JP2009179230A - Steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering system capable of suppressing uncomfortable feeling generated accompanied by the lack of a driving force of a vehicle during turning. <P>SOLUTION: A steering control ECU 130 is equipped with a correction determination part 70, and detects the lack of the driving force by detecting a gear change of a transmission 11. The steering control ECU 130 corrects so that a base signal D<SB>T</SB>is reduced by calculating a base correction gain D<SB>G</SB>to be integrated to the base signal D<SB>T</SB>when detecting the lack of the driving force during the turning of a vehicle, and corrects so that a damper compensation value I is increased by calculating a damper correction gain I<SB>G</SB>to integrate it to the damper compensation value I, and reduces auxiliary torque generated by a motor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steering system including an electric force applying means for assisting steering of a vehicle.

  The vehicle steering system includes an electric force applying means for generating an auxiliary torque corresponding to the magnitude of the steering torque by the electric motor and transmitting the auxiliary torque to the steering system to reduce the steering force that the driver steers. Become. In such an electric force applying means, a base signal determined by the steering torque and the vehicle speed is compensated by inertia (inertia) and damping (viscosity) of the steering system, and the electric motor is controlled using the compensated signal as a target current.

Conventionally, each characteristic of damping, inertia, and base signal in the electric force applying means is calculated using an inertia table having a base table, a damper table, and a substantially differential characteristic.
Here, a method for setting each table, which is a function of the steering torque, the vehicle speed, and the motor angular velocity, will be considered. The base table lowers the gain as the vehicle speed increases, increases the dead zone, increases the manual steering area to provide the driver with road surface information, and provides a solid steering torque response as the vehicle speed increases. In the middle and low vehicle speed range, it is necessary to improve the response delay of the steering due to the inertia and viscosity of the electric motor to provide a clean steering feeling in the middle and low vehicle speed range.

  In the damping control, the road surface reaction force decreases during high-speed traveling, so that the movement of the electric motor at a high rotational speed is suppressed and controlled to give a sense of stability to the steering feeling. For this purpose, the damping control performs a correction for attenuating or amplifying the target current with a compensation value corresponding to the damping gain.

In the electric power applying means configured as described above, in order to further improve the steering feeling for the driver of the vehicle, for example, in Patent Document 1, corresponding to the shift position (traveling range) of the automatic transmission, A technique for changing characteristics of a target current of an electric motor that drives an electric force applying means is disclosed.
Japanese Unexamined Patent Publication No. 08-216901 (see paragraphs 0020 to 0022)

However, for example, when the automatic transmission performs a gear change during turning of the vehicle, transmission of engine torque to the driving wheels is interrupted, so that driving force of the driving wheels disappears, so-called driving force loss occurs.
When the driving force is lost, the road surface reaction force against the steered wheels is reduced, the moment around the kingpin is reduced, and the driver feels that the steering wheel is missing.
For example, the technique disclosed in Patent Document 1 has a problem that it is not possible to reduce a sense of incongruity such as a feeling of falling out of the steering wheel that occurs when the driving force of the vehicle during turning is lost.

  Therefore, an object of the present invention is to provide a steering system that can reduce a sense of incongruity that occurs when the driving force of a vehicle that is turning is lost.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a vehicle steering system including a turning detection means for detecting turning, and transmits auxiliary torque generated by the electric motor to the steering system of the steered wheels. An electric force applying means that calculates the auxiliary torque, a steering control means that calculates a control signal for controlling the electric motor so as to generate the auxiliary torque, and a drive wheel from the engine of the vehicle via the transmission. Driving force cut-off detecting means for detecting that the driving force transmitted to the vehicle is cut off, and drive transmitted to the drive wheels when the turning detection means detects that the vehicle is turning. Correction means for correcting the control signal so that the auxiliary torque generated by the electric motor is reduced when the driving force cutoff detecting means detects that the force is cut off. It was characterized in that.

  According to the first aspect of the present invention, the steering control means can detect turning of the vehicle and interruption of the driving force transmitted from the engine to the driving wheel, and the engine is driven from the engine when the vehicle is turning. When the driving force transmitted to the wheel is interrupted, the control signal can be corrected so that the auxiliary torque generated by the electric motor is reduced.

  According to a second aspect of the present invention, the steering control unit includes a base signal calculation unit that calculates a base signal serving as a reference for the control signal, and a damper that calculates a damper compensation value based on the rotation speed of the operation element. A compensation signal calculating unit, calculating the control signal by compensating so as to subtract the damper compensation value from the base signal, and the correction means detects that the vehicle is turning. When the driving force cutoff detecting means detects that the driving force transmitted to the driving wheel is cut off, and / or corrects the base signal to decrease, and / or The auxiliary torque is reduced by correcting the damper compensation value to be increased.

  According to the second aspect of the present invention, when the vehicle is turning, when the driving force transmitted from the engine to the driving wheel is interrupted, the damper compensation value calculated based on the rotation speed of the operating element is increased. Thus, the auxiliary torque can be reduced by reducing the base signal serving as a reference for the control signal.

  According to a third aspect of the present invention, the transmission includes a transmission ratio detection unit that detects a transmission ratio set by the transmission and notifies the correction unit of the detected transmission ratio. The means is such that the larger the gear ratio detected by the gear ratio detecting means when the driving force cutoff detecting means detects that the driving force transmitted to the driving wheel is interrupted, the greater the ratio of the base signal. The correction amount and / or the correction amount of the damper compensation value is increased.

  According to the invention of claim 3, when the driving force cutoff detecting means detects that the driving force transmitted to the driving wheel is cut off, the larger the gear ratio detected by the gear ratio detecting means, The auxiliary torque can be reduced by largely correcting the base signal and / or the damper compensation value.

  According to a fourth aspect of the present invention, the engine includes engine torque detection means for detecting engine torque and notifying the correction means of the detected engine torque, and the correction means includes the engine torque detection means. The correction amount of the base signal and / or the correction amount of the damper compensation value is increased as the engine torque of the engine detected by is increased.

  According to the fourth aspect of the present invention, the auxiliary torque can be reduced by correcting the base signal and / or the damper compensation value larger as the engine torque is larger.

  ADVANTAGE OF THE INVENTION According to this invention, the steering system which can reduce the discomfort which generate | occur | produces with the driving force omission of the vehicle in turning can be provided.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 is an overall conceptual diagram of a four-wheel vehicle to which a steering system according to the present embodiment is applied, and FIG.

As shown in FIG. 1, the steering system 100 according to the present embodiment includes an electric force applying unit 110 that assists the steering by the steering handle 3 that steers the front wheels 1 (1L, 1R), which are steered wheels, with an electric motor 4. A steering control ECU (steering control means) 130 for controlling the electric force applying means 110 is included.
Further, the vehicle V is provided with rear wheels 2 (2R, 2L).

As shown in FIG. 2, the electric force applying means 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 force applying means 110 can change the traveling direction of the vehicle V (see FIG. 1) when the steering handle 3 is operated.
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.

The electric force applying means 110 includes an electric motor 4 that applies an auxiliary steering force (auxiliary torque) for reducing the steering force by the steering handle 3 as an electric force, and is provided on the output shaft of the electric motor 4. The worm gear 5 a meshes with a worm wheel gear 5 b provided on the pinion shaft 7.
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 in accordance with the vehicle speed V _S , a light and stable steering torque response feeling is imparted lightly at low speed traveling and at 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 applying unit 110 includes a motor drive circuit 23 for driving the electric motor 4, a resolver 25, a torque sensor S _T for detecting 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 (vehicle speed) of the vehicle V (see FIG. 1).
The steering control ECU 130 of the steering system 100 (see FIG. 1) includes an electric force applying means control unit 130a (see FIG. 3) which will be described later for driving and controlling the electric motor 4 that is a functional part of the electric force applying means 110. Yes.

The electric motor drive circuit 23 includes a plurality of switching elements such as a three-phase FET bridge circuit, for example, and uses a DUTY (DU, DV, DW) signal from the electric force applying means control unit 130a (see FIG. 3). A rectangular 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 _m (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.

  The steering angle sensor 26 is a sensor that detects the turning angle of the front wheel 1, and is constituted by, for example, a rack position sensor that detects an operation amount of the rack shaft 8. The steering angle sensor 26 is connected to the steering control ECU 130 via a signal line, and inputs the operation amount of the rack shaft 8 to the steering control ECU 130 as a detection signal.

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 vehicle V according to this embodiment is interposed between the engine 10 and the front wheel 1 that is a driving wheel, and transmits the driving force of the engine 10 to the front wheel 1. A transmission 11 configured as a transmission and a transmission control device 11 a for controlling the transmission 11 are provided.
Furthermore, the engine 10 includes an engine torque sensor 10a (engine torque detection means) that detects engine torque.
FIG. 1 illustrates a front engine front wheel drive (FF) vehicle. In the case of a front engine rear wheel drive (FR) vehicle, the rear wheel 2 is a drive wheel, and the transmission 11 is a driving force of the engine 10. Is transmitted to the rear wheel 2.

The transmission control device 11a is connected to the steering control ECU 130 through a signal line. For example, a gear position sensor (not shown) provided in the transmission 11 detects a gear position selected by the transmission 11 and converts it into an electrical signal or the like. It has a function of inputting to the steering control ECU 130.
Since the gear position selected by the transmission 11 has a gear ratio set for each gear position, the transmission 11 sets the gear ratio by selecting the gear position. Then, the transmission control device 11 a that detects the gear position selected by the transmission 11 detects the gear ratio set by the transmission 11. Further, the transmission control device 11a inputs an electric signal obtained by converting the detected gear ratio to the steering control ECU 130, thereby notifying the steering control ECU 130 of the gear position (speed ratio).

Further, the transmission control device 11a has a function of detecting that the transmission 11 is undergoing a gear change and inputting it to the steering control ECU 130 as a shift signal such as an electric signal.
Thus, by providing the transmission control device 11a, the steering control ECU 130 according to the present embodiment can detect the gear position selected by the transmission 11, and also detects that the transmission 11 is undergoing a gear change. it can.

  When the transmission 11 is undergoing a gear change, the transmission 11 cannot transmit the driving force generated by the engine 10 to the front wheels 1. That is, the driving force transmitted from the engine 10 to the front wheels 1 via the transmission 11 is cut off by the transmission 11 during the gear change. Therefore, the steering control ECU 130 can detect that the driving force transmitted from the engine 10 to the front wheels 1 is interrupted by detecting that the transmission 11 is changing gears.

  The engine torque sensor 10a is connected to the steering control ECU 130 through a signal line, converts the engine torque of the engine 10 into a signal such as an electric signal, and inputs (notifies) the steering control ECU 130.

  Next, functions of the steering control ECU will be described with reference to FIGS. 3 is a schematic configuration diagram of the steering control ECU of the steering system, FIG. 4A is a graph showing a characteristic function of a base signal stored in the base table, and FIG. 3B is a characteristic function of the damper table. It is a graph.

The steering control ECU 130 includes a microcomputer (not shown), a microcomputer (ROM) including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and is controlled by a program stored in the ROM, for example. The
As shown in FIG. 3, the steering control ECU 130 includes an electric force applying means control unit 130 a that controls the electric force applying means 110 (see FIG. 2) and a correction determination unit 70.
The electric force applying means control unit 130a and the correction determination unit 70 can be configured by, for example, software logic incorporated in a program for controlling the steering control ECU 130, but are not limited thereto, and are configured by hardware logic. Also good.

(Electric force application means controller)
First, the electric force applying means controller 130a will be described with reference to FIG. 2 as appropriate with reference to FIG.
The electric force applying means 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). A PI 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 adders 61, 62, 64, 65 and the integrators 71, 72 will be described later.

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 calculation unit 67 differentiates the angle signal θ of the motor 4 output from the resolver 25 to generate an angular speed signal ω. The excitation current generator 59 generates a target signal for the excitation current of the electric motor 4, but can perform field-weakening control by making the D-axis current ID and the Q-axis current IQ substantially equal if necessary.

The base signal calculation unit 51 generates a base signal D _{T serving} as a reference for the output signal IM ₁ that is a target signal of the output torque T _M ^* from the torque signal T and the vehicle speed signal VS. This signal generation is obtained by referring to a base table 51a set in advance by experimental measurement or the like based on the torque signal T and the vehicle speed signal VS. The base table 51a may be set in advance by experimental measurement or the like, and may be incorporated as data in software logic constituting the base signal calculation unit 51, for example.
When the base signal calculation unit 51 is configured by hardware logic, for example, the base signal calculation unit 51 may be provided with a storage unit and stored in a table data format.

As shown in FIG. 4A, the base signal calculation unit 51 (see FIG. 3) is provided with a dead zone N1 in which the base signal _DT is set to zero when the value of the torque signal T is small. When the value of T becomes larger than the dead zone N1, it has a characteristic of increasing linearly with the gain G1. Further, the base signal calculation unit 51 has a characteristic that the output increases with the gain G2 at the value of the predetermined torque signal T, and the output is saturated when the value of the torque signal T further increases.
In general, since the load on the road surface (road reaction force) varies depending on the traveling speed, the vehicle has a gain 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. For this reason, the base signal calculation unit 51 sets the gain (G1, G2) to be low and the dead zone N1 to be large as the vehicle speed V _S (vehicle speed signal VS) increases and increases to increase the manual steering region. The road surface information is given to the driver. That is, a firm response feeling of the steering torque Ts is given as the vehicle speed V _S (vehicle speed signal VS) increases. 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 52 compensates for the viscosity of the steering system, and when the convergence of the steering system at the neutral point decreases when the vehicle V (see FIG. 1) travels at a high speed. The steering damper function is provided to compensate for this, and the steering damper function is realized by referring to the damper table 52a corresponding to the angular velocity ω. The damper table 52a may be set in advance by experimental measurement or the like, and may be incorporated as data in software logic constituting the damper compensation signal calculation unit 52, for example.
Further, when the damper compensation signal calculation unit 52 is configured by hardware logic, for example, the damper compensation signal calculation unit 52 may be provided with a storage unit and stored in a table data format.

As shown in FIG. 4B, the characteristic function of the damper table 52a indicates 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. Has increasing properties.
Further, the gain is increased as the value of the vehicle speed signal VS is higher, and the output torque T _M ^* of the electric motor 4 is attenuated 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 handle 3 to the neutral point can be improved and the traveling of the vehicle V (see FIG. 1) 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 base signal _DT calculated by the base signal calculator 51. That is, the steering control ECU 130 compensates so as to subtract the damper compensation value I from the base signal _DT .
The adder 62, the output signal and an addition to the output signal of the output signal and the inertia compensation signal computing part 53 of the adder 61 (control signal) it is an IM _1.

Here, subtracting the damper compensation value I from the base signal _DT (attenuation correction) means correcting in the direction opposite to the rotation direction of the electric motor 4.
Therefore, when the direction of the steering torque and the rotation direction of the electric motor 4 (see FIG. 1) are the same as during normal steering, subtraction is performed, but self-adjustment that occurs on the front wheel 1 (see FIG. 1) that is a steered wheel When the steering torque direction and the rotation direction of the motor 4 are opposite to each other such that the steering handle 3 (see FIG. 1) is returned to the neutral position by the lining torque (SAT), the addition is performed.
Further, when the steering handle 3 is moved due to a crosswind, a road step, or the like, addition is also performed.

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. The inertia table 53a may be set in advance by experimental measurement or the like, and may be incorporated as data in the software logic that constitutes the inertia compensation signal calculation unit 53, for example.
Further, when the inertia compensation signal calculation unit 53 is configured by hardware logic, for example, the inertia compensation signal calculation unit 53 may be provided with a storage unit and stored in a table data format.

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.
Further, practically sufficient steering feeling is imparted to vehicle characteristics such as FF cars, FR cars, RV (Recreation Vehicle) and sedans, and steering characteristics that vary depending on vehicle speed, road surface, and the like.

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.

(Correction judgment part)
The steering control ECU 130 according to this embodiment is configured so that the engine torque detected by the engine torque sensor 10a when the transmission 11 changes gear while the vehicle V (see FIG. 1) is turning, and the transmission control device 11a Based on the detected gear position selected by the transmission 11, a base correction gain D _G for correcting the base signal _DT calculated by the base signal calculation unit 51, and a damper compensation value calculated by the damper compensation signal calculation unit 52 It calculates the damper compensation gain I _G for correcting the I.
Therefore, the steering control ECU 130 includes a correction determination unit 70.

The correction determination unit 70 receives a signal from an engine torque sensor 10a included in the engine 10, receives an engine torque detection unit 70a that detects engine torque, and a signal from a transmission control device 11a included in the transmission 11, And a gear position detector 70b for detecting a gear position selected by the transmission 11.
As described above, since the transmission control device 11a has a function of generating a shift signal when the transmission 11 is undergoing a gear change, the gear position detection unit 70b indicates that the transmission 11 is undergoing a gear change. Can be detected.

  Thus, the gear position detection unit 70b provided in the correction determination unit 70 detects the gear position (speed ratio) selected by the transmission 11 based on the signal input from the transmission control device 11a. The gear position detection unit 70b and the transmission control device 11a serve as a gear ratio detection unit.

Further, the gear position detection unit 70b can detect that the transmission 11 is changing gears. As described above, the gear position detection unit 70b detects that the transmission 11 is changing gears. It can be detected that the driving force transmitted to 1 (see FIG. 1) is cut off. That is, the gear position detection unit 70b can detect that the driving force transmitted from the engine 10 to the front wheels 1 is interrupted based on the signal input from the transmission control device 11a.
Accordingly, the gear position detection unit 70b and the transmission control device 11a serve as a driving force cutoff detection unit described in the claims.

Furthermore, in order to detect turning of the vehicle V (see FIG. 1), the correction determination unit 70 includes a turning detection unit 70c.
An operation amount of the rack shaft 8 (see FIG. 2) output from the rudder angle sensor 26 is input as a detection signal to the turning detection unit 70c, and the turning detection unit 70c receives the front wheel 1 based on the operation amount of the rack shaft 8. Calculate the turning angle. Then, when the front wheel 1 is steered from the neutral position, it is detected that the vehicle V is turning.
From this, the steering angle sensor 26 and the turning detection unit 70c become turning detection means for detecting the turning of the vehicle V.
Note that the method for detecting the turning of the vehicle V is not limited.
For example, the vehicle V may include a yaw rate sensor (not shown) and detect the vehicle V's yaw rate to detect when the vehicle V is turning.
Of course, the structure which detects the turning of the vehicle V combining these may be sufficient.

The correction determination unit 70 corrects the base signal _DT based on the engine torque input to the engine torque detection unit 70a and the signal from the transmission control device 11a input to the gear position detection unit 70b. A correction gain calculation unit 70d that calculates a base correction gain D _G to be corrected and a damper correction gain I _G to correct the damper compensation value I is provided.

Steering control ECU130 includes a base correction gain _{D G} for correcting gain calculating unit 70d is operational, the base signal computing part 51 is integrated by integrator 72 to the base signal _{D T} for calculating to correct the base signal _{D T.} Further, the steering control ECU130 includes a damper compensation gain I _G the correction gain calculator 70d is computed, and integrated by integrator 71 to the damper compensation value I damper compensation signal computing part 52 computes, correct the damper compensation value I To do.
For example, by setting the base correction gain D _G to a value greater than 0 and 1 or less and the damper correction gain I _G to a value of 1 or more, the base signal D _T can be corrected to decrease, and the damper compensation value I Can be corrected to increase.
Accordingly, the correction determination unit 70 and the integrators 71 and 72 serve as correction means described in the claims, and correct the damper compensation value I so as to increase and correct the base signal _{DT so as} to decrease. it is, so that the assist torque motor 4 occurs decreases, correcting the output signal IM ₁ is a control signal.

In this embodiment, the base correction gain _DG is a value set in advance as a value unique to the vehicle V (see FIG. 1). For example, the engine correction torque (see FIG. 1) and the transmission 11 (see FIG. 1). It may be calculated as a value corresponding to the gear position (gear ratio) selected in FIG.
FIG. 5A is a graph showing an example of a function of engine torque, gear position, and base correction gain.
In (a) of FIG. 5, as a premise, the gear ratio set by the transmission 11 increases as the gear position selected by the transmission 11 approaches the first speed (hereinafter referred to as low gear). The closer the gear position selected by the transmission 11 is to the fifth speed (hereinafter referred to as high gear), the smaller the gear ratio set by the transmission 11 becomes.

In the present embodiment, as shown in FIG. 5 (a), the greater the engine torque, based correction gain D _G has a smaller properties.
Furthermore, for the same engine torque, as the gear position selected by the transmission 11 approaches the low gear, i.e., the larger the gear ratio set by the transmission 11, the base correction gain D _G has a smaller properties.

This is because as the engine torque of the engine 10 (see FIG. 3) is larger and the gear ratio set by the transmission 11 (see FIG. 3) is larger, the driving force of the front wheels 1 (see FIG. 1), which are the drive wheels, is increased. This is due to the increase in SAT.
During the turning of the vehicle V (see FIG. 1), the steering system that assists the steering against the SAT is assisted. Therefore, as the SAT increases, the auxiliary torque (assist amount) that the motor 4 (see FIG. 1) transmits to the steering system. ) Is increased.
For example, when driving force loss occurs and the SAT against the auxiliary torque becomes small, the auxiliary torque transmitted to the steering system becomes a steering wheel feeling and the driver feels uncomfortable.
Therefore, for example, when driving force loss occurs, the amount of decrease in SAT decreases as the engine torque increases and the gear ratio set by the transmission 11 increases (the gear position selected by the transmission 11 is closer to low gear). The feeling of falling out of the steering wheel that occurs as the SAT decreases increases.

Thus to reduce the strong handle missing feeling that occurs, reducing the base correction gain D _G larger the engine torque, and to reduce the higher base correction gain D _G speed ratio is large to be set in the transmission 11 The base signal _DT calculated by the base signal calculation unit 51 (see FIG. 3) is greatly corrected.
In other words, the engine 10 by increasing the reduction rate of more base correction gain D _G is large engine torque (see FIG. 1), to increase the correction amount of the base signal D _T. Furthermore, by increasing the reduction rate of more base correction gain D _G speed ratio is large to be set in the transmission 11, to increase the correction amount of the base signal D _T.
As described above, as the engine torque of the engine 10 (see FIG. 1) is larger and the gear ratio set by the transmission 11 is larger, the correction amount of the auxiliary torque generated by the electric motor 4 (see FIG. 1) is increased. , Effectively reduce the feeling of falling out of the handle.

Damper adjusting gain I _G, in the present embodiment, the preset values as values specific to the vehicle V (see FIG. 1), for example, and the engine torque of the engine 10 (see FIG. 1), the transmission 11 ( It is conceivable to calculate as a value corresponding to the gear position selected in FIG.
FIG. 5B is a graph showing an example of a function of engine torque, a gear position selected by the transmission, and a damper correction gain. Also in FIG. 5B, as a premise, as the gear position selected by the transmission 11 (see FIG. 1) approaches the first speed (low gear), the gear ratio set by the transmission 11 increases, The closer the gear position selected by the machine 11 is to the fifth speed (high gear), the smaller the gear ratio set by the transmission 11 becomes.

In the present embodiment, as shown in (b) of FIG. 5, the larger the engine torque, the damper compensation gain I _G has a larger characteristic.
Further, in the case of the same engine torque, the damper correction gain IG has a characteristic that the larger the gear position selected by the transmission 11 approaches the low gear, that is, the larger the gear ratio set by the transmission 11 is, the larger the damper correction gain _IG is.

Damper correction gain I _G is By having such characteristics, the correction amount of the larger engine torque damper compensation value I of the engine 10 (see FIG. 3) is increased, and set in the transmission 11 (see FIG. 3) The correction amount of the damper compensation value I increases as the gear ratio to be applied increases. In addition, it is possible to effectively reduce the feeling of falling out of the handle that occurs when the SAT becomes small.

Incidentally, as shown in FIG. 5 (a), a function of engine torque and a gear position and the base correction gain D _G, and is shown in (b) of FIG. 5, an engine torque and a gear position and the damper correction function gain I _G Is an example, and does not limit the characteristics of the base correction gain D _G and the damper correction gain I _G.

The base correction gain D _G and the damper correction gain I _G may have characteristics shown by a graph corresponding to the gear position selected by the transmission 11. For example, the transmission 11 having a gear position of 1st to 4th gears. If so, the characteristics may be composed of four graphs.
Further, the base correction gain D _G and the damper correction gain I _G may be constant values, and a suitable base correction gain D _G and a damper correction gain I depending on characteristics required for the vehicle V (see FIG. 1). _G may be set.

Correction gain calculator 70d (see FIG. 3) is the method of calculating the base correction gain D _G but not limited to, for example, and the engine torque of the engine 10 (see FIG. 1), the transmission 11 (Fig. 1 the base correction gain D _G corresponding to the gear position selected by reference), and create a base compensation gain table 70e (see FIG. 3) set by an experiment or the like in advance measurement, software logic to configure the correction determination section 70 Can be incorporated as data.
Further, when the correction determination unit 70 is configured by hardware logic, the correction determination unit 70 may be provided with a storage unit and stored in a table data format.

Similarly, the correction gain calculator 70d is, the damper compensation gain I but is not limited the method for calculating the _G, for example, and the engine torque of the engine 10 (see FIG. 1), the transmission 11 (see FIG. 1) the in damper compensation gain I _G which corresponds to the gear position selected, the data in the software logic to create a damper compensation gain table 70f (see FIG. 3) set by an experiment or the like in advance measurements, constituting the correction determination section 70 As long as it is built in.
Further, when the correction determination unit 70 is configured by hardware logic, the correction determination unit 70 may be provided with a storage unit and stored in a table data format.

  FIG. 6 is a flowchart showing steps in which the steering control ECU controls the electric force applying means so as to reduce the feeling of falling out of the steering wheel that occurs in the turning vehicle. With reference to FIG. 6, a step in which the steering control ECU 130 controls the electric force applying means 110 (see FIG. 1) so as to reduce the feeling of falling out of the steering wheel that occurs in the turning vehicle V (see FIG. 1) will be described ( As appropriate, see FIGS.

The steering control ECU 130 determines whether or not the vehicle V is turning by the turning detection unit 70c of the correction determination unit 70 (step S1). If the vehicle V is not turning (step S1 → No), no processing is performed. However, when the vehicle V is turning (step S1 → Yes), the control proceeds to step S2.
As described above, the steering control ECU 130 can determine whether or not the vehicle V is turning based on the operation amount of the rack shaft 8 input from the steering angle sensor 26 to the turning detection unit 70c.

When the vehicle V is turning (step S1 → Yes), the steering control ECU 130 does not perform processing unless the transmission 11 is in gear change (step S2 → No), but when the transmission 11 is in gear change. (Step S2 → Yes), the control proceeds to Step S3.
Since the shift signal is input from the transmission control device 11a to the gear position detection unit 70b of the correction determination unit 70 of the steering control ECU 130, the steering control ECU 130 is input to the gear position detection unit 70b of the correction determination unit 70. By detecting the shift signal, it can be determined that the transmission 11 is changing gears.

As described above, when the transmission 11 is undergoing a gear change, the transmission 11 cannot transmit the driving force generated by the engine 10 to the front wheels 1 and the driving force is lost. Therefore, the correction determination unit 70 determines that it is necessary to correct the base signal D _T and the damper compensation value I when the transmission 11 is undergoing a gear change. Therefore, when the transmission 11 is undergoing a gear change (step S2 → Yes), the steering control ECU 130 calculates the base correction gain D _G and the damper correction gain I _G by the correction determination unit 70 (step S3).

That is, the correction gain calculation unit 70d of the correction determination unit 70 refers to the base correction gain table 70e, the gear position selected by the transmission 11 before the gear change of the transmission 11, and the engine torque detection unit 70a. It calculates the base correction gain D _G corresponding to the engine torque input to.
Further, the correction determination unit 70 refers to the damper correction gain table 70f to determine the gear position selected by the transmission 11 before the transmission 11 changes gear and the engine torque input to the engine torque detection unit 70a. The corresponding damper correction gain _IG is calculated.

For this reason, the gear position detection unit 70b of the correction determination unit 70 detects the gear position selected by the transmission 11 before the transmission 11 changes gears by a signal input from the transmission control device 11a. It has a function to keep.
As a result, when the correction gain calculation unit 70d of the steering control ECU 130 detects that the driving force transmitted to the front wheels 1 is blocked by the gear change of the transmission 11, the gear position detection unit 70b detects it. As the transmission gear ratio is larger, the correction amount of the base signal _{DT and} the correction amount of the damper compensation value I can be increased.

Then, the steering control ECU130 corrects the base signal _{D T} in the correction determining unit 70 calculates the base correction gain _{D G,} to correct the damper compensation value I in the damper compensation gain _{I G} (step S4).
That is, the steering control ECU130 is based signal _{D T} of the base signal computing part 51 generates, integrates the base correction gain _{D G} in multiplier 72.
Further steering control ECU130 is a damper compensation value I damper compensation signal computing part 52 computes, integrates the damper compensation gain _{I G} in multiplier 71.

As described above, the step of controlling the electric force applying means 110 may be incorporated as a subroutine in a program for controlling the steering control ECU 13 and executed periodically (for example, at a predetermined time interval such as 100 msec).
In the step of controlling the electric force applying means 110, the execution order of step S1 and step S2 in FIG. 6 may be switched.

As described above, the steering system according to the present embodiment can reduce the feeling of wheel disengagement due to loss of driving force that occurs during gear change even when the transmission changes gears in a turning vehicle. It has an excellent effect of reducing the uncomfortable feeling that the driver learns.
Furthermore, it is possible to correct the auxiliary torque generated by the motor by calculating the correction gain corresponding to the magnitude of the engine torque and the gear position (transmission ratio) selected by the transmission, corresponding to the running state of the vehicle As a result, it is possible to achieve an excellent effect that the feeling of falling out of the steering wheel can be suitably reduced.

In the present embodiment, the damper compensation value I (see FIG. 3) is corrected with the damper correction gain I _G (see FIG. 3), and the base signal D _T (see FIG. 3) is corrected to the base correction gain D _G. Although the correction is performed at the same time (see FIG. 3), a configuration may be used in which at least one of these corrections is performed.
That is, when the vehicle V (see FIG. 1) is turning and the transmission 11 (see FIG. 1) is in gear change, the correction gain calculation unit 70d (see FIG. 3) corrects the damper compensation value I. calculates a damper compensation gain I _G, in the integrator 71 (see FIG. 3) may be configured to be integrated into the damper compensation value I.
Alternatively, when the vehicle V (see FIG. 1) is turning and the transmission 11 (see FIG. 1) is gear changing, the correction gain calculation unit 70d (see FIG. 3) should correct the base signal _DT. calculates the over scan correction gain D _G, multiplier 72 may be configured to be integrated to the base signal D _T (see FIG. 3).

In the above description, a vehicle including a transmission including an automatic transmission is taken as an example. However, the present embodiment is applied to a vehicle including a transmission including a manual transmission (hereinafter referred to as an MT vehicle). Can also be applied.
In the MT vehicle, when changing the gear of the transmission, the driver needs to depress the clutch pedal.
When the driver depresses the clutch pedal, the transmission of the engine torque to the drive wheels is interrupted and the driving force is lost.
Therefore, in the case of an MT vehicle, for example, a sensor that detects that the driver has depressed the clutch pedal, and the steering control ECU that controls the steering system of the MT vehicle detects that the clutch pedal has been depressed, The present embodiment can be applied to an MT vehicle by correcting the auxiliary torque generated by the electric motor.

  Furthermore, although the steering handle 3 (see FIG. 1) and the electric force applying means 110 (see FIG. 1) in which the steered wheel 1 (see FIG. 1) is mechanically connected are taken as an example, the steering handle 3 This embodiment can also be applied to a so-called steer-by-wire electric force application means in which the front wheel 1 is not mechanically connected.

  Further, the electric force applying means 110 (see FIG. 1) according to the present embodiment generates an auxiliary torque corresponding to the magnitude of the steering torque input to the steering handle 3 (see FIG. 1). This is not limited, and the electric force applying means that generates auxiliary torque corresponding to the difference between the steering angle of the steering wheel 3 and the turning angle (actual steering angle) of the front wheel 1 (see FIG. 1) that is a steered wheel. Also, the present embodiment can be applied.

  In the present embodiment, the engine torque is detected by the engine torque sensor 10a (see FIG. 1) provided in the engine 10 (see FIG. 1). However, the driving force of the engine 10 is applied to the front wheels 1 that are the drive wheels. The engine torque may be calculated based on the hydraulic pressure of a clutch mechanism (not shown) to be transmitted or a hydraulic pressure command value calculated by the steering control ECU 130, for example.

1 is an overall conceptual diagram of a four-wheel vehicle to which a steering system according to an embodiment is applied. It is a block diagram of an electric power provision means. It is a schematic block diagram of steering control ECU of a steering system. (A) is a graph showing the characteristic function of the base signal stored in the base table, and (b) is a graph showing the characteristic function of the damper table. (A) is a graph showing an example of a function of engine torque, gear position, and base correction gain; (b) is an example of a function of engine torque, gear position selected by the transmission, and damper correction gain; It is a graph to show. 4 is a flowchart showing steps in which the steering control ECU controls the electric force applying means so as to reduce a feeling of falling out of the steering wheel that occurs in a turning vehicle.

Explanation of symbols

1 (1L, 1R) Front wheel (drive wheel)
3 Steering handle 4 Electric motor (steering system)
5a Worm gear (steering system)
5b Worm wheel gear (steering system)
7 Pinion shaft (steering system)
8 Rack shaft (steering system)
8a Rack teeth (steering system)
9 Tie rod (steering system)
10 Engine 10a Engine torque sensor (engine torque detection means)
11 Transmission 11a Transmission control device (driving force cutoff detection means, transmission ratio detection means)
26 Rudder angle sensor (turn detection means)
51 Base signal calculation unit 52 Damper compensation signal calculation unit 70 Correction determination unit (correction means)
70a Engine torque detection unit 70b Gear position detection unit (driving force cutoff detection means, gear ratio detection means)
70c Turn detection unit (turn detection means)
70d Correction gain calculator 71, 72 Accumulator (correction means)
DESCRIPTION OF SYMBOLS 100 Steering system 110 Electric power provision means 130 Steering control ECU (steering control means)
D _T base signal D _G base correction gain I damper compensation value I _G damper compensation gain V vehicle

Claims (4)

A vehicle steering system comprising a turning detection means for detecting turning,
Electric force applying means for transmitting auxiliary torque generated by the electric motor to the steering system of the steered wheels;
Steering control means for calculating the auxiliary torque and calculating a control signal for controlling the electric motor so as to generate the auxiliary torque;
Driving force cutoff detection means for detecting that the driving force transmitted from the engine of the vehicle to the drive wheels via the transmission is cut off;
When the turning detection means detects that the vehicle is turning, when the driving force interruption detection means detects that the driving force transmitted to the drive wheel is interrupted, the electric motor And a correction means for correcting the control signal so that the auxiliary torque generated by the motor is reduced. The steering control means includes
A base signal calculation unit that calculates a base signal that serves as a reference for the control signal; and a damper compensation signal calculation unit that calculates a damper compensation value based on a rotation speed of the operation element, and the damper compensation from the base signal Compensate to subtract the value and calculate the control signal,
The correction means includes
When the turning detection means detects that the vehicle is turning, when the driving force cutoff detection means detects that the driving force transmitted to the driving wheel is cut off, the base The steering system according to claim 1, wherein the auxiliary torque is reduced by correcting the signal so as to decrease and / or correcting the signal so as to increase the damper compensation value. In the transmission,
A gear ratio detection unit that detects a gear ratio set by the transmission and notifies the correction unit of the detected gear ratio is provided.
The correction means includes
The larger the gear ratio detected by the gear ratio detecting means when the driving force cutoff detecting means detects that the driving force transmitted to the driving wheel is interrupted, the larger the correction amount of the base signal, 3. The steering system according to claim 2, wherein a correction amount of the damper compensation value is increased. The engine includes
Engine torque detecting means for detecting engine torque and notifying the detected engine torque to the correcting means is provided,
The correction means includes
3. The correction amount of the base signal and / or the correction amount of the damper compensation value is increased as the engine torque of the engine detected by the engine torque detection means is larger. 3. The steering system according to 3.

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