JP2019172080A - Electric power steering device and management system for electric power steering device - Google Patents

Abstract

To grasp a degree of deterioration of a transmission part in an electric power steering device with an inexpensive configuration.SOLUTION: An electric power steering device 100 comprises: a controller 60 which controls an electric motor 50 on the basis of a steering torque and a motor rotation angle detected by a torque sensor 51 and a rotation angle sensor 52; first and second transmission parts 41, 42 which transmit a torque acting on a steering shaft 20 and a torque of the electric motor 50 to a rack shaft 30; an estimation part 71 which estimates a state quantity of the first and second transmission parts 41, 42 on the basis of the steering torque and the motor rotation angle detected by the torque sensor 51 and the rotation angle sensor 52; and a degradation degree calculation part 72 which calculates a degree of degradation of the first and second transmission parts 41, 42 on teh basis of the state quantity estimated by the estimation part 71.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric power steering device and a management system for the electric power steering device.

  As a vehicle steering device, Patent Literature 1 discloses an electric power steering device including an electric motor that generates a steering assist torque. The electric power steering apparatus includes a torque sensor that detects torque applied to the torsion bar, and a rotation angle sensor that detects a rotation angle of the electric motor. The electric motor is detected by the torque sensor and the rotation angle sensor. It is controlled according to the torque and the rotation angle. Torque generated by the electric motor is transmitted to the pinion shaft through the worm gear and the worm wheel, and is further transmitted to the rack shaft through the pinion of the pinion shaft and the rack of the rack shaft. As a result, the rack shaft moves in the axial direction, and appropriate steering assistance according to the driver's steering is realized.

Japanese Patent Laid-Open No. 2006-179748

  In an electric power steering apparatus, a transmission unit that transmits torque such as a worm gear, a worm wheel, a pinion, and a rack causes wear and the like to deteriorate due to the transmission of torque. The mechanical characteristics such as viscous resistance and equivalent resistance of the transmission unit change with the deterioration of the transmission unit. To maintain the initial steering feeling, the electric motor is controlled according to the degree of deterioration of the transmission unit. It is necessary to change the control parameters for

  Further, the transmission part may be damaged when it is significantly deteriorated. Therefore, it is desirable to manage the replacement time of the electric power steering device based on the degree of deterioration of the transmission unit.

  For these reasons, it is required to grasp the degree of deterioration of the transmission unit in the electric power steering apparatus.

  It is known that the degree of deterioration of the transmission unit is calculated from the amount of state of the transmission unit such as the torque acting on the transmission unit, the displacement speed of the transmission unit, and the amount of displacement of the transmission unit. For this reason, as a method of grasping the degree of deterioration of the transmission unit, it is conceivable to provide a sensor for detecting these state quantities in the electric power steering apparatus.

  However, when the electric power steering apparatus disclosed in Patent Document 1 is provided with a sensor that detects these state quantities, a sensor other than the torque sensor and the rotation angle sensor for controlling the electric motor is connected to the electric power steering apparatus. It will be provided in the steering device. Therefore, the number of sensors increases and the cost of the electric power steering device increases.

  An object of this invention is to grasp | ascertain the deterioration degree of the transmission part in an electric power steering apparatus with an inexpensive structure.

  The first invention provides a steering shaft, a torsion bar, a torque detection unit, an electric motor, a rotation angle detection unit, a control unit for controlling the electric motor, a torque acting on the steering shaft, and a torque of the electric motor. A transmission unit that transmits to the rack shaft, an estimation unit that estimates a state quantity of the transmission unit based on a steering torque detected by the torque detection unit, and a motor rotation angle detected by the rotation angle detection unit; and an estimation unit A deterioration degree calculation unit that calculates a deterioration degree of the transmission unit based on the estimated state quantity.

  In the first invention, the state quantity of the transmission unit is estimated based on the steering torque and the motor rotation angle detected for the control of the electric motor by the control unit. Therefore, the detection unit for controlling the electric motor and the detection unit for calculating the deterioration degree of the transmission unit can be shared. Therefore, an increase in the detection unit of the electric power steering device can be prevented.

  The second aspect of the present invention further includes a steering angle detection unit, and the estimation unit is detected by the steering torque detected by the torque detection unit, the motor rotation angle detected by the rotation angle detection unit, and the steering angle detection unit. The state quantity of the transmission unit is estimated based on the steering angle.

  In the second invention, since three detection amounts are used in the estimation unit, it is possible to construct a model used for estimating the state amount in detail, compared with the case where only two detection amounts are used in the estimation unit. it can. Therefore, the state quantity of the transmission unit can be estimated more accurately, and the deterioration degree of the transmission unit can be grasped more accurately.

  In the third invention, the estimation unit estimates the torque in the transmission unit as a state quantity, and the deterioration degree calculation unit calculates the maximum value of the load based on the estimated torque, and calculates the deterioration degree of the transmission unit. .

  In the third aspect of the invention, it is possible to grasp the degree of overload deterioration caused by receiving a temporary excessive load.

  In the fourth aspect of the invention, the estimation unit further estimates the displacement speed and displacement amount of the transmission unit as state quantities, and the deterioration degree calculation unit calculates the number of repetitions and the allowable number of repetitions. Based on the number of times, the deterioration degree of the transmission unit is calculated.

  In the fourth invention, it is possible to grasp the degree of repeated load deterioration caused by repeatedly receiving a load.

  In the fifth invention, the control unit changes a control parameter for controlling the electric motor based on the deterioration degree calculated by the deterioration degree calculation unit.

  In the fifth aspect of the invention, the electric motor is controlled so as to generate torque in anticipation of a change in the load of the transmission unit accompanying a change in the degree of deterioration. Therefore, the steering feeling can be maintained.

  In a sixth aspect of the present invention, when the determination unit that determines whether or not the electric power steering device needs to be replaced and the determination unit determine that the electric power steering device needs to be replaced based on the calculated degree of deterioration. And an informing unit for informing that it is time to replace the electric power steering device.

  In the sixth aspect of the invention, whether or not the electric power steering device needs to be replaced is determined based on the calculated degree of deterioration. Therefore, it is possible to more appropriately manage the replacement time of the electric power steering device.

  ADVANTAGE OF THE INVENTION According to this invention, the deterioration degree of the transmission part in an electric power steering apparatus can be grasped | ascertained with an inexpensive structure.

FIG. 1 is a configuration diagram of an electric power steering apparatus and a management system according to the first embodiment of the present invention. FIG. 2 is a block diagram of the electric power steering apparatus and management system according to the first embodiment of the present invention. FIG. 3 is a block diagram illustrating details of the deterioration degree calculation unit. FIG. 4 is a flowchart for explaining processing performed by the excessive load deterioration degree calculation unit. FIG. 5 is a flowchart for explaining processing performed by the repeated load deterioration degree calculation unit. FIG. 6 is a flowchart for explaining processing performed by the determination unit. FIG. 7 is a configuration diagram of an electric power steering apparatus and a management system according to the second embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
First, the electric power steering apparatus 100 and the management system 1000 for the electric power steering apparatus 100 according to the first embodiment of the present invention will be described with reference to FIGS. The electric power steering apparatus 100 is mounted on a vehicle and assists the operation of the steering wheel 10 by a driver (hereinafter referred to as “steering operation”). The management system 1000 manages the replacement time of the electric power steering device 100.

  As shown in FIG. 1, the electric power steering apparatus 100 includes a steering shaft 20 connected to the steering wheel 10 and a rack shaft 30 that steers the wheel 1 as the steering shaft 20 rotates. The rack shaft 30 is connected to the wheel 1 via the knuckle arm 31, and the wheel 1 is steered by the displacement of the rack shaft 30.

  The steering shaft 20 includes an input shaft 21 that rotates in response to a steering operation by a driver, an output shaft 22 that displaces the rack shaft 30, and a torsion bar 23 that connects the input shaft 21 and the output shaft 22. The

  The output shaft 22 and the rack shaft 30 are connected to each other via the first transmission portion 41. The first transmission unit 41 includes a pinion gear 41 a provided on the output shaft 22 and a rack gear 41 b provided on the rack shaft 30. The pinion gear 41a and the rack gear 41b mesh with each other, and the torque of the output shaft 22 is converted into an axial load of the rack shaft 30 via the pinion gear 41a and the rack gear 41b and transmitted to the rack shaft 30. Thereby, the rack shaft 30 is displaced in the axial direction by the transmitted torque, and the wheel 1 is steered.

  The electric power steering apparatus 100 further includes an electric motor 50 that is driven in accordance with a steering operation. The output shaft of the electric motor 50 is connected to the output shaft 22 of the steering shaft 20 via the second transmission portion 42.

  The second transmission unit 42 includes a worm shaft 42 a provided on the output shaft of the electric motor 50 and a worm wheel 42 b provided on the output shaft 22. The worm shaft 42a and the worm wheel 42b mesh with each other, and the torque of the electric motor 50 is transmitted to the output shaft 22 through the worm shaft 42a and the worm wheel 42b. The torque transmitted from the electric motor 50 to the output shaft 22 is further transmitted to the rack shaft 30 through the pinion gear 41a and the rack gear 41b.

  As described above, the electric power steering apparatus 100 is a so-called column type electric power steering apparatus that assists the steering operation by transmitting the torque of the electric motor 50 to the rack shaft 30 through the output shaft 22.

  The electric motor 50 is controlled by a controller 60 as a control unit. The controller 60 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read-Only Memory) that stores a control program executed by the CPU, and a RAM (Random Access Memory) that stores arithmetic results of the CPU. And a microcomputer including the above. The controller 60 may be composed of a single microcomputer or a plurality of microcomputers.

  In addition, the electric power steering apparatus 100 includes a torque sensor 51 as a torque detection unit that detects a steering torque acting on the torsion bar 23, and a rotation angle sensor 52 as a rotation angle detection unit that detects the rotation angle of the electric motor 50. And a steering angle sensor 53 as a steering angle detection unit for detecting a rotation angle of the steering wheel 10 (hereinafter also referred to as “steering angle”). Signals output from the torque sensor 51, the rotation angle sensor 52, and the steering angle sensor 53 are input to the controller 60.

  As shown in FIG. 2, the controller 60 includes an auxiliary torque calculation unit 60a, a correction unit 60b, and a current target value calculation unit 60c. The auxiliary torque calculation unit 60 a calculates torque necessary for assisting the steering operation (hereinafter referred to as “auxiliary torque”) based on signals input from the torque sensor 51, the rotation angle sensor 52, and the steering angle sensor 53. .

  The correction unit 60b corrects the calculated auxiliary torque based on a control parameter for controlling the electric motor 50. The control parameter is determined by mechanical characteristics (for example, friction) of the first and second transmission units 41 and 42. Therefore, it is possible to drive the electric motor 50 in anticipation of loads on the first and second transmission units 41 and 42.

  The current target value calculation unit 60c calculates a target value of the magnitude of the current supplied to the electric motor 50 based on the corrected auxiliary torque. The calculated current target value is input to the current supply unit 61, and a current having a magnitude based on the current target value is supplied from the current supply unit 61 to the electric motor 50.

  Thus, the controller 60 controls the electric motor 50 according to the steering torque, the motor rotation angle, and the steering angle detected by the torque sensor 51, the rotation angle sensor 52, and the steering angle sensor 53, respectively. Therefore, a steering operation with a desired steering feeling is possible.

  By the way, the mechanical characteristics such as the viscous resistance and equivalent resistance of the first and second transmission parts 41 and 42 change as the first and second transmission parts 41 and 42 deteriorate. Therefore, in order to maintain a desired steering feeling, it is necessary to grasp the degree of deterioration of the first and second transmission units 41 and 42 and change the control parameter in the correction unit 60b based on the degree of deterioration.

  Further, when the first and second transmission units 41 and 42 are significantly deteriorated, it is desirable to replace the electric power steering device 100. In order to appropriately manage the replacement time of the electric power steering apparatus 100, it is necessary to grasp the degree of deterioration of the first and second transmission units 41 and 42.

  In the electric power steering device 100, the desired steering feeling is maintained and the replacement time of the electric power steering device 100 is managed by grasping the degree of deterioration of the first and second transmission parts 41 and 42 by the configuration described later. is doing. Hereinafter, a configuration for grasping the degree of deterioration of the first and second transmission units 41, 42, a configuration for maintaining the steering feeling, and a configuration for managing the replacement timing of the electric power steering device 100 will be described in detail. Describe.

  First, the structure for grasping | ascertaining the degradation degree of the 1st and 2nd transmission parts 41 and 42 is demonstrated with reference to FIGS.

  As shown in FIG. 1, the electric power steering device 100 calculates an estimation unit 71 that estimates the state quantities of the first and second transmission units 41 and 42 and the degree of deterioration of the first and second transmission units 41 and 42. A deterioration degree calculation unit 72. Similar to the controller 60, the estimation unit 71 and the deterioration degree calculation unit 72 are configured by a microcomputer. The estimation unit 71 and the deterioration degree calculation unit 72 may be configured by a microcomputer that configures the controller 60, or may be configured by a microcomputer that is different from the microcomputer that configures the controller 60.

  As shown in FIG. 2, the estimation unit 71 is configured to generate torques acting on the first and second transmission units 41 and 42 based on signals input from the torque sensor 51, the rotation angle sensor 52, and the rudder angle sensor 53. The displacement speed and displacement amount of the first and second transmission units 41 and 42 are estimated as state quantities. A method for estimating these torque, displacement speed, and displacement as state quantities will be described later.

  The deterioration level calculation unit 72 calculates the deterioration levels of the first and second transmission units 41 and 42 based on the estimated torque, displacement speed, and displacement amount. The deterioration of the first and second transmission parts 41 and 42 includes an excessive load deterioration caused by receiving a temporary excessive load and a repeated load deterioration caused by repeatedly receiving a load. 72 calculates both the excessive load deterioration degree and the repeated load deterioration degree.

  Specifically, as shown in FIG. 3, the deterioration degree calculation unit 72 includes an overload deterioration degree calculation unit 72a that calculates an overload deterioration degree, and a repeated load deterioration degree calculation unit 72b that calculates a repeated load deterioration degree. It is equipped with. Below, the process performed by the excessive load deterioration degree calculation part 72a and the repeated load deterioration degree calculation part 72b is explained in full detail.

  Here, a process for calculating the degree of deterioration of the pinion gear 41a of the first transmission unit 41 will be described. The process for calculating the degree of deterioration of the rack gear 41b of the first transmission part 41 and the worm shaft 42a and the worm wheel 42b of the second transmission part 42 is substantially the same as the process for calculating the degree of deterioration of the pinion gear 41a. Omitted.

  First, the process performed by the excessive load deterioration degree calculation unit 72a will be described with reference to FIG.

  In step S401, the torque estimated by the estimating unit 71 is acquired. In step S402, a load acting on the teeth of the pinion gear 41a is calculated based on the acquired torque. Specifically, the load acting on the teeth is calculated by dividing the acquired torque by the radius of the reference pitch circle of the pinion gear 41a. The calculated load corresponds to the circumferential force on the reference pitch circle. The diameter of the reference pitch circle is a value determined by the specifications of the pinion gear 41a and is known.

  In step S403, the calculated load data is stored in a storage unit (not shown). The storage unit stores data of loads calculated in the past. In step S403, the calculated load data is further stored in the storage unit.

  In step S404, the maximum value of the load acting on the teeth of the pinion gear 41a is calculated based on a plurality of load data stored in the storage unit. The maximum value of the calculated load corresponds to an excessive load temporarily applied to the teeth of the pinion gear 41a. For example, when the wheel 1 rides on an obstacle such as a curb and receives an impact, the pinion gear 41a The applied load.

  In step S405, the excessive load deterioration degree of the pinion gear 41a is calculated based on the calculated maximum value of the load. Specifically, the calculated maximum value of the load is calculated by dividing the maximum value of the calculated load by the bending strength of the teeth of the pinion gear 41a to calculate the degree of excessive load deterioration due to the bending of the teeth. Is divided by the tooth surface strength of the pinion gear 41a to calculate an overload deterioration degree due to tooth surface damage.

  The bending strength of the teeth of the pinion gear 41a is a value calculated from the specification of the pinion gear 41a by, for example, the Lewis formula, and is known. Further, the tooth surface strength of the pinion gear 41a is a value calculated from the specifications of the pinion gear 41a by, for example, the Hertz formula, and is known.

  As described above, the overload deterioration degree is calculated, and the process in the overload deterioration degree calculation unit 72a ends.

  Next, processing performed by the repeated load deterioration degree calculation unit 72b will be described with reference to FIG.

  In step S501, the torque, the displacement speed, and the displacement amount estimated by the estimation unit 71 are acquired. The obtained displacement speed and displacement amount are respectively the displacement speed and displacement amount in the circumferential direction of the pinion gear 41a, that is, the rotation speed and rotation angle of the pinion gear 41a.

  In step S502, an average value of loads acting on the teeth of the pinion gear 41a is calculated based on the acquired torque. Specifically, as in steps S402 and S403 shown in FIG. 4, the load acting on the teeth is calculated, and the load data is stored in the storage unit. Thereafter, an average value of loads acting on the teeth of the pinion gear 41a is calculated based on a plurality of load data stored in the storage unit. The calculated average value of the load is an average value of the load repeatedly applied to the teeth of the pinion gear 41a.

  In step S503, an average value of the rotation speeds of the pinion gear 41a is calculated based on the acquired rotation speed. Specifically, first, the acquired rotation speed is stored in a storage unit (not shown). The storage unit stores rotational speed data acquired in the past, and the acquired rotational speed data is further stored in the storage unit. Next, an average value of the rotational speeds of the pinion gear 41a is calculated based on a plurality of rotational speed data stored in the storage unit.

  In step S504, based on the calculated average value of the load and the average value of the rotation speed, an allowable number of repetitions for the bending strength of the teeth and an allowable number of repetitions for the tooth surface strength are calculated. The allowable number of repetitions for the bending strength of the teeth is calculated by, for example, the Lewis equation from the specification of the pinion gear 41a, the average value of the load, and the average value of the rotation speed. Further, the allowable number of repetitions for the tooth surface strength is calculated by, for example, the Hertz formula from the specification of the pinion gear 41a, the average value of the load, and the average value of the rotation speed.

  In step S505, the number of times that the pinion gear 41a meshes with the rack gear 41b (hereinafter referred to as “repetition number”) is calculated based on the acquired rotation angle. Specifically, the number of repetitions is calculated by accumulating the acquired rotation angles and calculating the number of rotations of the pinion gear 41a from the accumulated value of the rotation angles.

  In step S506, the degree of repeated load deterioration of the pinion gear 41a is calculated based on the allowable number of repetitions for the bending strength of the teeth, the allowable number of repetitions for the tooth surface strength, and the number of repetitions. Specifically, the degree of repeated load deterioration due to tooth bending is calculated by dividing the calculated number of repetitions by the allowable number of repetitions for the calculated bending strength of the teeth. Further, the degree of repeated load deterioration due to tooth surface damage is calculated by dividing the calculated number of repetitions by the allowable number of repetitions for the calculated tooth surface strength.

  As described above, the repeated load deterioration degree is calculated, and the process in the repeated load deterioration degree calculation unit 72b ends.

  As described above, in the electric power steering apparatus 100, the degree of deterioration of the first and second transmission units 41 and 42 is calculated based on the torque, the displacement speed, and the displacement amount estimated by the estimation unit 71. Based on the steering torque, the motor rotation angle, and the steering angle detected by the torque sensor 51, the rotation angle sensor 52, and the steering angle sensor 53, the estimation unit 71 generates torque and displacement in the first and second transmission units 41, 42, respectively. Estimate speed and displacement.

  The detected steering torque, motor rotation angle, and steering angle vary depending on the status of the steering operation and the driving status of the vehicle such as getting on an obstacle. Therefore, the deterioration degree calculation unit 72 calculates the deterioration degree according to the state of the steering operation or the driving state of the vehicle. Therefore, it is possible to grasp the degree of deterioration of the first and second transmission units 41 and 42 with high accuracy.

  Further, the steering torque, the motor rotation angle, and the steering angle detected by the torque sensor 51, the rotation angle sensor 52, and the steering angle sensor 53, respectively, are used for the control of the electric motor 50 by the controller 60. That is, the state quantities of the first and second transmission units 41 and 42 are estimated based on the steering torque, the motor rotation angle, and the steering angle detected for the control of the electric motor 50 by the controller 60. Therefore, the degree of deterioration of the first and second transmission units 41 and 42 can be calculated without providing the electric power steering apparatus 100 with a detection unit different from the detection unit for controlling the electric motor 50. Thereby, increase of the sensor as a detection part of the electric power steering apparatus 100 can be prevented, and the deterioration degree of the 1st and 2nd transmission parts 41 and 42 can be grasped | ascertained with an inexpensive structure.

  Next, a configuration for maintaining the steering feeling of the electric power steering apparatus 100 will be described with reference to FIG.

  As shown in FIG. 2, the deterioration levels of the first and second transmission units 41 and 42 calculated by the deterioration level calculation unit 72 are input to the correction unit 60 b of the controller 60. The correction unit 60b changes the control parameter based on the input deterioration level.

  As described above, the deterioration degree calculation unit 72 can calculate the deterioration degree according to the state of the steering operation or the driving state of the vehicle. Therefore, the control parameter can be changed according to the steering operation situation or the vehicle driving situation. Therefore, it is possible to appropriately generate the torque of the electric motor 50 in anticipation of loads on the first and second transmission parts 41 and 42 due to deterioration, and to maintain the steering feeling.

  Next, a configuration for managing the replacement time of the electric power steering apparatus 100 will be described in detail with reference to FIGS. 1 and 2.

  As illustrated in FIG. 1, the management system 1000 includes a determination unit 81 that determines whether or not the electric power steering apparatus 100 needs to be replaced based on the deterioration level calculated by the deterioration level calculation unit 72, and a determination result by the determination unit 81. And a notification unit 82 that operates based on the above. Similar to the controller 60, the determination unit 81 is configured by a microcomputer. The notification unit 82 is mounted on the vehicle. The notification unit 82 may be a device visually recognized by the driver, for example, a character display device or a lamp, or may be a buzzer or a speaker that notifies the driver by sound.

  Processing performed by the determination unit 81 will be described with reference to FIG. Here, the determination process based on the deterioration degree of the pinion gear 41a of the first transmission unit 41 will be described. Since the determination process based on the deterioration degree of the rack gear 41b of the first transmission part 41 and the worm shaft 42a and the worm wheel 42b of the second transmission part 42 is substantially the same as the determination process based on the deterioration degree of the pinion gear 41a, Omitted.

  In step S601, the deterioration level calculated by the deterioration level calculation unit 72 is acquired. The degree of deterioration to be acquired is the degree of excessive load deterioration caused by the bending of the pinion gear 41a and the tooth surface, and the degree of repeated load deterioration caused by the bending of the tooth and the tooth surface.

  In step S602, it is determined whether or not the excessive load deterioration level resulting from the bending of the tooth exceeds a predetermined first threshold value. The first threshold is “1”, for example. The degree of overload degradation caused by tooth bending exceeding 1 is synonymous with the fact that the maximum load value calculated in step S404 (see FIG. 4) exceeds the bending strength of the teeth of the pinion gear 41a. .

  If it is determined in step S602 that the degree of overload deterioration due to tooth bending has exceeded the first threshold, the process proceeds to step S606. If it is determined in step S602 that the degree of overload deterioration due to tooth bending does not exceed the first threshold, the process proceeds to step S603.

  In step S603, it is determined whether or not the excessive load deterioration level due to the tooth surface damage exceeds a predetermined second threshold value. The second threshold is “1”, for example. The degree of overload degradation due to tooth surface damage exceeding 1 is synonymous with the fact that the maximum load value calculated in step S404 (see FIG. 4) exceeds the tooth surface strength of the pinion gear 41a. .

  If it is determined in step S603 that the degree of overload degradation due to tooth surface damage has exceeded the second threshold, the process proceeds to step S606. If it is determined in step S603 that the degree of overload deterioration due to tooth surface damage does not exceed the second threshold value, the process proceeds to step S604.

  In step S604, it is determined whether or not the repeated load deterioration due to the bending of the teeth exceeds a predetermined third threshold. The third threshold is “1”, for example. When the degree of repeated load deterioration due to tooth bending exceeds 1, the number of repetitions calculated in step S505 (see FIG. 5) is equal to the bending strength of the teeth calculated in step S504 (see FIG. 5). Is equivalent to exceeding the allowable number of repetitions for.

  If it is determined in step S604 that the repeated load deterioration due to tooth bending has exceeded the third threshold, the process proceeds to step S606. If it is determined in step S604 that the repeated load deterioration due to tooth bending does not exceed the third threshold, the process proceeds to step S605.

  In step S605, it is determined whether or not the degree of repeated load deterioration due to tooth surface damage exceeds a predetermined fourth threshold value. The fourth threshold is “1”, for example. The degree of repeated load deterioration due to tooth surface damage exceeding 1 indicates that the number of repetitions calculated in step S505 (see FIG. 5) is the tooth surface strength calculated in step S504 (see FIG. 5). Is equivalent to exceeding the allowable number of repetitions for.

  If it is determined in step S605 that the degree of repeated load deterioration due to tooth bending has exceeded the fourth threshold value, the process proceeds to step S606. If it is determined in step S605 that the degree of repeated load deterioration due to tooth bending does not exceed the third threshold, the process returns to step S601.

  In step S606, a signal for operating the notification unit 82 is output. Thereby, the notification unit 82 operates and notifies the driver that the electric power steering device 100 needs to be replaced. After outputting the signal for operating the notification unit 82, the process performed by the determination unit 81 ends.

  In the management system 1000, the necessity of replacement of the electric power steering apparatus 100 is determined based on the deterioration degree calculated by the deterioration degree calculation unit 72, and the replacement time is managed. As described above, the deterioration degree calculation unit 72 can calculate the deterioration degree according to the state of the steering operation or the driving state of the vehicle, so that the replacement timing of the electric power steering apparatus 100 can be managed more appropriately. it can.

  Next, the process performed by the estimation part 71 is demonstrated. The estimation unit 71 uses a mathematical model by an extended observer, and an input / output relationship between a current value commanded to the current supply unit 61 that is a control input value and a steering torque, a motor rotation angle, and a steering angle detected as an output value. Is used to estimate the state quantities of the first and second transmission units 41 and 42.

  A state quantity estimation method by the estimation unit 71 will be described in detail with reference to symbols shown in Tables 1 and 2. Table 1 is a table showing main specifications of the electric power steering apparatus 100, and Table 2 is a table showing main variables in the electric power steering apparatus 100.

  The state equation in the electric power steering apparatus 100 is expressed by the following equation (1-1).

  Moreover, the output equation in the electric power steering apparatus 100 is represented by the following equation (1-2).

  When the extended observer theory is applied to the equations (1-1) and (1-2), the following equations (1-3) and (1-4) are obtained.

  For the extended system models of Expression (1-3) and Expression (1-4), an observer represented by the following Expression (1-5) is constructed.

  By using the equation (1-5), it is possible to estimate the state quantity and the component of the disturbance z and the component of the differential value z ′ thereof from the observation quantity y and the control quantity u that change from moment to moment.

  The estimated value of the torque transmitted from the pinion gear 41a to the rack gear 41b is based on the motor rotation angle, the motor rotation angular velocity, the motor rotation angular acceleration, and the steering angle from among the estimated z and z ′ components. It is calculated by the following equation (1-6).

  Further, the estimated value of the rotation angle and the estimated value of the rotation speed of the pinion gear 41a are based on the motor rotation angle and the motor rotation angular speed among the estimated components of z and z ′, specifically, 1-7) and the formula (1-8).

  Further, the estimated value of the torque transmitted from the worm shaft 42a to the worm wheel 42b is based on the motor rotation angular velocity and the motor rotation angular acceleration from among the estimated z and z ′ components. 1-9).

  Further, the estimated value of the rotation angle and the estimated value of the rotation speed of the worm shaft 42a are based on the motor rotation angle and the motor rotation angular speed from among the estimated z and z ′ components. 1-10) and the formula (1-11).

  As described above, the torque, the displacement speed, and the displacement amount in the first and second transmission units 41 and 42 are estimated.

  According to the above embodiment, the following effects are obtained.

  In the electric power steering apparatus 100, the state quantities of the first and second transmission units 41 and 42 are estimated based on the torque, the rotation angle, and the steering angle used for controlling the electric motor 50. Therefore, the detection unit for controlling the electric motor 50 and the detection unit for calculating the degree of deterioration of the first and second transmission units 41 and 42 can be shared. Therefore, an increase in the number of sensors as detection units of the electric power steering apparatus 100 can be prevented, and the degree of deterioration of the first and second transmission units 41 and 42 can be grasped with an inexpensive configuration.

  Further, the deterioration degree calculation unit 72 calculates the maximum value of the load based on the torque estimated by the estimation unit 71 and calculates the deterioration degree of the first and second transmission units 41 and 42. Therefore, it is possible to grasp the degree of excessive load deterioration caused by receiving a temporary excessive load.

  Further, the deterioration degree calculating unit 72 calculates the number of repetitions and the allowable number of repetitions based on the torque, the displacement speed, and the amount of displacement estimated by the estimation unit 71, and based on the calculated number of repetitions and the allowable number of repetitions, The degree of deterioration of the first and second transmission units 41 and 42 is calculated. Therefore, it is possible to grasp the degree of repeated load deterioration caused by repeatedly receiving the load.

  Further, the controller 60 changes a control parameter for controlling the electric motor 50 based on the deterioration degree calculated by the deterioration degree calculation unit 72. Therefore, it is possible to control the electric motor 50 so as to generate torque in anticipation of load changes in the first and second transmission parts 41 and 42 due to deterioration, and it is possible to maintain the steering feeling.

  In addition, the determination unit 81 determines whether or not the electric power steering apparatus 100 needs to be replaced based on the deterioration degree calculated by the deterioration degree calculation unit 72. Therefore, the replacement time of the electric power steering device 100 can be managed more appropriately.

  In the electric power steering apparatus 100, the steering angle is detected by the steering angle sensor 53 and used for estimating the state quantities of the first and second transmission units 41 and 42, but the steering angle detected by the steering angle sensor 53 is used. It is also possible to estimate the state quantities of the first and second transmission units 41 and 42 without using. In this case, the following formula (1-2 ') and formula (1-4') are used instead of formula (1-2) and formula (1-4).

  When the detected steering angle is used for estimating the state quantities of the first and second transmission units 41 and 42, the state quantities of the first and second transmission units 41 and 42 are estimated without detecting the steering angle. Compared with, a model used for estimation of the state quantity can be constructed in detail. Therefore, the state quantities of the first and second transmission units 41 and 42 can be estimated more accurately, and the degree of deterioration of the first and second transmission units 41 and 42 can be grasped more accurately.

<Second Embodiment>
Next, an electric power steering apparatus 200 according to a second embodiment will be described with reference to FIG. In the following, differences from the first embodiment will be mainly described, and the same or equivalent configurations as those described in the first embodiment are denoted by the same reference numerals as those in the first embodiment. Description is omitted.

  The electric power steering device 200 is a so-called dual pinion type electric power steering device that assists the steering operation by transmitting the torque of the electric motor 50 to the rack shaft 30 through a shaft different from the output shaft 22.

  As shown in FIG. 7, in the electric power steering apparatus 200, the output shaft of the electric motor 50 is connected to a pinion shaft 222 provided independently of the output shaft 22 via a second transmission unit 242.

  The second transmission unit 242 includes a worm shaft 42 a provided on the output shaft of the electric motor 50 and a worm wheel 242 b provided on the pinion shaft 222. The torque of the electric motor 50 is transmitted to the pinion shaft 222 through the worm shaft 42a and the worm wheel 242b.

  The pinion shaft 222 is connected to the rack shaft 30 via the third transmission portion 243. The third transmission unit 243 includes a pinion gear 243a provided on the pinion shaft 222 and a rack gear 41b. The torque of the pinion shaft 222 is converted into an axial load of the rack shaft 30 via the pinion gear 243a and the rack gear 41b and transmitted to the rack shaft 30.

  Similarly to the electric power steering device 100, the electric power steering device 200 includes a controller 60, an estimation unit 71, and a deterioration degree calculation unit 72. Since the configurations and operations of the controller 60 and the deterioration degree calculation unit 72 are substantially the same as those in the first embodiment, detailed description thereof is omitted here.

  Next, the process performed by the estimation part 71 is demonstrated. The estimation unit 71 uses a mathematical model by an extended observer, and an input / output relationship between a current value commanded to the current supply unit 61 that is a control input value and a steering torque, a motor rotation angle, and a steering angle detected as an output value. Is used to estimate the state quantities of the first, second, and third transmission units 41, 242, and 43.

  The state quantity estimation method by the estimation unit 71 in the second embodiment will be described in detail with reference to symbols shown in Tables 3 and 4 in addition to symbols shown in Tables 1 and 2. Table 3 is a table showing specifications not shown in Table 1 among the specifications of the electric power steering apparatus 200. Table 4 is a table showing variables that are not shown in Table 2 among the variables of the electric power steering apparatus 200.

  The state equation in the electric power steering apparatus 200 is expressed by the following equation (2-1).

  Moreover, the output equation in the electric power steering apparatus 200 is expressed by the following equation (2-2).

  When the extended observer theory is applied to the equations (2-1) and (2-2), the following equations (2-3) and (2-4) are obtained.

  With respect to the extended system models of Expression (2-3) and Expression (2-4), an observer represented by the following Expression (2-5) is constructed.

  By using Expression (2-5), it is possible to estimate the component of the state quantity and the disturbance z and the component of the differential value z ′ from the observed quantity y and the controlled quantity u that change from moment to moment.

  The estimated value of the torque transmitted from the pinion gear 41a to the rack gear 41b is based on the motor rotation angle, the motor rotation angular velocity, the motor rotation angular acceleration, and the steering angle from among the estimated z and z ′ components. It is calculated by the following equation (2-6-1).

  The estimated value of torque transmitted from the pinion gear 243a to the rack gear 41b is based on the motor rotation angle, the motor rotation angular velocity, the motor rotation angular acceleration, and the rudder angle among the estimated z and z ′ components. It is calculated by the following equation (2-6-2).

  Further, the estimated value of the rotation angle and the estimated value of the rotation speed of the pinion gear 243a are based on the motor rotation angle and the motor rotation angular speed among the estimated z and z ′ components, specifically, 2-7) and the formula (2-8).

  Further, the estimated value of the torque transmitted from the worm shaft 42a to the worm wheel 242b is based on the motor rotation angular velocity and the motor rotation angular acceleration from among the estimated z and z ′ components, and specifically, 2-9).

  Further, the estimated value of the rotation angle and the estimated value of the rotation speed of the worm shaft 42a are based on the motor rotation angle and the motor rotation angular speed from among the estimated z and z ′ components. 2-10) and the formula (2-11).

  As described above, the torque, the displacement speed, and the displacement amount in the first, second, and third transmission units 41, 242, and 243 are estimated.

  According to the above embodiment, the same effects as in the first embodiment can be obtained.

  In the electric power steering apparatus 200, the rudder angle is detected by the rudder angle sensor 53 and used to estimate the state quantities of the first, second and third transmission units 41, 242, 243. Without using, it is also possible to estimate the state quantities of the first, second and third transmission units 41, 242, and 243. In this case, instead of the formula (2-2) and the formula (2-4), the following formula (2-2 ') and formula (2-4') are used.

  Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.

  The electric power steering apparatus 100, 200 includes a steering shaft 20 that rotates in accordance with a steering operation, a torsion bar 23 that constitutes a part of the steering shaft 20, and a torque sensor 51 that detects a steering torque that acts on the torsion bar 23. The electric motor 50 that displaces the rack shaft 30 that steers the wheel 1, the rotation angle sensor 52 that detects the rotation angle of the electric motor 50, the steering torque that is detected by the torque sensor 51, and the rotation angle sensor 52 that is detected. A controller 60 that controls the electric motor 50 according to the motor rotation angle, a first transmission unit 41 that transmits torque acting on the steering shaft 20 and torque of the electric motor 50 to the rack shaft 30, a second transmission unit 42, 242 and the third transmission part 243 and the torque sensor 5 An estimation unit that estimates the state quantities of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 based on the steering torque detected by the rotation angle sensor and the motor rotation angle detected by the rotation angle sensor 52. 71 and a deterioration level calculation unit 72 that calculates the deterioration level of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 based on the state quantity estimated by the estimation unit 71. .

  In this configuration, the state quantities of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 are based on the steering torque and the motor rotation angle detected for the control of the electric motor 50 by the controller 60. Is estimated. Therefore, the sensor for controlling the electric motor 50 and the sensor for calculating the degree of deterioration of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 can be shared. . Therefore, an increase in the sensors of the electric power steering devices 100 and 200 can be prevented, and the degree of deterioration of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 can be grasped with an inexpensive configuration. Can do.

  The electric power steering devices 100 and 200 further include a steering angle sensor 53 that detects the steering angle, and the estimation unit 71 detects the steering torque detected by the torque sensor 51 and the motor rotation angle detected by the rotation angle sensor 52. Based on the steering angle detected by the steering angle sensor 53, the state quantities of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 are estimated.

  In this configuration, since the three detection amounts are used by the estimation unit 71, it is possible to construct a model used for estimating the state amount in detail, compared to the case where only the two detection amounts are used by the estimation unit 71. it can. Accordingly, the state quantities of the first transmission unit 41, the second transmission units 42, 242, and the third transmission unit 243 can be estimated more accurately, and the first transmission unit 41, the second transmission units 42, 242, and the third transmission amount can be estimated. The degree of deterioration of the transmission unit 243 can be grasped more accurately.

  In the electric power steering devices 100 and 200, the estimation unit 71 estimates the torque in the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 as a state quantity, and the deterioration degree calculation unit 72 The maximum value of the load is calculated based on the torque estimated by the estimation unit 71, and the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 are deteriorated based on the calculated maximum value of the load. Calculate the degree.

  With this configuration, it is possible to grasp the degree of excessive load deterioration caused by receiving a temporary excessive load.

  In the electric power steering devices 100 and 200, the estimation unit 71 further estimates the displacement speed and displacement amount of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 as state quantities, and deteriorates. The degree calculation unit 72 calculates the number of repetitions based on the estimated amount of displacement, calculates an allowable number of repetitions based on the estimated torque and displacement speed, and calculates the number of repetitions based on the calculated number of repetitions and the allowable number of repetitions. The degree of deterioration of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 is calculated.

  With this configuration, it is possible to grasp the degree of repeated load deterioration caused by repeatedly receiving a load.

  In the electric power steering devices 100 and 200, the controller 60 changes the control parameter for controlling the electric motor 50 based on the deterioration degree calculated by the deterioration degree calculation unit 72.

  In this configuration, the electric motor 50 is controlled so as to generate torque in anticipation of changes in the loads of the first transmission unit 41, the second transmission units 42 and 242, and the third transmission unit 243 accompanying a change in the degree of deterioration. . Therefore, the steering feeling can be maintained.

  In addition, the present embodiment relates to a management system 1000 that manages the electric power steering devices 100 and 200. The management system 1000 includes a determination unit 81 that determines whether or not the electric power steering devices 100 and 200 need to be replaced based on the deterioration level calculated by the deterioration level calculation unit 72, and the determination unit 81 includes the electric power steering device 100. , 200 when it is determined that replacement is required, and a notification unit 82 that notifies that the replacement timing of the electric power steering devices 100, 200 has come.

  In this configuration, whether or not the electric power steering devices 100 and 200 need to be replaced is determined based on the calculated degree of deterioration. Therefore, the replacement time of the electric power steering devices 100 and 200 can be managed more appropriately.

  As mentioned above, although embodiment of this invention was described, the said embodiment only showed a part of application example of this invention, and the meaning which limits the technical scope of this invention to the specific structure of the said embodiment. Absent.

  For example, although the electric power steering device 100 is based on a column type electric power steering device, it may be a single pinion type electric power steering device.

  Further, the deterioration degree calculation unit 72 of the electric power steering devices 100 and 200 includes an overload deterioration degree caused by tooth bending, an overload deterioration degree caused by tooth surface damage, and a repeated load caused by tooth bending. It may be configured to calculate at least one of the degree of deterioration and the degree of repeated load deterioration due to tooth surface damage.

  Further, the estimation unit 71 of the electric power steering apparatus 100 may be configured to estimate at least one state quantity of the first transmission unit 41 and the second transmission unit 42, and the deterioration degree calculation unit 72 The degree of deterioration of at least one of the first transmission unit 41 and the second transmission unit 42 may be calculated. Similarly, the estimation unit 71 of the electric power steering apparatus 200 may be configured to estimate at least one state quantity of the first transmission unit 41, the second transmission unit 242, and the third transmission unit 243. The degree calculation unit 72 may be configured to calculate at least one degree of deterioration of the first transmission unit 41, the second transmission unit 242, and the third transmission unit 243.

  In addition, the correction unit 60b of the electric power steering devices 100 and 200 includes an overload deterioration degree due to tooth bending, an overload deterioration degree due to tooth surface damage, and a repeated load deterioration degree due to tooth bending. Further, the control parameter may be changed based on at least one of the degree of repeated load deterioration caused by tooth surface damage.

  Further, the determination unit 81 of the electric power steering devices 100 and 200 includes an overload deterioration degree due to tooth bending, an overload deterioration degree due to tooth surface damage, and a repeated load deterioration degree due to tooth bending. Further, it may be configured to determine whether or not the electric power steering devices 100 and 200 need to be replaced based on at least one of the degree of repeated load deterioration caused by the tooth surface damage.

  Further, at least one of the first and second transmission units 41 and 42 of the electric power steering apparatus 100 may be a belt-type transmission mechanism. Similarly, at least one of the first, second, and third transmission units 41, 242, and 243 of the electric power steering apparatus 200 may be a belt-type transmission mechanism.

  The notification unit 82 of the management system 1000 is not limited to the form mounted on the vehicle, and may be provided away from the vehicle, for example, at a place such as a management center. In this case, it is possible to manage the replacement time of the electric power steering devices 100 and 200 also in the management center.

  DESCRIPTION OF SYMBOLS 1 ... Wheel, 20 ... Steering shaft, 23 ... Torsion bar, 30 ... Rack shaft, 41 ... 1st transmission part, 42 ... 2nd transmission part, 50 ... Electricity Motor: 51 ... Torque sensor (torque detector), 52 ... Rotation angle sensor (rotation angle detector), 53 ... Steer angle sensor (steer angle detector), 60 ... Controller (controller) , 71... Estimating unit, 72... Deterioration degree calculating unit, 81... Determining unit, 82 ... Notifying unit, 100, 200 ... Electric power steering device, 242 ... Second transmission , 243 ... third transmission unit, 1000 ... management system

Claims (6)

A steering shaft that rotates in accordance with the steering operation;
A torsion bar constituting a part of the steering shaft;
A torque detector for detecting a steering torque acting on the torsion bar;
An electric motor that displaces the rack shaft that steers the wheels;
A rotation angle detector for detecting a rotation angle of the electric motor;
A control unit for controlling the electric motor according to a steering torque detected by the torque detection unit and a motor rotation angle detected by the rotation angle detection unit;
A transmission unit that transmits torque acting on the steering shaft and torque of the electric motor to the rack shaft;
An estimation unit that estimates a state quantity of the transmission unit based on a steering torque detected by the torque detection unit and a motor rotation angle detected by the rotation angle detection unit;
An electric power steering apparatus comprising: a deterioration degree calculation unit that calculates a deterioration degree of the transmission unit based on the state quantity estimated by the estimation unit. The electric power steering apparatus according to claim 1,
A steering angle detector for detecting the steering angle;
The estimation unit is a state quantity of the transmission unit based on a steering torque detected by the torque detection unit, a motor rotation angle detected by the rotation angle detection unit, and a steering angle detected by the steering angle detection unit. An electric power steering apparatus characterized by estimating The electric power steering device according to claim 1 or 2,
The estimation unit estimates the torque in the transmission unit as a state quantity,
The deterioration degree calculation unit calculates a maximum load value based on the torque estimated by the estimation unit, and calculates a deterioration degree of the transmission unit based on the calculated maximum load value. Power steering device. The electric power steering device according to claim 3,
The estimation unit further estimates a displacement speed and a displacement amount of the transmission unit as a state quantity,
The deterioration degree calculation unit calculates the number of repetitions based on the estimated displacement amount, calculates an allowable number of repetitions based on the estimated torque and displacement speed, and based on the calculated number of repetitions and the allowable number of repetitions An electric power steering apparatus characterized by calculating a deterioration degree of the transmission unit. The electric power steering device according to any one of claims 1 to 4,
The electric power steering apparatus, wherein the control unit changes a control parameter for controlling the electric motor based on the deterioration degree calculated by the deterioration degree calculation unit. A management system for managing the electric power steering device according to any one of claims 1 to 5,
A determination unit that determines whether or not the electric power steering device needs to be replaced based on the deterioration level calculated by the deterioration level calculation unit;
An electric power comprising: a notifying unit for notifying that it is time to replace the electric power steering device when the determining unit determines that the electric power steering device needs to be replaced. Steering device management system.

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