JP2009120097A - Control device for steering device - Google Patents

Abstract

Provided is a control device for a steering device that has a backup function for a main power source and can cope with a failure of an auxiliary power source with a minimum cost increase and a space increase.
A main power source that supplies power to a motor of a vehicle steering apparatus, a plurality of switchable auxiliary power sources that can supply power to the motor, and power supplied to the motor by the auxiliary power source. And a control circuit for controlling. The control unit has a main power supply failure determination unit that determines whether or not the main power supply has failed and causes the auxiliary power supply to supply power to the motor when it is determined that the main power supply has failed. ing. The total storage capacity of the plurality of auxiliary power supplies is 2000 to 3000J.
[Selection] Figure 1

Description

  The present invention relates to a control device for a steering device. More specifically, the present invention relates to a control device in a steering device that uses the driving force of an electric motor.

  An electric power steering device mounted on a vehicle such as an automobile needs to pass a larger current through the motor as the required steering assist force is larger. Therefore, power is usually supplied to the motor from the in-vehicle battery, which is the main power source. However, when the terminal voltage of the main power source decreases due to an increase in load such as when entering the garage or parking, the auxiliary power previously stored is stored A configuration has been proposed in which power is supplied from a power source to reduce the burden on the main power source (see, for example, Patent Documents 1 and 2).

JP 2003-320942 A JP 2005-287222 A

  In the electric power steering apparatus provided with the above-described auxiliary power supply, as a fail-safe measure when the auxiliary power supply fails, it is conceivable to arrange the auxiliary auxiliary power supply in a switchable manner in parallel with the main auxiliary power supply.

  On the other hand, the in-vehicle battery that is the main power source may also have a failure such as an extremely low voltage for some reason. When the in-vehicle battery breaks down, the power supplied from the electric power steering device is insufficient, and a stable steering assist force cannot be obtained continuously. For this reason, it is conceivable to provide the auxiliary power supply with a backup function of the main power supply.

  However, the amount of energy necessary for backing up the main power source is larger than the amount of energy originally required for the auxiliary power source, that is, the amount of energy necessary for peak cut of electric power for steering assist. Therefore, if both the above-described switchable auxiliary power supplies have a storage capacity capable of backing up the main power supply, the burden on cost and space increases.

  The present invention has been made in view of such circumstances, and has a minimum cost increase and space increase, and has a backup function for a main power supply and can also handle a failure of an auxiliary power supply. The object is to provide a device.

A control device for a steering device of the present invention (hereinafter also simply referred to as “control device”) includes a main power source that supplies electric power to a motor of a steering device of a vehicle,
A plurality of switchable auxiliary power supplies capable of supplying power to the motor;
And a control circuit for controlling the power supplied to the motor by the auxiliary power source,
The control circuit determines whether or not the main power supply has failed, and when determining that the main power supply has failed, the control circuit includes a main power supply failure determination unit that causes the auxiliary power supply to supply power to the motor. And
The total of the storage capacities of the plurality of auxiliary power supplies is 2000 to 3000J.

  The control device of the present invention has a plurality of auxiliary power supplies, and the total storage capacity of the plurality of auxiliary power supplies is set to 2000 to 3000J. Since a plurality of auxiliary power supplies are provided, even if a failure occurs in some of the auxiliary power supplies, the remaining auxiliary power supplies can supply steering assist power to the motor. Therefore, the necessary steering assist force can be stably obtained, and the reliability of the apparatus can be improved.

  The total storage capacity of the plurality of auxiliary power supplies is set to 2000 to 3000 J. This amount of 2000 to 3000 J is determined by the main power supply failure determining unit to have a failure of the main power supply, as will be described later. This corresponds to the electric power for generating the steering assist force necessary for moving the vehicle to a safe position. Therefore, even if the main power supply fails, the electric power stored in the auxiliary power supply is supplied to the motor, and the electric power steering device is continuously steered for a certain period of time until the vehicle is moved to a safe position. Auxiliary force can be generated.

  In this case, in the control device according to the present invention, on the assumption that the failure of the main power supply and the auxiliary power supply occurs at the same time is extremely small and can be ignored, each auxiliary power supply stores power for backup of the main power supply. The sum of the storage capacities of a plurality of auxiliary power sources that can be switched is set to 2000 to 3000J, rather than having a capacity. When the main power supply fails, these auxiliary power supplies are sequentially switched and used to obtain the steering assist force necessary to move the vehicle to a safe position. That is, since the main power source is backed up by the whole auxiliary power source, the capacity of each auxiliary power source can be kept small. Therefore, an increase in cost and space for minimizing the backup of the main power supply and handling the failure of the auxiliary power supply can be minimized.

  It is preferable that the control circuit is configured to use a plurality of auxiliary power supplies alternately. By alternately switching and using a plurality of auxiliary power supplies, the number of charges and discharges of each auxiliary power supply, and consequently the lifespan, can be made uniform, and the replacement times can be made uniform, facilitating maintenance.

  According to the control device for a steering device of the present invention, it is possible to have a backup function of the main power supply and cope with a failure of the auxiliary power supply with a minimum increase in cost and space.

Hereinafter, embodiments of a control device of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a circuit diagram of a control device 2 of an electric power steering device 1 according to an embodiment of the present invention. In the figure, a steering assist force is applied to a vehicle steering device 1s by a motor 1m. More specifically, the motor 1m is driven and controlled according to the output (steering torque) of a torque sensor such as a torsion bar type attached to a steering shaft (not shown) of the steering device 1s, and the steering shaft or steering gear (rack) Assist to pinion, rack shaft, etc. The motor drive circuit 3 supplies power to the motor 1m.

  The main power supply 4 is composed of an in-vehicle battery 4b and an alternator 4a, and a diode 6 is provided in the middle of a non-grounded electric circuit 5 that guides the main power supply 4 to the motor drive circuit 3. . A smoothing electrolytic capacitor 8 is provided between the cathode of the diode 6 and the ground side electric circuit 7. A voltage detector 33 is connected between the non-grounded electric circuit 5 and the grounded electric circuit 7 of the in-vehicle battery 4b. The voltage detector 33 outputs power that can be supplied by the main power supply 4 as a voltage value V.

  On the other hand, the auxiliary power source 9 includes two auxiliary power sources 9a and 9b connected in parallel to each other, and each auxiliary power source 9a and 9b is constituted by an electric double layer capacitor (capacitor). The auxiliary power supplies 9 a and 9 b are connected in series to the main power supply 4. In addition to the electric double layer capacitor (capacitor), a secondary battery such as a lithium ion battery or a nickel cadmium battery, or a capacitor can be used as the auxiliary power source.

  A power feeding circuit (high potential side circuit) 10 of the auxiliary power source 9 is connected to the motor driving circuit 3 via a discharge control circuit 11. The discharge control circuit 11 includes a MOS-FET 11a and a PWM voltage source 11b. The discharge current can be controlled by PWM controlling the gate voltage. The anode of the diode 13 is connected to the low potential side of the auxiliary power supply 9 via the reactor 12, and the cathode of the diode 13 is connected to the power supply circuit 10 of the auxiliary power supply 9. In addition, a MOS-FET 14 is provided between the anode of the diode 13 and the ground-side electric circuit 7. The protective diode 14d is connected in parallel to or built in the MOS-FET 14. The gate of the MOS-FET 14 is driven by the gate drive circuit 20.

Switching means 30a and 30b are respectively arranged between the auxiliary power supplies 9a and 9b and the non-grounded electric circuit 5, and these switching means 30a and 30b are opened and closed independently from each other by a control circuit described later. Be controlled. The switch means 30a and 30b are normally “closed” (when the auxiliary power supply is not used).
A current detector 31 that detects a discharge current from the auxiliary power supply 9 is disposed in the power feeding circuit 10. In addition, voltage detectors 32a and 32b for detecting the voltage between the terminals of the auxiliary power supplies 9a and 9b are provided. Each signal from the current detector 31 and the voltage detectors 32 a and 32 b is transmitted to the control circuit 15.

  The motor drive circuit 3, the discharge control circuit 11 and the gate drive circuit 20 operate in response to a command signal from the control circuit 15. The control circuit 15 is adapted to receive information on the steering torque of the steering wheel by the driver and the vehicle speed, and the control circuit 15 generates appropriate steering assist force in accordance with the information. The motor 1m is driven.

  When the MOS-FET 14 is in the on state, current flows from the alternator 4a through the reactor 12 and the MOS-FET 14, but when the MOS-FET 14 turns off, a high voltage is applied to the reactor so as to prevent magnetic flux change due to current interruption. Thus, the auxiliary power supply 9 is charged with a voltage obtained by boosting the output of the alternator 4a. In this way, the auxiliary power supply 9 can be charged by repeatedly turning on and off the MOS-FET 14.

  In the above configuration, when the required steering assist force is relatively small, the control circuit 15 turns off the discharge control circuit 11. Therefore, the voltage of the main power supply 4 is smoothed by the smoothing capacitor 8 and then supplied to the motor drive circuit 3. The motor drive circuit 3 drives the motor 1 m based on the control signal from the control circuit 15. On the other hand, the voltage of the auxiliary power supply 9 is not supplied to the motor drive circuit 3.

  Further, when the required steering assist force is relatively large and cannot be covered by the main power supply 4 alone, the control circuit 15 turns on the discharge control circuit 11. As a result, the current defined by the discharge control circuit 11 is supplied to the motor drive circuit 3 based on the voltage of the main power supply 4 and the auxiliary power supply 9 in series with each other.

  In the present embodiment, two auxiliary power supplies 9 a and 9 b connected in parallel to each other are used as the auxiliary power supply 9. The total storage capacity of the two auxiliary power supplies 9a and 9b is set to 2000 to 3000 joules (J). The storage capacities of the two auxiliary power supplies 9a and 9b may be the same or different from each other. However, since the number of parts can be reduced and the parts can be shared, Preferably there is.

The control circuit 15 is connected to the voltage detector 33 and constantly detects a voltage value V as power that can be supplied from the main power supply 4. Based on the voltage value V, the control circuit 15 determines whether or not the main power supply 4 has failed, and functionally includes a main power supply failure determination unit 15a that controls each circuit according to the determination. Yes.
Here, “failure of the main power supply 4” means, for example, that the alternator 4a and the battery 4b lose their functions, and the main power supply cannot be supplied to drive the motor 1m. 4 is a state in which the electric power is lowered.

The control circuit 15 causes the main power supply failure determination unit 15a to determine whether or not the voltage value V output from the voltage detector 33 is greater than a predetermined value.
Here, as described above, the predetermined value is set to the voltage value V that has been lowered to such an extent that the motor 1m cannot be driven and the main power supply 4 can be determined to have failed. The That is, the main power supply failure determination unit 15a determines whether or not the main power supply 4 has failed by determining whether or not the voltage value V of the voltage detector 33 is greater than a predetermined value.

When it is determined that the voltage value V is greater than the predetermined value (the main power supply 4 has not failed), the control circuit 15 performs the normal control described above.
On the other hand, when it is determined that the voltage value V is less than or equal to the predetermined value (the main power supply 4 has failed), the control circuit 15 causes the main power supply failure determination unit 15a to always turn on the discharge control circuit 11. At the same time, the switch means 30b of one auxiliary power source, for example, the auxiliary power source 9b is opened, and power is supplied from the other auxiliary power source 9a to the motor 1m.

  When the voltage detector 32a detects that the voltage across the terminals of the other auxiliary power supply 9a has fallen below the threshold, the control circuit 15 "closes" the switch means 30b of the one auxiliary power supply 9b. Then, the switch means 30a of the other auxiliary power supply 9a is "opened" to supply power from the auxiliary power supply 9b to the motor 1m.

  In this case, the total storage capacity of the auxiliary power supply 9a and the auxiliary power supply 9b is from when it is determined by the control circuit 15 (main power supply failure determination unit 15a) that the main power supply 4 has failed until the vehicle is moved to a safe position. Is set to a value (2000 to 3000J) that can supply electric power for generating the steering assist force necessary for the motor 1m.

  Therefore, even if the main power supply 4 breaks down, the electric power stored in the auxiliary power supply 9a and the auxiliary power supply 9b is supplied to the motor 1m, so that it continues for a certain time until the vehicle is moved to a safe position. Thus, a steering assist force can be generated.

Here, in the electric power steering apparatus 1 having the above-described configuration, when the main power supply 4 actually fails, the amount of electric power necessary for generating the steering assist force necessary to move the vehicle to a safe position is as follows. Consideration is based on the result of measuring the power consumption of the in-vehicle battery 4b in the vehicle actually traveling.
When the vehicle speed is low, even if the main power supply 4 breaks down, it does not cause a big problem. Therefore, here, it is considered that the vehicle is traveling at a relatively high speed and needs steering assist force. Two cases are considered, that is, a case where a sharp steering is performed (rapid steering condition) and a case where the steering is continuously performed at a substantially constant steering angle (a constant steering condition).

As the sudden steering condition, during the straight traveling at a vehicle speed of about 70 km / h, assuming that the steering wheel is steered suddenly to avoid an obstacle, for example, and the vehicle is subjected to an emergency avoidance operation, the vehicle travels under this sudden steering condition. The power consumption of the on-vehicle battery 4b was measured.
Further, as a constant steering condition, when traveling on a so-called loop bridge at a vehicle speed of 0 to about 40 km / h (in this case, it is considered that there is no vehicle evacuation space in the middle of the bridge. The power consumption of the in-vehicle battery 4b corresponding to the vehicle speed at this time was measured. This loop bridge was measured by running a double loop bridge with a total length of 1.1 km, a height of 45 m, and a diameter of 80 m.
Further, when measuring the power consumption of the in-vehicle battery 4b under both conditions, the power consumption by the electric power steering device 1 is reduced by not operating other devices mounted on the vehicle. It was set so as to greatly influence the power consumption.

As a result, under rapid steering conditions, power consumption in the vicinity of about 70 km / h where the avoidance operation was performed was about 500 W. Assuming that the time required for the emergency avoidance operation required for moving the vehicle to a safe place is 5 seconds, approximately 2500 J (500 (W) × 5 (seconds) is required to perform the emergency avoidance operation. ) Is required.
Under constant steering conditions, the power consumption of the in-vehicle battery 4b was about 40 W at the maximum when the vehicle speed was about 40 km / h. Assuming that the time required to cross the loop bridge and move the vehicle to a safe place is 60 seconds, an electric energy of about 2400 J (40 (W) × 60 (seconds)) may be required. I understand.

  As mentioned above, although it changes with vehicle types etc., in the case of a general passenger car, usually, if there is an electric energy of 2000-3000J, it is necessary to move the vehicle to a safe position after it is determined that the main power supply 4 has failed. It became clear that electric power for generating the steering assist force can be supplied to the motor 1m.

In the present embodiment, the voltage detectors 32a and 32b detect the voltages between the terminals of the auxiliary power supplies 9a and 9b, and a failure of the auxiliary power supplies 9a and 9b is detected by an abnormality (abrupt decrease, etc.) of this voltage. It is configured to be able to. And it is comprised so that electric power may be supplied from the auxiliary power supply except the auxiliary power supply by which the failure was detected by the voltage detector which is a failure detection means. As a result, even if one of the plurality of auxiliary power supplies fails, the assist can be continued with the remaining normal auxiliary power supplies, and the output reduction at the time of the failure can be minimized. The detection of the failure can be performed, for example, by sequentially closing only one of the switch means 30a and 30b by the control circuit 15.
Note that the number of auxiliary power supplies is not limited to two, and can be appropriately selected according to the capacity of each auxiliary power supply or the required auxiliary power supply capacity, and may be three or more.

It is a circuit diagram of one embodiment of a control device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 1s Steering apparatus 1m Motor 2 Control apparatus 3 Motor drive circuit 4 Main power supply 4a Alternator 4b Car-mounted battery 9 Auxiliary power supply 15 Control circuit 30 Switch means 31 Current detector 32 Voltage detector 33 Voltage detector

Claims (2)

A main power source for supplying electric power to a motor of a vehicle steering device;
A plurality of switchable auxiliary power supplies capable of supplying power to the motor;
And a control circuit for controlling the power supplied to the motor by the auxiliary power source,
The control circuit determines whether or not the main power supply has failed, and when determining that the main power supply has failed, the control circuit includes a main power supply failure determination unit that causes the auxiliary power supply to supply power to the motor. And
The steering apparatus control device, wherein a total of storage capacities of the plurality of auxiliary power supplies is 2000 to 3000J.   The control device for a steering apparatus according to claim 1, wherein the control circuit is configured to use a plurality of auxiliary power supplies by alternately switching them.

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