JPH0472991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an in-cylinder fuel injection device for an internal combustion engine (hereinafter referred to as engine), which includes an injector and a check valve.

(Prior art) As a conventional in-cylinder fuel injection device including an injector and a check valve, for example, Japanese Patent Application Laid-Open No. 58-72636
There is a publication. Such fuel injection devices have the following drawbacks.

(B) There is a limit (approximately 10) in controlling the ratio between the maximum fuel amount qfmax and the minimum fuel amount qfmin during the fuel injection time τ of the injector itself.

(b) It is difficult to measure small amounts of fuel with the injector.

(c) In addition to the injector itself generating heat, the heat from the cylinder head is transferred to the injector, causing the fuel between the injector and the check valve to vaporize, preventing sufficient fuel from being injected into the cylinder.

(d) Since high-pressure fuel (approximately 2.5 kg/cm ² ) is used, piping safety is low.

(e) When there is little fuel spray, such as during idling, the particle size of the spray becomes large, making idling unstable. Note that there is Japanese Unexamined Patent Publication No. 1987-74365 filed by the applicant as a prior document for the present application.

(Problems to be Solved by the Invention) This invention: (a) qfmax/qfmin in the fuel injection time τ is made larger than before.

(b) Possible to measure small amounts of fuel.

(c) The fuel between the injector and check valve does not vaporize even if it receives heat from the injector or the cylinder head.

(d) Low pressure fuel can be used.

(e) Even during idling operation, the spray particle size is reduced to stabilize idling operation.

(f) Make the spray particle size finer than before in all engine operating ranges.

The objective is to provide an in-cylinder fuel injection device.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides the following elements (a): A check valve chamber provided in the cylinder head of the engine and communicating with the combustion chamber of the cylinder via a valve hole.

(b) An electromagnetic check valve that opens and closes the valve hole.

(c) A fuel passage having a discharge port and a fuel throttle upstream thereof, and communicating the check valve chamber with the fuel pump via the discharge port.

(d) An air passage that communicates the fuel passage with the air pump between the fuel throttle and the discharge port, and has an air throttle.

(E) An electromagnetic fuel injector installed in the fuel passage upstream of the fuel throttle.

(f) An electric circuit that causes the check valve and the fuel injector to open synchronously during the intake stroke of the engine and close synchronously during the compression, explosion, and exhaust strokes of the engine.

(g) An air pressure Pa that is disposed in the air passage between the air throttle and the air pump and maintains the difference between the pressure in the engine intake passage and the pressure at one value set corresponding to each engine operating condition. Air regulator that generates.

(h) Disposed in the fuel passage between the injector and the fuel pump, it generates a fuel pressure Pf that maintains the difference between the pressure in the intake passage of the engine and the pressure at one value set corresponding to each operating condition of the engine. fuel regulator.

(li) An air amount sensor that detects the amount of air intake into the engine's intake passage and outputs a signal with a value corresponding to each amount of intake air.

(J) Input the signal value from the air amount sensor, and set the predetermined value Pa, corresponding to this signal value.
A computer that transmits the differential pressure with Pf.

(l) provided in at least one of the fuel passage and the air passage according to a signal from the computer;
A mechanism for maintaining the differential pressure mentioned above.

It consists of

(Operation of the Invention) In the above configuration, the amount of air taken into the intake passage of the engine is detected by the air amount sensor, and the air amount sensor sends a signal corresponding to the amount of intake air to the computer. The computer sets Pa−Pf=△ in advance according to the signal value from the air amount sensor.
P signal is sent to the differential pressure holding mechanism. As a result, the difference between the fuel pressure Pf in the fuel regulator, that is, at the fuel throttle, and the air pressure Pa, inside the air regulator, and that for the air throttle becomes constant, and the air and fuel having this constant pressure difference mix in the mixing chamber downstream of the air throttle. The primary air-fuel mixture flows into the check valve chamber through the discharge port and is injected into the combustion chamber of the cylinder through the valve hole of the check valve, which opens in synchronization with the opening of the injector during the intake stroke of the engine. The primary air-fuel mixture is mixed with intake air drawn into the cylinder from an intake valve of the engine to form a secondary air-fuel mixture, and this secondary air-fuel mixture is ignited by a spark plug.

(Description of Examples) Hereinafter, the present invention will be described based on drawings showing examples. First, the principle of this invention will be explained with reference to FIGS. 6 to 8. Reference numeral 1 indicates an intake cylinder for mixing air and fuel, and reference numeral 2 indicates a nozzle for mixing a fuel flow and an air flow within the intake cylinder 1. 5 is a fuel pump,
21 indicates an air pump. Also, symbol f indicates fuel, a
is air, SF is fuel throttle, Sa is air throttle,
S1 indicates a discharge port through which fuel and air are jetted, respectively. Now the pressure in intake cylinder 1 is P0, fuel pump 5
and the fuel and air pumped from the air pump 21.
Assuming that the pressures immediately before the fuel throttle Sf and the air throttle Sa are Pf and Pa, respectively, the amount of fuel and air jetted from the discharge port S1 depends on the differential pressure between the air pressure Pa and the fuel pressure Pf.

In other words, when the air pressure Pa exceeds a certain value, the fuel supplied from the fuel throttle Sf is stopped by the air flow supplied from the air throttle Sa, but the air pressure
As Pa is lowered below the above value, the amount of fuel supplied increases. Therefore, the fuel flow rate Gf ejected from the discharge port S1 changes almost linearly with Pa-Pf, as shown in FIG. 7, and reaches a maximum when Pa=Pf.
Further, the air flow rate Ga ejected from the discharge port S1 changes linearly as shown in FIG.

From Figures 7 and 8, in order to obtain a mixture with the optimum air-fuel ratio under each operating condition of the engine, the air flow rate Ga and fuel flow rate Gf must be adjusted to the air pressure Pa and the fuel pressure Pf.
It is necessary to control based on the difference Pa−Pf=ΔP.

This invention adjusts the fuel flow rate Gf according to engine operating conditions to a preset differential pressure between the fuel pressure Pf and the intake pressure P0 in the intake cylinder 1 under the operating conditions.
The air flow rate Ga is controlled by the fuel regulator based on Pf-P0=K2, and the differential pressure Pa-P0=K1 is set in advance according to the amount of air taken into the intake cylinder 1 during each engine operation. The air-fuel ratio of the air-fuel mixture in the combustion chamber of the cylinder, including the amount of air taken into the cylinder of the engine from the intake cylinder 1, is maintained at the optimum value for the operating conditions. ing.

Next, the present invention will be explained based on a first embodiment shown in FIGS. 1 to 4. Note that the same names as in FIG. 6 are given the same numbers for explanation. In Figure 1, 3
4 is a fuel tank, 4 is a fuel filter, and 5 is a fuel pump. 6 is a fuel regulator which is partitioned by a diaphragm 8 into a fuel chamber 7 and a negative pressure chamber 10, the negative pressure chamber 10 is communicated with the intake cylinder 1 through a negative pressure passage 16, and a compression spring 11 is accommodated in the chamber 10. ing. The fuel chamber 7 communicates with the fuel tank 3 via the fuel pump 5 and the fuel filter 4 through a fuel passage 55 . The diaphragm 8 has a fuel chamber 7
A valve 9 that protrudes inward is provided, and the tip of the valve 9 is connected to a return passage 19 in the fuel regulator 6.
opens and closes the return port 19a facing the fuel chamber 7. The return passage 19 communicates with the fuel tank 3. The fuel regulator 6 also has a plurality (four in FIG. 1, corresponding to the number of cylinders in the engine) of outlet ports 12 communicating with the fuel chamber 7.

Reference numeral 22 denotes an air regulator, which is partitioned into an air chamber 23 and a negative pressure chamber 28 by a diaphragm 24, and the air chamber 23 is connected to an air valve 38 in the intake cylinder 1 and a throttle valve 17 via an air pump 21 through an air passage 56. communicate between. The diaphragm 24 is provided with a valve 25 that projects into the air chamber 23, and the tip of the valve 25 opens and closes a release port 25a where the return passage 20 in the air regulator 22 faces the air chamber 23. The return passage 20 communicates between the air valve 38 in the intake cylinder 1 and the throttle valve 17. The air chamber 23 further has the same number of outlet ports 23a as the outlet ports 12 of the fuel regulator 6. Negative pressure chamber 2
8 has a retainer chamber 2 smaller in diameter than the negative pressure chamber 28.
8a, into which the retainer 32 is slidably inserted. A guide groove 31 is provided on the outer periphery of the retainer 32 in the axial direction of the retainer 32, and a guide piece 30 that engages with the guide groove 31 is provided to protrude into the retainer chamber 28a. A retainer 32 is provided in the negative pressure chamber 28.
A compression spring 29 is housed between the diaphragm 24 and the diaphragm 24 . The negative pressure chamber 28 communicates with the inside of the intake cylinder 1 via the negative pressure passages 16a and 16.

An electric actuator 33 is attached to the upper end of the air regulator 22, and its screw rod 34 is screwed into a screw hole 32a provided in the retainer 32.

An air valve 38 is attached to an eccentric shaft 39 rotatably attached to the intake cylinder 1. A fixed lever 41 is attached to the eccentric shaft 39, and the lever 41 is connected to a tension spring 40 attached to the intake cylinder 1. The rotation of the eccentric shaft 39 is transmitted to the rotation slider 42a of the variable resistor 42 via the coupling mechanism. 43 and 44 are terminals of the variable resistor 42 and the rotating slider 42a, respectively, and the wiring 4
5 and 46 are connected to the computer 35.

The computer 35 is connected to the electric actuator 33, and when receiving the output signal of the variable resistor 42 (this output signal is proportional to the amount of intake air passing through the air valve 38), the computer 35 is connected to the electric actuator 33, and when the computer 35 receives the output signal of the variable resistor 42 (this output signal is proportional to the amount of intake air passing through the air valve 38), a preset value is set for this output signal amount. The air pressure in the air chamber 23 of the air regulator 22 (hereinafter referred to as air pressure) Pa
A signal corresponding to the differential pressure ΔP between the fuel pressure (hereinafter referred to as fuel pressure) Pf in the fuel chamber 7 of the fuel regulator 6 is output to the electric actuator 33. The electric actuator 33 rotates the screw rod 34 by a signal amount corresponding to the differential pressure ΔP, thereby moving the retainer 32 up and down. Accordingly, the spring force of the compression spring 29 changes, the valve 25 moves via the diaphragm 24, and air is released from the release port 25a via the return passage 20 between the air valve 38 in the intake cylinder 1 and the throttle valve 17. The amount increases or decreases.

The intake pipe 1 communicates with each intake pipe 13 of the engine E via an air collection pipe 49. 36 indicates an intake port of engine E. The cylinder head 50 of the engine E is provided with a valve hole 52 that opens into the combustion chamber 51.
It is opened and closed by a.

An electromagnetic fuel injector 14 is provided in the cylinder head 50 adjacent to a check valve 57 . The fuel injector 14 communicates with the check valve chamber 59 and the valve hole 52 via a fuel passage 58 . The fuel passage 58 is provided with a discharge port 48 (corresponding to S1 in FIG. 6), and upstream thereof is a fuel throttle 4 that throttles the flow rate of fuel injected from the fuel injector.
7 is provided. Discharge port 48 and fuel throttle 47
A mixing chamber 60 is formed between the fuel injector 14 and the air nozzle 27 provided in the cylinder head 50 in the vicinity of the fuel injector 14 .
It communicates with the outlet port 23a of No. 2. The air nozzle 27 is provided with an air throttle 26. Note that the fuel injector 14 is connected to the fuel passage 53.
The outlet port 12 of the fuel regulator 6 is connected to the outlet port 12 of the fuel regulator 6 .

61 is a control unit, 62 is a crank angle sensor, 63 is a flywheel, and 64 is a distributor. The crank angle sensor 62 and the distributor 64 are connected to the control unit 60, and the control unit 60 is further connected to the fuel injector 14 and a reverse check. It is connected to valve 57. As shown in FIG. 3, the fuel injector 14 and check valve 57 open synchronously during the intake stroke of the engine, and close synchronously during the compression, explosion, and exhaust strokes. Note that the air regulator 22 is connected to the air passage 5.
4, air is supplied to the fuel passage 58 regardless of whether the check valve 57 is opened or closed.

In the configuration of the first embodiment, the air valve 38 rotates together with the eccentric shaft 39 while maintaining balance with the tension spring 40 depending on the intake air amount of the engine E. Along with this rotation, the rotation slider 42a rotates and the resistance value of the variable resistor 42 changes, and the amount of change is outputted to the computer 35 as an electric signal.
Note that the air flow rate sensor that outputs a signal with a value corresponding to each intake air amount directly measures the intake air flow rate using a hot wire flow rate measurement method, a discharge flow rate measurement method, a Karman vortex flow rate measurement method, etc. A method of deriving the amount of intake air may be used, or a method of measuring the amount of intake air based on engine parameters such as engine speed and intake pipe negative pressure may be used. Any method that can measure the intake air amount of the engine may be used. The air pressure of the air regulator 22 is preset in the computer 35 in accordance with this electric signal value.
Differential pressure △P between Pa and fuel pressure Pf of fuel regulator 6
A corresponding signal is output to the electric actuator 33. The electric actuator rotates the screw rod 34 by an amount corresponding to this signal, and as a result, the retainer 32, whose rotation is restricted by the guide piece 30 and the guide groove 31, moves in the vertical direction.
The spring force of the compression spring 29 on the diaphragm 24 changes. On the other hand, pressurized air from the air pump 21 presses the diaphragm 24 from the air chamber 23 side of the air regulator 22, but the total force of the intake negative pressure P0 acting on the negative pressure chamber 28 and the compression spring 29 balances with the air pressure Pa. The valve 25 is opened and closed to release excess air to the air valve 38 in the intake cylinder 1 and the throttle valve 1 via the release port 25a.
Release between 7 and 7. In this way, the air chamber 23
The air pressure Pa inside is Pa=P0+k1. here K1
is the pressure exerted by the compression spring 29.

On the other hand, the pressurized fuel from the fuel pump 5 presses the diaphragm 8 from the fuel chamber 7 side of the fuel regulator 6, but it opens and closes depending on the balance between the intake negative pressure P0 in the negative pressure chamber 10 and the spring force of the compression spring 11, and there is a surplus. The fuel is returned to the fuel tank 3 via the return passage 19. In this way, the fuel pressure Pf in the fuel chamber 7 of the fuel regulator 6 becomes Pf=P0+K2. Here, K2 is the pressure of the compression spring 11.

Therefore, Pa-Pf=K1-K2=ΔP, and ΔP is set in advance by the computer 35 with respect to the intake air amount to the intake cylinder 1 as described above.

As a result, the fuel at the fuel pressure Pf in the fuel chamber 7 of the fuel regulator 6 is fed under pressure to the injector 14 through the fuel passage 53, and is discharged into the mixing chamber 60 from the fuel throttle 47 during the intake stroke of the engine. On the other hand, the air pressure Pa in the air chamber 23 of the air regulator 22
The air passes through the air passage 54 and is discharged into the mixing chamber 60 from the air restrictor 26, but when passing through the air passage 54, the fuel flowing through the fuel passage 53 is prevented from being heated. Fuel and air are mixed in the mixing chamber 60 and discharged from the discharge port 4.
8 into the fuel passage 58. During the intake stroke of the engine, the valve element 57a of the check valve 57 opens the valve hole 52, so the air-fuel mixture (this is called the primary air-fuel mixture) flows into the combustion chamber 51 from the valve hole 52, and the air-fuel mixture flows into the combustion chamber 51 through the valve hole 52. mixed with intake air from
A mixture (referred to as a secondary mixture) having an air-fuel ratio optimal for each operating condition of the engine is formed, and the mixture is ignited by the ignition plug and combusted.

FIG. 4 shows an operational flowchart of the present invention. Upon starting the engine, in step 1,
It is determined whether the piston is at exhaust top dead center (TDC), and if it is determined to be at top dead center, it is determined in step 2 whether the cylinder is the NO1 cylinder. As a result of the judgment in step 2,
If it is the NO1 cylinder, the NO1 injector and NO1 check valve are opened in step 3. At this time, the engine E is in the intake stroke as described above, so the primary air-fuel mixture is injected into the combustion chamber 51. Incidentally, if it is determined in step 1 that the piston is not at the top dead center, the process directly proceeds to step 4.
Every time the crank angle is counted in step 4,
In step 5, it is determined whether the count value indicates the timing to close the intake valve, and steps 4 and 5 are performed until the count value of the crank angle reaches the timing to close the intake valve. In step 4, the crank angle is counted and when the specified rotation angle is reached, in step 6, the NO1 injector and NO1
The check valve closes and one cycle ends. No.2, No.
The same thing is done for the No. 3, No. 4 cylinder.

FIG. 5 shows a second embodiment of the invention. The difference between the second embodiment and the first embodiment is that the mixing chamber 60 of the first embodiment is shorter in the second embodiment, and the check valve chamber 59 of the first embodiment is shorter in the second embodiment. The reason for this is that the capacity has become smaller. The operation of the second embodiment is the same as that of the first embodiment.

(Effects of the Invention) Since the present invention has the above-described configuration, it has the following excellent effects.

(b) Approximately qfmax/qfmin at fuel injection time τ
Since it can be set up to 50, it is possible to set a fuel amount that has extremely low fuel consumption and allows stable operation for each operating condition of the engine.

(b) Even if the injector itself generates heat, or even if the injector is heated by the cylinder head, the fuel will not vaporize because the fuel injector has an air layer (mixing chamber 60). As a result, stable engine operation becomes possible.

(c) It becomes possible to use low-pressure fuel, reducing the risk of fuel leakage in piping, and increasing the safety of the fuel system.

(d) The particle size of the spray becomes finer than before in the entire operating range of the engine, resulting in less fuel consumption and stable engine operation. This also applies to idling operation.

[Brief explanation of drawings]

FIG. 1 shows a front view of a first embodiment of the invention. FIG. 2 shows a detailed view of the main part of FIG. 1. Third
The figure shows the operating timing of the check valve and fuel injector, and the supply status of fuel and air, and FIG. 4 shows a flowchart of the operation of the present invention. FIG. 5 shows a detailed view of the main parts of a second embodiment of the invention. FIG. 6 is an explanatory diagram of the operating principle of this invention. 7 and 8 are explanatory diagrams of the air flow rate and fuel flow rate in FIG. 6, respectively. 5...Fuel pump, 6...Fuel regulator,
14...Electromagnetic fuel injector, 21...Air pump, 22...Air regulator, 26...Air throttle, 33...Electric actuator (Pa-Pf
(mechanism for holding the value at a predetermined value), 35...computer, 42...variable resistor (air amount sensor), 47
... Fuel throttle, 48 ... Discharge port, 52 ... Valve port,
53...Fuel passage, 54...Air passage, 57...
Solenoid check valve.

Claims (1)

[Scope of Claims] 1. The following elements (a): A check valve chamber provided in the cylinder head of the engine and communicating with the combustion chamber of the cylinder via a valve hole. (b) An electromagnetic check valve that opens and closes the valve hole. (c) A fuel passage having a discharge port and a fuel throttle upstream thereof, and communicating the check valve chamber with the fuel pump via the discharge port. (d) An air passage that communicates the fuel passage with the air pump between the fuel throttle and the discharge port, and has an air throttle. (E) An electromagnetic fuel injector installed in the fuel passage upstream of the fuel throttle. (f) An electric circuit that causes the check valve and the fuel injector to open synchronously during the intake stroke of the engine and close synchronously during the compression, explosion, and exhaust strokes of the engine. (g) An air pressure Pa that is disposed in the air passage between the air throttle and the air pump and maintains the difference between the pressure in the engine intake passage and the pressure at one value set corresponding to each engine operating condition. Air regulator that generates. (h) Disposed in the fuel passage between the injector and the fuel pump, it generates a fuel pressure Pf that maintains the difference between the pressure in the intake passage of the engine and the pressure at one value set corresponding to each operating condition of the engine. fuel regulator. (li) An air amount sensor that detects the amount of air intake into the engine's intake passage and outputs a signal with a value corresponding to each amount of intake air. (J) Input the signal value from the air amount sensor, and set the predetermined value Pa, corresponding to this signal value.
A computer that transmits the differential pressure with Pf. (l) provided in at least one of the fuel passage and the air passage according to a signal from the computer;
A mechanism for maintaining the differential pressure mentioned above. An in-cylinder fuel injection device comprising: