Control system for a fuel pump

A control system for a fuel pump, particularly for a solenoid-valve-controlled fuel pump in the case of a self-ignitable internal-combustion engine, in which at least one pulse transmitter is mounted on the crankshaft and/or on the camshaft. The generated pulse sequences include at least several reference pulses for establishing the beginning of fuel injection, as well as speed pulses for detecting the average and the instantaneous rotational speeds. A trial activation takes place to detect into which cylinder the fuel must be injected. Based on the reaction of the fuel injection system and/or of the internal-combustion engine, it is detected whether fuel was injected into the proper cylinder.

FIELD OF THE INVENTION 
The present invention relates to a control system for a fuel pump, and in 
particular for a solenoid-valve-controlled fuel pump for an 
internal-combustion engine. 
BACKGROUND INFORMATION 
A control system for a fuel pump for a diesel gasoline engine is described 
in German Published Patent Application No. 40 21 886. Solenoid valves 
control the supply of fuel. Pulse wheels are located on the crankshaft 
and/or on the camshaft to precisely control the fuel injection quantity 
and the start of fuel injection. Each of these pulse wheels emits a 
sequence of different pulses. A reference pulse mark, which establishes 
the beginning of fuel injection, is provided for each injection process. 
Furthermore, speed pulses are provided for determining the average and the 
instantaneous rotational speed. A synchronization pulse emitted by a pulse 
wheel on the camshaft serves to assign and inject fuel to the appropriate 
cylinder. Because this pulse wheel also emits speed pulses for determining 
the instantaneous rotational speed, the mark which emits the 
synchronization pulse can result in inaccuracies in determining rotational 
speed. 
An object of the present invention is to obtain the fastest and most 
precise synchronization of the injection process, without thereby 
affecting the remaining measuring signals. Synchronization should still be 
possible when various sensor signals are not available. 
SUMMARY OF THE INVENTION 
The present invention is directed to a control system for a fuel pump for 
an internal-combustion engine of a vehicle. The control system includes a 
pulse transmitter mounted on the crankshaft or camshaft of the vehicle for 
generating pulses used to detect rotational speed. The pulses are received 
by a controlling device which determines the quantity of fuel to be 
injected into the cylinders based on the pulses. The control system also 
includes means for activating the controlling device to inject fuel into a 
particular cylinder of the engine and to synchronize fuel injection, as 
well as means for detecting whether fuel was injected into the proper 
cylinder based upon the reaction of the engine to the injection of fuel. 
Advantages of the control system according to the present invention include 
that no additional transmitter is required for the synchronization process 
and that the synchronization process takes place very quickly. 
Furthermore, errors occurring in detecting rotational speed are minimized 
because of the synchronous pulse. 
The present invention is also directed to a method of the operation of the 
control system.

DETAILED DESCRIPTION 
The system according to the present invention shall be described in 
conjunction with a diesel or gasoline engine. However, the present 
invention may also be applied to other internal-combustion engines in 
which fuel injection is controlled, or regulated. 
Referring to FIG. 1, a block diagram of a system according to the present 
invention is shown. A control unit 105 is connected to a final controlling 
device 110, and, in particular, a solenoid valve 110. The solenoid valve 
110 is located on a fuel pump 120. Depending upon the position of the 
solenoid valve 110, the fuel pump 120 injects fuel into the 
internal-combustion engine 100. In the system shown in FIG. 1, each 
cylinder of the internal-combustion engine 100 has a separate fuel pump 
120 and solenoid valve 110. It is also possible, however, for the same 
fuel pump 120 and solenoid valve 110 to alternately inject fuel into the 
individual cylinders. This applies particularly to 
solenoid-valve-controlled distributor pumps. 
The control unit 105 receives signals from a pulse transmitter 130 mounted 
on the crankshaft and from a pulse transmitter 140 mounted on the 
camshaft. The pulse transmitters 130 and 140 are each comprised of a pulse 
wheel 132, 142 on the respective shafts and of a sensor together with an 
evaluation circuit 134, 144, respectively, which emits corresponding 
pulses. The control unit 105 also receives signals from additional sensors 
150, which may indicate the position of the gas pedal, temperature values, 
pressure values, and/or other driving conditions. Based upon these 
signals, the control unit 105 calculates the trigger pulses I for the 
solenoid valve 110. 
Preferably, the number of teeth on the pulse wheel on the crankshaft 
corresponds to the number of cylinders of the internal-combustion engine. 
There is also a synchronization mark S on pulse wheel 132. Since the 
camshaft rotates twice for every motor revolution, with every revolution 
of the motor, the pulse transmitter generates a reference pulse R and a 
speed pulse N, as well as two synchronization pulses S, for each cylinder. 
The speed and reference pulses have the same spacing in each case. 
On the pulse wheel located on the camshaft, marks NW each generate two 
pulses per cylinder. Two such pulses define a rotational-speed measuring 
angle NM and are used to acquire the instantaneous rotational speed. Two 
rotational-speed measuring marks NW1, NW2, NW3 and NW4 are provided for 
each cylinder. 
In control systems of the prior art, a cylinder counter is provided which 
continuously counts between the values 1 and N, where N indicates the 
number of cylinders of the internal-combustion engine. Fuel is injected 
into the appropriate cylinder dependent upon the counter content. For 
example, if the cylinder counter contains a 3, then cylinder 3 is the next 
to be injected. This cylinder counter stipulates the firing order. When 
the internal-combustion engine is started, synchronization must take 
place. This means that the counter must be initialized with the correct 
value. How this synchronization takes place will be delineated in the 
following explanation. 
The system according to the present invention is also applicable, with 
appropriate modifications, to injection systems in which the pulse 
transmitters are mounted in reverse. This means that the pulse transmitter 
that generates the speed pulses is located on the crankshaft, and the 
pulse transmitter that emits the reference pulses is located on the 
camshaft. It is even possible for both pulse transmitters to be placed on 
the same shaft, or for only one pulse transmitter to be provided and for 
one corresponding evaluation circuit to separate the individual pulse 
sequences. 
Referring now to FIG. 2, the various pulses are shown for slightly more 
than one-half of a motor revolution. The rotational-speed measuring angle 
NM for acquiring the instantaneous rotational speed of the 
internal-combustion engine is at FIG. 2a. In each case, two successive 
pulses are designated as rotational-speed measuring angles NM1, NM2, NM3, 
NM4. On the basis of these pulses, the instantaneous rotational speed is 
calculated. This is used to calculate the precise fuel quantity to be 
injected during the next injection. 
Additional pulses are drawn as dotted lines. These pulses are not 
absolutely necessary, but do provide significant improvements in the 
system. The pulses are arranged so that all pulses from the pulse 
transmitter on the camshaft have the same spacing. This is advantageous 
because it considerably simplifies the signal analysis, in that pulses 
having the same spacing can be evaluated more easily and accurately than 
pulses having unequal spacing. 
However, only those pulses which are drawn in thickly are necessary to the 
system according to the present invention. They form the rotational-speed 
measuring angles designated as NM1, NM2, NM3 and NM4. The rotational speed 
which results when there is no injection is drawn as a dotted line in FIG. 
2b. The rotational speed which results when an injection takes place 
following the rotational-speed measuring angle NM2 is plotted as a 
dot-dash line in FIG. 2b. 
The pulses from the crankshaft transmitter are plotted in FIG. 2c. The 
reference pulses R immediately follow the rotational-speed measuring angle 
NM of the corresponding cylinder. A speed pulse N is also drawn in each 
case between two reference pulses R. This speed pulse N serves to acquire 
the average rotational speed of the crankshaft. A synchronization pulse S, 
which is used to synchronize the cylinders, is also drawn. 
Since the crankshaft rotates two revolutions per pump revolution, and the 
camshaft, in comparison, rotates only one revolution per pump revolution, 
two crankshaft revolutions result per camshaft revolution. This is 
indicated by designating the rotational-speed measuring angle NM1 as the 
rotational-speed measuring angle NM3, and the rotational-speed measuring 
angle NM2 as the rotational-speed measuring angle NM4. 
If the control unit 105 detects at this point that the synchronization 
pulse S has appeared, the instantaneous rotational speed needed to 
calculate the injection into the second or fourth cylinder is determined 
from the rotational-speed measuring angle NM2. After the synchronization 
mark appears, the next injection must follow, either into cylinder 2 or 4. 
An injection into cylinder 2 follows. If the pattern indicated by a 
dot-dash line drawn in FIG. 2b results, then this injection was correct. 
If, on the other hand, the pattern indicated by a dotted line results, 
then cylinder 2 was wrong, and the injection should have taken place into 
cylinder 4. 
A flow chart for the operation of the system according to the present 
invention is shown in FIG. 3. The synchronization mark S is detected in a 
first part. Various means are available for the detection. First, the 
synchronization pulse S can be detected in step 301 by means of a logical 
comparison of the pulse spacings. To accomplish this, the spacing between 
the pulses from the pulse transmitter on the crankshaft is evaluated. If 
the spacing between two successive pulses is considerably smaller than the 
spacing between the preceding pulses, then the last pulse is identified as 
the synchronization pulse S. 
Since irregularities in rotational speed also affect the spacing of the 
pulses during acceleration or deceleration, erroneous determinations are 
possible here. On the other hand, in a particularly advantageous 
modification, the number of pulses from the pulse transmitter on the 
crankshaft which appear between two rotational-speed measuring angles is 
evaluated. The number of pulses reveals if a synchronization pulse S 
existed. 
For this purpose, a rotational-speed measuring angle NM is detected in step 
300. After the rotational-speed measuring angle NM is detected, a counter 
Z1 is initially set to zero and then, with each occurrence of a pulse from 
the pulse transmitter on the crankshaft, is incremented by 1 at 305. The 
counter Z1 continues to be incremented until, in step 310, the occurrence 
of a second rotational-speed measuring angle NM is detected. 
In step 320, if it is detected that the counter has the value 2, no 
synchronization pulse S has occurred. This means that the second 
rotational-speed measuring angle detected in step 310 is the speed pulse 
NM3 or NM1, and further that the first or third cylinder must therefore be 
injected next, in step 322. 
On the other hand, in step 320, if it is detected that the counter is not 
equal to 2, step 325 follows. In step 325, if a counter value of 3 is 
recognized, the existence of a synchronization pulse S is detected. Here, 
in the case of the second rotational-speed measuring angle detected in 
step 310, the rotational-speed measuring angles NM2 or NM4 are involved. 
This means that the next injection must take place into the second or 
fourth cylinder, in step 327. In step 325, if it is detected that the 
counter content is not equal to 3, then an error is detected in step 330. 
In this case, this part of the flow chart must be repeated once again. 
In a second part, the injection data, i.e., the start of injection SB and 
the duration of injection SD, are calculated in step 335. The appropriate 
solenoid valve is then activated on a trial basis in step 340. This can 
result in injection into one of the two possible cylinders. It is then 
recognized whether the trial activation was correct. Such a recognition is 
possible because the rotational speed is evaluated. If the rotational 
speed, which is determined in the rotational-speed measuring angle NM3 
after the activation, is considerably greater than the rotational speed 
which is determined with the rotational-speed measuring angle NM2 before 
the activation, then the trial activation was correct. Whether or not the 
activation was correct can be evaluated desirably by analyzing the 
enabling or disabling times TE, TA of the solenoid valve. 
The rotational speed in the rotational-speed measuring angle NM3 is 
determined in step 345, and compared to the preceding rotational-speed 
value in the measuring angle NM2 in step 351. If the rotational speed is 
greater than the preceding one, then fuel injection into cylinder 3 
follows in step 355. If it is smaller, then fuel injection into cylinder 1 
follows in step 352. In the following step 360, subsequent injection takes 
place in each case into the next cylinder. 
concludes the synchronization for a 4-cylinder internal-combustion engine. 
If no increase in rotational speed is detected, then an additional 
injection test must still be performed for a 6-cylinder 
internal-combustion engine. 
It is therefore possible with this method of operation to implement the 
synchronization, at the latest, after one crankshaft revolution, and, on 
the average, even after one-half of a crankshaft revolution. Thus, the 
synchronization takes place within one piston stroke. It is particularly 
advantageous when the switching times for the solenoid valve are evaluated 
in addition to, or instead of, the rotational speed. 
In the case of a pump-nozzle system, the camshaft actuates the pump piston 
directly or indirectly. In the case of a 4-cylinder internal-combustion 
engine, four pump-nozzle units are mounted directly on the internal 
combustion engine. One of the pump-nozzle units at a time delivers fuel 
into the internal-combustion engine. Each pump nozzle contains a delivery 
element. When a flow of fuel begins to be delivered via the delivery 
element, it is also delivered through the corresponding solenoid valve. 
When the solenoid valve is closed, the injection takes place into the 
combustion chamber. The flow of fuel delivered through the open solenoid 
valve into the element chamber and the pressure build-up in the case of a 
closed solenoid valve only take place on the solenoid valve, or on the 
pump-nozzle unit whose element is discharging. This means that the 
camshaft actuates this element, so that pressure is built-up in the 
element chamber. In the case of the remaining three pump-nozzle units, no 
flow of fuel is delivered through the element. 
The enabling and the disabling times of the solenoid valve depend on 
whether fuel is delivered through the solenoid valve or not. Therefore, it 
is possible to detect the cylinder from measurement of the enabling or the 
disabling times. The enabling time is established by means of a BIP 
recognition, and the disabling time by means of a BOP or EIP recognition. 
To clarify these concepts, reference is made to FIGS. 4a and 4b. In FIG. 
4a, the solenoid valve lift MH is plotted as a function of time t. In FIG. 
4b, the trigger pulse I of the solenoid valve is plotted as a function of 
time t. 
BIP marks the start of the injection process. As of this instant, fuel is 
injected into the combustion chamber. BOP denotes the end of the injection 
process. At this instant, the solenoid valve begins to close, i.e., the 
opening cross-section of the solenoid valve is reduced in size. At the 
instant EIP, the solenoid valve is completely closed, and pressure is no 
longer built-up. The result is that injection of fuel into the combination 
chamber completely stops. 
As shown in FIGS. 4a and 4b, there is a time difference between the 
switching pulse I for the solenoid valve and the beginning and the end of 
the injection. The time difference between the beginning of the trigger 
pulse and the beginning of the injection BIP is designated as the enable 
time TE. The time difference between the end of the trigger pulse I and 
the end of the injection EIP is designated as the disable time TA. The 
enable time TE and the disable time TA depend in each case on whether the 
solenoid valve works under load operation, i.e., fuel is being delivered, 
or under no-load operation, i.e., no fuel is being delivered. 
The synchronization, i.e., the allocation of the cylinder counter to the 
cylinder to be injected, takes place as follows. At start-up, the 
individual solenoid valves of the various pump-nozzle units are quickly 
triggered in a cyclical manner, i.e., opening and immediately closing 
again, by cylinder 1 through cylinder N. 
The opening and closing preferably takes place in a time interval of about 
1.5 milliseconds. During the short opening time of the solenoid valve, 
provided that a pump element is in its prestroke, only a quantity of fuel 
that is negligible compared to the beginning quantity is injected. The 
enabling times TE and/or the disabling times TA are determined during the 
trial activation of the solenoid valves. On the basis of the measured 
switching times, it can be established which of the pump-nozzle elements 
is delivering. From this value, the cylinder counter can be started with 
the correct value. 
This process proceeds as depicted in the flow chart of FIG. 5. An 
initialization takes place in step 400. Thus, for example, a counter N is 
set to zero. In step 410, the counter N is incremented by 1. In step 420, 
the Nth solenoid valve is activated. 
The enabling time TE and/or the disabling time TA are then evaluated in 
step 430. Meanwhile, if the realization is that no injection is taking 
place, then the counter N is again incremented by 1 in step 410. However, 
if the realization is that a delivery of fuel follows, then the cylinder 
counter is set to the value of the counter N in step 440. This ends the 
synchronization procedure. 
As a result of this procedure, synchronization is possible for the 
injection test with the first revolution of the motor. Furthermore, the 
advantage of this procedure compared to the process of injecting fuel on a 
trial basis and of evaluating the change in rotational speed is that the 
start-up fuel quantity is not injected incorrectly and, therefore, there 
is no emission of black smoke. The transmitter systems, or the evaluation 
principles applied in pump-nozzle systems, can be used for the cylinder 
synchronization. Therefore, no additional sensors are necessary. 
In the case of a cold start, a faulty interpretation of the measuring 
results is possible due to variable cylinder friction or incomplete 
combustion. Therefore, it is necessary to wait until the synchronization 
has been additionally safeguarded. This is done with the help of a 
temperature threshold, and proceeds as follows. If the temperature lies 
under a specified threshold, then the process is repeated one time after 
the above-described flow chart has been traversed once. The two results 
are compared. In the case of a cold motor, this longer start-up process is 
of no consequence. 
If the goal is to achieve the highest possible reliability of the system to 
protect against failure, then, in addition, the synchronization pulse must 
be detected redundantly. This can be accomplished, for example, by placing 
an additional synchronization mark on the camshaft. This redundancy 
enables operation under emergency conditions, in that even a motor that is 
not running can be started again, so that the motor vehicle can be driven 
to a service station. If no such second transmitter is available, the 
motor can continue to run when the transmitter fails, but a renewed start 
is not possible. 
If individual interference pulses occur, then a monitoring operation must 
follow in which the synchronization pulse detected with the described 
process is compared to the cyclically rotating cylinder counter. With the 
help of a logic circuit, a redundant cylinder counter, and the described 
procedure, individual interference pulses are rendered ineffective. If the 
interference cannot be removed by means of the logic circuit, as long as 
the motor still turns, an emergency program must assure a new 
synchronization, as during start-up. 
A particularly advantageous embodiment of a system according to the present 
invention provides for the mounting of the pulse wheels in reverse. This 
means that a pulse wheel that produces an incremental raster is located on 
the crankshaft. Such a pulse wheel emits a pulse sequence as shown in FIG. 
6a. In the case of a six-cylinder internal-combustion engine, a pulse is 
missing at a spacing of 120 degrees, and therefore a reference pulse R is 
defined. This reference pulse R is usually used to determine the start of 
injection. Furthermore, the top dead center OT of the piston is drawn. The 
direction of rotation of the shaft is indicated by an arrow. 
Located on the camshaft is a transmitter wheel which emits at least one 
synchronization pulse S as well as the speed pulses N. The signal sequence 
generated by this transmitter wheel is shown in FIG. 6b. In the case of a 
six-cylinder internal-combustion engine, the speed pulses occur with a 
spacing of 60 degrees. The synchronization mark S is usually used for 
synchronization. 
It is even possible for both pulse wheels to be placed on the same shaft, 
or for only one pulse wheel be to provided and for a corresponding 
evaluation circuit to separate the individual pulse sequences. In such 
systems, the synchronization usually occurs by evaluating the speed pulses 
N, the synchronization pulse S, and perhaps other signals. In such 
systems, the procedure according to the present invention is particularly 
advantageous under emergency conditions. This type of emergency operation 
is necessary when the pulse transmitter and/or the associated evaluation 
unit, which generate the synchronization pulses or implement the 
synchronization, fail. 
The procedure is particularly suited as an emergency procedure in those 
systems in which the synchronization is performed for the most part on the 
basis of the evaluation of reference pulses and/or synchronization pulses. 
In such systems, the fuel quantity is usually released only when the 
synchronization has taken place. 
The procedure, which is clarified in FIG. 7, serves to maintain emergency 
driving operation when synchronization fails. After the control unit is 
switched on in step 600, a known error detection test is performed in step 
610. 
This test detects if the synchronization can be or has been properly 
implemented. This is not the case, for example, when the sensors and the 
evaluation unit are defective. If it is detected in step 620 that the 
synchronization can be or has been properly implemented, then the normal 
procedure for controlling the internal-combustion engine follows in step 
630. If it is detected, on the other hand, that the synchronization is 
faulty or is not possible, then an emergency synchronization is initiated 
in step 640. The normal control procedure then follows in step 650. 
Such an emergency synchronization can be performed as described in the 
preceding paragraphs, for example. The emergency synchronization is merely 
supposed to ensure that the internal-combustion engine can be started and 
that it is working well-enough to perform at least a limited range of 
functions. Fast synchronization is not required in an emergency operation. 
Moreover, in an emergency operation, unacceptably high exhaust emissions 
are not a concern. Since the requirements for emergency operation are not 
as stringent as those for normal operation, a considerably simpler 
procedure can be applied. 
The procedure is clarified in FIG. 8, in which various sequences for 
activating the solenoid valves are plotted as a function of time. The 
correct firing order ZF of the individual cylinders is also plotted, as an 
example. 
The control unit is switched on at instant T1. The synchronization is 
usually performed between instant T1 and instant T2. If it is detected in 
this time interval that the synchronization cannot be performed, or that 
the synchronization is faulty, the switch-over is made to emergency 
operation. At instant T3, the injection process is started. Instances of 
activation that have been carried out are shown with an X and those that 
have been left out are shown with a dash. The sequence for activating the 
individual solenoid valves MV is shown in FIG. 8a in accordance with a 
correctly implemented synchronization. 
In FIGS. 8b and 8c, the sequence of activation is shown for a faulty 
synchronization or for a failure of the pulse transmitter on the 
camshaft/crankshaft. In the procedure clarified in FIG. 8b, initially only 
the solenoid valve allocated to the first cylinder is activated for each 
ongoing injection operation. 
The activation of the solenoid valve leads only to an injection when the 
pump piston allocated to the first cylinder begins to deliver fuel. 
Therefore, the combustion chamber of the internal-combustion engine is 
injected only when the pump piston allocated to the first cylinder 
delivers fuel. 
An injection follows, at the latest, two revolutions of the crankshaft 
after the error is determined. This leads at instant T4 to a marked 
increase in rotational speed. This increase in rotational speed is 
detected, as already described. It is also particularly advantageous when 
a larger angular range is evaluated as the measuring angle to determine 
the instantaneous rotational speed. The average rotational speed spacing 
between two speed pulses N can also be used to detect the increase in 
rotational speed. 
The synchronization is complete when it is established by evaluating the 
increase in rotational speed that fuel has been injected into the first 
cylinder. The solenoid valves allocated to the remaining cylinders are 
subsequently activated in accordance with the established firing order. An 
injection is skipped 
increase in rotational speed is detected only after a certain time delay. 
Even if synchronization fails, this procedure enables a rapid 
synchronization (maximally after two crankshaft revolutions) by means of 
the synchronization pulse S. 
The sequence for activating the individual solenoid valves is shown in FIG. 
8c as another version of the method according to the present invention. 
The solenoid valves are initially continuously activated in accordance 
with the established firing order. If no synchronization has taken place 
yet, i.e., injection did not begin with the correct cylinder, then no 
marked increase in rotational speed results. After one machine cycle, 
i.e., after all solenoid valves have been activated once (this corresponds 
to two revolutions of the crankshaft), one solenoid valve is skipped and 
is not activated in the next machine cycle. 
In other words, after the first machine cycle, injection does not begin 
with the first but rather with the second solenoid valve. The solenoid 
valves are subsequently activated again in accordance with the established 
firing order. This procedure is repeated, whereby, one after the other, 
another solenoid valve is skipped in each case and is not activated, until 
one solenoid valve is activated synchronization with the delivering 
stroke. This leads to injections and thus at instant T4 to an increase in 
rotational speed. On the basis of the increase in rotational speed, it is 
recognized that the correct solenoid valve was activated. Thus further 
injection can be started based on the above synchronization. 
Since, according to this procedure, an increase in rotational speed occurs 
because all cylinders are injected, the increase is substantially greater 
than in the first version, in which there was only one injection into one 
cylinder. This greater increase in rotational speed can be detected more 
easily and reliably.