The present invention relates to an installation according to Claim 1. An installation of this type is disclosed in the publication:

International Journal of Hydrogen Energy, part 15, no. 1, January 1, 1990, London, pages 27-32, in the article by Krepec entitled 'improved concept of hydrogen on-board storage and supply for automotive applications' . Said installation has been designed in particular for injection of hydrogen gas in vapour form.

Sequential injection is known for the injection of petrol in vehicle engines. This means that the cylinders are supplied with fuel in ignition sequence. In the most simple embodiment, an installation of this type comprises a central rail to which one or more injection valves are connected for each cylinder, which injection valves are activated electrically. Said injection valves will be activated for only part of a revolution of the crankshaft.

In the case of petrol as the fuel, sequential injection is important both during starting/switching off and during continuous operation. During continuous operation the injection of petrol throughout the entire inlet stroke is generally undesirable, as is disclosed in the prior art. In the case of gas engines, trials show that the effect of sequential injection during continuous operation is not pronounced, or is less pronounced, compared with continuous feed. However, even in the case of gas engines, a construction of this type offers the possibility, when switching on or switching off, of allowing each cylinder to execute a complete combustion stroke by linking the control electronics to the position of the engine. That is to say, if it is decided to switch off the fuel supply while the engine is running, for example in the case of deceleration, if fuel supply is taking place to a specific cylinder at that point in time, this supply

will be continued, but no new metering for a subsequent cylinder will be started. This means that the last cylinder operated is able to terminate combustion in an effective manner.

When starting the internal combustion engine again, it is likewise the case that that cylinder which can be subjected to a complete fuel supply cycle is activated.

In this way incomplete combustion or no combustion at all, of a fuel/air mixture is prevented. This is particularly beneficial for the life of a catalyst and the quality of the exhaust gas. The aim of the present invention is to employ a construction of this type in internal combustion engines which operate on gas, such as natural gas, hydrogen or LPG.

This aim is achieved with an installation as described above which has the characterising features of Claim 1. In contrast to the construction customary in the case of petrol engines, which has been described above, a construction of this type is difficult to realise in the case of gas engines. After all, the energy density of dry gas is many times lower than the energy density of liquid petrol. This means that the introduction time is longer. It is pointed out that a Schlitz system is known per se from the International Patent Application 92/11448. With this system dry gas originating from a conventional vaporiser is distributed over a number of cylinders after it has passed through a dry gas shut-off valve in a so- called Schlitz device. The Schlitz device is usually provided with a piston element with an opening. In a certain position, said opening corresponds with an opening adjoining the individual feed to each of the cylinders. Metering takes place by moving the piston with respect to the stationary opening. In this device the passage is made V-shaped in order to provide accurate metering. Positioning of the piston is effected by a stepping

motor. Sequential injection is not proposed in this publication. Instead of a single Schlitz it is also possible to use a multiple Schlitz as disclosed in the prior art, which multiple Schlitz is likewise installed upstream of the distributor. Moreover, it is possible to install a number of Schlitz devices upstream or downstream of the distributor.

As has been described above, sequential injection offers the possibility, when changing the regime of the internal combustion engine, to start or to terminate the gas supply on completion of the preceding injection or withholding, respectively. Consequently, there will never be a partially combusted or uncombusted mixture in the cylinders. According to the invention, the various features are realised in that the at least one shut-off valve is managed by an appropriate control.

As indicated above, the advantages of sequential introduction of gas into an internal combustion engine during continuous operation are slight. Using the installation according to the present invention it is possible, in contrast to installations which operate with electrical injectors mounted on the inlet tract, which provide both the on/off function and the metering function, largely or entirely to dispense with sequential metering during continuous operation and to convert to full sequential operation only on detection of the termination of operation or when starting. It will be understood that the life of the various components can be appreciably prolonged by this means.

It is also conceivable to construct the Schlitz device as a shut-off valve, that is to say to install no further shut-off valve downstream of the latter. This means that during continuous operation said device gradually opens further or less far, depending on the operating status, and that the Schlitz makes a very rapid movement during starting or deceleration.

The invention will be explained in more detail below with the aid of illustrative embodiments shown in the drawing. In the drawing:

Fig. 1 shows, diagrammatically, a first embodiment of the invention;

Fig. 2 shows a cross-section of the Schlitz device according to Fig. 1; Fig. 3 shows, highly diagrammatically, a number of alternative embodiments with a "Monoschlitz" element; and

Fig. 4 shows an alternative embodiment with a "Multischlitz" element.

A first embodiment of the invention is shown diagrammatically in Fig. 1.

1 indicates part of an internal combustion engine provided with an outlet 2 and an inlet 3. A throttle valve 4 is located in the inlet, the position of said throttle valve being reported via line 5 to microprocessor 6. 7 indicates the flywheel of the engine and 8 a position detector, which is connected via line 9 to microprocessor 6. Cycle information is obtained in a manner which is not shown. In the outlet tract 2 there is a lambda probe 10, which is likewise connected to the microprocessor.

The installation shown here is suitable for operation both with petrol and with LPG and to this end a switch 11 is fitted. The pressure in the inlet tract is measured via a MAP sensor 12, which is likewise connected to microprocessor 6. The fuel supply comprises a feed line 13 for liquefied gas originating from, for example, a tank. The liquefied gas is fed through shut-off valve 14 into vaporiser/pressure regulator 15. The latter is equipped to dispense so-called dry gas, i.e. gas in vapour form, under a pressure of between 1.3 and 2.0 bar absolute into discharge line 16. The pressure level is dependent on the load and is partly determined by the pressure prevailing within connection line 17. Said gas in vapour form is fed through a dry gas shut-off valve 18, which is actuated by relay 19, which, in turn, is controlled by microprocessor 6. The gas is fed into a distributor unit 20 where gas is, on the one hand, uniformly distributed over the individual

lines 21-24 for the individual cylinders and, on the other hand, is metered. An installation of this type is known as a Schlitz element. The functioning of this element is described in the International Patent Application 92/11448. This installation is shown in cross-section in Fig. 2. It can be seen from this figure that a plunger 25 can be moved upwards and downwards by the action of a stepping motor 26, as a result of which movement opening 27 is exposed to a greater or lesser extent.

The construction described up to now essentially corresponds to the construction which is known under "MEGA or EGI systems". According to the invention, shut-off valves 28-31 are installed in the lines 21-24. Said shut-off valves are connected via lines to a control 32, which, in turn, is connected to microprocessor 6.

Control 32 works in conjunction with microprocessor 6 or is integrated therein and in this way a system is obtained with which, at the point in time when, for example, the gas supply has to be terminated, as in the case of deceleration, where the throttle valve is closed and the engine has appreciable revs, the termination signal for the metering of fuel is not given immediately to all cylinders but is given in such a way that no new metering cycle of gas to a new cylinder is started but, on the other hand, the metering cycle for gas which is already in progress is completed.

The same applies when gas metering is restarted. Gas is given only to that cylinder for which a complete metering cycle is possible. In the case of the intermediate continuous operation, sequential operation is possible, but not necessary. Variants of the inventive concept are shown in Figs 3 and 4.

Fig. 3 shows embodiments having a metering element or Schlitz device with a single in- and outlet. The latter is indicated by 33. Said metering element can be any metering element known in the prior art which is able accurately to control the quantity of gas supplied. In the first

alternative embodiment in Fig 3a, a number of individual shut-off valves 36 corresponding to the number of cylinders are arranged downstream of the Schlitz element. In the embodiment according to Fig 3b, a multiple Schlitz is used, downstream of which a number of shut-off valves are installed. In the embodiment according to Fig 3c, the sequence is precisely the reverse. In Fig 4 the construction according to Fig. 1 is shown diagrammatically. The installation according to the present invention is preferably driven in such a way that during the major part of the operation fluctuating loads are compensated for with the aid of the Schlitz device. Especially when starting and when switching off, use is made of sequential, intermittent control of the gas stream to the various cylinders with the aid of the shut-off valves 36. As a result the shut-off valves are subjected to appreciably less wear. In trials it has been found that the effect of sequential injection during continuous operation of conventional internal combustion engines which are driven by a gas is barely measurable if the composition of the exhaust gas is taken as the reference.

It can be seen from the above that many variants are possible which fall within the scope of the present invention. The aim of the invention is therefore also to encompass such variants, which fall within the scope of the appended claims.