Fuel Injection Device For Internal Combustion Engines

Abstract

Electrical signals representing the revolutions, load, temperature and acceleration of the revolutions of the internal combustion engine are detected and introduced into a controller, the output of which is used to actuate a servo motor or electromagnetic valve, whereby the time at which the fuel injection pump starts operating is controlled, thus preventing any undesirable combustion products from being produced.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an fuel injection device for internal combustion engines, or more in particular to an apparatus for controlling the time at which the fuel injection pump starts to inject fuel.

2. Description of the Prior Art

In the conventional fuel injection device, the time at which the fuel injection pump starts to inject fuel is controlled by mechanically detecting only the revolutions of the engine involved. In such a device, it is common practice to make arrangements in such a manner that the most appropriate fuel injection time is achieved either under the full or partial load (including the absence of the load). If, however, arrangements are made to obtain the most appropriate injection starting time under the full load, combustion noise occurs under a partial load, while if the best fuel injection time is determined in accordance with the time when the engine is partially loaded, the shortage of output will result under a full load. To cope with this problem, a new method is suggested in which the time at which fuel injection starts is controlled by utilizing not only the revolutions of the engine but also the load of the engine, particularly the pressure due to spilled fuel responsive to the amount of fuel injected (See, for example, Japanese Patent Publication No. 19367/66). This can be said to be a success, at least provisionally, in that noise is eliminated under a partial load without reducing the output under a full load, but the disadvantage of this type of device is that it not only requires a highly complicated construction of a hydraulic circuit but it cannot meet the demand, if any, for highly complicated characteristics of the timing of the starting of fuel injection. It is known that generation of the combustion products such as CH and NOx depends on the temperature and pressure in the combustion chamber, which in turn are greatly affected by the time at which injection of the fuel commences. Therefore, to prevent the generation of undesirable combustion products, the temperature and other factors of the combustion in the chamber should be added to control the time at which injection of the fuel commences. In this respect, the device mentioned above leaves something to be desired, because in such a device only the amount of fuel injected and revolutions are detected for the purpose of controlling the time at which injection of the fuel commences. Further, the addition of the temperature to the factors for controlling the same complicates still more the hydraulic circuit, making it very difficult to prevent the generation of undesirable combustion products.

SUMMARY OF THE INVENTION

This invention is intended primarily to prevent the generation of harmful combustion products and is so constructed that electrical signals representing the revolutions, load, temperature and acceleration of the revolutions of the internal combustion engine are detected and introduced into a controller, the output of which is used to actuate a servo motor or electromagnetic valve, whereby the time at which the fuel injection pump starts its operation is controlled, thus preventing any undesirable combustion products from being generated. Also, according to the invention no combustion noise occurs under the partial load, nor is there any shortage of output under the full load, while at the same time simplifying the construction of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a partial section of an embodiment of the invention.

FIG. 2 is a diagram showing a partial sectional view of another embodiment of the invention.

FIG. 3 is a diagram showing the construction of a third embodiment of this invention.

FIG. 4 is a block diagram showing a computer employed in the embodiments of FIGS. 1 and 2.

FIG. 5 is a diagram showing a partial sectional view of a fourth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be now explained with reference to the embodiments of FIGS. 1 and 2. First referring to FIG. 1, with the rotation of a drive shaft 1 connected to the crank shaft of the engine, a cam shaft 2 of the injection pump rotates through a nut coupling 3. Then an eccentric cam 4 fixed on the cam shaft 2 rotates, which causes the plunger 5 to reciprocate against the force of a coiled spring 6. Fuel in a suction chamber 7 is absorbed into a plunger chamber 8 and, through the path 9, introduced into an injection nozzle, from which it is injected into the combustion chamber of the engine, while the cut off fuel enters the chamber 11. The plunger 5 is rotated by moving the rack 13 which engages with the gear 12 provided in the plunger 5, whereby it is possible to change the time at which the double-flow path 14 is opened, said path 14 maintaining a local relationship with the slanted control edge 15 in the plunger 5, so that the amount of fuel injected from the injection nozzle 10 can be increased or decreased. The opposing ends of the drive shaft 1 and the cam shaft 2 respectively are provided with screws 16 and 17, which are received by the nut 3 for integrally rotating with the drive shaft 1 and the cam shaft 2. when the nut 3 is moved axially, the cam shaft 2 rotates with respect to the drive shaft 1. A worm 18 is fixed on the shaft of the servo motor M and engages with a piece 19. One side of the piece 19 engages with the nut 3 in such a manner that the nut 3 is not prevented from rotating but prevented from moving axially with respect to the piece 19. The reference numeral 20 shows a housing. The symbol C shows a controller, which issues an order for rotating the servo motor M. The controller C is provided for the purpose of accurately discerning the over-all engine conditions detected in the form of electrical signals representing the revolutions N, load L, temperature T and rotational acceleration a and of determining the magnitude of output to be transmitted to the servo motor M.

In the above-described construction, the electrical signals separately detected and representing the engine revolutions N, load L, temperature T and the acceleration of revolutions .alpha. are applied to the controller C, the output of which rotates the servo motor M. The worm 18 fixed on the servo motor M then rotates, thereby moving in the axial direction the piece 19 engaging with the worm 18. With the movement of the piece 19 in the axial direction, the nut 3 moves also in the axial direction while rotating. The drive shaft 1 and the cam shaft 2 rotate in opposed relationship by way of the screws 16 and 17 formed thereon, thereby positioning the cam shaft 2 and hence the cam 4 fixed thereon in a new relationship with respect to the drive shaft 1, setting a new time point of the rise of plunger 5 and thence a new time point at which fuel injection starts.

In FIGS. 2 and 3 showing a part of the fuel injection pump of the distribution type, the numeral 30 shows a housing, and 21 an annular roller holder with a channel-shaped section and rotatable with respect to the housing 30. A roller 22 is rotatably arranged on the roller holder 21 by means of a support 23. The peripheral portion of the roller 22 is in contact with the surface of the cam 32 provided on the skirt of the plunger 31 shown in FIG. 3. With the rotation of the drive shaft, the plunger 31 rotates, whereby the cam 32 rotates on the roller 22, causing the plunger 31 to reciprocate. Fuel is then sucked in and the injected cut-off fuel is returned to the fuel tank. The reference numeral 24 shows a piston chamber occupying a portion of the housing 30 and which is fitted with the piston 25 slidably in the piston chamber 24. The operating chamber 2 between an end of the piston 25 and an end of the piston chamber 24 is fitted with a compression spring 26. A hydraulic chamber 24b is formed on that side of the piston chamber 24 which is opposite to the side thereof fitted with the compression spring 26. The hydraulic chamber 24b is connected with the oil ducts 27a and 27b. The piston 25 rotates around the pin 28 and is connected with an end of the lever 29, the other end of which is in turn coupled with the roller holder 21. The symbol V shows an electromagnetic valve which functions to change the cross sectional area of the oil duct 27a, and the numeral 27b' shows a throttle section for the duct 27b. The electromagnetic valve V may be provided only in the duct 27a or both in the ducts 27a and 27b. In the event that the electromagnetic valve V is provided in the oil duct 27b, the throttle is arranged in the oil duct 27a. To the electromagnetic valve V is applied the output of the controller C as explained with reference to the embodiment of FIG. 1, while electrical signals representing the revolutions N of the engine, load L, temperature T and acceleration of revolutions .alpha. are applied to the controller C. Fuel cut off by the oil duct 27a or 27b may be introduced into the hydraulic chamber 24b, or as an alternative another kind of fluid may be introduced to the same by means of a separate pump.

In the above-described device, like the embodiment of FIG. 1, the electromagnetic valve V is energized in accordance with the variations in the output of the controller C, whereby the cross sectional area of the oil duct 27a and hence the hydraulic pressure inside the chamber 24b is changed, with the result that the piston 25 moves to the extent that the hydraulic pressure is in equilibrium with the force of the spring 26. The movement of piston 25 causes the lever 29 to rotate around the pin 28, resulting in the roller holder 21 for rotating relatively with respect to the housing 30. This causes a change in the spaced relationship between the cam of the plunger and the roller 22, which in turn changes the time at which the plunger begins to rise, that is, the time at which fuel begins to be injected. The compression spring 26 arranged in the operating chamber 24a in the above-described embodiment may be replaced with fluid as in the hydraulic chamber 24b. In such a case, the operating chamber 24a, like the hydraulic chamber 24b, is fitted with oil ducts and an electromagnetic valve. Further, the controlling factors to be employed are not limited to those employed in the above-described embodiments including the revolutions of the engine, load, temperature, and acceleration of revolutions. For example, they may be limited to the revolutions and load if there is no need fo taking measures against exhaust gases.

An actual example of the fuel injection pump of the distribution type according to the invention will be now explained with reference to FIG. 3. The reference numeral 30 shows a pump housing, 33 a cam shaft, and 22 a roller independent of the cam shaft 33 and rotatably supported on the roller holder 21 which is in turn mounted rotatably on the pump housing. The numeral 31 shows a plunger integral with the cam plate 32, so that both the cam plate 32 and the plunger 31 rotate integrally with the cam shaft 33. The cam surface of the cam plate 32 is in contact with the peripheral portion of the roller 22. The numeral 34 shows a slider which is movable in the direction of the axis of the plunger 31, and with the movement of the slider 34, an opening 31b of the fuel path 31a provided on the plunger 31 may be closed or opened. The numerals 35 and 36 show outlet paths for pressing into a not-shown injection nozzle the fuel sucked into the fuel path 31a and the plunger 38 from the fuel inlet 37. The period during which the fuel is pressed into the rejection nozzle continues, for example, from the time when the outlet path 36 begins to communicate with the notch 31c as shown in the drawing to the time when the opening 31b of the plunger 31 is positioned to its opened state at the right side of the slider 34. The numeral 39 shows an adjusting pin which is rotatable around the support pin 40 in a plane perpendicular to the paper surface. When the pin 39 rotates in the plane as mentioned above, the roller holder 21 also rotates around the axis of cam shaft 33 in a plane perpendicular to the paper surface. As a result, the spaced relationship between the roller 22 and the cam plate 32 changes, while at the same time changing the time at which the plunger begins to move upward, hence, the time of injection. The numeral 24 shows a cylinder formed in the pump housing 30 and fitted with a slidable piston 25. The numeral 41 shows a fuel pump, from which the fuel is supplied through the electromagnetic suction valve 42a to the hydraulic chamber 43 comprised of the cylinder 24 and the piston 25. The electromagnetic valve 42a is interposed between the hydraulic chamber 43 and the suction system of the fuel pump 41. Fuel is supplied to the hydraulic chamber 43 through the path 42a' by opening the electromagnetic valve 42a. The numeral 42b shows electromagnetic draining valve interposed between the hydraulic chamber 43 and the fuel tank 44. When the electromagnetic valve 42b is opened, the fuel in the hydraulic chamber 43 is drained through the path 42b' to the fuel tank 44. The numeral 45 shows an engine revolutions detecting gear fixed on the cam shaft 33, and this gear is placed opposed to the electromagnetic pickup fixed on the pump housing 30. The numeral 47 shows an engine revolutions detector which performs not only the engine revolutions detecting operation but differentiation in response to signals from the electromagnetic pickup for deciding whether or not the rotation of the engine is being accelerated. The numeral 48 shows an adjusting lever interlocked with the axle lever in the driver's compartment and is rotatable in the direction of arrow A or B around the supporting point 49. One end of the adjusting lever 48 engages with the slider 34, while the other end thereof is coupled with the rod of the differential transformer 50. Because of this construction, operating the axle lever in accordance with the load condition causes the slider 34 to move in the direction of the axis of the plunger 31 by means of the adjusting lever 48, whereupon the amount of injection changes, resulting in the change in output voltage of the differential transformer 50. The numeral 51 shows a position detector, which produces an output proportional to the output of the differential transformer 50. The numeral 52 shows an engine cylinder, 53 a thermistor and 54 a temperature detector for detecting the temperature in the cylinder in the form of voltage variations which result from the variations in the combustion temperature in the cylinder 52. The numeral 55 shows a transmitter to which the outputs of the revolution detector 47, position detector 51 and the temperature detector 54 are applied, and which produces an output for actuating the electromagnetic valves 42a and 42b.

The operation of the device according to the invention will be now explained with reference to the block diagram shown in FIG. 4.

An AC waveform detected by the elactromagnetic pickup 101 is shaped by the shaper 102 and applied to the D-A converter 103 where it is transformed into an analog value, thereby producing a voltage V.sub.1 proportional to the revolutions of the engine. The voltage proportional to the engine revolutions is applied to a differentiating circuit 105 for detecting the voltage V.sub.2 which is produced in response to the acceleration and deceleration of the engine.

It is possible to detect the temperature change in the cylinder by means of the thermistor 106 directly in the form of voltage variations, which are amplified by the amplifier 107 to produce a voltage V.sub.3 proportional to the temperature. As to the engine load, an AC voltage proportional to the load is produced by the differential transformer 108 excited as above, and this AC voltage is rectified by the rectifier 109 for producing a DC voltage proportional to the load.

In this way, the engine revolutions W, engine acceleration or deceleration dN/ dt, engine combustion chamber temperature T and load X are obtained in the form of output voltages V.sub.1, V.sub.2, V.sub.3 and V.sub.4 respectively, which are operated in the operational unit 110 to obtain the output voltages V.sub.10, V.sub.20, V.sub.30 and V.sub.40 representing the above-described control factors respectively. These voltages are applied to the adder 120 where they are added together and then applied to the comparator 130 where the sum V is identified. In the event of V being larger than zero, a voltage is applied to the electromagnetic suction valve 42a to open the same, whereupon fuel is supplied to the hydraulic chamber 43 thereby advancing the piston 25 in a forward angular direction, whereas if V is smaller than zero, a voltage is applied to the electromagnetic draining valve 42b to open the same, whereupon the fuel in the hydraulic chamber 43 is drained thereby actuating the piston 25 in such a direction as not to advance the same in a forward angular direction.

The controlling of the injection time in the above-mentioned manner permits not only the phase angle to be advanced in order to secure the engine power proportional to the engine revolutions as in the conventional method, but the injection time to be delayed by detecting the high rate of engine acceleration in order to reduce the noise of engine combustion and control undesirable exhaust which results from the increase in combustion temperature. Further, by detecting the engine load and delaying the injection time under partial load condition, it is possible to reduce combustion noise. Also, when the combustion temperature is abnormally high, undesirable exhaust can be reduced by delaying the injection time. Thus it is possible to obtain an automatic injection time regulator which makes possible fuel to be injected in the most appropriate timing taking into consideration the engine output, noise and exhaust.

Instead of the two electromagnetic valves 42a and 42b for suction and draining respectively provided in the above-described embodiment for operation of the piston 25, a single electromagnetic valve may be employed as shown in FIG. 2. Also, as an alternative method to operate the piston 25, the servo motor M may be used for the mechanical operation thereof as shown in FIG. 5. Of course, the electromagnetic valves may be replaced by such a control element as a servo valve.

It will be understood from the above description that, according to the present invention, such control factors as revolutions N, load L, temperature T and acceleration of revolutions .alpha. are introduced into the controller C, the output of which is used to actuate the servo motor M or the electromagnetic valve V in order to change the time at which fuel starts to be injected. Accordingly, in view of the fact that miniature electronic equipment can be manufactured with relative ease at present, the invention makes the whole device more compact and makes possible a better response than if a fluid is used to perform control operations mechanically as in the conventional devices.

Claims

What is claimed is:

1. A fuel injection device for an internal combustion engine having a pump means for injecting high pressure fuel into each engine cylinder, a pump driving means connected with said engine for driving said pump means by said engine and a connecting means provided between said pump means and said pump driving means for connecting said pump means with said pump driving means to be able to change the relative position of the pump driving shaft to the engine crank shaft so as to change the fuel injection timing of said pump means comprising:

detector means installed in said engine for detecting at least three engine parameters including the number of revolutions of the engine, the actual combustion temperature in the cylinder and the acceleration of the engine as measured by the rate of change of engine revolutions with time and for producing electrical signals representing said engine parameters;

a controller coupled with said detector means for performing logical operations on the output signal of said detector means and for producing an output signal when the total value of said engine parameters meets a predetermined value; and

means connected with said connecting means and said controller for driving said connecting means so as to change said relative position of said pump driving shaft to said engine crank shaft, thereby changing said fuel injection timing.

2. A fuel injection device for an internal combustion engine as defined in claim 1 wherein said connecting means comprises a first screw formed at one end of said pump driving shaft, a second screw formed at one end of a drive shaft connected with said engine crank shaft, a nut engaged with said first and second screws for changing the relative position of said pump driving shaft to said drive shaft by the axial movement thereof, a piece engaged with said nut and provided with teeth on one side thereof for driving said nut axially, a worm engaged with said teeth for driving said piece axially, and an electric motor connected with said controller for driving said worm in response to the output signal of said controller.

3. A fuel injection device for an internal combustion engine as defined in claim 1 wherein said pump means is a distributor type; said connecting means has at least a rotatable roller holder for changing the fuel injection timing; and said driving means comprises a piston biased by a spring and connected with said roller holder, a fluid chamber formed on one side of said piston and connected with a suction passage and a drain passage for moving said piston by the fluid therein, a first electromagnetic valve installed at said suction passage for charging the fluid into said fluid chamber in response to the output signal of said controller and a second electromagnetic valve installed at said drain passage for draining the fluid from said fluid chamber in response to the output signal from said controller.

4. A fuel device for an internal combustion engine as defined in claim 1 wherein said pump means is a distributor type; said connecting means has at least a rotatable roller holder for changing the fuel injection timing; and said driving means comprises a piston biased by a spring and connected with said roller holder, and an electric motor whose shaft is connected with said piston for driving said piston in response to the output signal of said controller.

5. A fuel injection device for an internal combustion engine as defined in claim 1 wherein said pump means is a distributor type; said connecting means has at least a rotatable roller holder for changing the fuel injection timing; and said driving means comprises a piston biased by a spring and connected with said roller holder, a fluid chamber formed on one side of said piston and connected with a suction passage and a drain passage for moving said piston by the fluid therein, and an electromagnetic valve installed at either of said pipes for transferring the fluid in said fluid chamber in response to the output signal of said controller.

6. A fuel injection device for an internal combustion engine as defined in claim 1 wherein said detector means further detects engine load and produces an electrical signal representing the engine load.

7. A fuel injection device for an internal combustion engine as defined in claim 2 wherein said detector means further detects engine load and produces an electrical signal representing the engine load.

8. A fuel injection device for an internal combustion engine as defined in claim 3 wherein said detector further detects engine load and produces an electrical signal representing the engine load.

9. A fuel injection device for an internal combustion engine as defined in claim 4 wherein said detector further detects engine load and produces an electrical signal representing the engine load.

10. A fuel injection device for an internal combustion engine as defined in claim 5 wherein said detector further detects engine load and produces an electrical signal representing the engine load.