JPH08133115A - Power steering controller - Google Patents

Abstract

PURPOSE: To provide a power steering controller which can prevent the value of an electric current flowing into a solenoid coil from increasing undesirably due to disconnection and a short circuit and at the same time can control the electric current value accurately. CONSTITUTION: When a transistor 3 becomes ON, an electric current ION flows from a DC power source 7 through a resistor 5, the transistor 3, and a solenoid coil 1 (for power steering). An ECU 27 detects both terminal voltage of the resistor 5 through an operation amplifier 19 or the like, and controls the electric current value ION. As the resistor 5 is provided upstream of the solenoid coil 1, even if disconnection and a short circuit are generated downstream of the solenoid coil 1, it can detect accurately the electric current value ION flowing into the solenoid coil 1. Also, as the resistor 5 is provided upstream of the transistor 3, even if voltage drop by means of the transistor 3 is changed, both terminal voltage of the resistor 5 is not affected much.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering control device for generating a steering assist force by passing a current through a solenoid coil.

[0002]

2. Description of the Related Art Conventionally, as a power steering control device of this type, for example, a steering assist force generating means having a solenoid coil for generating a steering assist force according to a current value flowing through the solenoid coil, Switching means for opening and closing the energization path to the solenoid coil, current detecting means for detecting the current value flowing through the solenoid coil, and controlling the open / closed state of the switching means based on the current value detected by the current detecting means A control means is provided.

For example, in Japanese Unexamined Patent Publication No. 60-234070, the current value flowing through the solenoid coil is detected downstream of the solenoid coil (on the side of the ground electrode), and the current value becomes a predetermined value according to the vehicle speed. As described above, a device for opening and closing the energization path to the solenoid coil is described.

However, when a current value is detected downstream of the solenoid coil, if a disconnection or a short circuit occurs between the solenoid coil and its detecting portion, it is as if the current value flowing through the solenoid coil is significantly reduced. Judgment is made. Then, the control unit may continuously control the switching unit to be in the closed state, and may undesirably increase the current value actually flowing through the solenoid coil.

Therefore, as illustrated in FIG. 4, a device is proposed which detects a current value upstream of the solenoid coil 51 (on the side of the DC power supply 53) and controls the open / closed state of the transistor 55 (switching means) based on the detected current value. Has been done. FIG.
In the power steering control device illustrated in FIG. 1, one end 51a (+ side) of the solenoid coil 51 that generates a steering assist force according to the current value is connected to the DC power source via the resistor 57 and the emitter 55e / collector 55c of the transistor 55. It is connected to 53. Also, the solenoid coil 51
The other end 51b (-side) of is connected to the body 61 (ground electrode). Furthermore, the emitter 5 of the transistor 55
A diode 63 is connected between 5e and the body 61 to selectively pass only a current flowing from the body 61 toward the emitter 55e.

Therefore, when the transistor 55 is turned on,
A current ION flows from the DC power supply 53 through the transistor 55, the resistor 57, and the solenoid coil 51. When the transistor 55 is turned off, the current IOFF flows through the diode 63, the resistor 57, and the solenoid coil 51. Therefore, the voltage drop across the resistor 57 is
Sum of current values flowing through the solenoid coil 51 Iθ (=
Proportional to ION + IOFF).

The voltage across the resistor 57 is input to the non-inverting input terminal and the inverting input terminal of the operational amplifier 69 through the resistor 65 on the + side and the resistor 67 on the − side, respectively. Further, a DC power supply 73 is connected between the resistor 65 and the operational amplifier 69 via the resistor 71. A resistor 75 is connected between the output terminal and the inverting input terminal of the operational amplifier 69. Furthermore, the DC power supply 73
Is a DC power supply 53 that is divided by the voltage dividing resistors 77 and 79.
Is taken out through the operational amplifier 81 to which the negative recovery is applied.

Thus, the two operational amplifiers 69 and 81 are
By inputting the voltage across the resistor 57 to the current detection circuit 83 mainly configured by, the voltage VFD corresponding to the voltage drop due to the resistor 57 can be obtained. For example, the resistance values of the resistors 57, 67, 75, 71, 65 are set to R5, R6, R7, R8, R9, respectively, and the voltage of the emitter 55e of the transistor 55 and the voltage of the DC power supply 73 are respectively set to V1, E1, the output voltage VFD of the operational amplifier 69 is given by the following equation.

[0009]

[Equation 1]

This voltage VFD together with a predetermined voltage corresponding to a target current value for energizing the solenoid coil 51 is compared with the comparison circuit 8
Input to 5. The comparison result of the comparison circuit 85 is input to the duty ratio calculation circuit 87, and the duty ratio calculation circuit 87 is input.
Calculates the duty ratio according to the comparison result. The calculated duty ratio is converted into a pulse signal by the pulsing circuit 89, and then input to the base electrode 55b of the transistor 55 via the driver 91.

With the above-described structure, the duty ratio for the transistor 55 to open and close the energization path to the solenoid coil 51 is changed according to the current value Iθ flowing through the solenoid coil 51, and the current value Iθ is controlled to the target current value. can do. In addition, the solenoid coil 5
If the current value Iθ flowing through 1 is detected upstream of the solenoid coil 51, the current value Iθ actually flowing through the solenoid coil 51 can be satisfactorily detected even if disconnection or short circuit occurs downstream of the solenoid coil 51. be able to. Therefore, it is possible to prevent the current value Iθ from undesirably increasing.

[0012]

However, as described above, the formula for obtaining the voltage VFD is expressed by the voltage V1 of the emitter 55e.
Exists. The voltage drop between the collector 55c and the emitter 55e is not necessarily constant depending on the current value Iθ, the temperature of the transistor 55, and the like. Therefore, the voltage VFD is
It cannot be said that the parameter corresponds sufficiently well to the current value Iθ. Therefore, the current value I flowing through the solenoid coil 51
There was a limit to the precise control of θ.

Therefore, the present invention provides a power steering control device capable of preventing the current value flowing through the solenoid coil from undesirably increasing due to disconnection or short circuit, and accurately controlling the current value. It was made for the purpose of doing.

[0014]

The present invention, which has been made to achieve the above object, has a solenoid coil as shown in FIG. 5, and a steering assist force is provided in accordance with a current value flowing through the solenoid coil. Steering assisting force generating means for generating, switching means for opening and closing the energization path to the solenoid coil, current detecting means for detecting a current value flowing through the energization path upstream of the solenoid coil and the switching means, and the switching SUMMARY OF THE INVENTION A gist of a power steering control device is characterized by including: a control unit that controls an open / closed state of the switching unit based on a current value detected by the current detection unit when the energization path is closed by the unit. .

[0015]

In the power steering control device of the present invention configured as described above, the current detecting means detects the value of the current flowing through the energization path upstream of the solenoid coil. Therefore, even if a disconnection or short circuit occurs in the downstream of the solenoid coil, the current value detected by the current detection means when the energization path is closed matches well with the current value flowing through the solenoid coil. Further, in the present invention, the current detection means detects the value of the current flowing through the energization path upstream of the switching means. Therefore, even if the voltage drop in the switching means changes, the current value detected by the current detecting means is not affected so much.

Therefore, according to the present invention, it is possible to prevent the value of the current flowing through the solenoid coil from undesirably increasing due to disconnection or short circuit, and to control the current value accurately. Further, for this reason, it is not necessary to perform special control such as backup at the time of disconnection or short circuit, and the configuration of the device can be simplified.

[0017]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a power steering control device of an embodiment. As shown in FIG. 1, in the power steering control device according to the present embodiment, one end 1a (+ side) of the solenoid coil 1 that generates a steering assist force according to a current value.
Is connected to the DC power supply 7 via the emitter 3e and collector 3c of the transistor 3 and the resistor 5. The other end 1b (− side) of the solenoid coil 1 is connected to the body 11 (earth electrode). Further, between the one end 1a of the solenoid coil 1 and the body 11, a diode 13 that selectively passes only the current from the body 11 toward the one end 1a is connected.

Regarding the voltage across the resistor 5, the positive side is the resistor 15
To the inverting input terminal 19a of the operational amplifier 19 and the negative side to the non-inverting input terminal 19b of the operational amplifier 19. The output terminal 19c of the operational amplifier 19 is connected to the base 21b of the transistor 21, and the inverting input terminal 19a is connected to the body 11 via the collector 21c / emitter 21e of the transistor 21 and the resistor 23. Further, the voltage VFD of the emitter 21e is input to the ECU 27 together with the detection signal of the vehicle speed sensor 25. The ECU 27 is a microcomputer having CPU, ROM, and RAM as main parts, and drives the transistor 3 via the driver 29 based on the voltage VFD and the detection signal of the vehicle speed sensor 25.

Next, the circuit operation of this power steering control device and the processing of the ECU 27 will be described. When the transistor 3 is turned on, a current ION flows from the DC power supply 7 through the resistor 5, the transistor 3 and the solenoid coil 1. When the transistor 3 is turned off, the current IOFF
Flows through the diode 13 and the solenoid coil 1. Therefore, the voltage drop due to the resistor 5 is proportional to the current value ION flowing through the solenoid coil 1, and the sum of the current values flowing through the solenoid coil 1 Iθ (= ION + IOFF)
And have a good correspondence.

Further, the operational amplifier 19 drives the transistor 21 so that the voltage drop across the resistor 5 and the voltage drop across the resistor 15 match. Therefore, the resistor 5,
The resistance values of the resistor 15 and the resistor 23 are respectively R
k, R1, R2, a resistor 15, a transistor 21,
Assuming that the current value flowing through the resistor 23 is Iη, the following relationship is obtained: IηR1 = IONRk (1) Therefore, the voltage VFD satisfies the correspondence relationship of VFD = I.eta..multidot.R2 = ION.multidot.Rk.multidot.R2 / R1 (2). This equation (2) does not include parameters that vary according to the driving state of the solenoid coil 1 other than the current value ION. Therefore, the voltage VFD very well reflects the current value ION. Therefore, the ECU 27 drives the transistor 3 based on this voltage VFD as follows.

FIG. 2 is a flowchart showing a power steering control process in which the ECU 27 drives the transistor 3. When the ignition switch (not shown) is turned on, the ECU 27 repeatedly executes this process every predetermined time. When the processing is started, first, step 101
At, the target value of the current value ION (target current value It) is calculated based on the vehicle speed detected via the vehicle speed sensor 25. In the following step 103, the detected value (detected current value Ik) of the current value ION is calculated based on the input voltage VFD. Further, in the following step 105, the process waits until the transistor 3 is turned on by the drive signal output from the ECU 27 itself.

When the transistor 3 is turned on, step 1
The process proceeds to 07, and it is determined whether the target current value It is larger than the detected current value Ik. Step 1 when It> Ik
After increasing the duty ratio of the drive signal of the transistor 3 in step 11, when it ≦ Ik, the duty ratio is decreased in step 113, and then in step 11 respectively.
Go to 5. In step 115, a pulse is created according to the duty ratio changed in step 111 or 113, and in the following step 117, the pulse is output as a drive signal for the transistor 3, and the process is temporarily terminated.

By this processing, as illustrated in FIG.
The duty ratio (TON / (TON + TOFF) of the drive signal of the transistor 3 is changed so that the voltage VFD (corresponding to the detected current value Ik) when the transistor 3 is turned on varies in the vicinity of the predetermined voltage Vt corresponding to the target current value It. )) Can be controlled. That is, the transistor 3 can be controlled so that the detected current value Ik matches the target current value It, and thus the current value Iθ flowing through the solenoid coil 1 can correspond to the vehicle speed.
Further, in this embodiment, the current value Iθ flowing through the solenoid coil 1 (which corresponds well to the current value ION) is detected by the resistor 5 provided upstream of the solenoid coil 1 and the transistor 3, so Such an effect can be obtained.

That is, the resistor 5 is the solenoid coil 1
Therefore, even if a disconnection / short circuit occurs downstream of the solenoid coil 1, the voltage across the resistor 5 corresponds well to the current value Iθ flowing through the solenoid coil 1. Therefore, it is possible to favorably prevent the current value Iθ flowing through the solenoid coil 1 from undesirably increasing due to a disconnection or a short circuit. Further, since the resistor 5 is provided upstream of the transistor 3, even if the voltage drop due to the transistor 3 changes, the voltage across the resistor 5 is not significantly affected. Therefore, the voltage VFD and the current value Iθ correspond well, and the current value Iθ can be accurately controlled to the target current value It.

Therefore, in this embodiment, it is possible to prevent the current value Iθ flowing through the solenoid coil 1 from undesirably increasing due to disconnection or short circuit, and to control the current value Iθ accurately. Further, for this reason, it is not necessary to perform special control such as backup at the time of disconnection or short circuit, and the configuration of the device can be simplified. In the above embodiment, the transistor 3 corresponds to switching means, the resistor 5 corresponds to current detection means, and the ECU 27 corresponds to control means.

The present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention. For example, in the above embodiment, the voltage VFD is processed by software to obtain the duty ratio of the drive signal of the transistor 3, but the same control can be executed by processing the voltage VFD by hardware. Further, the voltage across the resistor 5 is input to a circuit similar to the current detection circuit 83 of FIG.
May be required.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating a power steering control device according to an embodiment.

FIG. 2 is a flowchart showing a power steering control process of the embodiment.

FIG. 3 is an explanatory diagram showing effects of the power steering control device according to the embodiment.

FIG. 4 is a schematic configuration diagram showing a conventional power steering control device.

FIG. 5 is a structural example of the present invention.

[Explanation of symbols]

1 ... Solenoid coil 3 ... Transistor
5, 15, 23 ... Resistor 7 ... DC power supply 11 ... Body 1
9 ... Operational amplifier 21 ... Transistor 25 ... Vehicle speed sensor 2
7 ... ECU

Claims (1)

[Claims] 1. A steering assist force generating means for generating a steering assist force according to a value of a current flowing through the solenoid coil, a switching means for opening and closing an energization path to the solenoid coil, The switching means based on the current value detected by the solenoid coil and the current value flowing through the energizing path upstream of the switching means, and the current value detected by the current detecting means when the energizing path is closed by the switching means. A power steering control device comprising: a control unit that controls an open / closed state of the power steering system.