JP2013129334A - Steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering system that can achieve low costs and light weight while improving steering feeling.SOLUTION: The steering system 10 that can perform steering assist operation for applying an assist force to assist the steering of a steering device 20 by using a driving force generated at a motor 24. The steering system 10 includes steering torque detection means for detecting steering torque Ts, and restricts the steering assist operation under the condition that the steering torque Ts near the tail end of a steering possible range is equal to or more than a prescribed value.

Description

  The present invention relates to a steering system capable of performing a steering assist operation for assisting steering using a driving force generated in a driving source.

  Conventionally, a steering system such as a motor-driven power steering unit disclosed in Patent Document 1 below has been provided. The power steering unit of Patent Document 1 executes control for reducing assist by the motor in the terminal stopper region for the purpose of making it possible to adjust the running feeling in the left and right terminal stopper regions.

JP 2004-521010 A

  However, in the power steering unit described above, the assist force due to the steering assist operation by the motor is reduced in the vicinity of the terminal stopper region regardless of whether the steering operation is steep or not. Therefore, in the power steering unit of the prior art, the assist force at the time of steering is reduced even when performing slow steering in the vicinity of the terminal stopper region, and the driver feels uncomfortable with the steering feeling. is there.

  In view of the above, an object of the present invention is to provide a steering system capable of reducing the cost or weight while improving the steering feeling.

  The steering system of the present invention provided to solve the above-described problem is a steering system capable of performing a steering assist operation in which an assist force is applied so as to assist the steering of the steering device using the drive force generated in the drive source. The steering speed detecting means capable of detecting the steering speed and / or the steering torque detecting means capable of detecting the steering torque are provided, and the steering speed and / or the steering torque in the vicinity of the end of the steerable range is not less than a predetermined value. The steering assist operation is limited or prohibited on the condition that

  In the steering system of the present invention, on the condition that either one or both of the steering speed and the steering torque near the end of the steerable range are equal to or greater than a predetermined value, that is, a steep steering operation is performed near the end. The steering assist operation is restricted or prohibited. As a result, in the vicinity of the end of the steerable range, the force (steering force) required for the driver to steer increases and it is possible to prevent an excessively large impact from being applied to the steering device side. Specifically, when the steering device has a structure in which a stopper is provided at the end of the steerable range, it can be avoided that an excessively large impact is applied to the stopper. Therefore, according to the steering system of the present invention, it is possible to simplify the configuration in preparation for an impact caused by steering near the end of the steerable range. Specifically, it is not necessary to employ a member having a high impact resistance as the above-described member such as a stopper. Thereby, effects such as cost reduction or weight reduction of the steering system can be obtained.

  In addition, when a steep steering operation is performed near the end of the steerable range, the steering assist operation is restricted or prohibited, so that the steering rotation operation becomes heavy. Can prevent people from feeling. Further, when a gentle steering operation is performed, the steering assist operation is not limited or prohibited, and the driver does not feel uncomfortable with the steering feeling. Therefore, according to the steering system of the present invention, the steering feeling can be improved.

  Further, the steering system of the present invention provided to solve the same problem is a steering capable of performing a steering assist operation in which an assist force is applied so as to assist the steering of the steering device using the drive force generated in the drive source. The system has a steering angle detection means capable of detecting the steering angle, and is in a direction opposite to the steering direction on condition that the steering angle is within the terminal range defined on the terminal side of the steerable range. A reverse assist operation in which the assist force is applied is performed.

  In the steering system of the present invention, when the steering angle enters the terminal range of the steerable range, the reverse assist operation is performed so that the assist force in the direction opposite to the steering direction is generated. Therefore, it is possible to simplify the stopper provided at the end of the steerable range of the steering device, or to omit the stopper. As a result, it is possible to reduce the cost or weight of the steering system.

  Further, when the assist operation is performed so that the assist force in the direction opposite to the steering direction is generated within the terminal range, the driver feels that the steering operation is heavy, but for example, the driver suddenly experiences a collision with the stopper described above. I don't feel a shock. Therefore, according to the steering system of the present invention, the steering feeling can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the steering system which can aim at cost reduction or weight reduction can be provided, improving a steering feeling.

It is the schematic diagram which showed typically the structure of the steering system which concerns on one Embodiment of this invention. It is a block diagram which shows the control apparatus employ | adopted in the steering system of FIG. 2 is a Ts-It map employed in the steering system of FIG. 2 is a θ-Ts map employed in the steering system of FIG. 1. It is explanatory drawing which showed the determination method of the assist current in the steering system which concerns on 1st embodiment. It is a graph which shows the relationship of the steering angle in the steering system which concerns on 2nd embodiment, steering torque, assist electric current, and steering thrust. It is explanatory drawing which showed the determination method of the assist current in the steering system which concerns on 2nd embodiment.

≪First embodiment≫
Next, the steering system 10 according to the first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the steering system 10 is roughly divided into a steering device 20 that can be operated by the driver and a control device 30 that controls the operation of the steering device 20.

  The steering device 20 is a steering device provided with a steering 22 (handle). The steering device 20 includes a motor 24 (drive source) that operates using steering of the steering 22 as an input signal. The motor 24 is attached to the center of the steering column. The steering device 20 can generate an assist force for assisting steering by operating the motor 24.

  As shown in FIG. 2, the steering device 20 includes a steering angle detection unit 26 for detecting the steering angle θ of the steering 22 and a steering torque detection unit 27 for detecting the steering torque Ts. In addition to the steering wheel 22, the steering device 20 includes constituent members (not shown) such as a stopper, a rack and pinion mechanism, and a shaft.

  The control device 30 is for controlling the operation of the motor 24. As shown in FIG. 2, the control device 30 can receive output signals from the steering angle detection means 26, the steering torque detection means 27, and the separately provided vehicle speed detection means 28. Further, it is possible to cause the motor 24 to output a current (hereinafter also referred to as “assist current Is”) based on the detection signals input from the detection means 26, 27, and 28.

  The control device 30 can perform a steering assist operation that assists the steering of the steering device using the driving force generated in the drive source. In particular. The steering force can be assisted by driving the steering shaft by operating the motor 24 and transmitting the driving force to a steering rack (not shown).

  More specifically, the control device 30 derives from the steering torque Ts and the vehicle speed Vs detected by the steering torque detection means 27 based on a map as shown in FIG. 3 (hereinafter also referred to as “Ts-It map”). The assist current Is corresponding to the normal assist current It is output to the motor 24. Thereby, the steering force in the steering device 20 can be assisted.

  Here, the relationship between the steering angle θ and the steering torque Ts is indicated by a point P in a map shown in FIG. 4 (hereinafter also referred to as “θ-Ts map”) (hereinafter referred to as “lock region”). If the steering torque Ts is equal to or greater than a predetermined value in a state where the steering angle θ reaches the end range that is near the end of the steerable range, As a condition, the above-described steering assist operation is restricted or prohibited.

  That is, on the condition that the steering angle θ is within the terminal range and the steering torque Ts is equal to or greater than a predetermined value, the assist current Is actually output toward the motor 24 is based on the Ts-It map shown in FIG. Thus, control is performed to reduce the current assist current It to less than or equal to the normal assist current It derived from the above. As a result, the force (steering force) required for the driver to steer can be increased, and an excessively large impact on the steering device 20 side can be avoided.

  More specifically, the control device 30 derives the assist current Is by a method as shown in the explanatory diagram of FIG. 5 and outputs it to the motor 24. That is, the control device 30 derives the assist current Is from the vehicle speed Vs and the steering torque Ts based on the Ts-It map of FIG. Further, it is confirmed whether or not a point P indicating the relationship between the steering torque Ts and the steering angle θ exists in the lock region of the θ-Ts map shown in FIG. As a result, when the point P exists in the lock region, the coefficient k used to derive the assist current Is is determined in the range of 0 <k <1.

  The coefficient k may be defined by any method, but can be determined as follows, for example. That is, a mathematical formula such as the following (Formula 1) is defined in advance, and the coefficient k can be derived from this mathematical formula. In the following (Equation 1), x represents the distance between the boundary line L and the point P forming the boundary of the lock region in the θ-Ts map shown in FIG. F (x) is a function defined such that the coefficient k decreases as the distance x increases.

  k = f (x) (Formula 1)

  On the other hand, when the steering angle θ is outside the terminal range, or when the steering torque Ts is less than the predetermined value even when the steering angle θ is within the terminal range, the coefficient k is set to 1. When the coefficient k is derived in this way, the assist current that is actually output to the motor 24 is obtained by multiplying the normal-time assist current It derived based on the Ts-It map shown in FIG. 3 and the coefficient k. Is is derived. Therefore, when the steering angle θ is within the terminal range and the steering torque Ts is greater than or equal to a predetermined value (when the point P is in the lock region), the coefficient k is smaller than in other cases, The assist current Is is reduced by the amount.

  As described above, in the steering system 10 according to the present embodiment, when the steering torque Ts in the vicinity of the end of the steerable range is equal to or greater than the predetermined value, it is controlled that the steered steering 22 is operated in the vicinity of the end. The assist current Is is determined by the device 30 and is suppressed more than usual. As a result, the steering assist operation is limited, and the force (steering force) required for the driver to steer near the end of the steerable range increases. Therefore, even if steep steering is performed near the end of the steering range of the steering wheel 22, it is possible to prevent an excessively large impact from being applied to the steering device 20 side.

  Further, in the case of a structure in which a member such as a stopper (not shown) is provided at the end of the steerable range as in the steering device 20 illustrated in the present embodiment, the above-described control is executed. It is possible to avoid applying an excessively large impact to a member such as a stopper. Therefore, according to the steering system 10 of the present embodiment, it is possible to simplify the device configuration of the steering device 20 such as adopting a member such as a stopper that is not so high in impact resistance. Further, the steering system 10 can be reduced in cost or weight.

  Further, as in the steering system 10 of the present embodiment, when the steering 22 is steered near the end of the steerable range, the steering assist operation is limited, thereby causing a sudden collision with the stopper. It is possible to prevent the driver from feeling a large impact due to Further, when the steering wheel 22 is gently operated, the steering assist operation is not limited, and the driver does not feel uncomfortable with the steering feeling. Therefore, according to the steering system 10 of the present embodiment, the steering feeling can be improved.

  In the present embodiment, as shown in FIG. 4, the example in which the steering 22 determines whether the operation is performed steeply in the vicinity of the terminal end based on the relationship between the steering angle θ and the steering torque Ts is shown. However, the present invention is not limited to this. Specifically, as shown by a broken line in FIG. 2, a steering speed detecting means 29 for detecting the steering speed Ss of the steering wheel 22 is provided, or the steering torque Ts detected by the steering torque detecting means 27 is calculated. Thus, the steering speed Ss (Ss = dθ / dt) may be derived, and similar control may be performed based on the relationship between the steering speed Ss and the steering angle θ.

  In the present embodiment, an example is shown in which the steering assist operation is limited by setting the coefficient k to a positive number less than 1 when the steering 22 is steered in the vicinity of the steerable range of the steering angle θ. The steering assist operation may be completely prohibited by setting the coefficient k to zero.

<< Second Embodiment >>
Next, the steering system 50 according to the second embodiment of the present invention will be described in detail with reference to the drawings. In the following description, portions common to the steering system 10 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 1, the steering system 50 is roughly divided into a steering device 20 that can be operated by the driver and a control device 60 that controls the operation of the steering device 20, similarly to the steering system 10. Since the steering device 20 has the same configuration as that described above, detailed description thereof is omitted.

  Further, as shown in FIG. 2, the control device 60 is for controlling the operation of the motor 24 in the same manner as the control device 30 described above, and includes a steering angle detection means 26, a steering torque detection means 27, and a vehicle speed detection. Based on the output signal of the means 28, the steering angle θ, the steering torque Ts, and the vehicle speed Vs can be detected. Further, the control device 60 can output a current (hereinafter also referred to as “assist current Is”) to the motor 24 to perform a steering assist operation.

  Similar to the control device 30 described above, the control device 60 generates a normal assist current It derived from the steering torque Ts detected by the steering torque detection means 27 and the vehicle speed Vs based on the Ts-It map shown in FIG. A corresponding assist current Is is output to the motor 24. Thereby, the steering force in the steering device 20 can be assisted.

  Specifically, when the magnitude of the steering torque Ts is A and the magnitude of the driving force generated in the motor 24 by the assist current Is is B as shown in FIG. 6, the steering angle θ is near the end of the steerable range. When the angle is less than the lock setting angle θL set to, a thrust having a magnitude C that is the sum of A and B acts on the steering 22.

  When the steering angle θ has reached the lock setting angle θL, by performing a reverse assist operation in which an assist force is applied in the opposite direction to the case where the steering angle θ is less than the lock setting angle θL, Steering is restricted. That is, as shown in FIG. 6, the assist current Is (hereinafter referred to as “assist current in this case is particularly expressed as“ Also referred to as “reverse assist current Ir”. As a result, a driving force B having a direction and magnitude that cancels the magnitude A of the steering torque Ts is generated by the motor 24. Therefore, when the steering angle θ has reached the lock setting angle θL, the thrust C acting on the steering 22 becomes substantially zero.

  More specifically, the control device 60 derives the assist current Is by a method as shown in the explanatory diagram of FIG. 7 and outputs it to the motor 24. That is, the control device 60 derives the normal assist current It from the vehicle speed Vs and the steering torque Ts based on the Ts-It map of FIG. Separately from this, it is confirmed whether or not the absolute value of the steering angle θ is equal to or larger than the lock setting angle θL. As a result, when the absolute value of the steering angle θ is less than the lock setting angle θL, an assist current Is corresponding to the normal assist current It derived based on the Ts-It map is applied to the motor 24 to perform steering. Execute assist operation.

  On the other hand, when the absolute value of the steering angle θ is less than the lock setting angle θL, the reverse assist operation is executed. That is, when the absolute value of the steering angle θ is less than the lock setting angle θL, the motor 24 is controlled so that the steering torque Ts acting on the steering device 20 can be canceled by the driving force generated in the motor 24. On the other hand, an assist current Is (reverse assist current Ir) is applied. In other words, the reverse assist current Ir is applied to the motor 24 so as to generate a driving force having a magnitude corresponding to the steering torque Ts and acting in the direction opposite to the steering torque Ts. As a result, the steering wheel 22 cannot be operated beyond the predetermined lock setting angle θL.

  In the steering system 50 of the present embodiment, when the steering angle θ falls within the range of the lock setting angle θL or more, a reverse assist operation is performed so that an assist force in a direction opposite to the steering direction is generated, and the steering 22 The function as a pseudo-stopper that restricts the operation is exhibited. Therefore, in the steering system 50, it is possible to simplify a stopper (not shown) provided at the end of the steerable range of the steering device 20, or to omit the stopper. As a result, the steering system 50 can be reduced in cost or weight.

  In addition, when the steering assist operation is performed so that an assist force in a direction opposite to the steering direction is generated within the terminal range, the driver feels that the steering operation of the steering wheel 22 is heavy. I do not feel any shock. Therefore, according to the steering system 10 of the present embodiment, the steering feeling can be improved.

  The steering systems 10 and 50 described above each employ a rack and pinion type steering device 20, but the steering device 20 may be a ball nut type.

  INDUSTRIAL APPLICABILITY The steering system of the present invention can be used in all steering systems capable of performing a steering assist operation that applies an assist force so as to assist the steering of the steering device using the driving force generated in the drive source.

10, 50 Steering system 20 Steering device 22 Steering 24 Motor (drive source)
26 Steering angle detecting means 27 Steering torque detecting means 28 Vehicle speed detecting means 29 Steering speed detecting means 30, 60 Controller Ts Steering torque Vs Vehicle speed Ss Steering speed θ Steering angle

Claims (2)

In a steering system capable of performing a steering assist operation in which an assist force is applied so as to assist the steering of the steering device using a driving force generated in a drive source,
A steering speed detecting means capable of detecting a steering speed and / or a steering torque detecting means capable of detecting a steering torque;
A steering system characterized in that the steering assist operation is restricted or prohibited on condition that a steering speed and / or a steering torque in the vicinity of the end of the steerable range is a predetermined value or more. In a steering system capable of performing a steering assist operation in which an assist force is applied so as to assist the steering of the steering device using a driving force generated in a drive source,
Steering angle detection means capable of detecting the steering angle;
A reverse assist operation for applying an assist force in a direction opposite to the steering direction is performed on the condition that the steering angle is within a terminal range defined on the terminal side of the steerable range. Steering system.

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