JP2009078737A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of preventing the occurrence of insufficient output and preventing the other electrical equipments from being adversely affected. <P>SOLUTION: This electric power steering device 1 for generating steering assisting force by a motor 4 includes a main power supply 9 for supplying electric power to the motor 4, auxiliary power supply 10 for supplying electric power to the motor 4, a steering speed sensor 20 for detecting steering speed of a steering wheel 3 of the electric power steering device 1, a charging and discharging circuit 13 forming the first output state for charging the auxiliary power supply 10 based on the main power supply 9 and supplying electric power to the motor 4 by only the main power supply 9 and the second output state for supplying electric power to the motor 4 from the main power supply 9 and the auxiliary power supply 10 selectively, and a control circuit 6 for putting the charging and discharging circuit 13 into the first output state when the steering speed detected by the steering speed sensor 20 is below the predetermined value and putting the charging and discharging circuit 13 into the second output state when the steering speed exceeds the predetermined value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that generates a steering assist force by a motor, and more particularly to a configuration of an electric circuit thereof.

  In the electric power steering device, the larger the steering assist force that is required, the greater the current that needs to flow through the motor. 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).

  In the configuration using such an auxiliary power supply, whether a predetermined power value is set as a charging / discharging threshold value, and whether the main power supply and the auxiliary power supply are supplied with reference to this charging / discharging threshold value, Switching from main power supply only, but in order to prevent unnecessary power fluctuations, the vehicle speed is used as a reference value, and at low vehicle speeds when high power is required (vehicle speeds when entering a garage or parking that requires a large steering assist force) Is usually low speed), the main power supply and the auxiliary power supply are added together to supply power, and the others are considered to be only the main power supply.

JP 2003-320942 A JP 2006-213273 A

  However, even at times other than low vehicle speeds, when the steering speed is high (such as when the course is suddenly changed to avoid an obstacle or when a relatively sharp curve is made on a mountain road), the speed is relatively high. There is a case where electric power is required, and in the switching method based on the vehicle speed, there is a possibility that the output is insufficient (assist is insufficient) or other electrical components are adversely affected by overuse of the main power source.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electric power steering device that can avoid output shortage and adverse effects on other electrical components.

An electric power steering apparatus according to a first aspect of the present invention is an electric power steering apparatus that generates a steering assist force by a motor,
A main power supply for supplying power to the motor;
An auxiliary power source capable of supplying power to the motor;
Steering speed detecting means for detecting the steering speed of the steering wheel of the electric power steering device;
A first output state for charging the auxiliary power source based on the main power source and supplying power to the motor only by the main power source; and a second output state for supplying power to the motor from the main power source and auxiliary power source A charge / discharge circuit that selectively configures the output state of
When the absolute value of the steering speed detected by the steering speed detection means is less than or equal to a predetermined value, the charge / discharge circuit is set to the first output state, and when the absolute value exceeds the predetermined value, the charge / discharge circuit is set to the second output state. And a control circuit for making an output state.

  In the electric power steering apparatus according to the first aspect of the present invention, when the absolute value of the steering speed detected by the steering speed detection means is less than or equal to a predetermined value, the first output that supplies power to the motor only by the main power supply When the steering speed exceeds the predetermined value, the second output state in which power is supplied from the main power source and the auxiliary power source to the motor is set. In this way, by determining whether or not the auxiliary power supply should be used based on the steering speed, which is a direct parameter for steering, the amount of steering and Not only the speed increases, but also when relatively high power is required due to the high steering speed (the course is suddenly changed in order to avoid obstacles, or a relatively steep curve is turned on a mountain road) In such a case, it is possible to avoid an output shortage or an adverse effect on other electrical components due to overuse of the main power source.

An electric power steering apparatus according to a second aspect of the present invention is an electric power steering apparatus that generates a steering assist force by a motor,
A main power supply for supplying power to the motor;
An auxiliary power source capable of supplying power to the motor;
A first output state for charging the auxiliary power source based on the main power source and supplying power to the motor only by the main power source; and a second output state for supplying power to the motor from the main power source and auxiliary power source A charge / discharge circuit that selectively configures the output state of
When the differential value of the steering torque detected by the torque sensor for detecting the steering torque of the steering wheel of the electric power steering device is less than or equal to a predetermined value, the charge / discharge circuit is set to the first output state and exceeds the predetermined value And a control circuit for setting the charging / discharging circuit to the second output state (Claim 2).

  Also in the electric power steering apparatus according to the second aspect of the present invention, by determining whether or not the auxiliary power source should be used on the basis of the differential value of the steering torque that is a direct parameter for steering, (Normally, the amount of steering and the steering speed increase when entering the garage or when parking), but also when relatively high power is required due to the high steering speed (suddenly to avoid obstacles) When changing the course or turning a relatively steep curve on a mountain road, etc.), it is possible to avoid insufficient output or adversely affecting other electrical components due to overuse of the main power supply. it can.

  The control circuit is configured to set the charging / discharging circuit to the second output state when the vehicle speed is equal to or lower than a predetermined value, and to set the charging / discharging circuit to the first output state when the vehicle speed exceeds the predetermined value. It is preferable. According to this configuration, in addition to the steering speed (Claim 1) or the differential value of the steering torque (Claim 2), the vehicle speed is also used as a determination criterion, so that the auxiliary power in the case where an auxiliary power source is required. The power supply can be used reliably, and the reliability of the apparatus can be further improved.

  According to the electric power steering apparatus of the present invention, it is possible to avoid an output shortage and an adverse effect on other electrical components.

Embodiments of an electric power steering apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a circuit diagram showing a schematic configuration mainly including an electric circuit of an electric power steering apparatus 1 according to an embodiment of the present invention. In FIG. 1, a steering device 2 includes a driver's steering torque applied to a steering wheel (steering wheel) 3, and a steering assist force transmitted from a motor 4 to a steering shaft 2a via a speed reducer (not shown). Driven by. The motor 4 is a three-phase brushless motor and is driven by a drive circuit 5. The control circuit 6 includes a microcomputer, determines a necessary steering assist force based on the vehicle speed signal input from the vehicle speed sensor 7 and the steering torque signal input from the torque sensor 8, and the steering assist force. Is applied to the steering shaft 2a. Further, a steering speed sensor 20 as a steering speed detecting means is disposed around the steering shaft 2a so as to face the steering shaft 2a. The rotation of the steering shaft 2a detected by the steering speed sensor 20 is provided. The speed, that is, the steering speed signal is transmitted to the control circuit 6.

  The drive circuit 5 is given a voltage of the main power supply 9 or, if necessary, a DC voltage obtained by adding the voltage of the auxiliary power supply 10 to the drive circuit 5. The main power supply 9 is composed of a battery 9B and an alternator (having a rectification and regulator function) 9A. In order to switch the discharge circuit in the middle of electric circuits L1 and L3 for guiding the voltage of the main power supply 9 to the drive circuit 5. The switch 11 is provided. On the other hand, the auxiliary power source 10 is composed of, for example, an electric double layer capacitor or a secondary battery such as a lithium ion battery, and is connected in series to the main power source 9. The output voltage obtained by connecting the auxiliary power supply 10 to the main power supply 9 in series is guided from the electric circuit L2 to the drive circuit 5 via the switch 11 and the electric circuit L3.

  The switch 11 can switch the connection under the control of the control circuit 6. In the first output state shown by the solid line, the electric circuits L1 and L3 are connected to each other, and in the second output state shown by the dotted line, the electric circuits L2 and L3 are connected to each other. The switch 11 is actually configured to realize a circuit switching function as shown using a semiconductor switching element such as a MOS-FET.

  A charging circuit 12 is connected to the auxiliary power source 10 in parallel. The charging circuit 12 has a function of boosting the voltage of the main power supply 9 and charging the auxiliary power supply 10. Whether or not the charging circuit 12 performs charging is controlled by the control circuit 6. In addition, the electric circuit L1-L3 and the switch 11 comprise the discharge circuit which can comprise either the said 1st, 2nd output state, and also added the charging circuit 12 to this, and the charge / discharge circuit 13 is comprised. Yes.

  The control circuit 6 switches the switch 11 based on the steering speed signal sent from the steering speed sensor 20 and the vehicle speed signal sent from the vehicle speed sensor 7. That is, as shown in FIG. 2, the control circuit 6 monitors the vehicle speed and the steering speed (step S1), whether or not the obtained vehicle speed is lower than a predetermined value, and the steering speed is higher than the predetermined value. Is also determined (step S2). When the control circuit 6 determines that the obtained vehicle speed is lower than the predetermined value or the steering speed is higher than the predetermined value, the control circuit 6 advances the process to step S3 and switches the switch 11 to the second line indicated by the dotted line in FIG. Set to output state. As a result, the high voltage is supplied to the drive circuit 5 with the main power supply 9 and the auxiliary power supply 10 connected in series with each other. Thereby, a required large electric power can be supplied to the drive circuit 5.

  On the other hand, in step S2, if the control circuit 6 determines that the obtained vehicle speed is equal to or higher than the predetermined value and the steering speed is equal to or lower than the predetermined value, the process proceeds to step S4, and the switch 11 is set to the solid line in FIG. The first output state shown in FIG. Accordingly, the voltage of the main power supply 9 is supplied to the drive circuit 5 via the electric circuits L1 and L3, and the drive circuit 5 drives the motor 4 based on the control signal from the control circuit 6. In this case, the power of the auxiliary power supply 10 is not supplied to the drive circuit 5. Further, the control circuit 6 monitors the voltage of the auxiliary power supply 10 by a voltage sensor (not shown) built in the charging circuit 12, and if the voltage does not reach a certain voltage, it drives the charging circuit 12. The auxiliary power supply 10 is charged.

  As the “predetermined value” of the vehicle speed, when the vehicle speed is smaller than the predetermined value, a value that is likely to require a large steering assist force can be set, for example, 10 to 20 km / h. A value within the range can be selected. When entering a garage or parking that requires a large steering assist force, the vehicle speed is temporarily reduced to a value within the above range, except for exceptions such as forward parking on a large site.

  Further, as the “predetermined value” of the steering speed, a value in the range of 45 to 90 deg / sec can be selected in the same manner. The case where the steering speed is higher than the predetermined value means that a relatively high electric power is required, for example, when the course is suddenly changed in order to avoid an obstacle or a relatively sharp curve is made on a mountain road. In such a case, by supplying power from the auxiliary power supply in addition to the main power supply, avoiding the shortage of output or adverse effects on other electrical components due to overuse of the main power supply. be able to.

  In the present embodiment, in addition to the steering speed, the vehicle speed is also used as a criterion for determining the use of the auxiliary power supply. Therefore, when the auxiliary power supply is required, the auxiliary power supply can be used reliably, Reliability can be further improved. In other words, when a large steering assist force is required, it is possible to reliably avoid burdening only the main power source, resulting in insufficient output or to other electrical components due to overuse of the main power source. It is possible to prevent the adverse effects of.

In the above-described embodiment, the steering speed is used as a criterion for determining the use of the auxiliary power source. However, instead of this steering speed, the differential value of the steering torque obtained from the torque sensor 8 is used to determine the use of the auxiliary power source. It can also be a standard.
FIG. 3 is a flowchart showing a procedure for determining the use of the auxiliary power supply in this case. The control circuit 6 monitors the vehicle speed and the steering torque (step S11), and determines whether the obtained vehicle speed is smaller than a predetermined value and whether the differential value of the steering torque is larger than a predetermined value. Is performed (step S12). If the control circuit 6 determines that the obtained vehicle speed is smaller than the predetermined value or that the differential value of the steering torque is larger than the predetermined value, the process proceeds to step S13, and the switch 11 is indicated by a dotted line in FIG. The second output state is assumed. As a result, the high voltage is supplied to the drive circuit 5 with the main power supply 9 and the auxiliary power supply 10 connected in series. Thereby, a required large electric power can be supplied to the drive circuit 5.

On the other hand, in step S12, when the control circuit 6 determines that the obtained vehicle speed is equal to or higher than the predetermined value and the differential value of the steering torque is equal to or lower than the predetermined value, the process proceeds to step S14, and the switch 11 is turned on. A first output state indicated by a solid line 1 is assumed. Accordingly, the voltage of the main power supply 9 is supplied to the drive circuit 5 via the electric circuits L1 and L3, and the drive circuit 5 drives the motor 4 based on the control signal from the control circuit 6. In this case, the power of the auxiliary power supply 10 is not supplied to the drive circuit 5. Further, the control circuit 6 monitors the voltage of the auxiliary power supply 10 by a voltage sensor (not shown) built in the charging circuit 12, and if the voltage does not reach a certain voltage, it drives the charging circuit 12. The auxiliary power supply 10 is charged.
In the embodiment described above, the steering speed sensor 20 disposed opposite to the steering shaft 2a is used as means for detecting the steering speed of the steering wheel. However, the present invention is limited to this. For example, it is also possible to detect the rotational speed of the motor and obtain the steering speed by calculation from the rotational speed.

1 is a circuit diagram showing a schematic configuration mainly including an electric circuit of an electric power steering apparatus according to an embodiment of the present invention. It is a flowchart which shows the procedure which determines use of an auxiliary power supply in one embodiment of this invention. It is a flowchart which shows the procedure which determines use of an auxiliary power supply in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 4 Motor 6 Control circuit 7 Vehicle speed sensor 8 Torque sensor 9 Main power supply 10 Auxiliary power supply 13 Charging / discharging circuit 20 Steering speed sensor

Claims (3)

An electric power steering device that generates a steering assist force by a motor,
A main power supply for supplying power to the motor;
An auxiliary power source capable of supplying power to the motor;
Steering speed detecting means for detecting the steering speed of the steering wheel of the electric power steering device;
A first output state for charging the auxiliary power source based on the main power source and supplying power to the motor only by the main power source; and a second output state for supplying power to the motor from the main power source and auxiliary power source A charge / discharge circuit that selectively configures the output state of
When the absolute value of the steering speed detected by the steering speed detection means is less than or equal to a predetermined value, the charge / discharge circuit is set to the first output state, and when the absolute value exceeds the predetermined value, the charge / discharge circuit is set to the second output state. An electric power steering apparatus comprising: a control circuit for setting an output state. An electric power steering device that generates a steering assist force by a motor,
A main power supply for supplying power to the motor;
An auxiliary power source capable of supplying power to the motor;
A first output state for charging the auxiliary power source based on the main power source and supplying power to the motor only by the main power source; and a second output state for supplying power to the motor from the main power source and auxiliary power source A charge / discharge circuit that selectively configures the output state of
When the differential value of the steering torque detected by the torque sensor for detecting the steering torque of the steering wheel of the electric power steering device is less than or equal to a predetermined value, the charge / discharge circuit is set to the first output state and exceeds the predetermined value An electric power steering apparatus comprising: a control circuit for setting the charge / discharge circuit to the second output state.   The control circuit sets the charge / discharge circuit to the second output state when the vehicle speed is equal to or lower than a predetermined value, and sets the charge / discharge circuit to the first output state when the vehicle speed exceeds the predetermined value. 3. The electric power steering device according to any one of 2 above.

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