JPS6371545A - Combustion controller for engine - Google Patents

Abstract

PURPOSE:To prevent the sharp rise of the combustion temperature by carrying out at least one among the control for delaying the ignition timing and the control for increasing fuel when the rise of the combustion temperature over a prescribed level is detected. CONSTITUTION:In a control unit 18, the intake air quantity is read from an air flow meter 7, and the engine revolution speed is read from a revolution speed sensor, and the combustion temperature variation rate is estimation calculated by multiplying these variation rates. When the temperature variation rate is over a prescribed value previously determined, a prescribed time is set on a timer, and the initial delay angle quantity at the ignition timing and the initial quantity increase rate of the fuel injection quantity are set to the larger values as the temperature variation rate becomes larger. Therefore, the delay angle control for the ignition timing and the increase control for the fuel injection quantity are carried out for a prescribed time, and the sharp rise of the combustion temperature is prevented, and the breakage such as crack of the insulations of spark plugs 15 and 16 can be prevented beforehand.

Description

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

[Prior art]

The combustion temperature of an engine changes depending on changes in engine speed and load. For example, if the engine is operated at high speed and high load for a long period of time, the temperature of the exhaust system may rise abnormally. In order to take countermeasures, Japanese Patent Application Laid-Open No. 59-201
．． As shown in No. 950, when the temperature of the exhaust system is high,
There are things that increase the amount of fuel. By the way, when the engine accelerates rapidly, the temperature of the exhaust system does not rise much, but the combustion temperature rapidly changes in the upward direction, so the heat generated in the engine due to this change in combustion temperature increases. Due to the impact, for example, the durability of the insulator of a spark plug is significantly reduced, and in the worst case, the insulator may crack. In particular, in a rotary engine, combustion occurs sequentially in each working chamber, so the period during which the spark plug is exposed to high temperatures is longer than in a reciprocating engine.
The maximum temperature of the spark plug increases accordingly. For this reason,
In a rotary engine, the temperature change of the spark plug increases, which increases the risk of causing the insulator crack as described in ``2''.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and in particular provides an engine combustion control device that can reduce damage to the engine such as cracking of the spark plug insulator due to a rise in combustion temperature. It is intended for the purpose of providing.

[Structure of the invention]

In order to achieve the above object, the engine combustion control device of the present invention detects a change in combustion temperature of the engine, and when an increase in combustion temperature of a predetermined level or more is detected, controls the ignition timing to be delayed. , a combustion control means is provided that performs at least one of the control to increase the amount of fuel, and when the ignition timing is delayed, the combustion efficiency of the fuel is thereby lowered.On the other hand, when the amount of fuel is increased, the combustion Due to the cooling effect of the heat of vaporization of excess fuel that does not occur, and when both delaying the ignition timing and increasing the amount of fuel,
The present invention is characterized in that it is configured such that a sudden rise in combustion temperature can be prevented by the synergistic effect of the reduction in combustion efficiency and the cooling effect due to the heat of vaporization.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows a sectional view when the present invention is applied to a rotary engine. This rotary 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 disposed within 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. An internal gear 3 provided on the inner periphery of the rotor 2 is meshed with an external gear 5 fixed to 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 boat (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 one side housing side is shown).

An exhaust port 13 is formed in the rotor housing 1, and an exhaust pipe 14 is connected to the exhaust port 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 18 as a combustion control means receives an intake air amount signal sent from the air flow meter 7, a throttle valve opening signal sent from a throttle valve opening sensor (not shown) provided on each throttle valve 8, 9, The ignition device 17 is activated based on the intake pipe pressure signal sent from the intake pipe pressure gauge 19 installed in the intake branch pipe 6a, the engine rotation speed signal sent from the rotation speed sensor (not shown) installed on the eccentric shaft 4, etc. Each spark plug 15 and 16 by
Ignition timing, each injector 1? Each intake boat from 1
The fuel injection amount, injection timing, etc. for the engine 1 are controlled.

In the above configuration, each intake port 1 is
Fuel is blown into the air supplied to the rotor housing 1 from an injector 12, and a mixture of this air and fuel is sequentially drawn into each working chamber in the rotor housing 1. The inhaled air-fuel mixture is compressed as the rotor 2 rotates, and is then ignited and exploded by each spark plug 15, 16. This imparts rotational force to the rotor 2, and then the exhaust port 13, exhaust pipe It is exhausted via 14. 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.

If a change in the combustion temperature is detected during the engine operation period mentioned above, and if this combustion temperature is detected to rise above a predetermined value per unit time, an occurrence occurs within the engine due to the sudden temperature rise. Spark plug 15 due to thermal shock
・In order to prevent damage such as 16 insulator cracks,
The above control unit 18 has spark plugs 15 and 16
The ignition timing is corrected to the retarded side, and control is performed to increase the amount of fuel injected from the injector 12.

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, set the timer to "O" and initialize it (31)L, then read the intake air amount Qa from the air flow meter 7 (S2) and read the engine rotation speed rpm from the rotation speed sensor (S3). I do. Next, the read intake air amount Qa and engine rotation speed rpm
Set the basic ignition timing of the spark plugs I5 and 16 and the basic fuel injection amount from the injector 12 based on (S4
・S5) Do it.

Subsequently, the rate of change ΔQa of the intake air amount Qa (for example, the difference between the Qa read this time and the Qa read last time) and the rate of change Δrpm of the engine rotation speed rpm are determined, and by multiplying these, the rate of change ΔTemp (= Δ
QaXΔrpm), that is, the amount of temperature change per unit time is estimated (S6). And the temperature change rate ΔTem
It is determined whether or not p is smaller than a predetermined value a, which is a predetermined positive value (37). A predetermined time t is set (S8) L, and control to suppress a rise in combustion temperature is started. In this case, in order to prevent the rate of increase in combustion temperature from reaching a value that may cause damage such as cracking of the insulator of the spark plugs 15 and 16 (hereinafter referred to as the upper limit rate), , the predetermined value a may be set to a value somewhat smaller than the risk increase rate.

When the predetermined time t is set in the timer, first, the initial correction amount to retard the ignition timing, that is, the initial retard amount and the initial increase rate of the fuel injection amount are set (S9), and then the process moves to 314. Here, the initial retard amount is as shown in FIG.
If the temperature change rate ΔTemp is large (as the value is large,
On the other hand, although not shown, the initial increase rate of the fuel injection amount is also set to a larger value as the temperature change rate ΔTemp becomes larger.

In S7, if the temperature change rate ΔT e m p is smaller than the predetermined value a, which is a positive value, even if the combustion temperature is rising, the rate of increase is relatively small, or the combustion temperature is falling, so at this point There is no need to newly start combustion temperature rise suppression control. In this case, it is then determined whether the timer is "O" or not (S10), and if the timer is not "0", then the combustion temperature rise suppression control is in progress, so the timer is subtracted (311) L. After updating the correction amount of the retardation amount and the increase rate of the fuel injection amount (S12>), the process moves to S14.As shown in FIG. 4, the retardation amount is changed over time after the timer starts. As the time progresses, the value is gradually decreased from the initial value set in step 89, and when the predetermined time t has elapsed and the timer expires, the value is returned to the value before the timer was set.Furthermore, as shown in FIG. The increase rate of the injection amount is also gradually decreased from the initial value as time passes after the timer starts.The increase rate of the injection amount is shown in the middle zone in Figure 5, and this is determined by the engine speed rpm and, for example, the intake pipe pressure. This is an increase rate that is preset for each operation zone divided according to the load evaluated by The increase rate is set.

In SIO, if the timer is ``O'', it means that the combustion temperature increase suppression control is not in progress, so ``0'' is set as the correction amount for the ignition timing and fuel injection amount (S13)L.
The process moves to S14. 31.4 and the following 315, the actual ignition timing and basic fuel injection amount set in S4 and S5 are added with the correction amount set in either S9 and 2.313. The ignition timing and fuel injection amount are set, and then, based on these values, an injection control signal and an ignition control signal are output to the injector 12 and the ignition device 17, respectively (S16 and 31).
7) After that, return to S2.

Note that in the example described in "=", the rate of change in the combustion temperature was estimated based on the rate of change in the intake air amount and the rate of change in the engine speed, but the rate of change in the combustion temperature could be detected by other methods. You can also.

In addition, in the second embodiment, when an increase in combustion temperature exceeding a predetermined level is detected, both the ignition timing is retarded and the amount of fuel is increased. It is also possible to perform only one of the above, and in this case as well, the effect of suppressing the combustion temperature to some extent can be obtained. Furthermore, the present invention is applicable not only to the rotary engine having the structure shown in FIG. 1, but also to rotary engines and various reciprocating engines having various other known structures.

〔Effect of the invention〕

As described above, the engine combustion control device of the present invention detects a change in the combustion temperature of the engine, and when an increase in combustion temperature exceeding a predetermined level is detected, controls the ignition timing to be delayed and increases the amount of fuel. This configuration includes combustion control means that performs at least one of the following controls. This results in
If the ignition timing is delayed, this will reduce the combustion efficiency of the fuel, while if the amount of fuel is increased, the cooling effect due to the heat of vaporization of the excess fuel that is not combusted will cause the ignition timing to be delayed and the fuel If both of these are increased, the synergistic effect of the reduction in combustion efficiency and the cooling effect of the heat of vaporization will prevent a sudden rise in combustion temperature within the engine, thereby preventing problems such as cracking of the spark plug insulator. This has the effect that damage can be avoided as much as possible.

[Brief explanation of the drawing]

1 to 5 show one embodiment of the present invention, FIG. 1 is a cross-sectional explanatory diagram of a rotary engine equipped with a combustion control device, FIG. 2 is a flowchart showing a control procedure of the combustion control device, and FIG. The figure is a graph showing the relationship between the initial retard amount and the rate of temperature change, Figure 4 is a graph showing the relationship between the retard amount and the timer elapsed time, and Figure 5 is the graph showing the relationship between the fuel increase rate and the timer elapsed time. It is a graph showing the relationship between. 18 is a control unit (combustion control means).

Claims (1)

[Claims] 1. Combustion control means is provided that detects a change in the combustion temperature of the engine, and performs at least one of control to delay the ignition timing and control to increase the amount of fuel when an increase in the combustion temperature to a predetermined level or more is detected. An engine combustion control device characterized by: