GB2176028A

GB2176028A - Fuel injection apparatus

Info

Publication number: GB2176028A
Application number: GB08612481A
Authority: GB
Inventors: Hidekazu Oshizawa
Original assignee: Diesel Kiki Co Ltd
Current assignee: Bosch Corp
Priority date: 1985-05-23
Filing date: 1986-05-22
Publication date: 1986-12-10
Also published as: JPS61268844A; DE3617329A1; GB8612481D0; KR930011045B1; JPH07116975B2; DE3617329C2; KR860009231A; GB2176028B

Abstract

In a fuel injection pump which is capable of adjusting the fuel injection quantity by the ON/OFF control of a solenoid valve 7, the solenoid is driven by a first pulse in response to an injection timing signal and by a subsequent second pulse whose duration depends upon the desired fuel quantity. The second pulse is administered when it is detected that the valve has responded to the first pulse. Such control is accurate since it accounts for the delay in operation of the valve in response to the first pulse. <IMAGE>

Description

SPECIFICATION Fuel injection apparatus The present invention relates to a fuel injection apparatus, and more particularly to a fuel injection apparatus which is capable of adjusting the amount of fuel injection by controlling the opening/closing operation of a solenoid valve which is provided between a high-pressure chamber and a lower pressure portion of a fuel injection pump.

In the prior art, there is proposed, for example, a fuel injection apparatus which has a solenoid valve located between a high pressure chamber and a lower pressure portion of a distribution-type fuel injection pump, in which the high pressure chamber is made to communicate with the lower pressure portion or alternatively to disconnect from the lower pressure portion by means of the opening/closing operation of this solenoid valve, thereby regulating the amount of fuel injection that can be performed.

With this type of fuel injection apparatus, as well as setting the start time of fuel injection to a desired time by means of adjusting the timing of the application ofthe driving pulse for opening/closing the solenoid valve, the amount of fuel injection can be set to a desired value by adjusting the pulse width of the driving pulse. Consequently, the apparatus is able to control both the amount of fuel injection and the advance angle of fuel injection only by the adjustment of the driving pulse.

In order to realize high accuracy fuel supply control with the use of the above-mentioned fuel injection apparatus, however, it is necessary to perform exact opening/closing control of the solenoid valve. To do this, Japanese Patent Public Disclosure No. Sho 53-99134 (99134/78) discloses a fuel injection apparatus in which the opening/closing operation of the solenoid valve is performed by taking into consideration the closing delay time between the time which the driving signal is applied thereto and when the solenoid valve actually operates.

However, in the conventional apparatus mentioned above, the opening/closing control of the solenoid valve cannot be performed with precision due to the fact that the opening delay time of the solenoid valve is not considered at all, and consequently, the apparatus is unable to perform fuel supply control with high precision.

Summary of the invention It is an object of the present invention to provide an improved fuel injection apparatus which is capable of controlling the fuel supply from a fuel injection pump with high accuracy.

It is another object of the present invention to provide an electronically controlled type fuel injection apparatus able to take into account the control error due to the response delay of the solenoid valve for controlling the fuel supply and to control the fuel supply with utmost precision.

According to the present invention, in a fuel injection apparatus which includes a fuel injection pump having a solenoid valve located between a high pressure chamber and a lower pressure portion of the fuel injection pump so that the high pressure chamber can be communicated with the lower pressure portion of the fuel injection pump and is constructed to perform the control of injection of the fuel to be supplied to an internal combustion engine by means of the opening/closing control of the solenoid valve, the apparatus comprises a calculating means for calculating a target fuel quantity in accordance with the operating condition ofthe internal combustion engine and for outputting target data relating to the target fuel quantity, means for producing a timing signal relating to a desired timing of the beginning of fuel injection, a first means responsive to the timing signal for producing a first pulse signal for changing over the condition of the solenoid valve to enable a pressurizing operation of fuel in the high pressure chamber, and a signal generating means for generating a detection signal indicating the time the solenoid valve is changed over in response to the first pulse signal to a condition in which it is possible for fuel to be pressurized in the high pressure chamber.The apparatus further comprises a second means responsive to the detection signal and the target data for generating a second pulse signal with a pulse width corresponding to a driving period of said solenoid valve required for obtaining the target fuel quantity when the condition of the solenoid valve is actually changed over into a required condition in response to the first pulse signal, and a third means responsive to the detection signal for outputting a signal for causing the solenoid valve to be driven not in accordance with the first pulse signal but with the second pulse signal afterthe condition ofthe solenoid valve is changed over by the first pulse signal.

The timing signal may be supplied from, for example, an injection advance angle control unit which is provided separately, and the first pulse signal is produced in response to the timing signal.

When the first pulse signal is applied to the solenoid valve, the solenoid valve is changed over from a condition in which the high pressure chamber is communicated with the lower pressure portion of the fuel injection pump to a condition where the two parts are disconnected. Due to the response delay of the solenoid valve, a period of a few (ms) after the first pulse signal is applied is needed for the solenoid valve to completely disconnect the high pressure chamber from the lower pressure portion. This delay time is not necessarily constant and depends upon the condition of operation at that time (e.g. battery voltage, engine coolant temperature and the like).

The pulse width of the first pulse signal need only be long enough to assure a complete change over of the solenoid valve.

When the solenoid valve is changed over to the desired status by the application of the first pulse signal, the detection signal indicating this timing is, for example, output from a timing switch provided on the solenoid valve, and a second pulse signal is output in response to the occurrence of the detection signal. The second pulse has a pulse width adequate to assure application of driving voltage to the solenoid valve for the period required for supplying the pressurized fuel necessary for obtaining the target injection amount at each instant, and in response to the occurrence of the detection signal, the second pulse signal is used instead of the first pulse signal for the control ofthe solenoid valve.

As a result, after the solenoid valve is actually changed over to the desired status, its operation is dependent only on the second pulse signal. In other words, the period during which the high pressure chamber is disconnected from the lower pressure portion of the solenoid valve and supply of the pressurized fuel is carried out, is dependent on the pulse width of the second pulse signal. Because of this, even if the operation delay time of the solenoid valve varies due to a change in, for example, the battery voltage, the period of operation of the solenoid valve for supplying the pressurized fuel can still be accurately controlled regardless of the change.

The invention will be better understood and other objects and advantages thereof will be more apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

Brief description ofthe drawings Figure lisa block diagram showing an embodiment of a fuel injection apparatus according to the present invention; Figure 2 is a graph showing map data stored in the memory of the first converting unit shown in Figure 1; and Figures 3A to3G aretime charts for describing the operation of the apparatus shown in Figure 1.

Description of the preferred embodiments Figure 1 shows a block diagram of an embodiment of a fuel injection apparatus according to the present invention. The fuel injection apparatus 1 comprises a fuel injection pump 3 which is driven by a diesel engine 2 and injects a supply of fuel to the diesel engine 2. This fuel injection pump 3 is a distributiontype fuel injection pump, and a plunger 5 which is inserted in a plunger barrel 4 rotates with reciprocal movement according to the cam profile of a cam disc 5a driven by the rotational input power fro the diesel engine 2. As a result, the fuel pressurized within a high pressure chamber 6 is supplied under pressure to the individual cylinders of the diesel engine 2.In order to control the fuel quantity, this fuel injection pump 3 is provided with a normallyopened type solenoid valve 7, whereby the high pressure chamber 6 can be communicated with the lower pressure portion within the fuel injection pump 3. When no driving voltage is applied to the solenoid valve 7, and therefore the solenoid valve 7 is open, the high pressure chamber 6 is communicated with the lower pressure portion and the supply of pressurized fuel by means of the operation of the plunger 5 will not occur. On the other hand, if driving voltage is applied to the solenoid valve 7 in order to close it, the high pressure chamber 6 is disconnected from the lower pressure portion, fuel is pressurized within the high pressure chamber 6 in accordance with the movement of the plunger 5, and a condition in which pressurized fuel can be supplied develops.

If the solenoid valve 7 opens during the operation for supplying pressurized fuel, the pressure within the high pressure chamber 6 is released, and the fuel supply operation terminates. An injection pump which is constructed to control the timing of the start and termination of pressurized fuel supply by the use of a solenoid valve as stated above, is widely known, so that in Figure 1, only the main portions of the structure are shown, and the structural details are shown in simplified form.

In orderto detect the rotating state of the diesel engine 2, a rotation sensor 11 consisting of a pulser 9 and an electromagnetic pick-up coil 10 is associated with a driving shaft8 provided in the diesel engine 2 for driving the fuel injection pump 3. In the embodiment shown in Figure 1, the diesel engine 2 is a 4-cylinder 4-cycle engine, and the pulser 9 has 36 cogs provided on its periphery at 10 degree intervals. Therefore, a signal is output from the electromagnetic pick-up coil 10 every time the driving shaft 8 rotates 10 degrees.This signal is input to a speed detecting unit 12 as rotation signal SN, wherein the time interval between the pulses output from the electromagnetic pick-up coil 10 is measured in response to the rotation signal SN. As a result, speed data DN representing the speed of the diesel engine 2 at each instant is output on the basis of the measured result. The contents of speed data DN are renewed every time a signal is output from the electromagnetic pick-up coil 10; that is to say, every time the driving shaft 8 rotates by 10 degrees.

An acceleration pedal 13 is coupled with a transducer 14 for converting the amount of operation of the accelerator pedal 13 to a corresponding electric signal and acceleration data DA representing the amount of operation of the acceleration pedal 13 is output by the transducer 14.

The speed data DN and acceleration data DA are input to a target injection amount calculating unit 15 as data representing the operating condition of the diesel engine 2. In the target injection amount calculating unit 15, the optimum fuel injection quantity suited to the operating condition of the diesel engine 2 at each instant is calculated according to a map calculation based on predetermined map data, and data representing the result of this calculation is output as target injection amount data Qt. The target fuel injection amount data Otis represented in fuel volume per stroke of the plunger 5.

The target injection amount data Otis input to a first converting unit 16 to which the speed data DN iS also input. The first converting unit 16 has a memory 16a, in which data representing the relationship between the speed N of the diesel engine 2 and the angle 8 of the cam disc 5a necessary for obtaining the desired fuel injection quantity Q is stored.

Figure 2 is a diagram showing the characteristic curves of the relationship among data (3, N, and Q stored in memory 1 6a. For obtaining the value of angle 6which is necessary for obtaining the fuel injection quantity Q shown by data Qt when the rotational speed of the diesel engine is at N shown by data DN, the map calculation is carried out in the first converting unit 16 in accordance with the input data Qt and DN on the basis of data stored in the memory 16a. The data representing the result of this calculation is output as cam angle data De.

The cam angle data Do is input into a second converting unit 17 to which speed data DN is also applied. Data relating to the cam profile ofthe cam disc 5a is stored in advance in the second converting unit 17, and the cam angle data Do is converted therein into data T1 which represents a period corresponding to the cam angle 8 shown by cam angle data De, i.e., the time needed for the cam disc 5a to rotate 6 degrees. Time tQ shown by data T1 is the exact valve opening period of the solenoid valve 7 actually necessary for obtaining the fuel injection quantity shown by the injection amount data It at that time.

However, in order to obtain the exact valve opening period (to) of the solenoid valve 7, it is insufficient to set the pulse width of the driving pulse DP applied to an exciting coil 7a of the solenoid valve 7 at ta. That is, consideration must be given to the closing delay time tc, which is the period between the time when the driving pulse DP is actually applied to the exciting coil 7a and the time when the pressurization of fuel within the high pressure chamber 6 becomes possible due to the complete closure of the solenoid valve 7, and also to the opening delay time t,, which is the period between the time when the application of the driving pulse DP to the exciting coil 7a stops and the time when the solenoid valve 7 actually starts to open.

Because of this, the apparatus I has a first measuring unit 18 for measuring the closing delay time tc every time the solenoid valve 7 is closed, and a second measuring unit 19 for measuring the opening delay time to every time the solenoid valve 7 opens. First data DTI which represents the measured closing delay time tc and second data DT2 which represent the measured opening delay time t0, are output from the first and second measuring units 18 and 19, respectively.In this case, the closing delay time t0 is a value which represents the pulse width which should be added to the leading edge portion ofthe driving pulse DP in order to realize the desired actual opening time t0 of the solenoid valve 7 while, on the other hand, the opening delay time to is a value which represents the pulse width to be removed from the trailing edge portion of the driving pulse DP in order to realize the desired actual opening time tQ of the solenoid valve 7.

Data T1, DT1 and DT2 are added in an adder 20 according to the signal polarity shown in Figure 1 in order to obtain first pulse width data PW1 showing the desired pulse width of the driving pulse DP on the basis of data T1, DT1 and DT2. First pulse width data PW1 obtained from this calculation is input to a first pulse generating unit 21.

The first pulse generating unit 21 is constructed as a mono-stable multivibrator circuit which is able to set the pulse width of the output pulse in accordance with external signals. The first pulse width data PW1 is input to the first pulse generating unit 21 as an external signal for setting its output pulse width, and in response to a timing pulse TP1 output from a timing control unit 22, the first pulse generating unit 21 outputs a first pulse PS1 with a pulse width (=tc + tot0) determined by the first pulse width data PW1.

The timing control unit 22 is for performing the calculation for controlling the timing of the beginning of fuel injection. A reference pulse generator 23 is associated with the driving shaft 8 and is con structedto produce a reference pulse Prwhenthe driving shaft8 has reached a predetermined reference rotational position. A lift sensor 24 is provided for detecting when a valve needle of a fuel injection valve (not shown) lifts, the fuel injection valve being mounted on a predetermined cylinder of the diesel engine 2, and a lift pulse Pn is produced every time the valve needle is lifted due to the injection of fuel.

The timing control unit 22 receives the reference pulse Pr, the lift pulse P0 and the rotational signal SN and calculates an optimum timing for the beginning of fuel injection and generates the timing pulseTP1 at the time relating to the calculated optimum timing.

As previously explained, because of the fuel transmission delay within the injection pipe and the response delay of the solenoid valve 7, a time period tc is required for the timing pulse TP1 to be output and the actual injection of fuel to start. Therefore, the timing pulse TP1 is output from the first pulse generating unit 21 taking into consideration the delay time tc so that the first pulse PS1 is produced at the calculated optimum timing for the beginning of fuel injection in the timing control unit 22.

The first pulse PS1 is input through a switch 25 to an amplifier 26. The first pulse PS1 amplified by the amplifier 26, is output as the driving pulse DP and applied to the exciting coil 7a of the solenoid valve 7.

In the following, a detailed description of the first and second measuring units 18 and 19 will be given.

In order to measure the time tc, the first measuring unit 18 is supplied with the first pulses PS, obtained as described in the above and a detection signal S produced from a switch SW formed by a valve body 7b and a valve casing 7c of the solenoid valve 7. The switch SW functions so that it is in an ON state when the valve body 7b is seated on the valve seat 7d formed in the valve casing 7c, and so that it is in an OFF state when the valve body 7b is separated from the valve seat 7d.For this function to be realized, the switch SW is constructed in such a way in this embodiment that the rod portion 7f of the valve body 7b is guided by the valve casing 7c, and an insulation layer 79 is formed on the outer sliding surface ofthe rod portion 7f so as to maintain the electrically insulated condition between the outer sliding surface and the casing 7c. The valve casing 7c is grounded, and a predetermined level of voltage + V is applied through a resistor 27 and a spring shoe 7e to the valve body 7b. The spring shoe 7e is electrically insulated from the valve casing by an insulation layer 7h formed on one part of its surface, but is electrically connected through a return spring 7i to the valve body 7b. As a result, the voltage developed between the valve body 7b and ground in response to the opening/closing operation ofthe switch SW can be derived as signal S. Accordingly, the level of the signal S becomes ground level only when the valve body 7b is seated on the valve seat 7d, and when the valve body 7b is separated from the valve seat 7d, it becomes a predetermined high level. The timing ofthe level change of this signal S represents the actual timing of the opening or closing of the solenoid valve 7.

The first measuring unit 18 measures the period from the time when the level of the first pulse PS1 is changed from "L" to "H" to the time when the level of signal S changes from "H" to "L", and the data representing the delay time to for the closing ofthe valve obtained as a result of this measuring operation is output as the first data DT1.

Meanwhile, the second measuring unit 19 receives the output from switch 25 and the signal S and in the case where the apparatus is operating normally, the period from the time when the level of the first pulse PS1 is changed from "H" to "L" to the time when the level of signal S changes from "L" to "H" is measured. The data representing the delay time to for the opening ofthe valve obtained as a result of this measurement is output as the second data DT2.

The data T1 and the second data DT2 are inputto a pulsewidth decision unit 28 and calculation Of t0-T0 is executed on the basis of the data T1 and the second data DT2. Second pulse width data PW2 representing tQ-t0, is output therefrom. This second pulse width data PW2 represents the pulse width of the driving pulse DP needed to keep the solenoid valve 7 actually closed during the period ta represented by the data T1 after the solenoid valve 7 is driven in response to the first pulse PS, and actually closed.

The second pulse width data PW2 is input to a second pulse generating unit 29 constructed similarly to the first pulse generating unit 21 as data for determining the output pulse width for the second pulse generating unit 29. The second pulse generating unit 29 is also supplied with the detection signal S as a trigger signal and outputs a second pulse PS2 of a pulse width to - to in response to the change of the level of the detection signal S from "H" to "L".

The second pulse PS2 is input to the switch 25, and when the switch 25 is changed over from the state shown by the solid line to that represented by the broken line, the second pulse PS2 is input through the switch 25 to the amplifier 26, in place of the first pulse PS,.

To enable the switch 25 to perform the abovementioned switching operation, there is provided a switch control unit 30 which operates in response to the signal S. The switch control unit 30 operates so as to produce an "H" level signal on its output line 30a when the level of signal S changes from "H" to "L", and as a result, the switching condition of the switch 25 changes from that shown by the solid line to that shown by the broken line. The switching control unit 30 also operates so as to produce an "L" level signal on its output line 30a when the level of the detection signal S changes from "L" to "H" and the switch 25 is changed over as shown by the solid line.

Adescription ofthefuel adjusting operation ofthe fuel injection apparatus 1 shown in Figure 1 will be given with reference to the time charts shown in Figure 3A through Figure 3F.

When the level of the timing pulseTP1 output from the timing control unit 22 is changed from "L" to "H" at t = ta, in response to this, the first pulse PS1 is output from the first pulse generating unit 21 (Figures 3A and 3B). The pulse width of the first pulse PS1 is determined by data T1, DT1, and DT2, and equals: ta + Tc - to. At this time (t = t), the solenoid valve 7 is still in an open state so that the level of signal S is "H". Therefore, the switch 25 is switched over to the state shown by the solid line (Figure 3D).

As a result, the first pulse PSs is output through the switch 25 and the resulting driving pulse DP is applied to the exciting coil 7a of the solenoid valve 7.

Thus, the valve body 7b starts to move in the right-hand direction in Figure 1 and is seated on the valve seat 7d at t = t2. At this time, the solenoid valve 7 assumes a completely closed state and supply of the pressurized fuel starts. As can be understood, the time period from t1 tot2 is the delay time to for the closing of the solenoid valve 7 in this case.

When the solenoid valve 7 assumes a completely closed state at t = t2, the switch SW is closed so that the level of the detection signal S changes from "H" to "L" at t = t2 (Figure 3D). When the abovementioned level change of the detection signal S occurs, the second pulse PS2 is generated from the second pulse generating unit 29 and at the same time, the switch control unit 30 is triggered to change the level of the output line 30a from "L" to "H" (Figure 3G). As a result, when the switch SW is closed, the second pulse PS2 is output through the switch 25 instead of the firstpulse PS1 and the driving pulse DP is dependent on the second pulse PS2 aftert = t2.

The pulse width of the second pulse PS2 is determined by the data T1 and DT2 at that time. That is, it is equal to the difference between the time ta, which depends upon the target injection amount calculated by the target injection amount calculating unit 15 at that time, and the time to determined by the second measuring unit 19 on the basis ofthe operation ofthe solenoid valve J one time previously. In addition, since the calculation of the target injection amount is performed every time the driving shaft 8 rotates exactly 10 degrees, even if there is a sudden change in engine speed, a target injection amount corresponding to the actual operational condition of the engine at each instant can be obtained. Also, time to is measured every time fuel is injected. However, it represents the time when the valve body 7b starts to return under the force of the return spring 7i when the exciting coil 7a is deenergized, and is virtually unaffected by the operating condition of the engine. Therefore, the pulse width of the second pulse PS2 represents the necessary driving period of the solenoid valve 7 for obtaining the desired fuel injection amountaccording to the operating condition ofthe engine at each instant with extreme precision.

Afterthe solenoid valve 7 is once completely closed by the first pulse PS1, the solenoid valve 7 is driven for a period corresponding to the pulse width of the second pulse PS2, and both the levels of the second pulse PS2 and the driving pulse DP change from "H" to "L" att = t3. After being de-energized at t = t3, the solenoid valve 7 starts to open after the opening delay period to has lapsed, so that the level ofthe detection signal S changes from "L" to "H" at t = t4 which is a period of to later than t = t3 (Figure 3D). Consequently, the level of the output line 30a also changes from "H" to "L" at t = t4 (Figure 3G), and the switch 25 is switched-over again as shown by the solid line.

During the period ofthe above-mentioned control operation for the solenoid valve 7, the times t0 and to are measured by the first and second measuring units 18 and 19 respectively, and the results of the measured data DT1 and DT2 are used in the next control operation of the solenoid valve.

As can be understood from the above description, the first pulse PS1 is used for closing the solenoid valve 7, and after the solenoid valve 7 has been completely closed by the first pulse PS1, the second pulse PS2 is used in place of the first pulse PS1 as a signal for controlling the closing period of the solenoid valve 7. A desired fuel injection quantity can be obtained as mentioned above since the width of the second pulse PS2 is determined accurately, and also because the solenoid valve 7 can be controlled with the pulse of the second pulse PS2 alone entirely independent of the delay time tc for closing the valve 7 which is dependent to a large extent on the battery voltage. Accordingly, an extremely accurate adjustment of the fuel injection quantity can be realized.

Furthermore, according to the construction described above, the width ofthe first pulse PS1 need only be an appropriate value slightly longer than the time tc. However, according to the construction of the embodiment shown in Figure 1, even if the second pulse generating unit 29 and or the pulse width decision unit 28 malfunctions, the control of the solenoid valve 7 can be performed with comparatively high accuracy by the first pulse PS1 so that the construction has the advantage of greater reliability. Also, a device with the same function as that of the electronically controlled section shown in Figure 1 for controlling the opening/closing operation ofthe solenoid valve 7 can be realized by the use of a microcomputer in which a predetermined control program is executed and these types of control devices are also contained within the scope of the present invention.

Claims

1. Afuel injection apparatus which includes a fuel injection pump having a solenoid valve located between a high pressure chamber and a lower pressure portion of said fuel injection pump so that the high pressure chamber can be communicated with the lower pressure portion and is constructed to perform the control of injection of fuel to be supplied to an associated internal combustion engine by means of the opening/closing control of said solenoid valve, said apparatus comprising:: a calculating means for calculating a target fuel quantity in accordance with the operating condition of said internal combustion engine and for outputting target data relating to the target fuel quantity; means for producing a timing signal relating to a desired timing ofthe beginning of fuel injection; a first means responsive to the timing signal for producing a first pulse signal for changing over the condition of said solenoid valve to enable a pressurizing operation of fuel in the high pressure chamber; a signal generating means for generating a detection signal indicating the time said solenoid valve is changed over in response to said first pulse signal to a condition in which it is possible for fuel to be pressurized in the high pressure chamber;; a second means responsive to said detection signal and said target data for generating a second pulse signal with a pulse width corresponding to a driving period of said solenoid valve required for obtaining the target fuel quantity when the condition of said solenoid valve is actually changed over into a required condition; and a third means responsive to said first pulse signal, said second pulse signal and said detection signal for outputting a signal for changing over the condition of said solenoid valve to the required condition in accordance with said first pulse signal and for thereafter maintaining the required condition for a period relating to the pulse width of said second pulse signal.

2. An apparatus as claimed in Claim 1 wherein said target data is time data indicating an operating period of said solenoid valve required for obtaining said target fuel quantity.

3. An apparatus as claimed in Claim 2 wherein said first means has a correcting means for correcting said time data by taking into account the response characteristic of said solenoid valve and a first pulse generating means responsive to said timing signal for generating as said first pulse signal a pulse signal with a pulse width determined in response to the output from said correcting means.

4. An apparatus as claimed in Claim 3 wherein said apparatus further comprises a first measuring means responsive to said first pulse signal and said detection signal for measuring a closing delay time of said solenoid valve, and data relating to said closing delay time is applied as correcting data to said correcting means.

5. An apparatus as claimed in Claim 1 wherein said second means has a second measuring means for measuring an opening delay time of said solenoid valve, means responsive to said target data and the output from said second measuring means for calculating a driving period of said solenoid valve necessary for injecting fuel in precisely the amount of said target fuel quantity, and a second pulse generating means responsive to a signal indicating the calculated driving period for generating said second pulse signal at the time ofthe output of said detection signal.

6. An apparatus as claimed in Claim 5 wherein said second pulse generating means is a monostable multivibrator circuit to which said detection signal is applied as a trigger signal and the width of -the output pulse ofthe mono-stable multivibrator circuit is determined in response to the signal indicating the calculated driving period.

7. An apparatus as claimed in Claim 5 wherein said second measuring means is responsive to said detection signal and the output of said third means and measures a time from the generation ofthe output of said third means to the generation of said detection signal.

8. An apparatus as claimed in Claim 1 wherein said third means has a first switching means for selectively deriving either said first or second pulse signal, and a switch control means responsive to -said detection signal for controlling the switching operation of said first switching means, whereby said first switching means is controlled by said switch control means in such a way that said solenoid valve is driven by said second-pulse signal after the condition of said solenoid valve has been switched over into the required condition by said first pulse signal.

9. An apparatus as claimed in Claim 1 wherein said first means generates as said first pulse signal a pulse signal with a pulse width sufficient for completely closing said solenoid valve.

10. An apparatus as claimed in Claim 1 wherein said first means has a first pulse generating means for generating said first pulse signal in response to said timing-signal and the pulse width of said first pulse signal is determined in relation to said target fuel quantity.

11. -An apparatus as claimed in Claim 5 wherein said target data is time data indicating an operating period of said solenoid valve required for obtaining said target fuel quantity.

12. An apparatus as claimed in Claim 11 wherein said first means has a correcting means for correcting said time data by taking into account the response characteristic of said solenoid valve and a first pulse generating means responsive to said timing signal for generating as said first pulse signal a pulse signal with a pulse width determined in response to the outputfrom said correcting means.

13. An apparatus as claimed in Claim 12 wherein said apparatus further comprises means responsive to said first pulse signal and said detection signal for measuring a closing delay time of said solenoid valve, and data relating to said closing delay time and said opening delay time is applied as correcting data to said correcting means.

14. An apparatus as claimed in Claim 1 wherein said calculating means has a means for calculating the target fuel quantity according to the operating condition of said internal combustion engine, and a means for converting the calculated result showing the target fuel quantity into time data showing a driving period of said solenoid valve required for obtaining the target fuel quantity.

15. An apparatus as claimed in Claim 1 wherein said signal generating means includes a second switching means which is formed by a valve body and a valve seat of said solenoid valve.

16. Fuel injection apparatus substantially as described herein with reference to, and as shown in, the accompanying drawings.

17. An engine provided with fuel injection apparatus in accordance with any one ofthe preceding claims.