JPS6312875A - Fuel injection controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable direct in-tube injection in a gasoline engine, by arranging a needle while facing against a combustion chamber and opening/closing a fuel path and an air path with respect to a combustion chamber by means of said needle. CONSTITUTION:A fuel injection valve 38 is fixed to a cylinder head such that fuel is injected directly into a combustion chamber so as to lead the air through a path 62 into an air chamber 52 and to lead the fuel into a path 68. Normally, a piezoelectric element 44 is extended upon power supply so as to close a valve body 66, and when the piezoelectric element 44 is shrinked upon interruption of power supply thereto, the valve body 66 is lifted so as to lead the fuel through a fuel path 64 into a combustion chamber 54. When a needle 42 is pushed up by the fuel pressure and the air pressure while resisting against a spring 46, fuel is injected through an injection port 58 while air is injected through an injection port 56 then they are mixed in a recessed section 60 and injected into the combustion chamber 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control valve device for an internal combustion engine, and more particularly to a fuel injection control valve device suitable for direct in-cylinder injection.

[Conventional technology]

In order to atomize fuel when the engine temperature is low, a so-called air-assisted fuel injection control valve device has been proposed. In conventional air-assisted fuel injection systems, air branched from the intake pipe upstream of the throttle valve is forcibly sent by a pump to a mixing chamber formed near the nozzle of the fuel injection valve.
It is injected together with fuel into the intake port. The air flow breaks up the droplets of the fuel from the nozzle and atomizes it.

[Problem that the invention seeks to solve]

In a gasoline-fueled internal combustion engine, air and fuel are sent as a mixture to a combustion chamber where they are combusted. However, this method of supplying fuel to the intake pipe inevitably has the problem of a delay in response to depression of the accelerator pedal. Furthermore, due to adhesion of fuel to the intake pipe wall surface, there is a deviation of the air-fuel ratio from the target value during transient operation, and in order to eliminate this deviation, acceleration correction of the fuel supply amount is performed, but it is difficult to make an ideal correction. Therefore, in a gasoline engine, the fuel is
It is conceivable to inject it directly into the cylinder, like in a diesel engine. In this case, it is necessary to inject a mixture of fuel and air. Air-assisted fuel injection valves are known as devices that inject fuel and air in a mixed state. (
For example, see Japanese Patent Application Laid-Open No. 54-40915. )However,
In conventional air-assisted fuel injection valves, air is mixed with the fuel coming out of the nozzle. However, with this method, it is impossible to perform in-cylinder injection because backflow into the air passage is unavoidable.

The object of the present invention is to provide a structure of a fuel injection valve that enables in-cylinder injection of gasoline.

[Means and effects for solving the problem] According to the present invention, there is provided a main body which is attached to the cylinder head and forms a fuel passage and an air passage, and a main body which is installed within the main body and has one end facing the combustion chamber of the internal combustion engine. An internal combustion engine characterized in that the fuel passage and the air passage are opened and closed with respect to a combustion chamber by the needle, and injection of fuel and air into the combustion chamber is controlled. A fuel injection control valve device for use is provided.

A needle located facing the combustion chamber operates to control the injection of air and fuel into the combustion chamber. Therefore, an air-fuel mixture is formed in the cylinder, allowing direct injection in a gasoline engine.

Preferably, the needle has first and second pressure receiving parts that receive air pressure and fuel pressure, respectively, and when the air pressure and fuel pressure simultaneously act on the first and second pressure receiving parts, the valve member opens. When the valve is opened, fuel and air are injected at the same time.

Air pressure and fuel pressure act on the valve member in separate parts, and when the resultant force overcomes the set pressure, the valve member is opened, and as a result, fuel and air are injected simultaneously.

〔Example〕

In FIG. 2, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a crankshaft, 18 is a cylinder head, 20 is a combustion chamber, 22 is an intake valve, 24 is an intake boat, 26 is an exhaust valve, 28 is an exhaust boat. The intake boat 24 includes an intake pipe 30 and a surge tank 3
2. Connected to an air flow meter 36 via a throttle valve 34.

A fuel injection valve 38 is attached to the cylinder head 18 so as to inject fuel directly into the cylinder. FIG. 1A shows an embodiment of the fuel injection valve of the present invention in which air and fuel are mixed externally. The fuel injection valve 38 has a main body 40,
Needle 42 and PZT (piezo) as a high-speed drive part
The piezoelectric element 44 is a basic component.

It should be noted that the high-speed drive section may be of an electromagnetic drive type.The two needles 42 are urged downward by a spring 46.

The needle 42 has a first pressure receiving surface 48 and a second pressure receiving surface 50. Air pressure within the air chamber 52 acts on the first pressure receiving surface 48, and fuel pressure within the fuel chamber 54 acts on the second pressure receiving surface 50. The air pressure and fuel pressure each force the needle 42 upwardly in the diagram and force the needle 42 against the compression spring 46.
When the engine lifts, air is injected from the air nozzle 56 and fuel is injected from the fuel nozzle 58, and the air and fuel collide in an external mixing chamber 60 to form a mixture, which is injected into the combustion chamber 20.

The air chamber 52 communicates with an air passage 62, and this air passage 6
2, high pressure air is introduced as described later. On the other hand, a fuel passage 64 is connected to the fuel chamber 54, and this fuel passage 64 is selectively communicated with a fuel passage 68 communicating with an external fuel supply source by a valve body 66 driven by the piezoelectric element 44.

In FIG. 2, the air passage 62 is connected to the intake pipe upstream of the throttle valve 34 but downstream of the air flow meter 36 via an air conduit 70 and an air pressurizing compressor 72 driven by the engine. A bypass passage 74 bypassing the compressor 72 is connected to the air conduit 70 and a bypass control valve 76 is installed. The bypass control valve 76 has a function as a relief valve that controls the pressure of air supplied from the air conduit to the fuel injection valve 38 at a constant level. Downstream of the bypass passage 74, an air conduit 70
A control valve 78 is installed to control the amount of air introduced from the air into the bypass control valve 38. This control valve 78 is equipped with fast-response drive parts 7B and A made of PZT elements and the like. The air control valve 78 may be installed for each cylinder, or may be shared by all cylinders.

The fuel passage 68 of the fuel injection valve 38 is connected to a fuel pump 82 via a fuel conduit 80, and the fuel pump 82 is connected to a fuel tank (not shown).

To explain the operation of the fuel injection valve 38 of FIG. 1A, air is introduced into the air chamber 52 through the conduit 70 and the passage 62, and an upward force acts on the first pressure receiving portion 48. However, since the set pressure of spring 46 is stronger than this force, needle 4
B cannot be lifted by air pressure alone. The fuel is pump 82
The fuel is then introduced into the fuel passage 68 via the conduit 80. The piezoelectric element 44 is normally expanded by energization, and the valve body 66 is expanded by the spring 6.
5, the valve closes and fuel is not supplied to the fuel chamber 54. When the power supply to the piezoelectric element 44 is stopped, the piezoelectric element 44 contracts, the valve body 66 lifts, and fuel is introduced into the fuel chamber 54 from the fuel passage 64. Therefore, the fuel pressure is reduced to the second pressure receiving surface 5.
An upward force acts on 0. As a result, the resultant force of the force based on the air pressure PA and the force based on the fuel pressure PB acts on the valve member 42, and this resultant force overcomes the setting force of the compression spring 46, so that the needle 42 is lifted. Then, fuel is injected from the nozzle 58, and since the air chamber 52 communicates with the notch 84, air is ejected from the nozzle 56. The air and fuel injected simultaneously in this manner are mixed in the recess 60 and are injected into the combustion chamber 20.

FIG. 1B shows the structure of a fuel injection valve in a second embodiment. This embodiment is configured to inject previously mixed air and fuel into the combustion chamber. The needle 42 is configured as an outer valve that opens by protruding outward. The upper end of the valve member 42 constitutes a first pressure receiving portion 48, and fuel pressure from the fuel passage 68 acts through the metering hole 84 when the valve body 66 is opened. On the other hand, the lower end of the needle 42 constitutes a second pressure receiving part 50 and receives the pressure of the mixing chamber 60 . The mixing chamber 60 has an air passage 62'.

62 to an air supply similar to that of FIG.

To explain the operation of the fuel injection valve shown in FIG. 1B, air is sent prior to injection, but at this time, the piezoelectric element 44 is energized, causing the needle 66 to descend and cut off the fuel. Therefore, the needle 42 receives a force based on the downward air pressure in the second pressure receiving part 50. However, this force is caused by the compression spring 5 acting upwardly on the needle 42.
Since it is weaker than the setting of 2, the needle 42 is closed.

During fuel injection, the valve body 6 is pressed by the biasing force of the disc spring 65.
6 rises, and the fuel pressure from the fuel passage 68 reaches the metering hole 84.
It acts on the tenth pressure receiving surface 4B via. At this time, a resultant force of the fuel pressure on the first pressure receiving surface 48 and the fuel pressure on the second pressure receiving surface 5o acts on the needle 42, and since this resultant force exceeds the set force of the compression spring 52, the needle 42 descend. At this time, fuel enters the mixing chamber 60 through the metering hole 84, mixes with air, and is ejected from the nozzle port 86.

FIG. 1C shows another embodiment of an outward-opening type fuel injection valve that mixes air and fuel first.

A collar 91 is fitted and attached to the upper end of the needle 42, and a first pressure receiving surface 48 is formed on the upper surface of the collar 91. The umbrella portion at the lower end of the needle 42 constitutes a second pressure receiving surface 50 . 9
2 is a stopper that determines the valve lift. The body is divided into an outer body 40a and an inner body 40b, between which an annular air passage 62 is formed. Annular air passage 62 communicates with annular mixing chamber 60 . Fuel fills the fuel space 90 within the inner body 40b. When the needle 42 performs a predetermined lift, the fuel space 90 enters the mixing chamber 6 through the metering hole 84.
0 and is ejected from the nozzle 86 via the passage 92. A recess 94 is formed in the bottom of the main body 40b upstream of the spout 84.
This recess 94 becomes a mixing chamber that holds the air-fuel mixture between the lift start position of the needle 42 and the full stroke position shown by the two-dot chain line. In addition, the main body 40
The cylinder head 18 around a is the water jacket 1
8C can be formed to improve cooling performance.

Further, making the air passage 62 annular also contributes to improving the cooling performance of the needle 42. In addition, an external opening type needle 42
The tip can be made of ceramic to make it more resistant to the effects of combustion heat.

The operation of the fuel injection valve 38 according to the present invention shown in FIGS. 1A, 1B, and 1C is controlled by an electronic control device described below. In FIG. 2, 100 is a control circuit, which is configured as a microcomputer system. The control circuit 100 includes a microprocessing unit (MPU) 102,
Memory 104, input port 106, and output port 10
8 and a bus 110 that connects these are the basic components.

Various sensors are connected to the input port 106 to which engine operating condition signals are applied. A signal corresponding to the intake air amount Q is obtained from the air flow meter 36. A signal TH corresponding to the opening degree of the throttle valve 34 is obtained from the throttle sensor 112. Temperature sensors 114 and 116 are installed in the water jackets of the cylinder head 18 and cylinder block 10, and provide signals corresponding to their respective temperatures.

A crank angle sensor 118 is installed facing a rotating member 120 that rotates integrally with the crankshaft 16.
A pulse signal corresponding to the rotation of 6 is obtained.

A control program is stored in the memory 104, and performs control operations to be described later. output capo) 108 is the fuel injection valve 38
piezoelectric element 44, piezoelectric drive section 78A of air control valve 78,
Furthermore, a signal is sent to the drive section 76A of the relief valve 76.

FIG. 3A is a timing diagram illustrating an example of how the fuel injection valve according to the present invention operates.

Although the supply of fuel and air is intended to occur during the intake stroke, it may also occur at the beginning of the compression stroke. The fuel injection amount is determined according to the load factor (intake air amount to rotational speed ratio), and the fuel injection time to obtain this fuel injection amount is τ.
Let it be i. Injection start time is tl, injection path change time is t2
During this time, the piezoelectric element 44 that drives the fuel supply control valve body 66 is neutralized, and an injection time of τi is obtained.

On the other hand, the air control valve 78 starts operating at time t3 and stops operating at time t4. The air control valve 78 is driven by a pulse signal, and the air control valve 78 is driven by a pulse signal.
The duty ratio, which is the ratio of N hours B, is controlled to obtain a desired degree of atomization. That is, as the duty ratio approaches 1, the amount of air increases, so the degree of atomization of the fuel becomes stronger, and the duty control allows vibrational operation of the needle, which also contributes to improved atomization. The operation start time t3 of the air control valve 78 is earlier than the fuel supply start time t1. This is intended to sufficiently atomize the left-handed fuel when the valve is opened at time t1 by filling air prior to fuel supply.

Furthermore, the operation stop time of the air control valve 78 is a time t4, which is later than the fuel supply stop time t2.

This is intended to prevent sagging by blowing away residual fuel near the injection path.

(c) in FIG. 3A shows the lift characteristics of the needle 42, and shows the time t1 when the fuel pressure and air pressure start to be applied simultaneously.
The valve begins to open at , starts closing at time t2 when the fuel pressure is stopped, and completes at t5, which is slightly later than t4.

The drive signal for the air control valve before and after the start of fuel supply is set to be a continuous signal (or set to a higher duty ratio than the duty ratio during fuel injection) as shown in Figure 3B, thereby promoting atomization at the start of injection and promoting injection. It is possible to further improve the effect of preventing sag at the end of the process.

Times t1 to t5 are determined as follows.

First, the valve closing time t5 of the needle 42 is determined by the air control valve 78.
The duty ratio of the drive pulse signal, that is, the degree of atomization, is determined as shown in FIG. In FIG. 4, the vertical axis is expressed as the crank angle from the intake top dead center TDC. That is, the smaller the particle size (the larger the duty ratio B/A), the faster the injection is completed. This is to ensure that the fuel injection ends quickly and the fuel evaporates sufficiently.

On the other hand, the larger the particle size (the smaller the duty ratio B/A), the later the fuel injection ends to suppress the occurrence of knocking.

Next, time t1 is calculated using the following equation.

t1=t5-6X10 xNex (τi+ΔS2) (1) Here, ΔS2 is the time required to close the needle,
It is a measured value or the number of actual measurements.

Time t3 is calculated by the following formula.

t3=t5-6X10 xNex (τi+Δt1+ΔS2) ...(2) Furthermore, tl
, t3 must not be before the intake top dead center in order to prevent blow-through to the exhaust gas.

The general flow of an actual program that implements the above operations will be explained below with reference to flowcharts. FIG. 5 shows a crank angle interrupt routine that is executed every time a pulse signal arrives from the crank angle sensor 118. In step 200, it is determined whether the crank angle corresponds to the top dead center of the intake stroke (time 10 in FIG. 3A). In step 202, it is determined whether engine water temperature TW≦predetermined value T1. When the engine is cold, TW≦T1, and the process proceeds to step 204, where the duty ratio B/A is set to 1. That is, the amount of air is maximized and the strongest degree of atomization is obtained.

After the engine warms up, TW>Tj, and step 202
The process then proceeds to step 206, where it is determined whether the throttle valve opening TH>predetermined value θ0. When the throttle valve is partially opened, TH≦00, and the process proceeds to step 208, where the duty ratio B/A is set to a predetermined value β (<1.0). This predetermined value is set based on the amount of air that optimizes the fuel particle size during partial opening. Also, when the throttle valve is fully open, T
Since H>θ0, the process proceeds to step 210, where the duty ratio is calculated based on the intake air amount to revolution speed ratio Q/N, which is the load equivalent value.

In step 212, times t1 to t4 are calculated according to the above equation (1).
, (2).

In step 214, time t1 is set in the conveyor register A of the control circuit 100, which sets the valve opening time of the fuel injection control valve body 66, and in step 216, the time t1 is set in the conveyor register A of the control circuit 100.
A time t3 is set in the conveyor register B of the control circuit 100, which sets the operation start time.

When time t3 arrives, an interrupt signal is applied from conveyor register B to MPU 102, and the time coincidence interrupt routine shown in FIG. 6 is activated. In step 222, it is determined whether the flag F1=1.

This flag F1 is set to "1" during fuel injection, and set to "0" when fuel injection is stopped. At time t1, fuel injection has not yet been performed, so F1=0, and the process proceeds to step 224.
The rise time TON of the pulse signal is calculated according to the value of the duty ratio B/A. In order to promote atomization by supplying more air than usual before starting fuel supply, the duty B/A is made thicker than usual (or the duty ratio B/A is set to 1.0 as shown in Fig. 3B). In step 226, T is input to the down counter 121 (see FIG. 2) for forming the duty signal.
ON' is set. At step 228, a time Δt corresponding to one cycle of the pulse signal is set in the conveyor register B.

Therefore, prior to fuel supply, the air control valve 78 is driven by a pulse signal having a desired duty ratio from time t1.

When time t1 comes, flag F1=1, so step 2
22, proceed to step 230, and step 20 in FIG.
The rise time TON of the pulse signal is calculated according to the duty ratio B/A of the drive pulse signal of the air control valve 78 calculated in 4.208.210. At step 232, the rise time TON of the pulse signal is set in the B register. Therefore, during fuel supply, the air control valve is driven by the calculated duty ratio signal.

When the time t2 arrives, the flag Fi=0, so the flow goes from step 222 to step 224 in the same way as before the start of fuel injection, and TON' is calculated from the duty ratio B/A of the pulse signal after the end of fuel injection. . This prevents the fuel from becoming deformed.

FIG. 10 explains the formation of the duty signal as a result of the execution of the routine of FIG. That is, the down force rotor 12
Data corresponding to TON, . . . TON' is set to 1, and a signal of "1" is output until the countdown of that data is completed. Then, the countdown is executed every Δ corresponding to one cycle of the pulse signal.

FIG. 7 shows a time coincidence interrupt routine for conveyor register A, which is initially activated when time 1 arrives. In step 239, it is determined whether flag F1=1. Since F1=0 before fuel injection, the process proceeds from step 239 to step 240, where a Low signal is applied to the drive member 44 of the fuel injection valve 38. Therefore, the fuel pressure is allowed to be applied to the needle 24, and the resultant force with the already applied air pressure lifts the needle 24, and the air is injected into the cylinder together with the fuel.

In step 242, flag F1 is set, and in step 244, time t2 is set in conveyor register A. When that time t2 arrives, the time match interrupt routine is activated again, this time in step 239 to flag F.
1-1, the flow goes to step 246, and the driving member 44
A High signal is applied to. Therefore, fuel supply is cut off. At step 248, flag F1 is reset.

FIG. 8 shows a calculation routine for the fuel injection amount. This routine may be executed at regular intervals or may be executed before step 212 in the middle of the routine of FIG. At step 250, the basic injection amount τBASE is calculated from the intake air amount to revolution speed ratio Q/N. Here k is a constant. In step 252, the basic fuel injection amount is determined by various factors a and b.

C, and τi is calculated.

FIG. 9 shows a routine for correcting the air pressure on the supply side so that the fuel injection amount does not change due to fluctuations in cylinder pressure. This routine is assumed to be executed at regular intervals. At step 260, a map calculation of the cylinder pressure P1 is executed. In other words, since cylinder pressure is determined by engine operating conditions such as load and rotation speed, map values of cylinder pressure according to these operating condition factors are stored in advance in memory, and this map can be used to determine the engine operation. The cylinder pressure under the conditions is calculated. In step 262, the detected value of the air pressure po detected by the pressure sensor 119 is input. Step 2
At 64, the difference between the cylinder pressure P1 and the air pressure po is compared with a predetermined value Δ.

If the actual difference is greater than the predetermined value Δ, the process proceeds to step 268, and the signal to the actuator 78A is controlled to increase the opening degree of the relief valve 78. Conversely, if the actual difference is smaller than the predetermined value Δ, the process proceeds to step 270, and the actuator 78 is activated so that the opening degree of the relief valve 78 is increased.
The signal to A is controlled. When the actual difference and the predetermined value are substantially equal, the opening degree of the relief valve 78 is maintained. Through such feedback control, the difference between the cylinder pressure and the air pressure is controlled to a predetermined value Δ, and it is possible to correct the cylinder pressure fluctuation so that it does not affect the fuel injection amount. Note that the differential pressure correction can also be performed using fuel pressure instead of the air pressure correction in the embodiment.

In the embodiment, the fuel injection valve is opened by applying air pressure first and then applying fuel pressure, but conversely, by applying fuel pressure first and then applying air pressure, the fuel injection valve is opened. It is also possible to open the valve.

〔effect〕

According to this invention, a single needle facing the combustion chamber of an internal combustion engine is installed in the fuel injection valve, and the injection of both fuel and air is controlled by the needle, thereby enabling direct in-cylinder injection in a gasoline engine.

As an effect of the embodiment, the needle is provided so as to open when air pressure and fuel pressure are applied at the same time, and by ejecting fuel and air to mix them, air is preliminarily supplied to the fuel injection valve prior to injection. By supplying it in advance, a highly fine particle state can be obtained from the initial stage of injection.

[Brief explanation of drawings]

FIG. 1A, FIG. 1B, and FIG. 1C are sectional views showing the structure of each embodiment of the fuel injection valve of the present invention. FIG. 2 is an overall schematic diagram of a direct injection gasoline internal combustion engine equipped with the fuel injection valve of the present invention. FIGS. 3A and 3B are timing diagrams illustrating the air and fuel supply operations of the present invention. FIG. 4 is a graph explaining the relationship between duty ratio B/A and injection completion time t5. FIGS. 5 to 9 are flowcharts illustrating the operation of the control circuit. FIG. 10 is a diagram for explaining how to form duty No. 13 using a down counter. DESCRIPTION OF SYMBOLS 10... Cylinder block, 18... Cylinder head, 20... Combustion chamber, 38... Fuel injection valve, 42... Needle, 44... PZT piezoelectric element, 48.50... Pressure receiving 70... Air passage, 78... Air control valve, 80... Fuel passage, 82... Air pump, 100... Control circuit.

Claims (2)

[Claims] 1. It has a main body that is attached to the cylinder head and has a fuel passage and an air passage, and a needle that is installed in the main body and has one end facing the combustion chamber of the internal combustion engine, and has a fuel passage and an air passage. A fuel injection control valve device for an internal combustion engine, characterized in that the needle is opened and closed with respect to a combustion chamber to control injection of fuel and air into the combustion chamber. 2. The needle has a first pressure receiving part that receives air pressure and a second pressure receiving part that receives fuel pressure, and the needle opens when the fuel pressure and air pressure act on the respective pressure receiving parts. Claims 1. A fuel injection valve device for an internal combustion engine according to.