JPH01249941A - Protection for solenoid valve driving transistor - Google Patents

Abstract

PURPOSE:To improve the diagnosis precision by surely protecting a driving transistor when trouble is judged by monitoring the output side voltage when the driving transistor is turned ON and by checking the trouble recovery state. CONSTITUTION:A controller unit 20 monitors the voltage on the collector side of the driving transistor 24 of a solenoid valve 9. The duty signal supplied from a duty ratio determining part 23 and the monitor voltage are inputted into a trouble judging part 27, and the trouble of the grounding of a harness 25 is judged from the variation of the monitor voltage in the output of the ON duty. If a trouble is judged, the duty ratio of the duty ratio determining part 23 is compulsorily determined to 0%, and an alarm is displayed by a lamp 28. Further, a trouble recovery check part 29 into which a trouble judgement signal is inputted outputs a duty signal ON periodically for a short time on the basis of a diagnosis map, etc. after the judgement of trouble, and the trouble recovery is checked in the trouble judgement part 27.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for protecting a driving transistor of a solenoid valve used for controlling the amount of intake air in an electronic control system of a vehicle engine, and more specifically, a method for protecting a solenoid valve using a driving transistor when determining a failure in a power supply side control system. Regarding.

[Conventional technology]

In recent years, electronic control of vehicle engines has progressed, and with this, solenoid valves have been used as valve means for controlling the amount of intake air, etc., and the solenoid valves are variably controlled by control signals such as duty signals from the control unit. Air volume M
l, tends to be optimized. In such an electronic control device, the control unit and the solenoid valve are wired by a connecting means such as a harness to form an electric circuit, but it is difficult to guarantee that the harness and solenoid valve are always in a normal state. It is also equipped with a monitoring fault diagnosis device. Conventionally, regarding failure diagnosis of the above-mentioned electronic control system, there is a prior art disclosed in, for example, Japanese Utility Model Application Publication No. 58-86577. Here, it is shown that a control harness and a monitor harness are connected to one sensor, and it is determined whether the sensor is normal or abnormal based on signals from both harnesses.

[The problem that the invention tries to solve! ! ! ]

However, in the prior art described above, the monitor harness is specially wired, which makes the circuit complicated. Furthermore, if the monitor harness is disconnected or has a ground fault, a completely erroneous determination will be made, making the fail-safe system even more complicated. Therefore, it is desirable to diagnose failures without using a monitor harness. Here, as a fault diagnosis method that does not use a monitoring harness, a ground side control circuit is configured in which a power source is always connected to the solenoid valve and the ground side of the solenoid valve is controlled by a drive transistor. By monitoring the voltage at which the solenoid valve of the transistor opens, there is an advantage that an 8m-ground fault between the solenoid valve and the harness can be easily detected at any time based on the monitored voltage. However, in such a circuit configuration for ground side control, if the ground side of the solenoid valve has a ground fault, the solenoid valve is always energized and remains fully open, which is undesirable and may cause the engine to rev up. A power supply side control system connected to the power supply side is preferable to a solenoid valve. By the way, according to the above-mentioned power supply side control method using the drive transistor, when the harness is grounded, the power supply voltage is applied only to the drive transistor instead of the above-mentioned solenoid valve, causing an excessive current to flow, leading to destruction of the transistor. When determining a failure, it is necessary to simultaneously protect the drive transistor. The present invention has been made in view of these points, and its purpose is to be able to reliably protect the drive transistor at the time of failure determination in the @sourcefll# control method, and to further improve failure recovery. It is an object of the present invention to provide a method for protecting a driving transistor of a solenoid valve, which can improve diagnostic accuracy by checking the condition.

[Means to solve the problem]

In order to achieve the above object, the drive transistor protection method of the present invention connects a drive transistor and a power source to one side of the solenoid valve, configures a circuit so that the other side of the solenoid valve is grounded, and inputs the input to the drive transistor. In an electronic control system that controls the current of the solenoid valve using a control signal, a failure is determined by monitoring the output side voltage when the drive transistor is on, and when a failure is determined, the drive transistor is forcibly turned off. It is. Further, it is preferable that after the drive transistor is turned off when determining the failure, the drive transistor is periodically turned on to determine the failure state again, and the drive transistor is maintained in the off state until the failure is recovered.

[For production]

According to the above method, in the power supply side control method of the solenoid valve using the drive transistor, the presence or absence of a failure is determined based on the monitor voltage on the output side of the transistor, and when failure is determined, protection is provided to prevent destruction by controlling the transistor to turn off #J. In addition, after determining a failure, by periodically turning on the transistor and re-judging the failure state, there will be more opportunities for failure diagnosis, which will help improve accuracy. Turning off the transistor will protect it.

【Example】

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, to describe the case where the present invention is applied to intake air amount control, reference numeral 1 is an engine body, and an air cleaner 2 is connected to an intake pipe 3 in the intake system of this engine body 1.
．． Throttle body 5 with throttle valve 4. A multi-point injector 7 is provided on the intake boat side of the engine main body 1, communicating through an intake manifold 6. and throttle valve 4 of throttle body 5
A bypass passage 8 communicates between the upper and the downstream, and a solenoid valve 9 for controlling the idle rotation speed is installed in the bypass passage 8.
is established. The solenoid valve 9 bypasses the throttle valve 4 to take in air, and changes its opening so that the engine speed during idling converges to a target engine speed set by the engine cooling water temperature and the like. In FIG. 2, the electronic control system of the solenoid valve 9 will be described.Water temperature sensor 11. Engine speed sensor 12
and neutral switch 13. Air conditioner switch 1
4. It has a starter switch 15 and the like, of which signals from the engine speed, neutral switch, and starter switch are input to an idle determination section 21 of a control unit 20 to determine the idle state. This idle signal, cooling water temperature, and air conditioner switch signal are sent to the idle rotation speed setting section 22.
is input, a target engine speed is determined according to the cooling water temperature and whether or not the air conditioner is used, and in the duty ratio determining section 23, the actual engine speed detected by the engine speed sensor 12 converges to the target engine speed. The duty ratio is determined in this manner, and a duty signal as a control signal is output. Note that when the vehicle is not in the idle state, the duty ratio is maintained at a predetermined value. It also has a drive transistor 24 as a drive device, and this drive transistor 2
The emitter of No. 4 is connected to the power supply side, and the above duty signal is input to the base. The collector is connected to the solenoid valve 9 by a harness 25 serving as a connecting means and grounded, thereby forming a circuit for controlling the power supply side of the solenoid valve 9. Therefore, as a failure diagnosis control system, the drive transistor 24
monitor the voltage on the collector side of the Further, the duty signal from the duty ratio determination section 23 and the monitor voltage are input to the failure determination section 27, and a failure due to a harness ground fault is determined based on the change in the monitor voltage when the duty is on. If it is determined that there is a failure, the duty ratio of the duty ratio determination section 23 is forcibly set to 0%, and an alarm is displayed with a lamp 28. It also has a failure recovery check section 29 to which a failure determination signal is input, and after determining the failure, the failure recovery check section 29 periodically outputs a duty signal that is turned on for a short period of time based on a diagnostic map or the like.
The failure determination unit 27 checks failure recovery and issues instructions depending on whether or not recovery has occurred. Next, the operation of this control system will be described using the flowchart shown in FIG. First, when the duty signal output from the duty ratio determining section 23 is at a low level, the drive transistor 24 is turned off and the solenoid valve 9 is closed due to de-energization. At this time, the collector side of the drive transistor 24 is grounded and the monitored voltage is zero, and even if the harness 25 is grounded, the monitored voltage will not change.
judgment is canceled. On the other hand, when the duty signal output from the duty ratio determination section 23 is at a high level, the drive transistor 24 is turned on and a current corresponding to the duty ratio flows through the solenoid valve 9. At this time, if the harness 25 is normal, the solenoid valve 9 is opened by energization and the amount of intake air is controlled to flow into the engine body 1 through the bypass passage 8.
Engine speed is controlled. When the harness is normal, a voltage is generated on the collector side of the drive transistor 24, and the monitor voltage is input to the failure determination section 27, which determines that it is normal. When the harness 25 has a ground fault under these conditions, the collector side of the drive transistor 24 is grounded, causing the monitor voltage to drop to zero, and the fault determination unit 27 determines that the harness ground fault is a fault due to such a drop in the monitor voltage. will be carried out. At this time, the solenoid valve 9 is de-energized, returns to its initial state, and takes in the minimum amount of air, thereby preventing the engine from revving up or the like. This state is the process of proceeding from step S1 to step S3 via step S2 in the flowchart of FIG. 3, and the ground fault flag is set. Then, by inputting the failure judgment signal to the duty ratio determination unit 23 and setting the duty ratio to 0%, the drive transistor 24 is forcibly turned off (step S4), so that no excessive current flows through the drive transistor 24. This will prevent its destruction. This failure judgment signal is input to the failure recovery check section 29,
After this, the fault recovery check section 29 performs a check and gives instructions. That is, step S1 of the flowchart
Then, the process proceeds to step S5, and after a predetermined time, a duty signal that is ON for a short period of time is output, and the drive transistor 24 is forcibly turned on (step S6). In this state, the failure determination section 27 again makes a determination (step 37). , and if the monitored voltage is still zero and there is a harness ground fault, the process advances to step S8 and the drive transistor 24 is turned off. On the other hand, if a monitor voltage is generated due to recovery from the ground fault, step S
The process proceeds from step 9 to step 810 to restart control. In this way, even after a harness ground fault has been determined, the diagnosis is periodically confirmed. It goes without saying that the present invention can also be applied to solenoid valves other than those for controlling intake air amount.

【Effect of the invention】

As described above, according to the present invention, in a power supply side control method using a driving transistor of a solenoid valve, it is possible to accurately determine a ground fault in a connecting means such as a harness by monitoring with a control unit and perform a failure diagnosis. When a failure is determined, it can be protected by turning off the transistor. Since the transistor is turned on to check for recovery even after a failure is determined, diagnostic accuracy is improved, and upon recovery, normal control is resumed and engine performance is restored, which is preferable.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of application of the solenoid valve of the present invention, FIG. 2 is a circuit diagram showing an embodiment of a drive transistor protection method, and FIG. 3 is a flowchart of the operation. DESCRIPTION OF SYMBOLS 1... Engine body, 9... Solenoid valve for idle speed control, 20... Control unit, 24... Drive transistor, 26... Monitor part, 27... Failure determination part, 29... ...Failure recovery check department ' Patent applicant: Fuji Heavy Industries Co., Ltd. Agent Patent attorney: Makoto Kobashi, Ukiyo Patent attorney: Susumu Murai Figure 1 Figure 3 Q Bean D

Claims (2)

[Claims] (1) A circuit is configured such that a driving transistor and a power source are connected to one side of the solenoid valve and the other side of the solenoid valve is grounded, and an electronic circuit is configured to control the current of the solenoid valve by a control signal input to the driving transistor. In a control system, a method for protecting a drive transistor of a solenoid valve, characterized in that a failure is determined by monitoring the output side voltage of the drive transistor when the drive transistor is on, and when a failure is determined, the drive transistor is forcibly turned off. (2) After the drive transistor is turned off when determining the failure, the drive transistor is periodically turned on to determine the failure state again, and the drive transistor is maintained in the off state unless the failure is recovered. A method for protecting a drive transistor of a solenoid valve according to claim 1.