JP2003220963A - Electric power steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering control device for preventing overheat of a motor without generating a sudden change to steering force required for a driver. <P>SOLUTION: The electric power steering control device is equipped with a torque sensor 1 detecting steering torque, a motor 2, a memory part 3 which memorizes control data D1 for determining the size of the driving power of the motor 2 corresponding to change in the steering wheel torque, and a control means 4 which monitors heat generation of the motor 2 and determines the driving power of the motor 2 according to the control data D1. It is constituted so that the control data D2, D3 are stored in the memory part 3, for making small the value of the driving power of the motor 2 to the same steering torque as compared with the control data D1, and the control means 4 determines the driving power of the motor 2 utilizing the control data D2, D3 instead of the control data D1 when the motor 2 is judged to be in a certain heated state. <P>COPYRIGHT: (C)2003,JPO

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 control device used by being incorporated in a vehicle such as an automobile.

[0002]

2. Description of the Related Art An example of a schematic structure of a conventional electric power steering control device is shown in FIG. The illustrated electric power steering control device includes a torque sensor 1, a motor 2, a storage unit 30, and a control unit 40.

The torque sensor 1 detects the steering torque of the steering mechanism of the vehicle. The motor 2 applies a steering assist force to the steering mechanism section. In the steering mechanism section, when the steering wheel 5 is operated by the driver, the steering shaft 6 rotates, and this rotation is converted into an operation in the vehicle width direction by the steering gear 7, so that the directions of the pair of wheels 8 are changed. It is configured to be. Motor 2
Is assisted in the rotation of the steering shaft 6, and the driver's steering operation load is reduced.

The storage unit 30 stores control data for determining the current flowing through the motor 2. Control unit 40
Is based on the steering torque and the control data,
The current flowing through the motor 2 is determined. As shown by the solid line L10 in FIG. 6, the control data is specified in principle such that the current increases as the steering torque increases. This is because the current, that is, the steering assist force is increased substantially in proportion to the steering torque to appropriately reduce the driver's steering operation load.

However, when a large current flows through the motor 2, the temperature of the motor 2 rises. This causes the motor 2 to overheat and fail. for that reason,
Even when the steering torque becomes larger than a predetermined value T1, a current not exceeding a predetermined upper limit value i does not flow in the motor 2.

[0006]

However, the above-mentioned conventional device has the following problems.

That is, conventionally, when the steering torque reaches the value T1, the steering assist force of the motor 2 does not increase and remains constant even if the steering torque further increases thereafter. On the other hand, the steering torque generally increases as the steering angle increases. Therefore, as shown in FIG. 7, when the steering angle gradually increases due to the steering operation, when the steering angle reaches the predetermined angle α and the steering torque becomes equal to or more than the value T1, the time This caused a phenomenon in which the steering force required by the driver suddenly increased. Such a sudden change in steering force is not preferable in terms of vehicle operability. Also, the motor 2
Although the current exceeding the upper limit value i is prevented from flowing to the motor 2, if the current near the upper limit value i continues to flow to the motor 2,
Since the heat generation temperature of the motor 2 rises over time, the motor 2 may be overheated.

The present invention has been devised under such circumstances, and it is possible to prevent overheating of a motor without causing a sudden change in the steering force required by the driver. It is an object of the present invention to provide an electric power steering control device capable of performing the above.

[0009]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention takes the following technical means.

The electric power steering control device provided by the present invention includes a torque sensor for detecting a steering torque, a motor for applying a steering assist force to the steering mechanism portion, and the above-mentioned corresponding to the change of the steering torque. A storage unit that stores first control data for determining the magnitude of the driving power of the motor, and monitors the heat generation of the motor, and based on the steering torque and the first control data, the motor Control means for determining the driving power of
An electric power steering control device including: a second power reduction control unit configured to reduce the value of the drive power of the motor with respect to the same steering torque as compared with the first control data in the storage unit. Control data is stored,
Further, when the control means determines that the motor is in a constant heat generation state, the motor is driven by using the second control data instead of the first control data. It is characterized in that it is configured to determine power.

According to this structure, when the motor is in a constant heat generation state, the drive power of the motor is determined based on the second control data instead of the first control data. Will be done. Then, the value of the drive power of the motor becomes small, and the steering assist force of the motor also becomes small. Therefore, when an upper limit is set to the drive power supplied to the motor for the purpose of preventing the motor from overheating, the motor can provide a steering assist force commensurate with the steering torque of the steering mechanism. It is possible to prevent a sudden change in the steering force required by the driver when the state is switched to a state in which only a constant steering assist force is obtained. That is, in the past, in the process of performing the steering operation to increase the steering angle, there was a phenomenon in which a large amount of steering assist force was rapidly obtained from a state where a large steering assist force was obtained. On the other hand, in the present invention, by reducing the steering assist force in advance, the degree of change in the steering assist force at the time when only a certain steering assist force is obtained is reduced so that the driver does not feel uncomfortable. can do. As a result, the operability of the vehicle is improved. Further, according to the present invention, when the motor is in a constant heat generation state, the value of the drive power of the motor can be reduced to improve the heat generation state of the motor. It is more suitable to

In a preferred embodiment of the present invention, the storage section stores a plurality of pieces of data as the second control data, and the control means responds to the heat generation state of the motor. It is configured to selectively use the plurality of second control data.

According to this structure, the drive control of the motor can be performed more finely than in the case where only one second control data is provided, and the steering force required by the driver can be reduced. It is possible to more appropriately prevent sudden changes and overheating of the motor.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows an embodiment of a schematic structure of an electric power steering control device according to the present invention. It should be noted that, in the drawings shown in FIG. 1 and subsequent figures, the same or similar elements as those of the above-described conventional technique are denoted by the same reference numerals as those of the above-described conventional technique. The electric power steering control device of the present embodiment has a storage unit 3 and a control unit 4 which are different in configuration from the storage unit 30 and the control unit 40 of the above-mentioned conventional technology. The configuration other than that is the same as that of the above-mentioned conventional technique. Therefore, in the electric power steering control device of the present embodiment, the torque sensor 1 and the motor 2 are provided in the steering mechanism portion of the vehicle having the configuration shown in FIG.
It is configured as assembled.

The storage unit 3 has a first control data D1 for determining a current flowing through the motor 2 (hereinafter referred to as "motor current") and two types of second control data D2.
It remembers D3 and. These control data D1 to D
As shown in FIG. 2, reference numeral 3 is data defining the relationship between the steering torque and the motor current. In each case, the motor current is set to increase as the steering torque increases, and the motor current is set to a constant value i. Is not exceeded. The first control data D1 has a larger motor current value with respect to the same steering torque than the second control data D2 and D3, and is the data that reduces the driver's steering operation load most. . Therefore, in the normal time, the first control data D1 is stored in the motor 2.
A current determined based on As will be described later, the second control data D2 and D3 are data used when the heat generation temperature of the motor 2 exceeds a predetermined value, and the second control data D2 is greater than the second control data D2. The data D3 has a smaller motor current value for the same steering torque.

As shown in FIG. 3, the control unit 4
Includes a heat generation temperature calculation means 41, a temperature region determination means 42, a control data selection means 43, and a current determination means 44. The heat generation temperature calculation means 41 calculates the heat generation temperature of the motor 2 based on the value of the motor current and its time. In the temperature region determination means 42, the first to third temperature regions J1 to J3 in which the heat generation temperature is preset are set.
Which of the above is applicable is determined. These first to third temperature regions J1 to J3 are all temperature regions lower than the temperature at which the motor 2 is in an overheated state, and the first temperature region J1 is in the lowest temperature range. The second temperature range J2 is a higher temperature range than the first temperature range J1, and the third temperature range J3 is a higher temperature range than those.

The control data selection means 43 selects one control data from the first and second control data D1 to D3 stored in the storage section 3 based on the judgment result of the temperature region judgment means 42. You have selected. For the first temperature region J1 which is the lowest temperature, the first control data D
1 is selected. The second control data D2 is selected for the second temperature region J2, and the third control data D2 having the highest temperature is selected.
The second control data D3 is selected for the temperature region J3. The current determination means 44 determines the motor current based on one of the steering torque detected by the torque sensor 1 and the first and second control data D1 to D3 selected by the control data selection means 43. I have decided.

First, when the heat generation temperature of the motor 2 is within the range of the first temperature range J1, the motor current is determined based on the steering torque and the first control data D1. In this case, for example, if the steering operation is frequently performed, the temperature of the motor 2 rises and the temperature shifts to the second temperature region J2. Then, the control data selecting means 4
3 selects the second control data D2 instead of the first control data D1. The current determining means 44 uses the second
The motor current is determined based on the control data D2 and the steering torque. When the second control data D2 is used instead of the first control data D1 as described above, the motor current can be reduced, so that heat generation of the motor 2 is suppressed and overheating of the motor 2 is prevented. be able to. Further, the temperature of the motor 2 further rises and the third temperature region J
When shifting to 3, the second control data D2
Instead, the second control data D3 is used to determine the motor current. Therefore, the motor current is further reduced, the heat generation of the motor 2 is suppressed, and the overheat of the motor 2 is prevented more reliably.

As the heat generation temperature of the motor 2 rises, the first
When the control data D1 of No. 2 is switched to the second control data D2, D3, the relationship between the steering angle and the steering force required by the driver is shown by the solid line L1 as shown in FIG. The relationship shown in FIG. 3 shifts to the relationship shown by solid lines L2 and L3. As shown in FIG. 2, the first control data D1 is data that causes the motor current to increase relatively steeply as the steering torque increases, and therefore, as shown by the solid line L1 in FIG. When the motor current reaches the predetermined upper limit value i by steering the steering wheel so that the angle becomes the predetermined angle α, the steering force is suddenly changed.
On the other hand, the second control data D2 and D3 have a gradual increase in the motor current as the steering torque increases as compared with the first control data D1. Therefore, the solid lines L2 and L3 in FIG. As shown in, the change in the steering force when the steering angle is equal to or larger than the predetermined angle α or an angle close to the predetermined angle α can be made gentler than in the case shown by the solid line L1 in FIG. Therefore, it is possible to improve the operability by preventing the driver from feeling a large discomfort in the steering operability.

When the first control data D1 used to determine the motor current is sequentially switched to the second control data D2 and D3, the motor current and the steering assist force fluctuate. The steering force required for this also changes at that time. On the other hand, the first and second control data D1 and D2, and the second control data D
If the contents of 2 and D3 are not so different from each other, it is possible to reduce the change in the steering force when the control data is switched so that the driver does not feel uncomfortable. is there. Especially,
In the present embodiment, as the second control data,
There are two control data D2 and D3, and the data used for determining the motor current goes from the first control data D1 to the second control data D2 and then to the second control data D.
Since the control data is sequentially switched to 3, it is possible to preferably greatly reduce the motor current without causing a large change in the steering force when switching the control data.

The present invention is not limited to the contents of the above embodiment. For example, the second control data is not limited to two, and may be one or more than two. The more the second control data is, the finer the drive power of the motor can be controlled to make the change in the steering force required by the driver more gradual. Further, the first and second control data need not be map data as shown in FIG. 2, but are, for example, arithmetic expression data for calculating the motor current based on the value of the steering torque. Good. The first and second control data are not limited to the relationship between the steering torque and the motor current, but may be the relationship between the steering torque and the motor voltage.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a schematic structure of an electric power steering control device according to the present invention.

FIG. 2 is a graph defining a relationship between a steering torque and a current flowing through a motor according to the present invention.

FIG. 3 is a block diagram showing a schematic structure of a control unit shown in FIG.

FIG. 4 is a graph defining a relationship between a steering angle and a steering force according to the present invention.

FIG. 5 is an explanatory diagram showing an example of a schematic structure of a conventional electric power steering control device.

FIG. 6 is a graph defining a relationship between a conventional steering torque and a current flowing through a motor.

FIG. 7 is a graph defining a relationship between a conventional steering angle and a steering force.

[Explanation of symbols]

1 Torque sensor 2 motor 3 storage 4 control unit D1 First control data D2, D3 Second control data

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3D032 CC21 CC50 DA15 DA67 DB11                       DC31 DD02 DE06 DE20 EA01                       EB11 EC23 EC24 GG01                 3D033 CA16 CA20 CA21 CA31

Claims (2)

[Claims] 1. A torque sensor for detecting steering torque,
A motor for applying a steering assist force to the steering mechanism section; a storage section for storing first control data for determining the magnitude of the drive power of the motor corresponding to the change in the steering torque; An electric power steering control device, comprising: a control unit that monitors heat generation of the motor and that determines drive power of the motor based on the steering torque and the first control data. The storage unit stores second control data for reducing the value of the drive power of the motor for the same steering torque as compared with the first control data, and the control means includes: When it is determined that the motor is in a constant heat generation state, the drive power of the motor is changed by using the second control data instead of the first control data. Characterized in that it is configured to determine that electric power steering control system. 2. The storage unit stores a plurality of second control data, and the control means controls the plurality of second controls according to a heat generation state of the motor. The electric power steering control device according to claim 1, wherein the electric power steering control device is configured to selectively use the usage data.