuit unit 21 has a permanent magnet or the like and is configured so that the direction of the magnetic field passing through the magnetic detection unit 22 changes in accordance with the rotation of the sub-gear 3. The magnetic detection unit 22 is composed of, for example, a Hall IC or a magnetic resistance element. The magnetic detection unit 22 outputs a signal corresponding to the rotation angle of the sub-gear 3. The period of the signal output from the second sensor 20 in response to the rotation of the shaft member 1 is set to be longer than the period of the signal output from the first sensor 10 in response to the rotation of the shaft member 1. The output signal of the magnetic detection unit 22 (i.e., the output signal of the second sensor 20) is transmitted to the electronic control unit 4.

The electronic control unit 4 is primarily composed of a microcomputer that includes a processor for information processing and memory for storing programs, data, etc. The processor is composed of a CPU and MPU. The memory includes various non-transient tangible storage media such as ROM, RAM, and non-volatile rewritable memory.

Next, the method by which the electronic control unit 4 detects the steering angle of the steering wheel will be explained with reference to Figures 1, 4, and 5.

As shown in FIG. 1, the output signal of the first sensor 10 and the output signal of the second sensor 20 are transmitted to the electronic control unit 4. The electronic control unit 4 calculates the difference between the output signal of the first sensor 10 and the output signal of the second sensor 20. Here, FIG. 4 shows the relationship between the output signal of the first sensor 10 and the output signal of the second sensor 20 with respect to the mechanical angle (i.e., the rotation angle) of the shaft member 1. In FIG. 4, solid line A indicates the output signal of the first sensor 10, and solid line B indicates the output signal of the second sensor 20. Note that, for simplicity of explanation, FIG. 4 shows a metal target 11 of the first sensor 10 with four blades 12. Also, while FIG. 4 shows the mechanical angle of the shaft member 1 from 0 to 360 degrees, in reality, the shaft member 1 rotates more than 360 degrees.

An example of a method for calculating the rotation angle (steering angle) of the shaft member 1 from the output signal of the first sensor 10 and the output signal of the second sensor 20 is described below. First, the output signal of the first sensor 10 or the output signal of the second sensor 20 is multiplied by a coefficient to adjust the tilt. Next, the difference between the tilt-adjusted output signal of the first sensor 10 and the output signal of the second sensor 20 is calculated. Next, the "current rotation number of the sub-gear 3" or "current blade number" is calculated from the calculated difference value. However, because the "current rotation number of the sub-gear 3" or "current blade number" calculated here uses the output signal of the second sensor 20, the effect of backlash between the main gear 2 and sub-gear 3 is included.

Next, the electronic control unit 4 calculates the current rotation number of the sub-gear 3, calculated from the difference between the output signal of the first sensor 10 and the output signal of the second sensor 20, and calculates the steering angle of the shaft member 1 based on the output signal of the second sensor 20. In other words, the steering angle of the shaft member 1 is determined by adding up the output signal of the second sensor 20 and dividing it by the period. In the following explanation, the steering angle calculated in this way will be referred to as the "steering angle calculated from the output signal of the second sensor 20."

The electronic control unit 4 also calculates the current blade number, calculated from the difference between the output signal of the first sensor 10 and the output signal of the second sensor 20, and calculates the steering angle of the shaft member 1 based on the output signal of the first sensor 10. In other words, the steering angle of the shaft member 1 is calculated by adding up the output signal of the first sensor 10 and dividing it by the period. In the following explanation, the steering angle calculated in this way will be referred to as the "steering angle calculated from the output signal of the first sensor 10."

Figure 5 shows the relationship between the mechanical angle of the shaft member 1 and the steering angle calculated from the output signal of the first sensor 10 and the steering angle calculated from the output signal of the second sensor 20. In Figure 5, the steering angle calculated from the output signal of the first sensor 10 is indicated by the solid line D. Furthermore, the dashed lines E and F indicate cases where the steering angle calculated from the output signal of the first sensor 10 is erroneously detected. As described above, the period of the signal output from the first sensor 10 as the shaft member 1 rotates corresponds to the number of blades 12 on the metal target 11 and is shorter than the period of the signal output from the second sensor 20. Therefore, the steering angle calculated from the output signal of the first sensor 10 is more accurate than the steering angle calculated from the output signal of the second sensor 10. However, as described above, the difference between the output signals of the first sensor 10 and the second sensor 20 includes the effect of backlash. Furthermore, due to the influence of noise, the steering angle calculated from the output signal of the first sensor 10 may be erroneously detected by an amount equivalent to the electrical angle of the blades 12 of the metal target 11.

On the other hand, the steering angle calculated from the output signal of the second sensor 20 is shown by the hatched area G. Due to the influence of backlash, the steering angle calculated from the output signal of the second sensor 20 is less accurate than the steering calculated from the output signal of the first sensor 10. However, the period of the signal output from the second sensor 20 in conjunction with the rotation of the shaft member 1 is longer than the period of the signal output from the first sensor 10. Therefore, the steering angle calculated from the output signal of the second sensor 20 has a high tolerance for backlash, and the possibility of a major false detection occurring that is related to the number of rotations of the sub gear 3 is extremely low.

Therefore, if the difference between the steering angle calculated from the signal of the first sensor 10 and the steering angle calculated from the signal of the second sensor 20 is greater than a predetermined threshold, the electronic control unit 4 determines that the steering angle calculated from the signal of the first sensor 10 is an erroneous detection. This predetermined threshold is set in advance through experiments, etc., and stored in the memory of the electronic control unit 4. In Figure 5, for example, erroneous detection occurs in the steering angle calculated from the signal of the first sensor 10 when the mechanical angle is between θ1 and θ2, between θ3 and θ4, and between θ5 and θ6.

As shown in Figure 1, if an erroneous detection occurs in the steering angle calculated from the signal of the first sensor 10, the electronic control unit 4 determines a correction value from the steering angle calculated from the output signal of the second sensor 20. This correction value is expressed by the following equation (1).

(360 / Number of target blades) x Number of falsely detected target blades [deg] ... (Equation 1)

The electronic control unit 4 uses the correction value shown in equation (1) above to correct the steering angle calculated from the signal of the first sensor 10 so that it approaches the steering angle calculated from the signal of the second sensor 20. That is, the electronic control unit 4 makes corrections as shown by arrows H, I, and J in Figure 5. This enables the electronic control unit 4 to detect the true steering angle of the steering wheel (in other words, the true steering angle of the shaft member 1).

The physical quantity detection device according to the first embodiment described above has the following advantages.
(1) In the first embodiment, if the difference between the steering angle calculated from the signal of the first sensor 10 and the steering angle calculated from the signal of the second sensor 20 is greater than a predetermined threshold, the electronic control unit 4 determines that the steering angle calculated from the signal of the first sensor 10 is an erroneous detection. In this case, the electronic control unit 4 corrects the steering angle calculated from the signal of the first sensor 10 so that it approaches the steering angle calculated from the signal of the second sensor 20. In this way, the electronic control unit 4 detects the true steering angle of the steering wheel.

According to this, the first sensor 10, which uses an inductive sensor, is highly accurate but may produce erroneous detection of the electrical angle of the blades 12 of the metal target 11 due to error factors such as noise. On the other hand, the second sensor 20, which outputs a signal corresponding to the rotation angle of the sub-gear 3, has a high tolerance for backlash and is less accurate, but is extremely unlikely to produce a significant erroneous detection that is related to the number of rotations of the sub-gear 3. Therefore, the electronic control unit 4 compares the steering angle calculated from the signal of the first sensor 10 with the steering angle calculated from the signal of the second sensor 20, and determines whether or not the steering angle calculated from the signal of the first sensor 10 has been erroneously detected based on a threshold. If the steering angle calculated from the signal of the first sensor 10 has been erroneously detected, the electronic control unit 4 corrects the steering angle calculated from the signal of the first sensor 10 based on the steering angle calculated from the signal of the second sensor 20. Specifically, the steering angle calculated from the signal of the first sensor 10 is corrected by an electrical angle corresponding to the number of erroneously detected blades 12 so as to approach the steering angle calculated from the signal of the second sensor 20. This allows the physical quantity detection device to detect the true steering angle with high accuracy. Furthermore, this detection method increases the tolerance for backlash, making it possible to reduce the size of the main gear 2 and the sub gear 3. Therefore, the physical quantity detection device can improve detection accuracy and reduce its size.
Furthermore, because this physical quantity detection device has a large tolerance for backlash, it is possible to increase the number of selectable combinations for the number of teeth on the main gear 2 and sub gear 3 and the number of blades 12 on the metal target 11 of the first sensor 10. The effect of being able to increase the number of combinations is that it is possible to widen the detection range of the steering angle, because the detection range of the steering angle is determined by the ratio between the number of blades 12 on the first sensor 10 and the number of teeth on the main gear 2 and sub gear 3 on the second sensor 20. This makes it possible to create a small, highly accurate sensor with a wide detection range.

(2) In the first embodiment, the period of the signal output by the first sensor 10 in response to the rotation of the shaft member 1 is shorter than the period of the signal output by the second sensor 20 in response to the rotation of the shaft member 1 .
This shortens the period of the signal output by the first sensor 10, thereby improving the detection accuracy of the steering angle calculated from the signal of the first sensor 10. Specifically, by increasing the number of blades 12 of the metal target 11 of the first sensor 10, the period of the signal output by the first sensor 10 can be shortened, thereby improving the detection accuracy of the steering angle.

Second Embodiment
A second embodiment will be described. In the first embodiment described above, the physical quantity detection device detects a steering angle as a physical quantity related to steering of a steering wheel of a vehicle. In contrast, in the second embodiment, a physical quantity detection device detects a steering torque as a physical quantity related to steering will be described.

First, the general configuration of the physical quantity detection device of the second embodiment will be described. As shown in Figures 7 and 8, the physical quantity detection device of the second embodiment includes an output shaft 7, a torsion bar 8, and a third sensor 30 in addition to the components described in the first embodiment.

In the second embodiment, the shaft member 1 described in the first embodiment is referred to as the "input shaft 1." The driver's steering force is input to the input shaft 1 from the steering wheel.

The output shaft 7 is arranged coaxially with the input shaft 1. The output shaft 7 is arranged to be rotatable relative to the vehicle body around its own axis CL3. The output shaft 7 is connected to the wheels, for example, via a rack shaft (not shown). A lower cylinder member 9, on which a metal target 31 of a third sensor 30 is mounted, is fixed to the outer wall of the radially outer side of the output shaft 7. The lower cylinder member 9 rotates together with the output shaft 7 around the axis CL3 of the output shaft 7.

One end 8a of the torsion bar 8 is inserted into a hole 1a provided in the input shaft 1, and the other end 8b is inserted into a hole 7a provided in the output shaft 7. One end 8a of the torsion bar 8 is fixed deep within the hole 1a of the input shaft 1, and the other end 8b is fixed deep within the hole 7a of the output shaft 7. The torsion bar 8 elastically deforms around its own axis in response to the torsional torque acting on the input shaft 1 and the output shaft 7 (i.e., it twists around its own axis).

The third sensor 30 is an inductive sensor that uses the principle of electromagnetic induction to output a signal corresponding to the rotation angle of the output shaft 7. The third sensor 30 has a metal target 31, an excitation detection coil 33, and a transmitter/receiver circuit (not shown). The metal target 31 is composed of multiple blades 32 that protrude radially outward from the lower cylinder member 9. The multiple blades 32 are evenly spaced at predetermined intervals around the entire circumference of the lower cylinder member 9. The period of the signal output from the third sensor 30 as the output shaft 7 rotates is determined by the number of blades 32 on the metal target 31.

The excitation and detection coil 33 (specifically, the excitation coil and detection coil) and the transmission and reception circuit of the third sensor 30 are both mounted on the substrate 6. The output signal of the transmission and reception circuit (i.e., the output signal of the third sensor 30) is transmitted to the electronic control unit 4.

The number of blades 12, 32 on the metal targets 11, 31 of the first sensor 10 and the third sensor 30 (hereinafter referred to as the "first and third sensors 10, 30"), respectively, can be set arbitrarily. For example, the number of blades 12, 32 on the metal targets 11, 31 of the first and third sensors 10, 30, respectively, may be an integer multiple including 1, or may not be an integer multiple. As an example, in the second embodiment, the number of blades 12, 32 on the metal targets 11, 31 of the first and third sensors 10, 30, respectively, is set as follows: That is, the number of blades on the metal target of one of the first and third sensors 10, 30 is set to a number excluding an integer multiple of the number of blades on the metal target of the other sensor. In particular, the number of blades of the first or third sensor 10, 30 which has fewer blades for the metal target is set to more than half the number of blades of the first or third sensor 10, 30 which has more blades for the metal target.

Next, the method by which the electronic control unit 4 detects steering torque based on the output signals of the first to third sensors 10, 20, and 30 will be explained with reference to Figures 6, 9, and 10.

As shown in Figure 6, output signals from the first to third sensors 10, 20, and 30 are transmitted to the electronic control unit 4. The method for detecting the true steering angle of the steering wheel from the output signals of the first sensor 10 and the second sensor 20 is the same as in the first embodiment, so a description thereof will be omitted. Note that the steering angle of the steering wheel is the same as the steering angle of the input shaft 1. In other words, as shown in Figure 9, the electronic control unit 4 detects the true steering angle of the input shaft 1.

Next, as shown in FIG. 6, the electronic control unit 4 converts the detected true steering angle of the input shaft 1 into the electrical angle of the third sensor 30. In particular, the electronic control unit 4 calculates the output signal of the third sensor 30 from the detected true steering angle of the input shaft 1 when it is assumed that the steering angle of the input shaft 1 and the steering angle of the output shaft 7 are the same (in other words, when it is assumed that the steering torque is 0). The output signal of the third sensor 30 (i.e., the electrical angle) calculated under such an assumption is called the expected value of the third sensor 30.

Next, the electronic control unit 4 calculates the difference angle between the expected value of the third sensor 30 and the actual output signal of the third sensor 30. Figure 10 shows the relationship between the expected value of the third sensor 30 and the actual output signal of the third sensor 30 relative to the mechanical angle of the output shaft 7. The dashed line K in Figure 10 indicates the expected value of the third sensor 30, and the solid line L indicates the actual output signal of the third sensor 30. When the driver turns the steering wheel, a predetermined steering torque (torsion torque) acts on the input shaft 1 and the output shaft 7, twisting the torsion bar 8 around its own axis with a predetermined elastic coefficient. As a result, the mechanical angle of the input shaft 1 and the mechanical angle of the output shaft 7 differ from each other. Therefore, the expected value of the third sensor 30 and the actual output signal of the third sensor 30 differ from each other. In this case, the difference angle M between the expected value of the third sensor 30 and the actual output signal of the third sensor 30 is a value that correlates with the steering torque. In other words, the larger the angle difference M, the greater the steering torque. Therefore, as shown in Figure 6, the electronic control unit 4 can calculate the steering torque from the angle difference M.

Here, a comparative physical quantity detection device will be described for comparison with the physical quantity detection device of the second embodiment described above.

As shown in FIG. 11 , the physical quantity detection device of the comparative example does not include the main gear 2, sub-gear 3, and second sensor 20 described in the first and second embodiments, but only includes the first sensor 10 and the third sensor 30. Therefore, the electronic control unit 4 included in the physical quantity detection device of the comparative example directly compares the output signal of the first sensor 10 with the output signal of the third sensor 30 when detecting steering torque. Specifically, the steering torque is detected by calculating the difference between the output signals of the first sensor 10 and the third sensor 30. Therefore, in the comparative example, it is convenient for calculating steering torque to set the number of blades on the metal target of one of the first and third sensors 10, 30 to an integer multiple greater than one of the number of blades on the metal target of the other sensor. This makes it easy to calculate steering torque in the comparative example.

Compared with the physical quantity detection device of the comparative example described above, the physical quantity detection device of the second embodiment has the following advantages.
(1) In the second embodiment, the electronic control unit 4 compares the steering angle of the input shaft 1 detected from the output signals of the first sensor 10 and the second sensor 20 with the output signal of the third sensor 30 to calculate the steering torque.
According to this, the electronic control unit 4 of the second embodiment does not directly compare the output signal of the first sensor 10 with the output signal of the third sensor 30, as in the comparative example. Therefore, there is no need to impose constraints such as an integer multiple on the period of the output signal of the first sensor 10 accompanying the rotation of the input shaft 1 and the period of the signal output by the third sensor 30 accompanying the rotation of the output shaft 7. This increases the degree of freedom in design.

(2) In the second embodiment, the electronic control unit 4 calculates the output signal of the third sensor 30 as an expected value of the third sensor 30 when it is assumed that the steering angle of the input shaft 1 detected from the output signals of the first sensor 10 and the second sensor 20 is the same as the steering angle of the output shaft 7. Then, the electronic control unit 4 calculates the steering torque from the difference angle between the actual output signal of the third sensor 30 and the expected value of the third sensor 30.
According to this, the electronic control unit 4 can compare the steering angle of the input shaft 1 detected from the output signals of the first sensor 10 and the second sensor 20 with the output signal of the third sensor 30 to calculate the steering torque.

(3) In the second embodiment, the number of blades of the metal target of one of the first and third sensors 10, 30 is a number excluding an integer multiple of the number of blades of the metal target of the other sensor.
This eliminates the need to impose restrictions such as an integer multiple on the number of blades of the metal targets of the first and third sensors 10, 30, respectively, thereby increasing the degree of freedom in design.

(4) In the second embodiment, the number of blades of the first or third sensor 10, 30 having the fewer blades on the metal target is more than half the number of blades of the first or third sensor 10, 30 having the greater number of blades on the metal target.
According to this, the detection accuracy of the rotation angle by the inductive sensor increases as the number of blades on the metal target increases. Therefore, the detection of steering torque by the physical quantity detection device is rate-limited by the number of blades of the sensor having fewer blades on the metal target, out of the first and third sensors 10, 30. Therefore, in the second embodiment, the number of blades of the sensor having fewer blades on the metal target, out of the first and third sensors 10, 30, is set to be more than half the number of blades of the sensor having the larger number of blades on the metal target, out of the first and third sensors 10, 30. As a result, the physical quantity detection device of the second embodiment can detect steering torque with higher accuracy than the physical quantity detection device of the comparative example.

(Other embodiments)
(1) In the first embodiment, the physical quantity detection device detects the steering angle of an input shaft as a shaft member. However, the physical quantity detection device is not limited to this. For example, the physical quantity detection device may detect the steering angle of an output shaft as a shaft member.

(2) In the second embodiment, the third sensor that detects the steering angle of the output shaft is configured as an inductive sensor, but this is not limiting. For example, a sub-gear type sensor like the second sensor may also be used.

(3) In the second embodiment, the steering angle of the input shaft is detected using the method described in the first embodiment, but this is not limiting and other methods may be used for detection. For example, the steering angle of the input shaft may be calculated from the difference between the output signals of the first sensor and the second sensor and the output signal of the second sensor. Alternatively, the steering angle of the input shaft may be calculated from the difference between the output signals of the first sensor and the second sensor and the output signal of the first sensor.

The present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the claims. Furthermore, the above-described embodiments and portions thereof are not unrelated to each other and can be combined as appropriate, except where such combinations are clearly impossible. It goes without saying that, in the above-described embodiments, the elements constituting the embodiments are not necessarily essential, except where expressly stated as essential or where they are clearly considered essential in principle. Furthermore, in the above-described embodiments, when numerical values such as the number, value, amount, or range of components of the embodiments are mentioned, they are not limited to that specific number, except where expressly stated as essential or where they are clearly limited to a specific number in principle. Furthermore, in the above-described embodiments, when the shape, positional relationship, etc. of components, etc. are mentioned, they are not limited to that shape, positional relationship, etc., except where expressly stated as essential or where they are clearly limited to a specific shape, positional relationship, etc. in principle.

The control unit and method described in the present invention may be implemented by a special-purpose computer provided by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and method described in the present invention may be implemented by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and method described in the present invention may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible recording medium.

The features of the present disclosure are as follows.
[Claim 1]
A physical quantity detection device for detecting a physical quantity related to steering of a steering wheel of a vehicle,
A shaft member (1) that rotates in conjunction with the steering wheel;
a first sensor (10) having a metal target (11) provided on the shaft member and an excitation detection coil (13) provided on the vehicle body side, and outputting a signal according to the rotation angle of the shaft member using the principle of electromagnetic induction;
a main gear (2) provided on the shaft member;
a sub-gear (3) meshing with the main gear;
a second sensor (20) that outputs a signal corresponding to the rotation angle of the sub gear;
and an electronic control unit (4) that, when a difference between the steering angle calculated from the signal of the first sensor and the steering angle calculated from the signal of the second sensor is greater than a predetermined threshold, corrects the steering angle calculated from the signal of the first sensor to approach the steering angle calculated from the signal of the second sensor, thereby detecting a true steering angle of the steering wheel.
[Claim 2]
The physical quantity detection device according to claim 1 , wherein a period of the signal output by the first sensor in response to rotation of the shaft member is shorter than a period of the signal output by the second sensor in response to rotation of the shaft member.
[Claim 3]
the shaft member is an input shaft to which a steering force of a driver is input from the steering wheel,
an output shaft (7) provided coaxially with the input shaft;
a torsion bar (8) having one end (8a) fixed to the input shaft and the other end (8b) fixed to the output shaft, and elastically deforming in response to a torsional torque acting on the input shaft and the output shaft;
a third sensor (30) that outputs a signal according to the rotation angle of the output shaft,
3. The physical quantity detection device according to claim 1, wherein the electronic control unit compares a true steering angle of the input shaft detected from the output signal of the first sensor and the output signal of the second sensor with the output signal of the third sensor to calculate a steering torque.
[Claim 4]
4. The physical quantity detection device according to claim 3, wherein the electronic control unit calculates, from a true steering angle of the input shaft detected from the output signal of the first sensor and the output signal of the second sensor, an expected value of the third sensor when it is assumed that the steering angle of the input shaft detected from the signal of the first sensor and the signal of the second sensor is identical to the steering angle of the output shaft, and calculates the steering torque from a differential angle between the actual output signal of the third sensor and the expected value of the third sensor.
[Claim 5]
5. The physical quantity detection device according to claim 3, wherein the third sensor is an inductive sensor that has a metal target (31) provided on the output shaft and an excitation detection coil (33) provided on the vehicle body side, and outputs a signal according to a rotation angle of the output shaft using the principle of electromagnetic induction.
[Claim 6]
6. The physical quantity detection device according to claim 5, wherein the number of blades of the metal target of one of the first sensor and the third sensor is a number excluding an integer multiple of the number of blades of the metal target of the other sensor.
[Claim 7]
7. The physical quantity detection device according to claim 5, wherein the number of blades of one of the first sensor and the third sensor, which has a smaller number of blades for detecting the metal target, is more than half the number of blades of the other of the first sensor and the third sensor, which has a larger number of blades for detecting the metal target.

1 Shaft member (input shaft)
2 Main gear 3 Sub gear 4 Electronic control unit 10 First sensor 11 Metal target (first sensor)
13 Excitation detection coil (first sensor)
20 Second sensor

Claims (7)

A physical quantity detection device for detecting a physical quantity related to steering of a steering wheel of a vehicle,
a shaft member (1) that rotates in conjunction with the steering wheel;
a first sensor (10) having a metal target (11) provided on the shaft member and an excitation detection coil (13) provided on the vehicle body side, and outputting a signal according to the rotation angle of the shaft member using the principle of electromagnetic induction;
a main gear (2) provided on the shaft member;
a sub-gear (3) meshing with the main gear;
a second sensor (20) that outputs a signal corresponding to the rotation angle of the sub gear;
and an electronic control unit (4) that, when a difference between the steering angle calculated from the signal of the first sensor and the steering angle calculated from the signal of the second sensor is greater than a predetermined threshold, corrects the steering angle calculated from the signal of the first sensor to approach the steering angle calculated from the signal of the second sensor, thereby detecting a true steering angle of the steering wheel. The physical quantity detection device of claim 1, wherein the period of the signal output by the first sensor in response to rotation of the shaft member is shorter than the period of the signal output by the second sensor in response to rotation of the shaft member. the shaft member is an input shaft to which a steering force of a driver is input from the steering wheel,
an output shaft (7) provided coaxially with the input shaft;
a torsion bar (8) having one end (8a) fixed to the input shaft and the other end (8b) fixed to the output shaft, and elastically deforming in response to a torsional torque acting on the input shaft and the output shaft;
a third sensor (30) that outputs a signal according to the rotation angle of the output shaft,
3. The physical quantity detection device according to claim 1, wherein the electronic control unit compares a true steering angle of the input shaft detected from the output signal of the first sensor and the output signal of the second sensor with the output signal of the third sensor to calculate a steering torque. The physical quantity detection device described in claim 3, wherein the electronic control unit calculates the output signal of the third sensor as an expected value of the third sensor based on the true steering angle of the input shaft detected from the output signal of the first sensor and the output signal of the second sensor, assuming that the steering angle of the input shaft detected from the signal of the first sensor and the signal of the second sensor is the same as the steering angle of the output shaft, and calculates the steering torque from the differential angle between the actual output signal of the third sensor and the expected value of the third sensor. The physical quantity detection device described in claim 3, wherein the third sensor is an inductive sensor having a metal target (31) attached to the output shaft and an excitation detection coil (33) attached to the vehicle body, and outputs a signal corresponding to the rotation angle of the output shaft using the principle of electromagnetic induction. The physical quantity detection device according to claim 5, wherein the number of blades on the metal target of one of the first and third sensors is a number excluding an integer multiple of the number of blades on the metal target of the other sensor. The physical quantity detection device of claim 6, wherein the number of blades of the sensor having the fewer blades on the metal target out of the first sensor and the third sensor is more than half the number of blades of the sensor having the greater number of blades on the metal target out of the first sensor and the third sensor.