JP4772345B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that applies a steering assist force to a steering mechanism using an assist motor as a drive source.

2. Description of the Related Art Conventionally, in the above-described electric power steering apparatus, a steering angle of a steering shaft is detected using a steering angle sensor, and an output torque (steering assist force) of an assist motor is controlled by taking this detection value into account (for example, , See Patent Document 1).
JP 2002-316654 A

By the way, in the above prior art, a dedicated rudder angle sensor is required and a control system as a countermeasure against the rudder angle sensor failure is necessary, which may lead to an increase in cost and weight due to a complicated configuration. Therefore, improvement of such a point is desired.
Therefore, the present invention provides an electric power steering apparatus that can control the steering assist force in consideration of the steering angle of the steering shaft and can reduce cost and weight by simplifying the configuration.

As means for solving the above problems, the invention according to claim 1, in the assist motor electric power steering apparatus for applying a steering assist force to a steering mechanism (82) as a drive source (80), the voltage of the assist motor (82) And a steering angle calculating means (93d) for detecting a motor rotation speed based on the current and calculating a relative steering angle of the steering shaft (25) based on the motor rotation speed, and an operation of the steering shaft (25) . Reference position estimating means (93e) for estimating the turning reference position based on the steering wheel, and maximum turning detection means (101) for detecting the maximum turning of the steering shaft (25) , the turning reference position Is a position where the absolute turning angle of the steering shaft (25) is 0 degree,
When the maximum turning detection means (101) detects the maximum turning of the steering shaft (25), the reference position estimation means (93e) estimates the turning reference position of the steering shaft (25). And

  According to this configuration, by knowing the relative turning angle of the steering shaft (the turning angle from an arbitrary position) and the turning reference position (the turning reference state with respect to the vehicle body), relative to the turning reference position. It becomes possible to detect the turning angle, that is, the absolute turning angle of the steering shaft.

Further, when the steering shaft is turned to the maximum clockwise or counterclockwise, the absolute steering angle of the steering shaft that is set in advance to a predetermined angle can be known, and based on this, the steering reference position of the steering shaft (absolute The position at which the turning angle is 0 degree) is estimated, and the absolute turning angle of the steering shaft can be detected.

According to a second aspect of the present invention, in the electric power steering device (80) that applies the steering assist force to the steering mechanism using the assist motor (82) as a drive source, the motor rotation is performed based on the voltage and current of the assist motor (82). A turning angle calculation means (93d) for detecting the speed and calculating a relative turning angle of the steering shaft (25) based on the motor rotation speed, and a turning reference based on the operation of the steering shaft (25) Reference position estimating means (193e) for estimating the position, wherein the turning reference position is a position where the absolute turning angle of the steering shaft (25) is 0 degree, and relative to the steering shaft (25). When the change width of the turning angle reaches a predetermined value, the reference position estimating means (193e) And estimating a steering reference position of 5).

  According to this configuration, the range of change in the relative turning angle of the steering shaft (corresponding to the amount of change from the clockwise end to the counterclockwise end) has reached a predetermined value (corresponding to the amount of change between the left and right maximum turning). Sometimes, it is possible to know the absolute turning angles at the clockwise and counterclockwise ends of the change width of the steering shaft, and based on this, the steering reference position of the steering shaft (the position at which the absolute turning angle is 0 degree). ) And the absolute turning angle of the steering shaft can be detected.

According to the present invention, it is possible to finely control the steering assist force in consideration of the steering angle of the steering shaft, and to reduce cost and weight by eliminating the need for a dedicated steering angle sensor and its failure countermeasure. it can.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the directions such as front, rear, left and right in the following description are the same as those in the vehicle unless otherwise specified. In the figure, the arrow FR indicates the front of the vehicle, the arrow LH indicates the left side of the vehicle, and the arrow UP indicates the upper side of the vehicle.

  A saddle-ride type four-wheel vehicle (vehicle) 1 shown in FIG. 1 includes left and right front wheels 2 and rear wheels 3, which are relatively large-diameter low-pressure balloon tires, in front of and behind a small and lightweight vehicle body. This is a so-called ATV (All Terrain Vehicle) that has secured a large height and has improved the running ability mainly on rough terrain. The vehicle body frame 4 of the saddle-ride type four-wheel vehicle 1 is formed by integrally joining a plurality of types of steel materials by welding or the like. More specifically, the left and right closed loop structures are connected via a plurality of cross members. By connecting, a box structure that is long in the front-rear direction is formed at the center in the vehicle width direction.

  An engine 5 as a prime mover of the saddle-ride type four-wheel vehicle 1 is mounted at a substantially central portion of the body frame 4. The engine 5 is a water-cooled single-cylinder engine, and has a so-called vertical layout in which the rotation axis of the crankshaft is along the vehicle front-rear direction. Propeller shafts 8f and 8r are led out from the lower part of the engine 5 toward the front or the rear, respectively. It is connected to each front wheel 2 or rear wheel 3 through the rear reduction mechanism 12 or the like so that power can be transmitted. The front wheels 2 and the rear wheels 3 are suspended at the front or rear portion of the vehicle body frame 4 via independent suspension type front suspensions or rear suspensions (not shown).

  In the engine 5, a throttle body 17 is connected to the rear portion of the cylinder portion 7 that is erected on the crankcase 6, and an air cleaner case 18 is connected to the rear portion of the throttle body 17. On the other hand, the base end portion of the exhaust pipe 19 is connected to the front portion of the cylinder portion 7. The exhaust pipe 19 extends forward of the cylinder portion 7 and then turns back toward the rear, and its tip is connected to a silencer 21 disposed at the rear of the vehicle body.

  A fuel tank 22 and a saddle-ride type seat 23 are disposed in order from the front side at the center in the vehicle width direction at the upper part of the vehicle body of the saddle-ride type four-wheel vehicle 1. In addition, a bar-type handle 24 that forms left and right grips is disposed obliquely above and forward of the fuel tank 22. The handle 24 is fixed to an upper end portion of a steering shaft 25 that linearly extends up and down. A battery 94 as a power source for the vehicle is disposed below the rear portion of the seat 23.

  The steering shaft 25 is provided with an inclination so that the upper portion thereof is located rearward. A fuel tank 22 is located immediately behind the upper portion of the steering shaft 25, and a seat 23 is located immediately behind the fuel tank 22. Further, the engine 5 is positioned at a predetermined distance behind the lower portion of the steering shaft 25, and a radiator 26 for cooling the engine 5 is disposed in front of the lower portion of the steering shaft 25. Reference numeral 29 denotes an electric radiator fan.

  At the front part of the body frame 4, a resin body cover 31 that appropriately covers the front part of the vehicle body, a front fender 32 made of the same resin that covers each front wheel 2 from the upper side to the rear side, and a front made mainly of steel. A protector 33 and a front carrier 34 are attached. A rear fender 35 made of resin and a rear carrier 36 mainly made of steel are attached to the rear portion of the vehicle body frame 4 so as to cover each rear wheel 3 from above to the front.

Referring also to FIG. 2, at the front part of the vehicle body frame 4, the upper and lower ends of the steering shaft 25 are connected to an upper support bracket 54 or a lower support bracket 55 as a cross member that couples the closed loop structure. Each is supported.
Here, the saddle-ride type four-wheel vehicle 1 includes an electric power steering system (electric power steering device) 80 for reducing a steering operation force, that is, a front wheel steering force.

  The power steering system 80 includes a power assist motor 82 integrated actuator unit 81 provided at an intermediate portion of the steering shaft 25 and a power assist based on a detection value of a torque sensor (torque detection means) 91 in the actuator unit 81. It comprises a control unit 93 as an ECU (Electric Control Unit) for driving and controlling a motor (assist motor) 82.

  The lower end of the steering shaft 25 is coaxially connected to the input shaft 83 of the actuator unit 81, and the output shaft 84 of the actuator unit 81 that is coaxial with these is supported by the lower support bracket 55 via the shaft holder 55a. Is done. The shafts 83 and 84 are connected to each other through a torsion bar 92 that is a part of the torque sensor 91 in the housing 85 of the actuator unit 81.

The housing 85 of the actuator unit 81 is fastened to the lower support bracket 55 with bolts or the like.
Here, since a grounding resistance acts on each front wheel 2, when the handle 24 is operated clockwise or counterclockwise, an input shaft 83 mechanically coupled to the handle 24 and each front wheel 2 are mechanically connected. A relative rotational force is generated between the output shaft 84 and the connected output shaft 84.

  At this time, the torsion bar 92 interposed between the shafts 83 and 84 is twisted, and the rotational torque applied to the steering shaft 25, that is, the steering torque of the handle 24 is detected based on the twist, and the detected value is determined according to the detected value. When the received signal is input to the control unit 93, the power assist motor 82 is driven and controlled based on the signal.

  As a result, when the handle 24 is rotated, the steering mechanism including the steering shaft 25 (output shaft 84) receives the rotational operation force from the handle 24 and the auxiliary rotational force from the power assist motor 82. Therefore, the handle operating force is reduced.

  Referring to FIG. 3 together, the output shaft 84 of the actuator unit 81 and the left and right front wheels 2 are connected via left and right tie rods 75, and the inner ends of these tie rods 75 are engaged. The pitman arm 84a is attached to the output shaft 84 by spline fitting.

  The pitman arm 84a is located immediately below the lower support bracket 55, and the pitman arm 84a and the shaft holder 55a fixed to the lower support bracket 55 are used to rotate the handle 24 (steering shaft 25) clockwise or counterclockwise. A handle stopper that defines the maximum steering position is configured.

  That is, a stopper main body 55b protrudes from the lower side of the shaft holder 55a, and left and right contact portions 84b protrude from both sides of the pitman arm 84a, so that the steering wheel 24 is in a state where the steering angle is 0 degree ( When the vehicle is rotated clockwise or counterclockwise until it reaches a predetermined angle (θ1 in FIG. 3), either the left or right contact portion 84b contacts the side portion of the stopper main body 55b. A maximum turning state in which the rotation of the handle 24 is restricted is obtained. For example, on both sides of the stopper main body 55b, a maximum turning switch (maximum turning detection means) 101 for detecting the maximum rightward or leftward turning of the handle 24 (steering shaft 25) is provided.

  Here, another form of the handle stopper will be described with reference to FIGS. 2 and 9. On the front upper side of the vehicle body frame 4, left and right top pipes 53 having a substantially square shape in side view are provided. An upper support bracket 54 is provided between the tops of the top pipes 53 (which is also the uppermost part of the vehicle body frame 4), and a cross pipe 52 is provided immediately behind the upper support bracket 54. A bar-shaped stopper main body 155b is fixed in a standing state at the upper center of the cross pipe 52, and a bar 184a whose intermediate portion is bent along its outer periphery is welded to the steering shaft 25 immediately ahead. Fixed.

  Both side portions of the bar 184a constitute left and right abutting portions 184b, and when the handle 24 is rotated from the steering angle of 0 degree clockwise or counterclockwise until it reaches a predetermined angle (θ2 in FIG. 9). The left and right abutting portions 184b abut on the side portions of the stopper main body 155b, thereby achieving a maximum turning state in which further rotation of the handle 24 is restricted. Also in the handle stopper having such a configuration, for example, the maximum steering switch 101 is provided on both sides of the stopper main body 155b.

  FIG. 4 is a block diagram showing the main part of the steering assist force control apparatus in the first embodiment. As shown in this figure, the control unit 93 has a maximum provided in the stopper main body 55b (or the stopper main body 155b). A maximum turning detection signal from the turning switch 101 is input, and the turning angle of the steering shaft 25 is detected based on the maximum turning detection signal, the voltage value and the current value to the power assist motor 82, and the turning. The steering assist force to the steering shaft 25 is controlled in consideration of the steering angle.

  Specifically, the control unit 93 includes a turning angle calculation unit (steering angle calculation means) 93d that calculates a relative turning angle (a turning angle from an arbitrary position) of the steering shaft 25, and a maximum turning switch 101. Knowing from the reference position estimation unit (reference position calculation means) 93e for estimating the steering reference position (steering reference state with respect to the vehicle body) of the steering shaft 25 based on the detection signal from the steering shaft 25, the relative steering angle and the steering reference position A steering force control unit 93f that changes the steering assist force based on the absolute turning angle of the steering shaft 25 to be obtained (relative turning angle from the turning reference position).

  One process performed in the control unit 93 will be described with reference to the flowchart of FIG. 5. First, it is determined whether or not the ignition 102 is ON (whether or not the engine is started) ( If it is determined in step S1) that the ignition is on (YES), the turning angle calculation unit 93d calculates the relative turning angle of the steering shaft 25 (step S2), and the reference position estimation unit 93e. Estimates the turning reference position (step S3), and the steering force control unit 93f changes the steering assist force to the steering shaft 25 based on the relative turning angle and the absolute turning angle that can be known from the turning reference position. Control is performed to do this (step S4).

  That is, the power assist motor 82 that generates the steering assist force is driven and controlled in consideration of not only the steering torque detection signal from the torque sensor 91 but also the absolute turning angle of the steering shaft 25, for example, the steering shaft. When the handle 24 is turned from a position where the absolute turning angle of the steering wheel 25 (the handle 24) is 0 degree (straight vehicle traveling position), and when the handle 24 is returned to the position where the absolute turning angle is 0 degree, the power assist motor 82 Fine control such as changing the output torque (steering assisting force) can be performed, so that it is possible to improve the steering performance and the ratio design freedom of the steering mechanism.

  Here, the process when the turning angle calculation unit 93d calculates the relative turning angle of the steering shaft 25 in step S2 will be described with reference to the flowchart of FIG. First, the turning angle calculation unit 93d detects the current and voltage of the power assist motor 82 (step 21), calculates the rotational speed (motor rotational speed) of the power assist motor 82 based on the detected value, and this motor. The turning speed of the steering shaft 25 is calculated by adding the reduction ratio of the actuator unit 81 to the rotation speed (step S22). Thereafter, the turning angle calculation unit 93d calculates the relative turning angle of the steering shaft 25 by integrating the turning speed (step S23).

  Next, processing when the reference position estimation unit 93e estimates the steering reference position of the steering shaft 25 in step S3 will be described with reference to the flowchart of FIG. First, the reference position estimation unit 93e determines whether any of the maximum turning switches 101 is turned on (whether maximum turning is detected) (step S31), and determines which maximum turning. If it is determined that the rudder switch 101 is turned on (maximum steering is detected) (YES), the absolute steering angle at the time of maximum steering of the steering shaft 25 that is set to a predetermined angle can be known. Thus, the position at which the absolute turning angle of the steering shaft 25 becomes 0 degrees is back-calculated and estimated as the turning reference position (step S32).

  Note that the steering reference position is not estimated by the reference position estimation unit 93e immediately after the ignition is turned on. In such a case, the steering force control unit 93f performs control that does not include the turning angle until the turning reference position is estimated. When the turning reference position is not estimated, the steering force control unit 93 f can use a predetermined initial value read from the memory of the control unit 93. Specifically, for example, this is used by fixing or assuming the absolute turning angle of the steering shaft 25 when the ignition is OFF, or by storing the absolute turning angle of the steering shaft 25 immediately before the ignition is OFF. It can also be used.

  Here, in step S4, when the steering force control unit 93f changes the output torque of the power assist motor 82 based on the absolute turning angle of the steering shaft 25, the power assist motor 82 based on the detection signal of the torque sensor 91 is used. The target value of the output torque is multiplied by a predetermined ratio that changes according to the absolute turning angle.

  Specifically, as shown in FIG. 8, when the absolute turning angle of the steering shaft 25 is relatively small, a state in which the target value of the output torque of the power assist motor 82 is multiplied by a ratio of 100% is substantially constant. While maintaining a good steering feel in the practical steering range, when the absolute turning angle becomes relatively large, the ratio is reduced to less than 100% on the contrary, By multiplying the ratio by the target value to reduce the output torque of the power assist motor 82, the steering restoring force due to the road surface reaction force is emphasized.

  Furthermore, the ratio (steering ratio) between the absolute turning angle of the handle 24 and the absolute turning angle of the front wheels 2 changes according to the absolute turning angle of the handle 24 due to restrictions on the vehicle body layout. There is a difference in steering load (handle steering force) between when the handle 24 is at an angle corresponding to the neutral position and at an angle corresponding to the maximum steered position. In the power steering system 80, by controlling the steering assist force in accordance with the absolute turning angle, it is possible to increase or decrease the steering load difference, and an optimal steering feeling can be set. Further, since the steering load change due to the steering ratio change can be adjusted by the assist control of the power steering system 80, the allowable range of the steering ratio change is widened, and as a result, the degree of freedom of design around the steering is widened.

  As described above, the electric power steering apparatus in the above-described embodiment applies the steering assist force to the steering mechanism using the power assist motor 82 as a drive source, and rotates the motor based on the voltage and current of the power assist motor 82. A steering angle calculation unit 93d that detects the speed and integrates the motor rotation speed (steering speed) to calculate the relative steering angle of the steering shaft 25, and the steering shaft 25 based on the operation of the steering shaft 25. A reference position estimation unit 93e that estimates a turning reference position and a maximum turning switch 101 that detects the maximum turning of the steering shaft 25 are provided, and the maximum turning switch 101 detects the maximum turning of the steering shaft 25. Sometimes, the reference position estimator 93e makes the absolute rotation of the steering shaft 25. And estimates the position where the angle is 0 degrees as a steering reference position.

According to this configuration, it is possible to know the relative turning angle of the steering shaft 25 and its turning reference position, thereby detecting the relative turning angle from the turning reference position, that is, the absolute turning angle of the steering shaft 25. It becomes possible.
As a result, it is possible to control the steering assist force with a fine steering angle in consideration of the steering angle of the steering shaft 25, and it is possible to reduce the cost and weight by eliminating the need for a dedicated steering angle sensor and its countermeasure against failure. Furthermore, since the steering load change due to the relationship between the steered position and the steering ratio can be adjusted by the assist control of the power steering system 80, the steering ratio at each steered position can be set without considering the steering load change. The design freedom around the steering can be expanded.

Next, a second embodiment of the present invention will be described.
This embodiment differs from the first embodiment in the configuration of the steering assist force control device and the processing for estimating the steering reference position of the steering shaft 25, and is the same as the first embodiment. The same reference numerals are given to the parts and the description thereof is omitted.

  FIG. 10 is a configuration diagram showing the main part of the steering assist force control apparatus in this embodiment. As shown in this figure, in the control unit 193 instead of the control unit 93, the cumulative value of the relative turning angle is shown. Based on this, the steering angle of the steering shaft 25 is detected, and the steering assist force to the steering shaft 25 is controlled in consideration of the steering angle.

  Specifically, the control unit 193 accumulates the turning angle calculation unit 93d that calculates the relative turning angle of the steering shaft 25, and the calculated value of the turning angle calculation unit 93d to change the relative turning angle. A turning angle accumulation unit 93g for detecting the width, and a reference position estimation unit (reference position calculation means for estimating the turning reference position of the steering shaft 25 when the detected value of the turning angle accumulation unit 93g reaches a predetermined value. 193e and a steering force control unit 93f that changes the steering assist force based on the absolute turning angle of the steering shaft 25 that can be known from the relative turning angle and the turning reference position.

  In such a control unit 193 as well, the process shown in the flowchart of FIG. 5 is performed, so that the control of changing the steering assist force based on the absolute turning angle of the steering shaft 25 is performed. The content of the process at the time of estimating the steering reference position of the shaft 25 is different from that of the first embodiment.

  That is, as shown in the flowchart of FIG. 11, first, the relative turning angle of the steering shaft 25 is accumulated (step S131), and the accumulated value (the amount of change of the relative turning angle from the clockwise end to the counterclockwise end). It is determined whether or not (equivalent) has reached a predetermined value (step S132). Here, the predetermined value is a value corresponding to a change amount between left and right maximum turnings in the steering shaft 25, and more specifically, a value slightly smaller than a change amount between the maximum turnings.

  Here, when it is determined that the accumulated value has reached the predetermined value (YES), a position that is the center of the accumulated value (a position at which the absolute turning angle is 0 degree) is set as a turning reference position. Estimate (step S133). Note that the reason why the predetermined value is slightly smaller than the amount of change between the maximum turnings is that the steering reference position can be estimated before the steering shaft 25 fully turns to the left and right, thereby improving the detection sensitivity. It is for improving.

  As described above, the electric power steering apparatus according to the above embodiment includes the turning angle calculation unit 93d that calculates the relative turning angle of the steering shaft 25 and the turning angle accumulation that detects the change width of the relative turning angle. 93g, and a reference position estimation unit 193e for estimating the steering reference position of the steering shaft 25 based on the operation of the steering shaft 25, and the change width of the relative turning angle of the steering shaft 25 has reached a predetermined value. Sometimes, the reference position estimation unit 193e estimates the steering reference position of the steering shaft 25.

According to this configuration, when the change width of the relative turning angle of the steering shaft 25 reaches a predetermined value, it is possible to know the absolute turning angles at the clockwise and counterclockwise ends of the changing width of the steering shaft 25. Therefore, the steering reference position of the steering shaft 25 can be estimated based on this, and the absolute turning angle of the steering shaft 25 can be detected.
As a result, even when the maximum steering switch 101 is not provided as in the first embodiment, it is possible to finely control the steering assist force in consideration of the steering angle of the steering shaft 25. The cost and weight can be reduced by eliminating the steering angle sensor and its failure countermeasure.

Next, a third embodiment of the present invention will be described.
In this embodiment, the configuration of the steering assist force control device and the processing for estimating the steering reference position of the steering shaft 25 are different from those in the above embodiments. The same reference numerals are given and description thereof is omitted.

  FIG. 12 is a block diagram showing the main part of the steering assist force control apparatus in this embodiment. As shown in this figure, a control unit 293 that replaces the control units 93 and 193 includes a saddle-ride type four-wheel vehicle 1. A detection signal from a vehicle speed sensor (vehicle speed detection means) 103 for detecting the vehicle speed of the vehicle is input, and the turning angle of the steering shaft 25 is detected based on the vehicle speed detection signal and the steering torque detection signal from the torque sensor 91, The steering assist force to the steering shaft 25 is controlled in consideration of the turning angle.

  Specifically, the control unit 93 linearly moves the saddle-ride type four-wheel vehicle 1 based on the detected values of the turning angle calculation unit 93d that calculates the relative turning angle of the steering shaft 25, the vehicle speed sensor 103, and the torque sensor 91. A straight traveling state detection unit 93h that detects the state, and a reference position estimation unit that estimates a turning reference position of the steering shaft 25 when the straight traveling state detection unit 93h detects the straight traveling state of the saddle-ride type four-wheel vehicle 1 (reference Position calculation means) 293e and a steering force control unit 93f that changes the steering assist force based on the absolute turning angle of the steering shaft 25 that can be known from the relative turning angle and the turning reference position.

  In such a control unit 93 as well, the process shown in the flowchart of FIG. 5 is performed, so that the control of changing the steering assist force based on the absolute turning angle of the steering shaft 25 is performed. The content of the process at the time of estimating the steering reference position of the shaft 25 is different from those of the above embodiments.

  That is, as shown in the flowchart of FIG. 13, first, the timer in the control unit 93 is reset (step S231), and after detecting the vehicle speed and the steering torque (step S232), the steering torque is below a predetermined value. Is determined (step S233). Here, when it is determined that the steering torque is equal to or lower than the predetermined value (YES), it is next determined whether or not the vehicle speed is equal to or higher than the predetermined value (step S234). Here, when it is determined that the vehicle speed is equal to or higher than the predetermined value (YES), it is next determined whether or not a predetermined time has elapsed since the timer was reset (step S235).

  Here, when it is determined that the predetermined time has elapsed (when the steering torque is equal to or lower than the predetermined value and the vehicle speed is equal to or higher than the predetermined value continues for the predetermined time), the saddle-ride type four-wheel vehicle 1 moves straight ahead. The position of the steering shaft 25 in the straight traveling state (position where the absolute turning angle is 0 degree) obtained by, for example, averaging the relative turning angles within the predetermined time is determined as the turning reference position (Step S236). When it is determined in step S235 that the predetermined time has not elapsed (NO), the processing from step S232 is repeated until the predetermined time has elapsed. If it is determined in steps S233 and S234 that the steering torque exceeds a predetermined value (NO), or if the vehicle speed is determined to be lower than the predetermined value (NO), the process starts from step S231. The process starts again.

  As described above, the electric power steering apparatus according to the above embodiment includes the turning angle calculation unit 93d for calculating the relative turning angle of the steering shaft 25 and the turning of the steering shaft 25 based on the operation of the steering shaft 25. A reference position estimation unit 293e that estimates a reference position, a torque sensor 91 that detects a steering torque, and a vehicle speed sensor 103 that detects a vehicle speed. The detected value of the torque sensor 91 is equal to or less than a predetermined value and the vehicle speed sensor 103 The reference position estimation unit 293e estimates the steering reference position of the steering shaft 25 when the detected value is equal to or greater than the predetermined value for a predetermined time.

According to this configuration, it is possible to estimate that the absolute turning angle of the steering shaft 25 is kept constant (0 degrees) when the steering torque is equal to or lower than the predetermined value and the vehicle speed is equal to or higher than the predetermined value for a predetermined time. Therefore, based on this, it is possible to estimate the steering reference position of the steering shaft 25 and to detect the absolute steering angle of the steering shaft 25.
As in the above-described embodiments, this makes it possible to control the steering assist force with a fine steering angle in consideration of the steering angle of the steering shaft 25, and eliminates the need for a dedicated rudder angle sensor and its failure countermeasures. Reduction can be achieved.

  In addition, the structure in each said Example is an example of this invention, and it cannot be overemphasized that a various change is possible in the range which does not deviate from the summary of this invention.

1 is a side view of a saddle-ride type four-wheel vehicle according to an embodiment of the present invention. It is a side view of the vehicle body front part of the saddle-ride type four-wheel vehicle. It is AA sectional drawing in FIG. It is a block diagram of the steering assistance force control apparatus of the said saddle-ride type four-wheel vehicle. It is a flowchart which shows the process of the said steering assist force control apparatus. It is a flowchart which shows the process at the time of calculating the relative turning angle in the flowchart of FIG. It is a flowchart which shows the process at the time of estimating the steering reference position in the flowchart of FIG. It is the graph which provided the ratio which multiplies the target value of the output torque of a power assist motor on a vertical axis | shaft, and provided the turning angle on the horizontal axis. FIG. 4 is a view taken in the direction of arrow B in FIG. 2 and is an explanatory view showing another form of the handle stopper. It is a block diagram of the steering assist force control apparatus in 2nd Example of this invention. It is a flowchart equivalent to FIG. 7 in a 2nd Example. It is a block diagram of the steering assistance force control apparatus in 3rd Example of this invention. FIG. 8 is a flowchart corresponding to FIG. 7 in the third embodiment.

Explanation of symbols

25 Steering shaft 80 Power steering system (electric power steering device)
82 Power Assist Motor (Assist Motor)
91 Torque sensor (torque detection means)
93d Steering angle calculation unit (steering angle calculation means)
93e, 193e, 293e Reference position estimation unit (reference position estimation means)
101 Maximum steering switch (maximum steering detection means)
103 Vehicle speed sensor (vehicle speed detection means)

Claims (2)

In the electric power steering device (80) that applies steering assist force to the steering mechanism using the assist motor (82) as a drive source,
A turning angle calculation means (93d) for detecting a motor rotation speed based on the voltage and current of the assist motor (82) and calculating a relative turning angle of the steering shaft (25) based on the motor rotation speed; wherein the steering shaft (25) a reference position estimating means for estimating the steering reference position based on the operation of (93e), maximum steering detecting means for detecting a maximum steering of the steering shaft (25) and (101) equipped with a,
The steering reference position is a position where the absolute steering angle of the steering shaft (25) is 0 degree,
When the maximum turning detection means (101) detects the maximum turning of the steering shaft (25), the reference position estimation means (93e) estimates the turning reference position of the steering shaft (25). Electric power steering device. In the electric power steering device (80) that applies steering assist force to the steering mechanism using the assist motor (82) as a drive source,
A turning angle calculation means (93d) for detecting a motor rotation speed based on the voltage and current of the assist motor (82) and calculating a relative turning angle of the steering shaft (25) based on the motor rotation speed; Reference position estimating means (193e) for estimating the turning reference position based on the operation of the steering shaft (25),
The steering reference position is a position where the absolute steering angle of the steering shaft (25) is 0 degree,
When the change width of the relative turning angle of the steering shaft (25) reaches a predetermined value, the reference position estimating means (193e) estimates the turning reference position of the steering shaft (25). Electric power steering device.

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