JP2581303B2 - Steering angle detection arithmetic unit for four-wheel drive vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering angle detection and calculation device for a four-wheel drive vehicle used for accurately performing turning control and the like of a vehicle.

<Conventional technology> A vehicle traveling on a circuit has a centrifugal force, that is, a lateral acceleration (hereinafter, referred to as a lateral acceleration) corresponding to the traveling speed in a direction perpendicular to the traveling direction.
We call it horizontal G. ) Occurs.

For this reason, if the traveling speed with respect to the radius of curvature of the circuit is too high, the wheels may skid and the vehicle may not operate as desired. Therefore, immediately before the circuit, the driver once lowers the running speed and performs so-called slow-in first-out running in which the vehicle accelerates slowly. However, there is a case where the radius of curvature is gradually reduced in a circuit such as a blind curve in which an exit cannot be confirmed. In such a case, an advanced driving technique is required.

On the other hand, there is a vehicle having an under-steering tendency in which the traveling radius increases while the steering angle is constant when the vehicle is accelerated from a steady circular turning state. In such a vehicle, it is necessary to gradually increase the steering angle with an increase in the lateral G. However, when the lateral G exceeds a certain value (limit value) inherent to the vehicle, the tendency of understeering sharply increases, and steering becomes difficult. It is known that A typical example of such a vehicle is a so-called FF vehicle having a front engine and a front drive in which the steered wheels and the drive wheels are the same, but this tendency is also observed in a four-wheel drive vehicle that drives all wheels. Can be seen.

In order to prevent the lateral G from exceeding the limit value, it is fundamental that the driver knows the radius of curvature of the circuit and adjusts the driving force with the accelerator pedal. However, it is difficult for an inexperienced driver to delicately control the depression amount of the accelerator pedal by using the above-described blind curve or the like.

In view of such circumstances, various driving force control devices have been proposed that automatically reduce the driving force before the vehicle becomes difficult to turn. Many of these devices reduce the output of the engine in accordance with, for example, the amount of rolling of the vehicle body without being linked to the amount of depression of the accelerator pedal. In other words, rolling caused by the lateral G always occurs during turning, but the smaller the turning radius and the higher the traveling speed, the larger the amount of rolling. Therefore, the turning amount is increased by height sensors provided on the left and right sides of the vehicle body. To reduce the output. In addition, there is a method of detecting the yaw amount, which is a swing phenomenon of the vehicle body, to reduce the output.

<Problem to be Solved by the Invention> In the driving force control device as described above, after rolling or the like actually occurs, output control of the engine is performed based on the rolling amount. However, such a control device has the following disadvantages. That is, in a situation where the rolling is rapidly increasing, a so-called hunting operation is repeated in which the output control is delayed, or the output is further controlled by releasing the control after the rolling is stopped and the rolling is generated again. Cause it.

Therefore, ECU (Electronic Control) is performed based on driving force control based on running speed, steering angle, etc. and stability factor (eigenvalue obtained from suspension, tire rigidity, etc.).
Unit), the control unit is in the limelight. In this driving force control device, since the data at the moment when the driver turns the steering wheel is input to the ECU, the engine output control (so-called anticipation control) can be performed before excessive rolling or the like occurs. The steering angle which is indispensable for this control is usually based on the steering shaft stored in a random access memory (RAM), that is, the neutral position of the front wheels, and the amount of deviation from the neutral position is determined by a slit plate attached to the steering shaft. It is detected by a steering angle sensor using a phototransistor or the like and input to the ECU.

However, as is well known, the steering amount for fully steering the steering wheel, that is, the lock-to-lock rotation speed is several rotations (generally 2.5 to 3 rotations). Therefore, even if a slit or the like at the neutral point is formed in the slit plate of the steering angle sensor, the neutral position is normal if the battery or the wiring or the like is removed (for example, during maintenance). In one rotation from the state described above. The neutral position of the steering shaft itself and the neutral position of the front wheels naturally change when gears in the steering device are worn or when the toe-in adjustment is performed during maintenance. Therefore, the turning angle of the steering wheel and the actual steering angle sometimes differ on a small order.

When driving the vehicle in such a state, when the output control should be performed, this may not be performed, or conversely, the output may be reduced simply by turning the steering wheel lightly, and the driver may not be able to drive as intended Had occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a steering angle detecting device capable of learning and correcting the neutral position of a steering shaft by itself while traveling and supplying accurate steering angle data to an ECU.

<Means for Solving the Problems> In order to solve this problem, the present invention provides a rotating member that rotates integrally with a steering shaft, and a rotating member that is fixed to a steering column and detects an angular displacement of the rotating member. Steering angle detection means comprising an angle detector, traveling speed detection means for detecting the traveling speed of the vehicle, rotation difference detection means for detecting the difference between the rotational speed of each of the front, rear, left and right wheels and their average value, After the start of traveling, the vehicle travels for a predetermined time in a state where the traveling speed information obtained from the traveling speed detecting means is equal to or more than a predetermined value, and each rotation difference information obtained from the rotation difference detecting means is equal to or less than a predetermined value. Under the condition, the first learning is performed with the position of the rotating member detected by the rotation angle detector of the steering angle detecting means as a neutral position, and the angular displacement of the rotating member from this neutral position is used as the steering angle. On the other hand, in learning the neutral position from the second time onward under the above conditions, a steering angle calculation position is provided such that only a predetermined amount of angle increase or decrease is performed with respect to the neutral position of the rotating member obtained by the first learning. The present invention proposes a steering angle detection and calculation device for a four-wheel drive vehicle.

<Operation> Even if the neutral position information in the RAM is lost or erased due to a stop or maintenance, if the vehicle travels straight ahead at a predetermined speed for a predetermined time, the rotation angle of the rotating member, that is, the steering shaft at that point becomes neutral. Stored in RAM as a location,
Thereafter, the steering angle of the vehicle is calculated from the angular displacement of the rotating member from the neutral position.

<Embodiment> An embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 schematically shows a configuration of a driving force control device employing one embodiment of a steering angle detection arithmetic device according to the present invention, FIG. 2 shows an enlarged perspective view of a steering angle sensor, and FIG. 9 shows a control flowchart of the neutral position learning in the embodiment.

As shown in FIG. 1, the vehicle of the present embodiment is a four-wheel drive passenger vehicle having an engine 2 and a transmission 3 mounted on a front portion of a vehicle body 1 and driving front and rear left and right wheels 4, 5, 35, and 36. .

The output control of the engine 2 in this passenger car is normally performed as follows.

By adjusting the depression amount of the accelerator pedal 6, a throttle valve (not shown) in the throttle body 8 opens and closes via the accelerator cable 7. Since the throttle body 8 is provided between the intake duct 10 connected to the air cleaner box 9 and the intake manifold 11, the amount of air sucked under negative pressure into the combustion chamber (not shown) of the engine 1 increases or decreases. At this time, the opening of the throttle valve is detected by a throttle position sensor 12 attached to the throttle body 8,
It is input to the ECU 13 as throttle opening information.

In addition to the throttle opening information, information such as the atmospheric pressure, the intake air temperature, and the cooling water temperature is input to the ECU 13, and the fuel injection amount is set to improve the engine output and reduce the amount of toxic components in the exhaust gas. Then, the injector 14 is driven (fuel injection). Note that the engine 2 of this embodiment employs multipoint injection, and the injection amount is controlled for each cylinder. The air that has been injected into the air-fuel mixture
A piston (not shown) is ignited by an ignition unit (not shown) near a compression top dead center, and burns and expands.
Generate output. At this time, the ECU 13 determines the ignition timing and the energizing time based on information such as the crank angle and the knocking in addition to the information on the intake air, and controls the drive of the ignition unit.

The output of the engine 2 is transmitted to the wheels 4, 5, 35, and 36 by drive shafts 15, 16, 39, and 40 via the transmission 3, and the wheels are driven to rotate. As a result, a driving force is generated between the vehicle and the road surface, and the vehicle body 1 moves forward or backward, and the vehicle travels based on the driver's will.

The throttle valve of this embodiment is controlled by the ECU 13 in addition to the opening and closing control by the accelerator pedal 6 described above. This is driven in the closing direction from the original position by a vacuum motor 17 integrated with the throttle body 8. The vacuum motor 17 has an EC
Magnet valve 18 driven by duty ratio by U13
, A negative pressure is supplied from a negative pressure source in the vacuum tank 19. In the figure, reference numeral 20 denotes a vacuum hose connecting the intake manifold 11 and the vacuum tank 19.

The control of closing the throttle valve by the vacuum motor 17 in the vehicle of the present embodiment is used as a means for reducing the driving force during turning. Vehicle speed V, steering wheel 21
From the steering angle δ and the stability factor A
The ECU 13 calculates the optimum throttle opening and drives the magnetle valve 18 with an appropriate duty ratio so as to achieve the opening. Then, the vacuum motor 17 drives the throttle valve in the closing direction, so that the understeer can be suppressed by reducing the engine output, that is, the driving force.

The traveling speed V is detected by a reed switch type vehicle speed sensor (not shown), which is a traveling speed detecting means built in the speedometer 22, and is directly input to the ECU 13. Also,
The steering angle δ of the steering wheel 21 is detected by a steering angle detection unit 24 which is a steering angle detection means provided above the steering column 23. As shown in FIG. 2, the steering angle detection unit 24 includes a slit plate 25 and a steering angle sensor 26 serving as a rotation angle detector. The slit plate 25 rotates integrally with the steering shaft 27, and has a number of slits 25a formed on the outer periphery thereof. The steering angle sensor 26 is fixed to the steering column 23, and two photointerrupters 28 and 29 are mounted on the upper part thereof so as to sandwich the slit plate 25 therebetween.

The resolution of the steering angle detection unit 24 is in units of 5 °, and the rotation direction (clockwise or counterclockwise) of the steering can be detected. The information of the detected steering angle δ is stored in the TCL (Traction Calculate Uni
t) Entered in 30.

The TCL 30 is a device that calculates a target drive torque T _O that does not cause excessive rolling or the like during turning, and sends the information to the ECU 13. The ECU 13 is connected to the ECU 13 by a signal cable 31, so that information can be exchanged with each other. TCL3
To calculate the target driving torque T _O is the 0, other information of the steering angle [delta], the information of the accelerator opening theta _A from the accelerator sensor 32 attached to the throttle body 8 is inputted.
Further, information on the wheel speeds V _FL and V _FR of the left and right front wheels 4 and 5 is obtained from the wheel speed sensors 33 and 34, and information on the wheel speeds V _RL and V _RR of the right and left rear wheels 35 and 36 is obtained from the wheel speed sensors 37 and 38. , Respectively.

Hereinafter, the procedure for detecting the steering angle center in the present embodiment will be described with reference to the control flowchart of FIG. In addition, the symbol (S
1, S2 ...) correspond to the symbols described at the end of the paragraph of the description.

When the engine 2 starts and the vehicle body 1 starts running, the third
The learning control shown in the figure is started. The learning control interval may be performed every one rotation of the crank, or may be performed every few rotations.

After start of control, it calculates a the TCL30 first running speed V _B.
In this embodiment, as the running speed V _B, the front and rear left and right wheels 4,
Of the wheel speeds V _FL , V _FR , V _RF , V _RR of 5, 35, 36, the second value from the bottom is used. ... S1 At this time, the value detected by the vehicle speed sensor in the speedometer 22 described above may be used as it is, or an error may be determined by comparing the detected value with the above calculated value.

When the obtained running speed V _B, the TCL30, then the wheel speeds V
An average value of _FL , V _FR , V _RF , V _RR , that is, a four-wheel average value VAV 4 is calculated. … S2 Once the four-wheel average value VAV4 is obtained, the TCL 30 then calculates the difference between this and each wheel speed V _FL , V _FR , V _RF , V _RR , ie, the wheel speed difference ΔV
_FL , ΔV _FR , ΔV _RF , ΔV _RR are calculated by the following equations.

_{ΔV FL = | V FL -VAV4 |} ΔV FR = | V FR -VAV4 | ΔV RF = | V RF -VAV4 | ΔV RR = | V RR -VAV4 | ... S3 Then, the traveling speed V _B is given the TCL30 Value (hereinafter, referred to as a judgment value _VA . In the present embodiment, this is set to 10 km / H).
It is determined whether it is greater than. This is because a difference in wheel speed due to steering is unlikely to occur unless the traveling speed becomes high to some extent, and is appropriately set based on the traveling characteristics of the vehicle, experiments, and the like. In the case of V _B <V _A In this step, TCL30 proceeds to step S13 described later. … S4 If V _B ≧ V _A , the TCL 30 then calculates each wheel speed difference ΔV _FL ,
ΔV _FR, ΔV _RF, ΔV _RR predetermined value (hereinafter, referred to as determination value V _C. In this embodiment a 1km / H it.) Determines smaller or not. Here, the determination value V _C to 0 km / H, i.e. not a state the wheel speed difference is not, the dynamic load radius of the tire or the like is changed by the magnitude of the air pressure, the left and right wheels of the front and rear despite a straight state 4,5,35,36 wheel speeds V _FL , V _FR ,
This is because _VRF and _VRR may be different from each other. Also in these steps, each wheel speed difference ΔV _FL , ΔV _FR , ΔV _RF , Δ
The value of V _RR is equal to or larger than the determination value V _C, TCL30 proceeds to step S13. If it is _{... S5~S8 ΔV FL ~ΔV RR <V} C, TCL30 determines that the vehicle body 1 is running straight, counts up from the following formula built value t of the learning timer.

t = t + Δt S9 Here, Δt is a minute time required for the learning control.

State Next, the value t is given the value of the learning timer in TCL30 (hereinafter, referred to as the determination value t _D. In this embodiment does this 0.5 second.) Or not greater than, that described above a predetermined time It is determined whether or not the vehicle has run. … S10 This determination is, of course, at the beginning of traveling, t
<A t _D, but repeating the above calculation and determination (S1 to S10) to return to the start position of the flowchart in that case.

When it is determined that 0.5 seconds have elapsed from the start of the learning timer count, the TCL 30 sets the steering angle neutral position learned flag F _C
Is set, that is, whether this learning control is the first time. … S11 S11, the steering angle neutral position learned flag F
If it is determined that _C is not set, the TCL 30 regards the current steering shaft turning position δm (n) as the neutral position δM (n) of the steering shaft 27, reads this into an internal memory, and simultaneously reads the steering angle neutral position. to set the learned flag F _C. … S12 Thus, the neutral position δ of the steering shaft 27
After M (n) is set, the turning angle δ of the steering shaft 27 is determined based on the neutral position δM (n).
Calculate _S.

Next, the TCL 30 clears the count of the learning timer, returns to the start position, and starts the steering angle neutral position learning again. … S13 The steering angle neutral position learned flag F _C in step S11
Is set, that is, when it is determined that the steering angle neutral position learning has been performed for the second time or later, the TCL 30 sets the current steering shaft turning position δm (n) to the previous neutral position δm (n).
It is determined whether it is equal to M (n-1). And δm
If (n) = δM (n-1), step S13
Move to S14 If it is determined in step S14 that the current steering shaft turning position δm (n) is not equal to the previous neutral position δM (n-1) due to play in the steering system or the like, the TCL 30 determines First, it is determined whether or not a value obtained by subtracting the previous neutral position δM (n−1) from the current steering shaft turning position δm (n) is smaller than −Δδ. Δδ is a correction amount, and is set to 5 ° or less because the resolution of the steering angle sensor 26 is 5 ° as described above. ... S15 In step S15, δm (n) −δM (n−1) <
If −Δδ, the TCL 30 is set to the new neutral position δM (n)
ΔM (n−1) −Δδ. By doing this,
Even if an abnormal detection signal is output from the steering angle sensor 26 for some reason, the neutral position δM (n) is not rapidly updated. Then, when the update of the neutral position δM (n) is completed, the process proceeds to step S13. ... S16 In step S15, δm (n) −δM (n−1) ≧
-Δδ, the TCL 30 then moves from the current steering shaft turning position δm (n) to the previous neutral position δM (n
It is determined whether the value obtained by subtracting -1) is larger than Δδ. ... S17 In step S17, δm (n) −δM (n−1)>
If Δδ, the TCL 30 sets the new neutral position δM (n) to δM (n−1) + Δδ. Again, step 16
Similarly to the above, abrupt renewal of the neutral position δM (n) is not performed. Also in this case, when the update of the neutral position δM (n) is completed, the process proceeds to step S13. ... S18 In step S15, δm (n) −δM (n−1) ≦
In the case of Δδ, since the absolute value of the value obtained by subtracting δM (n−1) from δm (n) is smaller than Δδ, the current steering shaft turning position δm (n) is set to the new neutral position δM ( n). Also in this step, the neutral position δM
Upon completion of the update in (n), the flow shifts to step S13.
… S19 The description of the specific embodiment of the present invention is completed above, but the embodiment of the present invention is not limited to this embodiment. For example, in the above embodiment, the ECU and the TCL are used as the control device. The ignition timing may be retarded, the compression ratio may be reduced, or the like, as a driving force control method. Further, although the above embodiment is directed to a driving force control device taking into account turning, the present invention may be applied to a steering angle calculation in a four-wheel steering device or the like.

<Effects of the Invention> According to the steering angle detection / calculation device for a four-wheel drive vehicle according to the present invention, the neutral position of the steering angle is learned from the traveling speed, the rotation difference of each wheel, and the traveling time. Even if there is a deviation between the steering angle and the actual steering angle due to aging, it is automatically corrected. As a result, driving force control and the like can be performed with high accuracy, and steering stability is improved. Further, since the learning correction amount for the second and subsequent times is suppressed to a predetermined value, the neutral position is not rapidly updated, and the stability can be maintained at a high level.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a driving force control device employing an embodiment of a steering angle detection calculation device according to the present invention. FIG. 2 is an enlarged perspective view showing a steering angle sensor. FIG. 7 is a control flowchart of the neutral position learning in this embodiment. In the drawing, 1 is a vehicle body, 2 is an engine, 3 is a transmission, 4, 5 is a front wheel, 8 is a throttle body, 13 is an ECU, 21 is a steering wheel, 23 is a steering column, 24 is a steering angle detection unit, and 28 is a slit plate. Reference numeral 26 denotes a steering angle sensor, 27 denotes a steering shaft, 30 denotes a TCL, 31 denotes a signal cable, 33 and 34 denote wheel speed sensors, 35 and 36 denote rear wheels, and 37 and 38 denote wheel speed sensors.

Claims (1)

(57) [Claims] 1. A steering member comprising: a rotating member rotating integrally with a steering shaft; a rotation angle detector fixed to a steering column for detecting an angular displacement of the rotating member; Traveling speed detecting means for detecting, rotational difference detecting means for detecting a difference between the rotational speed of each of the front, rear, left and right wheels and their average value, and traveling speed information obtained from the traveling speed detecting means after traveling starts. Under the condition that each rotation difference information obtained from the rotation difference detection means is equal to or less than a predetermined value and the vehicle travels for a predetermined time, the rotation detected by the rotation angle detector of the steering angle detection means. The first learning is performed with the position of the member as the neutral position, and the angular displacement of the rotating member from this neutral position is used as the steering angle, while the learning of the neutral position from the second time onward under the above conditions is performed as described above. Times a predetermined amount of angle increase and decrease the steering angle calculating means which is adapted only performed, the four-wheel drive vehicle, characterized in that it comprises a steering angle detection computing device to a neutral position of the resulting rotary member by learning.