JPH08291877A - Failure diagnosing device for solenoid valve - Google Patents

Abstract

PURPOSE: To detect a failure such as seizure of a plunger by detecting supply current to a solenoid valve and a change in current in the solenoid valve driving time at the same time and determining a normal condition of the solenoid valve if the detected change in current is negative. CONSTITUTION: In application to a vent shut valve 10 serving as a normally open type solenoid valve, which is arranged in the middle of a passage through which a canister 8 absorbing evaporative fuel in a fuel tank is opened to the atmosphere, in the vent shut valve 10, a valve element 24 is normally positioned in the upper side, in other words, in a valve open condition by means of energizing force of a spring 25. When current flows to a coil 21, a plunger 22 is driven downward against the spring 25, and the valve element 24 is brought into pressure contact with a seal valve seat via a valve rod 23 integrated with the plunger 22 so as to close the passage. In this case, a change in current during solenoid valve driving time is detected by detecting the current flowing in the coil 21, and if the detected change in current is negative, it is judged that the vent shut valve 10 is in a normal condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid valve failure diagnostic device.

[0002]

2. Description of the Related Art For example, in an evaporated fuel processing apparatus for temporarily storing evaporated fuel generated in a fuel tank of a vehicle driven by an internal combustion engine and appropriately supplying it to an intake system of an engine, an electronic control unit (ECU) is used. A solenoid valve controlled by a solenoid valve is used, and a method of determining disconnection or short circuit of a coil of the solenoid valve by an ECU has been conventionally known.

[0003]

However, in the above-mentioned conventional method, when the coil is normal and the sticking of the plunger occurs, the failure cannot be detected.

Further, in order to detect such a failure,
For example, a method of adding a pressure sensor or a flow rate sensor and performing failure diagnosis based on the control signal of the solenoid valve and the change of the controlled object can be considered, but there is a problem that the number of parts increases and the cost increases.

The present invention has been made in view of this point, and an object thereof is to provide a failure diagnosis device for a solenoid valve capable of surely detecting a failure such as sticking of a plunger by a simple method.

[0006]

In order to achieve the above object, the present invention relates to a solenoid valve failure diagnosing device having a plunger, in which current detecting means for detecting a current supplied to the solenoid valve and the current detecting means are provided. Current change detection means for detecting a change in current when the solenoid valve is driven by output, and determination means for determining that the solenoid valve is normal when a negative change in current is detected by the current change detection means are provided. It was done like this.

[0007]

[Operation] It has been experimentally confirmed that a negative change in the drive current of the solenoid valve is detected when the plunger operates normally without sticking, and when the negative change is detected, it is normal. Is determined, and if no negative change is detected, it is determined to be a failure.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an evaporated fuel processing apparatus according to an embodiment of the present invention, in which a fuel tank 1 is connected to a canister 8 having an adsorbent for evaporated fuel via an evaporated fuel passage 2. Has been done. A pressure sensor 3, a bypass valve 4, a two-way valve 5, a one-way valve 6 and a one-way solenoid valve 7 are provided in the middle of the fuel vapor passage 2. The canister 8 has a passage 9 that communicates with the atmosphere, and a vent shut valve 10 is provided in the middle of the passage 9. The canister 8 is connected to an intake system 12 of the engine via a purge passage 11.

The pressure sensor 3 is connected to an electronic control unit (hereinafter referred to as "ECU") 14, and its detection signal is supplied to the ECU 14. Bypass valve 4,
The one-way solenoid valve 7, the vent shut valve 10, and the purge control valve 13 are solenoid valves, and their operations are controlled by the ECU 14. The bypass valve 4 is normally in a closed state, and is opened by a drive signal from the ECU 14 when necessary. Further, the vent shut valve 10 is normally in an open state, and is closed by a drive signal from the ECU 14 when necessary. The purge control valve 13 is the ECU 1
4 controls the flow rate of the mixture of evaporated fuel and air purged from the canister 8 by duty control.

The ECU 14 is a C that performs various arithmetic processes.
The CPU includes a memory for storing programs executed by the CPU and CPU and operation results, an input / output circuit including an A / D converter, a D / A converter, etc., and controls the drive of the solenoid valve described above, and will be described later. Failure detection of the solenoid valve.

In the apparatus shown in FIG. 1, the evaporated fuel generated in the fuel tank 1 is stored in the canister 8 and is appropriately supplied to the engine intake system 12.

FIG. 2 is a sectional view showing the structure of the vent shut valve 10. The vent shut valve 10 includes a coil 21.
And the valve shaft 23 and the plunger 22 fixed to the valve shaft 23.
And a spring 25 for urging the valve body 24 in the valve opening direction (upward direction in the drawing).

The vent shut valve 10 is a normally open solenoid valve, and is in the open state as shown when the coil 10 is not energized. And the coil 10
When a current is supplied to, the plunger 22, the valve shaft 23, and the valve body 24 move downward in the figure, and the valve is closed.

FIG. 3 is a diagram showing in detail the electrically connected state of the vent shut valve 10. The coil 21 has one end connected to the positive electrode of a battery (not shown) and the other end connected to a current detection resistor. It is connected to the collector of the transistor 32 via 31. The base of the transistor 32 is the ECU 1
4 and the emitter is grounded. Further, both ends of the resistor 31 are connected to the ECU 14. The resistor 31 and the transistor 32 are not shown in FIG. The other solenoid valves 4, 7, 13 are also electrically connected in the same manner as the vent shut valve 10.

According to this configuration, when the ECU 14 supplies the low level signal to the transistor 32, the transistor 32 is in the off state, the coil 21 is not supplied with current, and the vent shut valve 10 is opened. It is in a valve state.
On the other hand, when a high level signal is supplied, the transistor 32 is turned on to supply current to the coil 21, and the vent shut valve 10 is closed. At this time, the ECU 14 sets the resistance 3
Current value IA supplied to coil 21 from the voltage across 1
Detect CT.

FIG. 4 is a diagram showing the time change (waveform) of the current value IACT, which shows the transistor 32 at time t0.
This is the case when is turned on.

FIG. 3A shows a waveform when the plunger 22 does not move due to sticking or the like, and the current value IAC
T monotonically increases with a delay due to the inductance of the coil 21. On the other hand, FIG. 6B shows a waveform when the plunger 22 moves normally, and the current value IAC
T tends to decrease once in the process of increasing and then increase again. This is because the magnetic flux near the coil 21 changes as the plunger 22 moves. Therefore,
Depending on the presence or absence of this reduced portion, it is possible to detect a failure such as sticking of the plunger.

FIGS. 5 (a) and 5 (b) are diagrams showing changes in the amount of change ΔIACT of the current value IACT per unit time, which correspond to the waveforms of FIGS. 4 (a) and 4 (b), respectively. As is clear from this figure, when there is a portion where the current waveform decreases, the change amount ΔIACT becomes a negative value. Therefore, in this embodiment, when the ΔIACT value becomes a negative value, the solenoid valve is regarded as normal. I am trying to judge. In other words, when the ΔIACT value does not become a negative value, it is determined that a failure such as sticking of the plunger has occurred.

As described above, in this embodiment, when the current supply to the coil of the solenoid valve is started, the current IAC
When the change amount ΔIACT of T has a negative value, it is determined to be normal, and when the change amount ΔIACT does not have a negative value, it is determined to be a failure. Therefore, it is possible to reliably detect a failure such as sticking of the plunger by a simple method. it can.

Actually, as shown in Table 1, it is desirable to make the determination based on the results of the two energizations. That is, in the case of a normally open type (normally open type) solenoid valve such as the vent shut valve 10, it is determined as normal when a negative change in the current value is detected twice, and a negative change is detected. When it is not detected at both times, it is determined that the valve is stuck in the open or closed state, and the first negative change is detected,
If it is not detected the second time, it is determined that the valve is closed.

Further, in a normally closed type (normally closed type) solenoid valve such as the bypass valve 4,
If two negative changes in the current value are detected, it is determined to be normal, and if neither negative change is detected, it is determined that the valve is stuck in the open or closed state, and the first negative When the change in is detected and is not detected for the second time, it is determined that the valve open state is fixed.

[0023]

[Table 1] FIG. 6 shows the duty ratio D of the drive signal for the purge control valve 13.
and a flow rate Q of the air-fuel mixture passing through the purge control valve 13 and a current waveform of the coil at each point A to E. FIG. It shows that linearity can be obtained. As can be seen from this figure, in the range where the linearity is good, there is a portion where the current waveform decreases and there is a moment when the current value IACT becomes zero. Therefore, it is possible to determine the secular change in the range with good linearity by detecting the duty value range in which the current waveform has a decreasing portion and the moment when IACT = 0. , D
By correcting the duty value, it is possible to always use a range with good linearity.

[0024]

As described in detail above, according to the present invention, when a negative change in the drive current of the solenoid valve is detected, it is determined to be normal, and when no negative change is detected, it is determined to be a failure. Therefore, it is possible to reliably detect a failure such as sticking of the plunger with a simple configuration.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an evaporated fuel processing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a solenoid valve.

FIG. 3 is a diagram showing a drive circuit of a solenoid valve.

FIG. 4 is a diagram showing a current waveform of a coil of a solenoid valve.

FIG. 5 is a diagram showing changes in the amount of change in coil current of a solenoid valve.

FIG. 6 is a diagram showing the relationship between the duty ratio of the duty control valve and the air-fuel mixture flow rate.

[Explanation of symbols]

 4 By-pass valve 7 One-way solenoid valve 10 Vent shut valve 13 Purge control valve 21 Coil 22 Plunger 23 Valve shaft 24 Valve body 31 Current detection resistance

Claims (2)

[Claims] 1. A failure diagnosis device for a solenoid valve having a plunger, wherein a current detecting means for detecting a current supplied to the solenoid valve, and an output of the current detecting means for detecting a change in current when the solenoid valve is driven. A solenoid valve failure diagnosis device comprising: a current change detection means; and a determination means for determining that the solenoid valve is normal when a negative change in current is detected by the current change detection means. 2. The failure diagnosis device for a solenoid valve according to claim 1, wherein the solenoid valve is used in a vehicle or an internal combustion engine.