GB2291721A

GB2291721A - Method of and control means for controlling an internal combustion engine

Info

Publication number: GB2291721A
Application number: GB9514478A
Authority: GB
Inventors: Berndt Schott; Klaus Joos
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-07-22
Filing date: 1995-07-14
Publication date: 1996-01-31
Anticipated expiration: 2015-07-14
Also published as: ES2119648A1; DE4425986A1; ES2119648B1; KR100378451B1; GB9514478D0; JPH0849588A; JP3980669B2; GB2291721B; DE4425986B4

Description

METHOD OFAND CONTROL MEANS FOR CONTROLLING 2291721 AN INTERNAL COMBUSTION

ENGINE The present invention relates to a method of and control means for controlling an internal combustion engine.

A method and control means for controlling an internal combustion engine are known from, for example, US 3 470 854. In this publication, a method for controlling an internal combustion engine with a fuel pump is also described. In this method, the fuel pump is switched off when the engine speed drops below a threshold value. 10 However, there remains a need for a method Ofand control means for controlling an internal combustion engine in which a fuel pump can be switched on as quickly as possible and thus build up pressure quickly for a short starting time of the engine. Preferably, the method and control means shall be such as to prevent interference signals 41:rom causing the fuel pump to be switched on. According to a first aspect of the present invention there is provided a method of controlling an internal combustion engine with a fuel pump, characterised in that it is tested whether a voltage condition is fulfilled, or in that it is tested whether a voltage condition is fulfilled and an engine-speed value lies within an acceptable range, and in that the fuel pump is activated if at least one of the conditions is fulfilled.

Preferably, the fuel pump is activated if at least one engine-speed value or one mean value of at least two engine-speed values lies between a minimum value and a maximum value.

For preference, a first and a second voltage value are detected at two successive times, the fuel pump being activated if the difference between the first and the second voltage values is greater than a threshold value. The first voltage value is preferably detected before a starter is energised and the second voltage value is preferably detected when a first engine-speed signal occurs or after a prescribed time period has elapsed.

According to a second aspect of the invention there is provided control means for controlling an internal combustion engine with a fuel pump, characterised in that means are provided which test whether a voltage condition is fulfilled or which test whether a voltage condition is fulfilled and an engine-speed value lies within an acceptable range, and with means which activate the fuel pump if at least one of the conditions is fulfilled.

With a method exemplifying and control means embodying the present invention, it is possible to reduce the time for building up the fuel pressure by evaluating the supply voltage. At the same time, incorrect switching on of the fuel pump by interference signals may be able to be prevented.

An exampleof theffethod'and an embodiment of the control means of the present invention will now be more particularly described with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram of an internal combustion engine and associated fuel pump control system; Fig. 2 is a diagram showing signals utilised in the control system; and Fig. 3 is a flow chart showing steps in performance of a method exemplifying rne invention by way of such a control system.

Referring now to the drawings there is shown in Fig. 1 an engin e control system in which fuel is metered to an internal comoustion engine via a fuel metering device 105. A fuel pump 110 feeds the fuel from a reservoir container 115 and supplies it to a fuel metering device 105. The fuel metering device 105 and the fuel pump 110 are provided with actuation signals by a control device 120.

The control device 120 is preferably provided with supply voltage Ubat (Fig. 2) from a battery 130. Furthermore, the battery 130 is connected via switching means 135 to a starter 140. A signal transmitter 145, which is arranged on the internal combustion engine 100, issues signals which are sensed by a sensor 150, which in turn feeds a corresponding engine-speed signal N (Fig. 2) to the control device.

The system operates as follows: The starter 140 is provided with voltage as a result of the switching means 135 being activated by the driver. The starter 140 drives the engine 100, which leads to the engine starting. As a result of the crankshaft rotation of the engine 100, the signal transmitter 145 also rotates and the sensor 150 detects the engine-speed signals N which are produced during this process and passes the enginespeed signals N on to the control device 120.

Various sensors (not illustrated) detect characteristic operating variables. On the basis of these variables the control device 120 calculates signals which determine the injected quantity of fuel and are intended to be fed to the fuel metering device. Furthermore, the control device 120 provides the fuel pump 110 with a signal, so that the fuel pump 110 feeds fuel from the reservoir container 115.

In Fig. 2, the output signal of the sensor 150 is plotted above, and the supply voltage UBat is plotted below, against time t. Shortly after a time to, the switching means 135 is closed and the starter is activated. This leads to a severe drop in the supply voltage UBat. At a time tl, a first negative edge of the output signal of the sensor 150 occurs. At a time T2, a further negative edge of the output signal of the sensor 150 occurs. The same applies for a time t3- The steps of a method exemplifying the invention are illustrated in Fig. 3. In a first step 300, the supply voltage UBat is measured at the time to. At a step 310, the switching means 135 is closed. The starter is energised with the closing of the switching means 135.

The first'. value U(to) of the supply voltage must be measured at a time at which the starter current still has no influence on the supply 10 voltage. The value U(to)of the supply voltage at the time to is stored.

At a later time, a second value U(t1) of the supply voltage is detected in a step 320. The time tl is preferably the time at which the first negative edge of the output signal N of the sensor 150 occurs. Subsequently, at a step 330, the difference U = U(t1) - U(to) is determined.

If, in a following interrogation step 340, it is detected that the difference M is greater than a threshold US, the fuel pump 110 is energised in a step 350. If this is not the case, a step 360 follows, in which the time t2 of the occurrence of the second negative edge of the signal N is detected.

Subsequently, in a step 370 the time t3 at which the third negative edge of the engine-speed signal N occurs is determined. In a step 380, a first engine-speed value Nj and a second engine-speed value N2 are calculated as a function of the times tl and t2 and the times t2 and t3, respectively. Subsequently, it is tested in an interrogation step 390 whether the mean value N1+N2/2 of the two engine-speed values lies between a minimum Nmin and a maximum Nmax value. If this is the case, the fuel pump is energised in the step 350. By means of this interrogation it is tested whether the evaluated signals are actually engine-speed pulses. If interferences pulses occur, the mean enginespeed value lies outside the acceptable range defined by Nmin and Nmax.

It is particularly advantageous if the first engine-speed value NI is determined directly after the step 360 and the interrogation step 390 tests whether this value lies in the acceptable range.

If interference pulses occur, a step 400 follows in which the system waits for the next pulse of the engine-speed signal which occurs at the time t4. Instead of the value for the time tl, the value of the time t'? is used, and instead of the value for the time t2 the value of the time t3 is used. The time t4 occurs in place of the time t3- Subsequently, the two engine-speed values NI and N2 are calculated again in the step 380 on the basis of the times t2, t3 and t4.

By virtue of the fact that the fuel pump 110 is energised when one of the two conditions for the supply voltage, or for the engine speed, is fulfilled, it is possible for the fuel pump 110 to be energised at a very early time. By evaluating a mean value for the engine speed it is possible to reliably prevent incorrect energising which is caused by interference signals.

Alternatively, there may also be provision that not the negative edges but rather the positive edges of the output signal N of the sensor 150 are correspondingly evaluated.

Furthermore, it is possible that in the step 320 the voltage is detected not when the first negative edge occurs but rather after a prescribed time.

It is particularly advantageous that it is tested whether a voltage condition is fulfilled or alternatively whether a voltage condition is fulfilled and an engine-speed value lies within an acceptable range. The fuel pump is activated if one of the conditions is fulfilled.

r

Claims

1. A method of controlling an internal combustion engine, comprising the steps of checking for fulfillment of an engine supply voltage condition or fulfillment of an engine supply voltage condition in conjunction with location of engine speed within a predetermined acceptable range and activating a fuel pump supplying fuel to the engine in response to ascertaining fulfillment of at least one of the conditions.

2. A method as claimed in claim 1, wherein said engine speed is represented by at least one actual engine speed value or by a mean value of at least two such actual values and the range is defined by a predetermined minimum value and a predetermined maximum value.

3. A method as claimed in claim 1 or claim 2, wherein the firstmentioned voltage condition is represented by the exceeding of a predetermined threshold value by the difference between first and second values of the voltage respectively detected at successive instants in time.

4. A method as claimed in claim 3, wherein the first voltage value is detected prior to energisation of a starter of the engine.

5. A method as claimed in claim 3 or claim 4, wherein the second voltage value is detected after a predetermined period of time has lapsed following detection of the first voltage value or when an engine speed signal occurs.

6. A method as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

7. Control means for controlling an internal combustion engine, comprising means for checking for fulfillment of an engine supply voltage condition or fulfillment of an engine supply voltage condition in conjunction with location of engine speed within a predetermined acceptable range and means for activating a fuel pump supplying fuel to the engine in response to ascertaining fulfillment of at least one of the conditions.

8. Control means as claimed in claim 7 and operable to perform the method claimed in any one of claims 2 to 6.

9. Control means substantially as hereinbefore described with reference to the accompanying drawings.

10. A motor vehicle comprising an internal combustion engine and control means as claimed in any one of claims 7 to 9 for controlling the engine.