JPS6380029A - Fuel control unit for engine - Google Patents

Abstract

PURPOSE:To slow down a temperature drop in a spark plug as well as to prevent an insulator from cracking, by delaying a fuel supply stop as long as the specified time at a time when a lowering degree of combustion temperature is more than the specified value at the time of engine deceleration. CONSTITUTION:An injector 12 is attached to a side housing of a rotary engine, and spark plugs 15 and 16 are attached to a rotor housing 1 as well. When a control unit 18 detects a decelerated state of more than the specified value in an engine, it finds the estimated value of combustion temperature from reach revolution out of the engine speed sensor installed in an eccentric shaft 4 and an air flow meter 7. And, when the estimated value is smaller than the specified value, fuel injection is stopped after the elapse of the specified time. With this constitution, the combustion temperature is lowered by degrees, thus an insulator of the spark plug is prevented from cracking.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control device for an engine.

[Prior art]

The combustion temperature of an engine changes depending on engine rotational speed and load fluctuations, etc.
As shown in Japanese Patent No. 22, when fuel supply to the engine is stopped when deceleration exceeds a predetermined value for the purpose of improving fuel efficiency, the combustion temperature rapidly decreases.

However, when the combustion temperature changes rapidly as shown above,
A large heat load is generated within the engine, resulting in a significant decrease in the durability of the insulator of the spark plug, for example, and in the worst case, the insulator may crack. In particular, in a rotary engine, ignition occurs sequentially in each working chamber, so the temperature of the spark plug during normal operation when fuel is supplied is higher than that of a reciprocating engine (and the temperature is higher when the fuel supply is stopped). As the temperature drop of the spark plug increases, the frequency of the above-mentioned insulator cracking increases.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned problems of the conventional art, and is designed to minimize damage such as cracks in the insulator of the spark plug caused by a drop in combustion temperature due to the stoppage of fuel supply to the engine. The object of the present invention is to provide an engine fuel control device that can prevent such problems.

[Structure of the invention]

In order to achieve the above object, the engine fuel control device according to the present invention detects the deceleration state of the engine, and when a predetermined deceleration or more is detected, fuel control is performed to stop fuel supply to the engine. The apparatus is provided with combustion detection means for detecting the degree of decrease in the combustion temperature of the engine, and when deceleration exceeding a predetermined value is detected and the degree of decrease in the combustion temperature determined by the combustion detection means is equal to or greater than a predetermined value, the fuel supply is stopped in a predetermined manner. A delay means is provided to delay the time, so that when the combustion temperature decreases by more than a predetermined value due to the stoppage of fuel supply during deceleration exceeding a predetermined level, the fuel supply is continued and the intake air amount decreases due to deceleration. By slowing down the combustion inside and then stopping the supply of fuel for a predetermined period of time! ! ! By stopping the combustion, even if the combustion temperature drops by a predetermined value or more due to the stoppage of fuel supply, the combustion temperature is gradually lowered gradually and the large heat load inside the engine is reduced. This feature is characterized in that it is configured to prevent this from occurring.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 to 5. An embodiment in which the present invention is applied to a rotary engine will be described as follows. As shown in FIG. The engine includes a rotor housing 1 and a pair of side housings (not shown) connected to both sides of the rotor housing 1. A rotor 2 is rotatably arranged in the rotor housing 1 with its apex in contact with the inner surface of the rotor housing 1, and three working chambers are formed between the rotor 2 and the rotor housing 1. There is. An internal gear 3 provided on the inner periphery of the rotor 2 is meshed with an external gear 5 provided on the side housing.

The intake pipe 6 having the air flow meter 7 is branched into two branch pipes 6a and 6b on the downstream side of the air flow meter 7, and each branch pipe 6a and 6b has a primary side and a Throttle valves 8 and 9 on the secondary side are respectively arranged. One branch pipe 6a is connected to an intake boat 11 provided on one side housing, and the other branch pipe 6b is connected to another intake port (not shown) provided on the side housing, and is attached to each side housing. Fuel is injected into each intake boat 11 from an injector 12 (only the negative side housing side is shown).

An exhaust boat 13 is formed in the rotor housing l, and an exhaust pipe 14 is connected to this exhaust boat 13.

Furthermore, leading-side and trailing-side spark plugs 15 and 16 are arranged in the rotor housing 1, and each spark plug 15 and 16 is electrically connected to an ignition device 17.

The control unit 78, which functions as a combustion detection means and a delay means, receives an intake air m signal sent from the air flow meter 7 and a throttle valve opening sensor (not shown) provided on each throttle valve 8, 9. a throttle valve opening signal sent from the intake pipe, an intake pipe pressure signal sent from the intake pipe pressure gauge 19 installed in the intake branch pipe 6a, and an engine rotation speed signal sent from a rotation speed sensor (not shown) installed on the eccentric shaft 4. Based on the above, the ignition timing of each spark plug I5, 16 by the ignition device 17, the amount of fuel injection from each injector 12 to each intake boat 11, injection timing, etc. are controlled.

In the above configuration, each intake boat 1 is
Fuel is injected from an injector 12 into the air supplied to the rotor housing 1, and a mixture of this air and fuel is sequentially drawn into each working chamber in the rotor housing 1. The intake air-fuel mixture is compressed as the rotor 2 rotates, and then ignited by each spark plug 15 and 16 to explode, imparting rotational force to the rotor 2, and then passed through the exhaust boat 13 and exhaust pipe 14. is exhausted. In this way, the suction, compression, explosion, and exhaust strokes are sequentially performed in each working chamber to rotate the rotor 2, and the rotational force of the rotor 2 is transmitted to the eccentric shaft 4. The control unit 1B detects the deceleration state of the engine during the engine operation period described above, and stops injection of fuel into the intake boat 11 from the injector 12 when detecting deceleration of a predetermined value or more. At this time, in order to prevent damage to the engine such as cracking of the insulators of spark plugs 15 and 16 due to thermal shock caused by a sudden drop in combustion temperature due to the stoppage of fuel injection, the combustion temperature is reduced due to the stoppage of fuel injection. When the combustion temperature decreases by more than a predetermined value, the control unit 18 is configured to delay the fuel injection stop operation from the time when deceleration of more than a predetermined value is detected by a time corresponding to the degree of decrease in combustion temperature accompanying the deceleration. has been done.

Hereinafter, the control procedure of the control unit 18 will be explained in detail with reference to the flowchart shown in FIG.

When the engine starts, the control unit 18
First, the engine speed sensor and air flow meter 7
and the engine rotation speed r from the throttle valve opening sensor.
pm, intake air amount Qa, and throttle valve opening degree TVO are each read (Sl-S3), and then the temperature parameter X is obtained by multiplying the read engine rotational speed rpm and the intake air amount Qa (S4). This temperature parameter X is, so to speak, an estimated value of the combustion temperature of the engine, and increases as the combustion temperature increases. In this S4,
Assuming that fuel injection will be stopped in a step to be described later, the combustion temperature before injection is stopped is estimated in advance. In addition,
The combustion temperature after the fuel injection stops can be considered to be almost constant regardless of the combustion temperature before the fuel injection stops, so determining the combustion temperature before the fuel injection stops This has the same significance as determining the degree of decrease in combustion temperature.

Next, it is determined whether the obtained temperature parameter X is smaller than a predetermined value a set in advance (S5). If the temperature parameter After setting the delay time parameter y by subtracting the correction amount X' obtained from the graph from the initial value of the delay time parameter y (S6), the process moves to S8. The initial value of the delay time parameter y is the delay time parameter y within a range where the temperature parameter
is set to be "0" or a negative value. Also,
In S5, if the temperature parameter After setting (S7), the process moves to S8. In the range where the temperature parameter X is greater than or equal to the predetermined value a,
The delay time parameter y has a positive value, and the correction amount X' increases as the temperature parameter X increases, so as the temperature parameter X increases, the delay time parameter y increases.

In S8, based on the delay time parameter y, a delay time t, that is, a waiting time from when deceleration exceeding a predetermined value is detected to when fuel injection is stopped, is set in the timer from the graph of FIG. This delay time t is the delay time parameter y
is “0” or in the negative range, in other words, the temperature parameter
On the other hand, in the range where the delay time parameter y is positive, that is, the temperature parameter As the delay time parameter y becomes larger, it becomes longer (but becomes flat in the range where the delay time parameter y exceeds a certain value).

Next, read the engine rotation speed rpm and throttle valve opening TVO once again (S9 510), and read the engine rotation speed rpm and throttle valve opening T.
Based on VO, it is determined whether the operating state of the engine at that time is included in the fuel injection stop zone 2 indicated by diagonal lines in FIG. 5 (Sll). The combination of engine rotation speed rpm and throttle valve opening TVO is the above zone Z.
If it is included in the above, it is assumed that the deceleration is greater than the predetermined value. If the operating state of the engine at that point is not within the fuel injection stop zone, that is, the deceleration zone Z above a predetermined value, it is necessary to inject fuel, so the control unit 18 outputs a fuel injection signal to the injector 12 ( After performing injection control (S13)' for the injector 12 in step S12), the process returns to step S1.

On the other hand, if the operating state of the engine is included in the fuel injection stop zone Z in the above Sll, then the timer is set to "0".
It is determined whether or not the value is below (S14). If the timer is larger than "0", although the vehicle is decelerating more than a predetermined value, it is not yet time to stop fuel injection, so the timer is subtracted (S15) and a fuel injection signal is output to the injector 12 (S16). After controlling the injection of the injector 12 (318), the process returns to S9. Also, S
If the timer is "0" or less in step 14, it is time to stop fuel injection, so a fuel injection stop signal is output to the injector 12 (S17) L, and the injection stop control (S1
After performing 8), return to S9.

In the above embodiment, the combustion temperature of the engine is estimated using a temperature parameter obtained by multiplying the intake air amount and the engine rotation speed, but the combustion temperature can also be detected by other methods.

In addition to delaying the timing of stopping fuel injection in the above embodiment, it is possible to increase the amount of air charged into the engine during the period from when deceleration exceeding a predetermined level is detected until stopping fuel injection. By further slowing down the rate of decrease in combustion temperature when fuel injection is stopped, it is possible to further reduce the risk of engine damage such as cracking of the insulator. Further, the present invention is applicable not only to the rotary engine having the structure shown in FIG. 1, but also to other known rotary engines and various reciprocating engines having various structures.

〔Effect of the invention〕

As described above, the engine fuel control device of the present invention is a fuel control device that detects the deceleration state of the engine and stops the fuel supply to the engine when a deceleration of more than a predetermined value is detected. Combustion detection means for detecting the degree of decrease in combustion temperature is provided, and delay means for delaying the stop of the fuel supply for a predetermined period when deceleration exceeding a predetermined value is detected and the degree of decrease in combustion temperature by the combustion detection means is equal to or greater than a predetermined value. This is the configuration provided. As a result, if the combustion temperature drops by more than a predetermined value during deceleration above a predetermined value, the combustion within the engine is first slowed down by the reduction in the amount of intake air accompanying the deceleration while fuel supply continues, and then the combustion is delayed for a predetermined period of time. Since the combustion is stopped by stopping the fuel supply, even if the combustion temperature drops by more than a predetermined value due to the stoppage of the fuel supply, the combustion temperature can be lowered gradually and gradually. As a result, the generation of a large heat load within the engine is prevented, and damage such as cracking of the insulator of the spark plug can be prevented as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram of a rotary engine having a fuel control device of the present invention, FIG. 2 is a flowchart showing the control procedure of the fuel control device of the present invention, and FIG. 3 is a diagram showing correction amounts of temperature parameters and delay time parameters. A graph showing the relationship between
FIG. 4 is a graph showing the relationship between the delay time parameter and the delay time, and FIG. 5 is an explanatory diagram showing a fuel injection stop zone determined by a combination of engine rotation speed and throttle opening. 18 is a control unit (combustion detection means and delay means). Patent applicant Mazda Co., Ltd. Figure 3; JIrL Runozu Rameg

Claims (1)

[Claims] 1. In a fuel control device that detects the deceleration state of the engine and stops fuel supply to the engine when a deceleration of more than a predetermined value is detected, combustion detection means is provided to detect the degree of decrease in the combustion temperature of the engine. A fuel control device for an engine, comprising a delay means for delaying the stop of the fuel supply for a predetermined period of time when a deceleration of a predetermined value or more is detected and the degree of decrease in combustion temperature determined by the combustion detection means is a predetermined value or more.