JP2009231409A - Linear solenoid driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a short-circuit failure of a linear solenoid, without causing secondary failures. <P>SOLUTION: A CPU 3 outputs a PWM signal, in which the duty ratio is fixed to a prescribed value, when drive of a linear solenoid 1 is stopped, and the CPU detects a short-circuit failure of the linear solenoid 1, on the basis of a conducting state of the linear solenoid 1 made conductive by the PWM signal, in which the duty ratio is fixed to the prescribed value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a linear solenoid driving device that detects a short circuit failure in a device including a linear solenoid.

Conventionally, the current value that flows through the linear solenoid is detected as the voltage value across the resistance element connected in series with the linear solenoid, and the energization current of the linear solenoid is controlled so that the detected voltage value becomes the desired voltage value. A linear solenoid driving device is known. This device detects the value of the current flowing through the linear solenoid, corrects the duty ratio of the PWM signal that drives the linear solenoid based on the detection result, and compares the corrected duty ratio with the reference duty ratio to linearly Detects a solenoid short failure.
Japanese Patent Laid-Open No. 7-194175

  According to the conventional short failure detection method, when the target current value of the linear solenoid is small, the difference between the corrected duty ratio and the reference duty ratio is small, and thus there is a possibility that a short failure is erroneously detected. For this reason, the conventional linear solenoid drive device detects a short-circuit failure of the linear solenoid when the reference duty ratio is large, that is, when the target current value of the linear solenoid is large. However, when a short fault has occurred in the linear solenoid, a short current having a magnitude proportional to the magnitude of the reference duty ratio flows through the drive circuit and harness when the PWM signal is in the ON state. For this reason, if a short-circuit failure is detected when the reference duty ratio is large, when the short-circuit failure occurs, a large short-circuit current flows through the drive circuit and the harness and the load increases, which may cause a secondary failure. .

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a linear solenoid driving device capable of detecting a short-circuit failure of a linear solenoid without causing a secondary failure.

  The linear solenoid drive device according to the present invention outputs a PWM signal whose duty ratio is fixed to a predetermined value or less when the linear solenoid is stopped, and is energized by the PWM signal whose duty ratio is fixed to a predetermined value or less. The linear solenoid short-circuit failure is detected on the basis of the energization state.

  According to the linear solenoid driving device of the present invention, it is possible to detect a short-circuit failure of the linear solenoid without causing a secondary failure.

  Hereinafter, a configuration of a linear solenoid drive device according to an embodiment of the present invention and a short failure detection method thereof will be described with reference to the drawings. In this embodiment, it is assumed that the linear solenoid driving device is provided for each of a plurality of (for example, six) linear solenoids that are mounted on a vehicle and perform shift control of the vehicle.

[Configuration of linear solenoid drive unit]
As shown in FIG. 1, a linear solenoid driving apparatus according to an embodiment of the present invention includes a current feedback circuit 2 that drives a linear solenoid (linear SOL) 1 and a current value that flows through the linear solenoid 1 (solenoid driving circuit current value). A CPU 3 that performs feedback control so that Isol becomes a target current value is provided as a main component. The current feedback circuit 2 detects the voltage across the current monitor resistance element 4 connected in series to the linear solenoid 1 as a monitor current value, and outputs a signal corresponding to the magnitude of the detected monitor current value. The circuit 5 includes a filter circuit including a resistor R1 and a capacitor C1 that smoothes the output signal of the current monitor circuit 5 and inputs the smoothed signal to the A / D port 6 of the CPU 3. The current feedback circuit 2 further supplies the electric power of the battery power source VB in accordance with the duty ratio of the PWM signal (solenoid drive signal) output from the drive signal output port 7 of the CPU 3 according to the input signal to the A / D port 6. And a drive circuit 8 for supplying to the circuit.

[Short failure detection method for linear solenoid]
The linear solenoid driving device detects a short-circuit failure of the linear solenoid 1 by executing a short-circuit failure detection process described below. Hereinafter, with reference to the flowchart shown in FIG. 2, the flow of the operation of the linear solenoid drive device when executing the short failure detection process will be described.

  The flowchart shown in FIG. 2 starts when the ignition switch of the vehicle is switched from the off state to the on state, that is, before the vehicle starts running, and the short failure detection process proceeds to step S1.

  In the process of step S1, the CPU 3 determines whether or not the linear solenoid 1 is in a drive stop state. As a result of the determination, if the linear solenoid is not in the drive stop state, the CPU 3 advances the short failure detection process to the process of step S8. On the other hand, when the linear solenoid is in the drive stop state, the CPU 3 advances the short failure detection process to the process of step S2. In addition, the process of this step S1 shall be repeatedly performed for every predetermined control period.

  In step S2, the CPU 3 outputs a PWM signal whose duty ratio is fixed to a predetermined value or less so that the linear solenoid 1 is energized with a weak current that does not affect the control of the linear solenoid 1 or has a small effect. Output as a short diagnosis signal. However, if a signal has already been output by the previous short failure detection process, the CPU 3 maintains the output of the signal. Note that the “control object of the linear solenoid 1” here can be exemplified by a hydraulic cylinder, a pneumatic cylinder, a fuel injection valve, etc. of the vehicle, and “the control object is not affected or is less influenced” is controlled. This means that the vehicle behavior does not change due to the change in the target operating state. Thereby, the process of step S2 is completed, and the short failure detection process proceeds to the process of step S3.

  In the process of step S3, the CPU 3 determines whether or not the input voltage to the A / D port 6 is greater than or equal to a predetermined threshold value. Specifically, when the linear solenoid 1 is in a normal state, a weak current (for example, about 37 mA) corresponding to the duty ratio of the PWM signal flows through the linear solenoid 1 by outputting a PWM signal from the CPU 3 ( The current monitor circuit 5 outputs a voltage proportional to the weak current (see FIG. 3C), and the A / D port 6 has a voltage corresponding to the output voltage of the current monitor circuit 5 (see FIG. 3B). (Normal voltage, for example, about 2.1 V) is input (see FIG. 3D).

  On the other hand, when the linear solenoid 1 is in a short-circuit failure state, since the inductance component of the linear solenoid 1 disappears, the current monitor circuit 5 outputs a pulse signal synchronized with the PWM signal output from the CPU 3 (FIG. 3 ( b)), a short current (for example, 9 A) flows through the drive circuit 8, and as a result, a voltage higher than normal (voltage at the time of abnormality, for example, about 2.2 V) is input to the A / D port 6 ( Voltage input to A / D port, FIG. 3 (d) solid line chain line).

  Therefore, the CPU 3 sets a predetermined threshold value (see the two-dot chain line in FIG. 3D) to a value between the normal voltage and the abnormal voltage, and the input voltage to the A / D port 6 is equal to or higher than the predetermined threshold value. It is determined whether or not there is. However, since the output current of the drive circuit 8, the output voltage of the current monitor circuit 5, and the input voltage to the A / D port 6 fluctuate depending on the voltage of the battery power supply VB, the short-circuit failure of the linear solenoid 1 is further increased. In order to accurately detect, for example, the CPU 3 refers to a prepared table indicating the correspondence between the magnitude of the battery power source VB and the predetermined threshold value, and sets the predetermined threshold value according to the magnitude of the voltage of the battery power source VB. It is desirable to change.

  As a result of the determination, if the input voltage to the A / D port 6 is not equal to or greater than the predetermined threshold value, the CPU 3 advances the short failure detection process to the process of step S8. On the other hand, if the input voltage to the A / D port 6 is equal to or higher than the predetermined threshold, the CPU 3 advances the short failure detection process to the process of step S4.

  In the process of step S4, the CPU 3 increments the value of the program counter (NG count) for counting the number of times that the input voltage to the A / D port 6 is determined to be greater than or equal to a predetermined threshold. Thereby, the process of step S4 is completed, and the short failure detection process proceeds to the process of step S5.

  In the process of step S5, the CPU 3 determines whether or not the value of the program counter is a predetermined threshold value N0 (for example, 50). As a result of the determination, if the value of the program counter is not the predetermined threshold N0, the CPU 3 returns the short failure detection process to the process of step S1. On the other hand, if the value of the program counter is the predetermined threshold N0, the CPU 3 advances the short failure detection process to the process of step S6.

  In the process of step S6, the CPU 3 determines that the linear solenoid 1 is in a short circuit failure state. Thereby, the process of step S6 is completed and CPU3 advances a short fault detection process to the process of step S7.

  In the process of step S7, the CPU 3 executes a fail safe operation. Specifically, as a fail-safe operation, an operation for notifying the vehicle driver of a short-circuit failure of the linear solenoid 1 or an ATCU (Automatic Transmission Control Unit) stops driving all linear solenoids. The operation | movement etc. which fix to 3rd speed (4th speed fixation) by a function can be illustrated. Thereby, the process of step S7 is completed and a series of short failure detection processes are completed.

  In the process of step S8, the CPU 3 resets the value of the NG count to zero. Thereby, the process of step S8 is completed, and the short failure detection process returns to the process of step S1.

  As is clear from the above description, in the linear solenoid drive device according to the embodiment of the present invention, the CPU 3 outputs a PWM signal in which the duty ratio is fixed to a predetermined value or less when the linear solenoid 1 is stopped, and the duty ratio Is detected based on the energized state of the linear solenoid 1 energized by the PWM signal fixed at or below a predetermined value. According to such a short-circuit failure detection method, even if a short-circuit failure occurs in the linear solenoid 1, the duty ratio of the PWM signal is fixed to a predetermined value or less, and the short-circuit current flowing through the drive circuit and harness is Since it is small, the load on the drive circuit and the harness is small, and it is possible to prevent a secondary failure from occurring. As a result, the drive circuit and the harness can be configured with a low-capacity member (material), so that the cost of the drive circuit and the harness can be reduced. Furthermore, since a short circuit failure can be detected when the linear solenoid 1 is stopped driving, a safer vehicle control can be performed by detecting the short circuit failure before traveling the vehicle such as when the engine is started. Further, in the short circuit failure detection process according to the embodiment of the present invention, the duty ratio is not corrected by feedback control, so that the short circuit failure can be reliably detected.

  As mentioned above, although embodiment which applied the invention made | formed by this inventor was described, this invention is not limited with the description and drawing which make a part of indication of this invention by this embodiment. For example, the numerical values such as voltage value and current value and the duty ratio in this embodiment can be set to optimum values based on the circuit configuration, the characteristics of the linear solenoid 1, the system requirements, and the like. As described above, other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

  The present invention can be applied to detection of a short-circuit failure of a linear solenoid.

It is a block diagram which shows the structure of the linear solenoid drive device used as embodiment of this invention. It is a flowchart figure which shows the flow of the short fault detection process used as embodiment of this invention. It is a wave form diagram which shows the time change of the linear solenoid drive circuit current value, the current monitor circuit output signal, and the A / D port voltage when the linear solenoid is normal and when a short circuit failure occurs. It is a wave form diagram which shows the time change of the linear solenoid drive circuit current value, current monitor circuit output signal, and A / D port voltage for demonstrating that a short circuit failure cannot be detected by current feedback control.

Explanation of symbols

1: Linear solenoid (Linear SOL)
2: Current feedback circuit 3: CPU
4: Current monitor resistor element 5: Current monitor circuit 6: A / D port 7: Drive signal output port 8: Drive circuit R1: Resistor C1: Capacitor

Claims (4)

Drive means for driving the linear solenoid by supplying power from the power source according to the PWM signal, detection means for detecting the energization state of the linear solenoid, and short-circuit failure of the linear solenoid based on the energization state detected by the detection means A linear solenoid drive device comprising a detecting means for detecting,
Output means for outputting a PWM signal whose duty ratio is fixed to a predetermined value or less when the linear solenoid is stopped driving, and the detecting means is energized by the PWM signal whose duty ratio is fixed to a predetermined value or less. A linear solenoid drive device that detects a short-circuit failure of the linear solenoid based on the energized state of the linear solenoid. In the linear solenoid drive device according to claim 1,
The linear solenoid driving apparatus according to claim 1, wherein the predetermined value is a value by which a weak current that does not affect the operation of the control target of the linear solenoid is applied to the linear solenoid. In the linear solenoid drive device according to claim 1 or 2,
The linear solenoid drive device, wherein the detection means determines that the linear solenoid is short-circuited when the detection value of the detection means is equal to or greater than a predetermined threshold value. In the linear solenoid drive device according to claim 3,
The linear solenoid driving apparatus according to claim 1, wherein the detecting means changes the predetermined threshold according to a voltage of the power source.

Images