JPH07329798A - Electric power steering device - Google Patents

Abstract

PURPOSE:To improve the reliability of the motion of a motor by providing with a plurality of relay contacts connected in parallel for supplying a motor current; a plurality of relay driving circuits for driving the contacts in every relay; and a means for distinguishing whether voltage at the terminal on a motor side of the contact is more than a fixed value or not. CONSTITUTION:When voltage at a terminal on a motor side is distinguished to be less than a fixed voltage, a relay RY1 monitoring finish plug is set, and then a fail safe plug is set for returning. When the disengagement of a clutch and relay RY1 monitoring finish are distinguished, whether a relay RY2 monitoring ends or not is distinguished, and when the monitoring is distinguished not to finish by clearing, only the terminal of the relay RY2 is turned ON, and whether voltage at the terminal on the side of a main circuit 6 of a contact of the relay RY2 is more than fixed voltage or not is distinguished. When the above voltage is distinguished to be more than the fixed voltage, a relay RY2 monitoring finish plug is set, and then the contacts of the relays RY1, RY2 are turned ON together.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device in which a steering force of steered wheels is assisted by a motor.

[0002]

2. Description of the Related Art A state in which a vehicle such as an automobile is stopped,
Alternatively, when the vehicle is traveling at a low speed, a large steering force is required to operate the steered wheels. Therefore, in order to reduce the steering force of the driver, an electric power steering device in which a motor assists the steering force has been put into practical use. Such an electric power steering device is configured, for example, as shown in FIG. The motor 1 for assisting the steering force is connected between the motor connection terminal 2a and the motor connection terminal 2b of the controller 2.

The positive electrode + of the battery 3 which is the driving power source of the motor 1 is connected to the power supply connection terminal 2c of the controller 2 via the contact 4a of the fail-safe relay 4, and the negative electrode − is connected to the power supply connection terminal 2d of the controller 2. There is. The relay coil 4c of the fail-safe relay 4 is connected between the relay connection terminal 2e of the controller 2 and the relay connection terminal 2f, and the relay 4 is provided outside the controller 2.

The controller 2 includes a relay drive circuit 5 and
The motor drive circuit 6 is built in, and the relay drive circuit 5 is connected to the relay connection terminals 2e and 2f. The input side of the motor drive circuit 6 is connected to the power supply connection terminals 2c and 2d, and the output side is connected to the motor connection terminals 2a and 2b. A key switch 7 is connected between the key switch connection terminal 2g of the controller 2 and the positive electrode + of the battery 3.

Next, the operation of this electric power steering system will be described. Now, when the key switch 7 is turned on,
Current is supplied to the relay coil 4c of the fail-safe relay 4, and the contact 4a is turned on. Thereby battery 3
To the motor 1 via the contact 4a and the motor drive circuit 6,
A drive current corresponding to the detected torque of a torque sensor (not shown) that detects the steering force is supplied, and the motor 1 generates the drive force in a predetermined rotation direction to assist the driver's steering force.
When the key switch 7 is turned off, the current to the relay coil 4c is cut off, the contact 4a is turned off, the drive current of the motor 1 is cut off, and the steering force is not assisted.

Thus, the drive current of the motor 1 is, for example,
In the case of a large current of 70 A or more, it is necessary to use the contact 4a having a large current capacity, and the fail-safe relay 4 becomes large in size and cannot be built in the controller 2.
As shown in, the fail-safe relay 4 is connected to the controller 2
It is provided outside of.

[0007]

As described above, when the driving current of the motor is a large current of, for example, 70 A or more, the fail-safe relay having a contact capable of flowing the large current is expensive, and Since the fail-safe relay has a large shape, it needs to be provided outside the controller, and a bracket for mounting the fail-safe relay and a connector for electrically connecting the fail-safe relay and the controller are required. To do. Therefore, there is a problem that the electric power steering device becomes expensive. Further, there is a possibility that contact failure may occur due to the interposition of the connector, and there is a problem that reliability is reduced.

In view of the above problems, the present invention provides an electric power steering apparatus which is small in size and inexpensive in construction, and has high reliability in motor operation, even if the drive current of the motor for assisting the steering force is large. With the goal.

[0009]

An electric power steering apparatus according to a first aspect of the present invention is an electric power steering apparatus configured to assist a steering force of steered wheels by a motor. The electric power steering apparatus is connected in parallel to flow a current of the motor. A plurality of relay contacts, a plurality of relay drive circuits that drive the contacts for each relay, and means for determining whether or not the voltage of the motor-side terminal of the contacts is equal to or higher than a predetermined value. It is characterized by

An electric power steering apparatus according to a second aspect of the present invention is characterized in that the plurality of relays are built in a control section for driving and controlling the motor.

In the electric power steering apparatus according to the third aspect of the invention, means for detecting the current of the motor, comparing means for comparing the current value detected by the means with a predetermined value, and the comparing means And a means for closing one of the contacts and opening the other when it is determined to be equal to or less than a predetermined value.

According to a fourth aspect of the present invention, in the electric power steering apparatus, when the current of the motor becomes equal to or less than the predetermined value after the comparing means determines that the current of the motor is larger than the predetermined value, the contact point is reduced. One of them is closed and the other is opened to determine whether or not the voltage of the terminal of the contact on the motor side is equal to or higher than a predetermined value.

An electric power steering apparatus according to a fifth aspect of the present invention comprises a clutch for transmitting the rotational force of the motor to a steering mechanism and a means for determining whether the clutch is engaged or disengaged, and it is determined that the means is in a disengaged state. In this case, one of the contacts is closed and the other is opened to determine whether the voltage of the motor-side terminal of the contact is equal to or higher than a predetermined value.

[0014]

In the first aspect of the invention, each relay drive circuit
When the contacts of each of the multiple relays connected in parallel are turned on,
The motor current shunts and flows to each contact. As a result, it is possible to supply a current to the motor by using a plurality of small and inexpensive relays having contacts with a small current capacity. When it is determined whether the voltage of the motor-side terminal of each contact is equal to or higher than a predetermined value, it can be determined whether the contact is normal or abnormal. If one contact fails, the motor current will flow through the remaining contacts. Therefore, a small and inexpensive relay can be used, and the reliability of motor operation can be improved.

According to the second aspect of the invention, a plurality of relays having respective contacts connected in parallel for flowing the current of the motor are built in the control unit for driving and controlling the motor. When each contact is turned on by each relay drive circuit, the motor current is divided and flows to each contact. When it is determined whether the voltage of the motor-side terminal of each contact is equal to or higher than a predetermined value, it can be determined whether the contact is normal or abnormal. If one contact fails, the motor current will flow through the remaining contacts. As a result, the current can be supplied to the motor by using a plurality of small, inexpensive relays having contacts with a small current capacity, and the size and cost can be reduced. Moreover, the reliability of the operation of the motor can be improved.

In the third aspect of the invention, when the current value of the motor is less than or equal to a predetermined value, one of the contacts of the plurality of relays is closed and the other is opened. As a result, if the motor current is less than the specified value, the relay will not be overloaded even if the motor current is passed through one contact. By monitoring the voltage of, the failure of the contact can be determined.

In the fourth invention, the drive current of the motor is shunted to the contacts of the plurality of relays connected in parallel and flows. When it is determined that the motor current is greater than the predetermined value and then the motor current is less than or equal to the predetermined value, it is determined whether the voltage at the motor-side terminal of the contact is greater than or equal to the predetermined value. As a result, the quality of the contact can be determined with a low frequency.

According to the fifth aspect of the invention, when it is determined that the clutch for transmitting the rotational force of the motor to the steering mechanism is in the disengaged state, it is determined whether the voltage at the motor side terminal of the contact is equal to or higher than a predetermined value. When the clutch is in the disengaged state, no current is flowing to the motor, so closing one contact and opening the other does not affect the system. By monitoring the voltage, the failure of the contact can be determined.

[0019]

The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. FIG. 1 is a schematic diagram of an electric power steering device according to the present invention. Motor 1 that assists the steering force of the steered wheels
Is the motor connection terminal 2a and the motor connection terminal of the controller 2
It is connected between 2b. The positive electrode + of the battery 3, which is the drive power source of the motor 1, is the power source connection terminal of the controller 2.
2c and the negative electrode are connected to the power supply connection terminal 2d of the controller 2. The controller 2 has a fail-safe relay (hereinafter called relay) RY ₁ and a fail-safe relay.
(Hereinafter referred to as relay) RY _2, the relay drive circuit 5A, the relay driving circuit 5B and has a motor driving circuit 6 is incorporated, and the contact RY _1a of the relay RY _1, and the contact RY _2a of the relay RY ₂ is connected in parallel ing. One side of the connection between the contacts RY _1a and RY _2a is connected to the power supply connection terminal 2c. The other side of the connection between the contacts RY _1a and RY _2a and the power supply connection terminal 2d are connected to the input side of the motor drive circuit 6, and the output side thereof is the motor connection terminals 2a, 2b.
Connected with.

The relay driving circuit 5A is connected to the relay coil RY _1c of the relay RY _1, the relay driving circuit 5B is connected to the relay coil RY _2c of the relay RY _2. A key switch 7 is connected between the key switch connection terminal 2g of the controller 2 and the positive electrode + of the battery 3. Contact RY _1a , RY _2a
Have the same current capacity, and are selected to have a current capacity of, for example, approximately half the maximum drive current of the motor 1.

Next, the operation of the electric power steering device constructed as described above will be described. When the key switch 7 is turned on, the relay drive circuits 5A and 5B are driven, and the relay drive circuits 5A and 5B cause the relay coils RY _1c and RY _{1c of} the relays RY ₁ and RY ₂ to move.
Current is supplied to RY _2c and contacts RY _1a and RY _2a both turn on. As a result, the current from the battery 3 is applied to the contacts RY _1a , RY
_{The current} is divided by _2a and flows to the motor drive circuit 6, and the motor 1 is supplied with a drive current according to the detection torque of a torque sensor (not shown) that detects a steering force, and the motor 1 rotates a predetermined speed. Driven in the direction to assist the steering force of the driver. When the key switch 7 is turned off again,
The current to the relay coils RY _1c and RY _2c is cut off, and the contact RY
_1a and RY _2a are turned off, the drive current of the motor 1 is cut off, and the steering force is no longer assisted.

Since the drive current flowing from the battery 3 to the motor 1 is divided into the contacts RY _1a and RY _2a in this manner, the small fail-safe relays RY ₁ and RY ₂ having the contacts RY _1a and RY _2a having a small current capacity are provided. Can be used. That is, when the maximum current of the motor 1 was 70A, the contact RY _1a current capacity is 35A, the RY _2a can be used. for that reason,
In a system in which the maximum current of the motor 1 is 35A, the two relays used in the controller 2 can be incorporated in the controller 2. In this case, the controller 2 is slightly increased in size due to the increase in the number of relays. However, as in the case where the relay is attached to the outside of the controller 2, a bracket for the relay and a connector for electrically connecting the controller and the relay are provided. Is unnecessary, and the size and cost of the electric power steering device can be reduced. If one of the contacts RY _1a , RY _2a fails, the drive current flows to the motor through the other contact, so the motor does not immediately become inoperable due to the failure of the contact. The reliability can be increased.

By the way, the drive current of the motor 1 is changed to the contact RY.
_In the case of shunting to _1a and RY _2a , if one contact fails, the drive current concentrates on the other contact and if the current capacity exceeds the current capacity, the contacts will burn out and the operation of the electric power steering system will not work properly. It is possible that Therefore, the state of each contact is monitored as follows.

2 and 3 are half of a block diagram showing a specific configuration of the controller 2, and the same components as those in FIG. 1 are designated by the same reference numerals. The vehicle speed signal S _SP , the torque signal main S _TM , the torque signal sub S _TS, and the voltage of the battery 3 are input to the controller 2, and current is supplied from the controller 2 to the motor 1 and the clutch CLH.

The vehicle speed signal S _SP is input to the input port DI ₀ of the CPU 30 via the vehicle speed signal input circuit 21a. The torque signal main S _TM is sent to the CPU 30 via the torque main input circuit 21b.
Input to the input port AI _{0 of} the torque main input circuit 21
Input from b to the input port AI ₁ of the CPU 30 via the torque main amplifier circuit 21c. Torque signal sub S _TS is input to the input port AI ₂ of CPU 30 via the Torukusabu input circuit 21d. Voltage of the battery 3 is supplied to the relay RY _1, RY serving motor driving circuit via the parallel circuit of contacts (not shown) of the ₂ main circuit 6 and the relay terminal voltage monitoring circuit 21l. The detected current obtained by detecting the current flowing through the motor 1 is input to the motor current detection circuit 21m.

Further, the voltage of the battery 3 is directly applied to the system power supply control circuit 21e, is also applied via the key switch 7, and is also applied to the key switch monitoring circuit 21g. System power control circuit 21e has CPU 30 output port
The DO ₀ signal is input. The control signal output from the system power supply control circuit 21e is the 5V power supply circuit / WDT circuit 21f, 8
Input to V power supply circuit 21h and 26V power supply circuit 21i. 5V
The output signal of the power supply circuit / WDT circuit 21f is input to the reset terminal RES of the CPU 30. 5V power supply circuit / WDT circuit 21f
The signal from the output port DO ₁ of the CPU 30 is input and a voltage of 5V is applied. The output signal of the key switch monitoring circuit 21g is input to the input port DI ₁ of the CPU 30.

A voltage of 8V is applied to the 8V power supply circuit 21h and the 8V power supply monitoring circuit 21j. The output signal of the 8V power supply monitor circuit 21j is input to the input port AI ₃ of the CPU 30. The 26V voltage is supplied to the 26V power supply circuit 21i and the 26V power supply monitoring circuit 21k. The output signal of the 26V power supply monitoring circuit 21k is input to the input port AI ₄ of the CPU 30. The signal from the output port DO ₂ of the CPU 30 is input to the relay drive circuit 5A, and its output signal is given to the relay RY ₁ as a drive signal. The signal from the output port DO ₃ is input to the relay drive circuit 5B, and its output signal is given to the relay RY ₂ as a drive signal. The output signal of the relay terminal voltage monitoring circuit 21l is input to the input port AI ₅ of the CPU 30, and the output signal of the motor current detection circuit 21m is input to the input port AI ₆ of the CPU 30.

The signal at the output port DO ₄ of the CPU 30 is 26V
Is input to the main circuit drive circuit 21o to which the voltage is applied, and its output signal is applied to the main circuit 6. The signal from the output port DO ₅ of the CPU 30 is input to the clutch drive circuit 21p, and its output signal is input to the clutch CLH and the clutch voltage monitoring circuit 21r. The signal from the clutch drive circuit 21p is given to the clutch current monitoring circuit 21q, and its output signal is
Input to input port DI _{2 of} CPU 30. The output signal of the clutch voltage monitoring circuit 21r is input to the input port DI ₃ of the CPU 30. The rotational force of the motor 1 is transmitted to the speed reducer SDN via the clutch CLH.

Next, by the controller 2, the relay RY
₁RY₂The operation of monitoring the contact of the
Together with the flow charts of FIGS. 4 and 5 showing the halves respectively
explain. Now, when the key switch 7 is turned on, the control
The voltage is applied to each circuit of the roller 2 and the CPU 30 operates.
Can be started to drive the motor 1 which assists the steering force.
It becomes a state. First, the CPU 30 causes the relay RY to be described later.₁Superintendent
Visual end flag and relay RY ₂Check the monitoring end flag and
It is determined whether the initial monitoring of the array has been completed (S1)
If not, then relay RY₁Finished monitoring
If it is determined that it has not ended (S2),
Output port DO₂Output signal from relay RY ₁Turned on
Output port DO₃Does not output a signal from the relay RY₂
Is turned off (S3).

[0030] Subsequently examined input port AI ₅ by CPU 30, the contacts of the terminal voltage of the relay RY _1, i.e. the voltage of the main circuit 6 side terminals of the contact of the relay RY ₁ (not shown) is a predetermined voltage or higher It is determined whether or not (S4). If it is determined that there is no voltage drop due to a contact failure of the relay RY ₁ and that contact is normal and is equal to or higher than a predetermined voltage, the relay RY ₁ monitoring end flag is set (S5) and the process returns. Also,
If there is a voltage drop due to contact failure and the contact is abnormal, and it is determined that the voltage at the terminal on the main circuit 6 side is less than the predetermined voltage (S4), the relay RY ₁ monitoring end flag is set ( S6), sets the fail-safe flag (S7), and returns.

When the CPU 30 again determines that the relay initial monitoring is not completed (S1), the relay RY ₁
It is determined whether or not the monitoring of ( ₁ ) has been completed (S2), and the relay RY ₁ monitoring completion flag has already been set.
_When it is determined that the monitoring of ₁ is finished, it is determined whether the monitoring of the relay RY ₂ is finished (S8), and when it is determined that the monitoring of the relay RY ₂ is not finished, no signal is output from the output port DO ₂ and the relay RY ₁
Is turned off and the signal is output from the output port DO ₃ and relayed.
Turn RY ₂ on (S9). Subsequently, examine the input port AI ₅ by CPU 30, or the contacts of the voltage at the terminals of the relay RY _2, i.e. the voltage of the main circuit 6 side terminals of the contact of the relay RY ₂ (not shown) is a predetermined voltage or more It is determined whether or not (S10).

Here, the relay RY₂Due to poor contact
Voltage drop, the contact is normal, and
If it is determined to be above, relay RY₂The monitoring end flag of
Set (S11). Then CPU 30 outputs DO₂， DO
₃Output signals from each and relay RY₁RY₂Drive
Turn on each contact (S12). Next, the relay initial supervision
It is determined whether or not the viewing end flag is set (S13)
 , If it is determined that it is not set, the relay initial monitoring
The end flag is set (S14). Also, relay RY ₂Contact
There is a voltage drop due to poor contact at a point, and the contact is abnormal.
Therefore, the voltage of the terminal on the main circuit 6 side is less than the predetermined voltage.
If it is determined (S10), the relay RY₂Set the monitoring end flag
(S15), and then set the failsafe flag.
(S16). Then, the relay initial monitoring end flag is set.
If not determined (S13), the relay initial monitoring ends.
Set the flag (S14) and return.

As a result, the initial monitoring of the contacts of the relays RY ₁ and RY ₂ is completed. In this way, when the contacts of relays RY ₁ and RY ₂ are normal and the contacts of relays RY ₁ and RY ₂ are turned on (S12), the current from battery 3 is shunted to both contacts of relays RY ₁ and RY _2. Is supplied to the main circuit 6. Also, CPU 30
By checking the input port AI ₀ with, output a signal corresponding to the torque signal main S _TM from the output port DO ₄ , drive the main circuit drive circuit 21o, and apply the drive signal which is the output signal to the main circuit 6. , Drive the main circuit 6.

When the main circuit 6 is driven, a drive current corresponding to the torque signal main S _TM is supplied to the motor 1 to drive the motor 1. From here, the relays RY ₁ and RY ₂ after the initial monitoring of the relays are monitored. CPU 30
If the engine is stopped or the input port
When DI ₀ is checked and the vehicle speed signal S _SP of a predetermined value or more is input, the signal for driving the clutch CLH is not output from the output port DO _5, and the clutch CLH is disengaged. The CPU 30 checks the relay initial monitoring end flag, and if the flag is set and it is determined that the relay initial monitoring has ended (S
1) Then, check the output port DO ₅ , and determine whether the clutch CLH is off, that is, whether it is disengaged (S17) .If it is disengaged, check the relay RY ₁ monitoring end flag, If it is determined whether the monitoring of the relay RY ₁ has ended (S2), and if it is determined that the monitoring has ended, then the relay RY ₂ monitoring end flag is checked to determine whether the relay RY ₂ monitoring has ended (S
8), if it is determined that the monitoring has ended, the process returns. That is, immediately after the end of the initial monitoring, the relay R regardless of the state of the clutch CLH.
Y _1, not to determine the quality of the contacts of RY _2.

Next, when the engine is driven,
Input port DI₀Check the vehicle speed signal S below a predetermined value_SP
Is input, the output port DO_Five
Outputs the signal to drive the clutch CLH from the clutch CL
Engage H. In addition, the CPU 30 enables the initial monitoring of the relay.
If it is determined that the output has been completed (S1), then the output port DO _Five
To determine whether the clutch CLH is off (S
17) If it is determined that it is on, the CPU 30 will
AI₆The current of the motor 1 is below a predetermined value, that is,
Relay RY₁RY₂The current capacity of the contact of
If it is determined that the value is less than the predetermined value (S18), the relay RY
₁Check the monitoring end flag and relay RY₁Whether or not the monitoring of
Discriminate (S2), relay RY upon completion of initial monitoring₁End monitoring
If it is determined that the relay RY₂Whether or not the monitoring of
Determine (S8), relay RY₂Check the monitoring end flag and end monitoring
If it is determined that, it returns.

As a result, when the drive current of the motor 1 is less than the predetermined value after the initial monitoring, that is, the relay R
If the current capacity of the contacts of Y ₁ and RY ₂ is less than the current capacity, relays RY and R
Neither the quality of the Y ₂ contact is determined. When the clutch CLH is engaged in this way, the clutch CLH
The rotational force of the motor 1 is transmitted to the speed reducer SDN via H, and a steering shaft (not shown) rotates to assist the steering force. The CPU 30 examines the input port AI _0, and outputs a signal corresponding to the torque signal main S _TM from the output port DO _4, will control the rotational force of the motor 1 in response to the torque signal main S _TM .

When the CPU 30 determines that the clutch CLH is on (S17), the input port AI ₆ is checked to determine whether the drive current of the motor 1 is below a predetermined value (S17).
18) If it is determined that the value is larger than the predetermined value, the relay RY ₁ monitoring end flag is cleared (S19), then the relay RY ₂ monitoring end flag is cleared (S20), and the process returns. continue,
The CPU 30 checks the relay initial monitoring end flag, and if the relay initial monitoring end flag is set and it is determined that the relay initial monitoring is finished (S1), it is determined whether or not the clutch CLH is disengaged (S17), When decoupled to determine which examine the relay RY ₁ monitoring end flag, it is determined whether or not the relay RY ₁ monitoring end or (S2), the relay RY ₁ by clearing the above-described
If it is determined that the monitoring of has not been completed, only the contact of the relay RY ₁ is turned on (S3), and it is determined whether the voltage of the terminal on the main circuit 6 side of the contact of the relay RY ₁ is equal to or higher than a predetermined voltage (S4). ), If it is determined that the voltage is equal to or higher than the predetermined voltage, the relay RY ₁ monitoring end flag is set (S5), and the process returns.

When it is determined that the voltage is less than the predetermined voltage, the relay RY
₁ Set the monitoring end flag (S6), set the fail-safe flag (S7), and return. If it is determined that the clutch CLH is disengaged and it is determined that the relay RY ₁ monitoring is completed, then it is determined whether or not the relay RY ₂ monitoring is completed (S8), and if it is determined that it is not completed by the above-described clearing. Only the contact of relay RY ₂ is turned on (S9), and relay RY ₂
It is determined whether or not the voltage at the main circuit 6 side terminal of the contact is above a predetermined voltage (S10). If it is above the predetermined voltage, the relay RY ₂
Set the monitoring end flag (S11), then relay RY ₁ ,
Turn on both RY ₂ contacts (S12). Then, it is determined whether or not the relay initial monitoring flag is set, and when it is determined that the initial monitoring is completed and the relay initial monitoring end flag is set (S13), the process returns.

In this way, when it is determined that the drive current of the motor 1 is larger than the predetermined value (S18), the relay RY ₁
Monitor flag and relay RY ₂ Clear the monitor flag (S1
9) (S20), relay RY ₁ , RY ₂ contact relay RY ₁ , RY ₂
The quality is determined in the same manner as in the case of the initial monitoring of.

Further, as described above, it is determined whether or not the motor current is less than or equal to a predetermined value (S18), and if it is determined to be greater than the predetermined value, the relay RY ₁ monitoring end flag and relay
RY ₂ Clear the monitoring end flag (S19) (S20). continue,
If the motor current is determined to be equal to or less than the predetermined value, the contact of the relay RY _1, RY _2, as in the case where it is determined that the disconnect clutch CLH, the quality of contact of the relay RY _1, RY ₂ Determine.

[0041] Incidentally, the step (S4), in (S10), determines the voltage of the contacts of the terminals of the relay RY _1, RY ₂ is whether or not a predetermined voltage or more is actually defines a predetermined time, in that time The discrimination operation is continued with. In this way, when the contacts of the relays through which the drive current of the motor 1 flows are initially monitored, and after the initial monitoring is finished, when it is determined that the motor current exceeds a predetermined value, the contacts of the respective relays are contacted. The quality of will be determined.

By doing so, it is possible to provide a small and inexpensive electric power steering apparatus by using a plurality of inexpensive relays having a small current capacity of the contacts. Further, since a small relay is used, it can be built in a control unit for controlling the motor, and a bracket for the relay and a connector for connecting the control unit and the relay are not required, and the cost can be reduced.
Further, since the motor current is shunted to the contacts of a plurality of relays, even if one of the contacts fails, the current of the motor is not immediately cut off, and the reliability of the operation of the motor that assists the steering force is improved. be able to.

Furthermore, after the initial monitoring, if the motor current does not exceed a predetermined value, the quality of the relay contacts is not judged. Therefore, the frequency of relay ON / OFF is reduced to prevent noise generation and durability of the relay. Will be excellent in terms of. In this embodiment, the drive current of the motor 1 is divided into two relays.
RY _1, was diverted to the respective contacts of RY _2, the number of these relays are not limited to two, the same effect can be diverted in the same manner using three or more relays resulting .

[0044]

As described above in detail, in the first invention, a plurality of small and inexpensive relays having contacts with small current capacity are used, and those contacts are connected in parallel so that the motor current for assisting the steering force is increased. Since the flow is divided, it is possible to provide an electric power steering device that is inexpensive and has a highly reliable motor operation.

In the second invention, a plurality of inexpensive relays having contacts with small current capacity are used, and these contacts are connected in parallel so as to shunt the current of the motor for assisting the steering force. Since it is built in the control unit that controls the drive, the reliability of the motor operation can be improved and
A bracket for mounting the relay and a connector for connecting the relay and the control unit are not required, so that the cost can be reduced and the electric power steering device with high reliability can be provided at low cost.

In the third invention, when the current value of the motor is less than or equal to the predetermined value, one of the contacts of the plurality of relays is closed and the other contact is opened. In the following cases, the current of the motor flows through one contact, and it is not necessary to apply an excessive load to that contact.In that condition, monitor the terminal voltage on the motor side of the contact,
The failure of the contact can be identified.

In the fourth invention, a plurality of inexpensive relays having contacts with small current capacity are used, and these contacts are connected in parallel to divide the current of the motor for assisting the steering force. Moreover, the reliability of the motor operation can be improved. Furthermore, when the motor current becomes less than the specified value after it is determined that the motor current is greater than the specified value, the relay contacts are monitored. Therefore, it is possible to provide an electric power steering device that can reduce the amount of noise, has less noise from the relay, and has excellent durability of the relay.

In the fifth aspect of the invention, when it is determined that the clutch for transmitting the rotational force of the motor to the steering mechanism is in the disengaged state, it is determined whether or not the voltage at the motor side terminal of the contact is equal to or higher than a predetermined value. When the clutch is in the disengaged state, no current is flowing to the motor.Therefore, closing one contact and opening the other has no effect on the system.In that state, the voltage at the motor side terminal of the contact is By monitoring, the failure of the contact can be identified.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a controller of an electric power steering apparatus according to the present invention.

FIG. 2 is a half part of a block diagram showing a specific configuration of a controller of the electric power steering apparatus according to the present invention.

FIG. 3 is a half part of a block diagram showing a specific configuration of a controller of the electric power steering apparatus according to the present invention.

FIG. 4 is a half part of a flowchart showing the control contents of the CPU.

FIG. 5 is a half part of a flowchart showing the control contents of the CPU.

FIG. 6 is a schematic diagram of a controller of a conventional electric power steering device.

[Explanation of symbols]

1 Motor 2 Controller 3 Battery 7 Key switch 30 CPU RY ₁ , RY ₂ Fail-safe relay

Claims (5)

[Claims] 1. An electric power steering device configured to assist a steering force of steered wheels by a motor,
Contact points of a plurality of relays connected in parallel to flow the motor current, a plurality of relay drive circuits that drive the contact points for each relay, and whether or not the voltage at the motor side terminal of the contact points is equal to or greater than a predetermined value. An electric power steering device comprising: 2. The electric power steering device according to claim 1, wherein the plurality of relays are built in a control unit that drives and controls the motor. 3. A means for detecting a current of the motor, a comparing means for comparing a current value detected by the means with a predetermined value, and a case in which the comparing means determines that the current value is a predetermined value or less, The electric power steering apparatus according to claim 1, further comprising: a means that closes one of the contacts and opens the other. 4. When one of the contacts is closed when the current of the motor becomes equal to or less than the predetermined value after the comparing means determines that the current of the motor is larger than the predetermined value. 4. The electric power steering apparatus according to claim 3, wherein the other is opened to determine whether or not the voltage of the motor-side terminal of the contact is equal to or higher than a predetermined value. 5. A clutch for transmitting the rotational force of the motor to a steering mechanism, and means for determining whether the clutch is engaged or disengaged. When it is determined that the means is in a disengaged state, among the contact points, 4. The electric power steering apparatus according to claim 3, wherein one of the contacts is closed and the other is opened to determine whether or not the voltage of the motor-side terminal of the contact is equal to or higher than a predetermined value.