GB2183061A

GB2183061A - A fuel injection device for internal combustion engines

Info

Publication number: GB2183061A
Application number: GB08627289A
Authority: GB
Inventors: Frank Thoma
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1985-11-16
Filing date: 1986-11-14
Publication date: 1987-05-28
Also published as: FR2590322A1; GB8627289D0; IT8622311A1; DE3540811A1; IT1197973B; DE3540811C2; GB2183061B; FR2590322B1; IT8622311A0

Abstract

A fuel injection device with a pump 2 for air compressing injection type internal combustion engines has a pump plunger 12 actuated by engine camshaft 9, 10 and having no chamfer control provision, and an electromagnetic switching valve 3. Control device 4 controls the valve 3 in response engine speed, load and markings 14 such that after a control pulse triggered by the crankshaft 6 the timing and quantity of injection is determined. The arrangement may be used with engines having an odd or even number of cylinders. <IMAGE>

Description

SPECIFICATION A fuel injection device for internal combustion engines This invention relates to a fuel injection device for an air compressing injection-type reciprocating internal combustion engine, with a pump jet comprising a plunger guided in the pump cylinder and driven by a camshaft, and also with a pump working space communicating with the jet through a fuel pressure duct and with an electronic control device dependent upon the engine rotary speed and load and which controls a switching valve for influencing the fuel connection with the jet, and also with a pulse wheel disposed on the crankshaft and having a specific number of teeth for triggering a control pulse, and with a further pulse wheel with markings so that after a control pulse the crankshaft travels through an angle of rotation required for injection of a definite quantity, by counting the marking pulses.

Already known from DE-OS 32 24 769 is a fuel injection device of this type wherein, on the one hand, a rotary speed and load dependent electronic control device operates an electrical position member which co-operate with a position transmitter and is connected to the control rod of the pump jet, to permit control of the commencement of injection, and on the other an electromagnet switching valve which serves as a two-position magnetic valve which is connected by a filling passage to the working space of the pump. In this case, the quantity of fuel to be injected is preset by the switching valve. The pump plunger is provided with a control edge which, according to the position of the plunger, controls the control bore in the pump cylinder during the pressure stroke and so controls the commencement of injection.Termination of delivery is controlled by a so-called free plunger which co-operates with the pump plunger.

The present invention seeks to provide a fuel injection device with, actuated by an electronic control device through magnetic valves, an inlet into and an outlet from the pump working space which permits not only of accurate control of the commencement of injection but also an accurate control of the quantity injected.

According to the present invention there is provided a fuel injection device for an air compressing injection-type reciprocating internal combustion engine, with a pump jet comprising a plunger guided in the pump cylinder and driven by a camshaft, and also with a pump working space communicating with the jet through a fuel pressure duct and with an electronic control device dependent upon the engine rotary speed and load and which controls a switching valve for influencing the fuel con nection with the jet, and also with a pulse wheel disposed on the crankshaft and having a specific number of teeth for triggering a control pulse, and with a further pulse wheel with markings so that after a control pulse the crankshaft travels through an angle of rotation required for injection of a definite quantity, by counting the marking pulses, and thereby determining the opening period of the switching valve, wherein the number of teeth on the pulse wheel disposed on the crankshaft, in the case of an internal combustion engine having an even number of cylinders, corresponds to half the number of cylinders and the pulse wheel which determines the end of injection to determine injection of the desired quanitity is associated with the shaft which is at the same time the camshaft controlling the gas exchange valves of the internal combustion engine.

The invention also provides a fuel injection device for an air compressing injection-type reciprocating internal combustion engine, with a pump jet comprising a plunger guided in the pump cylinder and driven by a camshaft, and also with a pump working space communicating with the jet through a fuel pressure duct and withal electronic control device dependent upon the engine rotary speed and load and which controls a switching valve for influencing the fuel connection with the jet, and also with a pulse wheel disposed on the crankshaft and having a specific number of teeth for triggering a control pulse, and with a further pulse wheel with markings so that after a control pulse the crankshaft travels through an angle of rotation required for injection of a definite quantity, by counting the marking pulses, and thereby determining the opening period of the switching valve, wherein the pulse wheel disposed on the crankshaft is provided with a number of teeth corresponding to the odd number of cylinders of the internal combustion engine and the pulse wheel which determines the commencement of injection and subsequently the end of injection to determine injection of the desired quantity is associated with the shaft which is at the same time the camshaft which controls the gas exchange valves of the internal combustion engine, the pulse wheel comprising in its markings an orientation tooth gap by which and by the omission of every second control pulse at the crankshaft end, those control pulses which are in each case close to the point in time at which injection is desired are selected to determine the commencement of injection.

The fuel injection device according to the invention has the advantage that both the quantity injected and also the commencement of injection are controlled by a single switching valve. Commencement of injection must, for thermodynamic reasons, be related to the position of the reciprocating piston of the internal combustion engine at its top dead centre, this position being associated with a specific position of the crankshaft. The possibility of inadmissible errors in excluded by the particular combination, namely the camshaft controlling the quantity injected and the crankshaft controlling the commencement of injection.

By reason of the elasticity in the drive connection between crankshaft and camshaft and the consequently possible considerable relative rotary oscillations which might result, a known system of crankshaft control of the quantity injected and camshaft control of the commencement of injection would be too inaccurate.

Embodiments of the invention will now be described in detail hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of the fuel injection device according to the invention, for an internal combustion engine having an even number of cylinders; Figure 2 shows a part of the fuel injection device with magnetic valve actuated inlet and outlet on the pump working space of the pump jet, and Figure 3 shows a further embodiment of fuel injection device for an internal combustion engine having an odd number of cylinders.

The fuel injection device 1 illustrated in Figs.

1 and 2, for an air compressing injection type internal combustion engine, comprises a pump jet 2 havign an electromagnetically actuated switching valve 3 which serves as a two-position magnetic valve or 2/2-way valve which can be operated by an electric control device 4 dependent upon the operating parameters of the internal combustion engine so that commencement of injection and quantity injected are controlled solely via this single 2/2-way valve 3.

Vital to the operation of this valve 3, for commencement of injection, there is on the crankshaft 6 of the internal combustion engine a pulse wheel 5, of which the teeth 7 correspond in number to half the number of cylinders in the four-cylinder internal combustion engine shown in Fig. 1, since the crankshaft 6 rotates at twice the rotary speed of the camshaft 10.

Fuel injection occurs directly from the travel of the pump plunger 12 which is guided for axial diaplacement in the pump cylinder 8 and is driven through a rocker 11 by a cam 9 on the camshaft 10 (Fig. 2). The delivery stroke is, via the shape of the cam 9, associated with the angle of rotation of the camshaft 10 and during the delivery stroke, the 2/2-way valve 3 is largely in the closed position.

The quantity injected is determined by a pulse wheel 13 disposed on the camshaft 10 and provided with markings 14 constituted by numerous teeth, the number of which is expediently a whole multiple of the number of cylinders.

The embodiment according to Fig. 3 corresponds substantially to that shown in Fig. 1, but the fuel injection device is intended for an internal combustion engine having an odd number of cylinders, in this case a five-cylinder internal combustion engine, so that there are on the crankshaft pulse wheel 5 five teeth 7, while on the camshaft pulse wheel 13 there is an orientation tooth gap 15 which in the case of internal combustion engines having an odd number of cylinders, is required for fuel injection in order correctly to associate the pump jets 2 with the relevant cylinders.

The fuel injection device shown in Fig. 1 operates as follows: Upon triggering of a control pulse at the crankshaft 6, and after a time lag determined by the amount of travel completed, the desired commencement of injection takes place in the control device 4 by closure of the 2/2way valve 3.

The control pulse originating from the crankshaft, according to the commencement of injection desired, usually acts first while simultaneously with the commencement of injection subsequent counting of the camshaft pulses causes the camshaft 10 to rotate through the amount required for injection of the desired quantity and only then is the 2/2-way valve 3 opened. The described injection quantity is effected here as determined by the driver (according to load) and in keeping with other operating variables, e.g., temperature, etc., which are fed as input signals a, b to the electronic control device so that, together with the signals arising from the pulses from the camshaft and crankshaft wheels, they can be converted to an output signal to operate the 2/2-way valve 3.

The fuel injection device according to Fig. 3 and its mode of operation differ from that shown in Fig. 1 in that, for an internal combustion engine having an odd number of cylinders, it must comprise an orientation tooth gap 15 which serves as a starting mark on the camshaft pulse wheel 14 while the number of teeth on the crankshaft pulse wheel 5 must correspond to the number of cylinders in the internal combustion engine. Since, however, during one working stroke of the crankshaft pulse wheel, twice as many control pulses have to be delivered as there are cylinders, or twice as many injections have to take place, the omission of every second pulse at the crankshaft pulse wheel 5 results in selection of those pulses which are in each case close to the desired moment of injection. This is achieved in that, starting from the pulse of the orientation tooth gap 15, the next pulse on the crankshaft pulse wheel 5 is used for a delayed commencement of injection Simultaneously with the moment of the commencement of injection, counting of the pulses on the camshaft pulse wheel commences, the number being dependent upon the relative load signal and being a measure of the quantity to be injected.

In order to avoid errors in the injected quantity due to rotary oscillations, where the injection cam may vary in its position in relation to the crankshaft, it is possible to dispose on the camshaft pulse wheel 14 orientation tooth gaps corresponding to the number of engine cylinders. These orientation tooth gaps are always located in the same position in relation to the individual injection cams. Then, regardless of the position in which the cam is located by virtue of rotary oscillations of the crankshaft, the electronic control device can ascertain where the commencement of injection is located and from it, by choosing a corrected injection angle, determine exactly the quantity to be injected or the termination of injection via the cam travel/angular rotation travelled in the control device.

Claims

1. A fuel injection device for an air compressing injection-type reciprocating internal combustion engine, with a pump jet comprising a plunger guided in the pump cylinder and driven by a camshaft, and also with a pump working space communicating with the jet through a fuel pressure duct and with an electronic control device dependent upon the engine rotary speed and load and which controls a switching valve for influencing the fuel connection with the jet, and also with a pulse wheel disposed on the crankshaft and having a specific number of teeth for triggering a control pulse, and with a further pulse wheel with markings so that after a control pulse the crankshaft travels through an angle of rotation required for injection of a definite quantity, by counting the marking pulses, and thereby determining the opening period of the switching valve, wherein the number of teeth on the pulse wheel disposed on the crankshaft, in the case of an internal combustion engine having an even number of cylinders, corresponds to half the number of cylinders and the pulse wheel which determines the end of injection to determine injection of the desired quantity is associated with the shaft which is at the same time the camshaft controlling the gas exchange valves of the internal combustion engine.

2. A fuel injection device for an air compressing injection-type reciprocating internal combustion engine, with a pump jet comprising a plunger guided in the pump cylinder and driven by a camshaft, and also with a pump working space communicating with the jet through a fuel pressure duct and with an electronic control device dependent upon the engine rotary speed and load and which controls a switching valve for influencing the fuel connection with the jet, and also with a pulse wheel disposed on the crankshaft and having a specific number of teeth for triggering a control pulse, and with a further pulse wheel with markings so that after a control pulse the crankshaft travels through an angle of rotation required for injection of a definite quantity, by counting the marking pulses, and thereby determining the opening period of the switching valve, wherein the pulse wheel disposed on the crankshaft is provided with a number of teeth corresponding to the odd number of cylinders of the internal combustion engine and the pulse wheel which determines the commencement of injection and subsequently the end of injection to determine injection of the desired quantity is associated with the shaft which is at the same time the camshaft which controls the gas exchange valves of the internal combustion engine, the pulse wheel comprising in its markings an orientation tooth gap by which and by the omission of every second control pulse at the crankshaft end, those control pulses which are in each case close to the point in time at which injection is desired are selected to determine the commencement of injection.

3. A fuel injection device for an internal combustion engine substantially as described herein with reference to, and as illustrated in, the accompanying drawings.