JP4300103B2 - Vehicle steering control device - Google Patents

Description

  The present invention relates to a vehicle steering control device that includes, for example, an assist mechanism that assists a steering force in accordance with a steering torque output from a steering mechanism by rotating a steering wheel of the vehicle.

  As this type of conventional vehicle steering control device, for example, the one described in Patent Document 1 below is known.

  In brief, the vehicle steering control device includes a driving / braking force left / right wheel difference signal input means for receiving a driving / braking force left / right wheel difference signal from the driving / braking force control unit, and its driving / braking force. Torque steer prevention auxiliary torque determining means for outputting an auxiliary torque signal for preventing torque steer based on the left and right wheel difference signal by the left and right wheel difference signal input signal is provided, and the auxiliary torque signal is used as an auxiliary in normal assist control. In addition to the steering torque signal, steering control is performed as a control signal for the electric motor.

As a result, the electric power steering device can cancel the moment generated around the kingpin due to the difference between the left and right wheels of the drive / braking force control signal, and the handle can be prevented from being removed without forming a complex suspension. An effect is produced.
Japanese Patent Laid-Open No. 11-129927

  However, in the conventional vehicle steering control device, the torque is generated only when a difference occurs in the control value between the left and right wheels, that is, only when the difference in rotation occurs by looking at the difference in rotation between the left and right wheels. It only controls the steering suppression.

  In addition, the torque steer suppression control in this conventional example is to prevent the steering wheel from being removed by generating an auxiliary reaction force torque in the electric power steering device based on the rotation difference signal between the left and right wheels as described above. is there.

  Further, in order to prevent malfunction in the torque steer suppression control, a dead zone is provided so that this control is not performed when the rotation difference signals of the left and right wheels are minute.

  Therefore, there is a risk of inviting the following technical problems.

  That is, the torque steer is also generated by an unbalance (difference) in drive transmission torque from the engine generated between the left and right wheels as drive wheels. This is likely to occur in a type in which a so-called engine is placed horizontally in an engine room. That is, in this horizontal installation type, the position of the transmission is shifted to the left or right in the vehicle body width direction in the engine room, so the lengths of the left and right drive shafts are different. For this reason, since the rigidity of the left and right drive shafts is different, a difference occurs in the torque transmitted from the engine from the both drive shafts to the left and right wheels.

  In this way, torque steer caused by problems due to engine layout in the engine room becomes prominent when the vehicle suddenly starts up or in a turbocharged engine with a large output torque. As the inward torque increases, the vehicle tries to turn to the longer side of the drive shaft.

  Such torque steer is different in the left and right directions on the drive shaft even when there is no rotational difference between the left and right wheels on the road surface with high frictional resistance, or even when a small rotational difference occurs. Torque is generated.

  As a result, the torque difference between the two drive shafts is transmitted to the driver via the steering shaft and the steering wheel, which may increase the driver's steering load and deteriorate the steering feeling.

  Such torque steer occurs even when there is no rotational difference between the left and right wheels as described above, or even a minute rotational difference. Therefore, as in the prior art, the left and right wheels rotate more than the dead zone. An apparatus that cannot be controlled without a difference cannot cope with the above technical problem.

  The present invention has been devised in view of the technical problem of the conventional vehicle steering control device. The invention according to claim 1 is, in particular, the actuator control means is detected by the left-right torque difference detection means. A control circuit is provided that drives and controls the actuator in a direction that cancels out torque steer generated by a transmission torque difference between the left and right drive shafts.

  Therefore, according to the present invention, the control circuit performs control so as to cancel the torque steer based on the transmission torque difference between the left and right drive shafts that may actually generate torque steer, not the rotational difference between the left and right drive wheels. Therefore, the generation of realistic and specific torque steer can be suppressed.

  According to a second aspect of the present invention, the left-right torque difference detection means stores a relationship between an engine torque detection circuit that detects or estimates engine torque and a torque difference applied to the left and right drive shafts with respect to the engine torque. And a memory circuit.

  According to the present invention, the torque applied to the left and right drive shafts only by collating the engine torque and the table map by configuring the storage circuit of the torque difference detecting means acting on the left and right drive shafts by, for example, a table map. The difference can be easily obtained, and it is not necessary to provide a special device for detecting the torque difference between the drive shafts. Therefore, an increase in cost can be suppressed.

  Embodiments of a vehicle steering control device according to the present invention will be described below in detail with reference to the drawings. The steering control device in this embodiment is applied to a front-wheel drive vehicle that is placed horizontally in an engine room.

  FIG. 1 shows an outline of a vehicle steering control apparatus according to this embodiment. The vehicle is provided with a steering shaft 2 to which a steering wheel 1 is connected and an output shaft 3 at the lower end of the steering shaft 2. A rack and pinion mechanism 4 that is a steering mechanism that applies steering torque to the left and right steered wheels FL and FR (drive wheels) to be transmitted, and a steering torque of the steering wheel 1 that is provided on the lower end side of the steering shaft 2 is detected. A torque sensor 5 that is an assist force detecting means, a hydraulic power cylinder 6 that is connected to the rack portion 4a of the rack and pinion mechanism 4 and is an assist mechanism that applies a steering assist force to the rack and pinion mechanism 4. A hydraulic circuit 7 that supplies and discharges operating hydraulic pressure to the hydraulic power cylinder 6, and an electric motor 8 that is an actuator that drives a later-described gear pump 9 included in the hydraulic circuit 7. Is composed mainly of the control unit 10 Metropolitan is an actuator control means for controlling the electric motor 8.

  Further, the driving force of the engine (not shown) is transmitted to the steered wheels FL and FR via the left and right drive shafts.

  The hydraulic power cylinder 6 includes an unillustrated piston that slides in the cylindrical cylinder portion 11 in the rack while the rack portion 4a passes through the cylindrical cylinder portion 11 extending in the vehicle body width direction. Is fixed. Also, in the cylindrical cylinder portion 11, left and right first hydraulic chambers and second hydraulic chambers are separated by the piston.

  The hydraulic circuit 7 has a pair of first and second passages 12 and 13 each having one end connected to each hydraulic chamber, and is capable of forward and reverse rotation connected to the other end of each of the passages 12 and 13. The gear pump 9 which is one reversible pump is provided.

  The electric motor 8 is driven to rotate in the forward and reverse directions by a control current output from the control unit 10, whereby the drive control of the gear pump 9 is performed, and the hydraulic control is performed by the drive control of the gear pump 9. The hydraulic pressure supplied to each hydraulic chamber of the power cylinder 6 is controlled, and steering assist control is performed according to the steering force and the steering direction by the steering wheel 1.

  As shown in FIGS. 1 and 2, the control unit 10 is configured to output a torque signal output from the torque sensor 5 that detects a torsion bar torque and a current vehicle speed signal from a vehicle speed sensor 15 that estimates a vehicle speed from a wheel speed. , The engine speed signal from the crank angle sensor 16, the throttle opening amount signal of the throttle valve from the throttle opening sensor 17, the gear shift position signal of the transmission from the gear position sensor 18, and the wheel speed sensor. A wheel speed signal from 19 and a steering angle signal from the steering angle sensor 20 are input.

  Further, a driving / braking force control unit 21 for controlling the driving force and the braking force for the driving wheels FL, FR is provided. This driving / braking force control unit 21 performs so-called traction control (TCS) for controlling the driving force of the engine to prevent slippage of the driving wheels FL and FR, for example, when the vehicle suddenly accelerates. In the driving / braking force control unit 21, a driving / braking force control unit 21a and a driving / braking force left / right wheel difference signal are output based on an output signal from the driving / braking force control unit 21a. Driving / braking force right / left wheel difference signal output means.

  Further, as shown in FIG. 2, the control unit 10 includes an auxiliary steering torque determination unit 22 that determines a normal required assist steering torque based on detection signals from the torque sensor 5 and the vehicle speed sensor 15, and The crank angle sensor 16, the throttle opening sensor 17, the gear position sensor 18, and the wheel speed sensor 19 are provided with a correction torque determination unit 23 that determines torque steer correction torque based on information signals.

  Further, based on the information signals from the decision units 22 and 23 and the on / off signal from the driving / braking force control unit 21a, that is, whether or not the slip prevention control of the driving wheels FL and FR is being performed. The target current value determining unit 24 that determines the target current value of the electric motor 8, the output current value determining unit 25 that determines the output current value to the electric motor 8, and the signal from the output current value determining unit 25 Based on this, the electric motor 8 is provided with a drive circuit 26 that outputs a drive current.

  Hereinafter, the steering assist control by the control unit 10 will be described based on the flowchart of FIG.

  First, in step 1, information signals from the torque sensor 5 and the vehicle speed sensor 15 are read.

  In step 2, the assist torque is obtained from the information signals of the sensors 5 and 15 using the table map of FIG. 4 showing the relationship between the torsion bar torque and the vehicle speed.

In step 3, now, it is determined whether preparative la transfected control by controlling the driving force of the engine described above (TCS) is being performed, if it is determined that not performed, the process proceeds to step 4.

  In step 4, a torque steer correction value is calculated. The correction value is determined by the torque steer correction torque determination unit 23 according to the method of the flowchart shown in FIG.

  More specifically, in step 11, information signals for obtaining the torque steer are read from the crank angle sensor 16, the throttle opening sensor 17, the gear position sensor 18, and the wheel speed sensor 19.

  Next, in step 12, an estimated engine torque value is obtained from the relative relationship between the engine speed and the accelerator opening (throttle opening) based on the table map shown in FIG.

  Next, in step 13, based on the table map shown in FIG. 7, the respective torque values (tire slip amounts) of both drive shafts are estimated based on the relationship between the engine torque estimated in step 12 and the gear position.

  Subsequently, in step 14, based on the table map shown in FIG. 8, the torque is determined depending on whether the estimated torque values of both drive shafts estimated in step 13 and the tire slip amounts of the drive wheels FL and FR are larger than a threshold value. Obtain an estimate of the steer.

  Next, in step 15, an assist correction value is obtained from the estimated value of torque steer obtained in step 14 based on the table map shown in FIG.

  Returning to the flowchart of FIG. 3, in step 5, it is determined whether a torque difference between the left and right drive shafts has occurred. If it is determined that a torque difference has occurred, the process proceeds to step 6.

  Here, a current command value to the electric motor 8 is calculated based on the assist torque and the torque steer correction value, and the process proceeds to step 7.

  In step 7, the current command value is output from the drive circuit 26 to the electric motor 8, and the process ends.

  If it is determined in step 3 that traction control (TCS) is being performed, the process proceeds to step 7 as it is without performing torque steer control in step 4 and subsequent steps in order to prevent control interference. Then, a predetermined current command value is output to the electric motor 8.

  Further, if it is determined in step 5 that there is no torque difference between the left and right drive shafts, it is not necessary to perform torque steer control, so that the routine proceeds to step 7 and a predetermined current command value is supplied to the electric motor 8. Output.

  As described above, according to this embodiment, the control circuit calculates the difference between the transmission torques of the left and right drive shafts FL, FR that may actually generate torque steer, not the rotation difference between the left and right drive wheels FL, FR. In view of this, since the control is made so as to cancel the torque steer, it is possible to suppress the occurrence of realistic and specific torque steer.

  As a result, an increase in the driver's steering load can be prevented, and deterioration of the steering feeling can be suppressed.

  In addition, since the assist torque, the estimated engine torque, the estimated drive shaft torque, the torque steer estimated value, the assist correction value, and the like are obtained by the table maps shown in FIGS. 4 and 6 to 9, the table map The torque difference applied to the left and right drive shafts can be easily obtained by simply checking the above, and it is not necessary to provide a special device for detecting the torque difference between the drive shafts. Therefore, an increase in cost can be suppressed.

  Note that the table maps shown in FIGS. 6 to 9 are created in advance by a vehicle running experiment or the like. That is, by estimating the engine torque, it is possible to estimate the magnitude of torque steer generated in the vehicle.

  Further, since the engine torque is estimated by three parameters of the engine speed signal from the crank angle sensor 16, the throttle opening amount by the throttle opening sensor 17 and the gear position sensor 18 of the transmission, the engine torque can be easily and highly accurately determined. Can be detected.

  Further, when the traction control (slip prevention control) is performed, the torque steer control is not performed, so that the controls do not interfere with each other, thereby preventing the vehicle behavior from becoming unstable. Can do.

  FIG. 10 shows a second embodiment of the present invention, which is constituted by electric power steering instead of a hydraulic power cylinder as an actuator of the assist mechanism.

That is, between the steering shaft 2 and the rack and pinion mechanism 4 , there are provided an assisting electric motor 30 and a reduction gear 31 that decelerates the rotation of the electric motor 30 and transmits it to the rack and pinion mechanism 4. Yes.

  The electric motor 30 is controlled by the control current output from the control unit 10 which is the same actuator control means as in the first embodiment, and the torque is controlled by the control flow based on FIGS. 3 and 5 described above. The occurrence of steer is suppressed.

  Therefore, this embodiment also has the same effect as the first embodiment.

The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below together with the effects thereof.
(1) The engine torque detection circuit detects or estimates an engine torque from information signals of at least a throttle opening of a throttle valve, a gear position of a transmission, and an engine speed. Vehicle steering control device.

According to the present invention, the engine torque is detected or estimated based on at least the above three parameters, so that the engine torque can be detected easily and with high accuracy.
(2) rotation difference detecting means for detecting or estimating a rotation difference between the left and right drive wheels;
A slip control means for preventing slip by controlling the torque transmitted to the drive wheel when the rotation difference detection means detects a rotation difference between the left and right drive wheels;
The actuator control means detects torque difference between the left and right drive wheels by the rotation difference detection means, and when torque control to the drive wheels is performed by the slip control means, torque control by the control circuit. The vehicle steering control device according to claim 2 , wherein the control is not performed.

  According to the present invention, since the slip control by the slip control means and the torque steer control by the control circuit do not interfere with each other, instability of the behavior of the vehicle can be prevented.

  The present invention is not limited to the configuration of each of the embodiments described above. For example, the application target vehicles include the following.

  In other words, there is an intermediate shaft that uses an intermediate shaft to equalize the bending angle of the drive shaft, but there is an isometric drive shaft. Loss occurs in transmission torque. Therefore, the present invention can be applied even to a vehicle that employs such an isometric drive shaft.

  Further, even when the engine is placed vertically in the engine room, in the case of an in-line engine, since it is mounted on the vehicle in a slanted state on either the left or right side, there is a difference in the torque applied to the left and right wheels. Therefore, the present invention can be applied even to a vertically installed engine.

  In addition, even in a so-called midship engine or rear engine, if there is a difference in torque transmitted to the left and right wheels, the torque is transmitted to the steering wheel via the chassis. appear. Therefore, the present invention can be applied to these engine-equipped vehicles.

  Further, even if the vehicle is other than the above, the present invention can be applied as long as a difference occurs in the engine torque transmitted to the left and right wheels.

  Further, the magnitudes of the engine torque and the drive shaft torque may be directly detected by a sensor or the like.

1 is a mechanical schematic configuration diagram illustrating a vehicle steering control device according to a first embodiment of the present invention. It is a control block diagram of the control unit in this embodiment. It is a flowchart figure which shows the basic assist control and torque steer control by the control unit. It is a table map which calculates | requires assist torque. It is a control flowchart figure which calculates | requires the torque steer correction value by the same control unit. It is a table map which calculates | requires an estimated engine torque corresponding to the flowchart of FIG. 6 is a table map for obtaining drive shaft torque corresponding to the flowchart of FIG. 6 is a table map for obtaining an estimated torque steer value corresponding to the flowchart of FIG. 5. 6 is a table map for obtaining an assist correction value corresponding to the flowchart of FIG. 5. It is a mechanical schematic block diagram which shows the steering control apparatus of the vehicle in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steering wheel 2 ... Steering shaft 4 ... Rack and pinion mechanism (steering mechanism)
5 ... Torque sensor 6 ... Hydraulic power cylinder (assist mechanism)
8 ... Electric motor (actuator)
DESCRIPTION OF SYMBOLS 9 ... Gear pump 10 ... Control unit 15 ... Vehicle speed sensor 16 ... Crank angle sensor 17 ... Throttle opening sensor 18 ... Gear position sensor 19 ... Wheel speed sensor

Claims (3)

A steering mechanism that is linked to the steering shaft and applies steering force to the steered wheels that are the left and right drive wheels ;
An assist mechanism for applying a steering assist force to the steering mechanism;
Actuator control means for outputting a control signal to an actuator of the assist mechanism based on a steering torque generated in the steering mechanism;
Left and right drive shafts that transmit engine drive torque to the left and right wheels of the steered wheels ;
In the steering control apparatus for a vehicle having the engine and the left and right torque difference detecting means for detecting or estimating the difference between the transmission torque output to the left and right drive shafts,
The left-right torque difference detection means is a relation between an engine torque detection circuit for detecting or estimating engine torque and a difference in torque applied to the left and right drive shafts with respect to the engine torque generated based on differences in rigidity between the left and right drive shafts. And detecting or estimating the difference in the transmission torque by referring to the storage circuit based on the engine torque,
The actuator control means includes a control circuit for driving and controlling the actuator in a direction to cancel torque steer generated by a transmission torque difference between the left and right drive shafts detected by the left and right torque difference detection means. Vehicle steering control device. A rotation difference detecting means for detecting or estimating a rotation difference between the left and right steered wheels;
A slip control means for preventing slip by controlling the torque transmitted to each steered wheel when the rotational difference between the left and right steered wheels is detected by the rotational difference detecting means;
The actuator control means, when the rotation difference between the left and right steered wheels is detected by the rotation difference detecting means, and when the transmission torque to the left and right steered wheels is controlled by the slip control means, The vehicle steering control device according to claim 1, wherein torque steer control by the control circuit is not performed . The left and right torque difference detecting means detects or estimates a transmission torque difference between the left and right drive shafts from information signals of at least a throttle opening of a throttle valve, a gear position of a transmission, and an engine speed. Item 3. The vehicle steering control device according to Item 1 or 2.

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