GB2242229A - I.c. engine measuring piston fuel injection - Google Patents

Abstract

The position of a measuring piston 13 in an intake injector is detected to control an electromagnet coil 7 which operates valves 2, 23 to determine the stroke and timing of piston motion and thereby the quantity and timing of fuel injection through the valve 8. With the coil 7 energised fuel under pressure from the chamber 4 flows to the piston chamber 26 and through the piston passage 13 or a by-pass (28, Fig. 2) to the supply reservoir. This flow provides injected cooling and removal of vapour. <IMAGE>

Description

1 r 1 ELECTROMAGNETIC IN-JECMON VALVE The invention relates to an

electromagnetic injection valve for delivering fuel into an induction passage or pipe leading to one or more cylin ders of an internal combustion engine. And the invention is concerned with the type of fuel injection valve which is equipped with electronically controlled fuel metering means and in which fuel leaves the valve into the induction passage or pipe through an atomizer or blow valve which extends into the induction pipe or passage. Such an electromagnetic fuel injection valve will be controllable by electronic control means so that fuel is injected at predetermined times and at predetermined rates.

In multi-cylinder engines, the induction passages leading to the respective cylinders may lead from a common chamber equipped with a single such injection valve. More usually however the induction passages leading to the individual cylinders are separate from one another, and each passage or pipe is equipped with its own individual fuel injection valve. The invention is concerned with a valve for use in both instances.

However in the case where the engine is equipped with separate induction pipes, one for each cylinder and each with its own injection valve of the type being discussed, that is a valve having fuel metering means, it is desirable if the metering performance and characteristic of the plural valves fitted to the engine is identical or nearly so, as otherwise unequal quantities of fuel might be fed to the different cylinders leading to uneven combustion with the consequence of risk of exhaust gas contamination.

An injection valve of this kind is, for example, the subject of DE-Al 25 01283. Although the device there described has as its object to provide satisfactory preparation of the fuel and relatively accurate fuel metering, satisfactory operation is ensured only in a single, or one point, injection valve installation, and in the case where multiple valves are installed, 2 with each valve feeding its own separate induction passage, there is a risk of variation in the operating characteristics of the various valves, whereby unequal quantities of fuel are injected into the separate induction pipes. As a result, uneven combustion with the known consequence of exhaust gas contamination can occur. Accordingly, the object of the invention is to provide, particularly but not exclusively for multi-valve installations, a fuel injection valve so constructed and arranged that any variation in its operating characteristics has at most, only an insignificant effect upon the operation of the engine. This object is achieved by the features set forth in claim 1. Advantageous developments of the subject of claim 1 are set forth in the subsidiary claims.

Broadly stated, this invention provides an electromagnetic injection valve for delivering fuel into the induction passage or pipe of an internal combustion engine by way of an atomizer forming part of the injection valve but located in the induction passage, the injected fuel being driven through the atomizer ahead of a piston moving in a measuring cylinder, and there being means for detecting and monitoring the movements of the piston as it travels back and forth in the cylinder, the travel of the piston during each injection phase corresponding to the amount of fuel displaced through the atomizer, the detector means providing signals for an electronic control circuit which times the injection phases and the intervals between these phases during the operation of the electromagnetic fuel injection valve.

Preferably, the injection valve includes a fuel distribution valve which has a first switching position in which a portion of the measuring cylinder in communication with the atomizer on one side of the piston, is connected to a fuel supply system, while a measuring cylinder portion on the other side of the piston is connected to a fuel discharge system; and the distribution valve having a second switching position in which the last-mentioned measuring cylinder portion is connected to the fuel supply system and the other measuring cylinder portion disconnected from the fuel supply system; j 3 1 1 the piston being moved due to fuel pressure differences occurring on its opposite sides during these phases, such piston movements being monitored by the detector means which provides signals for the control circuit.

One embodiment of the invention is shown by way of example in the drawings, in which: Figure 1 is a diagram showing in transverse crosssection the construction of an injection valve in accordance with the invention in conjunction with a fuel supply and discharge system; Figure 2 shows an alternative construction of the injection valve of Figure 1.

In the description which follows, the words "upper" and "lower" are used to refer to the valve in its disposition as illustrated in the drawing.

In Figure 1, an electromagnetic injection valve 1, includes a fuel distribution valve generally designated 2 which is fed from a chamber 4 containing fuel under pressure derived from a fuel supply system 3. The valve 1 has an armature 6 forming part of a valve member generally designated 5 which may be displaced against spring force by an electromagnetic coil system 7. 'Me valve member 5 has a central through bore leading to a chamber 10 (in the disposition of parts as shown). The armature 6 of the valve member 5 is accommodated in an armature guide 15 and its upper end extends into the pressure chamber 4 and its other, lower, end extends into a relief chamber 16 which is connected by way a fuel discharge line 17 which leads back to the fuel tank (not shown).

The valve member 5 has a spring-loaded collar 18, so that a lower end face 19 of the valve member 5 is urged against a flat scat 20 surrounding an open central bore leading into chamber 10, which is closed off relative to the relief chamber 16 when the end face 19 abuts the seat 20. The upper end of the valve member 5 which extends into the pressure chamber 4 cooperates by i 4 means of an upper end face 21 with a sealing surface-1.2 of a fixed spigot when the magnetic forces are operating.

When this occurs, a spring-loaded valve plate 23 is lifted by a further collar 24 of the valve member 5 so that a passage 25 is connected with the pressure chamber 4, while the central bore through the valve member 5 is closed off from communication with the pressure chamber 4.

The lower end of the injection valve 1 extends into an induction pipe or passage leading by way of an inlet valve to a cylinder combustion chamber of an internal combustion engine, the valve 1 terminating in an atomizer 9 and upstream of this, in terms of fuel flow, a blow valve 8.

A fuel measuring system generally designated 11 is disposed in the chamber 10 extending between the distribution valve 2 and the atomizer 9 and is formed by a measuring cylinder 12 and movable within this, a free piston 13. Movement of the free piston 13 is detected by a travel- detection system 14 which operates with laser beam, ultrasonics, induction or capacitance and whose values are fed to and processed in an electronic control unit (not shown) forming part of the electronic management system of the internal combustion engine, the control unit supplying the operating current to the electromagnetic coil system 7 according to a predetermined program.

The free piston 13 divides the measuring cylinder 12 of chamber 10, into, on the one hand, a lower measuring cylinder portion 26 which communicates with the passage 25 and with the blow valve 8 and the atomizer 9, and on the other hand, an upper measuring cylinder portion 27 which is connected, in dependence upon which of its two possible switching positions the valve member 5 has assumed, either to the relief chamber 16, or to the supply of fuel under pressure in the chamber 4. The connecting passage 25 has a throttle portion 3 1.

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1 i J The embodiment of Figure 1 shows that the free piston 13 has a by-pass passage 28 with a spring loaded valve 29, upwards movement of the free piston 13 being limited by a stop shoulder 30. Figure 2 shows an alternative arrangement of the by-pass passage, which in this case is disposed in the housing wall of the valve. Here, when the valve member 5 is in its lower switching position, the by-pass passage 28' is closed relative to the relief chamber 16 by the end face 19 of the valve member 5 abutting with the fixed seat 20; and this will occur even in a further alternative arrangement where, as is shown by broken lines, the passage 28' opens into the upper measuring cylinder portion 27. The free piston 13 is hydraulically locked (the pressures on its opposite sides being equal) when the by-pass passage 28' is open, this being discussed in detail in the following description of the fimction.

When the injection valve 1 in accordance with the invention is installed in a multi-cylinder internal combustion engine with each induction pipe leading to a cylinder combustion chamber having its own injection valve 1, sequential and selective injection related to the designated engine cylinder firing order will be obtained and controlled by the abovementioned electronic contr ol unit forming part of the engine management system and all in accordance with a given program. The electronic control unit supplies the individual injection valves with current which activates the electromagnetic coil system 7 to switch the valve 5 between its two positions, the timing of the supply of current being fully controlled.

The fuel supply 3 comprises a fuel pump, a pressure regulator and a return passage to the fuel tank (not illustrated) and makes available fuel at a predetermined pressure in the pressure chamber 4. The level of pressure in the discharge line leading back to the fuel tank is much lower than that of the fuel in chamber 4.

6 In the illustrated embodiment of the injection valve, injection into the injection pipe is always effected when the electromagnetic system 7 is non-energized, ie, in the phase of injection, the components will be in their positions as is shown in Figure 1. In this phase, the passage 25 and the by-pass passage 28 are both closed, and the bore through the valve member 5 being open, the upper measuring cylinder portion 27 is subjected to the (relatively high) pressure of the fuel located in the pressure chamber 4. This pressure acts upon the free piston 13, so that the latter presses downwardly against the fuel contained in the lower measuring cylinder portion 26. Since this fuel cannot flow off through the closed-off passage 25 or through the by-pass passage 28 (the valve 29 being closed at this stage), the pressure increases to a value at which the blow valve 8 is opened whereupon fuel is injected by way of the atomizer 9. As that happens, the pressure in the lower measuring cylinder portion 26 no longer increases, so that the quantity of fuel delivered into the upper measuring portion 27 does not lead to an increase in pressure, but instead displaces the free piston 13, moving it downwardly into the measuring cylinder portion 26 (the valve 29 still being closed).

Advantageously, the free piston 13 is made from a material of approximately the same density as that of the fuel and no appreciable leakages occur (from upper chamber portion 27 to lower chamber portion 26) during this displacement, it being noted that no difference in pressure will exist between the measuring cylinder portions 26, 27. The quantity of fuel displaced during the displacement of the free piston 13 into the measuring portion 26 corresponds to the travel of the free piston 13.

This travel is continuously detected by the travel-detection system 14 and is fed as a signal to the electronic control unit and is processed therein until the predetermined quantity of fuel to be injected is obtained, whereupon a signal is supplied to the electromagnetic system 7. The valve member 5 then moves to its alternative (raised) operative position against spring pressure.

tll 7 The armature 6 or the valve member 5 is then raised against the spring force and its end face 21 is urged against the sealing surface 22 of the spigot, this closing off the central bore of the valve member 5. At the same time, the. collar 24 of the rising valve member 5 lifts the valve plate 23, and the end face 19 of the valve member 5 moves away from sealing contact with the flat seat 20, so that now, while the upper measuring cylinder portion 27 is connected to the relief chamber 16, the lower measuring cylinder portion 26 is connected to the pressure chamber 4 by way of the passage 25.

When the upper measuring cylinder portion 27 is placed in communication with the relief chamber 16, it is thereby connected to the fuel discharge system 17. In this location there prevails a lower pressure than in the pressure chamber 4 and a lower pressure than that required for opening of the blow valve 8. As a result, the pressure in the lower measuring portion 26 now drops abruptly, so that the blow valve 8 closes and injection of fuel by way of the atomizer ceases abruptly. Fuel is then forced out of the pressure chamber 4 and into the portion 26 by way of the now open passage 25, so that the lower side of the free piston 13 is loaded and it is moved upwardly into the upper measuring portion 27 connected to the relief chamber 16. This upward movement continues until in the embodiment shown in Figure 1, the free piston 13 comes into abutment against the stop shoulder 30, thus defining its "dead" position. When in this dead position, the pressure still increases in the lower portion 26, and eventually this pressure increase is effective to open the differential pressure valve 29 (in the free piston 13) whose set opening pressure is lower than that of the blow valve 8.

When the valve 29 opens, fuel can flow out of the pressure chamber 4 and into the relief chamber 16 by way of the by-pass passage 28 in the free piston 13. This flow scavenges the injection valve 1, whereby hot fuel and vapour bubbles, which are possibly formed, are discharged by way of the fuel discharge system 17.

8 In the construction of Figure 2, the by-pass passage.98' is disposed in the housing wall of the valve. The by-pass passage 28' is opened when the lower side of free piston 13 is loaded and moved upwardly by the rising pressure. Eventually, pressure drops abruptly and the displacement is terminated, the "dead" position being reached when the piston 13 is hydraulically locked.

Since the connecting passage 25 is throttled relative to the by-pass passage 28' by the throttle 31, a pressure lower than the opening pressure of the blow valve 8 is established in this phase in both embodiments.

If the electromagnetic system 7 is now switched off by a signal from the control unit after the free piston has reached its "dead" position, as perceived by the detector means 14, the electromagnetic means (6, 7) functions so that the valve member 5 drops under spring pressure to its lower switching position and fuel is injected through the atomizer 9 as described above.

The injection valve in accordance with the invention leads to the possibility that injection of fuel can be timed and metered with it being possible to detect when a given quantity of fuel has in fact been passed to the atomizer. Known interference factors, which hitherto had considerable influence, such as ageing, wear, deposits etc. now have little or no adverse effect on performance. When a plurality of injection valves is used, variations in the operating characteristics of the individual valves. as sometimes occurred with hitherto known multivalve installations, now have little effect and arise only to an extent dependent upon any variation which may be found in the performance of the travel-detection systems provided for each of the respective valves of the installed set.

1 1 9 0 Scavenging the injection valve in the phases between injection ensures that heating of the fuel with the formation of vapour bubbles can no longer occur during operation of the engine. The use of the injection valve in accordance with the invention ensures trouble-free, economical operation of an internal combustion engine with low emission of toxic substances in, for example, road vehicles.

In summary, and referring to the valve as depicted in the drawing, the invention provides an electronically controllable, electromagnetically actuated fuel injection valve for injecting fuel into an induction passage leading to,a cylinder combustion chamber of an internal combustion engine, the valve having the following features in combination:-

1) fuel leaves the valve through an atomiser (9) located in the induction passage, fuel reaching the atomiser by way of a blow-off valve (8) arranged to open at predetermined pressure, there being upstream of this in terms of fuel flow 2) a cylindrical measuring chamber (12) in which is movable a free piston (13), there being portions (26, 27) of the measuring chamber (12) on opposite sides of the piston (13); 3) detector means (14) are provided for monitoring the movements of the free piston (13); 4) means (3) are provided for supplying fuel under pressure in a chamber (4) and means (17) are provided for the discharge of fuel to a low pressure region (the fuel tank); 5) a valve member (5) is provided and rendered switchable by electromagnetic means (6, 7) into one of two alternative operative positions, the member (5) being spring biassed toward the adoption of one of said positions; 6) passage means (25) is closable by the valve member (5) but when open interconnects the chamber (4) with the lower portion (26) of the cylindrical measuring chamber (12) below the free piston (13) and located between the free piston (13) and the blow-valve (8); passage means (16) is closable by the valve member (5) but when open interconnects upper portion (27) of measuring chamber (12) above the free piston (13) to the discharge (17) leading to a low pressure region.

8) The arrangement is such that when the valve member (5) is switched to one of its operative positions (its lower position, i.e. that shown in the drawing, Figure 1), fuel under pressure is supplied to the portion (27) of measuring cylinder (12) on one side of the free piston (13) causing the piston (13) to move and to displace fuel located on its opposite side in cylinder portion (26) past the blow-valve (8) to be expelled through the atomizer (9) - the passage (25) and the passage (16) leading to discharge (17) both being closed at this stage.

9) Movement of the free piston (13) is monitored by detector means (14) so that, when a predetermined quantity of fuel has been displaced past the blow-valve (8), the movement of piston (13) corresponding to this displacement, the detector (14) sends a signal to control circuitry for the valve (1) which causes actuation of the electromagnetic means (6,7) to move the valve member (5) to its other upper operative position and this is effective abruptly to terminate that driving pressure on the free piston (13) which caused its earlier downwards movement.

10) Simultaneously with its adoption of this upper alternative operative position by the valve member (5), the passage (16) interconnecting with the discharge (17) leading to a low pressure region, is opened, and the passage (25) is also opened so that the pressure chamber (4) is interconnected with the region (26) on the underside of the piston (13), that is the region just upstream of the blow-off valve (8). The piston then rises in measuring cylinder (12) over a predetermined distance,, monitored by the detector means (14), which latter, at a predetermined instant sends a signal which results in cut-off of current supply to the electromagnetic means (6,7), so that the valve member (5) under the influence of spring bias means adopts its initial operative position. 11) When the piston (13) moves upwardly away from the blow-off valve (8) over a predetermined distance, this is accompanied by a predetermiped quantity of pres surized fuel moving behind it. This newly supplied fuel is then ready to be injected through the atomizer when next the opposite side of the free piston (13) is subjected to the pressure of fuel in chamber (4).

Preferably means are provided for scavenging the cylindrical measuring chamber (12) during valve operating phases between injection flows through the blow-valve (8). Two alternatives are proposed viz a) the free piston (13) may be provided with a valve controlled through bore (28) controlled by a spring loaded valve member (29), through which fuel is passed towards the relief (16) leading to low pressure discharge (17) or, instead of this, b) a passage 28' is provided with the same function but which by-passes the free piston (13) being located in the housing wall defining the chamber (10) and measuring cylinder (12).

Preferably also, throttle means (3 1) are provided in the passage (25) for damping the flow of fuel under pressure into the region (26) directly adjacent the blow-off valve (8) and the atomizer (9).

i 12

Claims (1)

1. An electromagnetic injection valve for delivering fuel into the induction passage or pipe of an internal combustion engine by way of an atomizer forming part of the injection valve but located in the induction passage, the injected fuel being driven through the atomizer ahead of a piston moving in a measuring cylinder, and there being means for detecting and monitoring the movements of the piston as it travels back and forth in the cylinder, the travel of the piston during each injection phase corresponding to the amount of fuel displaced through the atomizer, the detector means providing signals for an electronic control circuit which times the injection phases and the intervals between these phases during the operation of the electromagnetic fuel injection valve.

2. An injection valve as defined in claim 1, and which includes a fuel distribution valve which has a first switching position in which a portion of the measuring cylinder in communication with the atomizer on one side of the piston, is connected to a fuel supply system, while a measuring cylinder portion on the other side of the piston is connected to a fuel discharge system; and the distribution valve having a second switching position in which the last-mentioned measuring cylinder portion is connected to the fuel supply system and the other measuring cylinder portion disconnected from the fuel supply system; the piston being moved due to fuel pressure differences occurring on its opposite sides during these phases, such piston movements being monitored by the detector means which provides signals for the control circuit.

1 1 13 3. An electromagnetic injection valve for delivering fuel into an induction pipe of an internal combustion engine, having a fuel distribution valve (2) with an armature (6) and a valve member (5) which is movable into one of two operative positions under magnetic influence against spring force, and an atomizer extending into the engine induction pipe; and wherein a fuel flow measuring system (11) is disposed between the metering valve (2) and the atomizer (9) and comprises a measuring cylinder (12), a movable free piston (13) and a travel-detection system (14) for monitoring the movements of the free piston (13).

4. An injection valve as claimed in claim 3, and in which the valve member (5) of the fuel distribution valve (2) has a first switching position in which a measuring cylinder portion (26), in direct communication with the atomizer (9), and on one side of the free piston (13) is connected to a pressurized fuel supply system (3), and a measuring cylinder portion (27) existing at the other side of the free piston (13) is connected to a low pressure fuel discharge system (17), and a second switching position in which the last-mentioned measuring cylinder portion (27) is connected to the fuel supply system (3) and the other measuring cylinder portion (26) is disconnected from the fuel supply system (3).

An injection valve as claimed in claim 4, and in which the fuel distribution valve (2) has a valve member (5) which is axially bored, said valve member (5) having an end face (21) which, in said first switching position, sealingly abuts with a sealing surface (22) and has a collar (24) which acts upon a valve plate (23), which, in said first switching position of said valve member (5) is lifted off a seating surface to open communication, by way of a connecting passage (25), between the fuel supply system (3) and the measuring cylinder portion (26) on the side of the free piston (13) which communicates with the atomizer.

14 6. An injection valve as claimed in claim 5 and in which the valve member (5) has another end face (19) which is movable into and out of sealing engagement with a flat seat (20), this controlling flow to a relief chamber (16) connected to a low pressure fuel discharge system (17).

An injection valve as claimed in claim 6 and in which a by-pass passage (28, 28) exists between the two measuring cylinder portions (26, 27) and is opened when the free piston moves in one direction towards a limit stop, and when communication exists between the pressure system (3) and the measuring cylinder portion (26) which is adjacent and connected to the atomizer (9).

8. An injection valve as claimed in claim 7, characterised in that the bypass passage (28) is disposed in the free piston (13) and has a differential pressure valve (29), the limit position being defined by a stop shoulder (30) located in a cylindrical measuring cylinder (12) along which the free piston is movable.

9. An injection valve as claimed in claim 7, characterised in that the bypass passage (28') is disposed in a housing wall of the valve.

An injection valve as claimed in any one of claims 5 to 9, and including means (3 1) provided in the connecting passage (25) for throttling liquid flow therethrough.

An injection valve as claimed in claim 9, and in which the by-pass passage (28') is closed by the end face (19) of the valve member (5) when the fuel metering valve (2) is in its second switching position.

12. An injection valve as claimed in one of the preceding claims, characterised in that the travel-detection system (14) for monitoring the movements of the free piston operates by laser beam, ultrasonics, induction or capacitance means.

7 i i 13. An electromagnetic fuel injection valve according to claim 1 and substantially as hereinbefore described with reference to either of Figures 1 or 2 of the accompanying drawings.

Published 199 1 at The Patent Office. Concept House. Cardiff Road. Newport. Givent NP9 2 RH. Further copies may be obtained from Sales Branch. Unn 6. Nine Mile Point. CwTnfelinfach. Cross Keys. Newport. NP1 7HZ. Printed by Multiplex techniques ltd. St MarY Cray. Kent.