JP4951926B2 - Vehicle behavior control device - Google Patents

Description

  The present invention relates to a vehicle behavior control device including a suspension capable of variably controlling damping force.

As a vehicle suspension, a suspension capable of variably controlling the damping force has already been put into practical use (the following [Patent Document 1]). In such a damping force variable control suspension, the damping force is variably controlled by switching orifices having different diameters inside the shock absorber.
JP-A-6-42570

  However, in the conventional damping force variable control suspension, for example, when the damping force of the suspension is reduced, the roll damping at the time of steering becomes small, and the combined vibration of the roll and the yaw is likely to occur, so that the vehicle stability is lowered. There was a concern to do. Accordingly, an object of the present invention is to provide a vehicle behavior control device that can ensure vehicle stability.

The vehicle behavior control device according to claim 1 is a damping force variable means for changing the damping force of the suspension, and a steering characteristic variable control means capable of variably controlling steering characteristics including a steering steering system damping characteristic and a power steering assist characteristic. The steering characteristic variable control means changes the damping force of the damping characteristic of the steering steering system in accordance with the change in the damping force of the suspension by the damping force variable means, and the steering characteristic variable control means has the damping force variable means depending on the change in the damping force of the suspension by, by the power steering mechanism to correct the damping torque amount to be added to the steering system, to change the damping force of the damping characteristics of steering based, front-wheel-side damping force of the suspension When the steering wheel increases compared to the rear wheel side, the steering It is characterized by increasing the damping force of the damping characteristics of steering system.

  According to a second aspect of the present invention, in the vehicle behavior control device according to the first aspect, when the steering characteristic variable control means is made smaller than when the damping force of the suspension by the damping force variable means is made larger, steering steering is performed. It is characterized by increasing the damping force of the damping characteristics of the system.

  According to a third aspect of the present invention, in the vehicle behavior control device according to the second aspect, when the steering characteristic variable control means is made smaller than when the damping force of the suspension by the damping force variable means is made larger, steering steering is performed. It is characterized by reducing the assist force of the power steering assist characteristic of the system.

  According to a fourth aspect of the present invention, in the vehicle behavior control device according to the second or third aspect of the present invention, the vehicle behavior control device further includes a switching unit that switches the damping force of the suspension by the damping force varying unit and the steering characteristic of the steering steering system by the operation of the occupant. It is characterized by having.

  According to a fifth aspect of the present invention, in the vehicle behavior control device according to the first aspect, when the damping force on either the front wheel side or the rear wheel side of the suspension increases, the damping force of the steering steering system damping characteristic It is characterized by increasing.

  According to a sixth aspect of the present invention, in the vehicle behavior control device according to the first or fourth aspect, when the damping force on the front wheel side of the suspension increases as compared with that on the rear wheel side, the damping characteristic of the steering system is reduced. It is characterized by increasing the damping force.

  According to a seventh aspect of the present invention, in the vehicle behavior control device according to the first or fourth aspect, when the damping force on the rear wheel side of the suspension increases as compared with the front wheel side, the damping characteristic of the steering steering system is attenuated. It is characterized by increasing power.

  The invention according to claim 8 is the vehicle behavior control device according to any one of claims 1 to 7, wherein the suspension provided with the damping force variable means has a damping force variable absorber, When the absorber breaks down, it further comprises setting means for setting the damping force of the suspension to be constant, and the steering characteristic variable control means, when the absorber breaks down, according to the damping force set to be constant by the setting means, The damping characteristic of the steering system is changed.

  According to a ninth aspect of the present invention, in the vehicle behavior control device according to any one of the first to seventh aspects, the suspension damping force variable control and the power steering characteristic variable control are not coordinated during normal operation, and the absorber However, when the damping force of the suspension is fixed due to a failure, the damping force of the damping characteristic of the steering system is increased.

  According to the vehicle behavior control apparatus of the first aspect, the damping force change of the suspension is changed by changing the damping force of the damping characteristic of the steering steering system in accordance with the change of the damping force of the suspension by the damping force varying means. A change in the behavior of the vehicle is controlled using the damping force control of the steering, and the operability can be improved.

  According to the vehicle behavior control device of the second aspect, when the damping force of the suspension is made smaller than when the damping force is made larger, the damping force of the steering system is increased, thereby using the steering damping force. Thus, the above-described coupled vibration can be suppressed and the operability can be improved. When the damping force of the suspension is reduced, the roll resonance frequency is lowered and approaches the steering resonance frequency and the yaw resonance frequency, and the combined vibration of roll vibration and yaw vibration (and steering vibration) tends to occur. By changing the damping force of the steering steering system according to the change in the damping force of the suspension by the damping force varying means, the above-described coupled vibration is suppressed by using the steering damping force to control the steering. Can be improved.

  According to the vehicle behavior control apparatus of the third aspect, when the damping force of the suspension is made smaller than when the suspension damping force is increased, the steering damping is similarly reduced by reducing the assist force of the power steering assist characteristic of the steering system. As a result, the above-described coupled vibration can be suppressed and the operability can be improved.

  According to the vehicle behavior control apparatus of the fourth aspect, the suspension damping force and the steering characteristic can be changed according to the occupant's preference by further including the switching means that switches by the occupant's operation.

  According to the vehicle behavior control apparatus of the fifth aspect, when the damping force on either the front wheel side or the rear wheel side of the suspension is increased, the damping force of the damping characteristic of the steering steering system is increased, whereby the suspension Even when the damping force of the vehicle is changed, the vehicle behavior and operability can be maintained in a predetermined state by changing the steering characteristics.

  According to the vehicle behavior control apparatus of the sixth aspect, when the damping force on the front wheel side of the suspension increases compared to the rear wheel side, the vehicle tends to understeer transiently. In this case, yaw attenuation decreases, and further, the yaw resonance frequency increases, thereby approaching the roll resonance frequency (and the steering resonance frequency). As a result, the attenuation of the yaw vibration deteriorates, but by increasing the damping force of the damping characteristic of the steering steering system, the combined vibration related to the yaw vibration is suppressed by using the steering damping force, thereby improving the maneuverability. Can be improved.

  According to the vehicle behavior control apparatus of the seventh aspect, when the damping force on the rear wheel side of the suspension increases as compared with the front wheel side, the vehicle tends to oversteer transiently. In this case, the phase advance of the steering torque with respect to the steering angle of the steering is reduced, and the feeling of steering response is reduced. Therefore, by increasing the damping force of the damping characteristic of the steering system, it is possible to generate a phase advance of the steering torque to increase the feeling of steering response and improve the operational feeling.

  According to the vehicle behavior control device of the eighth aspect, when the absorber having the damping force variable function fails, the damping force is set to be constant and the damping characteristic of the steering steering system is changed according to the damping force. To do. In this way, even when an absorber having a variable damping force mechanism fails, the damping force change of the suspension can be changed by changing the damping force of the steering steering system damping characteristic according to the set damping force of the suspension. It is possible to improve the operability by controlling the change in the behavior of the vehicle with the use of the damping force control of the steering wheel.

  According to the vehicle behavior control device of the ninth aspect, when the absorber having the variable damping force function fails and the suspension damping force is fixed, the damping characteristic of the steering system is adjusted according to the damping force. Increase the damping force. By doing so, even when an absorber having a damping force variable mechanism fails, the vehicle behavior can be set to the stable side by using the damping force of the steering control, and the operability can be improved.

  Hereinafter, an embodiment of a vehicle behavior control device of the present invention will be described with reference to the drawings. FIG. 1 shows a vehicle configuration diagram in which the vehicle behavior control device of this embodiment is mounted. The vehicle 1 includes four wheels FR, FL, RR, and RL. The front wheels FR and FL are steering wheels, and the steering gear box 2 and the hub carrier 3 of each front wheel FR and FL are connected. A rack bar 2a is built in the gear box 2, and both ends of the rack bar 2a are connected to the hub carrier 3 described above via tie rods 2b.

  A steering shaft 4 in a steering column (not shown) is inserted into the gear box 2. A pinion gear at the front end of the steering shaft 4 meshes with the rack of the rack bar 2a to constitute a so-called rack and pinion 2c. A steering wheel 5 is attached to the other end of the steering shaft 4. In addition, a steering angle sensor 6 that detects a rotation angle (steering angle) of the steering shaft 4 and a steering torque sensor 7 that detects torque applied to the steering shaft 4 are also attached to the steering shaft 4.

  The electric power steering mechanism of the present embodiment includes a motor 8 that applies a rotational force to the steering shaft 4. By controlling the control amount of the motor 8, the power steering assist force or the steering system Damping torque can be added to attenuate the vibration of the. The steering gear box 2 also includes a stroke sensor 2d that detects the stroke amount of the rack bar 2a.

  In the vehicle 1 of the present embodiment, the suspension unit 9 is attached to all the wheels FR, FL, RR, and RL. The suspension unit 9 includes a shock absorber with a damping force variable mechanism and a coil spring. The shock absorber with a variable damping force mechanism is a conventional unit with a known variable damping force mechanism. For example, the damping force is variably controlled by switching orifices having different diameters using an electric motor or the like inside the shock absorber.

  Further, a wheel speed sensor 10 is attached to each wheel FR, FL, RR, RL. The above-described sensors 2d, 6, 7 and actuators 8, 9 are connected to an ECU 11 that controls the vehicle behavior in an integrated manner. The ECU 11 is an electronic control unit including a CPU, a ROM, a RAM, an input / output unit, and the like. The ECU 11 receives an output from each sensor and sends a control signal to each actuator. Further, the ECU 11 is also connected to a switch 12 for switching suspension damping force setting and steering characteristics (including damping characteristics and power assist characteristics) between emphasis on maneuverability and ride comfort. The cause of victory is that the switch 12 can switch the damping force setting and steering characteristics of the suspension as desired.

  The power steering mechanism will be briefly described. The power steering mechanism applies the assist torque for reducing the steering operation force of the driver to the steering system by the motor 8, but the motor 8 also has a role of applying a damping torque for reducing the steering vibration. Here, the assist torque amount is calculated based on the steering torque detected by the steering torque sensor 7 and the vehicle speed detected by the wheel speed sensor 10.

  At the same time, a damping torque amount for attenuating steering vibration is calculated based on the steering angular velocity and the vehicle speed of the steering wheel 5 detected by the steering angle sensor 6. The attenuation coefficient at this time is Cst. Further, when increasing the steering damping coefficient, Ksc is used as the correction coefficient (Cst ← Cst × Ksc). If Ksc = 1, no correction is performed. The torque output from the motor 8 is the sum of the assist torque and the damping torque.

  Further, the steering resonance frequency, yaw resonance frequency, and roll resonance frequency will be briefly described. Normally, these resonance frequencies are arranged in the order of roll resonance frequency, steering resonance frequency, and yaw resonance frequency from the highest. Each resonance frequency is set so as to be as far as possible from each other so that mutual vibrations are coupled and resonances do not overlap.

  However, when the damping force of the suspension is variably controlled, the roll resonance frequency changes and may approach the yaw resonance frequency (and the steering resonance frequency). In this case, the above-described coupled vibration is likely to occur. Therefore, in this embodiment, by increasing the damping coefficient of the steering vibration, the coupled vibration such as roll vibration, yaw vibration, steering vibration, and the like is suppressed, and the steering vibration is reduced. Improve sexiness.

  Next, an embodiment of damping force control by the above-described apparatus will be described. A flowchart of this control is shown in FIG. As shown in FIG. 2, first, it is determined whether or not the above-described switch 12 is ON (setting for ride comfort: setting of suspension damping force is small) (step 200). If step 200 is affirmed, it is determined whether or not the assist map A has a reduced suspension damping force to improve riding comfort (step 205).

  If step 205 is negative, the map is switched to assist map A (step 210). Further, the steering damping force is also changed in accordance with the assist map A having a smaller suspension damping force. This is because, as described above, the roll resonance frequency is lowered due to the suspension damping force being lowered, and it is suppressed that the combined vibration is likely to occur near the yaw resonance frequency (and the steering resonance frequency). Specifically, the correction coefficient Ksc for correcting the steering attenuation coefficient Cst is set to Kscd (> 1) (step 215). Thereafter, Cst = Cst × Ksc (step 220), and the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is corrected.

  On the other hand, when step 205 is affirmed, it is considered that the process has already passed through steps 210 to 220 once, so the process returns to step 200 to monitor the operation of the switch 12 again. In step 200, it is determined whether or not the switch 12 is off (setting for emphasis on maneuverability: suspension damping force is large). If the switch 12 is off, it is determined whether or not the assist map B has a suspension suspension force that increases the maneuverability (step 225).

  If step 225 is negative, the map is switched to the assist map B (step 230). In this case, coupled vibrations of roll vibration and yaw vibration (and steering vibration) due to a decrease in suspension damping force are less likely to occur. Therefore, the correction coefficient Ksc for correcting the steering attenuation coefficient Cst is set to 1 (step 235). Thereafter, Cst = Cst × Ksc (step 220). In this case, since the correction coefficient Ksc = 1, the steering damping force remains under normal control (the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is not corrected).

  In the above-described embodiment, the damping of the steering vibration is increased by correcting (increasing) the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed, and the combined vibration of the roll resonance and the yaw resonance is suppressed. . However, even if the steering assist force calculated based on the steering torque and the vehicle speed is corrected (decreased), the steering damping force can be improved as a result. Therefore, the assist force is reduced as the suspension damping force decreases. Thus, the above-described coupled vibration can be suppressed.

  Further, as the damping force variable control mode, there is a mode in which the damping force is changed between the front wheel side and the rear wheel side. In this way, when the damping force on either the front wheel side or the rear wheel side of the suspension increases, even if the damping force of the suspension is changed by increasing the damping force of the damping characteristic of the steering steering system, By changing the steering characteristics, the vehicle behavior and operability can be maintained in a predetermined state. In addition, rather than increasing the damping force of the damping characteristic of the steering system,

  For example, when the damping force on the front wheel side of the suspension increases as compared with the rear wheel side, an understeer tendency tends to occur transiently. In this case, yaw attenuation decreases, and further, the yaw resonance frequency increases, thereby approaching the roll resonance frequency (and the steering resonance frequency). As a result, the attenuation of the yaw vibration deteriorates, but by increasing the damping force of the damping characteristic of the steering steering system, the combined vibration related to the yaw vibration is suppressed by using the steering damping force, thereby improving the maneuverability. Can be improved.

  Alternatively, when the damping force on the rear wheel side of the suspension increases as compared with the front wheel side, the vehicle tends to oversteer transiently. In this case, the phase advance of the steering torque with respect to the steering angle of the steering is reduced, and the feeling of steering response is reduced. Therefore, by increasing the damping force of the damping characteristic of the steering system, it is possible to generate a phase advance of the steering torque to increase the feeling of steering response and improve the operational feeling.

  Next, another embodiment will be described based on the flowchart of FIG. This embodiment assumes that the suspension damping force variable mechanism has failed. As shown in FIG. 3, first, it is determined whether or not a sensor that detects the operating state (set damping force) of the shock absorber that is expected to write the damping force variable mechanism has failed (step 300). If the sensor is not faulty, step 300 is executed again and the sensor abnormality is monitored.

  On the other hand, if the sensor fails and the suspension damping force variable mechanism cannot be controlled normally, it is next determined whether or not the actuator of the damping force variable mechanism can be operated (step 305). This determines whether or not the damping force value can be varied although the damping force value and the like cannot be detected. If step 305 is negative and the damping force can be changed by operating the actuator, the suspension damping force (the number of damping force steps) set in advance is set (front wheel side Sf, rear wheel side Sr).

  Here, this damping force (number of steps) is determined by the balance between riding comfort and maneuverability, but it is not set to the maximum number of damping force steps in consideration of riding comfort, so roll damping is important for maneuverability. This is a setting in which the above-described coupled vibration of roll vibration and yaw vibration (and steering vibration) is concerned. Therefore, after step 310, the correction coefficient Ksc for correcting the steering attenuation coefficient Cst is set to Kscf1 (> 1) (step 315). The value of the correction coefficient Kscf1 is a value determined according to the front wheel side step number Sf and the rear wheel side step number Sr corresponding to the suspension damping force. Thereafter, Cst = Cst × Ksc (step 320), the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is corrected, and the above-described coupled vibration is suppressed.

  On the other hand, if step 305 is affirmed and the number of damping force steps cannot be changed (a failure mode in which the number of steps is fixed), it is assumed that the suspension damping force is fixed with an emphasis on ride comfort and steering damping. The correction coefficient Ksc is set to Kscf2 (here,> Kscf1) so that the force becomes a large value, that is, to ensure the operability (step 325). Thereafter, Cst = Cst × Ksc (step 320), the steering damping torque amount calculated based on the steering angular velocity and the vehicle speed is corrected, and the above-described coupled vibration is suppressed.

  The present invention is not limited to the embodiment described above. For example, in the embodiment described above, the suspension damping force variable control and the power steering characteristic variable control are always coordinated, but this is not performed in the normal state, but only when there is an abnormality in the damping force variable control. In order to compensate, it may be made to cooperate. For example, when the suspension damping force variable control and the power steering characteristic variable control are not coordinated during normal operation, and the suspension shock absorber is broken and the suspension damping force is fixed, the steering steering system damping characteristic If the control can be performed to increase the damping force, the vehicle behavior can be set to the stable side by using the damping force of the suspension, and the operability can be improved.

  In the above-described embodiment, the assist torque of the power steering generated by the actuator (motor 8) and the damping torque for damping the steering vibration are applied to the steering shaft 4. However, a system in which an actuator that generates assist torque or damping torque is attached to the steering gear box 2 and controls the sliding movement (sliding amount) of the rack bar 2a may be used.

It is a vehicle block diagram carrying one Embodiment of the vehicle behavior control apparatus of this invention. It is a flowchart of steering damping torque correction control by the apparatus of FIG. 2 is a flowchart of steering damping torque correction control (when the suspension damping mechanism is malfunctioning) by the apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Steering gear box, 2a ... Rack bar, 2b ... Tie rod, 2c ... Rack and pinion, 2d ... Stroke sensor, 3 ... Hub carrier, 4 ... Steering shaft, 5 ... Steering wheel, 6 ... Steering angle sensor , 7 ... steering torque sensor, 8 ... motor (steering characteristic variable control means), 9 ... damping force variable suspension unit (damping force variable means), 10 ... wheel speed sensor, 11 ... ECU (damping force variable means, steering characteristic variable) Control means). 12 ... changeover switch.

Claims (4)

A damping force variable means for changing the damping force of the suspension;
Steering characteristic variable control means capable of variably controlling steering characteristics including steering steering system damping characteristics and power steering assist characteristics,
The steering characteristic variable control means changes the damping force of the damping characteristic of the steering steering system in accordance with a change in the damping force of the suspension by the damping force variable means,
The steering characteristic variable control means corrects a damping torque amount applied to the steering steering system by a power steering mechanism in accordance with a change in the damping force of the suspension by the damping force variable means, thereby damping the steering steering system. A vehicle behavior control device characterized in that when the damping force of the characteristic is changed and the damping force on the front wheel side of the suspension increases compared to the rear wheel side, the damping force of the damping characteristic of the steering system is increased. . The vehicle behavior control device according to claim 1 , further comprising switching means for switching a suspension damping force by the damping force varying means and a steering characteristic of the steering system by an operation of an occupant. The suspension including the damping force varying means is configured to have a damping force variable absorber, and further includes setting means for setting the damping force of the suspension to be constant when the absorber fails.
The steering characteristic variable control means, when the absorber has failed, depending on the damping force is set to a constant by the setting means, according to claim 1 or 2, characterized in that to change the damping characteristics of the steering system The vehicle behavior control device described in 1. Normally, the suspension damping force variable control and the power steering variable characteristic control are not coordinated, and when the damping force of the suspension is fixed due to a failure of the absorber, the damping characteristic of the steering system is attenuated. The vehicle behavior control device according to any one of claims 1 to 3 , wherein the force is increased.

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