Device for controlling the position of an element which controls the fuel-air mixture

The present invention relates to a device for controlling the position of an element of an automobile internal combustion engine which controls the fuel-air mixture, comprising a desired-value transmitter 2 for producing an electric desired-value signal which can be fed to a electronic control unit 14. A setting member 19 for displacing a throttle valve 20 into a position corresponding to the position of the desired-value transmitter 2 can be controlled by the electronic control unit 14. In order to make smooth starting possible, a controller unit 15, by which the control of the setting member 19 is regulated upon the starting, is arranged between the desired-value transmitter 2 and the electronic control unit 14.

The present invention relates to a device for controlling the position of 
an element which controls the fuel-air mixture of an internal combustion 
engine of an automotive vehicle, having a desired-value transmitter for 
producing an electric desired-value signal. The signal is fed to an 
electronic control unit by which a setting member, for displacing the 
element controlling the fuel-air mixture into a position corresponding to 
the signal of the desired-value transmitter, can be controlled. 
In such known arrangements the desired-value transmitter consists of a 
potentiometer which can be adjusted by the driver by means of the gas 
pedal. A corresponding signal is fed to the electronic control unit in 
accordance with the position of the potentiometer. The electronic control 
unit controls an electromotive setting member in such a manner that the 
element which controls the fuel-air mixture, and which may be a throttle 
valve, is brought into a position which corresponds to the position of the 
gas pedal. 
Upon starting, this can have the result that there is a starting jerk of 
the car when a signal corresponding to too high a desired value is fed to 
the electronic control unit and the setting member is adjusted accordingly 
by it. 
The proper determination of the desired value upon starting is, however, 
difficult since the driver can do this only on basis of a sense of feel. 
It is particularly difficult to produce jerk-free starting in the case of 
commercial vehicles which themselves are of substantial weight and in 
addition to which there is also a greatly varying weight of load. 
In this connection, the difficulty is further increased if the starting is 
to take place uphill. 
Substantially smooth starting, however, is necessary if sensitive cargo or 
persons are to be carried. 
The object of the invention therefore is to provide a device of this type 
which permits of smooth starting. 
This object is achieved in accordance with the invention by the provision 
between the desired-value transmitter (2) and the electronic control unit 
(14) of a controller unit (15) by which, upon displacement of the 
desired-value transmitter (2) from its end position corresponding to a 
speed of travel of zero, the change in the value of the desired-value 
signal per unit of time can be limited below a given speed of travel to a 
maximum value. By the development in accordance with the invention, a 
smooth increase of the signal fed to the electronic control unit takes 
place during starting even with a desired value which is set to a high 
value at the gas pedal, thus obtaining a smooth jerk-free start up to a 
speed of travel as from which the control of the setting member can take 
place in traditional manner without producing a jerk. In this way the 
driver can, upon starting, bring the gas pedal into the full-throttle 
position without producing a jerk upon starting. 
The maximum value to which the change in value of the desired-value signal 
per unit of time can be limited is preferably an adjustable, or 
presettable, constant value which is determined in a manner specific to 
each car. 
In one advantageous development of the invention, the change in the value 
of the desired-value signal per unit of time can be limited starting from 
a value which corresponds to the maximum position of the desired-value 
transmitter (2) at which the speed of travel is zero. This means that when 
a high desired value is set, the setting member can immediately pass, 
without limitation of its speed of adjustment, into a position in which 
the vehicle still does not start into motion due to the various 
resistances which must be overcome, such as weight of vehicle, frictional 
loss in transmission, and slippage of tires. Only from this point on, 
above which the vehicle starts to move, is the change in the size of the 
desired-value signal per unit of time limited to the maximum value until 
the specific speed of travel is reached. 
The value, up to which the change in the value of the desired-value signal 
per unit of time can take place without limitation, may be an adjustable, 
or presettable, constant value which is determined in a manner specific to 
the car, in which connection the weight of the car is particularly to be 
taken into consideration. 
This value may, however, also be a variable value which is automatically 
adjustable as a function of the total weight of the vehicle. In this way 
the optimum starting process is obtained automatically under any condition 
of loading of the vehicle. 
The controller unit (15) may have an integrating stage (16) by which the 
change in the size of the desired-value signal per unit of time can be 
limited. 
If the change of the size of the desired-value signal per unit of time is 
to be limited only starting from a given value, then the controller unit 
(15) can furthermore have a limiting stage (17), the output values of the 
integrating stage (16) and of the limiting stage (17) being adapted to be 
fed to an addition stage (18) and the output thereof to the electronic 
control unit (14). This development has the advantage that the starting 
process can take place immediately and it is not necessary to wait until 
the desired value signal which increases with limited rise has reached a 
value at which the car starts to move. 
The speed of the car can be noted by a speed transmitter (7) and be 
converted into an electric speed signal. 
The speed signal can be fed to one input (10) of a speed comparator and a 
signal corresponding to the given speed of travel to a second input (11) 
thereof, the comparator giving off an output signal if the speed signal is 
larger than the given travel speed signal from which the electronic 
control unit again operates in traditional manner. In this connection the 
speed comparator may be a threshold switch (8). Thus, when the given speed 
of travel is reached, a signal is produced by which switching is effected 
from limited to unlimited control of the setting member. The desired-value 
signal can be fed to one input (9) of a desired value comparator and an 
electric constant signal corresponding to the maximum position at which 
the speed of travel is zero to a second input (12) thereof, an output 
signal being given off by the desired-value comparator, when the 
desired-value signal is larger than the constant signal. In this case also 
the desired value comparator can be a threshold switch (3). The desired 
value comparator thus gives off a signal only when the desired-value 
signal entering into it is greater than the constant value present at its 
other input. 
The output of the speed comparator and the output of the desired-value 
comparator can be connected to a switch unit (5) by which a desired-value 
signal of the desired-value transmitter (2) can be fed to the controller 
unit (15) when an output signal of the desired value comparator is present 
and an output signal of the speed comparator is not present. Thus speed 
comparator and desired-value comparator clearly determined the criteria 
under which the controller unit is placed in operation. 
The output of the desired-value comparator can be connected to a second 
switch unit (4) by which the output of the desired-value transmitter (2) 
can be connected to the electronic control unit (14) when no output signal 
from the desired-value comparator is present. In this way the 
desired-value signal is then fed directly to the electronic control device 
when the desired value is smaller than the maximum acceleration value set 
on the desired-value comparator. This is also possible without difficulty 
since no starting jerk can occur with such slight acceleration. 
The output of the speed comparator can be connected to a third switch unit 
(6) by which the output of the desired-value transmitter (2) can be 
connected to the electronic control unit (14) when an output signal of the 
speed comparator is present. As a result the desired-value signal is fed 
directly to the electronic control device when the starting process is at 
an end and the given speed has been exceeded. After the process of 
regulated starting control, traditional control of the acceleration can 
then be effected during normal travel. A regulated starting control in 
accordance with the principles of the known acceleration control is not 
possible since the low speed of travel present during the starting cannot 
be measured in an economically feasible manner.

The device shown in FIG. 1 has a desired-value transmitter 2 which can be 
adjusted by the driver by means of a gas pedal 1 and which is developed as 
a potentiometer. 
The output of the desired-value transmitter 2 is connected with one input 9 
of a threshold value switch 3, with a switch unit 4, with a switch unit 5, 
and with a switch unit 6. 
The output of a speed detector/transmitter 7, which notes the speed of 
travel is connected to one input 10 of a threshold switch 8. 
The second input 11 of the threshold switch 8 is acted on by a constant 
electric magnitude which corresponds to a given speed, while the second 
input 12 of the threshold switch 3 is acted on by a constant electric 
magnitude which corresponds to the maximum position of the desired-value 
transmitter at which the car is not yet in motion and therefore still has 
a zero speed of travel. 
The output of the threshold switch 8 is connected to the switch unit 6 by 
which a connection from the desired value transmitter 2 can be effected 
via a connecting stage 13, to an electronic control unit 14 when a signal 
is given off at the output of the threshold switch 8. 
The output of the threshold switch 3 is connected to the switch unit 4 via 
which a connection can also be made from the desired-value transmitter 2 
to the connecting stage 13 and to the electronic control unit 14. This 
connection is open when no signal is given off by the threshold switch 3. 
Furthermore, the outputs of the two threshold value switches 3 and 8 are 
connected to the switch unit 5. As already stated, the switch unit 5 is 
also connected to the desired-value transmitter 2. 
This switch unit 5 opens the connection from the desired-value transmitter 
2 to a controller unit 15 when a signal is fed here from the threshold 
switch 3 but no signal is present from the threshold switch 8. 
The controller unit 15 has an integrating stage 16 and a limiting stage 17, 
to each of which the connection with the desired-value transmitter 2 
extends. 
The outputs of the integrator stage 16 and the limiting stage 17 are fed to 
an addition stage 18 which is also present in the controller unit 15 and 
the output of which is fed to the electronic control unit 14. 
The electronic control unit 14 thus receives, either the desired-value 
signal given off by the desired-value transmitter 2 directly via the 
connecting stage 13, or a signal prepared by the controller unit 15. 
Depending on the size of these signals, the electronic control unit 14 
controls the setting member 19 for the displacement of a throttle valve 
20. 
The function of the device in accordance with the invention will be 
described below with reference to the graphs shown in FIGS. 2, 3 and 4. 
The displacement between the idle position (0%) and the full-throttle 
position (100%) with respect to time is shown for the desired-value 
transmitter 2 in FIG. 2 and for the setting member 19 in FIG. 3. 
FIG. 4 shows the variation of acceleration a with the speed V during the 
starting process. In this case, the course of the acceleration in 
accordance with the prior art is shown in dashed line and the course of 
acceleration in accordance with the invention in solid line. 
If a high desired value is set on the desired value transmitter 2 upon 
starting, for instance by depressing the gas pedal 1 all the way, then the 
desired value transmitter 2 gives off a desired-value signal of 100%. This 
can be noted in FIG. 2. This desired-value signal is clearly above the 
value x. 
This value x is present as constant signal at the one input of the 
threshold switch 3 and corresponds to the maximum position of the 
desired-value transmitter at which the speed of travel is still zero. 
Since the desired-value signal is greater than this constant signal, an 
output signal is given off by the threshold switch 3 and fed both to the 
switch unit 5 and to the switch unit 4. The forward direction of the 
switch unit 4 is thereby blocked. 
At the same time the speed of travel is still zero so that the speed signal 
fed by the speed transmitter to the threshold switch 8 is less than the 
specific travel speed signal present at the other input of the threshold 
switch 8. This given travel speed signal corresponds to a fixed speed of 
travel below which regulated control and above which normal traditional 
control of the setting member 19 is to take place. This fixed speed of 
travel is designated V.sub.E. 
Since the speed signal is less than V.sub.E, the threshold switch 8 does 
not give off any signal. 
The forward direction of the switch unit 6 is thus blocked. 
Since a signal is present from the threshold switch 3 on the switch unit 5 
but no signal is present from the threshold switch 8, the forward 
direction of the switch unit 5 is opened and the desired-value signal from 
the desired-value transmitter 2 acts on the integrating stage 16 and the 
limiting stage 17 of the controller unit 15. 
This desired-value signal, which is very high due to the full-load position 
of the desired-value transmitter 2, is limited by the limiting stage 17 to 
a value which corresponds to the value x and is conducted to the addition 
stage 18. 
The desired-value signal is so treated by the integration stage 16 that its 
course with respect to time corresponds to the shape of the curve shown in 
FIG. 3 above the value x. 
The signals given off by the limiting stage 17 and the integrating stage 16 
are added in the addition stage 18 and forwarded to the electronic control 
unit 14. 
The addition of these signals is shown in FIG. 3, the vertical ascent of 
the curve up to the value x being formed by the limiting stage 17. This 
value remains constant over the course of time. The values of the 
integrating stage 16 which rise with the passage of time and are added 
thereto lead to the shape of the curve shown. 
If a position of the setting member 19 is reached which corresponds to the 
travel speed V.sub.E set at the threshold switch 8, an output signal is 
given off by the threshold switch 8 to the switch units 5 and 6. 
This has the result that the forward direction of the switch unit 5 is 
blocked and the forward direction of the switch 6 opened. 
In this way the controller unit 15 no longer is acted on, while the 
desired-value signal passes via the switch unit 6 and the connecting stage 
13 directly to the electronic control unit 14. 
The latter can now control the setting member 19 for the displacement of 
the throttle valve 20 in traditional fashion. 
The regulated control of the setting member 19 which has been described 
leads to the curve shown in FIG. 4 which clearly shows that regardless of 
the setting of a high desired value during the starting process the 
acceleration rise is limited to values which assure a smooth starting. 
On the other hand, if the desired value set is smaller at the start of the 
driving than the constant signal fixed by the value x at the threshold 
switch 3, then the threshold switch 3 does not give off any output signal. 
In this way the switch unit 4 is opened for passage and the desired-value 
signal can pass via the connecting stage 13 directly to the electronic 
control unit 14. At the same time the forward directions of the switch 
units 5 and 6 are blocked. 
Upon an increase of the desired value and simultaneous increase in the 
speed below the rate of increase determined by the integration stage 16, 
the value x is exceeded at the threshold switch 3 ad the value V.sub.E at 
the threshold switch 8. This has the result that the forward direction of 
the switch unit 5 continues to be blocked, the forward direction of the 
switch unit 4 is blocked and the forward direction of the switch unit 6 is 
opened. 
The desired-value signal thus passes directly from the desired value 
transmitter 2 via the switch unit 6 and the connecting stage 13 to the 
electronic control unit 14. 
The signal applied by switch unit 5 is a logic type signal. If controller 
unit 15 is acted on by switch unit 5 controller unit 15 creates a variable 
analog voltage which is supplied to the electronic control unit 14. 
The signal applied by connecting stage 13 is also a logic type signal. 
If there is a signal on the output of connecting stage 13 than the control 
unit 14 is supplied by the analog signal which is created by the 
transmitter 2 via a not shown line.