JP3585595B2 - Electric power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that calculates an engine speed from pulsations of an alternator.
[0002]
[Prior art]
In the conventional electric power steering apparatus shown in FIGS. 3 to 5, an electric motor m for applying an assist force is connected to a battery B via a controller C. The alternator 1 is connected to the battery B. The alternator 1 is linked to an engine (not shown) and generates an AC voltage. Moreover, the alternator 1 has a rectifying function, and can rectify the AC voltage and store it in the battery B.
Note that a regulator (not shown) is incorporated in the alternator 1 to adjust the power generation amount of the alternator 1. For example, when the battery voltage rises, the regulator stops the alternator 1 from generating power. On the other hand, when the battery voltage drops, the regulator causes the alternator 1 to start generating power. In this way, the regulator controls the alternator 1 to turn on and off, so that the charge amount of the battery B is kept constant.
[0003]
The controller C controls the electric motor m. The controller C applies a voltage to the electric motor m to rotate the electric motor m forward or reverse, a control circuit 3 for controlling the drive circuit 2, and switching between a main power supply and a backup power supply to be applied to the controller C. And a power supply circuit 4 for controlling the power supply.
Further, the control circuit 3 controls the drive circuit 2, the reading unit 5 that reads the pulsation frequency or cycle of the alternator from the power supply voltage V, and calculates the engine speed N from the read pulsation frequency or cycle. And a calculation unit 6.
[0004]
In this conventional electric power steering apparatus, the engine speed N is calculated as follows.
A voltage obtained by rectifying the generated AC voltage of the alternator 1 is superimposed on the power supply voltage V.
Here, since the alternator 1 is linked to the engine, the AC voltage generated by the alternator 1 has a pulsation proportional to the engine speed. Then, the rectified voltage of the AC voltage includes a pulsation of the AC voltage.
That is, as shown in FIG. 4, the pulsating voltage of the alternator 1 is included in the power supply voltage V. Therefore, if the pulsation frequency or cycle of the power supply voltage V is read by the reading unit 5, the pulsation frequency or cycle of the alternator 1 can be known. Then, if the pulsation frequency or cycle of the alternator 1 can be known, the calculation unit 6 can calculate the engine speed N.
[0005]
In this conventional example, the calculated engine speed N is transmitted to the control unit 7, and the drive circuit 2 is controlled accordingly.
That is, since the engine speed N is substantially proportional to the vehicle speed v, for example, in a low speed region where the calculated engine speed N is low, the control unit 7 controls the drive circuit 2 to apply a large assist force. On the other hand, in the high-speed range where the engine speed N is high, the control unit 7 controls the drive circuit 2 and hardly applies an assist force.
As described above, the assist force according to the vehicle speed v can be applied without providing the vehicle speed sensor, and the cost can be reduced and the size can be reduced.
[0006]
Further, the switching of the controller C can be controlled by the calculated engine speed N. For example, if the calculated engine speed N is larger than the set value, the control circuit 3 drives the power supply circuit 4 to apply the main power to the controller C. On the other hand, if the engine speed N is equal to or less than the set value, the control circuit 3 determines that there is no need to start the system, and drives the power supply circuit 4 to apply only the backup power to the controller C. Therefore, there is no need to link the switching of the controller C to an external ignition switch or the like, and external wiring can be reduced, and the cost and size of the electric power steering device can be reduced.
[0007]
[Problems to be solved by the invention]
In the above-described conventional electric power steering apparatus, the control unit 7 controls the drive circuit 2 according to the calculated engine speed N.
However, the engine speed N and the vehicle speed v are not necessarily proportional to the vehicle speed v, especially during acceleration of a vehicle whose transmission is shifted, and as shown in FIG. Becomes large.
Therefore, when the assisting force is applied according to the engine speed N, the steering may feel uncomfortable.
SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric power steering device capable of applying an assist force in accordance with a calculated engine speed and improving a steering feeling when the vehicle is accelerating.
[0008]
[Means for Solving the Problems]
The present invention provides an electric motor that applies an assist force, a controller that includes a drive circuit that controls the assist force by applying a voltage to the electric motor, a controller that controls the drive circuit, a battery connected to the controller, and an engine. An alternator associated therewith, and the control circuit of the controller includes a reading unit that reads a pulsation frequency or a cycle of the alternator, a calculation unit that calculates an engine speed from the read frequency or the cycle, and a calculated engine speed. It is assumed that an electric power steering device includes a control unit that controls a drive circuit according to the number.
The control circuit is provided with a data suppression unit that suppresses the calculated engine speed and transmits the result to the control unit when it is determined that the change in the calculated engine speed is greater than the change in the vehicle speed. Having.
With such a configuration, when the data suppression unit determines that the calculated engine speed is greater than the fluctuation of the vehicle speed, the engine speed is suppressed and transmitted to the control unit. Therefore, the control unit does not control the drive circuit based on the greatly changed engine speed, so that the steering feeling at the time of acceleration of the vehicle or the like can be improved.
[0009]
According to a second aspect of the present invention, in the first aspect, the data suppression unit is configured to input the engine speed calculated at regular intervals, while the data suppression unit sets the latest engine speed to the last time. Calculating the difference between the two engine speeds, and, if the difference between the two engine speeds does not exceed the set fluctuation range per fixed time, transmitting the latest engine speed to the control unit as it is. When the difference between the rotation speeds exceeds the set fluctuation range per fixed time, the latest engine rotation speed is suppressed to the one where the previous engine rotation speed fluctuated by the set fluctuation range and transmitted to the control unit. It is characterized in that it is configured to execute a program.
With this configuration, if the difference between the latest engine speed and the previous engine speed exceeds the set fluctuation range per fixed time, the latest engine speed fluctuates greatly compared to the vehicle speed. Is determined. Then, in this case, the latest engine speed is transmitted to the control unit while being suppressed that the previous engine speed has changed by the set variation width.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
In the embodiment of the present invention shown in FIGS. 1 and 2, the control circuit 3 includes a data suppression unit 8 between the calculation unit 6 and the control unit 7. The rest of the configuration is exactly the same as in the above-described conventional example, and a detailed description thereof will be omitted.
In the control circuit 3, based on the cycle T read by the reading unit 5, the calculation unit 6 calculates the engine speed N. That is, in the calculation unit 6, the following equation N = 60 / k · a · T
k: Number of poles of alternator (pulsation generated by one revolution of alternator)
a: Pulley ratio (Rotation ratio between engine and alternator)
T: Period (sec)
From the engine speed N.
Then, the engine speed N calculated in this way is transmitted to the data suppression unit 8.
[0011]
If the data suppression unit 8 determines that the fluctuation of the calculated engine speed N is larger than the fluctuation of the vehicle speed, the data suppressing unit 8 suppresses the engine speed N and transmits the result to the control unit 7. In this embodiment, the data suppression unit 8 suppresses the greatly fluctuated engine speed N by executing a program corresponding to the flowchart shown in FIG.
The data suppression unit 8 receives the engine speed N calculated by the calculation unit 6 at regular time intervals t. The data suppression unit 8 has a memory function of storing the latest input engine speed _Nx and the last input engine speed _Nx-1 .
In step 101, the latest engine speed N _x input and the engine speed N _x-1 input to the last time are compared.
Then, and in step 102 obtains a difference between the engine speed _{N x-1} input to these latest engine rotational speed _{N x} and the previous. For example, in step 101, the more recent engine speed _{N x} is greater than the previous engine rotational speed _{N x-1,} in step _102, calculates a N _{x -N x-1.} In contrast, at step 101, if more of the previous engine rotational speed _{N x-1} is greater than the latest engine speed _{N x,} in step _103, calculates the _{N x-1} -N _x.
[0012]
Further, in step 102, and compares these difference between the engine speed _{N x} and _{N x-1,} the width of the setting change per predetermined time t alpha, and β (> 0).
For example, in step 102, N _x −N _x−1 is compared with the set fluctuation range β. _Then, if not exceed the N _{x -N x-1} is set fluctuation range beta, _i.e., if _{N x -N x-1 <β} , conveyed directly to the control unit 7 that the latest engine speed _{N x} Can be
_However, when the N _{x -N x-1} exceeds the set variation range beta, _i.e., if _{N x -N x-1 ≧ β} , the latest engine speed _{N x} not vary significantly compared to the vehicle speed Are considered to be In this case, the latest engine speed _Nx is transmitted to the control unit 7 assuming that the previous engine speed _Nx-1 has changed by the variation width β. That is, in step 104, the latest engine speed _Nx = _Nx-1 + β is suppressed and transmitted to the control unit 7.
[0013]
Similarly, in step 103, N _x−1 −N _x is compared with the set variation width α. If N _x−1 −N _x does not exceed the set fluctuation range α, that is, if N _x−1 −N _x <α, the latest engine speed N _x is transmitted to the control unit 7 as it is. .
However, if N _x−1 −N _x exceeds the set fluctuation range α, that is, if N _x−1 −N _x ≧ α, the latest engine speed N _x greatly fluctuates compared to the vehicle speed. Are considered to be In this case, the latest engine speed _Nx is transmitted to the control unit 7 assuming that the previous engine speed _Nx-1 has changed by the variation width. That is, in step 105, is transmitted to the control unit 7 is inhibited and the latest engine speed _{N x = N x-1 -β} .
[0014]
In step 101, if the latest engine speed _Nx is the same as the previously input engine speed _Nx-1 , the engine speed is held as it is. Here, the set fluctuation widths α and β per fixed time t may be arbitrarily determined by a vehicle running test or experiment. For example, in a driving test, when the vehicle accelerates from akm / s to bkm / s in a certain period of time, the engine speed N (b) when the vehicle speed reaches bkm / s is measured, and the engine speed N (b) is measured. ) May be determined as the set variation width β.
[0015]
Next, the operation of the electric power steering device will be described more specifically.
Now, it is assumed that the vehicle is accelerated from the stopped state of the vehicle. At this time, the transmission is shifted, so that the fluctuation of the engine speed N is larger than the fluctuation of the vehicle speed v as shown in FIG. At this time, when the engine speed N calculated for each fixed time t changes beyond the set fluctuation ranges α and β per fixed time t according to the flowchart shown in FIG. And outputs it to the control unit 7. Therefore, even if the control unit 7 controls the drive circuit 2 according to the engine speed N, the steering does not feel uncomfortable.
In a state where the vehicle is running normally, the engine speed does not change beyond the set fluctuation ranges α and β per a fixed time t, and the assist force is changed according to the calculated engine speed as it is. May be added.
Also, when the vehicle speed is decelerated, as in the case of acceleration, if the engine speed N calculated for each fixed time t changes beyond the set fluctuation ranges α and β per fixed time t, the engine speed And outputs it to the control unit 7. Therefore, even if the control unit 7 controls the drive circuit 2 according to the engine speed N, the steering does not feel uncomfortable.
[0016]
【The invention's effect】
According to the first and second aspects of the invention, the assist force is applied in accordance with the calculated engine speed. Moreover, when the engine speed fluctuates greatly compared to the vehicle speed, such as when the vehicle is accelerating, the control unit does not control the drive circuit based on the engine speed, so that the steering feeling can be improved.
In particular, according to the second aspect, when the latest engine speed exceeds a set fluctuation range per a certain time, the control unit is suppressed to that the previous engine speed has fluctuated by the set fluctuation range. Conveyed to. Therefore, the degree of suppression can be freely set by changing the set fluctuation range per fixed time.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an electric power steering device according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a program executed by a data suppression unit 8;
FIG. 3 is a circuit diagram of a conventional electric power steering device.
FIG. 4 shows a characteristic of a pulsating voltage of the alternator 1 superimposed on the power supply voltage V.
FIG. 5 is a diagram illustrating an example of a change characteristic of an engine speed and a vehicle speed during acceleration of a vehicle.
[Explanation of symbols]
m Electric motor C Controller B Battery 1 Alternator 2 Drive circuit 3 Control circuit 5 Reading unit 6 Calculating unit 7 Control unit 8 Data suppressing unit t For a certain time

Claims (2)

An electric motor for applying an assist force, a controller including a drive circuit for controlling the assist force by applying a voltage to the electric motor, and a controller including a control circuit for controlling the drive circuit; a battery connected to the controller; and an alternator linked to the engine. The control circuit of the controller further includes a reading unit that reads the pulsation frequency or cycle of the alternator, a calculating unit that calculates the engine speed from the read frequency or cycle, and a control unit that calculates the engine speed based on the calculated engine speed. In an electric power steering apparatus comprising a control unit for controlling a drive circuit, the control circuit suppresses the calculated engine speed when it determines that the calculated change in engine speed is greater than the change in vehicle speed. A data suppression unit for transmitting the data to the control unit. Steering apparatus. The data suppression unit is configured to receive an input of the engine speed calculated at regular intervals, while the data suppression unit compares the latest engine speed with the previous engine speed to determine the difference therebetween. If the difference between these two engine speeds does not exceed the set fluctuation range per fixed time, the step of transmitting the latest engine speed to the control unit as it is, and the difference between both engine speeds becomes the set fluctuation range per fixed time And executing a program that suppresses the latest engine speed to the value that the previous engine speed has fluctuated by the set fluctuation range and transmits the latest engine speed to the control unit when the engine speed has exceeded the limit. An electric power steering device as described in the above.

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