GB2217386A

GB2217386A - Diesel engine glowplug installation

Info

Publication number: GB2217386A
Application number: GB8808274A
Authority: GB
Inventors: Michael Ernest Bishop-Laggett; Henry Gazeley Howitt
Original assignee: MYCALEX Co Ltd; Ford Motor Co
Current assignee: MYCALEX Co Ltd; Ford Motor Co
Priority date: 1988-04-08
Filing date: 1988-04-08
Publication date: 1989-10-25
Also published as: GB8808274D0

Abstract

The glowplug 14 is mounted so that it can be retracted from the combustion chamber 10 once the engine is running. This avoids the presence of the plug which otherwise disturbs gas flows in the chamber. The energy for securing the retraction of the plug is obtained from oil pressure existing in the engine when it is running, the solenoid operated valve 24 permitting the oil pressure to act on the piston 18 to move the glowplug 14 against the force of a spring 20 when the power supply is terminated after a preset time. <IMAGE>

Description

DIESEL ENGINE GLOWPLUG INSTALLATION This invention relates to a glowplug installation in a diesel engine. Glowplugs are required to initiate combustion in a diesel engine. They are located in a combustion chamber, normally the precombustion chamber, and are heated electrically to provide the necessary energy to initiate combustion.

The plug is only required when starting the engine from cold, and is redundant while the engine is running.

Conventionally however the plug projects into the combustion chamber and presents an obstacle to the creation of the desired swirl characteristics in the chamber. The continued presence of the plug thus has an adverse effect on fuel economy and smoke characteristics of the engine.

According to the invention, there is provided a diesel engine glowplug installation comprising a housing formed externally of a combustion chamber and having an opening into the chamber, a glowplug fitted in the housing and extending through the opening, and means for moving the plug between a position where it is located substantially wholly within the housing and a position where it projects into the chamber, wherein the means for moving the plug is operated by oil pressure generated by the engine when the engine is turning over.

The use of a retractable glowplug allows the plug to project into the combustion chamber when it is needed for starting, and to be removed from the chamber, or brought to a position where it is flush with the chamber wall, once the engine is running so that id does not interfere with gas flow in the chamber.

The plug moving means ma be spring-biased in one direction, and the supply of engine oil pressure to the installation can be arranged so that the oil pressure, when applied, overcomes the spring biassing to move the plug. Preferably the spring biases the plug into the chamber and the oil pressure retracts the plug into the housing.

The oil pressure is preferably applied to the housing by way of an ON/OFF valve which may be solenoid operated.

A timing circuit can be included to operate the valve at a preset time after the engine has fired, and this time can conveniently coincide with the time at which the heating current to the glowplug is switched off.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an installation in accordance with the invention; Figure 2 shows the installation with an activation voltage applied to the valve; Figure 3 shows the installation once the engine is turning over; and Figure 4 shows the installation with the engine running.

The drawings show a pre-combustion chamber 10 of a diesel internal combustion engine. In the wall of the chamber 10 is a housing 12 which contains a glowplug 14.

The glowplug can be moved between an extended position shown in Figures 1, 2 and 3 and a retracted position shown in Figure 4.

The housing 12 has an internal cavity 16 which is cylindrical in form and contains a base portion 18 of the glowplug body. Through this base portion, the plug 14 can slide along the cavity 16 in the housing 12.

Movement of the plug 14 in the cavity 16 is controlled in one direction by a spring 20 (which is indicated schematically in the figures), and in the other direction by oil pressure applied through an inlet 22 and controlled by a valve 24. The oil pressure enters the right-hand end of the chamber through an inlet aperture 26 into a space 27 bounded by the chamber walls and the plug body. The base portion 18 of the body is sealed to the chamber walls by a seal 28, and the shaft portion 30 is sealed to an opening in the housing end face by a seal 32.

Figure 1 shows the installation in a rest condition with no oil pressure applied. The spring 20 biases the plug out of the chamber, and the valve 24 is open.

In operation, when the engine is to be started, the action of switching on the current to the glowplug applies a voltage across the supply terminals 34 which transmits a heating voltage to the plug itself and an activation voltage to a solenoid 36 which operates the valve 24, to cause the solenoid to close the valve. The heating voltage to the plug passes through the spring 20 which provides an electrical connection between a terminal plate 38 in the housing and an opposite terminal plate 40 on the glowplug. This position is shown in Figure 2. The engine then starts.

Once the engine is running, the pressure within the lubricating oil servicing the engine builds up, and appears at the inlet 26. Since the valve 24 is closed, the oil pressure is not at this stage transmitted to the housing 12. This stage is shown in Figure 3. However after a preset time interval (which may be determined by an engine management system) the power supply across the terminals 34 is removed so that the glowplug 14 is deactivated and the solenoid voltage is removed, allowing the oil pressure to open the valve 24 and to reach the housing 12. The oil pressure then overcomes the spring 20 and pulls the glowplug back into the housing, to the position shown in Figure 4. This position, with the glowplug retracted, is maintained all the time the engine is running, as the high oil pressure level will prevail.

As soon as the engine stops, the oil pressure will drop and the spring 20 will cause the plug 14 to be extended into the chamber 10 once more.

In this way, the plug will be removed from the combustion chamber during normal running to allow the operating conditions in the chamber to be optimised.

In a multi-cylinder engine, one solenoid valve 24 can control the oil pressure supply to the housings 16 of all the combustion chambers. Alternatively there could be a valve associated with the combustion chamber of each cylinder.

Claims

1. A diesel engine glowplug installation comprising a housing formed externally of a combustion chamber and having an opening into the chamber, a glowplug fitted in the housing and extending through the opening, and means for moving the plug between a position where it is located substantially wholly within the housing and a position where it projects into the chamber, wherein the means for moving the plug is operated by oil pressure generated by the engine when the engine is turning over.

2. An installation as claimed in Claim 1, wherein the plug moving means includes a spring for biassing the plug in a direction opposite to that in which it is biased by oil pressure.

3. An installation as claimed in Claim 2, wherein the spring biases the plug into the chamber and the oil pressure biases the plug into the housing.

4. An installation as claimed in any preceding claim, wherein the oil pressure is applied to the housing by way of an ON/OFF valve.

5. An installation as claimed in Claim 4, wherein the valve is solenoid operated, and the solenoid is connected into the electrical circuit supplying the heating voltage to the glowplug so that when the electrical supply to the plug is interrupted, the supply to the solenoid is also interrupted.

6. An installation as claimed in any preceding claim, wherein the oil pressure derives from the engine lubrication system.

7. An installation as claimed in Claim 2, wherein the spring is op electrically conductive material and the electrical power supply to the glowplug is through the spring.

8. A diesel engine glowplug installation substantially as herein described with reference to the accompanying drawings.