JP2007276552A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering device, capable of carrying out a recovering process at occurrence of contact failure or other abnormality due to freezing or the like at a relay contact in a feeding circuit. <P>SOLUTION: A power feed line abnormality detector 32 takes inputs of torque signals, relay coil temperature, and motor drive circuit power voltage to determine whether or not there is abnormality in the power feed line based on the state of variation of power voltage in a motor drive circuit and the state of variation of torque gain. Abnormality detection signals are outputted to a motor output limiter 30 and a fail safe processor 33 to stop feeding to a power relay 47 and a motor relay 48. As temperature rises due to energization to the relay to eliminate freezing, a process of putting on/off the contacts to recover contact failure is carried out. In case where abnormality is determined in the power feed line even after a diagnosis process is repeated for a plurality of times, abnormality in the power feed line is confirmed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus, and in particular, an electric power provided with means for detecting an abnormality such as a continuity failure of a relay disposed between the power source and a controlled object and recovering the detected abnormality such as a continuity failure. The present invention relates to a steering device.

  An electric power steering device for a vehicle detects a steering torque and a vehicle speed generated in a steering shaft by operating a steering handle, and drives a motor based on the detection signal to assist a steering force of the steering handle. is there. Such an electric power steering apparatus is controlled by an electronic control circuit. The outline of the control is as follows: current supplied to the motor based on the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor. And the current supplied to the motor is controlled based on the result of the calculation.

  That is, when the steering wheel is operated and steering torque is generated, the electronic control circuit supplies a large steering assist force when the detected vehicle speed is zero or low, and the detected vehicle speed is high. Can control the current supplied to the motor in accordance with the steering force of the steering wheel and the vehicle speed so as to supply a small steering assist force, so that the optimum steering assist force according to the running state can be given. .

  In this type of device, feedback control is performed so that the current that actually flows through the motor matches the control target value of the motor current that is calculated based on the steering torque and vehicle speed. For this reason, the current that flows through the motor is detected. Motor current detecting means is provided.

  If the motor current detecting means described above fails, the accurate motor current cannot be measured. As a result, an excessive current flows to the motor to supply an excessive steering assist force, or the motor is not necessary. As a result, there is a problem that a sufficient amount of steering assist force cannot be supplied.

  Furthermore, if the motor rotates when a current is supplied to the motor and the operation of the motor current detecting means is confirmed, the steering handle rotates in a state where the motor shaft and the steering mechanism are coupled, and this is unexpected. An accident may occur.

  In response to this problem, the applicant is expected to apply a low voltage to the motor for a time sufficiently larger than the electrical time constant of the motor and sufficiently smaller than the mechanical time constant of the motor. Based on the current value and the motor current value detected by the motor current detection means, a failure determination means for determining a failure of the motor current detection means has been proposed (see Patent Document 1).

  However, there is no problem if the motor is new, but if it is used for a certain period of time, an oxide film with electrical insulating properties will be formed on the contact surface between the commutator and the brush of the motor, and the oxide film will become thicker over time. The electric resistance tends to increase, and the motor current does not flow unless a higher voltage is applied to the motor.

  In response to this problem, the present applicant sets the motor current command value for a time sufficiently larger than the electrical time constant of the motor and sufficiently smaller than the mechanical time constant of the motor and sets the motor current command value to the motor current command value. The current control value based on the motor is changed over time, and the motor current prediction value and the motor current detection value detected by the motor current detection means are repeated while starting with a low motor applied voltage and increasing the applied voltage over time. A failure determination means for detecting a failure of the motor current detection means by comparison is proposed (see Patent Document 2).

However, the inconvenience that the oxide film is formed on the contact surface between the commutator and the brush of the motor and the conductivity is impaired is not limited to the motor with the commutator, and is disposed in the power supply circuit of the electric power steering device. Similarly, the contact point of the relay is also disadvantageous in that the oxide film is formed and the conductivity is impaired. Therefore, the present applicant interrupts the failure detection process when the failure determination of the motor current detection unit is continued a plurality of times by the failure determination unit, and continues the ON / OFF control of the relay for a predetermined period to remove the oxide film or foreign matter. After removing it, we developed a control means to restart the failure detection process.
JP-A-8-91239 JP 2003-237605 A

  However, the inconvenience occurring at the relay contacts arranged in the above-described power supply circuit is not only caused by the oxide film formed by the prolonged use period. In an extremely low temperature environment, there is a possibility that the relay may not be turned ON / OFF due to icing of moisture adhering to the relay contact portion or icing of moisture adhering to the movable member constituting the relay.

  In the case of such a relay icing, not only in an open type relay but also in a closed type relay, when the sealed case is constituted by a resin material, the internal humidity rises due to the breathing action that permeates moisture at the molecular level. The same inconvenience as above may occur.

  SUMMARY OF THE INVENTION An object of the present invention is to solve various inconveniences that occur in a relay disposed in a power feeding circuit of an electric power steering apparatus, which has been a problem in the past.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the invention according to claim 1 is an electric power steering apparatus comprising: a motor that controls a steering mechanism to provide a steering assisting force based on at least a steering torque generated in a steering shaft. A relay disposed on the power supply line; power supply voltage detecting means for detecting a power supply voltage; relay temperature estimating means for estimating the relay temperature; and power supply line abnormality detecting means for detecting an abnormality in the power supply line. And the control device detects an abnormality of the power supply line based on a change state of the power supply voltage and a change state of the torque.

  The state of change in the power supply voltage used for detecting an abnormality in the power supply line in the control device is numerical information regarding the difference between the previous power supply voltage value and the current power supply voltage value sampled at a predetermined time interval. The torque change state is numerical information indicating the difference between the previous torque value and the current torque value sampled at a predetermined time interval.

  Then, the control device counts the number of occurrences of abnormality based on the sign of the integrated value of the numerical information indicating the change state of the power supply voltage and the numerical information indicating the change state of the torque, and the abnormality occurrence count is predetermined. When the threshold value is exceeded, it is determined that the power supply line is abnormal.

  The control device further includes motor current limiting means, and when abnormality of the power supply line is determined, if the relay temperature estimated by the relay temperature estimation means is equal to or lower than a predetermined temperature, the motor current is set to a predetermined value. Limit the following.

  The controller repeats ON / OFF operation of the relay when the relay temperature estimated by the relay temperature estimating means rises above a predetermined temperature.

  When the motor current is limited to a predetermined value or less in the diagnosis performed each time the power supply voltage value and the torque value are sampled, the control device determines that the motor current is less than the predetermined value in the next diagnosis. This restriction is removed, and the counter count value for counting the number of occurrences of abnormality is reset.

  When the number of diagnoses performed each time the power supply voltage value and the torque value are sampled exceeds the predetermined number of diagnoses and it is determined that the power supply line is still abnormal, the control device It is assumed that the abnormality is confirmed and a predetermined fail-safe process is executed.

  The relay disposed on the power supply line is a relay that energizes the excitation winding in order to drive the mechanical contact.

  Further, the relay temperature estimating means is a relay temperature estimating means for estimating based on a current value energized to the relay winding and a winding resistance value.

  The electric power steering apparatus may be provided with a plurality of relays each having two or more excitation windings and drive circuits for driving mechanical contacts on the power supply line.

  As described above, the electric power steering apparatus of the present invention detects an abnormality in the power supply line based on the state of change in the power supply voltage and the state of change in the torque.

  Under the condition where torque is generated, that is, under the condition where the motor current flows, the abnormality of the power supply line is judged from the state of change in the power supply voltage. It is possible to reliably detect poor contact caused by icing.

  When the abnormality of the power supply line is determined, if the estimated relay temperature is equal to or lower than a predetermined temperature (for example, the freezing point temperature or lower), the motor current is limited to a predetermined value or lower, thereby freezing the relay contact. When released, it is possible to avoid the danger of excessive motor assist due to a sudden increase in motor current.

  When the relay temperature rises above a predetermined temperature and contact failure, for example, icing is released, foreign matter attached to the relay contact can be removed by repeating the ON / OFF operation of the relay. In addition, the relay uses a self-heating relay that generates heat by energizing the relay windings, so that the relay contacts can freeze and the water adhering to the movable members of the relay can be frozen without any special heating means. Can be released.

  Embodiments of the present invention will be described below. FIG. 1 is a diagram for explaining an outline of the configuration of an electric power steering apparatus according to an embodiment of the present invention. A shaft 2 of a steering handle 1 is operated via a reduction gear 4, universal joints 5a and 5b, and a pinion rack mechanism 7. It is connected to the tyrod 8 of the opposite wheel. A torque sensor 3 that detects the steering torque of the steering handle 1 is provided on the shaft 2, and a motor 9 that assists the steering force is coupled to the shaft 2 via a reduction gear 4.

  There are first and second embodiments of the control device which is a control means for controlling the power steering device, which is referred to as the control device 10 in the first embodiment and the control device 50 in the second embodiment.

  The control device 10 (50) is supplied with an IG signal from the battery 14 via an ignition key (IG key) 11 and with power from a parallel power supply line. The control device 10 (50) calculates a steering assist command value based on the steering torque detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and the motor 9 based on the calculated steering assist command value. The current i supplied to is controlled.

[First embodiment of control device]
FIG. 2 is a block diagram illustrating the configuration of the control device 10 according to the first embodiment, and includes a configuration for detecting an abnormality in a power supply line to a power relay 47 described later.

  The control device 10 includes a CPU 10A and a detection circuit, a drive circuit, and the like connected to the CPU 10A. The CPU 10A shows a function executed by a program inside the CPU. For example, the phase compensator 23 does not indicate the phase compensator 23 as independent hardware, but indicates a phase compensation function executed by the CPU. FIG. 2 also shows the battery 14 and the motor 9 for easy understanding of the operation of the control device 10.

  Hereinafter, functions and operations of the control device 10 will be described.

  First, an ON / OFF signal output from the IG key 11 is detected by an IG key ON / OFF detector 21. When the IG key 11 is ON, a signal indicating ON is input to an input torque limiter 22 and a fail described later. It is output to the safe processor 33.

  A torque signal detected by the torque sensor 3 is input to the input torque limiter 22, and a torque signal greater than a predetermined value is limited and input to the phase compensator 23. In the phase compensator 23, the phase is compensated to increase the stability of the steering system and is input to the steering assist command value calculator 24. Further, the vehicle speed detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 24.

  The steering assist command value calculator 24 calculates a steering assist command value I that is a control target value of the current supplied to the motor 9 by a predetermined calculation formula based on the input torque signal and vehicle speed signal.

  The circuit composed of the comparator 25, the differential compensator 26, the proportional calculator 27, and the integral calculator 28 is a circuit that performs feedback control so that the actual motor current value i matches the steering assist command value I.

  The proportional calculator 27 outputs a proportional value proportional to the difference between the steering assist command value I and the actual motor current value i. The output of the comparator 25 is integrated by the integration calculator 28, and a proportional value of the integral value of the difference is output. The differential compensator 26 outputs a differential value of the steering assist command value I in order to increase the response speed of the motor current value i that actually flows through the motor with respect to the steering assist command value I. The differential value of the steering assist command value I output from the differential compensator 26, the proportional value proportional to the difference between the steering assist command value output from the proportional calculator 27 and the actual motor current value, and the integral calculator 28 The output integral value is added in the adder 29, and the current control value E (the duty ratio of the PWM signal that determines the motor applied voltage) is output through the motor output limiter 30. The current control value E is output to the motor drive circuit 41, and the motor 9 is driven. The current flowing through the motor 9 is detected by the motor current detector 42 and fed back to the adder 25.

  When the motor output limiter 30 constituting the motor output limiting means determines that the power supply line is abnormal such as a contact failure of the relay contact from the power supply line abnormality detector 32 and an abnormality signal is input to the motor drive circuit 41. Function to stop the output of the current control value E, stop the generation of the steering assist force by the motor, and gradually release the output restriction when the power supply line abnormality is resolved and the motor output restriction is released Is provided.

  When the power supply line is abnormal due to a contact failure of the relay contact or the like, the motor output is limited, so there is no danger to the driver's steering handle operation. Also, when the contact failure of the relay contact is resolved and the power supply line recovers normally, the output of the current control value E to the motor drive circuit is gradually recovered over time, and the motor output restriction is gradually released Therefore, since an excessive steering assist force is not suddenly generated, there is no danger to the driver's steering wheel operation.

  In addition, the control device 10 that constitutes the control means supplies the motor drive circuit power supply voltage detector 46 that constitutes the power supply voltage detection means that detects the power supply voltage supplied to the motor drive circuit 41 and the relay coil of the power supply relay 47. Relay coil voltage detector 45 for detecting the applied voltage, relay coil temperature estimator 31 constituting relay temperature estimating means for estimating the relay coil temperature to determine the icing state of the contact of the relay coil, power supply line abnormality A power supply line abnormality detector 32 that constitutes a detection means, and a fail safe processor 33 that stops power supply to a power relay 47 and a motor relay 48 to be described later when an abnormality of the power supply line is detected are provided.

  The relay coil voltage detector 45 and the relay coil temperature estimator 31 estimate the temperature of the power relay 47, calculate the current value from the detected power relay voltage and the internal resistance of the power relay, Calculate the calorific value based on the square of the resistance and current value, and estimate the relay coil temperature by adding the temperature (environmental temperature) at the start of energization of the relay coil measured by the temperature sensor attached to the control device. To do.

  In addition, the temperature of the relay coil can be estimated by providing a temperature sensor around the relay. However, when the temperature of the circuit board of the EPS control circuit is detected by the temperature sensor, the relay is detected from the temperature of the circuit board. The coil temperature can also be estimated.

  The power supply line abnormality detector 32 receives the torque signal input via the input torque limiter 22, the estimated relay coil temperature, and the motor drive circuit power supply voltage detected by the motor drive circuit power supply voltage detector 46 as inputs. Detect power supply line abnormality. When an abnormality is detected in the power supply line, the abnormality detection signal is output to the motor output limiter 30 as described above, and the abnormality detection signal is output to the failsafe processor 33 to the power relay 47 and the motor relay 48. Is stopped. The detection of power supply line abnormality and the fail safe process will be described in detail later.

  A contact 47 a of the power relay 47 is inserted into the power supply circuit that supplies power from the battery 14 to the motor drive circuit 41, and a contact 48 a of the motor relay 48 is inserted between the motor drive circuit 41 and the motor 9. The contact 47a of the power relay 47 and the contact 48a of the motor relay 48 are ON / OFF controlled by the failsafe processor 33.

  The motor drive circuit 41 is a circuit in which a semiconductor switching element that is ON / OFF controlled by the duty ratio of the PWM signal determined based on the current control value E is connected to an H bridge, and other circuits. A voltage (average value) corresponding to E is supplied to the motor 9. FIG. 3 shows an example of the configuration of the motor drive circuit 41. The motor drive circuit itself is a known circuit, and detailed description thereof is omitted here.

  The control device 10 described above determines the current command value I when the detected steering torque is large and the detected vehicle speed is zero or low when the steering handle is operated and the steering torque is generated. If the detected steering torque is small and the detected vehicle speed is high, the steering assist command value I is set to a small value, so that an optimal steering assist force according to the traveling state can be applied.

  Next, a diagnosis process for a disconnection abnormality of a power supply line or a contact failure of a relay contact (hereinafter referred to as an abnormality of a power supply line), which is a feature of the present invention, will be described.

  The above-mentioned abnormality of the power supply line can be detected by constantly monitoring the power supply voltage of the drive circuit. However, even when the battery is deteriorated, the same abnormal phenomenon as above occurs because the battery voltage decreases when the motor is driven. Therefore, it is difficult to accurately detect an abnormality in the power supply line only by monitoring the power supply voltage.

  Therefore, in the present invention, the diagnosis process is repeatedly performed a plurality of times, and abnormality of the power supply line is determined based on the change state of the power supply voltage of the motor drive circuit and the change state of the torque gain in each diagnosis process. Then, a process for recovering the contact failure of the relay contacts is executed. Then, when the abnormality of the power supply line is determined even after the diagnosis process is repeated a plurality of times, the abnormality of the power supply line is determined.

  In the following description, the difference Ed between the previous sampling value E0 of the power supply voltage and the current sampling value E1 (Ed = E0−E1) as the numerical value indicating the change state of the power supply voltage, and the numerical value indicating the change state of the torque gain. A difference Td (Td = T0−T1) between the previous sampling value T0 and the current sampling value T1 of the torque gain is used.

  In addition to detecting the abnormality of the power supply line, during the initial diagnosis of the EPS control circuit after turning on the ignition key, and during normal assist (steering assist) control, the following data is sampled at predetermined intervals. To do.

  First, the difference Ed between the previous sampling value E0 of the power supply voltage and the current sampling value E1 (Ed = E0−E1) and the difference Td between the previous sampling value T0 of the torque gain and the current sampling value T1 (Td = T0−T1). And the multiplication value C (C = Ed × Td) is calculated.

  Each time the sampling is performed, an abnormality counter indicating the number of occurrences of abnormality is counted up or down according to the sign of the multiplication value C. When the count value of the abnormality counter exceeds a predetermined threshold value, Judgment is made and predetermined processing is performed.

  That is, when the sign of the multiplication value C becomes negative (C <0), the abnormality counter indicating the number of occurrences of abnormality is incremented (addition 1), and the sign of the multiplication value C becomes positive (C> 0). If the value of the multiplication value C is zero (C = 0), the abnormality counter is kept as it is.

  The multiplication value C (C = Ed × Td), which is the multiplication result of the difference Ed (Ed = E0−E1) and the difference Td (Td = T0−T1), is always positive in the normal state ( Plus) or zero, not negative (minus). For example, when the steering is performed with the torque gain being maximum, the torque gain change is zero, and the power supply voltage change is the difference Ed between the previous sampling value E0 and the current sampling value E1 (Ed = E0−E1). Although the sign may be negative (minus), the multiplication value C that is the result of the multiplication is zero, the sign is not negative, and it is not treated as an abnormality.

  When the count value of the abnormality counter reaches a predetermined threshold value, the power supply line is determined to be abnormal. At this stage, the supply of the steering assist force is stopped, that is, the power supply to the motor is not stopped. The following processing is executed.

  First, the relay temperature at the time when the power supply line is determined to be abnormal is estimated, and if the estimated relay temperature is equal to or less than a predetermined value (for example, an icing temperature of 0 ° C.), motor current output is limited. . This is to avoid the danger that the motor current flows due to sudden contact of the relay contact and excessive assist occurs.

  Then, the relay temperature estimation process is executed even after the start of the motor current output restriction. When the estimated relay temperature exceeds a predetermined temperature, the wiping operation is performed to turn the relay off and then on again ( (Hereinafter referred to as OFF / ON operation) is performed a predetermined number of times. At this time, after one OFF / ON operation of the relay, the next operation is started after a predetermined time has elapsed and the contact state of the relay contact is stabilized.

  After the above-described relay OFF / ON operation ends, the motor current output restriction is gradually released. The time for releasing the output restriction is gradually released over an appropriate time so as not to pose a danger to the driver. This is because, for example, if the relay contact is normally restored as a result of relay OFF / ON operation when the estimated relay temperature is 0 ° C., the steering torque is immediately Therefore, the motor current corresponding to the current flows and excessive steering assist force is generated, which may cause danger to the driver. Therefore, the output limitation of the motor current is gradually released.

  This completes the determination of the abnormal state of the power supply line and the recovery process of the contact failure of the relay contact in the first diagnosis process. The determination of the abnormal state and the recovery of the contact failure of the relay contact in this diagnosis process are completed. Even if the process is repeated a predetermined number of times, for example, twice, if it is determined that there is an abnormality from the count value of the abnormality counter, the occurrence of the abnormality is confirmed and the fail safe process, that is, the supply of the steering assist force is stopped.

  FIG. 4 is a flowchart for explaining the outline of the power supply line determination process in the above-described diagnosis process. Assist control based on the current command value calculated based on the steering torque detected by the torque sensor and the vehicle speed sensor and the vehicle speed (step P1), and the relay temperature estimation process are executed (step P2). An abnormality determination process for the power supply line is executed (step P3), whether the ignition key (IG key) is OFF (the control device is energized and operating even when the IG key is OFF), or is a failure process (abnormality determination) Is executed) is determined (step P4). As a result, when the determination is negative, the process returns to step P1 and the abnormality determination process is repeated. If the determination is affirmative, the fail-safe process has already been executed, so a post-process for gradually releasing the motor current output restriction is executed (step P5), and the process is terminated.

  FIG. 5 is a flowchart for explaining the details of the abnormality determination process for the power supply line shown as step P3 in the flowchart of FIG. First, the difference Ed between the previous sampling value E0 of the power supply voltage and the current sampling value E1 (Ed = E0−E1) and the difference Td between the previous sampling value T0 of the torque gain and the current sampling value T1 (Td = T0−T1). And a multiplication value C (C = Ed × Td) of the difference Ed and the difference Td is calculated (step P11).

  At this time, the current sampling value E1 of the power supply voltage and the current sampling value T1 of the torque gain are stored in the storage device and used as the previous sampling values E0 and T0 in the next calculation.

  It is determined whether or not the multiplication value C is zero (C = 0) (step P12). If C = 0, the process proceeds to step P16. If C = 0 is not determined in step P12, it is determined whether or not the multiplication value C is positive (C> 0) (step P13). If the multiplication value C is positive (C> 0), the abnormal counter is counted. 1 is subtracted from the content (step P14), and when the multiplication value C is negative (C <0), 1 is added to the content of the abnormality counter (step P15).

  It is determined whether or not the count content of the abnormality counter is larger than a preset threshold value (for example, 100) (step P16). It is determined that the motor current is output, and the motor current output is limited (step P17). If the count content of the abnormality counter is less than the threshold value, it is determined that no abnormal state to be noted has occurred, the current (first) diagnostic process is terminated, and the next (second) diagnostic process. Move on.

  Further, it is determined whether or not the relay temperature estimated value is higher than a predetermined temperature set in advance (step P18). If the relay temperature estimated value is higher than the predetermined temperature (freezing temperature), the icing state of the relay is canceled. In step P19, it is determined whether or not the number of times of diagnosis is less than a predetermined number (for example, twice) set in advance (step P19). P20), the relay contact wiping operation (relay OFF / ONF operation) is performed (step P21), the abnormality counter is reset (step P22), and the motor current output restriction is allowed to be gradually released (step P23). ), Move on to the next diagnostic process.

  If it is determined in step P18 that the estimated relay temperature is not higher than the predetermined temperature set in advance, it is determined that the icing state of the relay has not been eliminated, and the current diagnostic process is performed to wait for the icing state to be eliminated. End and go to the next diagnostic process.

  Further, when the number of times of diagnosis processing reaches a predetermined number (for example, twice) set in advance in the determination of step P19, it is determined that the abnormal state of the power supply line cannot be resolved, and the diagnosis number counter is reset (step P24). ), Execution of the fail process (step P25), that is, the supply of the steering assist force is stopped, that is, the power supply to the motor is stopped, and the next diagnosis process is started.

  FIG. 6 is a timing chart for explaining an example of the timing of abnormality detection processing when the relay contact 47a of the power supply relay 47 freezes to cause a contact failure and the power supply line is abnormal in a cryogenic environment.

  Control by EPS is started at time t0. At this time, the relay temperature T is set to Tf below the freezing temperature, the relay drive circuit is set to relay ON, but the relay contact is in an OFF state due to freezing, the torque gain is 100%, the drive power supply voltage is the lower limit of the normal value, the motor There is no current output limit (100%), and the abnormal counter is a normal value.

  Since the relay drive circuit is set to ON, the relay temperature gradually increases due to energization of the relay coil. The monitoring of the change state of the torque gain and the monitoring of the change state of the drive power supply voltage are started, and the count of the abnormality counter is started.

  That is, the difference Ed between the previous sampling value E0 of the power supply voltage and the current sampling value E1 (Ed = E0-E1) and the difference Td between the previous sampling value T0 of the torque gain and the current sampling value T1 (Td = T0-T1). Further, the multiplication value C (C = Ed × Td) is calculated, and each time sampling is performed, counting of the abnormality counter indicating the number of occurrences of abnormality is started according to the sign of the multiplication value C.

  When the count value of the abnormality counter exceeds a predetermined threshold at time t1, and the abnormality of the power supply line is determined, the motor current output is limited. The relay contact wiping operation (OFF / ON operation) is performed at time t2 when the relay temperature T rises and reaches the freeze release temperature T0. Thereby, the freeze of the relay contact is released, the adhering ice pieces and other foreign matters are removed, the relay contact is turned on, and the abnormality counter is reset. Thereafter, the motor current output restriction is gradually released from time t3, and the motor current output restriction is completely released at time t4 to return to a normal state.

[Second Embodiment of Control Device]
FIG. 7 is a block diagram illustrating the configuration of the control device 50 according to the second embodiment, and includes a configuration for detecting an abnormality in the power supply line to the motor relay 48 and the motor 9.

  The control device 50 according to the second embodiment includes a CPU 50A, a detection circuit and a drive circuit connected to the CPU 50A, and the CPU 50A shows a function executed by a program inside the CPU. 7 also shows the battery 14 and the motor 9 in order to facilitate understanding of the operation of the control device 50.

  Since the control device 50 of the second embodiment has a configuration similar to that of the first embodiment, the same circuit elements and functional elements as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Differences will be described.

  In the second embodiment, the relay coil voltage detector 51 that detects the voltage of the motor relay 48 is replaced with a relay coil temperature detector in place of the relay coil voltage detector (45 of the first embodiment) that detects the voltage of the power relay 47. A relay coil temperature estimator 53 is provided instead of the device (31 of the first embodiment). Further, instead of the motor drive circuit power supply voltage detector (46 in the first embodiment), the motor terminal voltage detector 52 is replaced with the power supply line abnormality detector (32 in the first embodiment), and the power supply line abnormality is detected. Each device 54 is provided.

  In the second embodiment, the power supply line abnormality detector 54 has the estimated motor relay 48 temperature estimated by the relay coil temperature estimator 53, the motor terminal voltage detected by the motor terminal voltage detector 52, and the motor current. The motor current detected by the detector 42 is input, and an abnormality in the power supply line to the motor relay 48 and the motor 9 is detected. The relay coil temperature is estimated by the same method as described in the first embodiment.

  When an abnormality in the power supply line to the motor relay 48 and the motor 9 is detected, the abnormality detection signal is input to the motor output limiter 30, and the output of the current control value E to the motor drive circuit 41 is stopped and the motor is steered. In addition to stopping the generation of the auxiliary force, the abnormality detection signal is output to the failsafe processor 33, and the power supply to the power supply relay 47 and the motor relay 48 is stopped.

  The detection of the abnormality of the power supply line and the fail safe process are the same as the method described in the first embodiment, and the power supply voltage described in the first embodiment is replaced with the motor terminal voltage and the power relay is replaced with the motor relay. Therefore, detailed description is omitted.

  FIG. 8 is a diagram for explaining an example of a composite relay 60 and its drive circuit that can be used in place of the motor relay 48 of the control circuit shown in FIGS. In the composite relay 60, a plurality of relay coils L1, L2,... Ln are arranged around the iron core 61, and two relay coils, for example, L1 and L2, are a pair of coils and are set to have substantially the same characteristics. Yes. A mover 63 urged in a direction away from the iron core 61 by a tension spring 62 is disposed at the end of the iron core 61. The mover 63 is provided with a mover contact 63a and faces the mover contact 63a. A stator contact 63b is arranged at the position. The mover contact 63a and the stator contact 63b correspond to the contact 48a of the motor relay 48 of the control circuit shown in FIG. 2, and are connected to a control target (not shown) such as a motor.

  Further, the relay coils L1, L2,... Ln are respectively connected to the drive circuits D1, D2,... Dn, and the drive circuits D1, D2,. For example, when the device to be controlled has a configuration that performs fail-safe processing using a plurality of abnormality detection units and detection results thereof, the drive circuits D1 and D2 correspond to the fail-safe processing unit 33. ,... Dn are a plurality of fail-safe processors that operate according to the detection results of the plurality of abnormality detection units.

  The relay coil of the composite relay 60 includes a plurality of L1, L2,... Ln, and the drive circuit also includes a plurality of D1, D2,... Dn. Any number may be selected and used. Further, depending on the circuit configuration, a common relay contact can be used to open and close by driving any one of a plurality of different relay coils.

  Next, the operation will be briefly described. First, when the relay temperature is increased by energization, the drive circuits D1 and D2 are driven so that the generated magnetic force is canceled and currents in opposite directions are supplied to the coils L1 and L2, thereby operating the mover 53. I won't let you. Since the coils L1 and L2 generate heat by energization and the temperature of the composite relay 60 rises, the freezing of the movable contact 63a and the stator contact 63b can be released.

  Further, in the case of normal operation of the composite relay 60, when closing the contact, the drive circuits D1 and D2 are driven so that the direction of the generated magnetic force is in the same direction, and currents in the same direction are supplied to the coils L1 and L2. The armature 63 is attracted to the iron core 61 against the biasing force of the tension spring 62, and the armature contact 63a is brought into contact with the stator contact 63b. When the contact is opened, the current supply to the coils L1 and L2 is stopped, and the movable element 63 is separated from the iron core 61 by the urging force of the tension spring 62, and the contact between the movable element contact 63a and the stator contact 63b is released. Shall be allowed to.

  As described above, the means for solving the conduction failure of the power supply circuit according to the present invention has been explained by the power supply circuit of the steering assist motor. However, the means for solving the conduction failure of the power supply circuit according to the present invention is the conduction of other power supply circuits. Needless to say, it can also be applied to defect resolution.

  This is an electric power steering device that can detect and recover from the failure of relay contacts that are placed between the power supply and the motor to open and close the power supply circuit, especially in the low temperature environment due to continuity failures and abnormalities due to icing of the relay contacts. is there.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the outline of a structure of the electric power steering apparatus of embodiment of this invention. The block diagram of 1st Example of a control apparatus. The figure explaining an example of a structure of a motor drive circuit. A flow chart for explaining the outline of the power supply line abnormality determination process. FIG. 5 is a flowchart for explaining details of power supply line abnormality determination processing in the flowchart of FIG. 4. FIG. The timing chart explaining the timing of the abnormality detection process when abnormality of a power supply line is determined by the contact failure by freezing of a relay contact. The block diagram of 2nd Example of a control apparatus. The figure explaining an example of a composite relay and its drive circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering handle 2 Axis 3 Torque sensor 4 Reduction gear 5a, 5b Universal joint 7 Pinion rack mechanism 8 Tyrode 9 Motor 10 Control device (control device of 1st Example)
11 Ignition key (IG key)
12 Vehicle speed sensor 14 Battery 21 IG key ON / OFF detector 22 Input torque limiter 23 Phase compensator 24 Steering assist command value calculator 25 Comparator 26 Differential compensator 27 Proportional calculator 28 Integral calculator 29 Adder 30 Motor output Limiter 31 Relay coil temperature estimator 32 Power supply line abnormality detector 33 Fail safe processor 41 Motor drive circuit 42 Motor current detector 45 Relay coil voltage detector 46 Motor drive circuit power supply voltage detector 47 Power relay 47a Relay contact ( Relay contact of power relay)
48 Motor relay 48a Relay contact (Motor relay relay contact)
50 control device (control device of the second embodiment)
51 Relay coil voltage (battery voltage) detector 52 Motor terminal voltage detector 53 Relay coil temperature estimator 54 Power supply line abnormality detector 60 Relay 61 Iron core 62 Tension spring 63 Movable element L1, L2, ... Ln Relay coil D1 , D2, ... Dn drive circuit

Claims (10)

In an electric power steering apparatus including a control device that controls an output of a motor that applies a steering assist force to a steering mechanism based on a steering torque generated at least in a steering shaft,
A relay located on the power supply line;
Power supply voltage detecting means for detecting a power supply voltage;
Relay temperature estimating means for estimating the relay temperature;
Power supply line abnormality detecting means for detecting abnormality of the power supply line,
The control device detects an abnormality of a power supply line based on a change state of a power supply voltage and a change state of a torque. The state of change in the power supply voltage used for detecting an abnormality in the power supply line in the control device is numerical information relating to the difference between the previous power supply voltage value sampled at a predetermined time interval and the current power supply voltage value, and torque. 2. The electric power steering apparatus according to claim 1, wherein the change state is numerical information indicating a difference between the previous torque value and the current torque value sampled at a predetermined time interval. The control device counts the number of occurrences of abnormality based on a sign of an integrated value of numerical information indicating the state of change in power supply voltage and numerical information indicating the state of change in torque, and the counting of the number of occurrences of abnormality is a predetermined threshold value. The electric power steering apparatus according to claim 2, wherein the power supply line is determined to be abnormal when the value exceeds. The control device further includes a motor current limiting unit, and when it is determined that the power supply line is abnormal, the motor current is set to a predetermined value or less when the relay temperature estimated by the relay temperature estimation unit is a predetermined temperature or less. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is limited. 2. The electric power steering apparatus according to claim 1, wherein the control device repeats ON / OFF operation of the relay when the relay temperature estimated by the relay temperature estimating means rises to a predetermined temperature or more. When the motor current is limited to a predetermined value or less in the diagnosis performed each time the power supply voltage value and the torque value are sampled, the control device limits the motor current if the number of diagnosis is the predetermined value or less in the next diagnosis. The electric power steering apparatus according to claim 4, wherein the counter count value for counting the number of occurrences of abnormality is reset. When the number of diagnoses performed each time the power supply voltage value and the torque value are sampled exceeds the predetermined number of diagnoses and the power supply line is determined to be abnormal, the control device determines that the power supply line is abnormal. The electric power steering apparatus according to claim 2, wherein the electric power steering apparatus is fixed and predetermined fail-safe processing is executed. The electric power steering apparatus according to claim 1, wherein the relay disposed on the power supply line is a relay that energizes an excitation winding to drive a mechanical contact. 2. The electric power steering apparatus according to claim 1, wherein the relay temperature estimation means is relay temperature estimation means that estimates based on a current value energized in the relay winding and a winding resistance value. 3. 2. The electric power steering apparatus according to claim 1, wherein a plurality of relays each having two or more excitation windings and driving circuits for driving mechanical contacts are arranged on a power supply line. Power steering device.

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