JP2820777B2 - Idling control system for in-cylinder injection two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to idling of a direct injection two-cycle engine in which fuel is directly injected into a cylinder to perform local combustion at least at low load and low rotation. Regarding the control device, especially when a target idling rotational speed higher than usual according to the warm-up state of the engine is set during a cold period,
The present invention relates to a device capable of stably maintaining an engine speed at the target idling speed.

[Conventional technology]

In an engine idling control device, the target idling rotational speed is generally set to a high value because it is difficult to stabilize the idling rotational speed during a cold state immediately after the start of the engine or the like. As an idling control device that can realize such a high idling rotational speed, a device that increases the fuel injection amount is considered.

[Problems to be solved by the invention]

By the way, even if the above-mentioned idling control device is adopted for a direct injection type two-stroke engine, it is difficult to increase the engine speed to a high target idling speed in a cold state, so that idling operation becomes unstable. In extreme cases, engine rotation stops.

In the case of a direct injection type two-stroke engine, such a problem arises even if the fuel is simply increased unless the time required for atomizing the fuel is sufficiently secured. Can not be taken out, and as a result, the engine speed does not rise to the target value.

The present invention has been made to solve such a conventional problem, and in particular, it is possible to keep the engine speed at a target idling speed set higher than usual at a cold time, and to stabilize the idling operation. It is an object of the present invention to provide an idling control device for a direct injection two-cycle engine.

[Means for solving the problem]

The present invention relates to an in-cylinder injection type two-stroke engine idling control device in which fuel is directly injected into a combustion chamber every one revolution of a crankshaft by a fuel injection device and then ignited. Means,
Idling detecting means for detecting an idling state of the engine, temperature detecting means for detecting a temperature indicating a warm-up state of the engine, target idling speed setting means for setting the target idling speed higher as the detected temperature is lower, In the idling state, (i) fuel is injected into the combustion chamber after closing the exhaust port during a rising stroke in which the piston moves from bottom dead center to top dead center, and (ii) the piston is moved during the rising stroke. Within the range after closing the exhaust port, the fuel injection start timing is set to be advanced as the target idling speed set value set according to the detected temperature is higher, and the fuel injection end timing is set. The fuel may be kept constant irrespective of the target idling speed setting value or may be retarded as the target idling speed setting value is higher, so that the fuel (Iii) When the detected engine speed falls below the target idling speed set value, the injection period is set to be longer as the target idling speed set value is higher. Within the range, the fuel injection start timing is advanced with respect to the injection start timing set value set in accordance with the target idle speed setting value, and the fuel injection end timing is set to the target idle speed setting value. The fuel injection period is extended from the fuel injection period set value corresponding to the target idling rotational speed set value by keeping the injection end timing set value correspondingly set or retarding the injection end timing set value. And (iv) further advancing the injection start timing with respect to the injection start timing set value and extending the fuel injection period with respect to the fuel injection period set value. After maintaining the state for a predetermined time, the fuel injection device is configured to return the injection start timing stepwise to the injection start timing set value, and to return the fuel injection period stepwise to the fuel injection period set value. And a fuel injection control means for controlling.

Here, the present invention provides a so-called simultaneous injection type engine in which air and fuel are separately and simultaneously injected into a cylinder and mixes them at this time, or an engine in which only fuel is injected, and air in a chamber. The fuel can be applied to any of the so-called precharge type engines in which the fuel and the fuel are previously injected and mixed, and the air-fuel mixture is injected into the cylinder.

Further, as the temperature indicating the warm-up state of the engine in the present invention, for example, a cooling water temperature can be adopted in the case of a water-cooled engine, and a cylinder wall temperature can be adopted in the case of an air-cooled engine.

For the target idling speed, it is preferable to map in advance the engine speed at which the engine can stably rotate at each detected temperature by experimentation and to map the fuel injection start timing. Conversion time,
In other words, the time from fuel injection to ignition is determined by experiment,
It is preferable that the fuel injection start timing capable of securing the atomization time is calculated backward and mapped.

[Action]

According to the idling control device of the present invention, when the piston closes the exhaust port during the ascent stroke in the idling state, the fuel is injected into the combustion chamber, and the fuel is ignited after the injection is completed, the target idling speed Is set to be higher as the engine temperature is lower, that is, to be able to rotate stably even when the engine is cold.Furthermore, the fuel injection start timing is set to be advanced as the target idling speed setting value is higher, and the fuel injection is set. Since the period is set to be extended, the fuel is injected with the cylinder pressure being lower, the difference between the injection pressure and the cylinder pressure increases, and the fuel injection speed and the air penetration force increase. In addition to being able to sufficiently atomize the injected fuel, it is possible to inject a sufficient amount of fuel. Can be kept in the packaging speed can be stabilized idling of the cold.

When the detected engine speed falls below the target idling speed set value, the fuel injection start timing is advanced from the injection start timing set value set in accordance with the target idling speed set value, and the fuel injection is started. Since the period has been extended from the fuel injection period set value set in accordance with the target idling rotational speed set value, fuel will be injected at a lower cylinder pressure, and the difference between the cylinder pressure and the injection pressure will increase. As a result, the fuel injection speed and the air penetration force are increased, and the injected fuel can be sufficiently atomized, and a sufficient amount of fuel can be injected, thereby increasing the external load. The engine speed can be returned to the target idling speed set value, and engine stall can be prevented.

Further, after maintaining the advanced state of the injection start timing with respect to the set value of the injection start time and the extended state of the fuel injection period with respect to the set value of the fuel injection period for a predetermined time, setting of the injection start time corresponding to the target idling rotation set value is performed. Since the value and the fuel injection period set value are returned in a stepwise manner, the engine speed does not suddenly decrease even when an external load is applied, and engine stall can be prevented.

When the injection timing is advanced, the piston is advanced within a range after the exhaust port is closed during the upward stroke, so that the fuel injected into the combustion chamber is directly discharged from the exhaust port. That is, the problem of blow-by can be reliably prevented, and deterioration of fuel efficiency can be prevented.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 to 8 are views for explaining an idling control device for an air-fuel injection type two-stroke engine according to one embodiment of the present invention. FIG. 1 is a block diagram showing the overall configuration, and FIG. FIG. 3 is a diagram showing the relationship between the cooling water temperature and the target idling speed, FIG. 3 is a diagram showing the relationship between the engine speed and the injection timing and injection time, and FIG. FIG. 4 (b) is a diagram showing a change in engine speed, FIG. 5 is a diagram for explaining an idling region, FIG. 6 is a diagram showing an injection start timing together with each port timing, FIG. FIG. 8 is a sectional view showing an air fuel injection device main body, and FIG. 8 is a flowchart for explaining the operation of this embodiment.

First, the structure of the air fuel injection device main body will be described in detail with reference to FIG.

The air fuel injector main body 2 mainly includes an injection body 9 inserted and fixed to a cylinder head 8, and an injection body 9.
It comprises a valve mechanism 10 for opening and closing the injection ports of the air chamber and the fuel chamber formed therein, and a fuel injection valve 11 mounted on the rear portion of the outer wall of the injection body 9 and supplying fuel to the fuel chamber. Have been.

The injection body 9 has a housing 13 inserted into a mounting hole 8b facing the combustion chamber 12 of the cylinder head 8, and presses and fixes the housing 13 on the cylinder head 8.
It comprises a valve body 10 and a body 14 that holds the fuel injection valve 11, and a flange (not shown) of the body 14 is bolted and fixed to the cylinder head 8.

The housing 13 has an inner housing 16 formed integrally with an upper end of a cylindrical body 16a and a flange 16b formed at the upper end of a cylindrical body 16a, which is formed integrally with an upper end of a cylindrical body 15a. Of the outer housing 15 is pressed and fixed on the cylinder head 8 by the body main body 14.

Here, the inside of a hole passing through the axis of the inner housing 16 is an air chamber 17, and the lower end opening of the through hole is the combustion chamber 12.
The air injection port 16c faces the front. Also, upper and lower lateral grooves 16 are provided on the upper and lower portions of the outer peripheral surface of the inner housing 16.
d and 16e are recessed in a ring shape, and the upper and lower lateral grooves 16
The d and 16e are connected to each other by a pair of longitudinal grooves 16f formed in the outer peripheral surface so as to extend in the axial direction. The inside of each of the horizontal grooves 16d, 16e and the vertical grooves 16f is a fuel chamber 18,
The fuel chamber 18 communicates with the inside of the combustion chamber 12 by a fuel injection port 16g formed at the lower end of the inner housing 16. Note that 1
9 is a seal ring.

Above the spark plug 35 at the portion of the body body 14 located on the rear side when mounted on the vehicle, a mounting recess 14a for mounting the fuel injection valve 11 is recessed substantially parallel to the spark plug. The interior of the mounting recess 14a communicates with the upper lateral groove 16d of the fuel chamber 18 by fuel passages 14b and 15c formed so as to extend obliquely downward from the body main body 14 and the flange portion 15b of the outer housing 15. ing. And the mounting recess 14a
The injection nozzle side end of the fuel injection valve 11 is inserted therein, and the tip end surface 11a of the injection valve 11 is
At a slight gap from the front end and the bottom surface 14c.
Between them, a rubber cushioning member 20 is interposed.

The fuel supply port 11b at the upper end of each fuel injection valve 11 is
It is inserted into the book fuel rail 21 and communicates with the fuel passage 21a in the rail 21. This fuel rail 21
Is made of an aluminum alloy drawn material, and is bolted and fixed to the upper surface of the cylinder head 8 by a stay 22.

A valve 23 constituting the valve mechanism 10 is inserted into the through hole of the inner housing 16 from below.
The valve 23 is formed integrally with a mushroom-shaped valve plate 23b at the lower end of a valve shaft 23a, and the air injection port 16c and the fuel injection port 16g are opened and closed by the valve plate 23b. Further, the valve shaft 23a protrudes from the upper surface of the body 14, and a disc-shaped retainer 24 is screwed into the protruding portion 23c and fixed with a lock nut 25.The retainer 24 is surrounded by a cap 26. I have. Excited below the retainer 24 when energized,
An electromagnetic coil 27 that attracts the pump 24 downward is embedded. Further, a cylindrical spring seat 28 is variably screwed up and down in the axis of the electromagnetic coil 27, and the valve 23 is attached between the spring seat 28 and the retainer 24 in the closing direction. A biasing spring 29 for biasing is provided. Reference numeral 30 denotes a set bolt for fixing the spring seat at a predetermined position.

Further, an air inlet 14d is formed in the body main body 14, and the inlet 14d communicates with the air chamber 17 in the inner housing 16 through a communication hole 28a formed in the spring seat 28. ing. An air rail 3 is provided on the front side of the air fuel injection device main body 2 so as to cover the air introduction port 14d.
1 is arranged. The air rail 31 is made of an aluminum alloy drawing material, and an air passage 31a formed therethrough communicates with an air inlet 14d on the body body 14 side by a branch passage 31b. A plug 32 closes a processing hole when the branch passage 31b is formed.Although not shown, one end of the air passage 31a is connected to a compressed air source, and the other end is connected to a pressure valve. Air passage 31a
The inside, and thus, the inside of the air chamber 17 of the inner housing 16 is adjusted to a predetermined air pressure.

Next, a control system of the air fuel injection device main body 2 will be described with reference to FIGS.

In FIG. 1, reference numeral 40 denotes a rotation speed detection sensor for detecting the engine rotation speed, 41 a throttle opening detection sensor comprising a potentiometer for taking out the opening position of the throttle valve as a voltage, and 42 a cooling water temperature of the engine. The water temperature detection sensor 43 is a control unit that controls the overall operation state of the engine, and includes a target idling speed setting unit 43a and an air fuel injection control unit 43b.

The target idling speed setting section 43a is configured to read a target idling speed corresponding to the detected water temperature from a built-in water temperature / target idling speed map (see FIG. 2). Also, the air fuel injection control unit
43b reads the air fuel injection time (injection amount) and the injection timing for realizing the target idling speed from the built-in idling speed-air fuel injection time / timing map (see FIG. 3); When the engine rotational speed falls below the target idling rotational speed, the injection amount and the injection start timing are increased and advanced, respectively, and the increased and advanced state is maintained for a predetermined time, and then the original injection amount and injection timing are gradually increased. It is configured to return to.

Here, the water temperature-target idling speed map (FIG. 2) is obtained by experimentally obtaining an engine speed at which the engine can stably rotate at each cooling water temperature, and using this as a target idling speed. Water temperature is 80 ℃
The water temperature is substantially linearly higher as the water temperature is lower, such as 750 rpm in the case of 1,200 rpm in the case of 10 ° C.

The idling speed-air fuel injection time map (curve A in FIG. 3) is obtained by an experiment to determine the amount of fuel required to achieve the target idling speed.
It is converted into an injection time necessary to secure the fuel amount and is mapped. Furthermore, the idling speed-air fuel injection timing map (curve B in FIG. 3)
An atomization time required to atomize the fuel amount is obtained by an experiment, and an injection start time at which the atomization time can be secured is calculated back and mapped.

As is clear from FIGS. 3, 2 and 6,
The lower the cooling water temperature is, the higher the target idling speed is set, and the fuel injection start timing is set to the advanced side. In FIG. 6, a method of advancing at the time of cold idling is to advance both the injection start timing and the end timing as a whole as shown by a solid line in FIG. 6 and to advance only the injection start timing. Both cases (shown by dashed lines) are included. In this case, the injection amount is increased by extending the injection period.

Next, the control operation of idling at the time of cold will be described mainly with reference to the flowchart of FIG.

First, in step S1, a throttle opening (a potentiometer output) from the throttle opening detection sensor 41 is read and the detected opening is compared with a predetermined idling opening, that is, as shown in FIG. It is determined whether or not the engine is idling based on whether or not the potentiometer output is in the idle region (step S2). When the detected opening degree is larger, the operation is terminated as the non-idling state, and the idling control is not performed. On the other hand, if it is small, it is determined that the engine is in the idling state, the detected water temperature from the water temperature detection sensor 42 is read, and the target idling speed corresponding to the detected water temperature is set according to the map shown in FIG. The air fuel injection time and injection timing are set according to the map shown in FIG. 3 (steps S3 to S3).
5) This is output to the valve mechanism 10 and the fuel injection valve 11.

After a lapse of a predetermined time, the engine speed from the speed sensor 40 is read, and the detected engine speed is compared with the target idling speed (steps S6 and S7), and the detected engine speed is higher than the target idling speed. If so, the operation ends. On the other hand, if the load increases due to the activation of the compressor of the air conditioner and the engine speed falls below the target idling speed (engine speed a in FIG. 4B) (rotation speed b in FIG. 4), step 8 follows. , The increase value of the air fuel injection amount set in accordance with the reduced rotation speed, the advance value of the injection timing (for example, 3 degrees in crank angle).
゜) is set and output to the valve mechanism 10 and the fuel injection valve 11. After a lapse of a predetermined period t (for example, a period during which the engine rotates 70 times) in the increased and advanced state, the increased and advanced values are decreased and retarded by a preset value (for example, 1 ° in crank angle). Set the value and output (Steps S9, S
Ten).

Then, the engine speed is read again, and the detected engine speed is compared with the target idling speed (Step S11,
S12) When the engine speed decreases (FIG. 4 (b)
Immediately after returning to step S8, that is, after the short time t 'has elapsed, the state is returned to the above-described increased and advanced state. If it is higher, the routine proceeds to step S13 to return the injection amount and the injection timing to the reference values. It is determined whether or not the operation has ended. If the operation has returned, the operation is terminated. If the operation has not returned, the steps of reducing the amount and retarding the angle are repeated in steps S9 and S10. As a result, as shown in FIG. 4 (a), the advanced angle amount gradually returns from 3 ° to 2 °, 1 ° and the reference injection timing.

As described above, in the present embodiment, in the idling control, first, the target idling speed is set to be higher as the cooling water temperature is lower, that is, the idling speed at which the engine can stably rotate even in a cold state is obtained. Since the air fuel injection amount (injection time) corresponding to the number is set and the air fuel injection start timing is advanced so that the time required for atomizing the injection amount is obtained, the high idling speed Is obtained, the engine speed can be kept at this idling speed, and the idling operation can be stabilized.

Also, by advancing the injection start timing, the fuel is injected at a lower pressure in the cylinder,
The fuel injection speed increases, and the air penetration force increases. From this point, the atomization is improved, and the engine speed is increased.

Furthermore, in the case of the present embodiment, the fuel injection port is opened near the opening of the air passage. Therefore, by advancing the injection start timing, the injection is performed at a time when the cylinder internal pressure is low, and the pressure difference from the fuel pressure increases, and the injection amount increases.

Also, in the idling speed control, the fuel is injected into the combustion chamber after closing the exhaust port during the rising stroke in which the piston moves from the bottom dead center to the top dead center, and the fuel is ignited early after the injection is completed. In addition, stratified combustion can be generated, and idle rotation is easily stabilized.

In the case where the fuel injection start timing is advanced as the target idling rotational speed set value is higher, the piston is advanced within the range after the exhaust port is closed during the ascent stroke, so that the fuel is injected into the combustion chamber. Since the discharged fuel is reliably prevented from being directly discharged from the exhaust port, there is no deterioration in fuel efficiency.

In the present embodiment, in the idling control, after setting the injection amount and the like in step S5, the engine speed is compared with the target idling speed, and when the engine speed decreases, the fuel injection amount is immediately increased and the injection is started. Since the timing is advanced, the engine speed does not decrease even if, for example, the electric load increases, and the idling operation can be stabilized from this point as well.

Furthermore, in the present embodiment, after the above-described increase and advance state is held for a predetermined time, the advance value (crank angle 3 °) is not returned immediately to the original state, but is returned step by step by 1 °. When the engine speed decreases while returning in a stepwise manner, the advancing state is advanced again in a short time t ', so that the idling operation can be stabilized from this point as well.

Further, in this embodiment, since the engine speed is controlled by the injection start timing, it is necessary to adjust the injection time of the fuel injection valve when increasing or decreasing the engine speed,
Or less. For this reason, the idling speed is stable during idling even though the dynamic range is at the very end of the unstable range.

Note that, by advancing the injection start timing, it is not necessary to increase the fuel injection amount if atomization of the fuel is sufficiently promoted, but if the injection timing cannot be advanced sufficiently, the same as in the present embodiment. At the same time, the fuel injection amount may be increased.

Here, the following can be adopted as means for increasing the fuel injection amount.

As in the present embodiment, when the simultaneous injection type is used and the fuel passage is opened near the valve that opens and closes the air passage, the injection amount is also increased by advancing the injection start timing without changing the injection period. it can. This is because the pressure difference between the injection pressure and the cylinder pressure increases due to the advance of the injection start timing, and as a result, the injection amount increases. Note that when the advance amount is greatly increased, the injection amount may be able to be increased even if the injection period is shortened.

In the case of the simultaneous injection type, the injection start timing is advanced to extend the injection period. In this case, the injection end timing may remain at the injection end timing set value corresponding to the target idling rotational speed set value or may be retarded.

In the case of the precharge type, the injection amount can be increased by lengthening the injection period into the chamber. In this case, it is necessary to advance the opening timing of the valve that opens and closes the opening to the cylinder, but it is not always necessary to lengthen the opening period of the valve.

In any case, the fuel injection amount may be controlled by changing the fuel pressure.

In the above embodiment, the case where the present invention is applied to a water-cooled engine has been described. However, the present invention can also be applied to an air-cooled engine. The present invention can also be applied to a precharge type in which fuel and air are injected into a chamber in advance and mixed, and the air-fuel mixture is injected and supplied into a cylinder.

〔The invention's effect〕

As described above, according to the idling control apparatus for a direct injection two-cycle engine according to the present invention, the target idling speed is set higher as the engine temperature is lower, that is, the target idling speed is set so that the engine can stably rotate even in a cold state. As the target idling speed set value is set higher to advance the fuel injection start timing and the injection period is set longer so that the fuel atomization time obtained can be obtained, the target idling speed set value The time required to sufficiently atomize the corresponding amount of fuel can be obtained, and the engine speed can be maintained at the target idling speed setting value,
There is an effect that the idling operation can be stabilized.

When the detected engine speed falls below the target idling speed set value, the fuel injection start timing is advanced from the injection start timing set value, and the fuel injection period is extended from the fuel injection period set value. The fuel is injected at a lower cylinder pressure, and the difference between the cylinder pressure and the injection pressure increases to increase the fuel injection speed,
The penetration force in the air increases, and the injected fuel can be sufficiently atomized, and a sufficient amount of fuel can be injected. This allows the engine speed to reach the target idling speed even when the external load increases. The number can be restored, and the engine stall can be prevented.

Further, after maintaining the advanced state of the injection start time with respect to the injection start time set value and the extended state of the fuel injection period with respect to the fuel injection period set value for a predetermined time, the injection start time set value corresponding to the target idling speed set value Since the fuel injection period is returned to the set value stepwise, the engine speed does not suddenly decrease even when the external load is still applied, and engine stall can be prevented.

When the injection start timing is advanced, the piston is advanced within the range after closing the exhaust port during the upward stroke, so that the fuel injected into the combustion chamber is directly discharged from the exhaust port. This has the effect of reliably preventing blow-through and preventing fuel economy from deteriorating.

[Brief description of the drawings]

1 to 8 are diagrams for explaining an idling control device of an air-fuel injection type two-stroke engine according to one embodiment of the present invention. FIG. 1 is a block diagram showing the overall configuration, and FIG. FIG. 3 is a characteristic diagram showing the relationship between the cooling water temperature and the target idling speed, FIG. 3 is a characteristic diagram showing the relationship between the engine speed and the injection time / injection timing, and FIG. FIG. 4 (b) is a diagram showing a change in engine speed, FIG. 5 is a diagram for explaining an idling region, FIG. 6 is a diagram showing an injection timing together with an opening period of each port, FIG. FIG. 7 is a sectional view showing the air fuel injection device main body, and FIG. 8 is a flowchart for explaining the operation of the present embodiment. In the figure, 41 is a throttle opening detection sensor (idle detection means), 42 is a water temperature detection sensor, 43a is a target idling speed setting unit, and 43b is an air fuel injection control unit.

Continuation of the front page (56) References JP-A-61-207854 (JP, A) JP-A-61-55343 (JP, A) JP-A-62-659 (JP, A) JP-A-59-153941 (JP) JP-A-1-294936 (JP, A) JP-A-2-301644 (JP, A) JP-A-63-500322 (JP, A) JP-A-63-500320 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02D 41/00-41/40

Claims (1)

(57) [Claims] An idling control device for a direct injection two-stroke engine in which fuel is directly injected into a combustion chamber every one revolution of a crankshaft by a fuel injection device and then ignited. Detecting means;
Idling detecting means for detecting an idling state of the engine, temperature detecting means for detecting a temperature indicating a warm-up state of the engine, target idling speed setting means for setting the target idling speed higher as the detected temperature is lower, In the idling state, (i) fuel is injected into the combustion chamber after closing the exhaust port during a rising stroke in which the piston moves from bottom dead center to top dead center, and (ii) the piston is moved during the rising stroke. Within the range after closing the exhaust port, the fuel injection start timing is set to be advanced as the target idling speed set value set according to the detected temperature is higher, and the fuel injection end timing is set. The fuel may be kept constant irrespective of the target idling speed setting value or may be retarded as the target idling speed setting value is higher, so that the fuel (Iii) When the detected engine speed falls below the target idling speed set value, the injection period is set to be longer as the target idling speed set value is higher. Within the range, the fuel injection start timing is advanced with respect to the injection start timing set value set in accordance with the target idle speed setting value, and the fuel injection end timing is set to the target idle speed setting value. The fuel injection period is set to a value corresponding to the target idling rotational speed set value by keeping the injection end timing set value correspondingly set or retarding the injection end timing set value. (Iv) further advancing the injection start timing with respect to the set value of the injection start timing, and setting the fuel injection period relative to the set value of the fuel injection period. After holding the long state for a predetermined time, the fuel injection device is configured such that the injection start timing gradually returns to the injection start timing set value, and the fuel injection period gradually returns to the fuel injection period set value. And a fuel injection control means for controlling the idling control of the in-cylinder injection two-cycle engine.