JP2009096325A - Malfunction detecting device for steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a malfunction detecting device capable of detecting malfunction of a steering device even if the number of angle sensors is reduced. <P>SOLUTION: The malfunction detecting device 5 detects malfunction of the steering device 1, in which the transmission gear ratio of the rotation angle θh of a steering wheel 4 to the turning angle of a turning wheel is varied by a variable gear ratio mechanism 2, and the assisting force for steering is generated by an electric power steering 3. The malfunction detecting device 5 includes a computing part 5a for computing the rotational speed dθeps/dt of an assist motor 3b, the source of the assisting force, used in the electric power steering 3, based on a motor current i and applied voltage V of the assist motor 3b; and a determination part 5b for determining the malfunction based on the rotational speed dθm/dt of a differential gear motor 2a used in the variable gear ratio mechanism 2 to vary the transmission gear ratio by the rotation, the rotational speed dθh/dt of the steering wheel 4 and the computed rotational speed dθeps/dt of the assist motor 3b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention changes the transmission gear ratio of the rotation angle of the steering wheel with respect to the turning angle of the steered wheels by the variable gear ratio mechanism, and detects a failure of the steering device that generates an assist force during steering by the electric power steering. The present invention relates to a detection device.

  Conventionally, a steering apparatus including a variable gear ratio mechanism and an electric power steering has been proposed. According to the variable gear ratio mechanism, by setting the transmission gear ratio (= steering wheel angle / steering angle) to a small (quick ratio) setting in a low vehicle speed range such as parking operation, the steering handle can be rotated slightly. Since the steered wheels can be steered greatly, the operation burden on the driver is reduced, and convenience can be improved. At high vehicle speeds, the transmission gear ratio is set to a large value (slow ratio), so even if the steering wheel is rotated a lot, the steered wheels only turn slightly, improving the yaw rate response characteristics and improving vehicle stability. Can be improved.

  Further, according to the electric power steering, an assisting force is generated, so that the steered wheels can be steered only by lightly operating the steering handle.

  In a steering apparatus including such a variable gear ratio mechanism and an electric power steering, usually three angle sensors are used. The first is a handle angle sensor for measuring the rotation angle of the steering handle, and the second is a rotation angle of a differential gear motor that changes the transmission gear ratio by rotating with a variable gear ratio mechanism. The third is a pinion angle sensor for measuring the rotation angle of a pinion of a rack and pinion type gear box used for electric power steering.

Conventionally, it has been proposed to compare the rotation angles measured by each of the three angle sensors in order to detect the failure of these angle sensors, in particular, when detecting the failure of the steering device ( For example, see Patent Document 1).
JP 2003-306159 A

  However, installing three angle sensors for detecting each rotation angle increases the cost ratio of the angle sensor in the steering device and increases the number of in-vehicle wires used for communication with the angle sensor. It was an obstacle to realizing a steering device at a lower price.

  Therefore, an object of the present invention is to provide a failure detection device that can detect a failure of a steering device even if the number of angle sensors is reduced.

The present invention changes the transmission gear ratio of the rotation angle of the steering wheel with respect to the turning angle of the steered wheels by the variable gear ratio mechanism, and detects a failure of the steering device that generates an assist force during steering by the electric power steering. In the detection device,
A calculation unit for calculating a rotation speed of an assist motor used for the electric power steering and serving as a generation source of the auxiliary force from a motor current and an applied voltage of the assist motor;
From the rotational speed of the differential gear motor that is used in the variable gear ratio mechanism and changes the transmission gear ratio by rotating, the rotational speed of the steering handle, and the calculated rotational speed of the assist motor, the failure occurs. And a determination unit that performs the determination.

  According to the present invention, the rotational speed of the steering wheel can be calculated by time differentiation of the steering wheel rotation angle measured using the steering wheel angle sensor, and the rotational speed of the differential gear motor can be calculated using the differential gear. Using the motor angle sensor, the differential gear rotation angle measured by the differential gear motor angle sensor can be calculated by time differentiation.

  Further, the rotation speed of the assist motor can be calculated by the calculation unit without using an angle sensor.

  For this reason, the failure of the steering device can be detected only by using at most two angle sensors (the steering wheel angle sensor and the differential gear motor angle sensor).

In addition, the present invention detects a failure of the steering device that changes the transmission gear ratio of the rotation angle of the steering wheel with respect to the turning angle of the steered wheels by the variable gear ratio mechanism and generates an assist force during steering by the electric power steering. In the failure detection device to
A calculation unit that calculates a rotation angle of an assist motor that is used in the electric power steering and serves as a source of the auxiliary force, from a motor current of the assist motor and an applied voltage;
From the rotation angle of the differential gear motor that is used in the variable gear ratio mechanism and changes the transmission gear ratio by rotating, the rotation angle of the steering handle, and the calculated rotation angle of the assist motor, the failure occurs. And a determination unit that performs the determination.

  According to the present invention, the rotation angle of the steering handle can be measured by a handle angle sensor, and the rotation angle of the differential gear motor can be measured by a differential gear motor angle sensor.

  Further, the rotation angle of the assist motor can be calculated by the calculation unit without using an angle sensor.

  For this reason, the failure of the steering device can be detected only by using at most two angle sensors (the steering wheel angle sensor and the differential gear motor angle sensor).

  ADVANTAGE OF THE INVENTION According to this invention, even if it reduces the number of angle sensors, the failure detection apparatus which can detect the failure of a steering apparatus can be provided.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

  In FIG. 1, the block diagram of the steering device 1 provided with the failure detection apparatus 5 which concerns on embodiment of this invention is shown. The steering device 1 has a steering handle 4, a variable gear ratio mechanism 2, and an electric power steering 3 in addition to the failure detection device 5.

  The steering handle 4 is provided with a handle angle sensor 4a capable of measuring the handle rotation angle θh of the steering handle 4. The measured handle rotation angle θh is transmitted to the failure detection device 5.

  The variable gear ratio mechanism 2 changes the transmission gear ratio of the rotation angle θh of the steering handle 4 with respect to the turning angle of the steered wheel and the differential gear 2b connected to the steering handle 4 and the rack and pinion type gear box 3a. Therefore, the difference between the differential gear motor 2a that rotates the differential gear 2b, the variable gear ratio mechanism ECU 2c that outputs a control signal for rotating the differential gear motor 2a, and the differential gear motor 2a. And a differential gear motor angle sensor 2d for measuring the dynamic gear motor rotation angle θm.

  The variable gear ratio mechanism ECU 2c outputs a control signal so that the transmission gear ratio can be set small (quick ratio) in the low vehicle speed range according to the vehicle speed of the vehicle. A control signal is output so that the transmission gear ratio can be set large (slow ratio). The differential gear motor rotation angle θm measured by the differential gear motor angle sensor 2 d is transmitted to the failure detection device 5.

  The electric power steering 3 includes a rack and pinion gear box 3a that changes the turning angle of the steered wheels, an EPS motor (assist motor) 3b that is a source of assisting force during steering, and an EPS motor 3b according to the vehicle speed. EPS ECU3c to control.

  The EPS ECU 3c sets a motor applied voltage V and supplies it to the EPS motor 3b in order to cause the EPS motor 3b to generate a steering assist torque. At that time, the EPS ECU 3c measures the motor current i flowing through the EPS motor 3b.

  Further, the values of the motor current i and the motor applied voltage V are transmitted to the failure detection device 5.

  The rotation angle θp of the pinion in the rack and pinion gear box 3a is in a mechanical constraint relationship with respect to the steering wheel rotation angle θh and the differential gear motor rotation angle θm, and will be described in detail later. There is a relational expression based on a mechanical constraint relationship between the handle rotation angle θh and the differential gear motor rotation angle θm.

  Further, there is a mechanical constraint between the rotation angle θp of the pinion and the rotation angle θeps of the EPS motor 3b. As will be described in detail later, the rotation angle θp of the pinion and the rotation angle θeps of the EPS motor 3b There is also a relational expression based on a mechanical constraint relationship between them.

  The failure detection device 5 includes a calculation unit 5a, a first determination unit 5b, and a second determination unit 5c, and outputs a first failure signal and a second failure signal. In the vehicle, an alarm is issued based on at least one of the first failure signal and the second failure signal, and the driver of the vehicle can recognize the failure of the steering device 1.

  FIG. 2 shows a data flow in the failure detection apparatus 5 according to the embodiment of the present invention. The calculation unit 5a, the first determination unit 5b, and the second determination unit 5c will be described in detail with reference to FIG.

  First, the handle rotation angle θh is transmitted from the measured handle angle sensor 4 a to the failure detection device 5 and acquired by the failure detection device 5. The handle rotation angle θh is time-differentiated by the first determination unit 5b, and the first determination unit 5b calculates the handle rotation speed (dθh / dt).

  Similarly, the differential gear motor rotation angle θm is transmitted from the measured differential gear motor angle sensor 2 d to the failure detection device 5 and acquired by the failure detection device 5. The differential gear motor rotation angle θm is time-differentiated by the first determination unit 5b to calculate the differential gear motor rotation speed (dθm / dt).

The values of the motor current i and the motor applied voltage V are transmitted from the EPS ECU (3c) to the failure detection device 5 and acquired by the failure detection device 5. Generally, Formula 1 which is an electrical relational expression is established among the rotational speed (dθeps / dt) of the EPS motor 3b, the motor current i, and the motor applied voltage V. Here, R [Ω] is a circuit resistance, L [H] is a circuit inductance, and k [Vs / rad] is a counter electromotive voltage constant. Equation 1 can be transformed as Equation 2.

L × di / dt + R × i = V−k × dθeps / dt Equation 1
dθeps / dt = (V−L × di / dt−R × i) / k Equation 2

(In addition to the method of Formula 2, the applied voltage V, the motor current i, the motor rotation speed dθeps / dt are actually measured, and the data is prepared in advance in the failure detection device 5 as map data. (A method of estimating the motor rotation speed dθeps / dt from the applied voltage V and the motor current i may be used.)

  The calculation unit 5a calculates the rotational speed (dθeps / dt) of the EPS motor 3b from the motor current i of the EPS motor 3b and the motor applied voltage V using Equation 2.

If Equation 2 is integrated over time, Equation 3 can be derived. The calculation unit 5a calculates the rotation angle θeps of the EPS motor 3b from the motor current i and the motor applied voltage V of the EPS motor 3b using Equation 3.

θeps = (1 / k) × ∫ (V−L × di / dt−R × i) dt Equation 3

(Failure judgment by the second judgment part)
First, the failure determination in the second determination unit 5c will be described. The second determination unit 5c determines a failure from the rotation angle θh of the steering handle 4, the rotation angle θm of the differential gear motor 2a, and the rotation angle θeps of the EPS motor 3b. In general, Equation 4 is established from the mechanical constraint relationship among the rotation angle θp of the pinion, the rotation angle θh of the steering handle 4, and the rotation angle θm of the differential gear motor 2a. Here, a and b are constants.

Further, Formula 5 is also established between the rotation angle θp of the pinion and the rotation angle θeps of the EPS motor 3b from the mechanical constraint relationship. Here, c is a constant.

θp = a × θh + b × θm Expression 4
θp = c × θeps (5)

  First, the second determination unit 5c calculates the pinion rotation angle θp from the rotation angle θh of the steering handle 4 and the rotation angle θm of the differential gear motor 2a using Equation 4. Next, the second determination unit 5 c calculates the pinion rotation angle θp from the rotation angle θeps of the EPS motor 3 b using Equation 5.

  The second determination unit 5c determines whether the difference between the rotation angle θp of the pinion derived from Equation 4 and the rotation angle θp of the pinion derived from Equation 5 is equal to or less than a set threshold (= second set threshold). do. If the value is equal to or smaller than the second set threshold value, it is considered that the values of both the pinion rotation angle θp derived from Equation 4 and the pinion rotation angle θp derived from Equation 5 are substantially the same, and the occurrence of a failure in the steering device 1 is considered. The second failure signal shown is not output.

  On the other hand, if the second set threshold value is exceeded, it is considered that the values of both the pinion rotation angle θp derived from Equation 4 and the pinion rotation angle θp derived from Equation 5 are significantly different, and the second failure signal is Output.

(Failure determination by the first determination unit)
Next, the failure determination in the first determination unit 5b will be described. The first determination unit 5b fails based on the rotational speed (dθh / dt) of the steering handle 4, the rotational speed (dθm / dt) of the differential gear motor 2a, and the rotational speed (dθeps / dt) of the EPS motor 3b. Judgment is made. Differentiating Equation 4 with respect to time, we can derive Equation 6. Further, when the equation 5 is differentiated with respect to time, the equation 7 can be derived.

dθp / dt = a × dθh / dt + b × dθm / dt Equation 6
dθp / dt = c × dθeps / dt Equation 7

  First, the first determination unit 5b first uses Equation 6 to calculate the rotation speed of the pinion (dθh / dt) and the rotation speed (dθm / dt) of the differential gear motor 2a (dθm / dt). dθp / dt) is calculated. Next, the first determination unit 5b calculates the pinion rotation speed (dθp / dt) from the rotation speed (dθeps / dt) of the EPS motor 3b using Expression 7.

  The first determination unit 5b determines that the difference between the rotation speed of the pinion derived from Equation 6 (dθp / dt) and the rotation speed of the pinion derived from Equation 7 (dθp / dt) is a set threshold (= first setting). It is determined whether or not it is equal to or less than (threshold). If it is less than or equal to the first set threshold, it is considered that both the rotation speed of the pinion derived from Equation 6 (dθp / dt) and the rotation speed of the pinion derived from Equation 7 (dθp / dt) are substantially the same, A first failure signal indicating the occurrence of a failure in the steering device 1 is not output.

  On the other hand, if the first set threshold is exceeded, the values of both the pinion rotation speed (dθp / dt) derived from Equation 6 and the pinion rotation speed (dθp / dt) derived from Equation 7 are significantly different. Considering this, the first failure signal is output.

  Thus, the rotation angle θeps and the rotation speed (dθeps / dt) of the EPS motor 3b can be calculated by the calculation unit 5a without using an angle sensor. For this reason, the failure of the steering device 1 can be detected only by using at most two angle sensors (the handle angle sensor 4a and the differential gear motor angle sensor 2d).

It is a lineblock diagram of a steering device provided with a failure detection device concerning an embodiment of the present invention. It is a figure which shows the data flow in the failure detection apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering device 2 Variable gear ratio mechanism 2a Differential gear motor 2b Differential gear 2c Variable gear ratio mechanism ECU
2d Motor angle sensor for differential gear 3 Electric power steering 3a Rack & pinion type gear box 3b EPS motor (assist motor)
3c EPS ECU
4 Steering handle 4a Handle angle sensor 5 Failure detection device 5a Calculation unit 5b First determination unit 5c Second determination unit

Claims (2)

In the failure detection device that detects a failure of the steering device that changes the transmission gear ratio of the rotation angle of the steering wheel with respect to the turning angle of the steered wheels by the variable gear ratio mechanism and generates an assist force during steering by the electric power steering,
A calculation unit for calculating a rotation speed of an assist motor used for the electric power steering and serving as a generation source of the auxiliary force from a motor current and an applied voltage of the assist motor;
From the rotational speed of the differential gear motor that is used in the variable gear ratio mechanism and changes the transmission gear ratio by rotating, the rotational speed of the steering handle, and the calculated rotational speed of the assist motor, the failure occurs. A failure detection device for a steering device, comprising: a determination unit configured to determine In the failure detection device that detects a failure of the steering device that changes the transmission gear ratio of the rotation angle of the steering wheel with respect to the turning angle of the steered wheels by the variable gear ratio mechanism and generates an assist force during steering by the electric power steering,
A calculation unit that calculates a rotation angle of an assist motor that is used in the electric power steering and serves as a source of the auxiliary force, from a motor current of the assist motor and an applied voltage;
From the rotation angle of the differential gear motor that is used in the variable gear ratio mechanism and changes the transmission gear ratio by rotating, the rotation angle of the steering handle, and the calculated rotation angle of the assist motor, the failure occurs. A failure detection device for a steering device, comprising: a determination unit configured to determine

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