JP2007203798A - Electric power steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid inoperative of a system caused by a foreign matter caught in a relay contact of a motor relay circuit. <P>SOLUTION: When abnormality is detected in an abnormality monitoring of a motor system during a disconnection check in starting and steering assist control by a normally closed type motor relay circuit, the motor relay circuit is controlled to be in an opened state. Since the motor relay circuit maintains a closed state while a steering assist control processing is not carried out, and the motor relay circuit maintains the closed state when an abnormality of the motor system does not occur even while the steering assist control processing is carried out, the opportunity when a foreign matter or the like is caught in the relay contact of the motor relay circuit is reduced, and the possibility of a failure of the system itself due to the abnormality of the motor relay circuit due to catching of the foreign matter is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention avoids a system down due to a malfunction of a motor relay circuit for cutting off a power supply line between an electric motor that applies a steering assist force to a steering system and a motor drive circuit that supplies electric power to the electric motor. The present invention relates to an electric power steering control device capable of performing the above.

In this type of electric power steering control device, when an abnormality such as a short circuit failure occurs in a field effect transistor (FET) constituting a motor drive circuit, the electric motor may act as an electromagnetic brake. In order to avoid this, conventionally, a motor relay is inserted in the power supply line to the electric motor, and when an abnormality occurs, the motor relay is switched to an open state to cut off the power supply to the electric motor. It avoids acting as an electromagnetic brake (see, for example, Patent Document 1).
JP 2002-12157 A

  As described above, in a system in which a motor relay is inserted in the power supply line to the electric motor, a normally open type relay is used as the motor relay, and the electric motor is controlled by closing the motor relay when the system is activated. When an abnormality occurs, the motor relay is controlled to be in an open state to cut off the power supply to the electric motor, thereby preventing the electric motor from acting as an electromagnetic brake.

In such a system, the motor relay is normally controlled to be closed when the system is started, but it is not confirmed whether the motor relay is reliably closed by this control, and the motor relay is closed. After the control is performed, the process shifts to the normal control for generating the steering assist force as it is.
For this reason, if the motor relay is not closed for some reason, even if the current control is performed after the shift to the normal control and the power supply to the electric motor is actually started, the motor relay is not opened. Since it remains in the state, power supply is not normally performed. As a result, the difference between the current command value to the electric motor and the current value actually flowing to the electric motor becomes large, and it is determined that an abnormality has occurred at this point.

For this reason, for example, when a motor relay is not closed because a foreign object is caught between the contact points of the motor relay, the motor relay is not closed even though the system itself has not failed. Therefore, there is a problem that the system is determined to be abnormal and the system cannot be operated normally thereafter, and the steering assist force cannot be generated.
In fact, when investigating returned products from the market, foreign matter that seems to have hindered contact connection inside the motor relay was confirmed.

Originally, the motor relay is provided in order to prevent the electric motor from acting as an electromagnetic brake when an abnormality occurs. However, although the system itself is normal, it is detected as a motor relay failure due to foreign matter etc., so it is determined that the system needs to be stopped and can operate as an electric power steering device. Since then, the driver cannot perform the steering operation. This greatly affects future vehicles and the size of the system itself, and there is a demand for an electric power steering control device that can operate reliably even if it takes some time to start the system.
Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and it is possible to avoid the system being down due to the influence of a foreign object or the like even though the system itself is normal. An object of the present invention is to provide an electric power steering control device.

  In order to achieve the above object, an electric power steering control device according to claim 1 of the present invention includes an electric motor that applies a steering assist force to a steering system, a motor drive circuit that drives the electric motor, A normally-closed motor relay circuit that cuts off power supply from the motor drive circuit to the electric motor, an abnormality monitoring unit that monitors abnormality of a motor system for driving and controlling the electric motor, and the abnormality monitoring unit Motor relay control means for controlling the motor relay circuit according to the monitoring result of the motor, and the motor relay control means controls the motor relay circuit to an open state when an abnormality is detected by the abnormality monitoring means. It is a feature.

  In the first aspect of the present invention, the motor relay circuit for cutting off the power supply line from the motor drive circuit to the electric motor is constituted by a normally closed circuit, and when abnormality is detected by the abnormality monitoring means, The motor relay circuit is controlled to the open state. For this reason, while the system is normal, the motor relay circuit is kept closed, so the chance of foreign objects getting caught in the contact of the motor relay circuit is reduced, and the system main body may be stopped due to foreign object pinching etc. Is reduced.

Further, in the electric power steering control device according to claim 2, the abnormality monitoring means detects the voltage between terminals of the motor relay circuit and the voltage between terminals of the electric motor. And a disconnection check means for controlling the motor drive circuit at the time of starting to energize the electric motor for disconnection check, and performing a disconnection check based on the detection result of the inter-terminal voltage detection means at this time. It is characterized by that.
In the invention according to claim 2, the electric motor is supplied with a current for checking disconnection at the time of start-up, and one of the voltage between the terminals of the motor relay circuit and the voltage between the terminals of the electric motor at this time is detected. Since the disconnection check is performed based on this, it is possible to detect disconnection abnormality at the time of startup.

  Further, in the electric power steering control device according to claim 3, the motor relay control means opens and closes the motor relay circuit when the disconnection check means detects an abnormality in the disconnection check at startup. The abnormality monitoring means detects the abnormality even when the motor relay circuit is opened / closed a specified number of times when the abnormality monitoring means detects the abnormality by the disconnection check and activates the opening / closing control means because there is a possibility of disconnection. When it is done, it is characterized as being determined as a disconnection abnormality.

  In the invention according to claim 3, when an abnormality is detected in the disconnection check at the time of start-up, it is determined that there is a possibility of disconnection, the opening / closing control means is operated, the motor relay circuit is opened / closed, and the opening / closing operation is performed a specified number of times. Even if it is determined that there is an abnormality, it is determined that the disconnection is abnormal.Therefore, when foreign matter is caught in the relay contact of the motor relay circuit, the foreign matter is removed by opening and closing operation. Therefore, it is possible to reduce the possibility of the system being stopped due to the influence of a foreign substance or the like rather than the abnormality of the system itself.

The electric power steering control device according to claim 4 is characterized in that the motor relay circuit is inserted in each power supply line between the electric motor and the motor drive circuit.
In the invention according to the fourth aspect, since the motor relay circuit is inserted in each of the power supply lines between the electric motor and the motor drive circuit to form a dual system, the power supply to the electric motor is performed. It becomes possible to cut off more reliably.

  In the electric power steering control device according to claim 5 of the present invention, the motor relay circuit is controlled to be opened and closed by a relay-off signal from the motor-relay control means, and the abnormality monitoring means has a normal relay-off signal at startup. A relay off signal abnormality detecting means for determining whether or not the motor relay control means has an alarm means for notifying the abnormality of the relay off signal, and the relay off signal abnormality detecting means detects the abnormality of the relay off signal. Then, the alarm means is operated while the motor relay circuit is maintained in a closed state.

  According to the fifth aspect of the present invention, the abnormality of the relay-off signal is detected at the time of starting, and when the abnormality is detected, the abnormality of the relay-off signal is notified by the alarm means while the motor relay circuit is maintained in the closed state. Is done. The motor relay circuit is configured as a normally closed circuit and maintains a closed state while control is not performed, and even if the relay off signal is abnormal, the electric motor can be energized. If there is no abnormality that causes malfunction in the system, there is no problem even if the power supply to the electric motor is continued. Therefore, it is possible to operate the system effectively while notifying that an abnormality has occurred by the alarm means.

  According to the electric power steering control apparatus of the first aspect of the present invention, the motor relay circuit is configured by a normally closed circuit, and when an abnormality is detected, the motor relay circuit is controlled to be opened to supply power to the electric motor. Since it has been cut off, the chance of foreign objects getting caught in the contact of the motor relay can be reduced, and the system itself is judged to be abnormal due to foreign objects even though it can operate normally, and the system is stopped. Event can be reduced.

According to the electric power steering control device of the second aspect, the current for checking the disconnection is supplied at the time of start-up, and at this time, at least one of the voltage between the terminals of the motor relay circuit and the voltage between the terminals of the electric motor is applied. Since the disconnection check is performed based on this, disconnection detection can be performed at the time of startup, and abnormality detection can be performed promptly.
Further, according to the electric power steering control device of the third aspect, when an abnormality is detected by the disconnection check at the time of start-up, the motor relay circuit is opened / closed a specified number of times, and when the abnormality is still determined, the disconnection abnormality is present. Therefore, it is possible to prevent the system from being stopped due to the influence of a foreign substance or the like rather than an abnormality of the system itself, and the reliability of the system can be improved.

Further, according to the electric power steering control device of the fourth aspect, since the motor relay circuit is inserted in each of the power supply lines between the electric motor and the motor drive circuit, a double system is configured. The power supply to the motor can be cut off more reliably, and the reliability can be improved.
Further, according to the electric power steering control device of the fifth aspect of the present invention, when an abnormality is detected by the relay-off signal at the time of activation, the alarm means causes the abnormality of the relay-off signal while maintaining the motor relay circuit in the closed state. Therefore, the system can be operated effectively while notifying that an abnormality has occurred by the alarm means.

Embodiments of the present invention will be described below.
First, a first embodiment will be described.
FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, in which 1 is a steering wheel, and a steering force applied to the steering wheel 1 from a driver is applied to the steering shaft 2. Communicated. This steering shaft 2 has an input shaft 2a and an output shaft 2b, one end of the input shaft 2a is connected to the steering wheel 1, and the other end is one end of the output shaft 2b via a torque sensor 3 as torque detecting means. It is connected to.

The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6.
The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured as a rack and pinion mechanism having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A reduction gear 10 that transmits an auxiliary steering force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The electric motor 12 that generates an auxiliary steering force for the steering system is connected to the reduction gear 10. The output shaft is connected.
The torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b is used. The torsional angular displacement is converted into an angular displacement and detected by, for example, a potentiometer. The torque detection value T output from the torque sensor 3 is input to the controller 13.

In addition to the torque detection value T, the controller 13 also receives a vehicle speed detection value V detected by the vehicle speed sensor 15, and the controller 13 assists the steering assist force according to the input torque detection value T and the vehicle speed detection value V. The steering assist command value I _M ^* generated by the electric motor 12 is calculated by a known procedure, and the drive current supplied to the electric motor 12 is calculated based on the calculated steering assist command value I _M ^* and the motor current detection value I _MD. A motor drive current I _M for feedback control is calculated.

As shown in FIG. 2, the controller 13 has a steering assist control unit 17 having a microcomputer 16 that executes control processing of the electric motor 12 and a motor drive current I _M output from the microcomputer 16 in a known procedure. A motor drive circuit 18 that controls the drive current that is input and supplied to the electric motor 12; a motor current detection circuit 19 that detects the drive current flowing through the electric motor 12; and for notifying the driver when an abnormality occurs. For example, an alarm device 50 provided in the vicinity of the driver's seat.
Here, the motor drive circuit 18 drives the gates of the field effect transistors FET1 to FET4 based on the H bridge circuit 20 including the field effect transistors FET1 to FET4 and the motor drive current I _M output from the microcomputer 16. An FET gate drive circuit 21 is included.

The FET1 and FET2 are turned on / off by a PWM (pulse width modulation) signal having a duty ratio D1 determined based on the motor drive current I _M, and the magnitude of the current that actually flows through the electric motor 12 is controlled. FET3 and FET4 are driven by a PWM signal having a duty ratio D2 defined by a predetermined linear function equation (D2 = a · D1 + b, where a and b are constants) in a region where the duty ratio D1 is small, and a region where the duty ratio D1 is large. Then, it is turned ON / OFF according to the rotation direction of the electric motor 12 determined by the sign of the PWM signal.

For example, when the FET 4 is in a conductive state, the current flows through the FET 1, the electric motor 12, the FET 4, and the resistor R _L , and a positive current flows through the electric motor 12. Further, when the FET 3 is in a conductive state, the current flows through the FET 2, the electric motor 12, the FET 3, and the resistor R _R , and a negative current flows through the electric motor 12.
Further, the motor current detection circuit 19 is inserted between the terminal voltage representing the normal motor current of the resistor _RL inserted between the field effect transistor FET4 and the ground, and the field effect transistor FET3 and the ground. The terminal voltage representing the reverse motor current of the resistor R _R is detected, and the positive motor current detection value “+ _IMD ” is detected when the forward motor current is detected, and the negative motor current detection value “−” is detected when the reverse motor current is detected. I _MD "is output.

Then, the internal voltage Vr generated inside the controller 13 is applied to the connection point of the field effect transistors FET1 and FET2, and the field effect transistors FET3 and FET4 are grounded via current detection resistors R _R and R _L , respectively. ing.
The motor relay section 40 includes a motor relay circuit 43 including a relay contact 41 and a relay coil 42 for energizing the relay contact 41, and a pnp type bipolar as an applied voltage control active element that controls an applied voltage to the relay coil 42. The relay contact 41 is connected between the connection point of the field effect transistors FET2 and FET4 of the H-bridge circuit 20 and one input side of the electric motor 12, and one end of the relay coil 42 is grounded. The other end is connected to the collector terminal of the transistor TR. An internal voltage Vb is applied to the emitter terminal of the transistor TR, and a relay-off signal Ss from the microcomputer 16 is input to the base terminal. When this relay-off signal Ss is input, the transistor TR becomes conductive and relays. A voltage is applied to the coil 42 and the motor relay circuit 43 is controlled to be in an open state.

Further, the relay terminal voltage detection circuit 25 detects a potential difference between both ends of the relay contact 41, and the potential difference between both ends of the relay contact 41 is converted into a relay terminal voltage Δvr via a A / D converter. 16 is input.
The microcomputer 16 is controlled to be always operable by an internal voltage Vc generated by using a battery (not shown) as a power source. When an ignition switch (not shown) is turned on, a power relay (not shown) is turned on. Then, power supply to each part of the system is started, and execution of the steering assist control process shown in FIG. 3 is started.

In this steering assist control process, as shown in FIG. 3, first, a disconnection check process described later is executed in step S1, and if normal, the process proceeds from step S2 to step S3, and if abnormal, the process is directly performed from step S2. Exit.
In step S3, the motor drive control process is executed according to a known procedure based on the detection signals of the torque sensor 3 and the vehicle speed sensor 15, and the electric motor 12 is driven so as to generate a steering assist force according to the steering force of the driver. Control. Further, a motor system monitoring process is performed based on the motor current detection value I _MD detected by the motor current detection circuit 19 and the motor drive current I _M (step S4). It is determined that the motor system is abnormal.

If the result of the motor system monitoring process is normal, the process proceeds from step S5 to step S6. If the ignition switch is not turned off, the process returns to step S3 and the motor drive control process is continued.
Then, when the ignition switch is turned off, the process proceeds from step S6 to step S7 to execute the steering assist control end processing, and is inserted into, for example, a power supply line for supplying power from the battery to each part. The power supply relay (not shown) is cut off, the power supply to each part is finished, and the steering assist control process is finished.

On the other hand, when it is determined as abnormal in the motor system monitoring process in step S4, the process proceeds from step S5 to step S8.
In this step S8, processing at the time of abnormality detection is executed, a relay-off signal Ss is output to the bipolar transistor TR, the alarm device 50 is activated, and a voice or a warning lamp provided near the driver's seat is turned on. Notify the driver that an abnormality has occurred in the motor system. Then, this state is maintained until the ignition switch is turned off. When the ignition switch is turned off, the power relay (not shown) is cut off, and the steering assist control process is ended.

  As a result, the relay-off signal Ss is supplied to the bipolar transistor TR, the bipolar transistor TR becomes conductive, and a voltage is applied to the relay coil 42. Therefore, the motor relay circuit 43 is opened and power to the electric motor 12 is supplied. Supply is cut off. When the ignition switch is turned off, a power relay (not shown) is cut off, power supply to each part is finished, and the steering assist control process is finished.

FIG. 4 is a flowchart illustrating an example of a processing procedure of the disconnection check processing.
In this disconnection check process, first, in step S11, a motor drive current I _MC for disconnection check is output to the FET gate drive circuit 21. The disconnection check motor drive current I _MC is set to a value corresponding to a current value at which the electric motor 12 does not rotate when the electric motor 12 is driven and controlled in accordance with the motor drive current I _MC .

Next, the process proceeds to step S12, in which the relay terminal voltage Δvr of the relay contact 41 detected by the relay terminal voltage detection circuit 25 is read, and whether or not the relay terminal voltage Δvr is greater than a preset threshold value. A disconnection check is performed based on (Step S13).
When the relay terminal voltage Δvr is larger than the threshold value, it is determined that the relay terminal voltage Δvr is normal and no disconnection has occurred, the process proceeds from step S13 to step S14, and processing at the end of the disconnection check is performed. Specifically, stops the output of the motor drive current I _MC for disconnection check, each unit performs processing such as ready to start the motor drive control processing.

  On the other hand, if the relay terminal voltage Δvr is equal to or lower than the threshold value in step S13, it is determined that a disconnection or a short circuit failure has occurred, and the process proceeds to step S15, and the relay off signal Ss is intermittently transmitted several times. Output. As a result, the motor relay circuit 43 performs an opening / closing operation several times. Therefore, there is a possibility that foreign matter is removed when foreign matter is caught in the relay contact 41. That is, this opening / closing operation is performed in order to remove foreign matter.

  If the opening / closing operation is performed several times, the process proceeds to step S16, the relay terminal voltage Δvr is read again from the relay terminal voltage detection circuit 25, and then the process proceeds to step S17, where the relay terminal voltage Δvr is normal. Determine if there is. When the voltage between relay terminals Δvr is normal, it is determined that the disconnection has been released by removing the foreign matter sandwiched between the relay contacts 41, and the process proceeds to step S14 to perform the process at the end of the disconnection check.

On the other hand, if the relay terminal voltage Δvr is not normal, that is, if the relay terminal voltage Δvr is substantially zero, it is determined that foreign matter has not been removed or that a break has occurred at any point, step S18. To move to, and execute the process when an abnormality is detected. Specifically, it stops the output of the motor drive current I _MC for the disconnection check. In addition, the relay off signal Ss is output to the bipolar transistor TR, the alarm device 50 is activated, and the driver is informed that an abnormality has occurred in the motor system by turning on a sound or a warning light provided near the driver's seat. Notice. Then, this state is maintained until the ignition switch is turned off. When the ignition switch is turned off, the power relay (not shown) is cut off, and the steering assist control process is ended.

  As a result, the relay-off signal Ss is supplied to the bipolar transistor TR, the bipolar transistor TR becomes conductive, and a voltage is applied to the relay coil 42. Therefore, the motor relay circuit 43 is opened and power to the electric motor 12 is supplied. Supply is cut off. When the ignition switch is turned off, a power relay (not shown) is cut off, power supply to each part is finished, and the steering assist control process is finished.

Next, the operation of the first embodiment will be described.
When the ignition switch is turned on, the microcomputer 16 controls a power relay (not shown) to be turned on, and power supply to each unit is started, the microcomputer 16 first performs a disconnection check process shown in FIG. A motor drive current I _MC for disconnection check is output to the FET gate drive circuit 21.

In FET gate driving circuit 21 receives this, controls the driving of the respective field effect transistor FET1~FET4 to perform the energization of the motor driving current I _MC equivalent. Motor relay circuit 43, the constructed circuit of normally closed, the motor driving current I _MC corresponding energization is performed on the electric motor 12 via a motor relay circuit 43. Since the motor driving current I _MC for checking disconnection is set to a value corresponding to a current value at which the electric motor 12 does not rotate, even if the electric motor 12 is energized, the electric motor 12 does not rotate. Therefore, since the steering assist force does not act on the steering shaft, the steering shaft does not move arbitrarily even though the driver is not steering, and the driver does not feel uncomfortable.

At this time, when the disconnection or the like does not occur in the motor system, the potential difference between both ends of the relay contact 41 shows a normal value (steps S12 and S13), so the relay terminal voltage Δvr is normal, that is, the disconnection is It is determined that it has not occurred, the process proceeds from step S13 to step S14, and the disconnection check process is terminated.
Since the result of the disconnection check is normal, the process proceeds from step S2 in FIG. 3 to step S3. Thereafter, the steering assist force corresponding to the driver's steering operation based on the detection signals of the torque sensor 3 and the vehicle speed sensor 15 The motor drive control process for generating is performed. At this time, the motor system monitoring process is performed based on the difference between the motor current detection value I _MD detected by the motor current detection circuit 19 and the motor drive current I _M output to the FET gate drive circuit 21 (step S4). If these differences are smaller than the threshold value, it is determined that the motor system is normal, the process returns from step S5 to step S6 to step S3, and the motor drive control process continues.

If any abnormality such as disconnection or short-circuit failure occurs during the motor drive control process, the difference between the motor current detection value I _MD and the motor drive current I _M increases and exceeds the threshold value. Therefore, at this time, it is determined that the motor system is abnormal, the process proceeds from step S5 to step S8, the relay off signal Ss is output to control the motor relay circuit 43 to the open state, the alarm device 50 is activated, and the voice In addition, the driver is notified that an abnormality has occurred by turning on a warning light or the like.

For this reason, since electric power is not supplied to the electric motor 12, the electric motor 12 does not act as an electromagnetic brake, and does not hinder the driver's steering operation.
On the other hand, when a foreign object is caught in the relay contact 41 of the motor relay circuit 43 at the time of starting, the motor relay circuit 43 is in an open state. The inter-voltage Δvr becomes smaller than the threshold value. For this reason, the process proceeds from step S13 in FIG. 4 to step S15, and the motor relay 40 is controlled to open and close several times. As a result, when the foreign matter caught between the relay contacts 41 is removed, the motor relay circuit 43 is closed, so that the voltage Δvr between the relay terminals at both ends of the relay contact 41 becomes a normal value. Therefore, the result of the disconnection check is determined to be normal, the process proceeds from step S17 to step S14, the disconnection check process is terminated, and thereafter, the motor drive control process is performed in the same manner as described above.

  On the other hand, if the foreign matter sandwiched between the relay contacts 41 is not removed even if the motor relay circuit 43 is controlled to open and close several times, or if a disconnection occurs at another location, the relay terminal voltage Δvr is a normal value. Therefore, the process proceeds from step S17 to step S18, the relay OFF signal Ss is output, the alarm device 50 is activated, and the abnormality notification process for notifying the driver of the abnormality is executed. At this time, since the power supply to the electric motor 12 is stopped, even if a short circuit failure occurs in any of the field effect transistors, the electric motor 12 does not act as an electromagnetic brake. There is no hindrance to the steering operation.

Thus, since the disconnection check is performed at the time of start-up, it is possible to detect a disconnection abnormality at a point before the actual drive control of the electric motor 12.
Further, since the motor relay circuit 43 is configured by a normally closed circuit, the closed state is maintained unless any abnormality occurs. For this reason, since the opportunity for foreign matter etc. to be caught in the relay contact 41 is only when an abnormality has occurred in the system, the possibility of foreign matter being caught can be reduced. Therefore, it is possible to reduce the possibility that the system is determined to be abnormal due to the motor relay circuit 43 not operating normally due to the influence of foreign matter even though the system itself is normal.

  In addition, a disconnection check is performed at the time of start-up, and when the motor relay circuit 43 is not closed due to a foreign object or the like, this can be detected at this time, so that a steering assist force according to the driver's steering operation is generated. An abnormality can be detected at an earlier stage before starting. Also, when an abnormality occurs in the disconnection check, the motor relay circuit 43 is opened / closed. Therefore, when a foreign object is caught in the relay contact 41, the foreign object can be removed at this point. , The reliability of the system can be improved.

  Also, since the motor relay circuit 43 is energized only when an abnormality occurs in the system, relay welding due to energization of the motor relay circuit 43, wear of the relay contact 41, etc. The chance of occurrence can be reduced, that is, the possibility of occurrence of relay welding or wear can be reduced. Further, when the motor relay circuit 43 is energized to the extent that relay welding occurs, this abnormality can be detected by the motor system monitoring process in step S3 of FIG. 3, and the abnormality is detected. Sometimes, at this time, the motor relay circuit 43 is controlled to be in the open state, and the power supply to the electric motor 12 is stopped, so that occurrence of relay welding can be reliably avoided.

Moreover, since the opportunity for the motor relay circuit 43 to be in the open state can be reduced as described above, the opportunity for generating an operating sound when the motor relay circuit 43 is operated can be reduced.
Further, as described above, since the motor relay circuit 43 can be realized by using a normally closed circuit, the motor relay circuit is changed in the conventional circuit configuration, and the processing procedure of the steering assist control process is changed. This can be easily realized.
In the first embodiment, when an abnormality is detected in the disconnection check process, the motor relay circuit 43 is opened and closed several times in step S15, and then the abnormality determination of the relay terminal voltage Δvr is performed again in step S16. However, for example, each time an opening / closing operation is performed, an abnormality determination may be performed, and this operation may be repeated up to a predetermined number of times.

Next, a second embodiment of the present invention will be described.
In the second embodiment, as shown in FIG. 5, the controller 13 in the first embodiment is provided with a signal monitoring circuit 26 for monitoring the relay-off signal Ss.
As shown in FIG. 5, the signal monitoring circuit 26 includes a pnp bipolar transistor TR1 as an applied voltage control active element and a monitoring npn bipolar transistor TR2 for monitoring the relay-off signal Ss in series. An internal voltage Vb is applied to the emitter terminal of the connected bipolar transistor TR1, and the emitter terminal of the bipolar transistor TR2 is grounded. The potential between the bipolar transistors TR1 and TR2 is applied to one end of the relay coil 42, and the potential is monitored by the monitor circuit 26a. The monitoring result in the monitor circuit 26a is input to the microcomputer 16 via the A / D converter.

The relay-off signal Ss from the microcomputer 16 is applied to the base terminal of the bipolar transistor TR1, and the monitor signal Sm from the microcomputer 16 is input to the base terminal of the bipolar transistor TR2.
FIG. 6 is a flowchart showing a processing procedure of steering assist control processing executed by the microcomputer 16 in the second embodiment. In the steering assist control process in the second embodiment, a signal check process in step S20 is added to the steering assist control process in the first embodiment shown in FIG.

In the second embodiment, when the microcomputer 16 is activated, it first performs a signal check process in step S20, then proceeds to step S1, and thereafter performs the same process as in the first embodiment. .
In the signal check process, as shown in FIG. 7, first, the monitor signal Sm is output (step S21), and after waiting for the time required for the bipolar transistor TR2 to be turned on, the relay off signal Ss is output. (Step S22). Thus, after the bipolar transistor TR2 is turned on, the bipolar transistor TR1 is turned on.

  Next, the process proceeds to step S23, and the potential between the resistors R1 and R2 detected by the monitor circuit 26a is read as a monitor signal. At this time, since the bipolar transistors TR1 and TR2 are in the on state, the potential obtained by dividing the internal voltage Vb applied to the emitter terminal of the bipolar transistor TR1 by the resistor R1, the resistor R2, and the combined resistance of the relay coil 42 is Will appear.

  Next, the process proceeds to step S24, and it is determined whether or not the monitor signal exceeds a preset threshold value. The threshold is determined based on the potential obtained by dividing the internal voltage Vb applied to the emitter terminal of the bipolar transistor TR1 by the resistor R1, the resistor R2 and the combined resistance of the relay coil 42, and the relay off signal Ss is bipolar. It is set to a value that can be regarded as a normal signal that can turn on the transistor TR1.

  When the monitor signal exceeds the threshold value, it is determined that the relay-off signal Ss is normal, the process proceeds from step S24 to step S25, and the output of the relay-off signal Ss to the bipolar transistor TR1 is stopped. Then, after the time corresponding to the time required for the bipolar transistor TR1 to switch to the off state has elapsed, the output of the monitoring signal Sm to the bipolar transistor TR2 is stopped (step S26), and the signal check process is terminated. Accordingly, after the bipolar transistor TR1 is switched to the off state, the bipolar transistor TR2 is turned off.

  On the other hand, if the monitor signal does not exceed the threshold value in step S24, it is determined that the relay off signal Ss is abnormal, the process proceeds to step S27, the alarm device 50 is activated, and the relay off signal Ss is abnormal. Notify the driver. Here, the alarm device 50 in the second embodiment includes at least warning display means such as a display panel and a warning light for warning the driver that the relay-off signal Ss is abnormal. When the abnormality of the relay-off signal Ss is detected, this warning display means is operated, and thereafter the driver is continuously warned that the relay-off signal Ss is abnormal.

In step S25, the bipolar transistor TR1 is turned off, and in step S26, the bipolar transistor TR2 is turned off, and the process ends.
Here, when the bipolar transistor TR1 is turned on while the bipolar transistor TR2 is turned off, the internal voltage Vr is applied to the relay coil 42 via the resistor R1, and the motor relay circuit 43 is controlled to be opened. there is a possibility. In order to avoid this, after the bipolar transistor TR2 is turned on, the bipolar transistor TR1 is turned on so that the motor relay circuit 43 does not operate. For the same reason, when the bipolar transistors TR1 and TR2 are turned off, the bipolar transistor TR2 is turned off after the bipolar transistor TR1 is turned off.

Next, the operation of the second embodiment will be described.
When the ignition switch is turned on and power supply to each part is started, the microcomputer 16 first performs a signal check process shown in FIG. 7 and outputs a monitor signal Sm and a relay-off signal Ss in this order (step S21). , S22). Thus, after the bipolar transistor TR2 is turned on, the bipolar transistor TR1 is turned on, and the potential between the resistors R1 and R2 is detected by the monitor circuit 26a, and this is output as a monitor signal.

  The microphone computer 16 reads this monitor signal (step S23) and determines whether this is normal. If the normal relay off signal Ss is output and the bipolar transistor TR1 is controlled to be in the on state, the monitor signal is a potential equivalent value determined by the resistance equivalent values of the resistors R1, R2 and the relay coil 42 and the internal voltage Vb. Since the threshold value is exceeded, it is determined that the monitor signal is normal, the output of the monitor signal Sm and the relay-off signal Ss is stopped in this order, and the bipolar transistors TR1 and TR2 are turned off in the order of the bipolar transistors TR2 and TR1. The signal check process is completed after switching.

  Returning to FIG. 6, the process proceeds to step S <b> 1, and thereafter, a disconnection check is performed in the same manner as in the first embodiment. If the result is normal, detection signals from the torque sensor 3 and the vehicle speed sensor 15 The motor drive control process is executed based on the above, and the steering assist force corresponding to the driver's steering operation is generated. On the other hand, if it is abnormal as a result of the disconnection check, this is notified to the driver and the process is terminated.

  On the other hand, if there is an abnormality as a result of the signal check process in step S21, that is, if a predetermined voltage signal is not output as the relay-off signal Ss, or if the bipolar transistor TR1 is abnormal, the potential between the resistors R1 and R2 Is not a predetermined potential and the monitor signal does not exceed the threshold value, the process proceeds from step S24 to step S27, the alarm device 50 is activated, and a display for warning that the relay-off signal Ss is abnormal. After the warning display means such as the lamp and the display panel is operated, the bipolar transistors TR1 and TR2 are switched to the OFF state in this order.

Then, since the signal check process is completed, the process proceeds to step S1 in FIG. 6, and then a disconnection check is performed. If the result of the disconnection check is normal, the detection signals of the torque sensor 3 and the vehicle speed sensor 15 are used thereafter. Based on this, a steering assist force corresponding to the driver's steering operation is generated.
At this time, an abnormality is detected in the signal check process, but this abnormality is an abnormality of the relay-off signal Ss system for controlling the motor relay circuit 43 to the open state. As described above, the motor relay circuit 43 is configured by a normally closed circuit and normally maintains a closed state. Accordingly, when the motor relay circuit 43 is not in the open control state, that is, when no abnormality has occurred in the motor system, the motor relay circuit 43 is opened even if there is an abnormality in the relay-off signal Ss system. Since there is no need to do this, there is no problem, and there is no problem in executing the motor drive control process.

Therefore, although there is an abnormality in the relay-off signal Ss system, the motor drive control process can be performed, that is, the steering assist force can be generated in a situation where there is no influence when performing the motor drive control process itself. Therefore, the situation where the steering assist force can be generated can be expanded, and the system can be operated effectively.
Further, when there is an abnormality in the relay-off signal system, the alarm device 50 notifies the driver of this, so that the driver can be promptly responded to the abnormality of the relay-off signal system while generating the steering assist force. Can be encouraged.
Needless to say, the same effects as those of the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described.
In the third embodiment, as shown in FIG. 8, in the controller 13 in the second embodiment, a voltage detection circuit 27 between motor terminals is provided instead of the voltage detection circuit 25 between relay terminals. Yes. In addition to the motor relay circuit 43, a normally closed motor relay circuit 43a having the same configuration as the motor relay circuit 43 is provided. The motor relay circuit 43a is provided between the H bridge circuit 20 and the motor 12. It is inserted in a power supply line different from the power supply line in which the motor relay circuit 43 is inserted.

That is, one end of the relay contact 41a constituting the motor relay circuit 43a is connected to a connection point between the field effect transistors FET1 and FET3, and the other end is connected to the other terminal of the electric motor 12. One end of the motor coil 42a constituting the motor relay circuit 43a is connected to the connection point of the resistors R1 and R2, and the other end is grounded.
The voltage detection circuit 27 between the motor terminals detects a potential difference between the connection point of the field effect transistors FET1 and FET3 and the connection point of the field effect transistors FET2 and FET4, and uses this as a motor terminal voltage Δvm. This motor terminal voltage Δvm is input to the microcomputer 16 via the A / D converter.

The microcomputer 16 executes the steering assist control process according to the processing procedure shown in FIG. 6 as in the second embodiment. In the third embodiment, the signal check process in step S21 is performed as shown in FIG. The procedure shown in FIG.
That is, as shown in FIG. 9, after outputting the motor drive current I _MC for disconnection check in step S11, the process proceeds to step S12a, and the motor terminal voltage Δvm from the motor terminal voltage detection circuit 27 is read. A disconnection check is performed based on whether or not the motor terminal voltage Δvm is larger than a preset threshold value (step S13a).
Voltage Δvm motor terminal when the motor terminal voltage Δvm is larger than the threshold value is determined to be normal, the process proceeds from step S13a to step S14, stops the output of the motor drive current I _MC for disconnection check, each unit Then, a process at the end of the disconnection check such as a state where the motor drive control process can be started is performed.

On the other hand, when the motor terminal voltage Δvm is equal to or lower than the threshold value, it is determined that the motor terminal voltage Δvm is abnormal, that is, there is a possibility of disconnection, and the process proceeds to step S15 and the relay off signal Ss is counted. The motor relay circuits 43 and 43a are opened and closed several times. Thereafter, the process proceeds to step S16a, and the voltage between the motor terminals Δvm is read again from the motor terminal voltage detection circuit 27 to determine whether it is normal (step S17a). If it is normal, the process proceeds to step S14 to check for disconnection. Exit, if it is abnormal, the process proceeds to step S18, stops the output of the motor driving current I _MC for the disconnection check. In addition, a relay-off signal Ss is output, and the alarm device 50 is activated to notify the driver that an abnormality has occurred in the motor system by turning on a sound or a warning light provided near the driver's seat. Then, this state is maintained until the ignition switch is turned off. When the ignition switch is turned off, the power relay (not shown) is cut off, and the steering assist control process is ended.

Here, the motor relay circuits 43 and 43 a are inserted in both of the power supply lines to the electric motor 12. Therefore, even if one of the motor relay circuits 43 and 43a does not operate due to relay welding, disconnection, foreign matter, or the like, the other operates, so the reliability can be further improved.
Further, it is possible to prevent malfunction of the motor relay circuits 43 and 43a by reducing the occurrence of welding and mixing of foreign substances in this manner, and reliability of the power supply cutoff operation to the electric motor 12 by duplication. Therefore, even if relay welding or disconnection occurs, it can be dealt with reliably. Therefore, the relay welding check and disconnection check of the motor relay circuits 43 and 43a at the time of start-up can be omitted. it can.

In addition, it is possible to reduce the chance of energization that causes relay welding in the motor relay circuits 43 and 43a and to improve the reliability of the power supply cutoff operation. It is possible to omit the check for relay welding.
In the third embodiment, the case where the disconnection check is performed based on the potential difference Δvm between the terminals of the electric motor 12 has been described. However, the present invention is not limited to this, and is the same as in the second embodiment. It is also possible to detect a potential difference Δvr between the terminals of the motor relay circuits 43 and 43a by the procedure and perform a disconnection check based on the detected potential difference Δvr.

Further, the third embodiment is applied to the second embodiment, and instead of the potential difference Δvr between the terminals of the motor relay circuit 43, the potential difference Δvm between the terminals of the electric motor 12 is detected and based on this. It is also possible to perform a disconnection check.
Here, in each of the above embodiments, the motor system monitoring process in step S4 in FIGS. 3 and 6 corresponds to the abnormality monitoring means, and the process in step S8 in FIGS. 3 and 6 corresponds to the motor relay control means. Yes.

Further, the relay terminal voltage detection circuit 25 and the motor terminal voltage detection circuit 27 correspond to the terminal voltage detection means, the disconnection check processing in step S1 of FIGS. 3 and 6 corresponds to the disconnection check means, and FIG. The process of step S16 corresponds to the opening / closing control means.
7 corresponds to the relay-off signal abnormality detection means, and the alarm device 50 corresponds to the alarm means.

It is a schematic block diagram which shows the 1st Embodiment of this invention. FIG. 2 is a block diagram illustrating a specific configuration of the controller in FIG. 1. It is a flowchart which shows an example of the process sequence of the steering assistance control process performed with the microcomputer of FIG. It is a flowchart which shows an example of the process sequence of the disconnection check process of step S1 of FIG. It is a circuit diagram which shows the 2nd Embodiment of this invention. It is a flowchart which shows an example of the process sequence of the steering assistance control process in 2nd Embodiment. It is a flowchart which shows an example of the process sequence of the signal check process in FIG.6 S20. It is a circuit diagram which shows the 3rd Embodiment of this invention. It is a flowchart which shows an example of the process sequence of a disconnection check process in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Torque sensor 8 Steering gear 10 Reduction gear 12 Electric motor 13 Controller 15 Vehicle speed sensor 16 Microcomputer 18 Motor drive circuit 19 Motor current detection circuit 20 H bridge circuit 21 FET gate drive circuit 25 Voltage detection between relay terminals Circuit 26 Signal monitoring circuit 27 Motor terminal voltage detection circuit 41, 41a Relay contact 42, 42a Relay coil 43, 43a Motor relay circuit 50 Alarm device TR, TR1, TR2 Bipolar transistor

Claims (5)

An electric motor for applying a steering assist force to the steering system;
A motor drive circuit for driving the electric motor;
A normally closed motor relay circuit that cuts off a power supply line from the motor drive circuit to the electric motor;
An abnormality monitoring means for monitoring abnormality of a motor system for driving and controlling at least the electric motor;
Motor relay control means for controlling the motor relay circuit according to the monitoring result of the abnormality monitoring means,
The electric power steering control device, wherein the motor relay control means controls the motor relay circuit to an open state when an abnormality is detected by the abnormality monitoring means. The abnormality monitoring means includes
An inter-terminal voltage detection means for detecting at least one of the inter-terminal voltage of the motor relay circuit and the inter-terminal voltage of the electric motor;
A disconnection check means for controlling the motor drive circuit at the time of start-up to pass a current for disconnection check to the electric motor and performing a disconnection check based on a detection result of the inter-terminal voltage detection means at this time; The electric power steering control device according to claim 1, wherein: The motor relay control means includes an opening / closing control means for opening / closing the motor relay circuit when an abnormality is detected by a disconnection check at startup in the disconnection check means,
When the abnormality monitoring means detects an abnormality in the disconnection check, the opening / closing control means is operated as a possibility of disconnection,
3. The electric power steering control device according to claim 2, wherein when the abnormality is detected even when the motor relay circuit is opened and closed a predetermined number of times, it is determined as a disconnection abnormality.   The electric power steering according to any one of claims 1 to 3, wherein the motor relay circuit is inserted in each power supply line between the electric motor and the motor drive circuit. Control device. The motor relay circuit is controlled to open and close by a relay-off signal from the motor relay control means,
The abnormality monitoring means includes a relay off signal abnormality detection means for determining whether the relay off signal is normal at start-up,
The motor relay control means has an alarm means for notifying the abnormality of the relay off signal, and when the abnormality of the relay off signal is detected by the relay off signal abnormality detection means, the motor relay circuit is maintained in a closed state. The electric power steering control device according to any one of claims 1 to 4, wherein the alarm means is operated as it is.

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