JPH0247257Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an energization control device for an electric heater for promoting atomization of fuel when the machine is cold.

<Prior Art> Conventionally, for example, in an internal combustion engine equipped with an electronically controlled fuel injection device of a so-called single point injection (hereinafter referred to as SPI) system in which one fuel injection valve is provided upstream of a throttle valve, An electric heater (PTC heater) using a characteristic thermistor (PTC) is installed downstream of the throttle valve, and after turning on the key switch, the engine temperature (represented by the cooling water temperature) reaches a predetermined value. There is a system in which the electric heater is energized to generate heat and promote atomization of the fuel (see Utility Model Application No. 191368/1984).

<Problems to be solved by the invention> However, in the conventional fuel atomization heater energization control device described above, the energization to the electric heater for fuel atomization is turned off when the engine temperature reaches a predetermined temperature.
(see Fig. 4), there was a problem in that the air-fuel ratio temporarily became lean during this OFF period, deteriorating drivability.

That is, when the power supply to the electric heater is turned off from ON, the electric heater stops generating heat and is cooled by the fuel, so that its temperature rapidly decreases as shown in FIG. 4. For this reason, a large amount of fuel adheres to the electric heater, and this adhered fuel is not supplied to the engine, causing the air-fuel ratio to become lean. The electric heater is
When the switch is off, a certain amount of fuel adheres to it, but when it changes from on to off, this amount of adhering fuel increases at once, which causes the above-mentioned problem.

The present invention was developed in view of the above-mentioned conventional problems, and its purpose is to prevent the air-fuel ratio from becoming lean by avoiding the sudden adhesion of fuel when the electric heater for fuel atomization is turned off. shall be.

<Means for solving the problem> Therefore, in the present invention, as shown in FIG. 1, an electric heater is provided in the engine intake passage on the downstream side of the fuel supply means to promote atomization of the fuel; an engine operating state detection means for detecting the operating state of the engine; a switching means provided in a circuit for supplying electricity to the electric heater; and a switching means for controlling the switching means on and off in accordance with the detected engine operating state to supply electricity to the electric heater. In the energization control device for a fuel atomization heater for an internal combustion engine, the energization control device includes: energization control means for intermittently controlling the energization of the electric heater; A current supply amount reduction control means is provided to gradually reduce the amount of current.

<Function> With this configuration, when the electricity supply to the electric heater is cut off, the electricity supply is not cut off in an on/off manner, but the amount of electricity supplied is gradually reduced by duty-controlling the on/off of the switching means. Since the temperature decreases, a sudden temperature drop of the electric heater is suppressed, and therefore, it is possible to prevent fuel atomization from deteriorating when electricity is cut off.

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

FIG. 2 shows the hardware configuration of this embodiment.

In the figure, an engine 1 is equipped with an electronically controlled fuel injection device of a so-called single point injection (hereinafter referred to as SPI) system in which one fuel injection valve 2 is provided as a fuel supply means on the upstream side of a throttle valve 3. It is something.

An electric heater (hereinafter referred to as PTC heater) 5 using a positive temperature coefficient thermistor (PTC) is interposed in the intake passage 4 on the downstream side of the throttle valve 3. The PTC heater 5 is controlled to be energized intermittently by a control unit 6 serving as energization control means.

The control unit 6 includes a water temperature signal Tw from a water temperature sensor 7 that detects the temperature of the engine cooling water.
The ON signal of a key switch (not shown) is input, for example, when the key switch is turned on.
PTC heater 5 when water temperature Tw is below 65℃
The relay 8, which serves as a switching means provided in the energizing circuit of the PTC heater 5, is turned on and off so that it turns on and turns off when the above conditions are not met.
energization control. That is, the engine operating state detecting means in this embodiment corresponds to the water temperature sensor 7 and the key switch.

In the figure, 9 is an air flow meter, and 10 is an air flow meter.
is the idle speed control valve.

As mentioned above, by turning on the PTC heater 5 when the water temperature Tw is low (65° C. or lower), that is, when the engine is cold, the atomization of fuel that is not sufficiently atomized at low temperatures is promoted.

Next, the operation will be explained based on the flowchart shown in FIG.

When the key switch is turned on and power is supplied to the control unit 6, the water temperature signal is first output at S1.
Load Tw, and in S2 read the water temperature
Determine whether Tw is 65°C or less. This is to determine whether the engine is in a cold state and the fuel is not sufficiently atomized.

When it is determined in S2 that the water temperature Tw is 65° C. or lower, the PTC heater 5 is energized in S3. At this time, power is supplied to the PTC heater 5 via the relay 8, but the drive signal from the control unit 6 that drives this relay 8 is controlled to have a predetermined duty τ (ON time ratio). S3 outputs 100% duty. Then, when the PTC heater 5 is energized,
Set the flag to 1 in S4.

1. When it is determined in S2 that the water temperature Tw exceeds 65°C, the process proceeds to S5 and the flag is determined. Here, when it is determined that the flag = 1,
This indicates that the PTC heater 5 was energized last time when the water temperature Tw was 65° C. or lower, so the amount of energization is controlled to be reduced by duty control of the relay 8, which will be described below.

In S6, a coefficient n (initial value is set to 0) for gradually decreasing the amount of electricity applied to the PTC heater 5
Add 1 to the current coefficient n. That is, the coefficient n is initially set to 1, and increases by 1 as the loop is repeated.

In S7, the duty τ of the drive signal of the relay 8 is calculated based on the coefficient n set in S6 (τ←100−10n), and the duty τ of this calculation result is
A drive signal having the following value is output to the relay 8. and,
In S8, it is determined whether or not the duty τ is zero, and if it is not zero, the process returns to S6 and the loop of S6 to S8 is repeated until the duty τ becomes zero. That is, the control unit 6 serves both as an energization amount reduction control means and an energization control means, and reduces the drive signal of 100% duty .tau. by 10% to gradually bring it to zero.

When it is determined in S8 that the duty τ is zero, the process proceeds to S9 where the coefficient n is returned to its initial value of zero, and the flag is set to zero in S10.

In this way, when the power supply to the PTC heater 5 is cut off, the amount of power supplied is gradually decreased (in this embodiment, it is decreased by 10%), so that the amount of heat generated is gradually decreased, and the temperature of the PTC heater 5 is as shown in FIG. gradually decreases as shown by the dotted line. Therefore, the amount of fuel adhering to the PTC heater 5 gradually increases with this slow temperature drop, so a large amount of fuel does not adhere to the PTC heater 5 at once, and the air-fuel ratio becomes lean due to the adhering fuel. can be prevented.

Note that the engine operating state as a condition for intermittent control of energization to the PTC heater 5 is not limited to the cooling water temperature shown in this embodiment, and under any condition, the power supply to the PTC heater 5 may be cut off as in the conventional case. (ON
→OFF), the tendency for the air-fuel ratio to become leaner is unavoidable. Further, in this embodiment, the PTC heater 5 is used as the electric heater, but it is clear that the electric heater is not limited to the PTC heater.

Furthermore, in this embodiment, when cutting off the power supply to the PTC heater 5, the ON duty of the relay 8 is reduced by 10%, but it is also possible to easily change the reduction rate midway through the process. It is easy to match the current flow reduction characteristics to the characteristics of the engine.

<Effects of the invention> As explained above, according to the invention, when power is cut off to the electric heater for promoting atomization of fuel, the amount of current is controlled by duty-controlling the switching means provided in the energization circuit. By gradually decreasing the amount, it is possible to prevent fuel from suddenly adhering when the electric heater is turned off.

This has the effect that when the electric heater is turned off, the air-fuel ratio does not become lean due to the adhering fuel, and deterioration in drivability can be avoided.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a schematic block diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing control in the same embodiment, and Fig. 4 shows characteristics of the electric heater. It is a time chart. 1... Engine, 2... Fuel injection valve, 4... Intake passage, 5... PTC heater, 6... Control unit, 7... Water temperature sensor, 8... Relay.

Claims (1)

[Scope of utility model registration request] an electric heater that is installed in the engine intake passage on the downstream side of the fuel supply means to promote atomization of the fuel; an engine operating state detection means that detects the operating state of the engine;
A switching means provided in an energization circuit to the electric heater, and an energization control means for controlling on/off the switching means in accordance with a detected engine operating state and controlling energization to the electric heater intermittently. In the energization control device for a fuel atomization heater for an internal combustion engine, the energization amount reduction control gradually reduces the amount of energization to the electric heater by duty-controlling the on/off of the switching means when the energization to the electric heater is cut off. 1. An energization control device for a fuel atomization heater for an internal combustion engine, characterized in that a means is provided.