JP2008273246A - Steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering system capable of solving that problem that, when a vehicle making a turn at a low speed is accelerated, the restoration force of a steering wheel is small, and the steering wheel is not returned to the neutral position. <P>SOLUTION: An electric power steering device 110 has a throttle opening sensor S<SB>TH</SB>for detecting the throttle opening δ<SB>TH</SB>and a vehicle speed sensor S<SB>V</SB>for detecting the vehicle speed V<SB>S</SB>, which constitute an acceleration intention detection means for detecting the degree of the intention for acceleration which is the strength of the will of accelerating a vehicle V by a driver. A steering control ECU 130 detects the intention of acceleration of the driver after the vehicle V makes a turn at a low speed by the acceleration intention detection means, and increases the assist quantity A<SB>H</SB>to be given to the electric power steering device as the intention for acceleration is larger, and increases the restoration force of returning a steering wheel 3 to a neutral position. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steering system including an electric power steering device.

When the vehicle is turned by steering the steering handle, the steering handle returns to the neutral position by self-aligning torque (restoring force) after the vehicle turns.
However, when turning at a low speed, such as turning right or left at an intersection where thin roads intersect, the steering handle does not have sufficient restoring force after turning, and the steering handle does not return to the neutral position. It may be necessary to return the steering handle to the neutral position.

For example, Patent Document 1 discloses a technique for obtaining a suitable steering feeling by changing the assist force of an electric power steering device in accordance with the acceleration of a vehicle. According to this technique, the assisting force of the electric power steering device is reduced during acceleration of the vehicle, so that the steering handle becomes heavy, and instability of traveling of the vehicle can be reduced.
JP 2000-142442 A (see paragraphs 0012 to 0015)

  However, the technique disclosed in Patent Document 1 has not been studied for acceleration. In particular, there is room for improvement because no consideration has been given to the problem of accelerating by turning at a low speed.

  Accordingly, the present invention provides a steering system including an electric power steering device that can appropriately obtain a restoring force for returning a steering handle to a neutral position even when the vehicle turns at a low speed and accelerates. Let it be an issue.

  In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an electric power steering device in which an electric motor generates an auxiliary torque according to at least a steering torque and transmits the auxiliary torque to a steering system of a front wheel, and the electric power A steering control device that controls the steering device, a steering determination unit provided in the steering system returns to a neutral position, a return determination unit that detects a steering wheel return state, and a vehicle speed detection that detects the vehicle speed of the vehicle including the electric power steering device The steering system is configured to include means and acceleration intention detecting means for detecting the presence / absence and magnitude of the acceleration intention, which is the strength of the driver's intention to accelerate. When the driver operates the steering handle to turn the vehicle and the return determination means detects the steering wheel return state, the vehicle speed is low, and the acceleration intention detection means When the acceleration intention is detected, the steering control device increases the restoring force to return the steering handle to the neutral position as the magnitude of the acceleration intention detected by the acceleration intention detection means is larger. It was.

  According to the first aspect of the present invention, when the vehicle turns at a low speed, the restoring force for returning the steering handle to the neutral position increases as the driver intends to accelerate the vehicle. it can.

  The invention according to claim 2 is characterized in that the steering control device obtains the restoring force by driving the electric motor in a direction to return the steering handle to a neutral position.

  According to the second aspect of the present invention, the restoring force can be obtained by driving the electric motor.

  The steering control device may further include a damping control unit that calculates a damper compensation value that increases or decreases the viscosity of the electric power steering device. When the steering wheel is operated to turn the vehicle and the return determination means detects the steering wheel return state, the vehicle speed is low, and the acceleration intention detection means determines the acceleration intention. When detected, the damping control unit calculates the damper compensation value to be smaller as the magnitude of the acceleration intention detected by the acceleration intention detection means is larger.

  According to the third aspect of the present invention, a smaller damper compensation value is set as the acceleration intention is larger, so that the restoring force can be increased as the acceleration intention is larger.

  According to the present invention, it is possible to provide a steering system including an electric power steering device capable of appropriately obtaining a restoring force for returning a steering handle to a neutral position even when the vehicle turns and accelerates at a low speed. Can do.

<< First Embodiment >>
A first embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is an overall conceptual diagram of a four-wheel vehicle to which the steering system according to the first embodiment is applied, and FIG. 2 is a configuration diagram of an electric power steering device.

As shown in FIG. 1, the steering system 100 includes an electric power steering device 110 that assists the steering by the steering handle 3 that steers the front wheels 1L and 1R with the electric motor 4, and a steering control ECU that controls the electric power steering device 110 ( A steering control device 130, a vehicle speed sensor S _V (vehicle speed detection means), a throttle opening sensor S _{TH, and} other various sensors are included.

(Electric power steering device)
As shown in FIG. 2, the electric power steering device 110 includes a main steering shaft 3a provided with a steering handle 3, a shaft 3c, and a pinion shaft 7 connected by two universal joints (universal joints) 3b. A pinion gear 7 a provided at the lower end of the pinion shaft 7 meshes with the rack teeth 8 a of the rack shaft 8 that can reciprocate in the vehicle width direction, and tie rods 9, 9 are provided at both ends of the rack shaft 8. The left and right front wheels 1L, 1R are connected. With this configuration, the electric power steering apparatus 110 can change the traveling direction of the vehicle when the steering handle 3 is operated. Here, the rack shaft 8, the rack teeth 8a, and the tie rod 9 constitute a steering mechanism.
The pinion shaft 7 is supported by a steering gear box (not shown) through bearings 3d, 3e, and 3f at its upper, middle, and lower portions.

In addition, the electric power steering device 110 includes an electric motor 4 that supplies an auxiliary steering force for reducing the steering force by the steering handle 3, and a worm gear 5a provided on the output shaft of the electric motor 4 is connected to a pinion shaft. 7 is meshed with a worm wheel gear 5b.
That is, the worm gear 5a and the worm wheel gear 5b constitute a speed reduction mechanism. The worm gear 5a, the worm wheel gear 5b, the pinion shaft 7, the rack shaft 8, the rack teeth 8a, the tie rods 9, 9 and the like connected to the rotor of the electric motor 4 and the electric motor 4 constitute a steering system.

The electric motor 4 is a three-phase brushless motor including a stator (not shown) having a plurality of field coils and a rotor (not shown) that rotates inside the stator, and mechanically transfers electric energy. It is converted into energy (P _M = ωT _M ).
Here, omega is the angular speed of the electric motor 4, T _M is the torque generated by the motor 4. Further, the relationship between the generated torque T _M and the output torque T _M ^* that can actually be taken out as output is expressed by the following equation (1).
T _M ^* = T _M − (c _m dθ _m / dt + J _m d ² θ _m / dt ² ) i ² (1)
Here, i is a reduction ratio between the worm gear 5a and the worm wheel gear 5b.
From the equation (1), the relationship between the output torque T _M ^* and the motor rotation angle θ _m is defined by the inertia moment J _m of the rotor of the motor 4 and the viscosity coefficient _cm, and is independent of vehicle characteristics and vehicle conditions. is there.

Here, the steering torque applied to the steering wheel 3 Ts, the coefficients of the assist amount A _H, which assists the torque of the motor 4 which is boosted through a reduction mechanism (auxiliary torque), for example, the vehicle speed V _S Let k _A (V _S ) change as a function. In this case, since A _H = k _A (V _S ) × Ts, the pinion torque Tp, which is the road surface load, is expressed by the following equation (2).
Tp = Ts + A _H
= Ts + k _A (V _S ) × Ts (2)
Thus, the steering torque Ts is expressed as the following equation (3).
Ts = Tp / (1 + k _A (V _S )) (3)

Therefore, the steering torque Ts is reduced to 1 / {1 + k _A (V _S )} times the pinion torque Tp (load). For example, if k _A (0) = 2 when the vehicle speed V _S = 0, the steering torque Ts is controlled to be 1/3 lighter than the pinion torque Tp, and when the vehicle speed V _S = 100 km / h, If k _A (100) = 0, the steering torque Ts becomes equal to the pinion torque Tp, and is controlled to feel the steering torque with a firm weight equivalent to that of manual steering. That is, by controlling the steering torque Ts according to the vehicle speed V _S , a light and stable steering torque response feeling is imparted lightly during low-speed traveling and firmly during high-speed traveling.

Further, the assist amount A _H is a quantity that is assisted by the generated torque (assist torque) of the electric motor 4, as the generated torque of the motor 4 (assist torque) is large, the assist amount A _H is increased.

The electric power steering apparatus 110 includes a motor drive circuit 23 for driving the electric motor 4, a resolver 25, a torque sensor S _T to detect the pinion torque T _P applied to the pinion shaft 7, the output of the torque sensor S _T a differential amplifier circuit 21 which amplifies, and a vehicle speed sensor S _V for detecting the speed of the vehicle (vehicle speed).
The steering control ECU 130 of the steering system 100 (see FIG. 1) has an electric power steering control unit 130a (see FIG. 3) which will be described later that drives and controls the electric motor 4 that is a functional unit of the electric power steering device 110. .

The electric motor drive circuit 23 includes a plurality of switching elements such as, for example, a three-phase FET bridge circuit, and is rectangular using a DUTY (DU, DV, DW) signal from the electric power steering control unit 130a (see FIG. 3). A wave voltage is generated and the electric motor 4 is driven.
The motor drive circuit 23 has a function of detecting a three-phase motor current I (IU, IV, IW) using a hall element (not shown).
The resolver 25 detects an electric motor rotation angle θ _m of the electric motor 4 and outputs an angle signal θ. For example, a sensor for detecting a change in magnetoresistance includes a plurality of irregularities at equal intervals in the circumferential direction of a rotor (not shown). Some of them are close to a magnetic rotating body provided with a portion.

Torque sensor S _T is used to detect the pinion torque T _P applied to the pinion shaft 7, a magnetic film so that the opposite direction of the anisotropy in the axial direction two portions of the pinion shaft 7 is deposited, the A detection coil is inserted on the surface of the magnetic film so as to be separated from the pinion shaft 7.
The differential amplifier circuit 21 amplifies the difference in permeability change between the two magnetostrictive films detected by the detection coil as an inductance change, and outputs a torque signal T.

A vehicle speed sensor S _V is for detecting a vehicle speed as a pulse number per unit time, and outputs a vehicle speed signal VS.
The steering control ECU 130, the motor drive circuit 23, and each sensor are driven by power (not shown) supplied from a power source such as a battery.

Returning to FIG. 1, the throttle opening degree sensor S _TH is a sensor that detects the opening degree of a throttle valve (not shown) provided in the intake air passage for taking in the air for fuel combustion into the engine E. Although the structure is not limited, for example, an angle sensor that detects a rotation angle of a valve body that is rotatable in the intake air passage so as to open and close the intake air passage may be used.

(Steering control ECU)
Next, functions of the steering control ECU will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of a steering control ECU of the steering system.

The steering control ECU 130 includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown) and peripheral circuits.
As shown in FIG. 3, the steering control ECU 130 includes an electric power steering control unit 130 a that controls the electric power steering device 110 (see FIG. 2).

(Electric power steering controller)
First, the electric power steering control unit 130a will be described with reference to FIG. 2 as appropriate with reference to FIG.
The electric power steering control unit 130a includes a base signal calculation unit 51, a damper compensation signal calculation unit 52, an inertia compensation signal calculation unit 53, a Q axis (torque axis) PI control unit 54, and a D axis (magnetic pole axis) PI. A control unit 55, a two-axis three-phase conversion unit 56, a PWM conversion unit 57, a three-phase two-axis conversion unit 58, an electric motor speed calculation unit 67, and an excitation current generation unit 59 are provided.

The three-phase two-axis converter 58 converts the three-phase currents IU, IV, and IW of the electric motor 4 detected by the electric motor drive circuit 23 into the D axis that is the magnetic pole axis of the rotor of the electric motor 4 and the D axis manner and converts the two axes of the Q axis is an axis obtained by rotating 90 degrees, the Q-axis current IQ is proportional to the generated torque T _M of the motor 4, D-axis current ID is proportional to the exciting current. The motor speed calculator 67 differentiates the angle signal θ of the motor 4 to generate an angular speed signal ω. The exciting current generating unit 59 generates a target signal for the exciting current of the electric motor 4, but can perform field-weakening control by making the D-axis current and the Q-axis current substantially equal if necessary.

The base signal calculation unit 51 generates a base signal D _T that serves as a reference for the target signal IM ₁ of the output torque T _M ^* from the torque signal T and the vehicle speed signal VS. This signal generation is performed by referring to a base table 51a, which is set in advance by experimental measurement for a vehicle having the same steering function as that of the first embodiment and having a front wheel steering function, based on the torque signal T and the vehicle speed signal VS. The The base signal calculation unit 51 is provided with a dead zone in which the base signal _DT is set to zero when the value of the torque signal T is small, and increases linearly with the gain G1 when the value of the torque signal T becomes larger than this dead zone. It has the characteristics to do. Further, the base signal calculation unit 51 has a characteristic that the output increases with a gain G2 at a predetermined torque value, and the output is saturated when the torque value further increases.
In general, since the load on the road surface (road reaction force) differs depending on the traveling speed, the gain of the vehicle is adjusted by the vehicle speed signal VS. The load is heaviest during stationary operation at zero vehicle speed, and the load is relatively light at medium and low speeds. Thus, the base signal computing part 51, the gain according to the vehicle speed V _S becomes large and fast (G1, G2) to low and set a larger dead zone N1, driving the road information manual steering area greater taken Give to the person. That is, firm responsive feeling from the steering torque Ts in accordance with the increase of the vehicle speed V _S is applied. At this time, it is necessary to perform inertia compensation also in the manual steering region.

Returning to FIG. 3, the damper compensation signal calculation unit (damping control unit) 52 has a steering damper function for compensating for the viscosity of the steering system and for compensating for a decrease in convergence when the vehicle travels at a high speed. The steering damper function is realized by referring to the damper table 52a corresponding to the angular velocity ω.
The characteristic function of the damper table 52a has a characteristic that the damper compensation value I increases linearly as the angular velocity ω of the motor 4 increases, and the damper compensation value I rapidly increases at a predetermined speed.
Further, as the value of the vehicle speed signal VS is higher, the gain is increased to attenuate the output torque T _M ^* of the electric motor 4 according to the angular speed ω of the electric motor 4, that is, the turning speed. In other words, the higher the value of the vehicle speed signal VS, the smaller the road surface reaction force. Therefore, the damper compensation signal calculation unit 52 outputs the angular velocity ω of the electric motor 4 in order to brake the fast movement of the motor and provide stability. Control is suppressed. Due to this steering damper effect, the convergence of the steering wheel 3 can be improved and the vehicle characteristics can be stabilized.

Returning to FIG. 3 again, the adder 61 subtracts the damper compensation value I which is the output signal of the damper compensation signal calculator 52 from the output signal _DT of the base signal calculator 51, and the adder 62 by adding the output signal of the output signal and the inertia compensation signal computing part 53 of the vessel 61 in which an output signal IM _1.

  The inertia compensation signal calculation unit 53 compensates for the influence of the inertia of the steering system, and can output an output signal corresponding to the input torque signal T by referring to the inertia table 53a.

Further, the inertia compensation signal calculation unit 53 compensates for a decrease in responsiveness due to the inertia of the rotor of the electric motor 4. In other words, when switching the rotation direction from the normal rotation to the reverse rotation or from the reverse rotation to the normal rotation, the electric motor 4 tries to maintain the state by inertia, so the rotation direction is not switched immediately. Therefore, the inertia compensation signal calculation unit 53 performs control so that the switching of the rotation direction of the electric motor 4 coincides with the timing at which the rotation direction of the steering handle 3 is switched. In this manner, the inertia compensation signal calculation unit 53 improves the response delay of the steering due to the inertia and viscosity of the steering system and provides a clean steering feeling.
Also, it is practically sufficient for vehicle characteristics such as FF (Front engine Front wheel drive), FR (Front engine Rear wheel drive), RV (Recreation Vehicle) and sedan, and steering characteristics that vary depending on vehicle speed, road surface, etc. Steering feeling is given.

The output signal IM ₁ of the adder 62 is a current target signal that defines the torque of the motor 4.

The adder 64 subtracts the Q-axis current IQ from the output signal IM ₁ of the adder 62 to generate a deviation signal IE. The Q-axis (torque axis) PI control unit 54 performs P (proportional) control and I (integral) control so that the deviation signal IE decreases.
The adder 65 subtracts the D-axis current ID from the output signal of the exciting current generator 59. The D-axis (magnetic pole axis) PI control unit 55 performs PI feedback control so that the output signal of the adder 65 decreases.

The two-axis three-phase converter 56 converts the two-axis signal of the output signal VQ of the Q-axis (torque axis) PI control unit 54 and the output signal VD of the D-axis (magnetic pole axis) PI control unit 55 into three-phase signals UU, UV , Convert to UW. The PWM converter 57 generates a DUTY signal (DU, DV, DW) that is an ON / OFF signal (PWM (Pulse Width Modulation) signal) having a pulse width proportional to the magnitude of the three-phase signals UU, UV, UW. .
In addition, the angle signal θ of the electric motor 4 is input to the biaxial three-phase conversion unit 56 and the PWM conversion unit 57, and a signal corresponding to the magnetic pole position of the rotor is output.

Further, the steering control ECU 130 is provided with return determination means. In this embodiment, when the steering handle 3 is at the maximum steering angle, when a force to return to the neutral position is applied to the steering handle 3, the steering control ECU 130 determines that the steering handle 3 is neutral. It is possible to determine the “return state” that has started to return to the position. That is, the steering control ECU130, when the steering wheel 3 by the resolver 25 is detected to be in the maximum steering angle, a torque sensor S _T, torque is applied in the direction the steering wheel 3 is returned to the neutral position By detecting this, the “return state” is determined. Thus, the resolver 25 and the torque sensor S _T becomes the return determining means as set forth in claim.

  As return determination means, for example, a known technique such as the technique disclosed in Japanese Patent Application Laid-Open No. 2002-187562 disclosed by the applicant of the present application may be used.

Conventionally, when the vehicle V turns, the driver operates the steering handle 3 in the turning direction, that is, the so-called forward movement, the steering torque is assisted by the assist torque calculated by the steering control ECU 130. When the steering wheel returns to the neutral position by self-aligning torque, the steering control ECU 130 has little assist.
When the vehicle V is at a low speed, the self-aligning torque acts as an entraining torque (negative restoring torque) on the inner ring side, and the absolute value is based on the absolute value of the self-aligning torque (restoring torque) acting on the outer ring side. Since the steering wheel 3 is large, the steering wheel self-aligning torque obtained by adding the self-aligning torque on the inner ring side and the self-aligning torque on the outer ring side becomes the entrainment torque (negative restoring torque). The restoring force sufficient to return to the neutral position cannot be obtained. In this state, when the driver accelerates the vehicle V, while the steering wheel 3 is not returned to the neutral position, the vehicle speed V _S becomes greater, the driver is in the neutral position by operating the steering wheel 3 Need to return. As a result, the behavior of the vehicle V may become unstable.

Therefore, when the vehicle V shown in FIG. 1 turns slightly at a low speed by the steering system 100 including the electric power steering device 110 configured as described above, the steering control ECU 130 performs the driver's intention to accelerate, that is, when turning. A suitable restoring force is applied to the steering handle 3 based on the determination as to whether or not the driver has performed an operation of accelerating the vehicle V.
Specifically, when the vehicle V is at a low speed and the intention of acceleration is detected when the steering handle 3 returns, the steering control ECU 130 sets the auxiliary torque in the neutral direction to a large value and drives the electric motor 4. The steering handle 3 is returned to the neutral direction, and the return of the handle is promoted.
The low speed is a speed of about 10 km / h or less in the first embodiment.

In the first embodiment, the steering control ECU 130 (see FIG. 1) is characterized in that the driver's intention to accelerate is determined from the throttle opening δ _TH and the vehicle speed V _S.

As shown in FIG. 1, the steering control ECU 130, vehicle speed sensor _{S V} and the throttle opening sensor _{S TH} is connected, it is possible to detect the vehicle speed _{V S,} and a throttle opening degree _{[delta] TH.} Further, the static characteristics of the throttle opening δ _TH and the vehicle speed V _S are set in advance as the characteristics of the vehicle V. FIG. 4 is a diagram showing the characteristics of the throttle opening and the vehicle speed. As shown in FIG. 4, the throttle opening [delta] _TH and the vehicle speed V _S, has a correlation to the vehicle speed V _S is increased with the increase of the throttle opening [delta] _TH. The correlation shown by the solid line in FIG. 4 shows the relationship between the throttle opening δ _TH and the vehicle speed V _S when the driver operates the throttle opening δ _TH when accelerating the vehicle V. , Called static characteristics. And the V _SS the vehicle speed on the static characteristics. Since the throttle opening δ _TH is operated when the driver depresses the accelerator pedal, the static characteristic is a characteristic when the driver operates the accelerator pedal.

Meanwhile, when you want to quickly cause accelerated the vehicle V in the low speed traveling (see FIG. 1), the driver from depressing larger the accelerator pedal, the throttle opening degree [delta] _TH increases rapidly. However, the vehicle speed V _S is, by the time it reaches the vehicle speed V _S corresponding to the throttle opening [delta] _TH, the time lag is generated.
That is, as shown by a broken line in FIG. 4, in the vehicle V running at low speed, the vehicle speed V _S does not follow the static characteristic even when the throttle opening δ _TH increases (the characteristic that the vehicle speed V _S increases with a delay) , Referred to as acceleration characteristics).

  In the first embodiment, when there is a time lag between the static characteristic indicated by the solid line in FIG. 4 and the acceleration characteristic indicated by the broken line, the steering control ECU 130 (see FIG. 1) allows the driver to change the vehicle V. It is determined that there is an intention to accelerate quickly, that is, there is an intention to accelerate. Then, a restoring force for returning the steering handle 3 (see FIG. 1) to the neutral position is obtained by assisting the steering wheel return based on the magnitude of the acceleration intention. Further, the greater the intention to accelerate, the smaller the damper compensation value I and the lower the viscosity of the steering system, thereby increasing the restoring force for returning the steering handle 3 to the neutral position.

Driver, the greater the intention to be quickly brought accelerated the vehicle V (see FIG. 1), depresses larger the accelerator pedal, namely to open quickly the throttle opening [delta] _TH, large delay in acceleration characteristics with respect to the static characteristic Become. Therefore, the steering control ECU 130 (see FIG. 1) determines that the intention of acceleration is greater as the delay of the acceleration characteristic with respect to the static characteristic is greater. Specifically, the steering control ECU 130 determines the difference ΔV _S (= V _SS −) between the vehicle speed V _SS calculated from the throttle opening δ _TH and the vehicle speed V _S input from the vehicle speed sensor S _V (see FIG. 1). The magnitude of the driver's intention to accelerate is determined based on the magnitude of V _S ). From the above, in the first embodiment _(see FIG. 1) a throttle opening degree sensor S _TH for detecting a throttle opening [delta] _TH, the vehicle speed sensor S _V and the acceleration intent of the size detecting a vehicle speed V _S The steering control ECU 130 for determining constitutes the acceleration intention detecting means described in the claims.

Here static properties, as data that associates the throttle opening [delta] _TH and the vehicle speed V _SS, the steering control ECU130 may be stored in a storage device (not shown) provided (see Figure 1). Steering control ECU130, by reading the vehicle speed _{V SS} corresponding to the input throttle opening _{[delta] TH,} calculates the vehicle speed _{V SS} to the throttle opening degree _{[delta] TH} in static characteristics.

Alternatively, a function indicating static characteristics may be incorporated as a calculation formula into a program for driving a CPU (not shown) of the steering control ECU 130 (see FIG. 1). The steering control ECU 130 can calculate the vehicle speed V _SS from the throttle opening δ _TH by using a calculation formula of a function indicating static characteristics.

When the steering control ECU 130 (see FIG. 1) determines that the driver has an intention to accelerate when the vehicle V turns at a low speed, the steering handle 3 corresponds to the magnitude of the acceleration intention. an auxiliary torque to provide a suitable restoring force is calculated as the assist amount a _H. When the steering handle 3 (see FIG. 1) is steered, an auxiliary torque (assist amount A _H ) is added to the front wheel 1 (see FIG. 1) to increase the restoring force, and the steering handle 3 Return to the neutral position.

As described above, the assist amount A _H can be calculated by, for example, a value (k _A (V _S ) × Ts) obtained by integrating k _A (V _S ) that changes as a function of the vehicle speed V _S and the steering torque Ts. In this case, when the vehicle speed V _S is large, the function k _A (V _S ) is small. Accordingly, when the vehicle speed _{V S} is large, the assist amount _{A H} is reduced. FIG. 5A is a graph showing the relationship between the steering torque, the assist amount, and the acceleration intention size, and FIG. 5B is a graph showing the relationship between the motor angular velocity, the damper compensation value I, and the acceleration intention size. is there.
As shown in (a) of FIG. 5, the assist amount A _H is increased substantially in proportion to the steering torque Ts. As the acceleration intention increases, the proportional gain increases. That is, as indicated by a broken line in FIG. 5A, the slope is steep and is proportional to the steering torque Ts.

Therefore, the steering control ECU130, by determining the magnitude of the acceleration intention, the vehicle speed V _S is estimated that the increase, a large vehicle speed V _S assist amount A _H corresponding to the estimated based on the acceleration intention size Set. As a result, even when the vehicle V is at a low speed, if there is an intention to accelerate, a restoring force for returning the steering handle 3 to the neutral position can be obtained.
As described above, when the technique disclosed in Japanese Patent Application Laid-Open No. 2002-187562 is used as the return determination means, the “return state” is a state in which the assist in the steering direction is applied. In order to return the steering handle 3 to the neutral position, the steering control ECU 130 may reduce the amount of assist as the acceleration intention increases, as indicated by a dashed line in FIG. Good.

  Moreover, the steering system which comprises the electric power steering apparatus 110 (refer FIG. 1) has viscosity. Therefore, the steering control ECU 130 (see FIG. 1) includes a damper compensation signal calculation unit 52 as shown in FIG. 3, and performs damper control to compensate the viscosity of the steering system.

In the present embodiment, as shown in FIG. 5B, the steering control ECU 130 (see FIG. 1) decreases the damper compensation value I as the acceleration intention increases, thereby reducing the viscosity of the steering system. Set.
Thus, by reducing the viscosity of the steering system, the resistance to returning the steering wheel is reduced, and the restoring force for returning the steering handle 3 (see FIG. 1) to the neutral position is increased.

Then, the steering control ECU 130 (see FIG. 1), based on the magnitude of the acceleration intention, sets the assist amount _{A H} of the steering wheel 3 (see FIG. 1).

FIG. 6 is a flowchart showing steps for obtaining a suitable restoring force based on the magnitude of the acceleration intention. Hereinafter, with reference to FIG. 6, a step in which the steering control ECU 130 obtains a suitable restoring force based on the magnitude of the acceleration intention will be described (see FIGS. 1 to 5 as appropriate).
In the control shown in FIG. 6, the vehicle speed V _S is low (10 km / h or less), and the steering handle 3 is set to the neutral position, that is, from the maximum steering angle δ _{MAX on} either the left or right side. The start of the steering wheel return state in which the steering angle δ returns to 0 ° is triggered by the detection of the return determination means.

Steering control ECU130, in order to detect a driver's intention to accelerate, reads the throttle opening _{[delta] TH} (step S1). Further, the steering control ECU 130 reads the vehicle speed V _S (step S2). Then, the vehicle speed V _SS corresponding to the throttle opening δ _TH in the static characteristics is calculated (step S3).

Steering control ECU130 includes the vehicle speed _{V S} inputted from the vehicle speed sensor _{S V,} and compares the vehicle speed _{V SS} of the calculated static characteristics, if the vehicle speed _{V S} is smaller than the vehicle speed _{V SS} of the static characteristic (step S4 → Yes), the steering control ECU 130 determines that the driver intends to accelerate, and the control proceeds to step S5. On the other hand, when the vehicle speed _{V SS} of the static characteristics of the above vehicle speed _{V S} (step S4 → No), the steering control ECU130 judges no acceleration intention of the driver to set the normal assist amount _{A H} (step S10 ). Further, the steering control ECU 130 sets a normal damper compensation value I (step S11). If the steering handle 3 is in the neutral position (step S12 → Yes), the steering control ECU 130 ends the control, but if the steering handle 3 is not in the neutral position (step S12 → No), the steering control ECU 130 is Control is returned to step S1.

On the other hand, when the steering control ECU 130 determines that the driver intends to accelerate (step S4 → Yes), the steering control ECU 130 determines the magnitude of the driver's intention to accelerate (step S5). As described above, it can be determined that the greater the delay in the acceleration characteristic with respect to the static characteristic shown in FIG. That is, the steering control ECU130 includes the vehicle speed _{V SS} of the static characteristic corresponding to the throttle opening _{[delta] TH} to read, the difference [Delta] V _S between the vehicle speed _{V S} inputted from the vehicle speed sensor _{S V (= V SS -V S} ) The steering control ECU 130 determines that the driver's intention to accelerate is larger as ΔV _S is larger.

Then, the steering control ECU 130 sets a damper compensation value I based on the magnitude of the acceleration intention (step S6). That is, when the acceleration intention is large, the damper compensation value I is set small.
In step S6, the method of setting the damper compensation value I corresponding to ΔV _S (the magnitude of the intention of acceleration) is not limited. For example, ΔV _S is divided by several threshold values and divided by threshold values. A suitable damper compensation value I corresponding to the angular velocity ω of the electric motor 4 may be set for each range and stored in a storage device (not shown) of the steering control ECU 130 as table format data. The steering control ECU 130 can set a suitable damper compensation value I by reading the damper compensation value I corresponding to the calculated ΔV _S and the angular velocity ω of the motor 4 from the data in the table format.

Further, a calculation formula for calculating the damper compensation value I from ΔV _S and the angular velocity ω of the electric motor 4 may be incorporated in a program for driving a CPU (not shown) of the steering control ECU 130. The CPU (not shown) of the steering control ECU 130 can calculate the damper compensation value I using a calculation formula incorporated based on the calculated ΔV _S and the angular velocity ω.

Further, the steering control ECU130 sets the assist amount _{A H,} based on the magnitude of the acceleration intention and the vehicle speed _{V S} (step S7).
Here, at step S7, a method of setting the assist amount A _H, based on the magnitude of the acceleration intention is not limited to, for example, the acceleration intention size, the equation for calculating the assist amount A _H proportionality constant The method of using as a parameter can be considered.

A difference in the first embodiment, the magnitude of the acceleration intention, the vehicle speed V _SS of the static characteristic corresponding to the throttle opening [delta] _TH read, the vehicle speed V _S inputted from the vehicle speed sensor S _V checked by ΔV _S. Therefore, in addition to the vehicle speed V _S , ΔV _S is set as A _H = k _A (V _S , ΔV _S ) × Ts as a parameter of a proportional constant in the equation for calculating the assist amount A _H. Since it is preferable to increase the assist amount A _H as ΔV _S increases, the proportional constant k _A (V _S , ΔV _S ) is set to a larger value as ΔV _S increases.

[Delta] V _S proportional constant _{k A (V S, ΔV S} ) of formula for calculating the assist amount A _H corresponding but not how to set the limit, for example, by separating the [Delta] V _S at some threshold _A method of setting a suitable proportionality constant k _A (V _S , ΔV _S ) corresponding to ΔV _S for each range delimited by the threshold value is conceivable.
The proportional constant k _A (V _S , ΔV _S ) may be stored in a storage device (not shown) of the steering control ECU 130. The steering control ECU 130 reads the proportional constant k _A (V _S , ΔV _S ) determined for each vehicle speed V _S corresponding to the calculated ΔV _S from a storage device (not shown), thereby obtaining the proportional constant k _A (V _S , ΔV _S ) can be set.

The proportional constant _{k A (V S, ΔV S} ) steering control ECU130 is set by integrating the steering torque Ts, can be calculated assist amount _{A H.}

Further, a calculation formula for calculating proportional constants k _A (V _S , ΔV _S ) using the vehicle speed V _S and ΔV _S as parameters may be incorporated in a program for driving a CPU (not shown) of the steering control ECU 130. The CPU (not shown) of the steering control ECU 130 can calculate the proportional constant k _A (V _S , ΔV _S ) using the built-in calculation formula based on the vehicle speed V _S and ΔV _S.

Then, the steering control ECU 130 determines whether the steering handle 3 is in the neutral position, and if it is in the neutral position (step S8 → Yes), the control is finished. When the steering handle 3 is not in the neutral position (step S8 → No), the steering control ECU 130 determines the magnitude of the acceleration intention, and when the acceleration intention changes (step S9 → Yes), the steering control ECU 130 Then, control returns to step S6. That is, the assist amount _AH and the damper compensation value I based on the changed acceleration intention are set. When the acceleration intention does not change (step S9 → No), the steering control ECU 130 returns the control to step S8.

Here, the process in step S9 will be described in detail. The steering control ECU 130 reads the throttle opening δ _TH and the vehicle speed V _S and calculates the static vehicle speed V _SS . Then, the vehicle speed _{V SS} of the static characteristics, when the difference [Delta] V _S between the vehicle speed _{V S} inputted from the vehicle speed sensor _{S V (= V SS -V S} ) has been changed [Delta] V _S calculated in step S5 The steering control ECU 130 determines that the acceleration intention has changed.
Then, in order to set the assist amount _AH and the damper compensation value I corresponding to the changed acceleration intention, the control is returned to step S6.

Figure 7 is a graph showing the relationship between the steering angle and the vehicle speed of the steering resiliency and steering wheel, and the broken line (in this embodiment, 10 km / h) vehicle speed V _S is slow when the long and short dash line in the vehicle speed When V _S is a very low speed (for example, 4 to 7 km / h), the solid line indicates a case where the vehicle speed V _S is a very low speed (for example, 3 km / h or less).
As shown in FIG. 7, a steering restoring force is small as the vehicle speed V _S is low. This is because when the vehicle speed V _S is low, acts as a self aligning torque winding torque acting on the inner ring side (negative restoring torque), the self-aligning torque absolute value acts on the outer ring side (restoration torque) This is because the self-aligning torque of the steered wheel obtained by the sum of the self-aligning torque on the inner ring side and the self-aligning torque on the outer ring side becomes the entrainment torque (negative restoring torque). is there. This indicates that the steering handle 3 is unlikely to return to the neutral position if the vehicle speed V _S is low.
In the first embodiment, by even slow the vehicle V after turning determining the magnitude of the acceleration intention, the steering wheel 3 is to assist in the direction returning to the neutral position with a large assist amount A _H When the driver intends to accelerate, the steering handle 3 can be returned to the neutral position even if the vehicle V is at a low speed. Further, the greater the acceleration intention is, the smaller the damper compensation value I is, the viscosity of the steering system is reduced, and the steering handle 3 is easily returned to the neutral position.

As described above, in the first embodiment, the magnitude of the intention of acceleration can be determined based on the throttle opening _δTH , and when the vehicle V makes a small turn at a low speed, the driver when accelerated the V, steering control ECU130 can provide an assist amount a _H, based on the acceleration intention that determines the steering wheel 3. Furthermore, when the acceleration intention is large, the damper compensation value I is decreased to reduce the viscosity of the steering system, whereby a suitable restoring force of the steering handle 3 can be obtained. Then, the restoring force obtained by driving the electric motor 4 so as to obtain the assist amount A _H, based on the acceleration intention, that the steering wheel 3 can be returned to the neutral position, an excellent effect.

Here, in step S4 of FIG. 6, the difference between the vehicle speed _{V SS} of the static characteristic corresponding to the throttle opening _{[delta] TH} read, the vehicle speed _{V S} inputted from the vehicle speed sensor _{S V ΔV S (= V SS} - If V _S) is negative, i.e., it determines that the vehicle speed _{V S} inputted from the vehicle speed sensor _{S V} is, when greater than the vehicle speed _{V SS} of the static characteristics, the steering control ECU130 the driver has an intention to decelerate It may be configured to. In this case, the steering control ECU130 is to reduce the assist amount A _H, due to the excessive return of the steering wheel 3, a configuration for preventing the unstable travel of the vehicle V.

<< Second Embodiment >>
FIG. 8 is an overall conceptual diagram of a four-wheel vehicle to which the steering system according to the second embodiment is applied. In the second embodiment, the negative pressure of the intake manifold which varies in response to the rotational speed of the engine E (hereinafter, referred to as intake negative pressure) determine the driver's intention to accelerate based on P _b and the engine rotational speed Ne It is characterized by doing. A restoring force for returning the steering handle 3 to the neutral position is obtained by assisting the steering wheel return based on the magnitude of the acceleration intention. Further, the greater the intention to accelerate, the smaller the damper compensation value I and the lower the viscosity of the steering system, thereby increasing the restoring force for returning the steering handle 3 to the neutral position.
Therefore, as shown in FIG. 8, a rotational speed sensor S _NE for detecting a pressure sensor S _PB and the engine rotational speed Ne for detecting an intake negative pressure is provided in the steering system 100.
In addition, about the structure equivalent to the structure of the steering system 100 concerning 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The pressure sensor _SPB may be a pressure gauge that detects the pressure in the intake manifold. Here, the pressure in the intake manifold has a static characteristic that the negative pressure increases when the engine E is in an idle state, and approaches the atmospheric pressure as the throttle opening _δTH increases, and the engine speed Ne increases. Have. FIG. 9 is a graph showing static characteristics of the intake negative pressure and the engine speed. As shown in FIG. 9, the intake negative pressure P _b is to change in the following areas atmospheric pressure sensor S _PB may be a negative pressure gauge capable of measuring a negative pressure below atmospheric pressure.

The rotational speed sensor S _NE is a sensor that detects the engine rotational speed Ne of the rotational shaft of the engine E, and its configuration is not limited. For example, a control device (not shown) that controls the engine E is not shown. The rotational speed calculated from the crank angle sensor (rotary encoder) may be used as the engine rotational speed Ne.
Then, the engine rotational speed Ne of the pressure sensor _{S PB} intake negative pressure detected _{P b} and the rotation speed sensor _{S NE} detects, may be input to the steering control ECU 130.

When the driver accelerates the vehicle V (see FIG. 8) by a normal accelerator operation, the intake negative pressure _Pb and the engine rotational speed Ne have a correlation shown by the static characteristics shown by the solid line in FIG. Here, the intake negative pressure _PbS on the static characteristics corresponding to the engine rotational speed Ne is used.
Meanwhile, when you want to quickly cause accelerated the vehicle V in the low-speed running, the driver from depressing larger the accelerator pedal, the throttle opening degree [delta] _TH increases rapidly. When the throttle opening [delta] _TH is rapidly opened, because the flow is rapid fuel and air mixtures into the intake manifold, the intake negative pressure P _b rises rapidly. However, the engine rotational speed Ne is, by the time reaches the engine rotational speed Ne corresponding to the intake negative pressure P _b, the time lag is generated.
That is, as shown by the broken line in FIG. 9, in the vehicle V in the low-speed running, even if the intake negative pressure P _b and the throttle opening [delta] _TH increases increases, the engine rotational speed Ne is follow the static characteristics The characteristic of increasing with a delay (hereinafter referred to as negative pressure characteristic) is shown.

  In the second embodiment, when there is a time delay between the static characteristic indicated by the solid line in FIG. 9 and the negative pressure characteristic indicated by the broken line, the steering control ECU 130 (see FIG. 8) It is determined that the user wants to accelerate quickly, that is, has an intention to accelerate.

In addition, the driver depresses the accelerator pedal more greatly as the intention of accelerating the vehicle V is larger. For this reason, the throttle opening _δTH is rapidly opened and the intake negative pressure _Pb is rapidly increased, so that the delay of the negative pressure characteristic with respect to the static characteristic is increased. Therefore, the steering control ECU 130 (see FIG. 8) determines that the intention of acceleration is greater as the delay of the negative pressure characteristic with respect to the static characteristic is greater.
Specifically, the steering control ECU130 the static characteristics of the pressure sensor _{S PB} and the intake negative pressure _{P b} of (see FIG. 8), detects the rotational speed sensor _{S NE} engine rotational speed Ne (see FIG. 8) detects as the difference [Delta] P _b of the intake negative pressure P _bS above is large, it is determined that the acceleration intention is large. From the above, in the second embodiment, the rotational speed sensor S _NE for detecting the engine rotational speed _Ne, determines the steering control pressure sensor S _PB and acceleration intent of the size detecting the intake negative pressure P _b ECU 130 Constitutes the acceleration intention detecting means described in the claims.

When the steering control ECU 130 (see FIG. 8) determines that the driver has an intention to accelerate when the vehicle V turns slightly at a low speed, as in the first embodiment, the magnitude of the intention to accelerate is determined. in response to, an auxiliary torque to provide a suitable restoring force to the steering wheel 3, is calculated as the assist amount a _H. When the steering handle 3 (see FIG. 8) is steered, an auxiliary torque (assist amount A _H ) is added to the front wheel 1 (see FIG. 8) to increase the restoring force, and the steering handle 3 To the neutral position

Here static properties, as data that associates the intake negative pressure P _b and the engine rotational speed Ne, the steering control ECU130 may be stored in a storage device (not shown) provided (see Figure 8). Steering control ECU130, by reading the intake negative pressure P _bS corresponding to the detected engine rotational speed Ne, can be calculated intake negative pressure P _bS corresponding to the engine rotational speed Ne in the static characteristics.

Alternatively, a function indicating static characteristics may be incorporated in a program for driving a CPU (not shown) of the steering control ECU 130. Steering control ECU130 can be by a function showing a static characteristic, it calculates the intake negative pressure _{P bS} from the engine rotational speed Ne.

FIG. 10 is a flowchart showing steps for determining the magnitude of the intention of acceleration based on the negative pressure characteristic and setting a suitable restoring force. Hereinafter, with reference to FIG. 10, a step in which the steering control ECU 130 sets a suitable restoring force based on the magnitude of the acceleration intention will be described (see FIGS. 1 to 9 as appropriate).
In the control shown in FIG. 10, the vehicle speed V _S is low (in this embodiment, 10 km / h or less), and the steering handle 3 is moved from either the left or right maximum turning angle δ _MAX. The start of the steering wheel return state returning to the neutral position, triggered by the detection of the return determination means, is equivalent to the flowchart shown in FIG. 6 in the first embodiment.

Steering control ECU130, in order to detect a driver's intention to accelerate, reads the intake negative pressure _{P b} that is input from the pressure sensor _{S PB} (step S21). Further, the steering control ECU130 reads the engine rotational speed Ne that is inputted from the rotational speed sensor _{S NE} (Step S22). Then, an intake negative pressure _PbS corresponding to the engine rotational speed Ne in the static characteristics is calculated (step S23).

Steering control ECU130 includes the intake negative pressure P _b read, to compare the intake negative pressure P _bS of the calculated static properties, is less than the intake negative pressure P _b read by the intake negative pressure P _bS static characteristics (Step S24 → Yes), the steering control ECU 130 determines that the driver intends to accelerate, and the control proceeds to Step S25. On the other hand, when the intake negative pressure P _bS of static characteristics is equal to or higher than the read intake negative pressure P _b (step S24 → No), the steering control ECU 130 determines that the driver does not intend to accelerate, and the normal assist amount A _H Is set (step S30). Further, the steering control ECU 130 sets a normal damper compensation value I (step S31). If the steering handle 3 is in the neutral position (step S32 → Yes), the steering control ECU 130 ends the control, but if the steering handle 3 is not in the neutral position (step S32 → No), the steering control ECU 130 is Control is returned to step S21.

When the steering control ECU 130 determines that the driver intends to accelerate (step S24 → Yes), the steering control ECU 130 determines the magnitude of the driver's intention to accelerate (step S25). As described above, it can be determined that the greater the difference between the static characteristic and the negative pressure characteristic shown in FIG. That is, the steering control ECU130 the pressure sensor _{S PB} and the intake negative pressure _{P b} detected by the rotational speed sensor _{S NE} difference [Delta] P _b of the intake negative pressure _{P bS} on the static characteristics of the engine rotational speed Ne to detect ( = P _b −P _bS ), and the larger ΔP _b is, the greater the steering control ECU 130 determines that the driver intends to accelerate.

Then, the steering control ECU 130 sets a damper compensation value I based on the magnitude of the acceleration intention (step S26). That is, when the acceleration intention is large, the damper compensation value I is set small.
Although not how to set the damper compensation value I limit in response to [Delta] P _b, for example, by separating the [Delta] P _b at some threshold, for each range separated by a threshold, the angular velocity ω of the electric motor 4 A corresponding suitable damper compensation value I may be set and stored in a storage device (not shown) of the steering control ECU 130 as table format data. Steering control ECU130 may set the calculated [Delta] P _b and the motor 4 of the angular velocity by reading the corresponding damper compensation value I from the table format data into ω suitable damper compensation value I.

Further, a formula for calculating the damper compensation value I from the angular velocity ω of the [Delta] P _b and the motor 4, may be previously incorporated in the program for driving the CPU (not shown) of the steering control ECU 130. CPU (not shown) of the steering control ECU130 uses an embedded calculation formula based on the calculated [Delta] P _b angular velocity omega, it is possible to calculate the damper compensation value I.

Further, the steering control ECU130 sets the assist amount _{A H,} based on the magnitude of the acceleration intention and the vehicle speed _{V S} (step S27).
Here, in step S27, a method of setting the assist amount A _H, based on the magnitude of the acceleration intention and the vehicle speed V _S is not limited to, for example, the acceleration intention and the vehicle speed V _S size, the assist amount A A method is conceivable in which _H is used as a parameter of a proportional constant in the equation for calculating _H.

As described above, when there is the driver intends to accelerate, the assist amount A _H is suitable resiliency is set to a value in consideration of the vehicle speed V _S is increased is obtained. Therefore, the steering control ECU130, by calculating the assist amount A _H in view of the acceleration intention of the size can be calculated assist amount A _H corresponding to the vehicle speed V _S was increased. Then, in the second embodiment determines the difference [Delta] P _b of the intake negative pressure P _bS on the static characteristics of the engine rotational speed Ne of the rotational speed sensor S _NE is detected. Therefore, in addition to the vehicle speed V _S , ΔP _b is set as A _H = k _A (V _S , ΔP _b ) × Ts as a parameter of a proportional constant in the equation for calculating the assist amount A _H. Then, since it is preferable to increase the assist amount _{A H} greater the [Delta] P _b, is a proportional constant _{k A (V S, ΔP b} ) is a larger value the larger the [Delta] P _b.

Wherein the proportional constant _{k A (V S, ΔP b} ) for calculating the assist amount A _H corresponds to [Delta] P _b but is not limited to how to set, for example, by separating the [Delta] P _b at some threshold _A method of setting a suitable proportionality constant k _A (V _S , ΔP _b ) determined for each vehicle speed V _S corresponding to ΔP _b for each range delimited by the threshold value can be considered.
The proportional constant k _A (V _S , ΔP _b ) may be stored in a storage device (not shown) of the steering control ECU 130. The steering control ECU 130 reads the proportional constant k _A (V _S , ΔP _b ) corresponding to the vehicle speed V _S and ΔP _b from a storage device (not shown), thereby obtaining the proportional constant k _A (V _S , ΔP _b ). Can be set.

Then, the steering control ECU130 is by integrating the proportional constant _{k A (V S, ΔP b} ) the steering torque Ts is set, can be calculated assist amount _{A H.}

Further, a calculation formula for calculating a proportional constant k _A (V _S , ΔP _b ) using the vehicle speed V _S and ΔP _b as parameters may be incorporated in a program for driving a CPU (not shown) of the steering control ECU 130. The CPU (not shown) of the steering control ECU 130 can calculate a proportional constant k _A (V _S , ΔP _b ) using a calculation formula incorporated based on the vehicle speed V _S and ΔP _b .

Then, the steering control ECU 130 determines whether or not the steering handle 3 is in the neutral position, and if it is in the neutral position (step S28 → Yes), the control is terminated. When the steering handle 3 is not in the neutral position (step S28 → No), the steering control ECU 130 determines the magnitude of the acceleration intention, and when the acceleration intention changes (step S29 → Yes), the steering control ECU 130 Then, control returns to step S26. That is, the assist amount _AH and the damper compensation value I based on the changed acceleration intention are set. When the acceleration intention does not change (step S29 → No), the steering control ECU 130 returns the control to step S28.

Here, describing in detail the process in step S29, the steering control ECU130 reads the intake negative pressure _{P b} and the engine rotational speed Ne, the static characteristics, calculates the intake negative pressure _{P bS} corresponding to the engine rotational speed Ne . Then, the intake negative pressure _{P b} read, when the difference [Delta] P _b of the intake negative pressure _{P bS} of the calculated static characteristics, that is changing the [Delta] P _b calculated in step S25, the steering control ECU130 the driver It is determined that the acceleration intention has changed. Then, in order to set the assist amount _AH and the damper compensation value I corresponding to the changed acceleration intention, the control is returned to step S26.

As described above, in the second embodiment, the intake negative pressure P _bS on the static characteristics at the engine rotation speed Ne detected by the rotation speed sensor S _NE and the intake negative pressure P _b detected by the pressure sensor S _PB are _compared . The difference ΔP _b (= P _b −P _bS ) is calculated, and the larger ΔP _b is, the more the steering control ECU 130 determines that the driver's intention to accelerate is larger, and the assist amount A _H based on the determined acceleration intention size. Can be provided to the steering handle 3. Furthermore, when the acceleration intention is large, the damper compensation value I is decreased to reduce the viscosity of the steering system, whereby a suitable restoring force of the steering handle 3 can be obtained. Then, the restoring force obtained by driving the electric motor 4 so as to obtain the assist amount A _H, based on the acceleration intention, that the steering wheel 3 can be returned to the neutral position, equivalent to the first embodiment Excellent effect.

Here, in step S24 of FIG. 10, the difference [Delta] P _b of the intake negative pressure _{P bS} on the static characteristics of the engine rotational speed Ne, the intake negative pressure _{P b} of the pressure sensor _{S PB} is detected ₍₌ P b -P _{If bS)} is negative, i.e., the intake negative pressure _{P bS} on static characteristics, if greater than the intake negative pressure _{P b} of the pressure sensor _{S PB} is detected, steering control ECU130 the driver deceleration intent The structure which determines with having may be sufficient. In this case, the steering control ECU130 is to reduce the assist amount A _H, due to the excessive return of the steering wheel 3, a configuration for preventing the unstable travel of the vehicle V.

<< Third Embodiment >>
In the third embodiment, varies with the throttle opening [delta] _TH, on the basis of the change in the output torque, and judging a driver's intention to accelerate. The output torque is torque transmitted from an engine ECU (Electric Control Unit) that controls the engine to a transmission ECU that controls the transmission.
When the driver accelerates the vehicle after a small turn at low speed, the rotational speed of the engine increases, so the output torque transmitted from the engine ECU to the transmission ECU increases. Here, as the driver's intention to accelerate is larger, the driver opens the throttle opening _{δTH more} rapidly, so the engine speed also increases rapidly, and the rate at which the output torque increases increases. Therefore, the greater the rate at which the output torque increases, the greater the driver's intention to accelerate. A restoring force for returning the steering handle 3 to the neutral position is obtained by assisting the steering wheel return based on the magnitude of the acceleration intention. Further, the greater the intention to accelerate, the smaller the damper compensation value I and the lower the viscosity of the steering system, thereby increasing the restoring force for returning the steering handle 3 to the neutral position.

FIG. 11 is an overall conceptual diagram of a four-wheel vehicle to which the steering system according to the third embodiment is applied. In the third embodiment, the steering control ECU 130 calculates the output torque T transmitted from the engine ECU (not shown) to the transmission ECU (not shown) based on the throttle opening δ _TH and the engine rotational speed Ne, and the calculated output The magnitude of the intention of acceleration is determined based on the magnitude of the change in the torque T. Therefore, the steering control ECU130 is connected via a throttle opening degree sensor _{S TH} and the rotation speed sensor _{S NE} and the signal line, the throttle opening _{[delta] TH} and the engine rotational speed Ne is inputted. Then, the engine rotational speed Ne of the rotational speed sensor _{S NE} and the throttle opening degree _{[delta] TH} of the throttle opening degree sensor _{S TH} is detected by detecting, it may be input to the steering control ECU 130.
In addition, about the structure equivalent to the structure of the steering system 100 concerning 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The engine rotation speed Ne and the output torque T input to a transmission ECU (not shown) have characteristics as shown in FIG. 12, for example. FIG. 12 is a graph showing the characteristics of the engine speed Ne and the output torque T when the throttle opening δ _TH is from 1/4 to 4/4 (fully open), and the solid line indicates that the throttle opening δ _TH is 1 /. characteristics when 4, broken line characteristic when the throttle opening _{[delta] TH} is 2/4, characteristics when the dashed line is the throttle opening _{[delta] TH} is 3/4, the two-dot chain line is the throttle opening _{[delta] TH} The characteristics when 4/4 (fully open) are shown.
When the engine E is, for example, the engine rotational speed Ne, such as idle is small, when setting the throttle opening [delta] _TH to 1/4, corresponding to the increase of the engine rotational speed Ne, the characteristic shown by the solid line The output torque T is calculated based on this.

Here, when the throttle opening δ _TH turns at a low speed of 1/4, for example, and the throttle opening δ _TH is opened to 2/4, the output torque T is indicated by a broken line from the characteristic indicated by the solid line in FIG. Calculated by moving to characteristics. At this time, the output torque T rapidly increases as shown in FIG. Even if the throttle opening δ _TH is opened from 1/4 to 2/4, for example, there is a time delay in the increase of the engine rotation speed Ne, so that the engine rotation speed Ne is substantially constant and is not illustrated. The output torque T calculated by the engine ECU will increase.
For example, when the throttle opening [delta] _TH is opened from 1/4 to 2/4 in FIG. 12, the transition from the characteristic curve indicated by the solid line characteristic curve indicated by the broken line. At this time, the engine rotational speed Ne does not change and is substantially the same, and therefore when the transition is made from the solid line to the broken line, the output torque T calculated by an engine ECU (not shown) increases. That is, the point A moves from the point A on the solid line to the point B on the broken line. Thus, to increase the output torque T from the output torque T _A at the point A to the output torque T _B at the point B. Then, the throttle opening [delta] _TH is larger the output torque T is increased. That is, as the output torque T increases, the throttle opening _δTH increases.

Since the driver increases the throttle opening δ _TH as the acceleration intention increases, it can be determined that the driver's intention to accelerate is larger as the increase rate of the output torque T calculated by an engine ECU (not shown) is larger. Therefore, in the third embodiment, the steering control ECU 130 (see FIG. 11) calculates the output torque T based on the throttle opening [delta] _TH and the engine rotational speed Ne, the magnitude of the rate of increase in the output torque T, It is characterized by determining the magnitude of the driver's acceleration intention. As described above, in the third embodiment, the rotational speed sensor S _NE (see FIG. 11) for detecting the engine rotational speed Ne, the throttle opening sensor S _TH (see FIG. 11) for detecting the throttle opening δ _TH , and the acceleration. The steering control ECU 130 that determines the size of the intention constitutes the acceleration intention detection means described in the claims.

Specifically, the steering control ECU 130 (see FIG. 11), based on the throttle opening [delta] _TH and the engine rotational speed Ne at the time of turning at low speed, to calculate the output torque T from the characteristics shown in FIG. 12. When the throttle opening [delta] _TH is changed again calculates the output torque T based on the throttle opening [delta] _TH after the change. At this time, the output torque T is increased, when it becomes T + [Delta] T, the steering control ECU130 calculates the assist amount A _H in consideration of the size of [Delta] T. As described above, the assist amount A _H is because it is proportional to the steering torque Ts, the [Delta] T, the parameters of the proportional constant of formula for calculating the assist amount A _H. Further, the vehicle speed V _S is added to the parameter, so that A _H = k _A (V _S , ΔT) × Ts. Then, since it is preferable to increase the assist amount A _H as [Delta] T is large, a proportional constant k _{A (V S,} ΔT) is a larger value as [Delta] T is large.

When the steering control ECU 130 (see FIG. 11) determines that the driver intends to accelerate when the vehicle V (see FIG. 11) makes a small turn at a low speed, as in the first embodiment, in response to the acceleration intention size, the auxiliary torque given a suitable restoring force to the steering wheel 3 (see FIG. 11) is calculated as the assist amount a _H. Then, when the steering handle 3 is being steered, auxiliary torque (assist amount A _H ) is added to the front wheel 1 (see FIG. 11) to increase the restoring force, and the steering handle 3 is returned to the neutral position. .

FIG. 13 is a flowchart illustrating steps for determining the magnitude of the acceleration intention based on the output torque calculated by the steering control ECU and setting a suitable restoring force. Hereinafter, with reference to FIG. 13, a step in which the steering control ECU 130 sets a suitable force based on the magnitude of the acceleration intention will be described (see FIGS. 1 to 12 as appropriate).
The control shown in FIG. 13, the vehicle speed V _S is slow (in this embodiment, 10 km / h or less), and has an steering wheel 3, right and left of one of the largest turning angle [delta] _MAX The start of the steering wheel return state returning to the neutral position, triggered by the detection of the return determination means, is equivalent to the flowchart shown in FIG. 6 in the first embodiment.

The steering control ECU 130 reads the throttle opening δ _TH input from the throttle opening sensor S _TH in order to detect the driver's intention to accelerate (step S41). Further, the steering control ECU 130 reads the engine rotational speed Ne input from the rotational speed sensor S _NE (step S42). Based on the characteristic curve shown in FIG. 12, the output torque T (T ₁ ) corresponding to the throttle opening _δTH and the engine rotational speed Ne is calculated (step S43).

Again, the steering control ECU 130 reads the throttle opening δ _TH input from the throttle opening sensor S _TH (step S44), and outputs the output torque T (T ₂ ) corresponding to the read throttle opening δ _TH as shown in FIG. (Step S45). At this time, it is assumed that the engine speed Ne is not increased and is the value read in step S42.

Then, the steering control ECU 130 calculates an increase amount ΔT (= T ₂ −T ₁ ) of the output torque T. When ΔT is less than a predetermined value (step S46 → No), the steering control ECU 130 indicates that the driver intends to accelerate. It is determined that there is not, and a normal assist amount _AH is set (step S52). Further, the steering control ECU 130 sets a normal damper compensation value I (step S53). If the steering handle 3 is in the neutral position (step S54 → Yes), the steering control ECU 130 ends the control, but if the steering handle 3 is not in the neutral position (step S54 → No), the steering control ECU 130 is Control is returned to step S41.

Here, although not a value predetermined value is limited in step S46, for example, as shown in FIG. 12, due to changes in static characteristics of the throttle opening [delta] _TH at the same engine rotational speed Ne, an increase in the output torque T It may be an amount (indicated by an arrow in the figure). For example, in the points A and B in FIG. _12, T B -T _A becomes a predetermined value.
Then, a predetermined value based on the engine rotational speed Ne and the throttle opening [delta] _TH, for example (not shown) provided in the steering control ECU130 storage device stores in advance in a storage device based on the engine rotational speed Ne and the throttle opening [delta] _TH Read from.
Or, from the engine speed Ne and the throttle opening _{[delta] TH,} a formula for calculating the predetermined value, keep incorporated into a program for driving the CPU (not shown) of the steering control ECU130, steering control ECU130, the engine rotational speed Ne And the throttle opening δ _TH may be calculated using a calculation formula.

  Returning to step S46, when the increase amount ΔT of the output torque T is greater than or equal to a predetermined value (step S46 → Yes), the steering control ECU 130 determines that the driver has an intention to accelerate, and the magnitude of the driver's intention to accelerate is determined. Is determined (step S47). As described above, it can be determined that the larger the increase amount ΔT of the output torque T is, the greater the acceleration intention is. That is, the steering control ECU 130 determines that the driver's intention to accelerate is larger as the increase amount ΔT of the output torque T is larger.

Then, the steering control ECU 130 sets a damper compensation value I based on the magnitude of the acceleration intention (step S48). That is, when the acceleration intention is large, the damper compensation value I is set small.
Although the method of setting the damper compensation value I corresponding to the increase amount ΔT of the output torque T is not limited, for example, the increase amount ΔT of the output torque T is divided by several threshold values and divided by the threshold values. For each range, a suitable damper compensation value I corresponding to the angular velocity ω of the electric motor 4 may be set and stored in a storage device (not shown) of the steering control ECU 130 as table format data. The steering control ECU 130 can set a suitable damper compensation value I by reading the damper compensation value I corresponding to the calculated increase amount ΔT of the output torque T and the angular velocity ω of the motor 4 from the data in the table format.

Further, the steering control ECU130 sets the assist amount _{A H,} based on the magnitude of the acceleration intention and the vehicle speed _{V S} (step S49).
Here, in step S49, the a method of setting the assist amount A _H, based on the magnitude of the acceleration intention and the vehicle speed V _S is not limited to, the acceleration intention to increase the size of ΔT of the output torque T size In addition, a method may be considered in which, together with the vehicle speed V _S , a parameter of a proportionality constant in a formula for calculating the assist amount A _H is considered.

As described above, the assist amount A _H is proportional to the steering torque Ts, the vehicle speed V _S, the [Delta] T, a method of the parameters of the proportional constant of formula for calculating the assist amount A _H is considered. Specifically, the proportionality constant k _A in the equation for calculating the assist amount A _H may be set to k _A (V _S , ΔT) using the vehicle speed V _S and the increase amount ΔT of the output torque T as parameters.

The method of setting the proportionality constant k _A (V _S , ΔT) in the equation for calculating the assist amount A _H corresponding to the increase amount ΔT of the vehicle speed V _S and the output torque T is not limited. _A method may be considered in which a suitable proportionality constant k _A (V _S , ΔT) for each vehicle speed V _{S is set} for each range divided by several threshold values.
The proportional constant k _A (V _S , ΔT) may be stored in a storage device (not shown) of the steering control ECU 130. The steering control ECU 130 reads out the proportional constant k _A (V _S , ΔT) corresponding to the vehicle speed V _S and the increase amount ΔT of the output torque T from a storage device (not shown), thereby obtaining the proportional constant k _A (V _S , ΔT) can be set.

Then, the steering control ECU130 is by integrating the proportional constant _k A _{(V S, ΔT)} and the steering torque Ts is set, can be calculated assist amount _{A H.}

Further, a calculation formula for calculating the proportional constant k _A (V _S , ΔT) from the vehicle speed V _S and the increase amount ΔT of the output torque T may be incorporated in a program for driving a CPU (not shown) of the steering control ECU 130. . The CPU (not shown) of the steering control ECU 130 calculates a proportional constant k _A (V _S , ΔT) using a calculation formula incorporated based on the vehicle speed V _S and the calculated increase amount ΔT of the output torque T. Can do.

Then, the steering control ECU 130 determines whether or not the steering handle 3 is in the neutral position, and if it is in the neutral position (step S50 → Yes), the control is terminated. When the steering handle 3 is not in the neutral position (step S50 → No), the steering control ECU 130 determines the magnitude of the acceleration intention, and when the acceleration intention changes (step S51 → Yes), the steering control ECU 130 Then, control returns to step S48. That is, the assist amount _AH and the damper compensation value I based on the changed acceleration intention are set. When the acceleration intention does not change (step S51 → No), the steering control ECU 130 returns the control to step S50.

Here, describing in detail the process in step S51, the steering control ECU130 reads the throttle opening _{[delta] TH,} calculates an output torque T corresponding to the throttle opening _{[delta] TH} read. The calculated output torque T that changes an output torque T calculated in step S45 (T _2), when the change amount from the output torque T (T ₂₎ calculated in step S45 is equal to or greater than a predetermined value, the steering control ECU 130 determines that the acceleration intention has changed.
Then, in order to set the assist amount _AH and the damper compensation value I corresponding to the changed acceleration intention, the control is returned to step S48.

As described above, in the third embodiment, the increase amount ΔT of the output torque T is based on the engine rotational speed Ne detected by the rotational speed sensor S _NE and the throttle opening δ _TH detected by the throttle opening sensor S _TH. The steering control ECU 130 determines that the driver's intention to accelerate is larger as ΔT is larger. Then, it is possible to provide the assist amount A _H, based on the acceleration intention of a magnitude determined in steering wheel 3. Furthermore, when the acceleration intention is large, the damper compensation value I is reduced to reduce the viscosity of the steering system, whereby a suitable restoring force of the steering handle 3 can be obtained. Then, the restoring force obtained by driving the electric motor 4 so as to obtain the assist amount A _H, based on the acceleration intention, that the steering wheel 3 can be returned to the neutral position, equivalent to the first embodiment Excellent effect.

In the third embodiment, for simplicity of explanation, the throttle opening [delta] _TH separated by 1/4 steps, it is not intended to be limited, such as 1 / 6,1 / 8, What is necessary is just to set suitably.

Here, when the increase amount ΔT (= T ₂ −T ₁ ) of the output torque T becomes negative in step S46 of FIG. 13, that is, when the output torque T decreases, the steering control ECU 130 determines that the driver The structure which determines with having a deceleration intention may be sufficient. In this case, the steering control ECU130 is to reduce the assist amount A _H, due to the excessive return of the steering wheel 3, a configuration for preventing unstable behavior of the vehicle V.

As described above, in the steering system according to the present invention, when the vehicle turns at a low speed, the steering control ECU increases the restoring force to return the steering handle to the neutral position, thereby moving the steering handle to the neutral position. It has an excellent effect of being able to return to
Further, the steering control ECU determines the magnitude of the driver's intention to accelerate, and when the intention to accelerate is large, the assisting force is increased and the damper compensation value is decreased to restore the steering handle to the neutral position. As a result, the steering handle can be reliably returned to the neutral position.

1 is an overall conceptual diagram of a four-wheel vehicle including a steering system according to an embodiment of the present invention. It is a block diagram of the electric power steering apparatus of a steering system. It is a steering control ECU schematic control function block diagram of a steering system. It is a figure which shows the characteristic of a throttle opening and a vehicle speed. (A) is a graph showing the relationship between the steering torque, the assist amount, and the magnitude of the acceleration intention, and (b) is a graph showing the relationship between the angular velocity of the motor, the damper compensation value, and the magnitude of the acceleration intention. It is a flowchart which shows the step which determines the magnitude | size of the intention of acceleration with a vehicle speed, and sets suitable restoring force. It is a graph which shows the relationship between a steering restoring force, the steering angle of a steering handle, and a vehicle speed. It is a whole conceptual diagram of a four-wheel vehicle to which a steering system according to a second embodiment is applied. It is a graph which shows the static characteristic of an intake negative pressure and an engine speed. It is a flowchart which shows the step which determines the magnitude | size of the intention of acceleration with a negative pressure characteristic, and sets suitable restoring force. It is a whole conceptual diagram of a four-wheel vehicle to which a steering system according to a third embodiment is applied. 5 is a graph showing characteristics of engine rotation speed Ne and output torque T for each throttle opening. It is a flowchart which shows the step which determines the magnitude | size of the intention of acceleration with an output torque, and sets a suitable restoring force.

Explanation of symbols

1 (1L, 1R) Front wheel 2 (2L, 2R) Rear wheel 3 Steering handle 4 Electric motor 25 Resolver (return determination means)
52 Damper Compensation Signal Calculation Unit (Damping Control Unit)
DESCRIPTION OF SYMBOLS 100 Steering system 110 Electric power steering apparatus 130 Steering control ECU (steering control apparatus, acceleration intention detection means)
130a Electric power steering control unit S _TH throttle opening sensor (acceleration intention detection means)
_ST torque sensor (return determination means)
_SV vehicle speed sensor (vehicle speed detection means, acceleration intention detection means)
S _NE rotation speed sensor (acceleration intention detection means)
_SPB pressure sensor (acceleration intention detection means)
S _TH throttle opening sensor (acceleration intention detection means)

Claims (3)

An electric power steering device that generates an auxiliary torque according to at least the steering torque, and transmits the auxiliary torque to the steering system of the front wheels;
A steering control device for controlling the electric power steering device;
A return determination means for detecting a steering wheel return state in which a steering handle provided in the steering system returns to a neutral position;
Vehicle speed detection means for detecting the vehicle speed of the vehicle comprising the electric power steering device;
In a steering system configured to include acceleration intention detection means for detecting the presence and size of an acceleration intention, which is the strength of a driver's intention to accelerate the vehicle,
When the driver operates the steering handle to turn the vehicle and the return determination means detects the steering wheel return state, the vehicle speed is low, and the acceleration intention detection means When an acceleration intention is detected,
The steering control device includes:
The steering system characterized by increasing the restoring force to return the steering handle to the neutral position as the magnitude of the acceleration intention detected by the acceleration intention detection means is larger. The steering control device includes:
The steering system according to claim 1, wherein the restoring force is obtained by driving the electric motor in a direction in which the steering handle is returned to a neutral position. The steering control device includes:
A damping control unit that calculates a damper compensation value that increases or decreases the magnitude of the viscosity of the electric power steering device;
When the driver operates the steering handle to turn the vehicle and the return determination means detects the steering wheel return state, the vehicle speed is low, and the acceleration intention detection means When an acceleration intention is detected,
The damping control unit
The steering system according to claim 1 or 2, wherein the damper compensation value is calculated to be smaller as the magnitude of the acceleration intention detected by the acceleration intention detection means is larger.

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