JP2015074403A - Electrically-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-driven power steering device capable of accurately determining electric conduction/cutoff of a power supply relay, even when voltage of a battery varies to low voltage.SOLUTION: When a voltage of a motor drive circuit side terminal of the power supply relay 12 detected by a terminal voltage detection circuit 17 is lower than a predetermined value set lower than a battery voltage in engine cranking, a power supply stabilizing capacitor 14 is charged up to at least the predetermined value by a precharge circuit 15, then, the electric conduction/cutoff of the power supply relay 12 is determined by electric conduction/cutoff determination means based on the voltage of the motor drive circuit side terminal of the power supply relay 12 detected by the terminal voltage detection circuit 17 when driving the power supply relay 12 in an electric conduction state.

Description

  The present invention relates to an electric power steering apparatus including a power relay connected between a battery and a motor drive circuit, and a capacitor for stabilizing the power.

  Conventionally, in an electric power steering device equipped with a power relay connected between the battery and the motor drive circuit and a capacitor for stabilizing the power, the power relay is switched to the energized state when the ignition switch is turned on. In order to prevent inrush current (rush current) from flowing from the battery to the power stabilization capacitor, the precharge circuit charges the power stabilization capacitor before driving the power relay to the energized state. The capacitor for power stabilization is first charged by this precharge circuit, and then the power relay is switched to the energized state.

  However, in such a conventional electric power steering apparatus, an abnormality may occur in which the power relay contact remains disconnected when foreign matter is mixed into the power relay contact. Therefore, a discharge circuit is provided in addition to the precharge circuit, and after the power supply relay is energized, the precharge circuit is stopped and the charge of the capacitor for power stabilization is discharged by the discharge circuit. There has been proposed an electric power steering apparatus that includes a determination means for determining whether the power supply relay is in an energized state or a disconnected state by detecting a potential difference between both terminals of the contact (for example, Patent Documents). 1).

  According to the conventional electric power steering device disclosed in Patent Document 1, for example, when the power relay is normally energized, the charge of the capacitor for stabilizing the power supply is reduced with the precharge circuit stopped. Even if the discharge circuit discharges, the terminal voltage on the capacitor side of the contact of the power relay does not drop, but is maintained at the battery voltage. On the other hand, when the power supply relay is cut off, when the charge of the power stabilization capacitor is discharged by the discharge circuit while the precharge circuit is stopped, the voltage on the capacitor side of the contact of the power supply relay decreases. Therefore, when a potential difference is generated between both terminals of the contact of the power relay after discharging the capacitor charge while the precharge circuit is stopped, it can be determined that the power relay is cut off.

JP 2007-276706 A

  As described above, a conventional electric power steering apparatus in which after the power relay is energized, the charge of the power stabilization capacitor is discharged while the precharge circuit is stopped to determine whether the power relay is energized or interrupted. When the power relay is cut off, a voltage drop such as engine cranking occurs, and the reduced battery side voltage becomes the same potential as the capacitor side voltage after precharging. Since there is no potential difference between both terminals of the contact of the power relay, there is a problem that it may be erroneously determined that the power relay is energized even though the power relay is cut off.

  The present invention has been made to solve the above-described problems in the conventional electric power steering apparatus, and even when the battery voltage fluctuates to a low potential, such as during engine cranking. An object of the present invention is to provide an electric power steering device capable of accurately determining energization / cutoff of a power relay.

The electric power steering apparatus according to the present invention is:
An electric power steering apparatus comprising a motor for applying assist torque to a steering system, wherein the motor generates assist torque corresponding to steering torque by a driver to assist the driver's steering,
A motor drive circuit for supplying power from a battery and driving the motor;
A power relay connected between the battery and the motor drive circuit, enabling the supply of the power when in an energized state, and interrupting the supply of the power when in an interrupted state;
A capacitor connected between the motor drive circuit and the power relay;
A precharge circuit capable of charging the capacitor prior to driving the power relay to an energized state;
A terminal voltage detection circuit for detecting a voltage of a capacitor side terminal of the power relay;
Energization / interruption determining means for determining whether the power relay is energized or disconnected;
With
When the voltage detected by the terminal voltage detection circuit is lower than a predetermined value set lower than the battery voltage during engine cranking, the precharge circuit charges the capacitor to at least the predetermined value, and then the power relay Based on the voltage of the capacitor side terminal detected by the terminal voltage detection circuit when driving the power supply to the energized state, the energization / interruption determining means determines energization / interruption of the power relay,
It is characterized by that.

  According to the electric power steering apparatus of the present invention, even when the battery voltage is lowered due to engine cranking or the like, it is possible to accurately determine whether the power relay is energized or cut off.

1 is a configuration diagram showing an overall configuration of an electric power steering apparatus according to Embodiment 1 of the present invention. FIG. It is a block diagram which shows the structure of the control unit in the electric power steering apparatus by Embodiment 1 of this invention. 3 is a flowchart showing an operation of a control unit in the electric power steering apparatus according to Embodiment 1 of the present invention. 3 is a flowchart showing the operation of a power relay energization / interruption determining means in the electric power steering apparatus according to Embodiment 1 of the present invention. 4 is a timing chart for explaining the operation of driving a precharge circuit and power supply relay energization / interruption determination in the electric power steering apparatus according to Embodiment 1 of the present invention; 5 is a timing chart for explaining the operation of the discharge circuit and the power relay energization / interruption determination in the electric power steering apparatus according to Embodiment 1 of the present invention.

Embodiment 1 FIG.
Hereinafter, an electric power steering apparatus according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the overall configuration of an electric power steering apparatus according to Embodiment 1 of the present invention. In the electric power steering apparatus 100 shown in FIG. 1, the steering handle 101 includes a steering handle shaft 102, a reduction gear 103, a universal joint 104 on the handle side, a universal joint 105 on the pinion rack mechanism side, and a pinion rack. It is connected to a wheel tie rod 107 via a mechanism 106. A torque sensor 110 provided on the steering handle shaft 102 detects a steering torque applied to the steering handle 101 by the driver. A motor 120 that generates assist torque corresponding to the steering force applied to the steering handle 101 is connected to the steering handle shaft 102 via a reduction gear 103.

  The control unit 130 is supplied with power from the battery 160 via the ignition switch 150. The steering torque value detected by the torque sensor 110, the vehicle speed signal transmitted from the vehicle speed sensor, the engine signal 140 indicating the engine operating state transmitted from the engine control unit (not shown), and the like are input values. A motor control signal for controlling the motor 120 is generated to control the motor 120. The control unit 130 is mainly composed of a CPU described later, and executes control of the motor 120 by a predetermined program.

  Next, the configuration of the control unit 130 will be described. FIG. 2 is a configuration diagram showing the configuration of the control unit in the electric power steering apparatus according to Embodiment 1 of the present invention. In FIG. 2, the control unit 130 includes a CPU 10, a relay drive circuit 11, a power supply relay 12, a choke coil 13 connected between the power supply relay 12 and the battery 160, a power supply stabilization capacitor (hereinafter referred to as “power supply relay 12”). 14), a precharge circuit 15 that can charge the capacitor 14 as described later, a discharge circuit 16 that can discharge the capacitor 14 as described later, a terminal voltage detection circuit 17, and a motor 120. And a motor drive circuit 18 for driving.

  The power relay 12 includes a pair of terminals, one terminal of which is connected to the positive electrode side of the battery 160 and the other terminal is connected to the motor drive circuit 18 side, so that the battery 160 and the motor drive circuit 18 are connected. Connected between and. Then, it is possible to supply power from the battery 160 to the motor drive circuit 18 by electrically connecting the one terminal and the other terminal, and between the one terminal and the other terminal. By shutting off, supply of power from the battery 160 to the motor drive circuit 18 is stopped. In the following description, “energization” of the power relay means to electrically connect between the one terminal and the other terminal, and “cut off” of the power relay means one of the above-mentioned ones. This means that the terminal is electrically disconnected from the other terminal.

  The relay drive circuit 11 controls energization / cutoff of the power relay 12 based on a command from the CPU 10. The terminal voltage detection circuit 17 detects the voltage of a terminal (hereinafter referred to as a capacitor side terminal) connected to the capacitor 14 among the pair of terminals of the power supply relay 12. The CPU 10 controls the relay drive circuit 11, the precharge circuit 15, and the discharge circuit 16 based on the voltage at the capacitor side terminal of the power supply relay 12 detected by the terminal voltage detection circuit 17. Further, the CPU 10 determines whether the power relay 12 is energized or disconnected (hereinafter referred to as energization / interruption determination) based on the voltage at the capacitor side terminal after the power relay 12 is driven to the energized state. An energization / interruption determination unit.

  The capacitor 14 provided for stabilizing the power supply voltage supplied to the motor drive circuit 18 has one terminal connected between the power relay 12 and the motor drive circuit 18, and the other terminal connected to the ground potential portion of the vehicle. It is connected to the. The motor drive circuit 18 includes an H-type bridge circuit made up of, for example, four semiconductor switching elements. The motor 120 is driven by conducting a pair of semiconductor switch elements at the first diagonal position of the H-type bridge circuit. The motor 120 is rotated in the reverse direction by rotating forward and conducting another pair of semiconductor switching elements at the second diagonal position.

  The precharge circuit 15 is controlled by the CPU 10 as described later, and is charged from the battery 160 without passing through the capacitor 14 and the power supply relay 12. The discharge circuit 16 is controlled by the CPU 10 as will be described later, and discharges the capacitor 14. The terminal voltage detection circuit 17 detects the voltage of the capacitor side terminal of the power relay 12 and inputs the detected voltage value to the CPU 10.

  Next, the operation of the control unit 130 in the electric power steering apparatus according to Embodiment 1 of the present invention configured as described above will be described. FIG. 3 is a flowchart showing the operation of the control unit in the electric power steering apparatus according to Embodiment 1 of the present invention. In FIG. 3, first, before driving the power supply relay 12 to the energized state in step S10, the terminal voltage detection circuit 17 detects the voltage at the capacitor side terminal of the power supply relay 12, and the value becomes a predetermined value. It is determined whether or not it exceeds. Here, the predetermined value is set to a voltage equal to or lower than the lowest voltage at the time of engine cranking in a deteriorated battery and equal to or higher than the product guarantee voltage of the power supply relay 12.

  As a result of the determination in step S10, if it is determined that the voltage at the capacitor side terminal of the power supply relay 12 exceeds the predetermined value (Y), the discharge circuit 16 is driven to discharge the capacitor 14 in step S11. To do. On the other hand, as a result of the determination in step S10, if it is determined that the voltage at the capacitor side terminal of the power relay 12 is equal to or lower than the predetermined value (N), the process proceeds to step S12, where the voltage at the capacitor side terminal of the power relay 12 is It is determined whether or not it is below the predetermined value.

  If the result of determination in step S12 is that the voltage at the capacitor side terminal of the power relay 12 is below a predetermined value (Y), the precharge circuit 15 is driven to charge the capacitor 14 in step S13. On the other hand, if the result of determination in step S12 is that the voltage at the capacitor side terminal of the power relay 12 is greater than or equal to a predetermined value (N), the relay drive circuit 11 is set so that the power relay 12 is energized in step S14. In step S15, it is determined using the energization / interruption determining means whether the power supply relay 12 is energized or disconnected. The energization / interruption determining means is constituted by a predetermined program provided in the CPU 10.

  FIG. 4 is a flowchart showing the operation of the energization / interruption determining means in the electric power steering apparatus according to Embodiment 1 of the present invention. In FIG. 4, first, whether or not the voltage at the terminal after driving the power supply relay 12 in the energized state in step S20 exceeds the predetermined value lower than the battery voltage at the time of engine cranking. Determine. As a result, if it is determined that the voltage at the capacitor side terminal after driving the power relay 12 to the energized state exceeds a predetermined value (Y), the process proceeds to step S21 and the power relay 12 is in the energized state. Judge that there is. On the other hand, if it is determined that the voltage at the capacitor side terminal of the power relay 12 after driving the power relay 12 to the energized state is equal to or lower than the predetermined value (N), the process proceeds to step S22 and the power relay is in the cut-off state. Judge that there is. When it is determined that the power supply relay 12 is in the cut-off state, the power supply relay 12 is turned off using the relay drive circuit 11 and the above processing is performed a plurality of times.

  Next, the operation of the power relay energization / interruption determining means will be described using a timing chart. First, in step S10 in FIG. 3, it is determined that the voltage at the capacitor side terminal of the power relay 12 detected by the terminal voltage detection circuit 17 before driving the power relay 12 to the energized state is equal to or lower than a predetermined value. Case (N) will be described with reference to FIG. FIG. 5 is a timing chart for explaining the operation of precharge circuit driving and power relay energization / interruption determination in the electric power steering apparatus according to Embodiment 1 of the present invention. A case where it is determined that the relay 12 is energized is shown, and (B) shows a case where it is determined that the power relay 12 is cut off.

  First, a case where the energization / interruption determination unit determines that the power relay 12 is in an energized state will be described. In FIG. 5A, at time t1, the voltage at the capacitor side terminal of the power supply relay 12 before driving the relay 12 to the energized state is set lower than the battery voltage at the time of engine cranking. Therefore, the precharge circuit 15 is driven at time t1 (step S13 in FIG. 3) before the power supply relay 12 is driven to the energized state. As a result, the capacitor 14 is charged to a predetermined value from the battery 160 via the precharge circuit 15 at time t2.

  Then, when the power supply relay 12 is driven to the energized state by the relay drive circuit 11 at time t2, and the voltage at the capacitor side terminal of the power supply relay 12 after time t2 when the power relay 12 is driven to the energized state is determined (FIG. 4). Since the voltage exceeds the predetermined value in step S20), the energization / cutoff determining means determines that the power relay 12 is in the energized state (step S21 in FIG. 4).

  Next, a case where the power relay energization / interruption determining unit determines that the power relay 12 is in the interrupted state will be described. In FIG. 5B, at time t1, the voltage at the capacitor side terminal of the power relay 12 before driving the power relay 12 to the energized state is a predetermined value lower than the battery voltage at the time of engine cranking. Since it is determined that it is lower (step S12 in FIG. 3), the precharge circuit 15 is driven at time t1 (step S13 in FIG. 3) before the power supply relay 12 is driven to the energized state. As a result, the capacitor 14 is charged to a predetermined value from the battery 160 via the precharge circuit 15 at time t2.

  Then, when the power supply relay 12 is driven to the energized state by the relay drive circuit 11 at time t2, and the voltage at the capacitor side terminal of the power supply relay 12 after time t2 when the power relay 12 is driven to the energized state is determined (FIG. 4). Since the voltage is not more than the predetermined value in step S20), the energization / interruption determining means determines that the power relay 12 is in the interrupted state (step S22 in FIG. 4).

  Next, when the voltage at the capacitor side terminal of the power supply relay 12 detected by the terminal voltage detection circuit 17 before driving the power supply relay 12 to the energized state in step S10 in FIG. 3 exceeds a predetermined value. The case where it is determined (Y) will be described with reference to FIG. FIG. 6 is a timing chart for explaining the operation of the discharge circuit and the power relay energization / cutoff determination in the electric power steering apparatus according to Embodiment 1 of the present invention. 12 shows a case where it is determined that the power supply 12 is energized, and (B) shows a case where it is determined that the power supply relay 12 is cut off.

  When it is determined in step 10 of FIG. 3 that the voltage at the capacitor side terminal of the power relay 12 detected by the terminal voltage detection circuit 17 exceeds the predetermined value before driving the power relay 12 to the energized state (Y) Advances to step S11. Here, first, a case where the energization / interruption determination unit determines that the power relay 12 is in an energized state will be described. In FIG. 6A, the voltage of the capacitor side terminal of the power relay 12 before driving the power relay to the energized state exceeds the predetermined value set lower than the battery voltage at the time of engine cranking. 3 (determination result in step S10 of FIG. 3: Y), the discharge circuit 16 is driven at time t1 to start discharging the capacitor 14, and the voltage at the capacitor side terminal of the power supply relay 12 is a predetermined value at time t2. It becomes.

  Next, when the power relay 12 is driven to the energized state at time t2 and the voltage at the capacitor side terminal of the power relay 12 after the power relay 12 is driven to the energized state is determined, the voltage exceeds a predetermined value. (Determination result in step S20 in FIG. 4: Y), the energization / cutoff determination means determines that the power supply relay 12 is in the energized state (step S21 in FIG. 4).

  Next, a case where the energization / interruption determination unit determines that the power supply relay 12 is in an interrupted state will be described. In FIG. 6B, the voltage of the capacitor side terminal of the power relay 12 before driving the power relay to the energized state exceeds the predetermined value set lower than the battery voltage at the time of engine cranking. 3 (determination result in step S10 of FIG. 3: Y), the discharge circuit 16 is driven at time t1 to start discharging the capacitor 14, and the voltage at the capacitor side terminal of the power supply relay 12 is a predetermined value at time t2. It becomes.

  Next, when the power relay 12 is driven to the energized state at time t2 and the voltage of the capacitor side terminal of the power relay 12 after the power relay 12 is driven to the energized state is determined, the voltage is equal to or less than a predetermined value. For this reason (determination result in step S20 in FIG. 4: N), the energization / interruption determination means determines that the power relay 12 is in the interrupted state (step S22 in FIG. 4). As described above, when it is determined that the power supply relay 12 is in the cut-off state, the power supply relay 12 is put in the cut-off state, and the above processing is performed a plurality of times.

  As described above, according to the electric power steering apparatus according to the first embodiment of the present invention, the capacitor 14 is charged by driving the precharge circuit 15 before the determination of energization / cutoff of the power supply relay 12 is performed. Alternatively, by discharging the capacitor 14 by driving the discharge circuit 16, the voltage at the capacitor side terminal of the power relay 12 is set to a predetermined value lower than the battery voltage at the time of engine cranking, and the power relay is turned on / off. Since the determination is made, it is possible to suppress erroneous determination of the energization / interruption determination due to the battery voltage drop during engine cranking, which could not be determined by the conventional energization / interruption determination of the power relay.

  In the present invention, the embodiments can be appropriately modified or omitted within the scope of the invention.

DESCRIPTION OF SYMBOLS 100 Electric power steering apparatus, 101 Steering handle 101, 102 Steering handle shaft, 103 Reduction gear, 104 Universal joint on the handle side, 105 Universal joint on the pinion rack mechanism side, 106 Pinion rack mechanism, 107 Wheel tie rod, 110 Torque sensor, 120 motor, 130 control unit, 160 battery, 150 ignition switch, 10 CPU, 11 relay drive circuit, 12 power relay, 160 battery, 13 choke coil, 14 capacitor, 15 precharge circuit, 16 discharge circuit, 17 terminal voltage detection circuit , 18 Motor drive circuit.

The electric power steering apparatus according to the present invention is:
An electric power steering device configured to assist a driver's steering by generating an assist torque in a motor,
A motor drive circuit for supplying power from a battery and driving the motor;
A power relay connected between the battery and the motor drive circuit, enabling the supply of the power when in an energized state, and interrupting the supply of the power when in an interrupted state;
A capacitor connected between the motor drive circuit and the power relay;
A precharge circuit capable of charging the capacitor prior to driving the power relay to an energized state;
A terminal voltage detection circuit for detecting a voltage of a capacitor side terminal of the power relay;
Energization / interruption determining means for determining whether the power relay is energized or disconnected;
With
When the voltage detected by the terminal voltage detection circuit is lower than a predetermined value set lower than the battery voltage during engine cranking, the precharge circuit charges the capacitor to at least the predetermined value, and then the power relay Electric power steering wherein the energization / interruption determining means determines the energization / interruption of the power supply relay based on the voltage of the capacitor side terminal detected by the terminal voltage detection circuit when the motor is driven in an energized state A device,
The energization / interruption determining means includes
When the voltage detected by the terminal voltage detection circuit when the power relay is driven to the energized state after charging the capacitor to at least the predetermined value by the precharge circuit exceeds the predetermined value, Determine that the power relay is energized,
After the capacitor is charged to at least the predetermined value by the precharge circuit, and the voltage detected by the terminal voltage detection circuit when the power supply relay is driven to the energized state is less than the predetermined value, the power supply Determining that the relay is in a disconnected state;
It is characterized by that.

Claims (4)

An electric power steering device configured to assist a driver's steering by generating an assist torque in a motor,
A motor drive circuit for supplying power from a battery and driving the motor;
A power relay connected between the battery and the motor drive circuit, enabling the supply of the power when in an energized state, and interrupting the supply of the power when in an interrupted state;
A capacitor connected between the motor drive circuit and the power relay;
A precharge circuit capable of charging the capacitor prior to driving the power relay to an energized state;
A terminal voltage detection circuit for detecting a voltage of a capacitor side terminal of the power relay;
Energization / interruption determining means for determining whether the power relay is energized or disconnected;
With
When the voltage detected by the terminal voltage detection circuit is lower than a predetermined value set lower than the battery voltage during engine cranking, the precharge circuit charges the capacitor to at least the predetermined value, and then the power relay Based on the voltage of the capacitor side terminal detected by the terminal voltage detection circuit when driving the power supply to the energized state, the energization / interruption determining means determines energization / interruption of the power relay,
An electric power steering device. The energization / shut-off determination means is
When the voltage detected by the terminal voltage detection circuit when the power relay is driven to the energized state after charging the capacitor to at least the predetermined value by the precharge circuit exceeds the predetermined value, Determine that the power relay is energized,
After the capacitor is charged to at least the predetermined value by the precharge circuit, and the voltage detected by the terminal voltage detection circuit when the power supply relay is driven to the energized state is less than the predetermined value, the power supply Determining that the relay is in a disconnected state;
The electric power steering apparatus according to claim 1. A discharge circuit capable of discharging the capacitor;
When the voltage detected by the terminal voltage detection circuit exceeds a predetermined value set lower than the battery voltage during engine cranking, the discharge circuit discharges the capacitor to the predetermined value, and then the power source Based on the voltage detected by the terminal voltage detection circuit when the relay is driven to an energized state, the energization / interruption determination means determines the energization / interruption of the power relay.
The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is an electric power steering apparatus. The energization / shut-off determination means is
When the voltage detected by the terminal voltage detection circuit when the power supply relay is driven to an energized state after discharging the capacitor to at least the predetermined value by the discharge circuit exceeds the predetermined value, the power supply Determine that the relay is energized,
After the capacitor is charged to at least the predetermined value by the precharge circuit, and the voltage detected by the terminal voltage detection circuit when the power supply relay is driven to the energized state is less than the predetermined value, the power supply Determining that the relay is in a disconnected state;
The electric power steering apparatus according to claim 3.

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