JPH09217644A - Fuel injection device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inject the optimum quantity of fuel at all times by providing a magnetic gap detection means detecting the magnetic gap of a fuel injection valve, and thereby correcting the driving condition of the injection valve based on the detected magnetic gap in such a way that the quantity of fuel injection will meets the target quantity of fuel injection. SOLUTION: A fuel injection valve 14 houses a valve ingredient 16 roughly in a bar like shape in its cylindrical valve casing 15 in such a way as to be freely moved back and forth, and the valve ingredient 16 is driven back and forth by an electromagnetic coil 17. The valve ingredient 16 is formed out of a puppet 16a to be mounted to/demounted from a valve seat 15e, and of an armature 16b, and a magnetic gap G is provided between the armature 16b and a cylindrical body 15b. The magnitude of the magnetic gap G influencing the magnitude of driving force when a magnetic coil 17 pulls the valve ingredient 16 in, is analogized by the ambient temperature detected by a temperature sensor. The driving voltage value or driving current value of the fuel injection valve 14 is controlled based on the magnetic gap G in such a way that the quantity of fuel injection will be the target quantity of fuel injection obtained in response to the conditions of engine operations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an engine in which a fuel injection valve is attached to a cylinder head or the like so as to directly inject fuel into a combustion chamber.

[0002]

2. Description of the Related Art Recently, a so-called direct injection type gasoline engine in which fuel is directly injected into a combustion chamber by a fuel injection valve has been provided. This direct-injection gasoline engine is expected to significantly improve fuel efficiency and clean exhaust gas.

[0003]

However, in order to directly inject the fuel into the combustion chamber, the fuel injection valve must be attached to the cylinder head or the like so that its injection port faces the combustion chamber. Therefore, there is a concern that the operation of the fuel injection valve becomes unstable and the injection amount changes.

It is considered that the cause of the variation of the injection amount is that the internal magnetic gap changes from the design value due to the temperature of the fuel injection valve itself becoming high. This magnetic gap is extremely important for operating the fuel injection valve accurately, and is precisely adjusted one by one at the time of production. When this magnetic gap changes, the injection characteristics also change greatly.

It is considered that the cause of the magnetic gap fluctuation is the difference in the coefficient of thermal expansion between the valve box and the valve body, and the difference in the amount of thermal expansion due to the temperature difference between the two. Therefore, in order to prevent the fluctuation of the magnetic gap, the valve box on the high temperature side is made of a material having a small thermal expansion coefficient, and the valve body on the low temperature side is made of a material having a relatively large thermal expansion coefficient. It is necessary to lower the temperature of the injection valve itself to 100 ° C or less, which is comparable to the intake pipe injection.

Although the above method is simple, it is difficult to accurately grasp the temperature of the valve element, and it may not be possible to cope with it depending on operating conditions. Further, the above method is also difficult because the fuel injection valve has to be mounted on a high temperature portion such as a cylinder head and a cylinder block.

The present invention has been made in view of the above conventional circumstances, and provides a fuel injection device for an engine capable of injecting an appropriate amount of fuel even if the magnetic gap of the fuel injection valve changes. That is the issue.

[0008]

According to a first aspect of the present invention, there is provided a fuel injection valve arranged to directly inject fuel into a combustion chamber, and a fuel injection amount is a target determined according to an operating state of an engine. A fuel injection device for an engine, comprising: an injection control unit that controls the fuel injection valve so that an injection amount is achieved; a magnetic gap detection unit that detects a magnetic gap of the fuel injection valve; And a correction means for correcting the drive condition of the fuel injection valve based on the magnetic cap so that the amount becomes a quantity.

According to a second aspect of the present invention, in the first aspect, the magnetic gap detecting means is configured to obtain the magnetic gap based on the temperature of the fuel injection valve.

According to a third aspect of the present invention, in the first aspect, the magnetic gap detecting means is configured to obtain the magnetic gap based on the inductance of the fuel injection valve.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the correcting unit applies a drive voltage or a drive current when the magnetic gap detected by the magnetic gap detecting unit is large to a small magnetic gap. It is characterized in that it is made larger than the drive voltage or drive current at that time.

According to a fifth aspect of the present invention, in any one of the first to third aspects, the correction means sets the fuel injection time when the magnetic gap detected by the magnetic gap detection means is large and the fuel injection time when the magnetic gap is small. The feature is that it is longer than the injection time.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 9 are views for explaining an engine fuel injection device according to a first embodiment of the invention of claims 1, 2 and 4, and FIG. 1 is a block diagram thereof, FIG. 2, FIG. Is a cross-sectional side view of the engine,
4 is a bottom view of the cylinder head, FIG. 5 is a sectional side view of the fuel injection valve, FIG. 6 is a block configuration diagram of the fuel supply system, FIG. 7 is a temperature-magnetic gap characteristic diagram, and FIG. 8 is a magnetic gap-voltage / current. A characteristic diagram, FIG. 9 is a fuel injection amount correction coefficient-magnetic gap characteristic diagram.

In FIG. 1, reference numeral 1 denotes a CPU for controlling various actuators of a fuel supply system. The CPU 1 has an engine speed signal from an engine speed sensor 2, an engine load signal from a throttle opening sensor 3, and a temperature. The fuel injection valve ambient temperature signal from the sensor 4, the voltage waveform signal across the electromagnetic coil of the fuel injection valve from the voltage measurement circuit 7, and the fuel injection valve drive current signal from the current sensor 12 are input, and the fuel injection valve drive circuit is input. 6, various control signals described later are output to the inductance detection high-frequency current generation circuit 8 and the ignition control circuit 9. Reference numeral 5 is a memory in which various control data are stored.

Reference numeral 17 is an electromagnetic coil of the fuel injection valve 14 described later, and 13 is a switching transistor for controlling the power supply from the driving power source (battery) 15 to the fuel injection valve 14.

2 to 4 showing the mounting state of the fuel injection valve 14 on the engine 20, the engine 20 has a cylinder head 23 and a cylinder head 23 connected to the head-side mating surface of the cylinder block 22 by a head bolt 19. Cylinder head 2
3 has a structure in which a cam chamber 24 formed in the upper part of 3 is covered with a head cover 25.

A piston 27 is slidably inserted in the cylinder block 22, and a block-side mating surface 23 of a cylinder head 23 is attached to a top portion 27a of the piston 27.
A cavity 28 that forms a combustion chamber with the combustion recess 23a recessed in g is recessed. An electrode 29a of the spark plug 29 is provided above the tip side inclined surface 28a of the cavity 28.
Is located.

The combustion recess 23a of the cylinder head 23
Has two left and right intake valve openings 30a and 30b and two left and right exhaust valve openings 31a and 31b, which are respectively intake valves 35, 35, intake camshaft 38, and exhaust valve 3.
6,36 Exhaust cam shaft 39 opens and closes.

The left and right intake valve openings 30a and 30b are
As shown in FIG. 4, the intake ports 32a having a bifurcated shape are joined to each other and led out to the rear wall 23b of the cylinder head 23. The intake port 32a has a throat portion 32b formed coaxially with the valve shaft 35b of the intake valve 35 when viewed in the cam axis direction (see FIG. 2), and thus the intake port 32a has a straight line. A space for disposing the fuel injection valve 14 can be secured between the portion 32c and the block-side mating surface 23g.

A branch portion 32d of the intake manifold 32 is connected to the intake port 32a. A bias valve 37 is arranged in the branch portion 32d. The drift valve 37 has a cutout 37a and is parallel to the camshaft.
It is rotatable around a fully open position and a closed position shown by a solid line in FIG. 3, and is opened and closed by an actuator (not shown). When the drift valve 37 is rotated to the closed position, intake air is taken in by the top wall of the intake port 32a and the cutout portion 3.
7a, and flows toward the top wall side in a biased manner, flows axially from the cylinder center side along the exhaust side inner surface of the cylinder bore 26d, and reverses at the piston top surface 27a. A pair of left and right vortices, so-called tumble, are generated.

As shown in FIG. 3, the fuel injection valve 14 is disposed between the intake port 32a of the cylinder head 23 and the block-side mating surface 23g in parallel with the straight portion 32c of the intake port 32a. The insertion portion is surrounded by the cooling jacket 23f. And the cooling jacket 23f
The temperature of the cooling water inside the fuel injection valve 14 is controlled by the temperature sensor 4.
The ambient temperature (valve box temperature) is detected.

As shown in FIG. 5, in the fuel injection valve 14, a substantially rod-shaped valve body 16 is inserted in a substantially cylindrical valve box 15 so as to be movable back and forth, and the valve body 16 is moved forward and backward by an electromagnetic coil 17. Is configured to drive.

The valve box 15 is constructed by inserting and fixing a cylinder body 15b and a nozzle body 15c into upper and lower openings of a cylindrical casing 15a having upper and lower ends opened, and at the axis of the cylinder body 15b. Is provided with a fuel introduction hole 15d, and the nozzle body 15c
A valve seat 15e is formed at the lower end of the. A guide 15f is fixed to the nozzle body 15c, and injection holes 15g and 15h are formed in the guide 15f to guide and inject fuel in the direction of the spark plug and the direction of the top surface of the piston.

The valve body 16 has the valve seat 15e at the tip thereof.
The valve 16a is detachably attached to the armature 16b and the armature 16b that forms a part of the magnetic circuit. The magnetic circuit is formed by a cylindrical body 15b, an armature 16b, and a casing 15a. A valve body 16 is provided between the upper end of the armature 16b and the lower end of the cylindrical body 15b.
A return spring 18 that biases 5e in the closing direction is inserted.

A flange portion 1 is provided in the middle of the valve 16a.
6c is formed, and the opening of the injection port 15e is regulated by the flange portion 16c contacting a stopper 15i formed on the nozzle 15c. A magnetic gap G is provided between the upper end surface of the armature 16b and the lower end surface of the cylindrical body 15b with the valve 16a in close contact with the valve seat 15e. Since it is divided, the magnetic gap G is adjusted so as to accurately match a predetermined design value during manufacturing.

Since the magnetic gap G divides the magnetic circuit as described above, it greatly affects the magnitude of the driving force when the electromagnetic coil 17 pulls the valve body 16.
When the magnetic gap G is excessively large, the driving force becomes weak, and in an extreme case, the valve body 16 may become immovable. On the contrary, when the magnetic gap G is excessively small, the driving force becomes sufficient, The magnetic force disappearance time when the signal is off becomes longer, and the return of the valve body 16 becomes worse.

In FIG. 6 showing the fuel supply system 41 to the fuel injection valve 14, the fuel in the fuel tank 42 is supplied by the fuel supply pump 44 via the filter 45 to the high-pressure fuel pump 43.
Is supplied to. The high-pressure fuel pump 43 is rotatably driven by the engine 20 via a continuously variable transmission 54 to increase the pressure of the fuel supplied from the supply pump 44 to a high pressure, and the check valve 4
It is supplied to the pressure accumulating chamber (common rail) 47 via 6. The feed amount of the fuel supply pump 44 is always larger than the discharge amount of the high-pressure fuel pump 43, and the surplus amount is returned to the fuel tank 42 through the return path 41a. The fuel in the accumulator 47 is
The space 1 on the upstream side of the valve seat 15e, which is supplied at a high pressure into the fuel injection valve 14 and passes through the tubular body 15b and the armature 16b and is closed by the valve 16a, as indicated by the arrow in FIG.
5j is filled with high pressure. Therefore, the fuel is
Injection is performed during the period when the valve body 16 opens the valve seat 15e.

In the pressure accumulating chamber 47, when the pressure in the pressure accumulating chamber 47 reaches a predetermined value or more, the fuel is returned to the fuel tank 42 to maintain the fuel pressure in the fuel injection valve 14 at a predetermined value. 49 and a relief valve 50 are connected.

In the fuel injection device of the present embodiment, the magnetic gap G of the fuel injection valve 14 is detected, and the fuel injection amount is detected so as to become the target injection amount obtained according to the operating state of the engine 20. Based on the magnetic gap G, the drive condition of the fuel injection valve 14, for example, the drive voltage value and the drive current value are corrected.

The detection of the magnetic gap is performed as follows. Ambient temperature of fuel injection valve 14 and magnetic gap G
The relationship with the size of is determined in advance by experiments. For example, as shown in FIG. 7, this has a characteristic that the magnetic gap increases in proportion to the ambient temperature. The ambient temperature-magnetic gap characteristic is stored in the memory 5 as a map value.

Then, in the operating state of the engine 20,
The CPU 1 reads the detected value of the temperature sensor 4 and obtains the magnetic gap corresponding to the detected temperature based on the map of FIG. In addition, at a position near the ambient temperature measurement point for obtaining the relationship between the ambient temperature and the magnetic cap in advance,
The temperature sensor 4 is arranged.

On the other hand, the correction of the driving condition of the fuel injection valve 14 is performed in the following manner. As shown in FIG. 8, when the magnetic gap of the fuel injection valve 14 is larger or smaller than the boundary value Go, the drive voltage V or the drive current I to the fuel injection valve 14 is increased.
Switch between large and small.

When the detected magnetic gap G is larger than the boundary value Go in the operating state of the engine 20, the drive voltage V and drive current I of the fuel injection valve 14 are controlled to large values. As a result, a sufficient driving force is obtained even when the magnetic gap is large, the fuel injection valve 14 operates normally, and the target injection amount is secured.

Various modes can be adopted as the method for correcting the driving condition. For example, as shown in FIG. 9, the injection amount correction coefficient K is corrected to be larger as the detected magnetic gap G is larger. Good. As a result, the fuel injection time is corrected to be longer than the injection time corresponding to the target injection amount obtained according to the operating state of the engine, and as a result, the target fuel injection amount is secured even when the magnetic gap is large. This is the invention of claim 5 of the present application.

Various methods can be adopted for the method of detecting the magnetic gap G, and the second method is shown in FIGS.
As shown in the embodiment, it is also possible to detect by the inductance of the electromagnetic coil 17 of the fuel injection valve 14, and this is the invention of claim 3 of the present application.

In the second embodiment, the magnetic gap G is obtained based on the inductance of the fuel injection valve 14. In order to obtain the inductance of the fuel injection valve 14, as shown in FIG. 10, a measuring circuit including a high frequency current generating circuit 8 and a voltage measuring circuit 7 is connected to both ends of the electromagnetic coil 17 of the fuel injection valve 14, and the electromagnetic coil is connected. A high-frequency current is supplied to 17 while the drive signal is low, and the voltage waveform (amplitude) across the electromagnetic coil 17 is measured.

In the above voltage waveform, when the magnetic gap is small, the inductance is large and the voltage amplitude is large (see FIG. 12A). When the magnetic gap is large, the inductance is small and the voltage amplitude is small. Nari (Fig. 1
2 (B)), the relationship between the magnetic gap and the inductance (voltage amplitude) is as shown in FIG. 11, and this relationship is stored in the memory 5 as a map.

While the engine is running, a high frequency current is passed from the high frequency current generating circuit 8 during the low period of the drive signal, the voltage amplitude (inductance) between terminals is measured by the voltage measuring circuit 7, and the inductance is calculated based on FIG. Find the magnetic gap. Then, the drive voltage and drive current are switched between large and small depending on whether the obtained magnetic gap is larger or smaller than the boundary value Go.

Further, as a method of measuring the above-mentioned inductor stance, as shown in FIG. 13, a method of obtaining it based on the rising waveform and the falling waveform of the drive current can be adopted. That is, when the magnetic gap is small, the inductance is large, and thus the rise time t is small. On the contrary, the larger the magnetic gap is, the smaller the inductance is, and thus the rise time t is large.

Therefore, by measuring the rise time t, the inductance and eventually the magnetic gap can be obtained. The drive voltage and the current may be switched between large and small depending on whether the magnetic gap is larger or smaller than the boundary value Go.

In order to ensure the operation of the fuel injection valve 14 even when the magnetic gap G becomes larger than the design allowable value, it is conceivable that the magnetic force has a sufficient margin. If there is a sufficient margin and the magnetic gap G varies toward the smaller side, there is a problem that the disappearance time of the magnetic force after the drive signal is turned off becomes longer and the return of the valve body 16 becomes worse. . In order to improve the return of the valve body 16, the return spring 18 may be strengthened.
The leeway in the magnetic force that causes this noise is offset. So after all,
The method of giving a margin to the magnetic force is not realistic.

[0042]

According to the engine fuel injection device of the first aspect of the invention, the magnetic gap of the fuel injection valve is detected and the drive condition is corrected based on the magnetic gap. Even if the magnetic gap of changes,
This has the effect of ensuring the target fuel injection amount adapted to the operating condition.

According to the invention of claim 2, since the magnetic gap is detected based on the temperature of the fuel injection valve,
The magnetic gap can be detected easily and accurately.

According to the third aspect of the invention, since the magnetic gap is detected based on the inductance of the fuel injection valve, since the electromagnetic coil and the armature itself form an inductance type displacement gauge, for example, There is no need for a new electrode as in the case where the inductance is detected by the change in the capacitance, and the structure is simple and the cost and size are advantageous.

According to the fourth aspect of the present invention, the drive voltage or drive current when the detected magnetic gap is large is made larger than the drive voltage or drive current when the magnetic gap is small. Therefore, the magnetic gap is large. Even in this case, the required driving force can be obtained, and the target amount of fuel can be injected and supplied.

According to the invention of claim 5, the fuel injection time when the detected magnetic gap is large is made longer than the fuel injection time when the magnetic gap is small, so that the magnetic gap is large and the driving force is small. Even in this case, the target amount of fuel can be injected and supplied.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a fuel injection device for an engine according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional side view of an engine including the device of the first embodiment.

FIG. 3 is a vertical sectional side view of the engine.

FIG. 4 is a bottom view of the cylinder head of the engine.

FIG. 5 is a vertical cross-sectional side view of the fuel injection valve of the first embodiment device.

FIG. 6 is a block diagram showing a fuel supply system of the first embodiment device.

FIG. 7 is an ambient temperature-magnetic gap characteristic diagram of the device of the first embodiment.

FIG. 8 is a magnetic gap-driving voltage / driving current characteristic diagram of the device of the first embodiment.

FIG. 9 is an injection amount correction coefficient-magnetic gap characteristic diagram according to a modified example of the first embodiment device.

FIG. 10 is a circuit diagram for measuring inductance according to a second embodiment of the present invention.

FIG. 11 is an inductance-magnetic gap characteristic diagram of the second embodiment device.

FIG. 12 is a diagram for explaining the inductance measuring method of the device of the second embodiment, wherein (A) is a drive signal when the magnetic gap is small, a waveform of the fuel injection valve terminal voltage, and a waveform showing the valve lift. FIG. 1B is a waveform diagram showing a voltage waveform when the magnetic gap is large.

FIG. 13 is a drive signal, current waveform, and valve lift waveform diagram for explaining a modified example of the inductance measuring method in the device of the second embodiment.

[Explanation of symbols]

 1 CPU (injection control means, correction means) 4 Temperature sensor (magnetic gap detection means) 14 Fuel injection valve 20 Engine 23a Combustion chamber G Magnetic gap

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02M 65/00 306 F02M 65/00 306A

Claims (5)

[Claims] 1. A fuel injection valve arranged to directly inject fuel into a combustion chamber, and the fuel injection valve so that the fuel injection amount is a target injection amount determined according to an operating state of the engine. A fuel injection device for an engine, comprising: an injection control unit for controlling; a magnetic gap detecting unit for detecting a magnetic gap of the fuel injection valve; and a fuel based on the magnetic cap so that the fuel injection amount becomes the target injection amount. A fuel injection device for an engine, comprising: a correction unit that corrects a driving condition of an injection valve. 2. The fuel injection device for an engine according to claim 1, wherein the magnetic gap detection means is configured to obtain the magnetic gap based on the temperature of the fuel injection valve. 3. The fuel injection device for an engine according to claim 1, wherein the magnetic gap detection means is configured to obtain the magnetic gap based on the inductance of the fuel injection valve. 4. The driving voltage or the driving current when the magnetic gap detected by the magnetic gap detecting means is large, and the driving voltage or the driving voltage when the magnetic gap is small, according to claim 1. An engine fuel injection device, characterized in that the correction is made to a side larger than the drive current. 5. The fuel injection time according to any one of claims 1 to 3, wherein the correction means has a longer fuel injection time when the magnetic gap detected by the magnetic gap detection means is larger than a fuel injection time when the magnetic gap is small. A fuel injection device for an engine, which is characterized by: