WO1997037110A1

WO1997037110A1 - Cooling system alarm for fluid cooled internal combustion engines

Info

Publication number: WO1997037110A1
Application number: PCT/AU1997/000206
Authority: WO
Inventors: Peter Raymond Burnitt; Robert Martin
Original assignee: Novaheat Pty. Ltd.
Priority date: 1996-03-29
Filing date: 1997-04-01
Publication date: 1997-10-09

Abstract

A cooling system alarm unit (1, 10, 10a) has a pressure sensitive switch (4, 13, 13a) connected to a triggering circuit (9, 19, 19a) which controls audible and/or visual alarms (10, 11, 17, 18, 17a, 18a). The triggering circuit (9, 19, 19a) operates when the coolant pressure drops below, or optionally exceeds, preset values and has a delay to accommodate transient troughs/peaks.

Description

TITLE: COOLING SYSTEM ALARM FOR FLUID COOLED

INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION

(1 ) Field of the Invention THIS INVENTION relates to a cooling system alarm for fluid cooled internal combustion engines and is applicable to the cooling systems of motors.

(2) Prior Art

The supply of coolant to the power heads/cylinder block and head of fluid cooled internal combustion motors is critical. If the supply is interrupted (or insufficient) for, eg., 60-120 seconds, the engine may overheat and the engine may be irreparably damaged. If the interruption occurs for, eg., 4 minutes, the engine may seize and/or become unrepairable. Factors likely to affect flow of cooling fluid and pressure levels in cooling systems (eg., sea water cooling) include:

1. Blockage of cooling water inlets: eg., by plastic bags/seaweed/flotsam.

2. Restriction of cooling water: a) partial blockage to system - due to sand, mud, rust, thermostat malfunction; b) restriction to cooling water flow exhaust outlet in wet exhaust systems; c) considerable carbon build-up restricting or blocking cooling water outlet; d) in the mixing chamber, where exhaust gases combine with cooling water.

3. Reduction in cooling water flow. a) related to water pump failure or drive belt failure or reduced efficiency due to impellor wear.

4. Hose failure or leaking: a) rubber hoses fail through combination of ageing embrittlement and fatigue - it is often difficult to detect hose deterioration.

5. Filter clogged or blocked: a) many systems incorporate filters on coolant inlets to avoid or ameliorate problems as indicated in (2) above. b) if not properly maintained, the filter itself can cause restriction and possible blockage to coolant flow.

SUMMARY OF THE INVENTION

All of the factors noted above are likely to affect engine operating temperature and coolant temperature, and will therefore be indicated by a correctly installed temperature gauge. The advantage of also monitoring coolant pressure is principally in rapid response time. A correctly adjusted and calibrated system will operate audible and/or visible alarms, preferably within 5 seconds of one or more of the following:

1. Blockage or significant (eg., 50% or greater) restriction to coolant flow. 2. Coolant pump failure or drive belt failure (significant loss of pump efficiency will be indicated by alarm triggering at idle or alarm failing to shut off at normal idle after engine warm up).

3. Hose failure and significant leaks will result in immediate pressure loss and alarm within 5 seconds. 4. (a) Restriction of coolant in: i) a filter; ii) the engine block; iii) thermostat malfunction; and/or (b) Coke/carbon build-up in a wet exhaust mixing chamber.

5. A suitable system may also: (a) indicate system pressure by utilising a barograph or LED system to show pressure levels during normal operation - this will provide instant useful information regarding cooling system health and early warning of any deterioration such as: i) impellor wear; ii) thermostat operation; and iii) restrictions developing. In conjunction with tachometer, it is possible to monitor cooling system pressure and therefore performance at varying operating speeds and load conditions. This condition watch will allow planned maintenance and significant reduce in-service failures with the associated very expensive consequential damage to major engine components by overheating.

It is a preferred object of the present invention to provide an alarm system for the cooling system of engines to warn of interrupted and/or insufficient coolant flow and/or to indicate restrictions causing over pressure in cooling system and/or indicate and monitor cooling system efficiency and the condition of high wear items, eg., coolant pump impellors.

It is a further preferred object to provide a system which generates an audible and/or visible alarm. It is a still further preferred object that the system has a delay to prevent false triggering of the alarm.

It may be a still further preferred object to provide a system which switches off the ignition, eg., 30 seconds after the critical condition has been monitored. It is a still further preferred object to provide a system which transmits pressure data (eg., digital) to an engine management computer allowing optimal management efficiency.

Other preferred objects will become apparent from the following description. In a broad aspect, the present invention resides in a cooling system alarm unit for fluid cooled internal combustion engines including: a pressure sensor; means to connect the pressure sensor to the cooling system of an engine to a visual alarm means and/or an audible alarm means; and a triggering circuit interconnecting the pressure sensor to the alarm means; so arranged that when the pressure of the coolant in the cooling system fails below a preset value, the pressure sensor causes the triggering circuit to switch on the alarm means and the circuit will also

(optionally) include the instantaneous pressure whilst the engine is operating.

The pressure sensor and the triggering circuit may be mounted in a box gauge or housing behind the operator's console, or in the engine compartment, or directly on the engine. The audible alarm, which may comprise a buzzer or bell, may also be mounted in the box gauge or housing. The visual alarm means, which may comprise a LED or incandescent globe is preferably mounted in the console in clear view of the operator.

Preferably, the pressure sensor causes the triggering circuit to switch on the alarm(s) when the coolant pressure falls below approximately 27KPa (4 psi) (or rises above 200KPa (30 psi)).

Preferably, the system incorporates a barograph which accurately represents the instantaneous operating pressure in the cooling system.

Preferably, a plastic or rubber hose connects the inlet port of the pressure sensor to the cooling system, preferably, but not necessarily downstream of the coolant pump (and preferably upstream of the engine).

Preferably, in some applications, the sensor may be directly mounted to the engine and electrically connected to control circuitry which would be located remote from the engine. Preferably, the triggering circuit has a built-in delay of, eg., 5 seconds, so that the alarm(s) will not be triggered when the coolant pressure drops below or goes above the preset level for a transient period.

The triggering circuit may be connected to a relay in the engine's ignition to switch off the engine if the critical condition is monitored for, eg., 30 seconds, and the engine is not shut off by the operator. This facility may be omitted, or be by-passed by a manual override switch, eg., on watercraft, which regularly cross bars or manoeuvre in close quarters as the sudden loss of power in poor sea conditions may be more dangerous than any damage to the engine due to the interrupted coolant water flow; or land vehicles where engine shut-down could result in loss of control. With the addition of analogue/digital convertor, it is envisaged that the sensor and control circuitry could be coupled to engine management computers which could control cooling system and engine efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 is a schematic layout of the installation of a first embodiment of the alarm unit;

FIG 2 is a circuit diagram of the electronics therefor;

FIG 3 is a schematic layout of a second embodiment;

FIG 4 is a circuit diagram therefor;

FIG 5 is a schematic layout of a third embodiment; and FIGS 6A and 6B is the circuit diagram therefor.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENTS

Referring to FIGS 1 and 2, the alarm system 10 of the first embodiment has a box 11 mountable behind the dash of the operator's console and the alarm system is powered by the watercraft's 12V (or 24V) DC battery 12.

A pressure sensitive switch 13, which operates when the pressure monitored at its input port 14 is below, eg., 27KPa (4 psi), is mounted in the box 11 and its input port 14 is connected to the engine cooling system 15 via a plastic hose 15. It is preferred that the coolant pressure is monitored downstream of the coolant pump, and the hose 16 may be tapped into the coolant system at or upstream of the power head of the engine.

A bell or buzzer 17, providing an audible alarm, is mounted in the box 11 and an LED 18 is mounted in the console dash to provide a visible alarm.

A triggering circuit 19 interconnects the switch 13 to the alarms

17, 18, and will switch the alarms "on" when the pressure in the hose 16 falls below the preset value and is detected by the switch 13. A 5-second delay, generated in the triggering circuit, prevents false triggering of the alarms due to transient pressure drops in the cooling system 15 below the preset value.

When the operator hears and/or sees the alarm 17, 18, he/she can switch off the engine before damage occurs.

The alarm will not only detect an interruption to the coolant flow, eg., due to the blockage of the inlet(s) by rubbish, but will also detect total or partial failure of the water pump, eg., where wear in the pump reduces its capacity below the preset pressure level.

Referring now to FIGS 3 and 4, the alarm system 10a of the second embodiment has a housing/gauge 11a mountable in the dash of the operator's console and the alarm system is powered by the vehicles 12V DC battery 12a.

A pressure sensitive sensor 13a, which operates when the pressure monitored at its input port 14a is below, eg., 27 KPa (4 psi) is mounted in the instrument case gauge and its input port 14a is connected to the engine cooling system 15a via a plastic hose 16a. It is preferred that the coolant pressure is monitored downstream of the coolant pump, and the hose 16a may be tapped into the coolant system at or upstream of the power head of the engine.

A bell or buzzer 17a, providing an audible alarm, can be mounted in the instrument case 11a and a LED 18a is mounted in the console dash to provide a visible alarm.

A triggering circuit 19a interconnects the sensor 13a to the alarms 17a, 18a and will switch the alarms "on" when the pressure in the hose 16a falls below the preset value and/or is detected by the switch 13a. A 5-secoπd delay, generated in the triggering circuit, prevents false triggering of the alarms due to transient pressure drops in the cooling system 15a below the preset value.

When the operator hears and/or sees the alarm 17a, 18a, he/she can switch off the engine before the damage occurs.

In the third embodiment of FIGS 5, 6A and 6B, the alarm system 1 is incorporated in a case (instrument type) which can be dash- mounted or can be remotely mounted with alarms remote mounted for maximum detectability. The alarm system is powered by engine 12V or 24V battery 2 via voltage regulator/current limiter 3.

A pressure sensitive (piezo-resistive) sensor 4, which senses pressure monitored at its input port, is connected to the engine cooling system between the coolant pump and the engine block coolant jacket or heat exchanger via a high pressure small diameter flexible hose. (The sensor 4 may also be direct mounted to the engine.) The signal is fed 5 via electronic calibration and amplification circuits 6 in which it is possible to calibrate in the range of 0-200 Kpa (0-30 psi) in ten steps. This output is then fed to barograph driver circuit 7 and alarms comparator 8. The output from the driver circuit 7 is then fed to the visible display 10 which comprises up to ten LED's or the barograph. Within the alarm comparator 8, upper and lower alarm levels can be electronically set over 200 Kpa (28 psi). The comparator 8 feeds triggers into alarms generator circuit 9 which in turn feeds audible alarm/s 11.

It will be readily apparent to the skilled addressee that the alarm system is applicable to all fluid cooled internal combustion engines and provides a simple, inexpensive protection against expensive damage due to overheating of an engine. With the third embodiment (of FIGS 5, 6A and 6B) in conjunction with other engine instruments (eg., a tachometer), it is possible to monitor conditions of cooling systems under various operating conditions of speed and loading allowing for cost effective planned maintenance significant reducing in-service failures with their associated very expensive consequential damage to engines by overheating. It is also envisaged that suitably processed outputs from the analogue/digital convertor 12 of the coolant pressure alarm could be input into an engine management computer 13, allowing efficient control of engine combustion and cooling system.

While only one triggering circuit has been shown, which is triggered by the sensor when the coolant pressure drops below a preset level, the sensor can be connected to a second such circuit which operates the alarm(s) when the pressure exceeds a preset level, ie., to indicate a blockage in the coolant system.

The system of the present invention is much more reliable than known unit which rely on mechanical sensors, which have a high failure rate.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

Claims

CLAIMS:

1. A cooling system alarm unit for fluid cooled internal combustion engines including: a pressure sensor; means to connect the pressure sensor to the cooling system of an engine to a visual alarm means and/or an audible alarm means; and a triggering circuit interconnecting the pressure sensor to the alarm means; so arranged that when the pressure of the coolant in the cooling system falls below a preset value, the pressure sensor causes the triggering circuit to switch on the alarm means, and the circuit will also

(optionally) include the instantaneous pressure whilst the engine is operating.

2. A unit as claimed in Claim 1 wherein: the triggering circuit, or a second triggering circuit, switches on the alarm means when the pressure of the coolant exceeds a preset level.

3. A unit as claimed in Claim 1 or Claim 2 wherein: the pressure sensor and the triggering circuit are mounted in a box gauge or housing behind the operator's console, or in the engine compartment, or directly on the engine.

4. A unit as claimed in Claim 3 wherein: the audible alarm, which comprises a buzzer or bell, is also mounted in the box or housing.

5. A unit as claimed in Claim 3 wherein: the visual alarm means, which comprises a LED or incandescent globe, is mounted in the console in clear view of the operator.

6. A unit as claimed in any one of Claims 1 to 5 wherein: the pressure sensor causes the triggering circuit to switch on the alarm(s) when the coolant pressure falls below approximately 27 Kpa (4 psi) or rises above 200 Kpa (30 psi)).

7. A unit as claimed in Claim 6 wherein: the unit incorporates a barograph, which accurately represents the instantaneous operating pressure in the cooling system.

8. A unit as claimed in Claim 1 wherein: a plastic or rubber hose connects an inlet port of the pressure sensor to the cooling system, optionally downstream of the coolant pump (and optionally upstream of the engine).

9. A unit as claimed in Claim 1 wherein: the pressure sensor is directly mounted to the engine and electrically connected to control circuitry located remote from the engine.

10. A unit as claimed in Claim 9 wherein: the sensor is a piezo-resistive sensor.

11. A unit as claimed in any one of Claims 1 to 10 wherein: the triggering circuit has a built-in delay of, optionally, 5 seconds, so that the alarm(s) will not be triggered when the coolant pressure drops below, or goes above, the preset levels for a transient period.

12. A unit as claimed in Claim 11 wherein: the triggering circuit is connected to a relay in the engine's ignition, to switch off the engine, if the critical condition is monitored for, optionally, 30 seconds, and the engine is not shut off by the operator.

13. A unit as claimed in Claim 1 wherein: the relay can be by-passed by a manual override switch.

14. A unit as claimed in Claims 1 to 13 wherein: a digitised output from the pressure sensor is fed to a programmed engine management computer, which in turn controls engine temperature and coolant flow allowing optimum cooling of the engine.