JP2003252223A - Steering angle detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To utilize and accurately detect steering angle of a steering wheel even immediately after the on-operation of an ignition switch. <P>SOLUTION: A steering device comprises a steering angle sensor 62 for detecting the steering angle of a steering wheel 13, controls the rotation of an electric motor 67 according to the steering angle detected by the steering angle sensor 62 to steer right and left front wheels 44a and 44b. Steering reaction mechanisms such as a hydraulic cylinder 15 and springs 19a and 19b mechanically generating steering reactions and a steer torque sensor 63 are installed in an input part 10 having the steering wheel 13. The steer torque detected by the steer torque sensor 63 corresponds with the steer reaction, or is generally in proportion to the steer angle. By using them, before the zero-point of the steer angle sensor 62 is corrected, the steer angle is estimated and utilized based on the detected steer torque. Also, when the detected steer torque lowers below a specified value or less, the zero-point of the steer angle sensor 62 is corrected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering angle detecting device for detecting a steering angle of a steering wheel for steering a vehicle.

[0002]

2. Description of the Related Art Conventionally, a steering angle detecting device for detecting the steering angle of a steering wheel based on the rotation angle of the steering wheel is well known. In this steering angle detecting device, since the steering handle is rotated one or more times, it is difficult to detect the absolute steering angle indicating the rotation angle of the steering handle from the reference rotation position immediately after the ignition switch is turned on.
To solve this point, for example, Japanese Patent Laid-Open No. 6-99833.
In the publication, when the ignition switch is turned off, the absolute steering angle of the steering wheel at that time is stored in a memory, and the absolute steering angle stored in the memory is read out when the ignition switch is turned on. In the subsequent detection of the absolute steering angle, the read absolute steering angle is used.

[0003]

However, even after the ignition switch is turned off, the steering wheel may rotate for some reason. In this case, the steering angle of the steering wheel when the ignition switch is turned on may differ from the steering angle stored in the memory when the ignition switch is turned off, and the steering angle of the steering wheel may not be detected accurately. There is.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to make it possible to accurately detect the steering angle of the steering wheel even immediately after the ignition switch is turned on. It is to provide a detection device.

In order to achieve the above object, a feature of the present invention is that a steering reaction force is applied to a steering operation of a steering wheel, the steering reaction force increasing as the absolute steering angle from the reference rotational position of the steering wheel increases. A force mechanism, steering torque detecting means for detecting a steering torque for steering the steering wheel, and an absolute steering angle from the reference rotational position of the steering wheel based on the steering torque detected by the steering torque detecting means. The steering angle estimating means is provided.

According to the features of the present invention having such a configuration, the steering torque detected by the steering torque detecting means opposes the steering reaction force applied by the steering reaction force mechanism, and although the direction is different, The magnitude is equal to the steering reaction force. Further, this steering reaction force increases as the absolute steering angle from the reference rotational position of the steering wheel increases. Therefore, the steering torque detected by the steering torque detecting means has a predetermined relationship with the absolute steering angle from the reference rotational position of the steering wheel. Thereby, the steering angle estimating means can estimate the absolute steering angle using the detected steering torque, even immediately after the ignition switch is turned on and before the reference rotational position of the steering angle sensor is detected, The absolute steering angle can be used.

Another feature of the present invention is a steering reaction force mechanism for applying a steering reaction force increasing with an increase in an absolute steering angle from a reference rotational position of the steering handle to a steering operation of the steering handle, The steering angle detection means for detecting the steering angle of the steering wheel, the steering torque detection means for detecting the steering torque for steering the steering wheel, and the steering torque detected by the steering torque detection means are below a predetermined value. And a steering angle correction means for correcting the steering angle detected by the steering angle detection means so as to represent the absolute steering angle from the reference rotational position.

In the other features of the present invention having such a configuration, as described above, the steering torque corresponds to the steering reaction force, and the steering reaction force is the reference of the steering wheel by the steering reaction force mechanism. It increases as the absolute steering angle from the rotational position increases. Therefore, if the steering torque is equal to or less than the predetermined value, it means that the steering wheel is near the reference position. Accordingly, the steering angle correction means can accurately correct the steering angle detected by the steering angle detection means so as to represent the absolute steering angle from the reference rotational position, so that the highly accurate absolute steering angle can be used. become.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the whole steering device of a vehicle to which a steering angle detecting device according to the present invention is applied. This steering device includes an input unit 10 that converts a steering force input by a driver into a fluid pressure, and an output unit 20 that converts the converted fluid pressure into a rotational force and outputs the converted rotational force. A fluid pressure transmission unit 30 that transmits a fluid pressure from the input unit 10 to the output unit 20 is provided.

The input unit 10 is a rotational force-propulsion force conversion mechanism 1.
0a and a propulsive force-fluid pressure conversion mechanism 10b. The rotational force-propulsion force conversion mechanism 10a includes a screw rod 11 supported by a support member (not shown) so as to be displaceable in the axial direction and non-rotatable around the axis, and a ball (not shown) on the outer peripheral surface of the screw rod 11 It is composed of a screwed nut 12, and is constituted by a ball screw mechanism that propels the screw rod 11 in the axial direction by the rotation of the nut 12. The reverse efficiency of this ball screw mechanism is set high. The nut 12 is integrally rotated with the rotary shaft 14 on the inner peripheral surface of the lower end portion of the cylindrical rotary shaft 14 which is connected to the steering wheel 13 which is rotationally operated by the driver so as to integrally rotate at the upper end. It is fixed.

The propulsion-fluid pressure conversion mechanism 10b comprises a hydraulic cylinder 15, a piston rod 16 and a piston 17 which are housed in the hydraulic cylinder 15 so as to be liquid-tight and axially displaceable. Converts the axial thrust of to hydraulic pressure. The piston rod 16 is
It is formed integrally with the lower end of the screw rod 11. The piston 17 has the same pressure receiving area with respect to its displacement in both axial directions. The hydraulic cylinder 15 is divided into two oil chambers 15a and 15b by a piston 17 and has ports 15c and 15d communicating with the respective oil chambers 15a and 15b at both ends in the axial direction thereof, and the axial direction thereof. Has ports 15e and 15f communicating with the oil chambers 15a and 15b, respectively.

The ports 15c and 15d allow the hydraulic oil to flow out to the oil passages 31 and 32 constituting the fluid pressure transmitting portion 30 by the displacement of the piston rod 16 in the axial direction. Port 15
Reference characters e and 15f prevent negative pressure from being generated in the rear chamber when the piston 17 is displaced from the neutral position, and are commonly connected to the reservoir 18. These ports 15e, 1
When the hydraulic oil 5f flows out from the one oil chamber 15a (or 15b) through the one port 15c (or 15d), 5f breathes the hydraulic oil from the reservoir 18 into the other oil chamber 15b (or 15a). Supply.

Further, each oil chamber 15a of the hydraulic cylinder 15 is
Coil springs 19a and 19b in an initially compressed state for accommodating a restraining load are housed in 15b, respectively. The coil springs 19a and 19b constantly urge the piston rod 16 and the piston 17 to the neutral position, and give the piston rod 16 and the piston 17 a neutral returning force that increases as they move away from the neutral position. Therefore, the coil spring 19
Each of a and 19b has a neutral position returning function and a steering reaction force applying function. Further, both inner bottom walls of the hydraulic cylinder 15 limit the displacement of the piston 17 in the axial direction within a predetermined range, and have a limiting function of limiting the amount of displacement of the piston rod 16 from the neutral position within the predetermined range. .

The output unit 20 is a fluid pressure-propulsion force conversion mechanism 2
0a and a propulsion-rotational force conversion mechanism 20b. The fluid pressure-propulsion force conversion mechanism 20a includes the hydraulic cylinder 2
1 and a piston rod 22 and a piston 23 housed in the hydraulic cylinder 21 so as to be liquid-tight and displaceable in the axial direction.
It is converted into propulsive force in the axial direction of. The hydraulic cylinder 21 is
It is divided into two oil chambers 21a, 21b by a piston 23, and each oil chamber 21a, 21b
21b, ports 21c, 21d, 21 respectively communicating with 21b.
e, 21f. The ports 21c and 21d communicate with the oil passages 31 and 32, respectively, which form the fluid pressure transmission unit 30. The ports 21e and 21f are the communication control valve 2
It communicates with the oil passages 31 and 32 via 4 and 25, respectively.

The communication control valves 24 and 25 are electromagnetic switching valves, which are kept closed in the drawing when not energized and switched to open when energized. The piston rod 22 is provided in each of the oil chambers 21a and 21b of the hydraulic cylinder 21.
It is displaced in the axial direction by supplying and discharging hydraulic oil to and from. The piston 23 has the same pressure receiving area with respect to its displacement in both axial directions. Further, in the present embodiment, the pressure receiving area of the piston 23 is equal to the pressure receiving area of the piston 17 of the propulsion-fluid pressure conversion mechanism 10b.

Further, each oil chamber 21a of the hydraulic cylinder 21 is
21b accommodates coil springs 26a and 26b in an initially compressed state for applying a restraining load. The coil springs 26a and 26b constantly urge the piston rod 22 and the piston 23 to the neutral position, and give the piston rod 22 and the piston 23 a neutral return force that increases as they move away from the neutral position. Therefore, the coil spring 26
a and 26b have a neutral position returning function. Also,
Both inner bottom walls of the hydraulic cylinder 21 limit the displacement of the piston 23 in the axial direction within a predetermined range so that the piston rod 2
2 has a limiting function of limiting the displacement amount from the neutral position within a predetermined range.

The propulsion-rotational force converting mechanism 20b includes a screw rod 27 supported by a support member (not shown) so as to be displaceable in the axial direction and non-rotatable around the axis, and a ball (not shown) on the outer peripheral surface of the screw rod 27. And a nut 28 that is screwed through the screw rod 27, and is configured by a ball screw mechanism that applies a rotational force around the axis to the nut 28 by the displacement of the screw rod 27 in the axial direction. In addition,
The reverse efficiency of this ball screw mechanism is set high.
The screw rod 27 is formed integrally with the lower end of the piston rod 22. The nut 28 is provided on the inner peripheral surface of the upper end portion of the cylindrical rotary shaft 29.
It is fixed so as to rotate together with.

The rotary shaft 29 is formed integrally with the pinion gear 42 via the connecting shaft 41, and rotates integrally with the pinion gear 42. The pinion gear 42 meshes with the rack teeth of the rack shaft 43. The rack shaft 43 is
Left and right front wheels 44a, 44b as steered wheels are rotatably connected at both ends thereof through tie rods and knuckle arms (not shown), and the left and right front wheels 44a, 44b are steered by axial displacement.

As described above, the fluid pressure transmitting section 30 is provided with the oil passages 31 and 32 provided between the hydraulic cylinder 15 of the input section 10 and the hydraulic cylinder 21 of the output section 20. Input cutoff control valves 33 and 34 are provided in the oil passages 31 and 32, respectively. Input cutoff control valve 33, 34
Is composed of an electromagnetic switching valve, which is maintained in an open state in the drawing when it is not energized and is switched to a closed state when it is energized.

Further, the oil passages 31, 32 of the fluid pressure transmitting portion 30
A steering simulator section 50 is interposed between them. The steering simulator section 50 includes a hydraulic cylinder 51 and simulator cut valves 52 and 53. The hydraulic cylinder 51 includes a piston 54 that is fluid-tightly slidable in the axial direction.
And the ports 51c and 51d communicating with the two oil chambers 51a and 51b partitioned by the piston 54. The oil chambers 51a and 51b of the hydraulic cylinder 51 respectively house coil springs 55a and 55b in an initially compressed state in order to apply a restraining load. The coil springs 55a and 55b are connected to the piston 54
Is always biased to the neutral position, and a neutral return force that increases as the piston 54 moves away from the neutral position is applied to the piston 54.

The simulator cut valve 52 is connected to the oil passage 3
1 and the port 51c of the hydraulic cylinder 51. The simulator cut valve 53 is interposed between the oil passage 32 and the port 51d of the hydraulic cylinder 51. The simulator cut valves 52, 53 are both electromagnetic switching valves, and are kept closed in the drawing when not energized and switched to open when energized.

Next, the electric control unit of the steering system will be described. The electric control unit includes a hydraulic pressure sensor 61a,
61b, 61c, 61d, a steering angle sensor 62, a steering torque sensor 63, a steering angle sensor 64, and a traveling state sensor group 65 are provided. The hydraulic pressure sensor 61a detects the hydraulic pressure of the oil passage 31 between the hydraulic cylinder 15 and the input cutoff control valve 33. The hydraulic pressure sensor 61b is used for the hydraulic cylinder 15
The oil pressure in the oil passage 32 between the control valve 34 and the input cutoff control valve 34 is detected. The oil pressure sensor 61c is the input cutoff control valve 33.
The hydraulic pressure of the oil passage 31 between the hydraulic cylinder 21 and the hydraulic cylinder 21 is detected. The hydraulic pressure sensor 61d detects the hydraulic pressure of the oil passage 32 between the input cutoff control valve 34 and the hydraulic cylinder 21.

The steering angle sensor 62 detects the steering angle of the steering wheel 13. This steering angle sensor 62
Is composed of, for example, a rotary encoder assembled to the rotary shaft 14 and a counter incorporated in an electronic control circuit 80, which will be described later, and has a phase shift of π / 2 output from the rotary encoder according to the rotation of the steering wheel 13. The steering angle of the steering wheel 13 is detected by counting up or down the two-phase pulse train signal according to the rotation direction of the steering wheel by the counter. The counter may be a hardware circuit built in the electronic control circuit 80 or may be controlled by a program.

However, the steering wheel 13 makes one rotation or more, that is, makes an angle of 2π or more. Therefore, in order to detect the absolute steering angle of the steering wheel 13 from the reference rotational position, this type of steering angle sensor 62
Reference rotational position of the steering wheel 13 (that is, neutral position)
Need to detect. The absolute steering angle becomes “0” when the steering wheel 13 is at the reference rotation position,
The steering wheel 13 represents the steering angle from the reference rotational position to the left and right with negative and positive values.

The steering torque sensor 63 is the steering wheel 1
The steering torque applied to the steering wheel 13 for steering operation No. 3 is detected. The steering torque opposes the steering reaction force by the springs 19a, 19b, 55a, 55b and the like, and although the direction is opposite, the magnitude thereof is equal to the steering reaction force. Further, as the steering torque sensor 63, one capable of self-detecting the zero point is used.

The steering torque sensor 63 is shown in FIG.
As shown in, a fixed member 71 and a movable member 72 are provided. The fixing member 71 is formed in a cylindrical shape having an outer cylinder 71b and an inner cylinder 71c connected by an annular portion 71a. The outer cylinder 71b is fixed to a support member (not shown) on the vehicle body side that rotatably supports the rotary shaft 14. The inner cylinder 71c has a female screw formed on its inner peripheral surface. The movable member 72 includes a column portion 72a and the column portion 72a.
and a disc portion 72b integrally formed at one end of a. The cylindrical portion 72a has an inner cylinder 71 of the fixing member 71 on the outer peripheral surface thereof.
A male screw that is screwed with the female screw of c is integrally formed,
In accordance with the rotation, it moves back and forth in the inner cylinder 71c in the axial direction. The disk portion 72b rotates in conjunction with the rotation of the rotary shaft 14 and is engaged with the rotary shaft 14 so as to be displaced in the axial direction with respect to the rotary shaft 14 during the rotation.

On the outer circumference of the cylindrical portion 72a of the movable member 72, elastically deformable U-shaped beams 73 and 74 having through holes 73a and 74a formed in the center are both compressed inward. It is assembled in the state (bent). The beam 73 has a movable member 72 on the outer surface of the central portion.
Of the fixing member 71 is in contact with an annular protrusion 72c integrally formed with the disk portion 72b of the fixing member 71.
Is in contact with one surface. The beam 74 is in contact with one surface of the first nut 75 screwed to the cylindrical portion 72a of the movable member 72 at the outer surface of the central portion thereof, and the other surface of the annular portion 71a of the fixed member 71 at the outer end thereof. Is in contact with.

A gap is provided between each inner side surface of the beams 73 and 74 and each end surface of the inner cylinder 71c of the fixed member 71 for allowing the movable member 72 to be displaced in the axial direction with respect to the fixed member 71. ing. On the other hand, the inner cylinder 71 of the fixing member 71
Each end face of c limits the displacement of the movable member 72 in the axial direction with respect to the fixed member 71 within a predetermined amount, and the axial displacement of the movable member 72 with respect to the fixed member 71 is at the central portions of the beams 73, 74. It is prohibited when each inner surface comes into contact with each end surface of the cylinder 71c.

On the other surface of the first nut 75, in order to realize a double nut structure, a second nut 76 screwed to the cylindrical portion 72a of the movable member 72 outside the first nut 75.
One side is in contact. Therefore, the first nut 75
Even if the movable member 72 rotates about the axis, the movable member 72
Does not displace in the axial direction. Also, the first and second
The nuts 75 and 76 constitute a load adjusting mechanism,
The initial bending amount of the beams 73 and 74 is adjusted by their axial positions.

Further, the beam 73 has first and second strain gauges 77a and 77b fixed thereto, and the beam 74 has third and fourth strain gauges 77c and 77d.
Is stuck. In the first to fourth strain gauges 77a to 77d arranged in this way, when the movable member 72 is displaced with respect to the fixed member 71 in the direction of the arrow in the figure, the beam 73 bends as the displacement amount of the movable member 72 increases. The amount is increased to include the first and second strain gauges 77a, 77b.
Outputs a voltage signal that increases as the displacement amount of the movable member 72 increases, as indicated by the solid line in FIG. On the other hand, at this time, the amount of deflection of the beam 74 decreases, and the third and fourth strain gauges 77c and 77d output voltage signals that decrease as the amount of displacement of the movable member 72 increases, as indicated by the broken line in FIG. To do. Further, when the movable member 72 is displaced with respect to the fixed member 71 in the direction opposite to the arrow direction in the drawing, the tendency of the output voltage of the first to fourth strain gauges 77a to 77d is opposite to the above case.

In this case, the movable member 72 is displaced relative to the fixed member 71 by the springs 19a, 19b, 55a, 5
This is a movement against the steering reaction force due to 5b or the like. Also,
This steering reaction force is a force that balances the steering torque applied to the steering wheel 13 by the driver. Therefore, if the movable member 72 is displaced in the arrow direction of FIG. 2 with respect to the fixed member 71 by the rotation of the steering handle 13 to the right from the reference rotational position (neutral position), the first and second distortions are generated. The voltage output of the gauges 77a, 77b increases as the steering torque in the right direction increases, as shown by the solid line in FIG. At this time, the voltage outputs of the third and fourth strain gauges 77c and 77d decrease as the wavy line in FIG. 3 as the steering torque in the right direction increases. On the contrary, the steering wheel 1
When rotating from the reference rotational position of No. 3 to the left, the first to fourth strain gauges 77a to 77d have the steering wheel 13
A tendency opposite to the case of the rotation from the reference rotation position to the right is shown.

Therefore, in the steering torque sensor 63 constructed as described above, the first to fourth strain gauges 77a are provided.
By correcting the voltage output from ~ 77d to the zero point, the steering torque applied to the steering wheel 13 can be detected.
The zero point correction will be described later. Also, first to
The steering torque can be detected using any of the voltage outputs of the fourth strain gauges 77a to 77d, but in the present embodiment, regarding the steering torque in the right direction, the first and second strain gauges 77a and 77b. Is obtained by averaging the voltage output from and is expressed as a positive value. Regarding the steering torque in the left direction, the third and fourth strain gauges 77
It is obtained by averaging the voltage output from c and 77d, and is represented by a negative value.

Further, the steering angle sensor 64 is provided with the left and right front wheels 44 depending on the rotation angle from the neutral position of the connecting shaft 41 or the axial displacement from the neutral position of the rack shaft 43.
The actual turning angles of a and 44b are detected. Regarding this actual turning angle, the neutral position of the left and right front wheels 44a, 44b is represented by "0", the steering angle in the right direction is represented by positive, and the steering by the left direction is represented by negative. The traveling state sensor group 65 includes a vehicle speed sensor that detects a vehicle speed, a yaw rate sensor that detects a yaw rate, a lateral acceleration sensor that detects a lateral acceleration, and the like, and detects the traveling states of various vehicles.

Further, the electric control unit is composed of the electric motor 6
It also has 6,67. The electric motor 66 functions as a steering reaction force actuator that applies a reaction force to the turning operation of the steering wheel 13, and applies a rotational force to the small gear 66.
It is transmitted to the rotary shaft 14 via a and the large gear 68. The small gear 66 a is formed integrally with the rotating shaft of the electric motor 66 and meshes with the large gear 68 fixed to the rotating shaft 14. The electric motor 67 functions as a steering actuator that steers the left and right front wheels 44a and 44b by its rotational force, and transmits the rotational force to the connecting shaft 41 via the small gear 67a and the large gear 69. The small gear 67a is formed integrally with the rotating shaft of the electric motor 67,
It meshes with a large gear 69 fixed to the connecting shaft 41.

These various sensors 61a, 61b, 61
c, 61d, 62, 63, 64, 65, electric motor 6
6, 67 and various valves 24, 25, 33, 34, 5
2, 53 are connected to the electronic control circuit 80. The electronic control circuit 80 has a microcomputer as a main component, and executes various programs to execute various sensors 61.
a, 61b, 61c, 61d, 62, 63, 64, 65
Signal from the electric motor 66, 67
And various valves 24, 25, 33, 34, 52, 53
Drive and switching control.

Next, the operation of the embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the electronic control circuit 80 starts executing the fail check program shown in FIG. The execution of this fail check program is started in step 100, and various sensors 61a to 61d, 6 are started in step 102.
The abnormality check of each part of the system including 2-65 is executed.

In this abnormality check, as a general rule, the abnormality check is performed in order from a highly reliable location.
Normality and abnormality are judged at each location. In addition, the abnormal portion may be specified by a combination of a plurality of types of abnormality determinations. Then, by such normality / abnormality determination, a flag indicating normality / abnormality is set for each location.

Part of this abnormality determination will be described with a specific example. For example, a portion including an electric control device portion, that is, various valves 24, 25, 33, 34, 5
2, 53, various sensors 61a to 61d, 62 to 65, and electric motors 66 and 67 are first checked for disconnection and short circuit. In this case, the disconnection and the short circuit are checked by appropriately inspecting the voltage applied to each part. Further, in the electronic control circuit 80, an initial check for abnormality check of each part of the microcomputer is also performed.

With respect to the hydraulic pressure sensors 61a to 61d, an abnormality is determined based on the hydraulic pressure detected by the hydraulic pressure sensors 61a to 61d. For example, both hydraulic pressure values detected by the input hydraulic pressure sensor 61a and the output hydraulic pressure sensor 61c are compared, and the input hydraulic pressure sensor 61b and the output hydraulic pressure sensor 6 are compared.
Both hydraulic pressure values respectively detected by 1d and 1d are compared. In this case, since the input cutoff control valves 33 and 34 are in the open state, as a result of the comparisons described above, it is determined that the hydraulic pressure sensor of the group whose hydraulic pressure values match is normal, and the hydraulic pressure sensor of the group whose hydraulic pressure values do not match. It is determined to be abnormal.

Regarding the steering torque sensor 63,
Abnormality is determined based on the output voltages output from the first to fourth strain gauges 77a to 77. For example, the first
The output voltage values from the second strain gauges 77a and 77b are compared with each other, and the output voltage values from the third and fourth strain gauges 77c and 77d are compared with each other. In this case, the first and second strain gauges 77a, 7a
Since 7b is fixed to the single beam 73 and the third and fourth strain gauges 77c and 77d are fixed to the single beam 74, the results of the respective comparisons should be almost the same. Therefore, if both comparisons match, the steering torque sensor 63 is determined to be normal, and if either comparison does not match, the steering torque sensor 63 is determined to be abnormal.

Further, the abnormality of the input motor system such as the ball screw mechanism including the electric motor 66, the screw rod 11 and the nut 12 and the oil pressure sensors 61a and 61b,
Electric motor 67, screw rod 27 and nut 2
Abnormalities in the output motor system such as the ball screw mechanism including 8 and the hydraulic pressure sensors 61c and 61d are also detected.

In detecting the abnormality of the input motor system, the input cutoff control valves 33, 34 and the simulator cut valve 5 are operated before the driver turns the steering wheel 13.
In a state in which 2, 53 are set to the closed state, a predetermined drive current is supplied to the electric motor 66 and the direction of the drive current is alternately changed to set the hydraulic pressure value detected by the hydraulic pressure sensors 61a and 61b to the predetermined value. Compare. In this state, if the input motor system is normal, both oil chambers 15 of the hydraulic cylinder 15
The oil pressure in one of the oil chambers a and 15b increases. Therefore, if the two hydraulic pressure values detected by the hydraulic pressure sensors 61c and 61d alternately exceed a predetermined value, it is determined that the input motor system and the hydraulic pressure sensors 61a and 61b are normal. In other cases, it is determined that one of the input motor system and the hydraulic pressure sensors 61a and 61b is abnormal. Further, at this time, if the normality of the input motor system is confirmed, it is determined that the hydraulic pressure sensors 61a and 61b are abnormal. If the normality of the hydraulic pressure sensors 61a and 61b is confirmed, the abnormality of the input motor system is determined.

On the other hand, in detecting the abnormality of the output motor system, the input cutoff control valves 33, 34 and the communication control valve 2 are operated before the driver turns the steering wheel 13.
In the state in which 4, 4 and 25 are set to the closed state, a predetermined drive current is passed through the electric motor 67 and the direction of the drive current is alternately changed so that the hydraulic pressure value detected by the hydraulic pressure sensors 61c and 61d and the predetermined value can be changed. Compare. In this state, if the output motor system is normal, both oil chambers 21 of the hydraulic cylinder 21 are
The oil pressure in one of the oil chambers a and 21b rises. Therefore, if both the hydraulic pressure values detected by the hydraulic pressure sensors 61c and 61d alternately exceed the predetermined value, it is determined that the output motor system and the hydraulic pressure sensors 61c and 61d are normal. At other times, it is determined that one of the output motor system and the hydraulic pressure sensors 61c and 61d is abnormal. Further, at this time, if the normality of the output motor system is confirmed, it is determined that the hydraulic pressure sensors 61c and 61d are abnormal. If the normality of the hydraulic pressure sensors 61c and 61d is confirmed, the abnormality of the input motor system is determined.

If the result of this abnormality determination is that the entire system is normal, a "Yes" determination is made in step 102 and the operation proceeds to step 104. In step 104, the steering system is set to the steer-by-wire mode. In this steer-by-wire mode, the left and right front wheels 44a and 44b are electrically steered, and the electronic control circuit 80
The input cutoff control valves 33 and 34 are energized to set these valves 33 and 34 in the closed state, respectively. At the same time, the electronic control circuit 80 controls the communication control valves 24, 25.
Then, the simulator cut valves 52 and 53 are energized to set the valves 24, 25, 52 and 53 to open states, respectively.

After the processing of step 104, step 1
At 06, execution of a steering control program described later is permitted. After that, the steering control program is repeatedly executed every predetermined short time. And step 11
At 4, the execution of this fail check program ends. It should be noted that this fail check program is repeatedly executed at predetermined time intervals even after this execution is completed. However, the abnormality check such as the initial check of the microcomputer which is necessary only at the initial stage is not performed when the fail check program is executed after the initial stage.

On the other hand, if a part of the system is abnormal, it is judged "No" in step 102 and step 108
Proceed to. In step 108, all valves 24, 2 are released to release the steer-by-wire mode.
De-energize 5, 33, 34, 52, 53.
As a result, the input cutoff control valves 33 and 34 are set to the open state, and the communication control valves 24 and 25 and the simulator cut valves 52 and 53 are set to the closed state. This state is maintained even when the electric system fails. In this state, the left and right front wheels 44a, 4a
4b is steered by hydraulic pressure as described later in detail.

After the processing of step 108, step 1
At 10, the execution of a steering control program to be described later is prohibited. After that, the steering control program is not executed. In step 112 after the processing in step 110, a warning lamp (not shown) that indicates the occurrence of the detected abnormality together with the occurrence location thereof is turned on to notify the driver of the occurrence of the abnormality. Then, in step 114, the execution of the fail check program is once ended.

During the execution of such a fail check program, the electronic control circuit 80 repeatedly executes the sensor output correction program every predetermined short time. The execution of this sensor output correction program is started in step 200 of FIG. 6, and it is determined in step 202 whether or not both the steering angle sensor 62 and the steering torque sensor 63 are normal. In this case, by checking the flag set by the process of step 102 of FIG. 5, it is determined whether both the sensors 62 and 63 are normal. In this case, if the abnormality check of both sensors 62 is not completed yet or if the check result is abnormal, it is determined as “No” in step 202, and this sensor output correction program is executed in step 216. finish. On the other hand, both sensors 6
If the abnormality check of Nos. 2, 63 is completed at least once and the check result is normal, it is determined as “Yes” in step 202, and the process proceeds to step 204.

In step 204, it is determined whether or not the zero point correction of the steering angle sensor 62 is completed based on the flag set by the processing in step 214 described later. If the zero point correction of the steering angle sensor 62 has not been completed, it is determined as “No” in step 204 and the process proceeds to step 206. In step 206, it is determined whether or not the zero point detection of the steering torque sensor 63 is completed based on the flag set by the process of step 208 described later. If the zero point detection of the steering torque sensor 63 is not completed, it is determined as “No” in step 206 and the process proceeds to step 208.

In step 208, the zero point detection process of the steering torque sensor 63 is performed. In this zero point detection processing, the average value of the first to fourth strain gauges 77a to 77d of the steering torque sensor 63 is calculated as the zero point Tro. The output voltages of the first and second strain gauges 77a and 77b are substantially equal to each other and the third and fourth strain gauges 77c and 77c are equal.
Both output voltages of 7d are almost equal. Further, as shown in FIG. 3, with respect to the displacement of the movable member 72 from the reference position to both sides, both the output voltages of the first and second strain gauges 77a and 77b and the third and fourth strain gauges 77c and 77d. Both output voltages of the above change with the same gradient in opposite directions centering on the zero point Tro. Therefore, the average value of the first to fourth strain gauges 77a to 77d of the steering torque sensor 63 indicates the zero point Tro of the output of the steering torque sensor 63.

In step 208, a flag indicating that the zero point detection of the steering torque sensor 63 is completed is also set. As a result, next step 2
In the determination process of 06, the determination is “Yes”, and the zero point detection process of the steering torque sensor 63 in step 208 is not executed. Then, the calculated zero point Tro is used for subsequent calculation of the absolute steering torque Tr.

After the processing of step 206 or 208, in step 210, the steering torque sensor 63 (first to first
The absolute steering torque Tr is calculated using the outputs of the fourth strain gauges 77a to 77d) and the calculated zero point Tro. Specifically, the first and second strain gauges 77a, 7a
If the average value of both output voltages of 7b is equal to or higher than the zero point Tro, the zero point Tro is subtracted from this average value and the subtracted value is set as the absolute steering torque Tr. The first and second strain gauges 7
The fact that 7a and 77b are larger than the zero point Tro corresponds to the state where the movable member 72 is displaced to the left in FIG. 2 while rotating to the right due to the rotation from the neutral position of the steering wheel 13 to the right. Since the subtraction result is positive, the absolute steering torque Tr in this case is positive, and this positive absolute steering torque Tr represents the steering torque when the steering handle 13 is rotated rightward.

Also, the third and fourth strain gauges 77c,
If the average value of both output voltages of 77d is equal to or greater than the zero point Tro,
The zero point Tro is subtracted from this average value, and the subtracted value is given a negative sign to obtain the absolute steering torque Tr. It should be noted that the fact that the third and fourth strain gauges 77c and 77d are equal to or greater than the zero point Tro means that the movable member 72 is rotated leftward from the neutral position of the steering wheel 13 and is rotated rightward in FIG. It corresponds to the displaced state. Since the subtraction result is positive, the absolute steering torque Tr in this case is
Is negative, and this negative absolute steering torque Tr represents the steering torque when the steering handle 13 is rotated leftward.

After the processing of step 210, step 2
At 12, it is determined whether the absolute value | Tr | of the absolute steering torque Tr is less than or equal to a small predetermined value ΔTr. This absolute steering torque Tr is equal in magnitude to the steering reaction force at the time of turning the left and right front wheels 44a and 44b, although its direction is opposite. Then, as will be described later in detail, the steering reaction force and the absolute steering torque Tr are
As shown in FIG. 4, when the steering wheel 13 is in the neutral position, it indicates “0”, and as the rotation angle from the neutral position of the steering wheel 13 to the left and right increases, that is, the steering angle θ.
It increases as the absolute value | θh | of h increases. Therefore, the absolute value of the absolute steering torque Tr |
The fact that Tr | is equal to or less than the predetermined value ΔTr means that the steering wheel 13 is in the neutral position.

As a result, if the absolute value | Tr | of the absolute steering torque Tr is not less than the predetermined value ΔTr, step 21
In step 2, it is determined to be “No”, that is, the steering wheel 13 is not in the neutral position, and in step 216, the execution of this sensor output correction program is ended. Therefore, in this case, when the sensor output correction program is executed, it is determined to be “No” in step 204 described above, and step 20
6, 208, 210, 212 (or step 206,
210, 212) is executed.

Then, the absolute value of the absolute steering torque Tr | T
If r | is equal to or less than the predetermined value ΔTr, it is determined “Yes” in step 212, that is, the steering wheel 13 is in the neutral position, and the process proceeds to step 214. In step 214, the counter in the electronic control circuit 80 forming a part of the steering angle sensor 62 is cleared to “0”,
The zero point correction process of the steering angle sensor 62 is executed. As a result, the count value of this counter becomes "0" when the steering wheel 13 is at the neutral position. Also,
When the steering wheel 13 is rotated rightward from the neutral position, the rotation angle of the steering wheel 13 is incremented from "0" and represented by a positive value. In addition, the steering wheel 13
When is rotated leftward from the neutral position, the rotation angle of the steering wheel 13 is counted down from "0" and represented by a negative value. In this specification, the corrected steering angle is referred to as an absolute steering angle θh.

Next, steering control of the left and right rear wheels 44a and 44b based on a steering control program repeatedly executed at predetermined time intervals will be described. The steering control program is permitted to be executed by the process of step 106 of FIG. 5, and in this state, the entire system is normal, and the steering device is operated by the process of step 104 of FIG. Set to steer-by-wire mode.

The execution of the steering control program is started in step 300 of FIG. 7, and it is determined in step 302 whether the zero point detection of the steering torque sensor 63 is completed. If the zero point detection is not completed, step 302
Is determined to be "No" at step 316, and the execution of the steering control program is ended at step 316. However, at the time when the execution of the steering control program is permitted by the process of step 106 of FIG. 5, normally, step 20 of FIG.
The zero point detection of the steering torque sensor 63 is completed by the process of 8, and the flag indicating the completion of the zero point detection is set. At least immediately after the execution of the steering control program is permitted, the zero point detection of the steering torque sensor 63 is completed.

If the zero point detection of the steering torque sensor 63 is completed in this way, it is determined to be "Yes" at step 302 and the routine proceeds to step 304. In step 304, the absolute steering torque Tr is calculated using the detected zero point Tro based on the output of the steering torque sensor 63 by the same processing as the processing of step 210 of FIG. 6 described above. Then, in step 306, it is determined whether the zero point correction of the steering angle sensor 62 is completed. This determination is made depending on whether or not the flag indicating the completion of the zero point correction is set by the processing in step 214 of FIG. 6 described above.

If the zero point correction of the steering angle sensor 62 has not been completed, a "No" determination is made at step 306 and the routine proceeds to step 308. In step 308, the absolute steering angle θh is calculated based on the calculated absolute steering torque Tr.
To calculate. As shown in FIG. 4, the absolute steering torque Tr and the absolute steering angle θh are absolute values of the absolute steering torque Tr |
Except for the region where Tr | is less than the predetermined value ΔTr, there is a proportional relationship, and a table representing this relationship is stored in advance in the microcomputer. Therefore, this step 30
In the process of 8, the absolute steering angle θh corresponding to the absolute steering torque Tr is calculated with reference to the table. The relationship between the absolute steering torque Tr and the absolute steering angle θh will be described in detail later when the generation of the steering reaction force is described.

After the processing in step 308, the electronic control circuit 80 executes the processing in step 314 to set the left and right front wheels 44.
The steering control is performed on the steering wheels a and 44b, and the steering control program is temporarily terminated at step 316. In this turning control, first, the calculated absolute steering angle θh is multiplied by a coefficient K to calculate a target turning angle K · θh. The coefficient K is
Although it may be a constant, it may be changed according to the traveling state of the vehicle such as vehicle speed, lateral acceleration, yaw rate detected by the traveling state sensor group 65. For example, when the vehicle speed is low, the coefficient K is increased, and when the vehicle speed is high, the coefficient K is increased.
Set smaller.

In step 314, the actual turning angle is input from the turning angle sensor 64, and the electric motor 67 is operated so that the actual turning angle becomes equal to the calculated target turning angle K · θh. Control the rotation of. The rotation of the electric motor 67 is transmitted to the pinion gear 42 via the small gear 67a, the large gear 68 and the connecting shaft 41. The rack shaft 43 is laterally displaced by the transmission of the rotation to the pinion gear 42, and the left and right front wheels 44a and 44b are steered according to the displacement of the rack shaft 43. As a result, the left and right front wheels 44a, 44b are steered in accordance with the target turning angle K · θh, that is, the absolute steering angle θh due to the rotational operation of the steering wheel 13.

As a result, the front left and right wheels 44a, 44b are not moved to the steering wheel 1 immediately after the ignition switch is turned on and before the zero point correction of the steering angle sensor 62 is completed.
The steering wheel is steered according to the absolute steering angle θh of 3.

On the other hand, while the left and right front wheels 44a and 44b are being steered by such a rotating operation of the steering wheel 13, the steering wheel 13 has the input section 10 and the steering simulator section 50.
The steering reaction force is applied. Specifically, when the steering handle 13 is rotated, this rotation is caused by the rotation shaft 1
4 is transmitted to the nut 12, and the nut 12 rotates about the axis. Due to the rotation of the nut 12, the screw rod 11 and the piston rod 16 move forward or backward in the axial direction against the repulsive force of the coil springs 19a and 19b. For example, when the steering wheel 13 is rotated rightward, the piston rod 16 moves forward (moves leftward in the drawing) against the repulsive force of the coil spring 19a.
To do. On the contrary, when the steering wheel 13 is rotated leftward, the piston rod 16 moves backward (moves rightward in the drawing) against the repulsive force of the coil spring 19b.

By moving the piston rod 16 forward, the oil chamber 1
The hydraulic oil in 5a flows into the oil chamber 51a of the hydraulic cylinder 51 through the simulator cut valve 52. As a result, the piston 54 is displaced downward in the drawing against the repulsive force of the coil spring 55b, and the hydraulic oil in the oil chamber 51b is
Hydraulic cylinder 1 via simulator cut valve 53
5 into the oil chamber 15b. Also, the piston rod 1
Due to the retreat of 6, the hydraulic oil in the oil chamber 15b is passed through the simulator cut valve 53 to the oil chamber 51 of the hydraulic cylinder 51.
flows into b. As a result, the piston 54 is displaced upward in the drawing against the repulsive force of the coil spring 55a, and the working oil in the oil chamber 51a is discharged from the simulator cut valve 52.
Through the oil chamber 15a of the hydraulic cylinder 15.
The excess or deficiency of the hydraulic oil flowing from the hydraulic cylinder 51 into the oil chambers 15a and 15b of the hydraulic cylinder 15 is determined by the port 15
It is covered by the hydraulic oil in the reservoir 18 via e and 15f.

As can be understood from the above description,
Steering reaction force is applied to the steering operation of the steering wheel 13 by the repulsive force of the springs 19a, 19b, 55a, 55b. This steering reaction force increases as the amount of displacement from the neutral position of the piston 17 and the piston 54 increases, so that a large steering reaction force is applied to the rotational operation of the steering handle 13 as the rotation angle increases. To be done. Since the driver is rotating the steering wheel 13 with the steering torque that overcomes the steering reaction force, the absolute steering torque Tr and the absolute steering angle θh.
The relationship with is as shown in FIG.

Returning again to the explanation of the steering control program of FIG. 7, if the zero point correction of the steering angle sensor 62 is completed, it is judged "Yes" at step 306, and the routine proceeds to steps 310 and 312. In step 310,
The zero-corrected steering angle sensor 62 (electronic control circuit 8
(Including the counter within 0), the absolute steering angle θh is input. In step 312, the spring 19
The mechanical steering reaction force by a, 19b, 55a, 55b is controlled to be increased or decreased by the electric motor 66. The reason why the increase / decrease control of the steering reaction force is performed after the zero point correction of the steering angle sensor 62 is completed is that the absolute steering torque T using the table showing the characteristics of FIG.
This is because it is possible to calculate the absolute steering angle θh based on r.

In the control of increasing or decreasing the steering reaction force by the electric motor 66, the rotation of the electric motor 66 is controlled while feeding back the absolute steering torque Tr detected by the steering torque sensor 63. The rotational force of the electric motor 66 is transmitted to the steering wheel 13 via the small gear 66a, the large gear 68 and the rotary shaft 14. Therefore, if the turning force by the electric motor 66 in the direction opposite to the turning direction of the driver is applied to the steering wheel 13, the steering reaction force is controlled to increase. On the contrary, the torque generated by the electric motor 66 in the same direction as the rotation direction of the driver is applied to the steering wheel 13.
The steering reaction force is controlled to be reduced.

In this case, for example, the electronic control circuit 80
The drive current for the electric motor 66 can be controlled based on the vehicle speed detected by the traveling state sensor group 65 and the absolute steering angle θh detected by the steering angle sensor 62. According to this, the steering reaction force is reduced to improve the turning performance of the vehicle when the vehicle is traveling at a low speed and a large steering angle, and the steering reaction force is increased when the vehicle is traveling at a high speed and straight to improve the traveling stability of the vehicle. As a result, it is possible to obtain an appropriate steering reaction force according to the traveling state of the vehicle.

After the processing of step 312, the electronic control circuit 80 controls the rotation of the electric motor 67 to steer the left and right front wheels 44a and 44b in the same manner as described above. However, in the steering control of the left and right front wheels 44a and 44b, the steering angle sensor 62
The absolute steering angle θh detected by is used. Thus, the left and right front wheels 44a and 44b can be steered by using the highly accurate absolute steering angle θh after the zero point correction is completed.

Thereafter, the steering control program shown in FIG. 7 is repeatedly executed at predetermined time intervals, and steps 312 and 31 are executed.
By the processing of No. 4, the left and right front wheels 44a, 44b are steered according to the rotation operation of the steering wheel 13 by the driver. In addition to the mechanical steering reaction force by the springs 19a, 19b, 55a, 55b, electric steering reaction force control by the electric motor 66 is added to the rotation operation of the steering wheel 13. However, if an abnormality occurs in the system due to the execution of the fail check program in FIG.
When the steer-by-wire mode of the steering device is released, execution of the steering control program of FIG. 7 is also prohibited.

Next, the operation in the released state of the steer-by-wire mode will be described. In this case, when the driver rotationally operates the steering wheel 13, the screw rod 11 and the piston rod 16 move forward or backward in the axial direction, as in the case of the steer-by-wire mode described above. In this case, the simulator cut valve 52,
Since 53 is in the closed state, the steering reaction force is given by the repulsion force of the coil springs 19a and 19b and the reaction force for moving the piston rod 22 of the output unit 20 described later in the axial direction.

When the steering handle 13 is rotated to the right, the piston rod 16 moves forward (moves to the left in the drawing), the hydraulic oil in the oil chamber 15a of the hydraulic cylinder 15 flows out from the port 15c, and the oil passage 31 to the oil chamber 21b of the hydraulic cylinder 21 via the input cutoff control valve 33
Inflow through 1c. As a result, the piston 23 and the piston rod 22 move forward (move to the left in the drawing), the hydraulic oil in the oil chamber 21a of the hydraulic cylinder 21 flows out from the port 21d, and passes through the oil passage 32 and the input cutoff control valve 34. Port 1 in the oil chamber 15b of the hydraulic cylinder 15
It flows in through 5d. In this state, the communication control valves 24 and 25 are open.

When the steering handle 13 is rotated counterclockwise, the piston rod 16 retracts (moves to the right in the figure), the hydraulic oil in the oil chamber 15b of the hydraulic cylinder 15 flows out from the port 15d, and the oil passage is formed. 32 to the oil chamber 21a of the hydraulic cylinder 21 via the input cutoff control valve 34 and the port 2
Inflow through 1d. As a result, the piston 23 and the piston rod 22 retract (move to the right in the drawing), the hydraulic oil in the oil chamber 21b of the hydraulic cylinder 21 flows out from the port 21c, and passes through the oil passage 31 and the input cutoff control valve 33. Port 1 in the oil chamber 15a of the hydraulic cylinder 15
Inflow through 5c. The excess or deficiency of the hydraulic oil flowing from the hydraulic cylinder 21 into the oil chambers 15a and 15b of the hydraulic cylinder 15 is caused by the reservoir 1 through the ports 15e and 15f.
It is covered by the hydraulic oil in 8.

The axial displacement of the piston rod 22 causes the nut 28 to rotate about its axis. The rotation of the nut 28 causes the rotation shaft 29 to integrally rotate, and the rotation of the rotation shaft 29 is transmitted to the pinion gear 42 via the connecting shaft 41. The rotation of the pinion gear 42 displaces the rack shaft 43 left and right to steer the left and right front wheels 44a and 44b.

As a result, even when the steer-by-wire mode is released, the driver applies a reaction force to the rotating operation of the steering wheel 13, and
The left and right front wheels 44a, 44b are steered in accordance with the rotation operation.

In the above embodiment, the steering angle sensor 62 is composed of a rotary encoder, but a rotary potentiometer may be used. However, also in this case, since the steering wheel 13 rotates for one rotation or more, the potentiometer and a counter for counting the number of rotations for each rotation angle 2π are required, and the zero point of the steering angle sensor 62 accompanied by the zero point detection of the potentiometer. The need for correction arises. In this zero point correction, in step 214 of FIG. 6 of the above embodiment, the zero point detection of the potentiometer is performed in addition to the reset of the counter as in the above embodiment. Also, step 3 in FIG.
When the absolute steering angle θh of 10 is input, the zero point correction process using the detected zero point may be performed.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of a vehicle steering system to which a steering angle detection device according to the present invention is applied.

FIG. 2 is a sectional view showing an example of the steering torque sensor of FIG.

FIG. 3 is a graph showing an output voltage characteristic of a strain gauge forming a steering torque sensor with respect to steering torque.

FIG. 4 is a graph showing a relationship between an absolute steering torque and an absolute steering angle.

5 is a flowchart showing a fail check program executed by the electronic control circuit (microcomputer) of FIG.

6 is a flowchart showing a sensor output correction program executed by the electronic control circuit (microcomputer) of FIG.

7 is a flowchart showing a steering control program executed by the electronic control circuit (microcomputer) of FIG.

[Explanation of symbols]

10 ... Input part, 10a ... Rotational force-propulsion force conversion mechanism, 10
b ... Propulsion-fluid pressure conversion mechanism, 13 ... Steering handle, 2
0 ... Output part, 20a ... Fluid pressure-propulsion force conversion mechanism, 20b
... Propulsion-rotational force conversion mechanism, 30 ... Fluid pressure transmission part, 3
3, 34 ... Input shutoff control valves, 44a, 44b ... Left and right front wheels, 50 ... Steering simulator section, 61a-61d ... Hydraulic pressure sensor, 62 ... Steering angle sensor, 63 ... Steering torque sensor, 64 ... Steering angle sensor, 65 ... Running state sensor group, 6
6, 67 ... Electric motor, 80 ... Electronic control circuit.

Claims (2)

[Claims] 1. A steering reaction force mechanism for applying a steering reaction force increasing with an increase in an absolute steering angle from a reference rotational position of the steering handle to a steering operation of the steering handle, and a steering handle for steering the steering handle. A steering torque detecting means for detecting a steering torque; and a steering angle estimating means for estimating an absolute steering angle from a reference rotational position of the steering wheel based on the steering torque detected by the steering torque detecting means. A characteristic steering angle detection device. 2. A steering reaction force mechanism that applies a steering reaction force that increases with an increase in an absolute steering angle from a reference rotational position of the steering handle to a steering operation of the steering handle, and a steering angle of the steering handle is detected. Steering angle detecting means, steering torque detecting means for detecting steering torque for steering the steering wheel, and detecting that the steering torque detected by the steering torque detecting means is below a predetermined value. Steering angle correction means for correcting the steering angle detected by the steering angle detection means so as to represent the absolute steering angle from the reference rotational position.