Steering operation force detecting apparatus

A steering operation force detecting apparatus enabling to know in detail a force or a moment applied to a steering wheel rim (steering wheel) gripped by a driver during steering is provided. A force and a moment applied to each divided portion 11A and 11B of a steering wheel rim 11 are detected by force sensors 21A and 21B. Force applied points FP1 and FP2 of driver's hands which grip the divided portions 11A and 11B of the steering wheel rim 11 are detected by contact sensors 22 and an arithmetic processing section. Also, forces and moments at the force applied points FP1 and FP2 are calculated based on the detection results, and the calculation results are output to a higher-level device. Accordingly, it is possible to know in detail how much force or moment is applied to the force applied points FP1 and FP2 on the steering wheel rim 11 during a steering operation.

This application is the U.S. National Phase under 35 U.S.C. §371 of International Application PCT/JP2008/057316, filed Apr. 15, 2008, which claims priority to Japanese Patent Application No. 2007-111416, filed Apr. 20, 2007. The International Application was published under PCT Article 21(2) in a language other than English.

TECHNICAL FIELD

The present invention relates to a steering operation force detecting apparatus for detecting an operation force applied to a steering wheel at the time of steering a vehicle or the like.

BACKGROUND ART

It becomes increasingly important to know the sense of driving during steering by a driver in the performance evaluation or the like of new-model cars and tires. In this case, it is considered to be effective in the performance evaluation or the like to know in detail a force or a moment applied to a steering wheel rim (steering wheel) gripped by a driver during steering.

As a conventionally known detecting apparatus for detecting a force applied to the steering wheel rim (steering wheel) of a vehicle, there are known an apparatus for detecting the position of hands on a steering wheel, which is disclosed in National Publication of International Patent Application No. 2003-535757 (Patent Document 1), a steering wheel with an opto-electronic sensor, which is disclosed in National Publication of International Patent Application No. 2000-500101 (Patent Document 2), and an apparatus for evaluating steering operability by the analysis of a hand force, which is disclosed in Society of Automotive Engineers of Japan, Inc., Preprints of Meeting on Automotive Engineers, No. 55-03, P13-16 (Non-Patent Document 1).

In the apparatus disclosed in the Patent Document 1, sensors are provided in a steering wheel for a vehicle having a steering ring, a hub, and at least one spoke connecting the steering ring and the hub to detect a force applied to a steering wheel rim (steering wheel). The sensors used in the apparatus are divided into plural segments arranged successively in the longitudinal direction of the steering ring. Also, the sensors extend over the entire length of the steering ring and are arranged distributed over the periphery of the steering ring. By arranging the sensors as described above, the position of hands on the steering wheel can be detected by the sensors.

In the apparatus disclosed in the Patent Document 2, an optical sensor including an optical fiber which is wound around a steering wheel for controlling a vehicle is provided. By detecting a change in light signal passing through the optical fiber, the state in which a driver grips the steering wheel is detected.

An apparatus enabling to measure torque during steering by providing a torque sensor in a steering wheel hub is also known.Patent Document 1: National Publication of International Patent Application No. 2003-535757

Patent Document 2: National Publication of International Patent Application No. 2000-500101

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

As described above, it becomes increasingly important to know the sense of driving during steering by a driver in the performance evaluation or the like of new-model cars and tires. In this case, it is considered to be effective in the performance evaluation or the like to know in detail a force or a moment applied to a steering wheel rim (steering wheel) gripped by a driver during steering.

However, there is not known an apparatus for detecting how much force or moment is applied to a steering wheel by the steering operation of a driver, or how much force or moment is applied to a position on the steering wheel which the driver grips when the driver actually performs steering.

The present invention has been made in view of the aforementioned problems, and it is an object of the present invention to provide a steering operation force detecting apparatus enabling to know in detail a force or a moment applied to a steering wheel rim (steering wheel) gripped by a driver during steering.

Means for Solving the Problems

In order to achieve the above object, the present invention proposes a steering operation force detecting apparatus including: a steering wheel rim constituting a steering wheel and divided into at least two portions in a steering direction; a plurality of steering arms coupling each of the divided portions of the steering wheel rim and a steering wheel hub; first detecting means provided in each of the steering arms for detecting a force and a moment applied to each of the divided portions of the steering wheel rim; second detecting means for detecting a force applied point of a driver's hand which grips the divided portions of the steering wheel rim; arithmetic calculation means for calculating a force and a moment at the force applied point based on each detection result of the first detecting means and the second detecting means; and calculation result output means for outputting a calculation result by the arithmetic calculation means.

With the steering operation force detecting apparatus of the present invention, the force and the moment applied to each of the divided portions of the steering wheel rim are detected by the first detecting means. Also, the force applied point of the driver's hand which grips the divided portions of the steering wheel rim is detected by the second detecting means. Moreover, the force and the moment at the force applied point are calculated based on the detection results, and the calculation result is output. Accordingly, it is possible to know in detail how much force or moment is applied to the force applied point on the steering wheel rim during a steering operation.

Also, the present invention proposes the steering operation force detecting apparatus, characterized in that the second detecting means includes a sensor for detecting the force applied point arranged in each of the divided portions of the steering wheel rim.

With the steering operation force detecting apparatus of the present invention, the force applied point is detected by the sensor arranged in each of the divided portions of the steering wheel rim.

Also, the present invention proposes the steering operation force detecting apparatus, characterized in that the sensor for detecting the force applied point includes a plurality of contact sensors for detecting the presence or absence of contact of the driver's hand with the steering wheel rim, and the second detecting means includes means for obtaining the force applied point by the presence or absence of contact obtained by the contact sensors.

With the steering operation force detecting apparatus of the present invention, the presence or absence of contact of the driver's hand with the steering wheel rim is detected by the contact sensors arranged in each of the divided portions of the steering wheel rim. Moreover, the force applied point is obtained by the presence or absence of contact obtained by the contact sensors.

Also, the present invention proposes the steering operation force detecting apparatus, characterized in that the second detecting means includes means for obtaining the force applied point based on a distribution of the presence or absence of contact obtained by the plurality of contact sensors.

With the steering operation force detecting apparatus of the present invention, the presence or absence of contact of the driver's hand with the steering wheel rim is detected by the contact sensors arranged in each of the divided portions of the steering wheel rim. Moreover, the force applied point is obtained based on the distribution of the presence or absence of contact obtained by the contact sensors.

Also, the present invention proposes the steering operation force detecting apparatus, characterized in that the sensor for detecting the force applied point includes means for detecting a contact pressure of the driver's hand at a plurality of positions on the steering wheel rim, and the second detecting means includes means for outputting a detection result of the contact pressure at each of the plurality of positions.

With the steering operation force detecting apparatus of the present invention, the contact pressure of the driver's hand on the steering wheel rim is detected by the contact sensors arranged in each of the divided portions of the steering wheel rim. Moreover, the detection result of the contact pressure obtained by each contact sensor is output.

Also, the present invention proposes the steering operation force detecting apparatus, characterized in that the second detecting means includes means for obtaining the force applied point based on a distribution of the detected contact pressure.

With the steering operation force detecting apparatus of the present invention, the contact pressure of the driver's hand on the steering wheel rim is detected by the contact sensors arranged in each of the divided portions of the steering wheel rim. Moreover, the force applied point is obtained based on the distribution of the contact pressure detected by the contact sensors.

Also, the present invention proposes the steering operation force detecting apparatus, further including: means for detecting a steer angle of the steering wheel; means for transforming a coordinate system representing the force and the moment at the force applied point into a predetermined coordinate system based on the detected steer angle; and means for outputting the force and the moment at the force applied point represented by the transformed coordinate system as a detection result.

With the steering operation force detecting apparatus of the present invention, the steer angle of the steering wheel is detected. The coordinate system representing the force and the moment at the force applied point is transformed into a predetermined coordinate system based on the detected steer angle. Moreover, the force and the moment at the force applied point represented by the transformed coordinate system are output as the detection result.

Advantages of the Invention

With the steering operation force detecting apparatus of the present invention, the force and the moment applied to each of the divided portions of the steering wheel rim are detected by the first detecting means. Also, the force applied point of the driver's hand which grips the divided portions of the steering wheel rim is detected by the second detecting means. The force and the moment at the force applied point are calculated based on the detection results, and the calculation result is output. Therefore, it is possible to know in detail how much force or moment is applied to the force applied point on the steering wheel rim during a steering operation from the result. Accordingly, in the performance evaluation or the like of new-model cars and tires by using the apparatus of the present invention, it is possible to know in detail and in real-time the sense of driving during steering by a driver as the data of the force or the moment applied to the steering wheel rim (steering wheel) gripped by the driver during steering. The present invention can be thereby effectively utilized in the performance evaluation or the like.

DESCRIPTION OF SYMBOLS

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 4illustrate a first embodiment of the present invention.FIG. 1is a configuration diagram illustrating the main portion of a steering operation force detecting apparatus according to the first embodiment of the present invention.FIG. 2is a block diagram illustrating an electrical system circuit of the steering operation force detecting apparatus according to the first embodiment of the present invention.FIG. 3is a flowchart explaining a processing operation according to the first embodiment of the present invention.FIG. 4is a view explaining a detection operation according to the first embodiment of the present invention.

In the drawings, reference numeral10denotes a steering operation force detecting apparatus, which is constituted by a steering wheel rim11(11A,11B), a steering arm12(12A,12B) coupling the steering wheel rim11and a steering wheel hub13, and a processing unit20.

The steering wheel rim11is equally divided into two portions of the first divided portion11A and the second divided portion11B in the steering direction (rotation direction) along a vertical line. The first divided portion11A is coupled to the steering wheel hub13by the steering arm12A. The second divided portion11B is coupled to the steering wheel hub13by the steering arm12B.

Also, force sensors21A and21B for detecting a force and a moment applied to the steering arms12A and12B are provided substantially in each central portion of the steering arms12A and12B in the longitudinal direction. A known six-component load cell capable of detecting three component forces in x-axis, y-axis, and z-axis directions orthogonal to each other, and moments around the three axes at the same time is used as the force sensors21A and21B, for example. Here, the force sensors21A and21B are mounted corresponding to an x, y, z orthogonal coordinate system in which the longitudinal direction of the steering arms12A and12B is an x axis and the direction orthogonal to the x axis in the rotational plane of the steering wheel rim11is a y axis with the coordinate of a central point131(intersection of the plane with the rotation axis) of the steering wheel hub13in the rotational plane being the origin.

On the other hand, a plurality of contact sensors22are arranged at regular intervals in the circumferential direction in each of the first and second divided portions11A and11B of the steering wheel rim11. The contact sensors22are for detecting a position on the steering wheel rim11which a driver grips with his/her hands. As the contact sensor22, a pressure-sensitive sensor, an electrode-type touch sensor, or an optical sensor can be used, for example.

The processing unit20includes a sensor interface23, an arithmetic processing section24, a storage section25, and a data output section26.

The sensor interface23supplies driving power to the force sensors21A,21B and the plurality of contact sensors22. Also, electric signals as detection results output from the force sensors21A,21B and the plurality of contact sensors22are input to the sensor interface23. The sensor interface23outputs the detection result of each sensor to the arithmetic processing section24as digital data.

The arithmetic processing section24is mainly constituted by a known CPU and a memory, and operates based on a program stored in advance in the memory. Also, the detection result of each sensor is input from the sensor interface23to the arithmetic processing section24at predetermined time intervals (for example, at one-second intervals). The arithmetic processing section24obtains a force applied point described below based on the detection result. Furthermore, the arithmetic processing section24calculates a force and a moment at the force applied point, and stores the result in the storage section25with the coordinate data of each sensor and the detection time data described below. Moreover, the arithmetic processing section24outputs the data to an unillustrated higher-level device via the data output section26.

Also, the arithmetic processing section24deletes the data of the detection results stored in the storage section25, or outputs the data to the unillustrated higher-level device via the data output section26based on the operation of an unillustrated switch or the like.

The data of coordinates O1and O2of the detecting central points of the force sensors21A and21B and the data of the location coordinate of each contact sensor22in the x, y, z orthogonal coordinate system with the coordinate of the central point131(intersection of the plane with the rotation axis) of the steering wheel hub13in the rotational plane of the steering wheel rim11being the origin when the steering wheel rim11is in the position obtained when a vehicle is traveling straight are stored in advance in the storage section25. The arithmetic processing section24calculates a distance between the respective coordinates based on the data stored in the storage section25.

The contact sensors22in each of the first and second divided portions11A and11B of the steering wheel rim11are numbered in order from the one arranged in one end of the divided portions11A and11B. The coordinate of each contact sensor22is stored corresponding to the number in the storage section25.

Next, the processing operation of the arithmetic processing section24will be described in detail with reference toFIGS. 3 and 4.

The force sensors21A and21B detect forces and moments represented by the x, y, z orthogonal coordinate with the detecting central points O1and O2being the center, and output the detection result. Also, each of the contact sensors22outputs an electric signal indicating the presence or absence of contact of a driver's hand. Only the contact sensors22existing in gripped regions ER1and ER2by driver's hands output the electric signals indicating the presence of contact.

The arithmetic processing section24obtains the data of the presence or absence of contact detected by each contact sensor and the data of the force and the moment detected by each force sensor via the sensor interface23(SA1, SA2). The arithmetic processing section24stores the respective data in the storage section25with the detection time data by correlating the respective data with the coordinate data of each sensor (SA3). Moreover, the arithmetic processing section24calculates the coordinates of force applied points FP1and FP2based on the detection result of each sensor and the coordinate data of each sensor (SA4), and also, calculates forces and moments applied to the force applied points FP1and FP2(SA5). After that, the arithmetic processing section24stores the calculation results of the forces and the moments at the force applied points in the storage section25with the coordinate data of each sensor and the detection time data described below (SA6). Also, the arithmetic processing section24outputs the data to the unillustrated higher-level device via the data output section26(SA7).

Next, the arithmetic processing section24resets the counted time of a timer (SA8), and starts to count time. When a counted time T of the timer reaches a predetermined time T1or more (SA9), the process moves to the process of SA1described above and the above processes are repeated. Although the time T1is set to one second in the present embodiment, the value of the time T1is not limited to this value and may be set to any value.

When the coordinates of the force applied points FP1and FP2are to be obtained, the arithmetic processing section24obtains the central coordinate of the coordinates of all the contact sensors22existing in each region of the gripped regions ER1and ER2by driver's hands as the coordinates of the force applied points FP1and FP2.

Also, a force FFP1and a moment MFP1at the force applied point FP1described above can be calculated by using the following Equation (1) and Equation (2). A force FFP2and a moment MFP2at the force applied point FP2can be similarly calculated.
FFP1=F  (1)
MFP1=M−a×F(2)

F represents a force detected by the force sensor21A, M represents a moment detected by the force sensor21A, and a represents a position vector from the detecting central point of the force sensor21A to the force applied point F21. The calculation of the force and the moment at the force applied point FP2is similarly performed as described above.

With the steering operation force detecting apparatus10having the above configuration, the force and the moment applied to each of the divided portions11A and11B of the steering wheel rim11are detected by the force sensors21A and21B. Also, the force applied points F21and F22of driver's hands which grip the divided portions11A and11B of the steering wheel rim11are detected using the contact sensors22. Moreover, the forces and the moments at the force applied points FP1and FP2are calculated based on the detection results, and the calculation results are output. Therefore, it is possible to know in detail how much force or moment is applied to the force applied points FP1and FP2on the steering wheel rim11during a steering operation. Accordingly, in the performance evaluation or the like of new-model cars and tires by using the apparatus of the present invention, it is possible to know in detail and in real-time the sense of driving during steering by a driver as the data of the forces or the moments applied to the steering wheel rim (steering wheel)11gripped by the driver during steering. The present invention can be thereby effectively utilized in the performance evaluation or the like of new-model cars and tires.

FIGS. 5 to 9illustrate the second embodiment of the present invention.FIG. 5is a block diagram illustrating an electrical system circuit of a steering operation force detecting apparatus according to the second embodiment of the present invention.FIG. 6is a configuration diagram illustrating the main portion of the steering operation force detecting apparatus according to the second embodiment of the present invention.FIGS. 7 and 8are views explaining a detection operation according to the second embodiment of the present invention.FIG. 9is a flowchart explaining a processing operation according to the second embodiment of the present invention.

In the drawings, the same components as those in the first embodiment described above are assigned the same reference numerals to omit the description.

In a steering operation force detecting apparatus10B of the second embodiment, a contact-pressure sensor31is provided instead of the contact sensor22of the first embodiment, and a processing unit20B corresponding thereto is provided.

The contact-pressure sensor31detects a contact pressure applied to the contact-pressure sensor31when a driver grips the steering wheel rim11, and outputs an electric signal of the detection result to a sensor interface32.

The processing unit20B includes the sensor interface32, an arithmetic processing section33, a storage section34, and the data output section26.

The sensor interface32supplies driving power to the force sensors21A,21B and a plurality of contact-pressure sensors31. Also, electric signals as detection results output from the force sensors21A,21B and the plurality of contact-pressure sensors31are input to the sensor interface32. The sensor interface32outputs the detection result of each sensor to the arithmetic processing section33as digital data.

The arithmetic processing section33is mainly constituted by a known CPU and a memory, and operates based on a program stored in advance in the memory. Also, the detection result of each sensor is input from the sensor interface32to the arithmetic processing section33at predetermined time intervals (for example, at one-second intervals). The arithmetic processing section33obtains a force applied point based on the contact pressure as described below. Furthermore, the arithmetic processing section33calculates a force and a moment at the force applied point, and stores the result in the storage section34with the coordinate data of each sensor and the detection time data described below. Moreover, the arithmetic processing section33outputs the data to an unillustrated higher-level device via the data output section26.

Also, the arithmetic processing section33deletes the data of the detection results stored in the storage section34, or outputs the data to the unillustrated higher-level device via the data output section26based on the operation of an unillustrated switch or the like.

The data of coordinates O1and O2of the detecting central points of the force sensors21A and21B and the data of the location coordinate of each contact-pressure sensor31in the x, y, z orthogonal coordinate system with the coordinate of the central point131(intersection of the plane with the rotation axis) of the steering wheel hub13in the rotational plane of the steering wheel rim11being the origin when the steering wheel rim11is in the position obtained when a vehicle is traveling straight are stored in advance in the storage section34. The arithmetic processing section33calculates a distance between the respective coordinates based on the data.

The contact-pressure sensors31in each of the first and second divided portions11A and11B of the steering wheel rim11are numbered in order from the one arranged in one end of the divided portions11A and11B. The coordinate of each contact-pressure sensor31is stored corresponding to the number in the storage section34.

Next, the processing operation of the arithmetic processing section33will be described in detail with reference toFIGS. 7 to 9.

The force sensors21A and21B detect forces and moments represented by the x, y, z orthogonal coordinate with the detecting central points O1and O2being the center, and output the detection result. Also, each of the contact-pressure sensors31outputs an electric signal indicating the contact pressure of a driver's hand. Only the contact-pressure sensors31existing in gripped regions ER1and ER2by driver's hands output the electric signals indicating the contact pressure obtained when gripped by a driver.

The arithmetic processing section33obtains the data of the contact pressure detected by each contact-pressure sensor31and the data of the force and the moment detected by each force sensor21A and21B via the sensor interface32(SB1, SB2). The arithmetic processing section33stores the respective data in the storage section34with the detection time data by correlating the respective data with the coordinate data of each sensor (SB3).

Moreover, the arithmetic processing section33calculates the coordinates of force applied points FP1and FP2based on the detection result of each sensor and the coordinate data of each sensor (SB4), and also, calculates forces and moments applied to the force applied points FP1and FP2(SB5).

In the arithmetic processing section33of the present embodiment, in order to obtain the force applied point FP1in the divided portion11A, for example, the coordinate of the force applied point FP1is obtained by using a known weighted average obtained from a contact pressure distribution C:[(θ1, p1), (θ2, p2), (θ3, p3) to (θn, pn)] by the product of an angle θ from a y axis132passing through the origin131of the orthogonal coordinate to each contact-pressure sensor31existing in the gripped region ER1and a contact pressure p detected by each contact-pressure sensor31existing in the gripped region ER1as shown inFIG. 8. In the gripped region ER1ofFIG. 8, the coordinate of the force applied point FP1is obtained by using the weighted average obtained from the contact pressure distribution C using an angle θi and a detected pressure pi of a contact-pressure sensor31i, an angle θ(i+1) and a detected pressure p(i+1) of a contact-pressure sensor31(i+1), an angle θ(i+2) and a detected pressure p(i+2) of a contact-pressure sensor31(i+2), and an angle θ(i+3) and a detected pressure p(i+3) of a contact-pressure sensor31(i+3). The force applied point F22in the gripped region ER2is similarly obtained. Also, a pressure peak position in a pressure distribution detected by each contact-pressure sensor31may be simply obtained as the force applied point.

After that, the arithmetic processing section33stores the calculation results of the forces and the moments at the force applied points in the storage section34with the coordinate data of each sensor and the detection time data described below (SB6). Also, the arithmetic processing section33outputs the data to the unillustrated higher-level device via the data output section26(SB7).

Next, the arithmetic processing section33resets the counted time of a timer (SB8), and starts to count time. When a counted time T of the timer reaches a predetermined time T1or more (SB9), the process moves to the process of SB1described above and the above processes are repeated.

Also, a force FFP1and a moment MFP1at the force applied point FP1described above can be calculated by using the Equation (1) and the Equation (2) described above. A force FFP2and a moment MFP2at the force applied point FP2can be similarly calculated.

With the steering operation force detecting apparatus10B having the above configuration, the contact pressure of a driver's hand on the steering wheel rim11is detected by the contact-pressure sensors31arranged in each of the divided portions11A and11B of the steering wheel rim11. Also, the force applied points FP1and FP2are obtained based on the contact pressure distribution obtained by the contact-pressure sensors31. Moreover, the forces and the moments at the force applied points FP1and FP2are calculated based on the detection results, and the calculation results are output. Therefore, it is possible to know in detail how much force or moment is applied to the force applied points F21and FP2on the steering wheel rim11during a steering operation. Accordingly, in the performance evaluation or the like of new-model cars and tires by using the apparatus of the present invention, it is possible to know in detail and in real-time the sense of driving during steering by a driver as the data of the forces or the moments applied to the steering wheel rim (steering wheel)11gripped by the driver during steering. The present invention can be thereby effectively utilized in the performance evaluation or the like.

FIGS. 10 to 15illustrate the third embodiment of the present invention.FIG. 10is a block diagram illustrating an electrical system circuit of a steering operation force detecting apparatus according to the third embodiment of the present invention.FIG. 11is a configuration diagram illustrating the main portion of the steering operation force detecting apparatus according to the third embodiment of the present invention.FIGS. 12 to 14are views explaining a detection operation according to the third embodiment of the present invention.FIG. 15is a flowchart explaining a processing operation according to the third embodiment of the present invention.

In the drawings, the same components as those in the first and second embodiments described above are assigned the same reference numerals to omit the description.

In a steering operation force detecting apparatus10C of the third embodiment, a steer angle sensor41is provided in addition to the configuration of the second embodiment, and a processing unit20C corresponding thereto is provided.

The steer angle sensor41is provided in the steering wheel hub13, and detects a steer angle δ of the steering wheel rim11to output an electric signal corresponding to the detection result to a sensor interface.

The processing unit20C includes a sensor interface42, an arithmetic processing section43, a storage section44, and the data output section26.

The sensor interface42supplies driving power to the steer angle sensor41, the force sensors21A,21B and the plurality of contact-pressure sensors31. Also, electric signals output from the sensors are input to the sensor interface42. The sensor interface42outputs the detection result of each sensor to the arithmetic processing section43as digital data.

The arithmetic processing section43is mainly constituted by a known CPU and a memory, and operates based on a program stored in advance in the memory. Also, the detection result of each sensor is input from the sensor interface42to the arithmetic processing section43at predetermined time intervals (for example, at one-second intervals). The arithmetic processing section43obtains a force applied point based on the contact pressure as described below. Furthermore, the arithmetic processing section43calculates a force and a moment at the force applied point, and stores the result in the storage section44with the steer angle δ, the coordinate data of each sensor and the detection time data described below. The arithmetic processing section43transforms the coordinates of the force and the moment applied to the force applied point as described below, and stores the data of the coordinates of the force applied point and the force and the moment applied to the force applied point after transformation in the storage section44. Moreover, the arithmetic processing section43outputs the data to an unillustrated higher-level device via the data output section26.

Also, the arithmetic processing section43deletes the data of the detection results stored in the storage section44, or outputs the data to the unillustrated higher-level device via the data output section26based on the operation of an unillustrated switch or the like.

The data of coordinates O1and O2of the detecting central points of the force sensors21A and21B and the data of the location coordinate of each contact-pressure sensor31in the x, y, z orthogonal coordinate system with the coordinate of the central point131(intersection of the plane with the rotation axis) of the steering wheel hub13in the rotational plane of the steering wheel rim11being the origin when the steering wheel rim11is in the position obtained when a vehicle is traveling straight are stored in advance in the storage section44. The arithmetic processing section43calculates a distance between the respective coordinates based on the data.

The contact-pressure sensors31in each of the first and second divided portions11A and11B of the steering wheel rim11are numbered in order from the one arranged in one end of the divided portions11A and11B. The coordinate of each contact-pressure sensor31is stored corresponding to the number in the storage section44.

Next, the processing operation of the arithmetic processing section43will be described in detail with reference toFIGS. 13 to 15.

The force sensors21A and21B detect forces and moments represented by the x, y, z orthogonal coordinate with the detecting central points O1and O2being the center, and output the detection result. Also, each of the contact-pressure sensors31outputs an electric signal indicating the contact pressure of a driver's hand. Only the contact-pressure sensors31existing in gripped regions ER1and ER2by driver's hands output the electric signals indicating the contact pressure obtained when gripped by a driver.

The arithmetic processing section43obtains the data of the contact pressure detected by each contact-pressure sensor31, the data of the force and the moment detected by each force sensor21A and21B, and the data of the steer angle δ detected by the steer angle sensor41via the sensor interface42(SC1, SC2, SC3). The arithmetic processing section43stores the respective data in the storage section44with the detection time data by correlating the respective data with the coordinate data of each sensor (SC4).

Moreover, the arithmetic processing section43calculates the coordinates of force applied points FP1and FP2based on the detection result of each sensor and the coordinate data of each sensor (SC5), and also, calculates forces and moments applied to the force applied points FP1and FP2(SC6).

In the arithmetic processing section43of the present embodiment, in order to obtain the force applied point FP1in the divided portion11A, for example, the coordinate of the force applied point FP1is obtained by using a known weighted average obtained from a contact pressure distribution C:[(θ1, p1), (θ2, p2), (θ3, p3) to (θn, pn)] (n is a natural number) by the product of an angle θ from a y axis132passing through the origin131of the orthogonal coordinate to each contact-pressure sensor31existing in the gripped region ER1and a contact pressure p detected by each contact-pressure sensor31existing in the gripped region ER1as in the second embodiment described above. The force applied point FP2in the gripped region ER2is similarly obtained. Also, a pressure peak position in a pressure distribution detected by each contact-pressure sensor31may be simply obtained as the force applied point.

After that, the arithmetic processing section43stores the calculation results of the forces and the moments applied to the force applied points FP1and FP2in the storage section44with the coordinate data of each sensor and the detection time data described below, and performs a coordinate transformation of the forces and the moments applied to the force applied points FP1and FP2(SC7). In the coordinate transformation, the coordinate is transformed into an x′, y′, z′ orthogonal coordinate in which the horizontal direction in the rotational plane of the steering wheel rim11is an x′ axis and the direction orthogonal to the x′ axis in the plane is a y′ axis with the coordinate of the central point131(intersection of the plane with the rotation axis) of the steering wheel hub13in the rotational plane being the origin.

After that, the arithmetic processing section43stores the data of the forces and the moments applied to the force applied points FP1and FP2represented by the coordinate-transformed orthogonal coordinate system in the storage section44(SC8). Also, the arithmetic processing section43outputs the data obtained from each sensor with the detection time data and the calculated data to the unillustrated higher-level device via the data output section26(SC9).

Next, the arithmetic processing section43resets the counted time of a timer (SC10), and starts to count time. When a counted time T of the timer reaches a predetermined time T1or more (SC11), the process moves to the process of SC1described above and the above processes are repeated.

Also, a force FFP1and a moment MFP1at the force applied point F21described above can be calculated by using the Equation (1) and the Equation (2) described above. A force FFP2and a moment MFP2at the force applied point FP2can be similarly calculated.

As shown inFIG. 14, the coordinates of a pushing/pulling force, a vertical force and a moment at each of the force applied points FP1and FP2may be transformed into an x″, y″, z″ orthogonal coordinate system in which the tangential direction of the steering wheel rim11is a y″ axis and the normal direction is an x″ axis with the force applied points FP1and FP2being the origin. Here, the force in the tangential direction is a force for generating steering torque.

With the steering operation force detecting apparatus10C having the above configuration, the contact pressure of a driver's hand on the steering wheel rim11is detected by the contact-pressure sensors31arranged in each of the divided portions11A and11B of the steering wheel rim11. Also, the force applied points FP1and FP2are obtained based on the contact pressure distribution obtained by the contact-pressure sensors31. Moreover, the forces and the moments at the force applied points FP1and FP2are calculated based on the detection results, and the calculation results are output. Therefore, it is possible to know in detail how much force or moment is applied to the force applied points FP1and FP2on the steering wheel rim11during a steering operation. Accordingly, in the performance evaluation or the like of new-model cars and tires by using the apparatus of the present invention, it is possible to know in detail and in real-time the sense of driving during steering by a driver as the data of the forces or the moments applied to the steering wheel rim (steering wheel)11gripped by the driver during steering. The present invention can be thereby effectively utilized in the performance evaluation or the like of new-model cars and tires.

Each of the embodiments described above is one example of the present invention, and the present invention is not limited to the configuration of each of the above embodiments. Although the steering wheel rim11is divided into two portions of the two divided portions11A and11B in the above embodiments, the steering wheel rim11may be divided into three or more portions, for example. Also, it is preferable that the method of obtaining the force applied points FP1and FP2, the coordinate system or the like are appropriately determined according to data usage or the like.

INDUSTRIAL APPLICABILITY

It is possible to know in detail how much force or moment is applied to the force applied points on the steering wheel rim during a steering operation from the calculation results of the forces and the moments at the force applied points of driver's hands which grip the divided portions of the steering wheel rim. Accordingly, in the performance evaluation or the like of new-model cars and tires by using the apparatus of the present invention, it is possible to know in detail and in real-time the sense of driving during steering by a driver as the data of the forces or the moments applied to the steering wheel rim (steering wheel) gripped by the driver during steering. The present invention can be thereby effectively utilized in the performance evaluation or the like of new-model cars and tires.