JP4853122B2 - Electric steering control device - Google Patents

Abstract

A steering control apparatus is provided for a vehicle having a steering wheel for steering its steered wheels, a power source for generating power, and drive shafts for transferring the power to the wheels, to be served as driving wheels of the vehicle, and a traction control device for controlling braking torque applied to the wheels. The apparatus comprises a detection device for detecting thebraking torque applied to the wheels, a calculation device for calculating a driving force difference between the wheels, on the basis of the detected braking torque, a power source state detection device for detecting an actuating state of the power source, and a control device provided for controlling steering torque created by the steering wheel, and applying torque steer reducing torque to the steering wheel. A desired value of the torque steer reducing torque is determined, on the basis of the driving force difference and the actuating state of the power source. And, the torque steer reducing torque is applied to the steering wheel, in accordance with the desired value of the torque steer reducing torque, to reduce the torque steer.

Description

  The present invention relates to an electric steering control device for a vehicle, and more particularly to an electric steering control device that reduces torque steer generated in a steering wheel.

  In general, in a steering apparatus for a vehicle in which the steering wheel is a drive wheel, a phenomenon in which the steering force or the holding force changes in accordance with a change in the driving force is called torque steer, and this torque steer is suppressed. It is hoped that. For example, in Patent Document 1 described later, the driving force (or braking force) is controlled independently for each of the left and right wheels (or distributed to the left and right wheels) to improve the maneuverability and stability of the vehicle. A vehicle equipped with the left and right wheel control system is disclosed. Specifically, the torque steer that turns the steering wheel from the steered wheel side when the left and right uneven driving force (or braking force) acts on the steered wheel (steered wheel) by the above control is suppressed. For the purpose of the above, when a difference occurs in the control value between the left and right wheels in the driving force or the braking force by the left and right wheel control capable of controlling the driving force or the braking force independently for the left and right wheels, the control value There has been proposed an electric power steering device that outputs a torque steer prevention auxiliary torque signal for turning a steered wheel in a direction to cancel torque steer generated by the difference, and controls the electric motor.

  Further, in Patent Document 2 described later, in Patent Document 1, torque steer suppression control is performed only when a difference occurs in the control value between the left and right wheels, that is, only when a rotation difference occurs between the left and right wheels. However, on a road surface with high frictional resistance, even if there is no rotational difference between the left and right wheels, or even when a small rotational difference has occurred, a device that solves this is considered to be torque steer. Has been proposed. That is, the engine torque is detected or estimated in order to cancel the torque steer by looking at the transmission torque difference between the left and right drive shafts where torque steer may occur rather than the rotation difference between the left and right drive wheels. There has been proposed a steering control device that obtains an estimated torque steer value by a storage circuit that stores a relationship between torque differences applied to the drive shafts, and cancels torque steer generated due to a difference in transmission torque between the left and right drive shafts. A driving force distribution device that distributes the driving force to the left and right wheels in a four-wheel drive vehicle or the like has been proposed as described in Patent Document 3 below in relation to a vehicle whose steering wheel is a driving wheel. Yes.

Japanese Patent Laid-Open No. 11-129927 JP 2005-170116 A JP-A-5-77653

  However, as in Patent Document 2 described above, it is still difficult to sufficiently reduce the torque steer only by compensating for the torque steer based on the relationship between the left and right drive shaft torque differences with respect to the engine torque.

  Here, the cause of torque steer is analyzed. Torque steer means that in a vehicle (front engine / front drive vehicle (so-called FF vehicle) or four-wheel drive vehicle) whose steering wheel is a driving wheel, the steering wheel is steered from the steering wheel side when the vehicle is accelerated. (Steering wheel steers the steering wheel). The causes of the torque steer are mainly “the bending angle of the constant velocity joint of the drive shaft” and “the difference in driving force between the left and right wheels when a kingpin offset is present”.

First, as (1), “torque steer by the bending angle of the constant velocity joint of the drive shaft” will be described. As shown in FIG. 12, when the constant velocity joint of the drive shaft has a bending angle θ, the drive torque transmitted by the drive shaft is Tdrv, as shown in FIG. A secondary couple moment Mz to be steered is generated.
Mz = Tdrv · tan (θ / 2) --- (1)

  FIG. 13 shows the correspondence between the front and the plane with respect to the portion including the steering device in the vehicle in which the steered wheels are drive wheels. That is, in FIG. 13, in a vehicle in which the engine EG and the transmission TR are arranged horizontally with respect to the vehicle traveling direction in order to ensure the space efficiency of the engine compartment, the drive shaft (also referred to as the drive shaft). The length and mounting arrangement of DS1 and DS2 are not symmetrical. Therefore, when the joint bend angle of the drive shaft connected to the drive wheel is different between the left and right wheels WH1, WH2, the moment (also referred to as turning torque) Mz for turning the wheel is equal to the left and right wheels WH1. , WH2, and a torque steer occurs in which the steered wheels steer the steering wheel SW during acceleration of the vehicle. Thus, the torque steer resulting from the bending angle of the constant velocity joint of the drive shaft is called steady torque steer.

  Next, as (2), “torque steer due to difference in driving force between right and left wheels when a kingpin offset exists” will be described. As shown in FIG. 13, the steered wheels (WH1, WH2) have kingpins KP1, KP2 so that they can be steered, and the position of the turning center point TC (intersection of the kingpin axis and the road surface). The position of the driving force application point DP does not match, and there is a kingpin offset KPo that is the distance between the two points (KPc in FIG. 13 represents the wheel center kingpin offset). When the kingpin offset KPo exists, during the acceleration of the vehicle in which the driving force acts on the wheels WH1 and WH2, torque (steering torque) for turning the wheel is generated, which is (driving force) × (kingpin offset). As required. If the driving force is the same between the left and right wheels WH1, WH2, this steering torque is offset and torque steer does not occur. However, if the driving forces of the left and right wheels WH1, WH2 are different, "Torque steer where the right wheels (left and right wheels) steer the steering wheel" occurs.

Furthermore, the following three cases can be considered as the case where the driving force differs between the left and right wheels as in (2) above.
(2-a) "Driving force difference due to drive shaft characteristics"
When there is a characteristic difference between the drive shafts DS1 and DS2, a transient (dynamic) difference occurs in torque transmission. Even if the drive shafts DS1 and DS2 have the same material and the same cross-sectional shape, the torsional rigidity of the drive shaft differs if their lengths are different. When the vehicle accelerates rapidly, the driving force of the wheel having a short drive shaft length and high torsional rigidity rises quickly with a slight delay. On the other hand, the driving force rises gently at the wheel having a long drive shaft length and low torsional rigidity. Therefore, there is a left-right difference in the transient driving force, and torque steer (referred to as transient torque steer) due to this occurs.

(2-b) “Driving force left / right difference by traction control”
When braking torque is applied to one wheel by traction control, the driving force of the other wheel corresponding to the braking torque increases. In particular, when the traction control is activated on a so-called μ-split road surface where the road surface friction coefficient is different between the left and right wheels, a large left-right difference in driving force is generated.

(2-c) “Driving force left / right difference by driving force distribution device”
Even when a driving force distribution device is provided between the left and right wheels, a left-right difference in driving force occurs. There are two types of driving force distribution devices, one based on electronic control and the other that mechanically limits differentials (for example, viscous coupling), which are disclosed in, for example, the above-mentioned Patent Document 3.

  The above (1) and (2) summarize the causes of torque steer generated during acceleration of the vehicle, and FIG. 14 shows the respective torque steer occurrence sites. FIG. 14 shows that torque steer is generated from each part of the vehicle by the above (1), (2-a), (2-b) and (2-c). Among these, (1) and (2-a) relate to torque steer generated by the arrangement and characteristics of the drive shaft (hereinafter referred to as drive shaft-induced torque steer), which is already determined as the characteristics of the vehicle. It occurs only in one direction with respect to the steering direction of the steering wheel. On the other hand, (2-c) relates to torque steer generated by the driving force distribution device (hereinafter referred to as driving force distribution-derived torque steer), and (2-b) represents torque steer generated by traction control (hereinafter, referred to as torque steer). Therefore, it occurs in any direction with respect to the steering direction of the steering wheel.

  When the driving force distribution-induced torque steer or the traction control-induced torque steer is generated, the vehicle is accelerating, and therefore, the drive shaft-induced torque steer is also generated. For this reason, when the steered direction in which the drive shaft-induced torque steer occurs and the steered direction in which the drive force distribution-induced torque steer or traction control-induced torque steer occurs are the same direction, the torque steer is mutually amplified. Become bigger. On the other hand, if the steered direction in which the drive shaft-induced torque steer occurs and the steered direction in which the driving force distribution-induced torque steer or traction control-induced torque steer occurs are opposite, the torque steer cancels each other out. Get smaller. Therefore, in order to perform torque steer reduction control that does not give the driver a sense of incongruity, it is important to compensate for the mutual influence between the torque steers generated by the above causes.

  Therefore, the present invention compensates for the influence of the drive shaft-induced torque steer when the driving force distribution-induced torque steer or traction control-induced torque steer occurs when the vehicle is accelerated in the electric steering control device. An object is to realize torque steer reduction control without any sense of incongruity.

To achieve the above object, according to the present invention, the steering wheel in the vehicle that transmits the power generated by the power source to the driving wheel via the drive shaft is the driving wheel. In the electric steering control device which is mounted on the vehicle and includes steering torque control means for controlling the steering torque of the steering wheel of the vehicle, and the steering torque control means reduces torque steer generated in the steering wheel. Driving force distribution detecting means for detecting the driving force distribution between the wheels, driving force difference calculating means for calculating the driving force difference based on the driving force distribution state detected by the driving force distribution detecting means, and the driving force difference calculation It means based on the driving force difference for calculating and reducing the torque steer occurring in any direction relative to the steering direction of the steering wheel A first target value determination means for determining a first torque steer reducing torque target value, a power source state detecting means for detecting an operating state of the power source, the power source detected by the animal power source state detecting means Driving force calculating means for calculating the driving force based on the operating state, and torque generated only in one direction with respect to the steering direction of the steering wheel based on the driving force calculated by the driving force calculating means According to the second target value determining means for determining the second torque steer reduction torque target value for reducing the steer , and the second torque steer reducing torque target value determined by the second target value determining means, Correction means for calculating a torque steer reduction torque target value by correcting the first torque steer reduction torque target value determined by the first target value determination means, and the torque steer low calculated by the correction means Based on torque target value, the steering torque control means is obtained by the fact that by applying a torque steer reducing torque reduces the torque steer. The power source state detection means includes a throttle opening sensor, an engine speed sensor, an electric motor current sensor, and the like.

Further, as described in claim 2, the steering wheel in the vehicle that transmits the power generated by the power source to the driving wheel via the drive shaft is mounted on the vehicle in which the steering wheel is the driving wheel. Traction control means for controlling the braking torque of the steered wheel in the electric steering control device comprising steering torque control means for controlling the steering torque of the wheel and reducing torque steer generated in the steering wheel by the steering torque control means Braking torque detecting means for detecting the braking torque, driving force difference calculating means for calculating a driving force difference between the steered wheels based on the braking torque detected by the braking torque detecting means, and the driving force difference based on the driving force difference calculating means for calculating, raw in any direction relative to the steering direction of the steering wheel The first target value determining means, a power source state detecting means for detecting an operating state of the power source, animal power source state detecting means for determining a first torque steer reducing torque target value for reducing the torque steer that Driving force calculating means for calculating a driving force based on the operating state of the power source detected by the driving force, and any one of the steering direction of the steering wheel based on the driving force calculated by the driving force calculating means. Second target value determining means for determining a second torque steer reducing torque target value for reducing torque steer generated only in the direction, and second torque steer reducing torque determined by the second target value determining means Correction means for correcting the first torque steer reduction torque target value determined by the first target value determination means in accordance with the target value and calculating the torque steer reduction torque target value. Based on the torque steer reducing torque target value stage for calculating the steering torque control means may be configured to reduce the torque steer by applying a torque steer reducing torque.

  Since this invention is comprised as mentioned above, there exist the following effects. That is, in the electric steering control device according to claim 1, in accordance with the second torque steer reduction torque target value, the first torque steer reduction torque target value is corrected to calculate the torque steer reduction torque target value. Since the torque steer is reduced by applying the torque steer reduction torque based on the torque steer reduction torque target value, for example, in the situation where the torque steer due to the driving force distribution occurs, the torque steer due to the drive shaft is generated. Thus, the torque steer reduction control can be realized without causing the driver to feel uncomfortable.

  According to the second aspect of the present invention, the first torque steer reduction torque target value for reducing the driving force distribution-induced torque steer and the traction control-induced torque steer is used as the second torque steer reduction torque target value. By correcting the torque steer, it is possible to calculate a torque steer reduction torque with no excess or deficiency, and to effectively reduce the torque steer generated during acceleration of the vehicle without feeling uncomfortable for the driver.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an electric steering control device according to an embodiment of the present invention, which is mounted on, for example, the vehicle shown in FIG. That is, it is mounted on a vehicle that transmits the power generated by the engine EG as a power source to the wheels WHfr and WHfl as drive wheels via the transmission TR and the drive shafts DSfl and DSfr. The wheels WHfr and WHfl are It is also a steered wheel steered by the operation of the wheel SW. This electric steering control device includes a steering torque control means, and a steering torque Ts of the steering wheel SW is detected by a steering torque detection means M1 shown in FIG. 1, and based on the detection result, a power steering auxiliary torque target value determination means. In M2, a target value of torque used as auxiliary torque for power steering control in order to reduce the driver's steering force is calculated and output as an auxiliary torque target value Tps.

  Then, the driving force distribution detecting means M3 detects the distribution state Dst of the driving force to the left and right driving wheels, and based on this driving force distribution state Dst, the driving force difference ΔFd between the driving wheels is calculated as the driving force difference calculating means M4. Is operated on. Here, in the case of traction control, the driving force distribution detecting means M3 detects braking torque applied to the driving wheel. Therefore, the means for detecting or estimating the brake fluid pressure can be the driving force distribution detecting means M3. In the differential limiting device, the driving force distribution state can be detected by detecting the differential state. Therefore, the wheel speed sensors (WSfr and WSfl in FIG. 2) for detecting the wheel speed of the driving wheel can be used as the driving force distribution detecting means M3. Further, when an electronic driving force distribution device is provided, a means for obtaining a control target value of an electronic control unit ECU 5 (shown by a broken line in FIG. 2) for controlling the electronic driving force distribution device is defined as a driving force distribution detection means M3. Can do. Based on the driving force difference ΔFd calculated by the driving force difference calculating means M4, the first torque steer reducing torque target value determining means M5 reduces the aforementioned driving force distribution-induced torque steer and traction control-induced torque steer. The first torque steer reduction torque target value Tts1 is calculated.

  Further, as shown in FIG. 1, a power source state detecting means M6 is provided, and thereby an output Te representing the operating state of the power source is detected. As the power source of the present invention, known means for generating a driving force for driving the wheels can be used. For example, in addition to an internal combustion engine such as a gasoline engine (EG in FIG. 2) and a diesel engine, an electric motor, Furthermore, it is possible to use an apparatus (hybrid system) that combines these. Therefore, the power source state detection means M6 is a means for detecting information such as the throttle opening, the fuel injection amount, the engine speed, etc. in the internal combustion engine, and a means for detecting the drive current and drive voltage in the electric motor. Furthermore, a detection means can be provided directly on the output shaft of the power source.

Furthermore, transmission state detection means M7 is provided, and the transmission gear ratio Rt of the transmission TR in FIG. 2 is detected as the transmission state of the transmission. Then, in the driving force calculating means M8, a driving force (also referred to as driving torque) Fd transmitted by the drive shaft is calculated based on the power source output Te and the gear ratio Rt. Based on this driving force Fd, the second torque steer reduction torque target value determining means M9 determines the second torque steer reduction torque target value Tts2. The second torque steer reduction torque target value Tts2 is for reducing drive shaft-induced torque steer caused by the arrangement and characteristics of the drive shaft. As described above, since the arrangement and characteristics of the drive shaft are known, the drive shaft-induced torque steer is always generated in the determined steering direction, and the second torque steer reduction torque target value Tts2 for reducing this is as follows. The calculation can be performed in relation to a predetermined driving force Fd.

  Then, the correction means M10 corrects the first torque steer reduction torque target value Tts1 according to the second torque steer reduction torque target value Tts2, and determines the torque steer reduction torque target value Tts. This torque steer reduction torque target value Tts is added to the auxiliary torque target value Tps for power steering control to be a new target value, and the electric motor MT is controlled by the motor drive control means M11 based on this target value.

  As described above, the first torque steer reduction target torque value Tts1 for reducing the driving force distribution-induced torque steer and traction control-induced torque steer generated in an arbitrary turning direction is generated only in the determined turning direction. Since it is compensated by the second torque steer reduction torque target value Tts2 for reducing the drive shaft-induced torque steer, it is possible to generate torque steer reduction torque with no excess or deficiency and to execute torque steer reduction control with certainty. In addition, a sense of discomfort to the driver is suppressed.

  The electric steering control device is mounted on the vehicle shown in FIG. 2 as described above, and the engine EG is disposed horizontally in the engine compartment together with the transmission TR. A differential device DF is disposed in the transmission TR, and the driving force generated by the engine EG is distributed to wheels WHfr and WHfl which are driving wheels and steering wheels. This differential device DF has a characteristic of equally distributing the driving force to the left and right driving wheels, but instead of this differential device DF, a differential that generates a driving force difference between the left and right wheels by differential limiting torque. A limiting device (not shown) may be used. In addition, an electronic driving force distribution device that more actively controls the driving force between the left and right driving wheels can be provided. In the electronic driving force distribution device, a driving force distribution target value between the left and right driving wheels is calculated based on the running state of the vehicle, for example, the vehicle speed and the turning state, and the driving force of the left and right driving wheels is calculated based on the target value. Be controlled.

  The vehicle includes an engine electronic control unit ECU 1 that controls the engine EG, a steering electronic control unit ECU 2 that controls the steering system, a transmission electronic control unit ECU 3 that controls the transmission, and a brake electronic control unit ECU 4 that controls the brake system. They are connected via a communication bus (in the case of those equipped with an electronic driving force distribution device, an electronic control unit ECU 5 for controlling this is further provided as indicated by a broken line). Through this communication bus, the sensor signal and the processing signal in each electronic control unit can be shared.

  The engine EG is provided with a throttle valve TH for controlling the engine output. The opening degree of the throttle valve TH is adjusted by a throttle actuator TA, and the throttle opening degree Tk is detected by a throttle opening degree sensor TK. An engine speed sensor EK that detects the engine speed Ek is also provided. The driver's acceleration request is detected as an accelerator pedal operation amount Ap by an accelerator pedal sensor AP provided in the accelerator pedal. Thus, the throttle actuator TA is controlled by the engine electronic control unit ECU1 based on the detected accelerator pedal operation amount Ap, the engine speed Ek, and the throttle opening degree Tk.

  As described above, in this embodiment, a vehicle using a gasoline engine (EG) as a power source is shown. However, as described above, a known power source for generating a driving force can be used. In addition to an internal combustion engine such as a diesel engine, it is also possible to use an electric vehicle (EV) that uses an electric motor, or a hybrid vehicle (HEV) that combines these.

  On the other hand, the steering system is configured to control the steering torque acting on the steering wheel SW based on the steering torque sensor TS provided on the steering shaft in order to reduce the steering force of the driver. Specifically, the steering electronic control unit ECU2 is configured to control the electric motor MT in accordance with the steering torque Ts detected by the steering torque sensor TS. Further, the electric motor MT can be controlled in consideration of the vehicle speed Vx. This control is so-called power steering control, and is also called electric power steering because the electric motor MT is used.

  Further, during the acceleration of the vehicle, a torque steer phenomenon occurs in which the wheels WHfr and WHfl try to steer the steering wheel SW. A torque steer reducing torque for reducing this phenomenon is also caused by the electric motor MT as will be described later. Is granted. Note that such control for reducing torque steer is referred to as torque steer reduction control.

  The transmission TR is provided with a gear position sensor GP for detecting a transmission ratio Rt, and the output transmission ratio Rt is supplied to the transmission electronic control unit ECU3. As the transmission TR, a known transmission such as a manual transmission (manual transmission), an automatic transmission (automatic transmission), a continuously variable transmission (CVT), or the like is used.

  The vehicle is provided with a brake control device BRK that includes traction control and controls the braking torque of each wheel, and a brake electronic control unit ECU 4 that controls the brake control device BRK is connected to a communication bus. A wheel speed sensor WSxx (where xx means each wheel, fr is a right front wheel, fl is a left front wheel, rr is a right rear wheel, and rl is a left rear wheel) is connected to the brake electronic control unit ECU4. Thus, the speed Vwxx of each wheel is calculated, and further, the vehicle speed Vx is calculated based on these detected wheel speeds. Thus, the brake electronic control unit ECU4 monitors the wheel speed Vwxx, and the traction control is executed when the acceleration slip of the drive wheel increases. That is, braking torque is applied to the drive wheel, and acceleration slip is suppressed.

  The operation of the electric steering control apparatus configured as described above will be described with reference to the flowchart shown in FIG. First, after initialization of control is performed in step 101, sensor signals and communication signals on the communication bus are read in step 102. Subsequently, in step 103, signal processing operations such as filter processing are performed. Next, at step 104, an auxiliary torque target value Tps used for power steering control is calculated based on the steering torque Ts. In step 105, a first torque steer reduction torque target value Tts1 for reducing driving force distribution-induced torque steer and traction control-induced torque steer is calculated. This will be described later with reference to FIG. In step 106, a second torque steer reduction torque target value Tts2 for reducing drive shaft-induced torque steer is calculated, which will be described later with reference to FIG.

  Further, in step 107, the first torque steer reduction torque target value Tts1 is corrected based on the second torque steer reduction torque target value Tts2, and the torque steer reduction torque target value Tts is calculated. In the present embodiment, the first torque steer reduction torque target value Tts1 is corrected by adding the second torque steer reduction torque target value Tts2. Thus, in step 108, the torque steering reduction torque target value Tts is added to the power steering assist torque target value Tps to obtain a new target value (Tps + Tts). Based on this target value, a current command for the electric motor MT is obtained. The value is calculated. In step 109, drive control of the electric motor MT is performed based on the current command value.

  The first torque steer reduction torque target value Tts1 for reducing the driving force distribution-induced torque steer and the traction control-induced torque steer is calculated according to the flowchart shown in FIG. First, in step 201, the driving force distribution state Dst detected by the driving force distribution detector M3 is read as a sensor signal or a communication signal. Next, in step 202, a driving force difference ΔFd between the left and right driving wheels is calculated based on the driving force distribution state Dst. The driving force distribution detection means M3, the driving force distribution state Dst, and the driving force difference calculation means M4 will be described later. In step 203, it is determined whether or not the first torque steer reduction control is being executed. Here, if it is determined that it is not being executed, the routine proceeds to step 204, where it is determined whether or not to start the first torque steer reduction control. On the other hand, if it is determined in step 204 that the start of the first torque steer reduction control is not necessary, the first torque steer reduction torque target value Tts1 is set to zero (0) in step 206. If it is determined in step 203 that the first torque steer reduction control is being executed, it is further determined in step 205 whether or not the same control is to be terminated. Here, if the end of the first torque steer reduction control is denied, the process proceeds to step 207, where the first torque steer reduction torque target value Tts1 is calculated, and if the first torque steer reduction control end condition is satisfied, step 206 The first torque steer reduction torque target value Tts1 is set to zero.

  The calculation of the first torque steer reduction torque target value Tts1 executed in step 207 is performed based on the driving force difference ΔFd calculated in step 202, as shown in FIG. The driving force difference ΔFd, that is, the torque steer due to the left / right difference in the driving force, is arbitrarily determined as to which wheel driving force increases, and as shown in FIG. 5, the steering wheel SW is bidirectional in the steering direction. May occur.

  Here, the driving force distribution detecting unit M3, the driving force distribution state Dst, and the driving force difference calculating unit M4 will be described. In order to reduce the traction control-induced torque steer, a hydraulic pressure sensor (indicated by PSxx in FIG. 2) attached to the wheel cylinder of each wheel can be used as the driving force distribution detection means M3. In other words, the hydraulic pressure sensor for calculating the braking torque by the traction control can be used as the driving force distribution detecting means M3. Further, the hydraulic pressure applied to the drive wheel by the traction control can be estimated from the driving state of the hydraulic control valve of the traction control device without using the hydraulic pressure sensor. Therefore, a known means for estimating the braking torque by the traction control can be used as the driving force distribution detecting means M3. Further, the braking torque by the traction control is controlled by a target value (such as a hydraulic pressure target value or a wheel slip target value) in the traction control calculated in the brake electronic control unit ECU4, so that a target value for the traction control is set. The means may be driving force distribution detecting means M3.

  When the traction control is activated, when braking torque is applied to one of the driving wheels, the driving force corresponding to the braking torque increases on the other driving wheel. Therefore, the braking torque applied by the traction control can be set to the driving force distribution state Dst. Thus, the driving force difference calculation means M4 calculates the driving force difference ΔFd based on the driving force distribution state Dst (braking torque).

  When a differential limiting device is used as the driving force distribution device, means for detecting the differential state of the differential limiting device can be used as the driving force distribution detection means M3. Since the differential limiting torque of the differential limiting device has a characteristic of moving from the fast rotating side to the slow rotating side, the wheel speed sensor VWxx of the left and right driving wheels is used as the driving force distribution detecting means M3, and the wheel speed is From the detection result of the sensor VWxx, the relative speed difference between the left and right driving wheels can be obtained as the driving force distribution state Dst. Thus, in the driving force difference calculating means M4, the differential limiting torque is calculated based on the relative speed difference between the left and right driving wheels, and the driving force left / right difference ΔFd is calculated.

  Further, when an electronically controlled driving force distribution device is provided, the driving force distribution detecting means M3 can be a means for setting a target value for driving force distribution. The electronically controlled driving force distribution device is controlled according to the running state of the vehicle, but the driving force between the left and right driving wheels is controlled by the driving force distribution target value of the device. Therefore, the means for setting the driving force distribution target value in the electronically controlled driving force distribution device is the driving force distribution detecting means M3, and further the driving force distribution target value is set as the driving force distribution state Dst to the driving force difference calculating means M4. Thus, the driving force difference ΔFd can be calculated from the driving force distribution target value.

  On the other hand, the second torque steer reduction torque target value Tts2 is calculated according to the flowchart shown in FIG. First, in step 301, the output Te of the engine EG that is a power source is calculated based on the sensor signal and the communication signal read in step 102 of FIG. This output Te is calculated, for example, in the relationship between the engine speed Ne and the throttle opening Tk as shown in FIG. Next, at step 302, the transmission gear ratio Rt is calculated based on the detection result of the gear position sensor GP of the transmission TR. In step 303, the driving force Fd transmitted through the drive shaft is calculated based on the power source output Te and the transmission gear ratio Rt. Further, in step 304, a driving force change dFd that is a time change of the driving force Fd is calculated.

  In step 305, it is determined whether the second torque steer reduction control is being executed. Here, if it is determined that it is not being executed, the routine proceeds to step 306, where it is determined whether or not to start the second torque steer reduction control. When it is determined that the second torque steer reduction control is started, the second torque steer reduction torque target value Tts2 is calculated in step 309, and the second torque steer reduction control is executed. On the other hand, if it is determined in step 306 that the second torque steer reduction control need not be started, the second torque steer reduction torque target value is set to zero (0) in step 308. If it is determined in step 305 that the second torque steer reduction control is being executed, it is further determined in step 307 whether or not to end the control. Here, if the end of the second torque steer reduction control is denied, the process proceeds to step 309, the second torque steer reduction torque target value Tts2 is calculated, and if the condition of the second torque steer reduction control end is satisfied, step 308 is performed. The second torque steer reduction torque target value Tts2 is set to zero.

The starting condition of the torque steer reduction control in step 306 is determined based on whether or not the driving force Fd is equal to or greater than a predetermined value Fd1. Further, the driving force change dFd can be considered, and the driving force Fd ≧ predetermined value Fd1 and the driving force change dFd ≧ predetermined value dFd1 may be set as the start conditions. Also, the start condition can be set based on a function of the driving force Fd and the driving force change dFd. Then, the calculation of the second torque steer reduction torque target value Tts2 executed in step 309 is performed based on the driving force Fd as shown in FIG. Furthermore, using the relationship shown in FIG. 9 , based on the driving force change dFd, the second torque steer reduction torque correction value Ttsh is calculated as the correction value of the second torque steer reduction torque target value Tts2, and this is calculated as the second torque steer reduction torque correction value Ttsh. The target value Tts2 can be corrected by adding the steering reduction torque target value Tts2.

  Furthermore, the second torque steer reduction torque correction value Ttsh indicates an example of a pulse waveform (rectangular wave, triangular wave, and trapezoidal wave) of a predetermined time as shown in FIG. 10 when the second torque steer reduction control is started. ). As shown in FIG. 11, the pulse waveform at the lowest stage includes an output time Tpls of the pulse waveform, an increasing gradient KTup of the second torque steer reduction torque correction value Ttsh, a maximum value Ttsm of the second torque steer reduction torque correction value Ttsh, At least one of the parameters of the maximum value holding time Thld and the decrease gradient KTdwn of the second torque steer reduction torque correction value Ttsh may be set according to the driving force Fd or the driving force change dFd. it can.

  As described above, the drive shaft-induced torque steer depending on the arrangement and characteristics of the drive shaft can grasp in advance the direction of the generated steering and the magnitude of the driving force. Accordingly, torque steer (traction control-induced torque steer, driving force distribution-derived torque steer) that is determined by the road surface condition and the traveling state of the vehicle and generated in an arbitrary turning direction is determined using the second torque steer reduction torque target value Tts2. By correcting the first torque steer reduction torque target value Tts1 to be reduced, the torque steer reduction torque without excess or deficiency can be calculated. Therefore, it is possible to effectively reduce the torque steer that the steered wheels try to steer the steering wheel, which occurs during acceleration of the vehicle, without feeling uncomfortable for the driver.

It is a block diagram which shows the structure of the electric steering control apparatus which concerns on one Embodiment of this invention. 1 is a configuration diagram illustrating an overall configuration of a vehicle including an electric steering control device according to an embodiment of the present invention. It is a flowchart which shows the example of steering control in one Embodiment of this invention. It is a flowchart which shows the example of a calculation process of the 1st torque steer reduction torque target value in one Embodiment of this invention. In one Embodiment of this invention, it is a graph which shows the example of a map used for the calculation of a 1st torque steer reduction torque target value. It is a flowchart which shows the example of a calculation process of the 2nd torque steer reduction torque target value in one Embodiment of this invention. It is a graph which shows the example of a map for setting the 2nd torque steer reduction control start condition in one embodiment of the present invention. In one Embodiment of this invention, it is a graph which shows an example of the map for setting a 2nd torque steer reduction torque target value. In one Embodiment of this invention, it is a graph which shows an example of the map for setting a 2nd torque steer reduction torque correction value. In one Embodiment of this invention, it is a graph which shows the example of a pulse waveform showing the 2nd torque steer reduction torque correction value. In one embodiment of the present invention, it is a graph which shows a setting parameter of a pulse waveform showing the 2nd torque steer reduction torque correction value. It is a perspective view which shows the relationship between the drive shaft and drive wheel in a common vehicle. FIG. 2 is a front view and a plan view of a portion including a steering device in a vehicle in which steering wheels are drive wheels. It is a block diagram which shows the generation | occurrence | production site | part of the torque steering which generate | occur | produces at the time of acceleration of a vehicle.

Explanation of symbols

M1 Steering torque detection means M2 Power steering assist torque target value determination means M3 Driving force distribution detection means M4 Driving force difference calculation means M5 First torque steer reduction torque target value determination means M6 Power source state detection means M7 Transmission state detection means M8 Driving force calculation means M9 Second torque steer reduction torque target value determination means M10 Correction means M11 Motor drive control means ECU1 Engine electronic control unit ECU2 Steering electronic control unit ECU3 Transmission electronic control unit ECU4 Brake electronic control unit BRK Brake control device SW Steering Wheel MT Electric motor EG Engine TR Transmission WHfr, WHfl Wheel AP Accelerator pedal sensor TS Steering torque sensor TK Throttle opening sensor

Claims (2)

Steering torque control means for controlling the steering torque of the steering wheel of the vehicle mounted on the vehicle in which the steering wheel in the vehicle that transmits the power generated by the power source to the driving wheel via the drive shaft is the driving wheel. In the electric steering control device that reduces torque steer generated in the steering wheel by the steering torque control means, a driving force distribution detection means for detecting a driving force distribution between the steered wheels, and the driving force distribution detection Driving force difference calculating means for calculating a driving force difference based on the driving force distribution state detected by the means, and based on the driving force difference calculated by the driving force difference calculating means with respect to the steering direction of the steering wheel. first target value determined for determining a first torque steer reducing torque target value for reducing the torque steer occurring in any direction Means, power source state detecting means for detecting the operating state of the power source, driving force calculating means for calculating a driving force based on the operating state of the power source detected by the power source state detecting means, and the driving A second torque steer reduction torque target value for reducing torque steer generated only in one direction with respect to the steering direction of the steering wheel is determined based on the driving force calculated by the force calculation means. 2 target value determination means and a first torque steer reduction torque target value determined by the first target value determination means in accordance with a second torque steer reduction torque target value determined by the second target value determination means Correction means for calculating a torque steer reduction torque target value by correcting the torque steer, and based on the torque steer reduction torque target value calculated by the correction means, the steering torque control means Electric steering control apparatus characterized by reducing the torque steer by applying a torque reduction. Steering torque control means for controlling the steering torque of the steering wheel of the vehicle mounted on the vehicle in which the steering wheel in the vehicle that transmits the power generated by the power source to the driving wheel via the drive shaft is the driving wheel. In the electric steering control device for reducing torque steer generated in the steering wheel by the steering torque control means, traction control means for controlling the braking torque of the steered wheel, and braking torque detection for detecting the braking torque A driving force difference calculating means for calculating a driving force difference between the steered wheels based on a braking torque detected by the braking torque detecting means, and a driving force difference calculated by the driving force difference calculating means. In order to reduce torque steer occurring in any direction with respect to the steering direction of the steering wheel A power source state detecting means for detecting a first target value determination means for determining a first torque steer reducing torque target value, the operation state of the power source, the operation of the power source detected by the animal power source state detecting means A driving force calculating means for calculating a driving force based on the state, and a torque steer generated only in one direction with respect to the steering direction of the steering wheel based on the driving force calculated by the driving force calculating means. The second target value determining means for determining the second torque steer reduction torque target value for reducing the torque , and the second torque steer reduction torque target value determined by the second target value determining means A correction means for calculating a torque steer reduction torque target value by correcting the first torque steer reduction torque target value determined by one target value determination means, and the torque steer reduction calculated by the correction means Based on torque target value, the steering torque control means an electric steering control device, wherein a reducing said torque steer by applying a torque steer reducing torque.

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