JPH0318676Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a fuel cut device for an internal combustion engine.
Particularly suitable for use in automobile engines equipped with electronically controlled fuel injection devices, when the engine rotation speed is equal to or higher than the first judgment value and the throttle fully closed signal is on, fuel cut during deceleration is performed. At the same time, the fuel cut is continued until the engine speed reaches a second judgment value that is smaller than the first judgment value by the amount of hysteresis, and further, when the throttle fully closed signal is off, the judgment An internal combustion engine that prevents fuel from being cut off again even if the throttle fully closed signal is turned on again within the hysteresis by raising the value to a third judgment value higher than the normal engine speed. This invention relates to improvements to fuel cut devices.

[Conventional technology]

Internal combustion engines, especially automobile engines that use electronically controlled fuel injection systems, improve fuel efficiency by reducing hydrocarbons and carbon monoxide, which are unburned components in exhaust gas, and by prohibiting unnecessary fuel injection. For the purpose of improving engine performance, it is common to perform a so-called fuel cut in which fuel injection is stopped depending on the engine operating state, for example, during deceleration when the throttle valve is fully closed.

A conventional fuel cut circuit for cutting fuel during deceleration, for example, as shown in FIG. Frequency-voltage converter (hereinafter referred to as F-V converter) for converting into a voltage proportional to rotational speed NE
10 and the output voltage of the F-V converter 10 is compared with the reference voltage VR corresponding to the first judgment value N1, and F-
A voltage comparator 12 generates a "1" level output when the output voltage of the V converter 10 becomes equal to or higher than the reference voltage VR, and a voltage comparator 12 generates an output of "1" level when the output voltage of the voltage comparator 12 becomes "1" level. By feeding back to the input side of the voltage comparator 12 and increasing the output voltage of the F-V converter 10, the engine rotational speed is temporarily increased.
When NE exceeds the first judgment value N1, a hysteresis resistor 14 is used to make the judgment value relatively lower than the first judgment value N1 by the amount of hysteresis NH.
The logical product of the output of the voltage comparator 12 and the throttle fully closed signal I output from the idle switch 15 that is turned on when the throttle valve is at the idle opening is set as the fuel cut control output O by electronic control (not shown). Outputs to the fuel injection device to stop fuel injection when the conditions are met
It is composed of an AND circuit 16.

According to such a fuel cut circuit, the engine rotational speed NE and the throttle fully closed signal I during deceleration
As shown in Fig. 2, the fuel cut control output O changes according to the changing state of The fuel cut control output O is turned on to perform fuel cut during deceleration. At this time, the "1" level signal of the voltage comparator 12 is fed back to the input side of the voltage comparator 12 via the hysteresis resistor 14, and the judgment value is smaller than the first judgment value N1 by the hysteresis NH. This is the second judgment value (N1-NH). Next, when the throttle fully closed signal I turns off at time T1, the fuel cut control output O also turns off, and no fuel cut is performed. however,
When the throttle fully closed signal I turns on again at time T2, the determination value has decreased by the hysteresis NH, so the fuel cut control output O turns on.
The problem is that fuel cut is performed again until time T3 when the engine speed NE is lower than the first judgment value N1 by the amount of hysteresis NH, resulting in frequent fuel cut and impairing engine operating performance. had.

A fuel cut circuit as shown in FIG. 3 has been proposed as a fuel cut circuit for preventing fuel cut again when the throttle valve fully closed signal I is turned on again within the hysteresis as described above. There is. This fuel cut circuit includes an F-V converter 10, a voltage comparator 12, a hysteresis resistor 14, and an AND circuit 16, similar to the conventional example shown in FIG. In the cut circuit,
The hysteresis resistor 14 is connected to the voltage comparator 12.
It is connected to the output side of AND16, not to the output side of .

For this reason, the engine rotational speed NE during deceleration, the throttle fully closed signal I, and the fuel cut control output O
The relationship is as shown in Fig. 4. When the throttle fully closed signal I turns off at time T1, the output of the AND circuit 16 goes to the "0" level, so the hysteresis NH component is canceled and the engine rotational speed NE
Even after time T2 when the throttle fully closed signal I is turned on again with N1-NH higher than N1-NH, fuel cut is not performed again.

Further, as shown in FIG. 5, another fuel cut circuit that prevents the fuel from being cut again when the throttle fully closed signal I is turned on again within the hysteresis is as shown in FIG. In a fuel cut circuit having an F-V converter 10, a voltage comparator 12, a hysteresis resistor 14, and an AND circuit 16, similar to the conventional example shown in FIG. , throttle fully closed signal I
A reference voltage changing circuit 18 is added for raising the judgment value to a third judgment value N2 which is higher than the normal engine rotational speed when is off.

In the fuel cut circuit shown in FIG.
The relationship between the engine rotational speed NE during deceleration, the throttle fully closed signal I, and the fuel cut control output O is determined by the sixth
As shown in the figure, after time T1 when the throttle fully closed signal I turns off, the reference voltage VR of the voltage comparator 12 is switched, and the throttle fully closed signal I
Until time T2 when is turned on again, the judgment value is raised to the third judgment value N2, which is higher than the normal engine speed including the hysteresis NH.
Even if the output of the voltage comparator 12 is reliably at the "0" level, the hysteresis is canceled, and the throttle fully closed signal I is turned on again at time T2, the fuel will not be cut off again. Usually, the third judgment value N2 is 4 to 5 of the first judgment value N1.
The engine rotational speed is double the value, which is impossible in practice, and the hysteresis is reliably canceled between times T1 and T2.
Therefore, in the fuel cut shown in FIG. 5, the third judgment value N2 is not finely adjusted, and the set value itself only needs to be a certain value or more.

On the other hand, in internal combustion engines, fuel is not only cut when decelerating, but also when the engine speed exceeds a predetermined value in order to prevent engine damage due to engine overrun. . Conventionally, as a fuel cut circuit for preventing engine overrun, in addition to the fuel cut circuit during deceleration as shown in Figure 1, Figure 3, or Figure 5, a dedicated engine It is necessary to provide a fuel cut circuit for overrun prevention, which has the problem of complicating the control circuit and increasing costs.

Also, the fuel cut circuit during deceleration is shown in Figure 1 above.
Instead of using the frequency-voltage conversion method (hereinafter referred to as F-V conversion method) as shown in Fig. 3 or Fig. 5, the so-called ignition cycle detects the engine rotation speed from the ignition cycle. In the case of a comparison method, the accuracy of fuel cut during deceleration is extremely high and there is little variation in fuel cut rotation speed, but the fuel cut circuit for additional engine overrun prevention generally has a high frequency −
Since the voltage conversion method converts the primary ignition signal into voltage to obtain the engine rotation speed signal, there is a delay element, and the problem is that the rotation speed at which fuel is cut is actually too high than the judgment value. It had

The present invention was developed to eliminate the above-mentioned drawbacks of the conventional technology, and by slightly modifying the fuel cut circuit during deceleration, engine overrun can be prevented. Moreover, it is an object of the present invention to provide a fuel cut device for an internal combustion engine that can easily and accurately cut fuel.

[Means to solve the problem]

The present invention includes means for detecting the engine rotation speed, means for detecting the fully closed state of the throttle, means for cutting off the fuel supply, and executing the fuel supply cut means when the engine rotation speed is equal to or higher than a determination value. When the throttle is fully closed and fuel cut is not in progress, the judgment value is set as the first judgment value suitable for starting fuel cut during deceleration, and when the throttle is fully closed and fuel cut is not in progress, When the cut is being executed, the judgment value is set as the second judgment value which is smaller than the first judgment value by the amount of hysteresis, and when the throttle is not fully closed, the judgment value is set as the first judgment value. The above-mentioned object is achieved by providing a determination value determining means that sets a third determination value suitable for preventing engine overrun, which is a larger value than the third determination value.

〔Example〕

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

The first embodiment of the present invention, as shown in FIG. 7, includes an F-V converter 10, a voltage comparator 12, and a hysteresis resistor 14, which are similar to the conventional example shown in FIG. AND circuit 16 and reference voltage change circuit 1
8, the reference voltage changing circuit 18 is connected to a transistor Tr which is turned on and off in response to a throttle fully closed signal I output from an idle switch 15 which is input via a resistor R1. When it is off, i.e.
When the throttle fully closed signal I is on, the standard corresponding to the first judgment value N1 suitable for fuel cut during deceleration is obtained by dividing the voltage of the battery 20 by voltage dividing resistors R4 and R5. When the voltage VR is generated and the transistor Tr is turned on by the base leakage resistor R2, that is,
When the throttle fully closed signal I is turned off, the voltage of the battery 20 is divided by the combined resistance of the voltage dividing resistors R3 and R4 and the voltage dividing resistor R5, which is suitable for preventing engine overrun. The configuration is configured to generate a reference voltage VR corresponding to the third judgment value N2, and also performs fuel cut control at the time of overrun by taking the AND of the output of the voltage comparator 12 and the output of the transistor Tr. The AND circuit 22 that outputs the output O2, the logical sum of the fuel cut control output O2 at the time of overrun of the output of the AND circuit 22, and the fuel cut control output O1 at the time of deceleration of the output of the AND circuit 16 are used for final fuel cut control. An OR circuit 24 which outputs as an output O is added.

The action will be explained below.

First, when the throttle fully closed signal I is on,
A voltage is applied to the base of the transistor Tr by the resistor R1, and the transistor Tr is turned off.
Depending on the voltage division ratio between the voltage dividing resistor R4 and the voltage dividing resistor R5, the reference voltage VR is N1 corresponding to the first judgment value.
becomes. On the other hand, when the throttle fully closed signal I is off, this transistor Tr is turned on by the base leak resistor R2, and the voltage division ratio of the combined resistance of the voltage dividing resistors R3 and R4 and the voltage dividing resistor R5 is The reference voltage VR of the voltage comparator 12 is determined by
is set to N2 corresponding to the third judgment value, which is higher than when the transistor Tr is off.

Further, when the output of the voltage comparator 12 is "1", the engine rotation speed NE inputted to the positive input of the voltage comparator 12 via the resistor 14
The hysteresis amount NH is added to. The voltage comparator 12 has a reference voltage input to a negative input.
This is to compare VR and the engine rotation speed NE input to the positive input. Therefore, when the hysteresis amount NH is added to the positive input, this voltage comparator 12
This is a comparison between NE and VR-NH.

Hereinafter, the effects will be explained for each of the three types of determination values in total.

In this example, the first judgment value N1 is
This is a judgment value suitable for starting fuel cut during deceleration. That is, when the throttle fully closed signal I is on, the reference voltage VR of the voltage comparator 12 is set to the first voltage suitable for fuel cut during deceleration, which is determined by the ratio of the resistance values of the voltage dividing resistors R4 and R5. This is the reference voltage corresponding to the judgment value N1. In addition, before the start of fuel cut during deceleration, the output of the voltage comparator 12 is "0", and the "1" output of the voltage comparator 12 is added to the engine speed NE by the resistor 14 (the hysteresis amount is added to NH). equivalent) is not available. Therefore, in this case, if the condition that the engine rotational speed NE is greater than the first determination value N1 is further established, fuel cut-off during deceleration is performed as in the conventional case.

In this embodiment, the second judgment value N1−
NH is a value smaller than the first judgment value N1 described above by the amount of hysteresis (NH). That is, the throttle fully closed signal I is on, and the F-V converter 1
Once the engine rotational speed NE, which is the output of 0, is equal to or higher than the first judgment value N1, the voltage comparator 12
After the output of the voltage comparator 12 reaches the "1" level and the fuel cut is once performed, the determination by the voltage comparator 12 is made according to the second determination value N1-NH. It will be done. Once the output of the voltage comparator 12 reaches the "1" level, this "1" level output is input via the resistor 14 to one input of the voltage comparator 12 to which the engine speed NE is input. be done. Therefore, the engine rotational speed NE is first added to the "1" level signal (which corresponds to hysteresis) input via the resistor 14, and then added to the reference voltage determined by the resistance ratio of the voltage dividing resistors R4 and R5. It is compared to VR. As a result, the engine rotational speed NE at this time becomes the second judgment value N1 - NH, which is a value smaller than the first judgment value N1 by hysteresis (the "1" level input via the resistor 14). will be compared. Therefore, in this case, if the condition that the engine rotational speed NE is smaller than the second determination value N1-NH is further established, the fuel cut is stopped and the fuel supply is restarted.

In this example, the third judgment value N2 is
This determination value is larger than the first determination value N1 and is suitable for preventing engine overrun.
In normal operating conditions other than idling and deceleration when the idle switch 15 is off, the engine rotational speed NE is
When the value exceeds the third judgment value N2 suitable for preventing engine overrun, which is determined by the ratio of the resistance values of is ANDed with the OFF state, and a fuel cut control output O2 for preventing engine overrun is outputted via the OR circuit 24, and fuel cut is performed in the event of an engine overrun.

In addition, in the present invention, when the throttle is fully closed and fuel cut is being executed, the engine rotation speed NE is determined by determining whether the following inequality is true.
is compared with the second judgment value N1-NH, and the fuel supply is restarted (fuel cut is stopped).

NE＜(N1−NH)……(1a) That is, fuel cut continues while the following equation holds true.

NE>(N1−NH) ...(1b) However, as is done in the voltage comparator 12 of this embodiment, the term NH on the right side is moved to the left side, and the above equation (1a) is changed to the following equation. It goes without saying that even if the equation (2a) is used and the above equation (1b) is replaced by the following equation (2b), the result is exactly the same. In this embodiment, a hysteresis amount NH is added by a resistor 14 to the engine rotational speed NE input to the positive input of the voltage comparator 12.

(NE+NH)<N1...(2a) (NE+NH)>N1...(2b) In this example, engine rotational speed NE, throttle fully closed signal I, and fuel cut control output O
An example of the relationship is shown in FIG.

In the first embodiment, the present invention was applied to an F-V conversion type fuel cut device in which the engine rotational speed NE is determined based on the output of the F-V converter. Engine rotation signal G
This is a so-called ignition cycle comparison using a cycle comparator that measures the signal interval of the ignition primary signal Ig, which is a substitute signal for The present invention can be similarly applied to a type of fuel cut device.

FIG. 9 shows a second embodiment of the present invention applied to such a fuel cut device using the ignition cycle comparison method.

This embodiment is a fuel cut device for a 6-cylinder automobile engine that has a voltage comparator 12, AND circuits 16, 22, a reference voltage change circuit 18, and an OR circuit 24, similar to the first embodiment. , a frequency dividing circuit 30 for dividing the frequency of the primary ignition signal Ig by 1/3 to obtain a signal C for every engine revolution (hereinafter referred to as a one revolution signal) having a pulse width corresponding to the ignition cycle. The one-rotation signal C output from the frequency dividing circuit 30 is integrated within one cycle of the primary ignition signal Ig to obtain a voltage signal S inversely proportional to the engine rotational speed NE, which is then applied to the inverting input of the voltage comparator 12. The output of the integration circuit 32 at the rising edge of the one revolution signal C (see FIG. 10) is determined according to the output of the voltage comparator 12 and the output of the frequency divider circuit 30. When the voltage S of the reference voltage changing circuit 18 has not reached the reference voltage VR of the output of the reference voltage changing circuit 18, the output Q is generated and the AND circuits 16 and 3
2 is provided with a flip-flop circuit 34 which outputs a fuel cut control output.

In this embodiment, since the ignition cycle comparison method is used, the voltage signal S of the output of the integrating circuit 32, which is input to the voltage comparator 12 according to the engine rotation speed NE, becomes low level when the engine rotates at high speed.
Reference voltage when throttle fully closed signal I is on
This embodiment differs from the first embodiment in that the VR can be lifted up. The other points are almost the same as those of the first embodiment, so the explanation will be omitted.

FIG. 10 shows an example of the relationship among the primary ignition signal Ig, the one-rotation signal C output from the frequency dividing circuit 30, the reference voltage VR, the voltage signal S output from the integrating circuit 32, and the output Q from the flip-flop circuit 34 in this embodiment. Shown below.

In this example, since the ignition cycle comparison method is used, there is little variation in the fuel cut rotation speed.
Highly accurate fuel cutting is possible. In addition, the delay in converting the ignition signal to voltage is extremely small, making it possible to cut fuel with a quick response, and even during racing, etc., where an extremely quick response is required, the rotational speed at which the fuel is actually cut is too high. Never.

[Effect of idea]

As explained above, according to the present invention, by simply adding a few circuits to the conventional fuel cut circuit for deceleration, so that fuel cut is performed regardless of the presence or absence of the throttle fully closed signal, Fuel can be cut. Further, by employing the ignition cycle comparison method, there are excellent effects such as less time delay until fuel cut and highly accurate fuel cut.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an example of a conventional fuel cut circuit for deceleration, and Fig. 2 shows the engine rotational speed and throttle fully closed signal during deceleration in the conventional example shown in Fig. 1. A diagram showing an example of the relationship between fuel cut control outputs, FIG. 3 is a block diagram showing the configuration of another example of the conventional fuel cut circuit for deceleration, and FIG. FIG. 5 is a diagram showing an example of the relationship between the engine rotational speed during deceleration, the throttle fully closed signal, and the fuel cut control output. FIG. 5 is a block diagram showing still another configuration of the conventional fuel cut circuit for deceleration. 6 is a diagram showing an example of the relationship between the engine rotational speed during deceleration, the throttle fully closed signal, and the fuel cut control output in the conventional example shown in FIG. 5, and FIG. FIG. 8 is a circuit diagram showing the configuration of a first embodiment of the fuel cut device for an internal combustion engine, and shows the engine rotational speed, throttle fully closed signal, and fuel during engine overline and deceleration in the first embodiment. Diagram showing an example of the relationship between cut control outputs, No. 9
FIG. 10 is a circuit diagram showing the configuration of a second embodiment of the fuel cut device for an internal combustion engine according to the present invention, and FIG. , a diagram showing an example of the relationship among a reference voltage, a voltage signal of an output of an integrating circuit, and an output of a flip-flop circuit. 10... Frequency-voltage converter, 12... Voltage comparator, 14... Hysteresis resistor, 15... Idle switch, 16, 22... AND circuit, 1
8...Reference voltage change circuit, 20...Battery, 2
4...OR circuit, 30...frequency divider circuit, 32...integrator circuit, 34...flip-flop circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] Means for detecting the engine rotation speed; means for detecting the fully closed state of the throttle; means for cutting off the fuel supply; When the throttle is fully closed and the fuel cut is not in progress, the determination value is set as a first determination value suitable for starting fuel cut during deceleration; When the fuel cut is being executed, the judgment value is set as the second judgment value which is smaller than the first judgment value by the amount of hysteresis, and when the throttle is not fully closed, the judgment value is set to A fuel cut device for an internal combustion engine, comprising: determination value determining means for determining a third determination value suitable for preventing engine overrun, which is a larger value than the first determination value.