JP2010089539A - Steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering system offering excellent running stability without degrading its steering feel during towing of a trailer. <P>SOLUTION: The electric power steering system includes a yaw rate sensor 18 for detecting a yaw rate of a vehicle, an auxiliary reactive torque determination means 32 for controlling auxiliary reactive torque according to the vehicle's yaw rate detected by the yaw rate sensor 18, and a trailer connection switch 22 for detecting a state of towing the trailer by the vehicle. When the trailer connection switch 22 detects the towing of the trailer, the steering system reduces a controlled variable (i.e., the auxiliary reactive torque) determined by the auxiliary reactive torque determination means 32. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus capable of towing a trailer.

  The electric power steering device for reducing the steering force of the driver detects the vehicle behavior by the yaw rate detected by the yaw rate sensor in order to enhance the vehicle deflection suppression performance when a disturbance such as cross wind acts on the vehicle. Some control the steering assist force by controlling the electric assist motor in accordance with the detected yaw rate (see, for example, Patent Document 1). According to this electric power steering apparatus, the running stability of the vehicle is improved.

On the other hand, it is known that when a trailer (including a camper) is connected to a vehicle and pulled, a pendulum motion may occur in the vehicle and the trailer. When this pendulum motion occurs, the trailer vibrates around the vertical axis, causing the vehicle to resonate via the coupler. A trailer tow brake control device is known as a device for improving the running stability of a vehicle during trailer towing (see, for example, Patent Document 2). The trailer traction brake control device performs automatic brake control that activates a brake on one side of the vehicle rear wheel so that a yaw moment in the opposite phase to the vehicle pendulum motion is generated when the vehicle pendulum motion is detected. The pendulum movement is suppressed.
JP-A-11-147482 Japanese Patent No. 3997086

  By the way, when the vehicle is towing the trailer, disturbance from the trailer is input to the vehicle. At this time, the electric power steering device is activated according to the vehicle behavior (yaw rate) caused by the disturbance from the trailer, When the steering assist force is controlled, the steering feel may deteriorate.

  In particular, when the vehicle is provided with the trailer tow brake control device and the automatic brake control by the trailer tow brake control device and the vehicle behavior suppression control by the electric power steering device are simultaneously operated, the steering feel is worse. There is a case.

  Therefore, the present invention provides a steering device that does not deteriorate the steering feel when trailer is pulled and has excellent running stability.

In order to solve the above-mentioned problem, the invention according to claim 1 is a vehicle behavior detecting means (for example, a yaw rate sensor 18 in an embodiment described later) for detecting a vehicle behavior and the vehicle behavior detecting means detects the vehicle behavior. A steering device (for example, an embodiment to be described later) having a vehicle behavior suppression control unit (for example, an auxiliary reaction force torque determining means 32 in an embodiment to be described later) that controls the steering assist force according to the vehicle behavior. Electric trailer pulling means (for example, a trailer connection switch 22 in an embodiment to be described later) for detecting a state in which the vehicle is pulling the trailer. If detected, the steering device is characterized in that the control amount of the vehicle behavior suppression control unit is reduced.
With this configuration, it is possible to reduce the steering assist force generated according to the vehicle behavior caused by the disturbance from the trailer.

The invention according to claim 2 is the invention according to claim 1, wherein the vehicle includes a trailer traction brake control device that detects vibration around a vertical axis of the trailer and controls a brake in accordance with the vibration. When the trailer traction brake control device is operating, the control amount of the vehicle behavior suppression control unit is reduced.
By comprising in this way, it can suppress that the vehicle behavior suppression control of a vehicle behavior suppression control part interferes with the brake control of a trailer traction brake control apparatus.

  According to the first aspect of the present invention, the steering assist force generated according to the vehicle behavior caused by the disturbance from the trailer can be reduced, so that the deterioration of the steering feel when the trailer is pulled can be suppressed.

  According to the second aspect of the present invention, since the vehicle behavior suppression control of the vehicle behavior suppression control unit can be inhibited from interfering with the brake control of the trailer traction brake control device, the steering feel at the time of trailer traction is deteriorated. Can be suppressed.

  Embodiments of a steering apparatus according to the present invention will be described below with reference to the drawings of FIGS. In addition, the steering apparatus in this embodiment is an aspect as an electric power steering apparatus for a vehicle capable of towing a trailer including a camper.

  First, the configuration of the electric power steering apparatus will be described with reference to FIG. The electric power steering apparatus includes a manual steering force generating mechanism 1, and the manual steering force generating mechanism 1 includes a steering shaft 4 integrally coupled to a steering wheel (operator) 3 and a connecting shaft 5 having a universal joint. Via a pinion 6 of a rack and pinion mechanism. The pinion 6 meshes with a rack 7a of a rack shaft 7 that can reciprocate in the vehicle width direction, and left and right front wheels 9, 9 as steered wheels are connected to both ends of the rack shaft 7 via tie rods 8, 8. ing. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 3 is steered, and the direction of the vehicle can be changed by turning the front wheels 9 and 9. The rack shaft 7 and the tie rods 8 and 8 constitute a steering mechanism.

  In addition, an electric motor 10 that supplies auxiliary steering force for reducing the steering force generated by the manual steering force generation mechanism 1 is disposed coaxially with the rack shaft 7. The auxiliary steering force supplied by the electric motor 10 is converted into thrust through a ball screw mechanism 12 provided substantially parallel to the rack shaft 7 and is applied to the rack shaft 7. For this purpose, a drive-side helical gear 11 is integrally provided on the rotor of the electric motor 10 through which the rack shaft 7 is inserted, and a driven-side helical gear 13 meshing with the drive-side helical gear 11 is provided at one end of the screw shaft 12a of the ball screw mechanism 12. The nut 14 of the ball screw mechanism 12 is fixed to the rack 7.

  The steering shaft 4 is provided with a steering angular velocity sensor 15 for detecting the steering angular velocity of the steering shaft 4, and a pinion is installed in a steering gear box (not shown) that houses the rack and pinion mechanism (6, 7a). A steering torque sensor 16 for detecting a steering torque acting on the steering wheel 6 is provided. The steering angular velocity sensor 15 outputs an electrical signal corresponding to the detected steering angular velocity, and the steering torque sensor 16 outputs an electrical signal corresponding to the detected steering torque to the steering control device 20, respectively.

  Further, at appropriate positions of the vehicle body, a lateral acceleration sensor 17 for detecting lateral acceleration applied in the vehicle width direction of the vehicle, a yaw rate sensor (vehicle behavior detecting means) 18 for detecting the yaw rate of the vehicle, and the vehicle body speed are set. A vehicle speed sensor 19 for detection is attached. The lateral acceleration sensor 17 is an electrical signal corresponding to the detected lateral acceleration, the yaw rate sensor 18 is an electrical signal corresponding to the detected yaw rate, and the body speed sensor 19 is an electrical signal corresponding to the detected body speed. 20 is output.

  Further, this vehicle capable of towing a trailer includes a trailer connection switch 22. The trailer connection switch 22 outputs an ON signal to the steering control device 20 when the trailer is connected to the vehicle via a connector (not shown), and an OFF signal when the trailer is not connected. In this embodiment, the trailer connection switch 22 constitutes trailer tow detection means for detecting a state in which the vehicle is towing the trailer.

  Further, this vehicle is provided with a trailer traction brake control device (not shown). A trailer traction brake control device (hereinafter abbreviated as TSA) is used when, for example, the vehicle yaw rate detected by the yaw rate sensor 18 or the vehicle lateral acceleration detected by the lateral acceleration sensor 17 is generated substantially periodically. When the pendulum motion is determined to occur, and when it is determined that the pendulum motion is occurring (in other words, when the pendulum motion is detected), a yaw moment having the opposite phase to the pendulum motion of the vehicle is generated. Thus, the automatic brake control for operating the brake on one side of the vehicle rear wheel is performed to suppress the pendulum movement of the vehicle.

  When the TSA detects the pendulum movement of the vehicle and executes the automatic brake control, the TSA outputs a TSA operation flag F_TSA = 1 to the steering control device 20 as TSA operation information, and the pendulum movement of the vehicle is not detected. When automatic brake control is not being executed, a TSA operation flag F_TSA = 0 is output to the steering control device 20 as TSA operation information.

  The steering control device 20 determines a target current to be supplied to the electric motor 10 by a control signal obtained by processing input signals from the sensors 15 to 19 and the trailer connection switch 22 and TSA operation information, and a drive circuit 21. The output torque of the electric motor 10 is controlled by supplying the electric power to the electric motor 10, and the auxiliary steering force in the steering operation is controlled.

Next, output torque control of the electric motor 10 in this embodiment will be described with reference to the control block diagram of FIG.
The steering control device 20 includes auxiliary steering torque determining means 31, auxiliary reaction force torque determining means (steering reaction force device) 32, target current determining means 33, and output current control means 34.

  The auxiliary steering torque determining means 31 determines the auxiliary steering torque based on output signals from the steering angular velocity sensor 15, the steering torque sensor 16, and the vehicle body speed sensor 19. Since the method for determining the auxiliary steering torque in the auxiliary steering torque determining means 31 is the same as that of the known electric power steering, detailed description thereof will be omitted. In general, the auxiliary steering torque decreases as the steering angular velocity increases, and the steering torque becomes smaller. The auxiliary steering torque is set so as to increase as the vehicle speed increases, and the auxiliary steering torque decreases as the vehicle body speed increases.

The auxiliary reaction torque determination means 32 is based on the output signals of the steering angular velocity sensor 15, the lateral acceleration sensor 17, the yaw rate sensor 18, the vehicle body speed sensor 19, and the ON / OFF signal of the trailer connection switch 22 or TSA operation information. Then, the auxiliary reaction force torque TA is determined. The process for determining the auxiliary reaction force torque TA will be described in detail later.
The target current determination unit 33 calculates the target output torque of the electric motor 10 by adding the auxiliary steering torque determined by the auxiliary steering torque determination unit 31 and the auxiliary reaction force torque determined by the auxiliary reaction force torque determination unit 32. A target current corresponding to the target output torque is determined based on a known output characteristic of the electric motor 10.
The output current control unit 34 controls the output current to the motor 10 so that the actual current of the motor 10 matches the target current determined by the target current determination unit 33, and outputs it to the drive circuit 21.

Next, the process of determining the auxiliary reaction force torque TA by the auxiliary reaction force torque determining means 32 will be described in detail.
The auxiliary reaction force torque determining means 32 basically determines the steering reaction force according to the vehicle behavior (yaw rate in this embodiment) based on the vehicle body speed V, the steering angular velocity ω, and the vehicle yaw rate γ. The reaction force is corrected according to the degree of instability of the vehicle, and the amount of correction for the steering reaction force is increased as the degree of instability of the vehicle increases. In addition, since the possibility that the vehicle becomes unstable increases as the steering angular velocity ω increases, the correction amount for the steering reaction force increases as the steering angular velocity ω increases.

  Then, the side slip angle differential value Δβ of the vehicle is adopted as a parameter of the degree of instability of the vehicle. The side slip angle β of the vehicle refers to an angle formed by the traveling direction of the vehicle and the longitudinal axis of the vehicle, and the side slip angle β is obtained by time-differentiating the side slip angle β. Note that the side slip angle differential value Δβ is more suitable as the parameter of the degree of vehicle instability than the side slip angle β.

By the way, it is known that the lateral acceleration Gy of the vehicle can be estimated from the equation (1) based on the vehicle speed V, the yaw rate γ of the vehicle, and the side slip angle differential value Δβ of the vehicle from the physical relationship of the state quantity of the vehicle motion. (See, for example, JP-A-2003-146154).
Gy = V (γ + Δβ) (1)
Based on this, the side slip angle differential value Δβ can be calculated from the equation (2).
Δβ = (Gy / V) −γ Expression (2)
In this embodiment, the side slip angle differential value Δβ is estimated and calculated based on the output signals of the steering angular velocity sensor 15, the yaw rate sensor 18, and the vehicle body speed sensor 19. Thereby, the degree of instability of the vehicle can be easily detected.

  Further, the auxiliary reaction force torque determining means 32 sets the steering reaction force to zero when the TSA is executing the automatic brake control so that the yaw moment having the opposite phase to the pendulum motion of the vehicle is generated, and the TSA performs the automatic brake control. Control is performed so that the steering reaction force is generated only when the control is not executed.

  Next, the auxiliary reaction force torque determination process executed in the auxiliary reaction force torque determination means 32 will be described with reference to the flowchart shown in FIG. 3 and the block diagram shown in FIG. The auxiliary reaction force torque determination process routine shown in the flowchart of FIG. 3 is repeatedly executed by the steering control device 20 at regular intervals.

  First, in step S101, referring to the first auxiliary reaction torque table 41 shown in FIG. 4, the auxiliary reaction force torque (hereinafter referred to as the steering angular velocity ω) based on the output signals of the steering angular velocity sensor 15 and the vehicle body speed sensor 19 is described below. T1) (referred to as auxiliary reaction torque angular velocity component). The first auxiliary reaction torque table 41 is a table having the steering angular velocity ω set for each vehicle speed V as an address, and as the steering angular velocity ω increases, the auxiliary reaction force torque angular velocity component T1 increases, and the vehicle speed V increases. The auxiliary reaction torque angular velocity component T1 is set so as to increase as it increases.

Next, proceeding to step S102, referring to the second auxiliary reaction force torque table 42 shown in FIG. 4, the auxiliary reaction force torque (hereinafter referred to as the yaw rate γ) based on the respective output signals of the yaw rate sensor 18 and the vehicle body speed sensor 19 is referred to. T2) (referred to as auxiliary reaction force torque yaw rate component). The second auxiliary reaction torque table 42 is a table that uses the yaw rate γ set for each vehicle speed V as an address, and as the yaw rate γ increases, the auxiliary reaction force torque yaw rate component T2 increases and the vehicle speed V increases. The auxiliary reaction force torque yaw rate component T2 is set to be large.
That is, in this embodiment, the yaw rate γ is used as a vehicle behavior parameter, and the auxiliary reaction force torque (behavior reaction force) T2 increases as the yaw rate γ increases, in other words, as the vehicle behavior increases.

In step S103, Gy / V is calculated based on output signals from the lateral acceleration sensor 17 and the vehicle body speed sensor 19.
Next, proceeding to step S104, the differential value Δβ of the skid angle β is calculated {Δβ = (Gy / V) −γ}.

  Next, the process proceeds to step S105, and a correction coefficient K1 corresponding to the skid angle differential value Δβ obtained in step S104 is obtained with reference to the correction coefficient table 43 shown in FIG. The correction coefficient table 43 is a table whose address is the side slip angle differential value Δβ set for each steering angular velocity ω, and the correction coefficient K1 increases as the absolute value of the side slip angle differential value Δβ increases, and the steering angular velocity ω increases. The correction coefficient K1 is set so as to increase. More specifically, the correction coefficient K1 becomes the minimum value when the side slip angle differential value Δβ is zero, and the correction coefficient increases as the absolute value of the side slip angle differential value Δβ increases until the absolute value of the side slip angle differential value Δβ reaches a predetermined value. K1 gradually increases, and after the absolute value of the side slip angle differential value Δβ reaches a predetermined value, the correction coefficient K1 is set to be constant. When the side slip angle differential value Δβ is the same, the correction coefficient K1 is set to a larger value as the steering angular velocity ω increases.

  Next, it progresses to step S106 and the coefficient K2 is calculated | required according to TSA operation information. More specifically, when the TSA operation flag F_TSA, which is TSA operation information, is “1” (that is, when the TSA is performing automatic brake control so that a yaw moment having a phase opposite to the pendulum motion of the vehicle is generated). Sets “0” as the coefficient K2, and sets “0” as the coefficient K2 when the TSA operation flag F_TSA is “0” (that is, when the TSA is not executing the automatic brake control). .

Next, the process proceeds to step S107, the auxiliary reaction force torque angular velocity component T1 obtained in step S101, the auxiliary reaction torque torque yaw rate component T2 obtained in step S102, the correction coefficient K1 obtained in step S105, and obtained in step S106. From the coefficient K2, the auxiliary reaction force torque TA is calculated by the following equation (3).
TA = (T1 + T2) · K1 · K2 (3)

When the auxiliary reaction torque TA is calculated in this way, even when the vehicle body speed V, the steering angular velocity ω, and the yaw rate γ are the same, when the side slip angle differential value Δβ is small, that is, when the degree of instability of the vehicle is small, Since the correction coefficient K1 is small, the auxiliary reaction force torque TA is set small, and when the side slip angle differential value Δβ is large, that is, when the degree of instability of the vehicle is large, the correction coefficient K1 is large, so the auxiliary reaction force torque TA is large. Is set. As a result, when the vehicle is unstable, the vehicle deflection suppression performance can be improved and the running stability of the vehicle can be improved.
Further, since the correction coefficient K1 increases as the steering angular velocity ω increases, the auxiliary reaction force torque TA is set larger, and the running stability of the vehicle can be further improved.

  Furthermore, when the TSA is executing automatic brake control to suppress the pendulum movement of the vehicle, the coefficient K2 is zero, so the auxiliary reaction force torque TA is also zero. As a result, when the vehicle is towing the trailer, the vehicle behavior suppression control of the electric power steering device can be prevented from interfering with the brake control of the trailer towing brake control device. That is, the steering assist control of the electric power steering device can be prevented from interfering with the automatic brake control of the trailer traction brake control device. Thereby, deterioration of the steering feel at the time of trailer trailing can be prevented.

Next, the process proceeds to step S108, and it is determined whether or not the auxiliary reaction force torque TA calculated in step S107 is larger than the auxiliary reaction force torque maximum value Tmax.
If the determination result in step S108 is “NO” (TA ≦ Tmax), the process proceeds to step S109. On the other hand, if the determination result in step S108 is “YES” (TA> Tmax), the process proceeds to step S110, the auxiliary reaction force torque maximum value Tmax is set to the auxiliary reaction force torque TA, and the process proceeds to step S109. That is, the process of step S110 functions as a limiter that prevents the auxiliary reaction force torque TA from exceeding the auxiliary reaction force torque maximum value Tmax.

In step S109, it is determined whether or not the auxiliary reaction force torque TA calculated in step S107 is smaller than the auxiliary reaction force torque minimum value −Tmax.
If the determination result in step S109 is “NO” (TA ≧ −Tmax), the execution of this routine is temporarily terminated. On the other hand, if the determination result in step S109 is “YES” (TA <−Tmax), the process proceeds to step S111, the auxiliary reaction force torque minimum value −Tmax is set to the auxiliary reaction force torque TA, and the execution of this routine is once ended. To do. That is, the process of step S111 functions as a limiter that prevents the auxiliary reaction force torque TA from becoming smaller than the auxiliary reaction force torque minimum value −Tmax.

  In the above-described embodiment, when the TSA operation flag F_TSA which is the TSA operation information is “1” (that is, the TSA performs the automatic brake control so that the yaw moment having the opposite phase to the pendulum motion of the vehicle is generated). The coefficient K2 is set to "0", and the coefficient K2 is set to "0" when the TSA operation flag F_TSA is "0" (that is, when the TSA is not executing the automatic brake control) However, instead, when the trailer connection switch 22 is ON (that is, when the vehicle is pulling the trailer), the coefficient K2 is set to “0” and the trailer connection switch 22 is OFF ( That is, the coefficient K2 may be set to “1” when the vehicle is not towing the trailer. By doing so, it is possible to prevent a steering reaction force corresponding to the vehicle behavior caused by the disturbance from the trailer when towing the trailer, and thus it is possible to suppress the deterioration of the steering feel.

  In the above-described embodiment, the value of the coefficient K2 is set to “0” when the TSA operation flag F_TSA is “1”, or the value of the coefficient K2 is set to “0” when the trailer connection switch 22 is ON. However, the value of the coefficient K2 set in these cases is not limited to “0”, and can be changed to an appropriate value as long as it is a positive value smaller than 1.

  When the coefficient K2 is set to a positive value smaller than 1 when the TSA operation flag F_TSA is “1”, the vehicle behavior suppression control of the electric power steering device is applied to the trailer towing brake when the vehicle is towing the trailer. Interference with the automatic brake control of the control device can be suppressed. That is, it is possible to suppress the steering assist control of the electric power steering device from interfering with the automatic brake control of the trailer traction brake control device. Thereby, deterioration of the steering feel at the time of trailer trailing can be prevented.

  Further, when the coefficient K2 is set to a positive value smaller than 1 when the trailer connection switch 22 is ON, it is possible to reduce the steering reaction force according to the vehicle behavior caused by the disturbance from the trailer when towing the trailer. Therefore, it is possible to suppress the deterioration of the steering feel when the trailer is pulled.

  In the above-described embodiment, the vehicle yaw rate is used as a vehicle behavior parameter. However, instead of or in addition to the yaw rate, the lateral acceleration of the vehicle may be used as a vehicle behavior parameter.

1 is a configuration diagram of an electric power steering apparatus that is an embodiment of a steering apparatus according to the present invention. FIG. FIG. 3 is a block diagram of motor output torque control in the electric power steering device. It is a flowchart which shows the auxiliary reaction force torque determination process in the said motor output torque control. It is a block diagram of the auxiliary reaction force torque determination processing.

Explanation of symbols

18 Yaw rate sensor (vehicle behavior detection means)
22 Trailer connection switch (Trailer traction detection means)
32 Auxiliary reaction force torque determining means (vehicle behavior suppression control unit)

Claims (2)

Vehicle behavior detection means for detecting vehicle behavior;
A vehicle behavior suppression control unit that controls a steering assist force according to the vehicle behavior when the vehicle behavior is detected by the vehicle behavior detection unit;
In a steering apparatus equipped with
Trailer tow detection means for detecting a state in which the vehicle is towing the trailer is provided, and when the trailer tow detection means detects trailer towing, the control amount of the vehicle behavior suppression control unit is reduced. Steering device.   The vehicle includes a trailer traction brake control device that detects vibration around a vertical axis of the trailer and controls a brake in accordance with the vibration, and when the trailer traction brake control device is operating, the vehicle The steering apparatus according to claim 1, wherein a control amount of the behavior suppression control unit is reduced.

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