GB2574623A

GB2574623A - Method to determine the use of a block heater in an engine

Info

Publication number: GB2574623A
Application number: GB1809663.6A
Authority: GB
Inventors: Maiello Eduardo; Schoof Erik; Gandolfi Loïc; Tascedda Luca
Original assignee: Delphi Automotive Systems Luxembourg SA
Current assignee: BorgWarner Luxembourg Automotive Systems SA
Priority date: 2018-06-13
Filing date: 2018-06-13
Publication date: 2019-12-18
Also published as: GB201809663D0

Abstract

A method for determining use of a block heater in an internal combustion engine. The method first measures the temperature of a coolant after the start of the engine S2, then determines if there is a drop in said temperature S4. If a drop is detected, then an integral of the temperature difference between the measured temperature and a reference temperature with respect to time is taken S5 and compared to a predetermined threshold value S6. If the integral value is larger than the threshold value, then a block heater has been used S7. The reference temperature may be the start temperature of the coolant.

Description

METHOD TO DETERMINE THE USE OF A BOCK HEATER IN AN ENGINE

TECHNICAL FIELD

This invention relates to a method of determining whether a block heater has been used in an engine prior to engine start.

BACKGROUND OF THE INVENTION

In a conventional automobile, a block heater is a standalone accessory used to heat the coolant fluid inside the engine block or in any area of the coolant circuit. This device is mostly used in geographic regions with cold temperatures because heating the engine coolant can ease starting an engine.

The operation of an engine block heater, however, can disturb the on-board diagnostics (OBD) of rationality of temperature sensors, thus, there is a need for a method for detecting a presence of a block heater in an automobile.

Prior art methods for determining engine malfunctions have tried to determine whether a block heater is present and has been used by checking for a temperature difference between the engine coolant and the intake manifold air or ambient temperature, when the engine has been stopped for a minimum period; other methods have tried to determine the presence of the block heater by checking for a temperature drop in the engine coolant temperature after a period of time after engine start.

US6931865B1: Method and apparatus for determining coolant temperature rationality in a motor vehicle. US7975536B2 relates to a method to detect the presence of a liquid-cooled engine supplemental heater. US8140246B1 describes a method and system for detecting a presence of a block heater in an automobile. US7757649B2 describes a controller, cooling system abnormality diagnosis device and block heater determination device of internal combustion engine.

The methods of detection of a block heater used by the prior art are not reliable enough or cannot be used under certain circumstances. In case the coolant temperature sensor has a fault, detectable by OBD monitors, all the detection methods developed on prior art that rely only on this sensor cannot be used. In case the engine is equipped with an electronic controlled thermostat valve or a forced circulation block heater, that will allow the coolant fluid to circulate over the entire cooling circuit, allowing a homogenous distribution of the temperature on the system, the known detection methods simply based on a drop of the coolant temperature after engine start are not always reliable. On both circumstances the methods of detection developed on the prior art are not able to guarantee a reliable detection of the block heater.

Because the problems with the prior art are present on more advanced engines which use electronic controlled thermostat valves, which allow the coolant fluid to flow through all the coolant circuit independent of the coolant fluid temperature, these valves are yet only used on few engines because they were developed recently, on the next years they might become common on several engines. The problem is also present on engines that are equipped with forced circulation block heaters, which usually have a pump to force the coolant to flow through the system in order to have a better or more homogeneous temperature distribution on the coolant circuit, which will also prevent the prior art to detect the presence of a block heater.

The conventional methods are dependent on the relative position of the engine coolant temperature sensor relative to the block heater. However, these conventional methods can be inadequate depending on the configuration of the automobile and/or the placement of the block heater.

SUMMARY OF THE INVENTION

In one aspect is provided a method of determining whether a block heater has been used prior to starting an internal combustion engine comprising;

a) monitoring the temperature with time of the coolant subsequent to the start of the engine;

b) determining whether there is a subsequent drop in said temperature after starting;

c) if a temperature drop is determined in step b), during a period in the drop phase, integrating the temperature difference (Tref-T) between a reference temperature Tref and the measured temperature T, between first and second time points (ts, te), to provide an integral value,

d) determining if said integral value becomes larger than a predetermined threshold (thf).

e) if step d) is fulfilled, indicating a block heater has been used

The method may include determining the temperature T1 and corresponding timepoint tl at which the temperature drops.

The reference temperature (Tref) may be the start temperature, (Tl).

Said integration may start at time point tl.

The method may include the step of determining if the coolant temperature subsequent to the drop goes back to the level of the temperature Tl or forms a local maxima.

The method may include determining the time t3 when the coolant temperature subsequent to the drop goes back to the level of the temperature Tl or forms a local maxima.

Said integration may end at time-point t3 or before.

The reference temperature (Tref) may be the temperature Tl minus a fixed offset A.

The integration start point ts may occur when the temperature of the coolant drops to the level of Tref, and/or finishes when temperature of the coolant rises to the value of Tref.

It may be determined if a temperature drop detected in step b) occurs within a preset time period from engine start.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- Figure 1 shows the coolant temperature and other parameters subsequent to starting an engine, against time, after a block heater has been used previously.

- Figure 2a shows a plot 1 of coolant temperature T around the drop phase in more detail.

Figure 2b shows the integral value of (reference temperature (Tref) temperature of the coolant (T))

- Figure 3 shows a flowchart of one example of the methodology.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a method for detecting a presence of a block heater in an automobile, based on monitoring the behavior of the engine coolant temperatures during cranking and running phases of the engine.

The invention detecting the use of a block heater even in applications in which no drop of the coolant temperature is noticed immediately after engine start, due to the relative positions of the (engine coolant temperature) sensor and the block heater, or due to a homogenous distribution of the temperature of coolant fluid on the system, that can be seen on the most recent engines equipped with an electronic controlled thermostat valve and/or forced circulation block heater.

The problem of lack of robustness or incapacity of detecting the presence of a block heater in the engine is solved by using methodology that monitors the coolant temperatures, which is also reliable when used on engines equipped with electronic controlled thermostat valves and/or forced circulation block heaters. Analysis of the coolant temperature enables determination if a block heater was used.

When a block heater has been used, under these conditions, in most applications, the coolant temperature will increase quickly up to a certain level, and then a sudden drop is observed, before the coolant temperature increases again, exceeding the previous maximum value. Thus there is a drop or decrease of the coolant temperature sometime after engine is cranked and the water pump is actuated. This phenomenon, shown on figure 1, and is used in prior art systems to detect the use of a block heater; this happens because the temperature distribution in the cooling system is not homogenous. However as mentioned this is not ideal.

In aspect of the invention rather than look at the value of absolute temperature drops in coolant temperature, the extent or nature of the drop is determined by integration methods.

Figure 1 shows the coolant temperature and other parameters subsequent to starting an engine, against time, after a block heater has been used previously. Specifically reference numeral 1 shows the coolant temperature of an engine against time, after the engine (at time tO) has started (after cranking), and after a block heater has been used prior to starting. As can be seen when a block heater has been used, the coolant temperature rises until time point tl, there is a local maxima, and thereafter, there is a drop in temperature to a local minimum at time point t2 and then it rises again. The temperature then increases and increases; at time point t3 this is back to a level of that of time point tl

The “drop” phase is to be regarded as the period between time points tl and t3. In embodiments of the methodology, during any period of time within this time period, an integral of the difference between a set temperature and the coolant temperature is determined, and when or if this exceeds a threshold thr, the use of a block heater is determined. The set temperature may be the temperature at tl (Tmax=Tl) i.e. the temperature of the local maxima. Or it may be the temperature at tl (Tmax/Tl) minus a offset value A, in advanced embodiments, as will be explained hereinafter.

Basic Example

Figure 2a shows a plot 1 of coolant temperature T around the drop phase in more detail. Figure 2b shows the integral value 2 of (reference temperature (Tref) temperature of the coolant (T)) which in this example is determined from the timepoint tl (started at this point). In this case the reference temperature value Tref is the same as the temperature at point tl (=Tmax). Thus the bottom chart shows f (Tref-T) or f (Tmax-T), started at time-point tl.

If and when this integral value reaches a threshold value thr, at time-point td, the use of a block heater is determined. The bottom point 2b shows the aforementioned integral value and it achieves a threshold value thr at time point td. If the threshold value is not achieved, because the magnitude/duration of the drop is small the detection of a block heater will not be triggered.

In general the period of time over which the integral is determined starts at time point tl or any time thereafter and finishes at a time point before time t3. If the integral becomes more than a threshold value, the use of a block heater is indicated. Thus the integration only takes part in the drop phase, that is between tl and t3. The integral may be determined until the time point t3 where the temperature rises up to the value of maxima tl. The shaded area shows the integral value from time points tl to td.

Refined Example

Referring back to figure 1, in a further advanced embodiment an offset A is used in order to ignore small/shallow dips in temperature; i.e. a small drop region, to increase accuracy. Here the value of the temperature Tmax of the coolant at time point tl minus the offset value A is used as the constant temperature reference value (Tref) and the difference between this Tref (constant value) and the coolant temperature is integrated over a time period within the drop phase. Again is and when the integral value reaches or goes beyond a threshold value thr, the use of a block heater is indicated.

Preferably the integration is not started until the time point ts which is when the temperature of the coolant falls to value of Tref that is (temperature at tl (Tmax) offset A). Thus the integral value is determined from time-point ts. The integration can be up to time point te, when the temperature goes back up to Tref. Of course if the value of the integral reaches the threshold thr the integration process is stopped and the determination of use of a block heater is made.

Thus the following integral is calculated, and is shown by reference numeral 2 in figure 1.

Integral of coolant temperature drop =

J[( coolant temperature at (maxima tl) — offset Λ) — current coolant temperature T] dt or f((Tmax — A) —T) dt or f(Tref — T) dT

Again if and when the value of this integral exceeds a calibratable threshold (thr), the use of a block heater is confirmed.

In the example in the figure 1 this integral value reaches the value of thr at time point td. At this time the detection threshold is thus reached and the use of a block heater is flagged up i.e. determined.

The shaded area in figure 1 shows the integral value from time points ts and te. It is to be noted that the threshold value to trigger block detection (thr) may be achieved before t3 or that even at t3 the threshold value may not be reached.

The bottom two plots of figure 1 show the logic in methodology. Plot 3 show the logic resulting from the determination of whether the temperature drops by a predetermined amount. If so the logic signal indicates that there is a suspicion that a block heater may have been used. Plot 4 shows the logic from the determination above i.e. if the integral is above a threshold. If this is so than the suspicion that a bock heater may have been used is confirmed. This arises at point td in the figure.

Figure 3 shows a flowchart of one example of the methodology. In step SI the block heater detection starts. In step S2 the temperature of the coolant at engine start (crank) is determined. At step S3 it is determined whether the block heater detection is to be enabled. This depends on whether certain criteria, i,e, conditions are fulfilled which will be explained later. If yes the method proceeds to step S4 where the temperature of the coolant is monitored with time and it is determined that after an increase in temperature, (from crank time tO) there is a decrease in temperature coolant (thus whether a local maxima has been reached). At step S5 the difference between the reference temperature and coolant temperature is integrated, from a time point at or after tl (at the point of the local maxima). The so computed integral value is continually determined and monitored. At step S6 it is determined whether the integral value from step S5 reaches a threshold thr. If so at step S7 it is determined that a bock heater has been used. The block heater detection is then ended at step S9. If at step S6 the results were “no” then and the temperature goes back up to the maxima level it is determined at step S7 that no block heater has been detected.

Before running the above mentioned methodology there may be a check to ensure there are no faults with the temperature sensor, whether the engine has been off for more than a predetermined time, whether the engine has stopped more times than a threshold number. Before carrying out the check when the engine has started there may be a check to determine if there has been sufficient soak time. There may be a test to see whether the engine has been running for sufficient time e.g. by seeing if the fuel quantity injected since engine start up (crank) is more than a predetermined threshold. There may be a check to see whether the measured temperature of the coolant is different enough (e.g. by a threshold) from the ambient temperature.

In the prior art, the detection of a block heater was only based on verification of differences between the readings of coolant and air temperature sensors before engine was cranked or started, which is not always possible to be differentiated from OBD-II rationality errors on the sensors.

This invention uses an algorithm that evaluates the behavior of the coolant temperature during engine cranking and running phase to effectively determine if a block heater was present or not. The detection is also reliable when the engine is equipped with electronic controlled thermostat valves and/or forced circulation block heaters, which will prevent the methods used by prior art from detecting the presence of a block heater.

The advantage of this invention compared to the prior art is the improvement in the robustness of the detection of the presence of a block heater on the engine by using an efficient algorithm to verify the behavior of the ambient, coolant temperatures also during the engine cranking and starting phases. This invention can also be used on engines equipped with electronic controlled thermostat valves and/or forced circulation block heaters, which are recent technologies and will be used on several engines in the future.

Claims

1. A method of determining whether a block heater has been used prior to starting an internal combustion engine comprising;

d) determining if said integral value becomes larger than a predetermined threshold (thr).

e) if step d) is fulfilled, indicating a block heater has been used

2. A method as claimed in claim 1 including determining the temperature T1 and corresponding time-point tl at which the temperature drops

3. A method as claimed in claim 2 where the reference temperature (Tref) is the start temperature, (Tl).

4. A method as claimed in claim 2 or 3 where said integration starts at time point tl.

5. A method as claimed in claims 2 to 4 including the step of determining if the coolant temperature subsequent to the drop goes back to the level of the temperature Tl or forms a local maxima.

6. A method as claimed in claim 1 to 5 including determining the time t3 when the coolant temperature subsequent to the drop goes back to the level of the temperature Tl or forms a local maxima.

7. A method as claimed in claim 6 where said integration ends at time-point t3 or before.

5

8. A method as claimed in claim 1 to 7 where the reference temperature (Tref) is the temperature Tl minus a fixed offset A.

9. A method as claimed in claim 1 to 8 wherein it is determined if a temperature drop detected in step b) occurs within a preset time period from engine start.

9. A method as claimed in claim 1 to 8 where the integration start point ts occurs when the temperature of the coolant drops to the level of Tref, and/or 10 finishes when temperature of the coolant rises to the value of Tref.