GB2140091A

GB2140091A - Fuel supply system for a diesel engine

Info

Publication number: GB2140091A
Application number: GB08313628A
Authority: GB
Inventors: Ralph Gilbert Jefferies; Vincent David Hogan
Original assignee: Petter Refrigeration Ltd
Current assignee: Petter Refrigeration Ltd
Priority date: 1983-05-17
Filing date: 1983-05-17
Publication date: 1984-11-21
Also published as: GB8313628D0

Abstract

Fuel for a diesel engine is pumped by pump 8 from a main fuel tank 7 to a reservoir 1 from where it is fed via filter 13 and lines 15, 16 to a fuel injection pump 14 of a diesel engine. Excess fuel is returned via leak off rail 4 and lines 5, 6 to the main tank 7. A detector 2 detects the level of fuel in reservoir 1 and when the fuel falls to a predetermined level actuates a relay 3 to operate a solenoid 17 which shuts down the engine. Air entrained in the fuel supply by pump 8 escapes from reservoir 1 via outlet 10 to return to the main tank 7 via line 6. The reservoir 1 is preferably kept above the level of rail 4 to prevent air at outlet 10 of the reservoir entering rail 4. By shutting down the engine before reservoir 1 runs dry, fuel injection pump 14 always remains primed. <IMAGE>

Description

SPECIFICATION Fuel supply system for a diesel engine With a diesel engine, air entrainment in the fuel injection system will prevent the running or starting of an engine, requiring the call-out of a trained engineer to bleed the system of air before the engine can be started.

Where a diesel engine is fitted to a trailer unit of a lorry there is often no immediate indication in the drivers cab of the fuel level for the engine supply, increasing the likeli hood of the engine running short of fuel and so entraining air in the fuel system. This is a problem particuiarly with refrigerated trailer units which are often parked and left with the engine running unattended, the engine power ing the refrigeration unit.

The present invention aims to provide a system which will shut down the engine before air enters the fuel injection system.

A first aspect of the invention provides a fuel supply for a diesel engine, comprising a main fuel tank, a reservoir and a fuel injection system, wherein, in use, fuel passes from the main fuel tank to the fuel injection system via the reservoir, the reservoir having detection means for detecting a level of fuel in the reservoir, the detection means being operatively connected to the diesel engine to shut down the engine when the fuel level reaches a predetermined value.

Another aspect of the invention provides a trailer mounted refrigeration unit having a diesel engine and a fuel supply system for the diesel engine, the fuel supply system comprising a main fuel tank, a reservoir and a fuel injection system, wherein, in use, fuel passes from the main fuel tank to the fuel injection system via the reservoir, the reservoir having detection means for detecting a level of fuel in the reservoir, the detection means being operatively connected to the diesel engine to shut down the engine when the fuel level reaches a predetermined value.

Another aspect of the invention provides a monitor for monitoring the fuel supply to a diesel engine, the monitor comprising reservoir means for supplying fuel to the engine, and detection means for detecting a level of fuel in the reservoir, the detection means providing a signal to shut down a said engine when the level reaches a predetermined minimum value.

Diesel engines may be provided with means to shut down automatically the engine in response to low oil pressure or high cooling water temperature. One such means is a solenoid connected to the fuel rack on the fuel injection pump, the solenoid shutting the rack down to stop the engine. Preferably, the detection means of the present invention is arranged to actuate such a solenoid.

The invention will be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagram of the fuel supply system of a diesel engine powering a refrigeration plant of a refrigerated trailer unit; Figure 2 shows a fuel supply monitor of the system of Fig. 1.

A fuel supply monitor 1 has a fuel level probe 2 which is of the resistance type and which is connected through a relay 3 to a solenoid 1 7 arranged to shut the engine down when the solenoid is deenergised, for example by shutting a fuel rack of fuel injection pump 14.

The monitor 1 is preferably connected to a frame of the engine or trailer unit at a point above the level of leak off rail 4 of a diesel engine (not shown). Leak-off rail 4 is connected by fuel return lines 5 and 6 to a main fuel supply tank 7. A branch line connects fuel lines 5, 6 to port 10 of the monitor 1.

The main fuel tank 7 is connected to monitor 1 at port 11 by fuel line 9, a fuel pump 8 pumps fuel up to the monitor 1. A fuel, line 1 5 connects port 1 2 of monitor 1 to an engine fuel filter 1 3 which is connected to engine fuel injection pump 14 by fuel line 16.

Pump 14 feeds fuel injectors 24. It is pump 14, in particular, which must be kept primed with fuel.

A second fuel pump (not shown) may be mounted in fuel line 1 5 between port 1 2 and filter 1 3. Also, rail 4 may be connected to the inlet of the filter 1 3 upstream of the connection with the monitor 1 at port 10.

Monitor 1 has a lower bowl 1 9 connected to upper portion 20 by a fixing bolt 22, screwed into stem 23 on the bowl 19. Port 10 of the monotor 1 is located behind the head of bolt 22, as viewed in Fig. 2.

During normal operation of the fuel lift pump 8, air is often entrained by the pump and will be pumped to the engine via fuel line 9. Any air pumped into monitor 1 passes out through port 10 at the top of the monitor and is returned to the main tank 7 via line 6.

During normal operation of the engine, fuel is lifted from the main tank 7 by pump 8 and fed through line 9 to enter the monitor 1 at port 11. Excess fuel returns to the tank 7 via port 10 and fuel line 6. A restriction may be provided in fuel line 6 to control the rate of return flow through line 6.

Fuel is supplied to the engine from monitor 1 via line 15, filter 13 and line 16. Excess fuel returns via leak off rail 4 and line 5 to port 10 of the monitor 1 and to the main tank via line 6.

The monitor 1 is full of fuel and probe 2 passes an appropriate signal 3 controlling solenoid 17, to hold the rack of the fuel pump 14 in the normal position.

When fuel tank 7 empties of fuel air is pumped into monitor 1, the fuel level in monitor 1 falls as the engine continues to run and air passes back to the tank 7 via line 6 until lines 6 and 9 are empty.

The engine continues to run on the fuel in monitor 1 until the level falls to the switch level 25, when a signal is passed by relay 3 causing the solenoid 1 7 to shut the engine down. At this point, there is still a full supply of fuel in line 15, filter 13, line 1 6 rail 4 and line 5, hence the system remains primed.

Placing the monitor 1 above rail 4 ensures that there is no tendency for air at the top of monitor 1 to enter line 5 and rail 4. A one way valve could be provided. Also, the fuel may be gravity fed to the pump 14 or, as mentioned previously, a pump may be located in line 15.

On refiliing the tank, pump 8 pumps fuel into monitor 1 via line 9. Probe 2 cancels the signal to relay 3 and solenoid 1 7 allows the engine to be run again.

To enable easy starting of diesel engines, it is common to use glow plugs. The glow plugs must be heated for about ten seconds at the beginning of the engine start cycle and this is sufficient time for the fuel level in monitor 1 to rise to cancel the signal from probe 2, before the engine is cranked.

Alternatively, an override system can be built into the electrical system to ailow all systems to be cancelled until the engine reaches full speed. This assists the operator in determining which system is cutting out the engine. The small amount of fuel held in monitor 1 is sufficient to run the engine for a number of start attempts if an override system is used.

The system can be used to provide other services. The signal from probe 2 may be used to control the changeover from the one main fuel tank to another. Two probes could be used. A first being actuated at a high fuel level in monitor 1 to change between main fuel tanks, and a second at a lower fuel level for engine shutdown.

Alarm systems can be operated by the probe 2 to signal in the drivers cab or elsewhere.

The invention has been described with particular reference to trailer mounted refrigeration units where it is particularly advantageous, but it may be applied to other diesel engines where automatic engine shut down is required, in particular stationary units.

Preferably, the monitor 1 is of small volume, for example 500 cm3, to provide a fast reaction time for the system.

Claims

1. A fuel supply for a diesel engine, comprising a main fuel tank, a reservoir and a fuel injection system, wherein, in use, fuel passes from the main fuel tank to the fuel injection system via the reservoir, the reservoir having detection means for detecting the level of fuel in the reservoir, the detection means being operatively connected to the diesel engine to shut down the engine when the fuel level reaches a predetermined value.

2. A fuel supply as claimed in claim 1, wherein the detection means is arranged to control a solenoid on a fuel rack of a fuel injection pump for a said diesel engine, to shut down the engine.

3. A trailer mounted refrigeration unit having a diesel engine and a fuel supply as claimed in claim 1 or 2.

4. A unit as claimed in claim 3, wherein fuel is pumped from the main fuel tank to the reservoir and is fed from the reservoir to a fuel injection unit of the diesel engine, and the reservoir is connected to a fuel return line, which line returns to said main fuel tank fuel from a leak off rail of said fuel injection unit, for returning air from said reservoir to said main tank.

5. A unit as claimed in claim 4, wherein the reservoir is mounted above the level of the leak off rail of the fuel injection pump.

6. A unit as claimed in claim 4 or 5, wherein a restriction is provided in the fuel return line downstream of the connection to the reservoir.

7. A unit as claimed in any one of claims 1 to 7, wherein the reservoir comprises a chamber having an inlet port for fuel from the main fuel tank, an outlet port for fuel to the fuel injection system, a detector mounted in the chamber for detecting a predetermined level of fuel in the chamber, and an outlet port at an upper part of the chamber for the escape of air from said chamber.

8. A unit as claimed in any one of claims 1 to 7, wherein the said detection means detects a first level of fuel in said reservoir for switching between main fuel tanks and a second level of fuel in said reservoir for shutting down said engine.

9. A fuel supply system for a diesel engine, substantially as hereinbefore described with reference to the accompanying drawings.

10. A trailer mounted refrigeration unit including a fuel supply system substantially as hereinbefore described with reference to the accompanying drawings.

11. A monitor for monitoring the fuel supply to a diesel engine, comprising reservoir means for containing fuel for the engine and detection means for detecting a level of fuel in the reservoir and for providing a signal to shut down a said engine when the level reaches a predetermined value.

12. A monitor for monitoring the fuel supply to a diesel engine substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.