GB2167808A

GB2167808A - I C engine fuel flow regulating system

Info

Publication number: GB2167808A
Application number: GB08524758A
Authority: GB
Inventors: Heinz Beier; Ernst Kuhlen; Henning Garcke; Otto Meyer
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1984-11-30
Filing date: 1985-10-08
Publication date: 1986-06-04
Also published as: FR2574126A1; IT1182870B; GB8524758D0; IT8548581A0; DE3443746A1

Abstract

A valve 6 between a fuel pump and a carburettor float chamber and opened by a spring-loaded diaphragm 7 to regulate the fuel pressure or a valve (22, Figs. 2 and 3) by-passing the valve 6 is opened to increase the supply of fuel in response to throttle valve opening. A diaphragm 17 acted on by manifold vacuum permits an additional spring 12 to act to open the valve 6 in response to a fall in manifold vacuum or the bypass valve (22) is opened in response to vacuum fall or energization of an electromagnet (18, Fig. 2) at a predetermined throttle valve opening. <IMAGE>

Description

SPECIFICATION Fuel flow regulating system The invention relates to a fuel flow regulating system for interposing in the fuel-feed line between the fuel pump and the mixture-forming device of an internal combustion engine, with an inlet and an outlet and with a housing containing a pressure-regulating valve.

In order to obtain a constant liquid level, for example in the carburettor float chamber of an internal combustion engine, with minimal fuel pressure applied to the needle valve of the float, a pressure-regulating valve is nowadays often interposed in the line between the fuel pump and the carburettor. A pressure-regulating valve of this kind also has the advantage that it can prevent excessively rich mixture from reaching the engine during acceleration from a standing start when the engine is hot.

On the other hand in very hot weather, or after the engine has been stopped when it is very hot, a pressure-regulating valve can cause problems in that bubbles are formed in the fuel flowing through the valve, reducing the mass-rate-of flow of the fuel. Although this effect is hardly perceptible during medium torque operation of the engine, nevertheless when the engine is delivering full power and consuming a large flow of fuel it can become seriously starved of fuel due to this cause.

In order to overcome this disadvantage of the conventional pressure-regulating valves it is the intention in the present invention to provide a fuel flow regulating system which keeps the fuel pressure as low as possible during idling and low-torque operation of the engine but which, as soon as the engine changes over to high torque, puts the pressure-regulating valve out of action so that the engine now receives the fullest flow of fuel that the pump is capable of delivering.

Starting from a fuel flow regulating system of the kind mentioned at the beginning, the problem is solved by the invention in that a positioning device responsible to engine torque acts on a valve which is arranged to ensure that at high torques the mixture-forming device receives the greatest supply of fuel that the fuel pump is capable of delivering.

This construction of the fuel flow regulating system has the effect that when inductionpipe pressure exceeds a predetermined value, or when high engine torque is detected, the fuel pump and the carburettor is opened fully, so that the influence of gas formation in the line is minimised. Further characteristics of the invention will now be described with the help of the figures, which show preferred but not limiting examples of the invention. In the figures corresponding parts have been given the same index numbers.

The figures show: Figure 1 shows a first example of the fuel flow regulating system of the invention.

Figure 2 shows a second example, and Figure 3 shows a third example.

The fuel flow regulating system shown in Fig. 1 comprises a housing 1, with an inlet 2 and an outlet 3. The housing 1 contains a pressure-regulating valve 4 of a kind known per se, which is influenced, in a manner which will be described further below, by a positioner 11. The pressure-regulating valve 4 has a valve body 6 which cooperates with the under-surface of a valve seat 5, the valve body 6 being thrust upwards by a compression spring 16. When the engine is at rest, no fuel flowing, a lower flexible diaphragm 7 thrusts the valve body 6 resiliently downwards into the position shown in Fig. 1, against the influence of the compression spring 16, so that the valve body is clear of its valve seat 5. Under these circumstances there is a free patch for the flow of fuel between the inlet 2 and the outlet 3 through an open port 6.1 in the stem of the valve body 6.The upper surface of the lower diaphragm 7 is acted on by atmospheric pressure which is applied in the chamber above the lower diaphragm 7 through an atmospheric port 10. The lower diaphragm 7 is also thrust resiliently downwards by a compression spring 8, whose upper end is supported by a spider 13, which can be of The positioner 11, is fixed, in this example of the invention, to an upper flexible diaphragm 17 situated above the lower diaphragm 7 so that an atmospheric chamber is formed between the two diaphragms. A further compression spring 12 thrusts the diaphragm 17 resiliently downwards, the upper end of this spring 12 taking support against a cap 9. The chamber above the upper diaphragm 17, formed by the diaphragm 17 and the cap 9, communicates with the induction pipe of the engine through a suction connection 15.Fixed to the middle of the upper flexible diaphragm 17 and projecting downwards into the atmospheric chamber, there is an actuator pin 14 which can, if desired, be guided in its movement by the spider 13. The action of the actuator pin 14 will be described further below.

The method of functioning of this first example of the fuel flow regulating system of the invention, shown in its position of rest in Fig. 1, is as follows: When an engine equipped with the device of the invention has been started up and is idling, or overrunning, or operating at low torque, the pressure-regulating valve 4 is in action. The fuel arriving through the inlet 2 from a fuel pump (not shown) is delivered, under a controlled pressure, through the outlet 3 to float-valve needle (not shown) of the carburettor. The inductionpipe suction acting on the upper surface of the upper diaphragm 1 7 lifts this diaphragm 17, against the influence of its spring 12, lifting the actuator pin 14 clear away from the lower diaphragm 7, so that the positioner 11 does not, under these circumstances, act on the pressure-regulating valve 4.Consequently the lower diaphragm 7, assisted by its compression spring 8, keeps the fuel delivery pressure constant, preferably at about 0.1 bar.

The open port 6.1 in the stem of the valve body 6 is adapted to suit the flow requirements of the engine.

On the other hand, as soon as the engine changes over to medium or high torque operation, the induction-pipe pressure acting on the positioner 11 rises, with the consequence that the upper diaphragm 17, thrust by its compression spring 12, flexes downwards, lowering the actuator pin 14 so that this flexes the lower diaphragm 7 downwards, lowering the valve body 6, against the thrust of the lower spring 16 and opening the pressure-regulating valve 4. This makes the pressure-regulating valve 4 ineffective, the engine now receiving the full delivery capacity of the fuel pump. The flow cross section of the valve 4 cannot be influenced by the gas or fuel pressure acting on the under-surface of the lower diaphragm 7, because the upper compression spring 12 is too strong.

Fig. 2 shows a second example of the fuel flow regulating system of the present invention. Here again the pressure-regulating valve 4 consists of the parts 5, 6 and 7, although in this example the compression spring 8 acting on the diaphragm 7 takes support, at its upper end, against the cap 9. The chamber above the diaphragm 7, formed by the diaphragm 7 and the cap 9, is vented to the external atmosphere through an open port 10.

In this example, in addition to the pressureregulating valve 4, the housing 1 contains a bypass valve 20 comprising a second valve body 22 cooperating with a second valve seat 21, this valve body 22 also having an open port 22.1 in its stem. The two valve bodies 6 and 22 are preferably positioned on a common longitudinal axis 24. A pre-loaded compression spring 16 thrusts the two valve bodies 6 and 22 away from each other. The lower valve body 22 is thrust upwards by the nose of the armature 19 of an electromagnet 18 which, in this example, takes the place of the pneumatic positioner 11 of the example of Fig. 1. The coil of the electromagnet 18 receives electric current in dependence on signals representing engine torque.

A compression spring (not shown) thrusts the armature 19 upwards, the nose of the armature 19 thrusting the valve body 22 upwards. Fuel pressure regulation takes place substantially as described for the example of Fig. 1. During engine idling and low-torque operation the electromagnet 18 holds the armature 19 retracted downwards against the influence of the spring. Under these circumstances the pre-loaded compression spring 16 holds the valve body 22 down against its seat 21.

As soon as engine torque increases to medium or full torque, corresponding to a predtermined throttle valve opening, the flow of current to the electromagnet 18 is interrupted, for example by a switch connected to the throttle valve, with the result that the compression spring (not shown) lifts the armature 19, lifting the valve body 22 of its seat. This opens the bypass valve 20 so that fuel can flow freely through the open port 22.1 in its stem, the engine now receiving the full delivery capacity of the fuel pump.

Finally, Fig. 3 shows a third version of the fuel flow regulating system of the invention.

The fuel pressure-regulating valve 4 is the same as in the example of Fig. 2.

The bypass valve 20 comprises a second valve seat 21 cooperating with a second valve body 22. When the device is at rest, as represented in Fig. 3, the valve body 22 is thrust upwards by the nose of a pneumatic positioned 11 comprising a lower diaphragm 23 and a compression spring 12 which thrusts upwards against the diaphragm 23 and takes support, at its lower end, against a lower cap 25, which has a connection 15 communicating with the induction pipe of the engine, so that induction-pipe pressure acts on the under-surface of the diaphragm 23.

The two valve bodies 6 and 22 are positioned on a common longitudinal axis in the housing 1, and are thrust away from each other by a pre-loaded compression spring 16.

The thrust applied by the spring 16 is much less than that of the spring 12, the spring 16 merely serving to hold the first valve body 6 in contact with the first diaphragm 7.

The method of functioning of the third version of the invention is substantially the same as described for the version of Fig. 2. When the engine is idling, or overrunning, or in lowtorque operating the lower diaphragm 23 is flexed downwards by the induction-pipe suction acting on the under-surface of the lower diaphragm 23, so that the bypass valve 20 remains closed.

As soon as the engine changes over to medium-torque or full-torque operation, the increasing induction-pipe pressure lifts the bypass valve 20, opening this valve. This makes the fuel-pressure regulation ineffective and the engine receives the full delivery capacity of the fuel pump. The open cross section of the valve passage remains uninfluenced by gas and fuel pressure acting on the upper surface of the lower diaphragm 23, due to the high thrust applied by the lower compression spring 12.

Claims

1. A fuel flow regulating system for interposition between the fuel pump and the mixture-forming device of an internal combustion engine, with an inlet and an outlet and with a housing containing a pressure-regulating valve, characterised in that a positioning device (11) responsive to engine torque acts on a valve (4 or 20) which ensures that at high torques the mixture-forming device receives the greatest supply of fuel that the fuel pump is capable of delivering.

2. A fuel flow regulating system as claimed in Claim 1, characterised in that the valve which is acted on by the positioning device (11) is the pressure-regulating valve (4).

3. A fuel flow regulating system as claimed in Claim 1, characterised in that the valve which is acted on by the positioning device (11) is a bypass valve (20) which bypasses the pressure-regulating valve (4).

4. A fuel flow regulating system as claimed in Claims 2 and 3, characterised in that the positioning device (11) responds to induction-pipe pressure.

5. A fuel flow regulating system as claimed in Claim 3, characterised in that the positioning device (11) is an electromagnetically actuated valve (18) whose coil receives current when the throttle valve adopts a predetermined position.