JPH03951A - Examining device for sensitivity of oxygen sensor at every cylinder - Google Patents

Abstract

PURPOSE:To surely examine sensitivity of an oxygen sensor at every cylinder by controlling the device to delay an injection beginning timing by a prescribed time when a lean-orienting means is actuated, and controlling it to delay an injection end timing by a prescribed time when a rich-orienting means is actuated. CONSTITUTION:A harness cable 3a connected to a fuel injection valve 1 provided on each cylinder and a control unit 2 are connected through a connector 3b, and an examining device 4 for sensitivity of an oxygen sensor at every cylinder is detachably connected between the cable 3a and the connector 3b. This examining device 4 is made into a working condition when a changeover switch 3c is switched to the chain line position, and the fuel injection valve 1 is driven with a transistor 5 in the device 4. The examining device 4 is selected with a selecting switch 6 to make the cylinder into a rich condition or a lean condition. At selecting the lean side, the injection beginning timing is delayed by a prescribed time, and at selecting the rich side, the injection end timing is delayed by a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a device for investigating the detection sensitivity of exhaust oxygen concentration for each cylinder of an oxygen sensor installed in an exhaust passage collecting section.

<Conventional technology> Conventionally, in an electronically controlled fuel injection system for an internal combustion engine, an electromagnetic fuel injection valve is provided for each cylinder in the intake system of the engine, and the injection rate of these electromagnetic fuel injection valves is calculated based on the engine operating state. There is a device that injects fuel by being actuated by an injection pulse signal that has a pulse width that corresponds to the fuel injection amount and is output in synchronization with engine rotation. (Showa 60
(Refer to Publication No.-23246, etc.).

Here, an oxygen sensor is provided at the collecting part of the exhaust manifold, and based on the oxygen concentration in the exhaust gas detected by the oxygen sensor under predetermined operating conditions, the fuel injection amount is controlled so that the air-fuel ratio approaches the target air-fuel ratio. air-fuel ratio feedback control. Here, the sensitivity of the oxygen sensor differs for each cylinder depending on the mounting position of the oxygen sensor, the shape of the exhaust passage, etc., and the air-fuel ratio may differ depending on the cylinder. It becomes necessary to investigate the sensitivity of each cylinder.

Therefore, as a cylinder-specific sensitivity investigation device for oxygen sensors, we change the fuel injection amount of only that cylinder for each cylinder and examine the detection state of the oxygen sensor at that time. If the change in the detected value is small, the detection sensitivity of the oxygen sensor for that cylinder is high, and if the change in the detected value is small, the detection sensitivity is low, and so on, and the sensitivity of each cylinder is investigated. That is, conventionally, as shown in FIG. 4, the electromagnetic fuel injection valve 6 provided in each cylinder (#1 to #4 cylinder)
In the drive circuit between 1 to 64 and the current control circuit 65, an adjustment resistor 66 is connected in series to the drive circuit of the fuel injection valve 61 of the cylinder whose sensitivity is to be investigated (in the case of the conventional example, the first cylinder), By limiting the current i flowing through the fuel injection valve 61, the opening delay of the fuel injection valve 61 is increased, thereby reducing the injection amount of the cylinder concerned and making the air-fuel ratio lean;
The method used was to investigate the sensitivity of oxygen sensors for each cylinder.

<Problems to be Solved by the Invention> However, in such a conventional oxygen sensor sensitivity investigation device for each cylinder, the fuel injection valve of the cylinder whose sensitivity is to be investigated (in the case of Fig. 4, the first cylinder) By connecting the adjustment resistor 66 in series to the drive circuit 61, the electromagnetic attraction force of the electromagnetic coil counteracts the valve closing force of the spring and delays the rise to a current value i that is sufficient to attract the valve body. It is something that exists. Therefore, in a fuel injection valve using a copper wire coil, a current of about 4 A (ampere) usually flows to open the valve, so even if the current is limited by the series connection of the adjustment resistor 66, It is possible to make the air-fuel ratio of the relevant cylinder lean by delaying the valve. However, for example, in a fuel injection valve using a positive wire coil, the driving current is normally limited to about IA, so if the current is limited by the series connection of the adjustment resistor 66, the electromagnetic coil will not attract the valve body. This makes it impossible to conduct an investigation because no fuel is injected and no combustion occurs.

Furthermore, with conventional oxygen sensor cylinder sensitivity investigation devices, it is only possible to make the air-fuel ratio of a specific cylinder leaner, so it is possible to make the air-fuel ratio of the cylinder richer and investigate the cylinder-specific sensitivity of the oxygen sensor. There is also the problem that if you want to do so, you cannot conduct an investigation because enrichment is not possible.

The present invention was made in view of such conventional circumstances,
When investigating the sensitivity of oxygen sensors by cylinder, by changing the timing of the rise and fall of the drive signal, it is possible to independently make each cylinder leaner or richer, regardless of the type of injection valve. The purpose is to make it possible.

Means for Solving the Problems> For this reason, the present invention improves the exhaust oxygen concentration detection sensitivity of each cylinder of the oxygen sensor installed in the exhaust passage collecting part by changing the fuel injection amount of a specific cylinder from that of other cylinders. The configuration is for investigating a fuel injection valve of an arbitrary cylinder and a drive circuit that outputs a drive signal to the fuel injection valve, and is detachably connected to the fuel injection valve of the fuel injection valve. A first delay circuit is provided to detect the rise of the drive signal and delay the injection start timing for a predetermined period of time, thereby providing a leaner means for making the air-fuel ratio of the cylinder leaner, and detecting the fall of the drive signal, Enriching means for enriching the air-fuel ratio of the cylinder by providing a second delay circuit for delaying the injection end timing by a predetermined period of time; and a selection means for selectively operating the leaner means or the richer means. The structure is as follows.

<Operation> According to the cylinder-specific sensitivity investigation device for oxygen sensors, when the leaner means is activated by the selection means, the first delay circuit detects the rising edge of the drive signal of the fuel injector and determines the injection start timing. Since it is delayed for a predetermined period of time, the fuel injection amount is reduced and the air-fuel ratio of the cylinder becomes lean. On the other hand, when the enriching means is activated by the selection means, the second delay circuit detects the fall of the drive signal of the fuel injection valve and delays the injection end timing by a predetermined period of time, so that the fuel injection amount increases. , the air-fuel ratio of the relevant cylinder becomes richer.

Then, by making a specific cylinder lean or rich as described above, the fuel injection amount of the specific cylinder changes from that of other cylinders, and the exhaust oxygen concentration detection sensitivity of the specific cylinder can be investigated from the output state of the oxygen sensor at that time. .

<Example> An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a drive circuit for a fuel injection valve in the oxygen sensor cylinder sensitivity investigation device of this embodiment.

A harness cable 3a connected to an electromagnetic fuel injection valve 1 provided in each cylinder of the engine and a control unit 2 are normally connected by a connector 3. and,
An oxygen sensor cylinder sensitivity investigation device 4 according to the present invention is detachably connected between the harness cable 3a and the connector 3b. In the connected state, if the changeover switch 3c is closed with a solid line, the fuel injection valve 1 is driven by the transistor 2a of the control unit 2;
When it is closed as indicated by the dashed-dotted line, it is driven by the transistor 5 of the sensitivity investigation device 4.

Further, the sensitivity investigation device 4 can select whether to put the relevant cylinder in a rich state or a lean state by using a selection switch 6. That is, this selection switch 6 corresponds to selection means.

First, the driving of the fuel injection valve 1 by the sensitivity investigation device 4 will be described in the case where the selection switch 6 is switched to the lean side as shown by the solid line.

First, the reference voltage obtained by dividing the power supply voltage VB by a resistor 8.9 is input to the terminal 10 of the comparator 7, and the output of the control unit 2, which is connected to the power supply voltage 8 via the resistor 21, is input to the terminal. be done.

When the fuel injection valve 1 is open, the transistor 2a is turned on, and the input level at one terminal of the comparator 7 is at the L level, and when the fuel injection valve is closed, the transistor 2a is turned off, and the input level is at the H level. As a result, the output of the control unit 2 is inverted by the comparator 7, and an H level signal is output when the fuel injection valve 1 is open, and an L level signal is output when the fuel injection valve 1 is closed.

Therefore, when a drive signal for driving the fuel injection valve 1 to open is output from the control unit 2, the output voltage (1) of the comparator 7 gradually charges the capacitor 11 through the adjustment resistor 10. Then, the drive signal for the fuel injection valve 1 is turned OFF, and the output voltage V7 of the comparator 7 is
When the voltage also goes to L level, the capacitor 11 is rapidly discharged through the diode 12. Therefore, as shown in FIG. 2, the charging voltage Vll is input to the comparator 13 and compared with the specified voltage Vkl, and the output voltage Vll of the comparator 13 is applied to the base of the transistor 50. Here, the time for charging the capacitor 11 described above is slow due to the provision of the adjustment resistor 10, and as a result, the output voltage Vll from the comparator 13 is delayed by a delay time t, and the fuel injector 1 is The valve opening is delayed from the opening timing of the fuel injection valve (not shown) provided in the cylinder.

That is, the adjustment resistor 10. Capacitor 11. diode 12
and comparator 13 form a first delay circuit.

Furthermore, since the capacitor 11 is rapidly discharged when the drive signal for the fuel injector 1 falls, the timing at which the fuel injector 1 closes is between the other cylinders and the road. It becomes possible to reduce the fuel injection amount of the cylinder in which the engine is provided, thereby achieving a lean state. Note that resistors 14 and 15 are voltage dividing resistors for obtaining a reference voltage.

Next, the driving of the fuel injector l by the sensitivity investigating device 4 will be described in the case where the selection switch 6 is switched to the rich side as shown by the dotted line.

First, a drive signal of L level when fuel injection valve 1 is open and H level when it is closed is inverted by comparator 7, and a signal of H level when fuel injection valve 1 is closed and L level when it is closed. The output is the same as described above.

Therefore, while the fuel injection valve 1 is open, the output voltage of the comparator 7 is manually applied to the comparator 19, and
Capacitor 17 is rapidly charged through diode 16. Then, when the drive signal for the fuel injection valve 1 falls and the output voltage v7 of the comparator 7 also reaches the L level, the capacitor 17 is discharged through the adjustment resistor 18. Therefore, as shown in FIG. 3, the discharge voltage Vll+ is input to the comparator 13 and compared with the specified voltage ■3□.
The output voltage V+q of the comparator 19 is applied to the base of the transistor 5. Here, since the capacitor 17 described above takes time to discharge, the fuel injection valve 1 is opened for a delay time t2 longer than the driving time of the fuel injection valves (not shown) provided in other cylinders. Become. That is, diode 16. Capacitor 17. A second delay circuit is formed by the adjustment resistor 18 and the comparator 19. on the other hand,
Since the capacitor 17 is charged instantaneously, the valve opening timing is between the other cylinders and the road.

Therefore, it is possible to increase the amount of fuel injected into the cylinder in which the fuel injection valve 1 is provided, thereby achieving a rich state.

In this way, by using the cylinder-specific sensitivity investigation device 4 of the oxygen sensor shown in this embodiment, the air-fuel ratio can be detected through the detection of the opening characteristics of the fuel injection valve provided in the cylinder and the oxygen concentration in the exhaust gas. When investigating the correspondence with the sensitivity of the oxygen sensor,
Regardless of the type of electromagnetic fuel injection valve, by changing the timing of the rise and fall of the drive signal, it is possible to independently make the air-fuel ratio of a specific cylinder leaner or richer for each cylinder. .

Therefore, during the development stage of an engine in which an oxygen sensor is provided at the gathering part of the exhaust manifold and air-fuel ratio feedback control is performed using the oxygen sensor, various It is easy to investigate deviations in air-fuel ratio between cylinders due to differences in the sensitivity of oxygen sensors between cylinders. In addition, even if a fuel injector is clogged in the market, only the cylinder in which the fuel injector to be checked is installed is enriched using the cylinder-by-cylinder sensitivity investigation device 4 of the oxygen sensor, and the cylinder is enriched according to the settings. By detecting whether or not the fuel injection valve of the cylinder is clogged, it is easy to check which cylinder's fuel injection valve is clogged, which also has the effect of making maintenance easier.

Further, in this embodiment, the harness cable 3a and the connector 3
Since the cylinder sensitivity investigation device 4 is connected between the harness cable 3a and the harness cable 3a, it can be easily connected without cutting the harness cable 3a. .

<Effects of the Invention> As explained above, according to the present invention, when the lean means is activated by the selection means regardless of the type of fuel injector, the first delay circuit delays the injection start timing by a predetermined period of time. to make the air-fuel ratio of the cylinder lean, and on the other hand, when the selection means operates the enrichment means,
Since the second delay circuit delays the injection end timing by a predetermined period of time and enriches the air-fuel ratio of the relevant cylinder, it is possible to reliably investigate the cylinder-by-cylinder sensitivity of the oxygen sensor, and also to make the cylinder-by-cylinder sensitivity investigation Since the investigation device can be freely connected and detached, maintenance costs can also be reduced.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the drive circuit of the fuel injector in the oxygen sensor cylinder sensitivity investigation device according to the present invention, and Fig. 2 shows the characteristics of the drive voltage when lean is applied in the same embodiment. 3 is a characteristic diagram of the drive voltage when enriching in the same embodiment as above, and FIG. 4 is a circuit diagram showing a drive circuit of a fuel injection valve in a conventional sensitivity investigation device for each cylinder. 1... Electromagnetic fuel injection valve 2... Control unit 4... Sensitivity investigation device 7.13.19.
...Comparator io, is...Adjustment resistance
11.17...Capacitor 12.16...Diode Patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima〉〉

Claims (1)

[Claims] By changing the fuel injection amount of a specific cylinder from that of other cylinders,
A device for investigating the detection sensitivity of oxygen concentration in exhaust gas for each cylinder of an oxygen sensor installed in an exhaust passage gathering part, the device includes a fuel injection valve of an arbitrary cylinder and a drive circuit that outputs a drive signal to the fuel injection valve. is detachably connected between the fuel injection valve and detects the rise of the drive signal from the drive signal of the fuel injection valve,
A first delay circuit that delays the injection start timing by a predetermined period of time is provided to lean the air-fuel ratio of the cylinder concerned, and a fall of the drive signal is detected to delay the injection end timing by the predetermined period of time. Second
A cylinder of an oxygen sensor characterized by being provided with an enriching means for enriching the air-fuel ratio of the cylinder by providing a delay circuit, and a selection means for selectively operating the leaner means or the richer means. Another sensitivity investigation device.