Field of Application
[0001] The present invention relates to an electronic device architecture for automatically
determining the operating phase of an internal combustion motor or engine.
[0002] In particular, but not limited to, the invention relates to a device of the above-referred
type applied on a direct injection four-stroke motor with automatic determination
of the driving shaft angular position and od the motor operating phase, but the following
description covering this field of application is for convenience of explanation only.
Prior Art
[0003] As is well known in this technical field, the use of electronic units for managing
the injection in modern automotive motors is now common practice. An example of this
is provided by the European Patent Application 01830645.6 to the same Applicant.
[0004] Their use has become necessary to keep certain motor parameters under control so
as to bring the motor emissions within the close limits set by law in many of the
industrialized countries.
[0005] In order to comply with such restrictive law, the leading automotive companies are
increasing the production of direct injection motors so as to decrease pollutants
released in the environment, as well as to improve the performance of the motors.
However, these motors require a more complex and sophisticated control system.
[0006] Recently introduced multiple-injection systems, wherein the parameters to be controlled
are characterized by more pressing specifications of time, make the use of a certain
number of different types of sensors, whose signals are always processed by current
control units, a necessity.
[0007] Thus, these units, commonly known as ECUs (Electronic Control Units), are asked to
provide control functions of increasing complexity.
[0008] In the automotive industry field it is common practice to use ECUs equipped with
a TPU (Time Processor Unit) type of co-processor which is structured to process signals
issuing from a sensor of a driving shaft phonic wheel and from a sensor of a camshaft
phonic wheel, all this with the aim of determining the angular position of the driving
shaft and the operating phase of the motor.
[0009] A lot of parameters must be taken into consideration to best carry out the injection
process under the control of an ECU or a TPU. This implies an enormous computational
load both for the the ECU and for the TPU.
[0010] In fact, both these units have to manage a large number of signals having different
priority levels. In all cases, these signals have to be managed by software routine
activated by interrupt signals, as regards the ECU, and by the occurrence of certain
events, as regards the TPU.
[0011] In any case, a discrepancy is bound to exist between an ideal time for the injection
and the real time when the injection is actually carried out. This results in incorrect
combustion generating a larger amount of pollutants than intended.
[0012] The underlying technical problem of this invention is to provide an electronic device
for automatically determining the operating phase of an motor, which device should
have appropriate structural and functional features so as to enable automatic computation
of such operating phase by directly analysing the signal from the camshaft phonic
wheel.
Summary of the Invention
[0013] The solution idea on which the invention is based is one of providing a hardware
module which can be used as a peripheral unit to the ECU, so that the computing load
can be reduced. This hardware module has the task of calculating the operating phase
of the motor, by analysing the signal from a phonic wheel sensor of a motor camshaft.
[0014] Briefly, the solution idea of the invention is that of releasing the ECU from continually
monitoring the signal from the phonic wheel of the camshaft, so as to lighten the
computing load on the ECU and enable the processing of signals that issue from a plurality
of phonic wheels most commonly employed in the automotive field. This allows the ECU
to serve a number of different motors.
[0015] On the basis of this solution idea, the technical problem is solved by an electronic
device for automatically determining the operating phase of an internal combustion
motor as previously indicated, and as defined in the characterizing part of Claim
1.
[0016] The features and advantages of the device according to the invention should become
apparent from the following description of an embodiment thereof, given by way of
non-limitative example with reference to the accompanying drawings.
Brief Description of the Drawings
[0017]
Figure 1 shows schematically an endothermic injection motor associated with an electronic
device for determining the motor operating phase, according to the invention.
Figure 2 is a schematic detail view of the device according to the invention.
Figure 3 shows schematically a digital signal issuing from a phonic wheel associated
with the motor camshaft linked to the digital signal issuing from a phonic wheel associated
with the driving shaft.
Figure 4 is a diagram of a state machine illustrative of the operation of the device
of Figure 2.
Figures 5 and 6 show, on their relevant diagrams with a common time base, a series
of digital signals generated by the device of Figure 2, indicating the operating phase
of the motor in connection with the camshaft phonic wheel signal and the driving shaft
phonic wheel signal.
Detailed Description
[0018] With reference to the drawings, the architecture of an electronic device embodying
the invention is globally shown with 1 in schematic form. This electronic device is
useful to determine the operating phase of an engine or motor 2, specifically but
not limited to, a direct-injection four-stroke cycle motor with automatic determination
of the driving shaft angular position and of the operating phase. The motor 2 comprises
a driving shaft 3 in combination with a phonic wheel 9, and a camshaft 4 combined
with a phonic wheel 7.
[0019] The device 1 is associated with an ECU, not shown because of the same kind as ECUs
that are conventionally used in automotive applications for controlling this type
of motor ignition and/or injection. The device 1 is represented in Figure 1 by the
block "Camshaft Manager".
[0020] The device 1 is primarily aimed at releasing the ECU from monitoring the motor operating
phase.
[0021] The device 1 has the task of processing electric signals indicating the motor operating
phases. The device 1 is input a signal from a sensor 8 of a phonic wheel 7 made rotatively
rigid with a camshaft 1 of the motor 2.
[0022] The operating phases of a four-stroke are characterized by the movement of the piston
in the cylinder, which is managed by the driving shaft 3, and by the position of the
valves, which are managed by the camshaft 4. The piston moves toward the motor both
with all the valves closed (compression phase or stroke) and with the exhaust valve
open (exhaust phase). The opposite movement of the piston takes place either with
all the valves closed (combustion/expansion phase or power stroke) or with the intake
valve open (intake phase). Within one turn of the driving shaft, the piston completes
both one movement toward the head both the opposite, because its connection to the
driving shaft is established by a connecting rod. At the same time, the camshaft completes
a half turn to manage the valves as appropriate.
[0023] Thus, the rotation ratio between the camshaft and the driving shaft is 1:2. The timing
period for the injection to be actuated is between the compression and combustion/expansion
phases, and corresponds to one driving shaft revolution. In order to identify this
period, the camshaft 4 is provided with a phonic wheel 7 having a predetermined number
of teeth allocated on the circumference of the wheel 7. Since the teeth have no standard
distribution, the device 1 can be programmed by storing the particular profile of
the camshaft phonic wheel 4.
[0024] This signal is input to the device 1 along with a signal indicating the driving shaft
angular position. From the elaboration of this signal, the "Camshaft Manager" device
1 generates a phase signal suitable for each phonic wheel 7 rotation.
[0025] Briefly, the invention provides a hardware module which is input both a signal from
a sensor 8 of the phonic wheel 7 of the camshaft 4 and a signal indicating the driving
shaft angular position, and outputs a series of signals from which the operating phase
of the motor can be obtained, given a reference point.
[0026] The device 1 may also be located next to controllers of units arranged on variable
timing motors, since the modules inside the device can be programmed by inserting
the desired timing variation between the camshaft signal and the driving shaft angular
position signal.
[0027] A basic diagram in Figure 1 illustrates how the invention is applied.
Figure 3 shows the signal generated by the sensor of the driving shaft phonic wheel
compared with the signal from the camshaft phonic wheel. It can be seen in Figure
3 how the profile of the cam signal changes for two successive rotations of the driving
shaft.
[0028] The main function of the "Camshaft Manager" device 1 is to recognize the motor operating
phase by analysing the phonic wheel signal relating to the driving shaft angular rotation.
[0029] The "Camshaft Manager" device 1 comprises three modules 5, 6 and 10, also called
"dec_camma", "cams_shaft" and "pend_camma", whose interconnections are shown in Figure
2.
[0030] The "dec_camma" module 5 performs the task of providing a standard interface toward
the controller of the ECU such that the controller itself can manage the "Camshaft
Manager" device 1. Such a management is actuated by properly forcing the value of
a set of internal registers of the "dec_camma" module 5.
[0031] The values of said registers represent the configuration parameters of the second
"cams_shaft" module 6, forming the heart of the whole system. While normal operating
phase, this module 6 forces the values of a second set of registers inside the first
"dec_cam" module 5, from which the internal state and the results of the second "cams_shaft"
module 6 can be found.
[0032] A general diagram of the hardware architecture of the device 1 is shown in Figure
2.
[0033] Table 1 below shows the I/O input and output signals of the device 1.
Table 1:
Signals |
Description |
Input |
|
Control_bus |
Standard communication interface. |
Address_bus |
|
Data_bus (I/O) |
Data_bus is bidirectional. |
cam_signalSignal |
generated by the circuit of the camshaft sensor. |
lock_f |
Indicates that the driving shaft phonic wheel reference is found. |
n_tooth_holes |
Total number of teeth and holes of the driving shaft phonic wheel. |
tooth_num |
Tooth counter for the crankshaft phonic wheel. |
Output |
|
lock_cam |
Indicates that the motor operating phase is found. |
cam_phase |
Indicates the motor operating phase. |
rec_out |
Desired camshaft profile. |
teeth_cnt |
Indicates the driving shaft angular position after one rotation of the camshaft. |
interrupt_cam |
Interrupt signal. |
[0034] The set of signals
lock_cam, cam_phase and
rec_out allows, whenever the motor operating phase to be found in connection with the driving
shaft position, denoted
tooth_num. The signal
teeth_cnt is generated to indicate the driving shaft angular position in connection with one
complete rotation of the camshaft; like
tooth_num, it is a counter of the teeth of the driving shaft phonic wheel, except that it is
reset every two driving shaft rotations.
[0035] The third "pend_camma" module 10 functions to generate an interrupt toward the controller
of the injection unit of the motor, once the error signals generated by "cams-shaft"
are input. Concurrently with the interrupt being generated, the relevant internal
register of "dec_camma" is set, and from this the type of error generated by "cams_shaft"
can be found.
[0036] The whole architecture 1 is structurally independent, and can be formed as an integrated
circuit on a supporting board and standard bus interconnection. The motor ECU may
also find place on this board.
[0037] Of course, there is no reason for the modules 5, 6 and 10, the device 1, and the
ECU not to be formed in a common-shared integrated circuit of the system-on-chip variety,
still retaining its operational independence.
[0038] Table 2 below shows the registers provided in the first "dec_camma" module 5, which
can be read and/or written by means of the standard interface:
Table 2
Register |
Description |
Output to "cams_shaft" |
|
start |
Starts the state machine implemented in "cams_shaft" |
stop |
Stops the state machine implemented in "cams_shaft" and brings it back to its initial
state ready to start again. |
mem_cam_changes1 |
Table of size1 items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur on the cam signal during the driving shaft rotation relevant to
phase zero. |
profile 1 |
Indicates the expected value of the cam profile stored in mem_cam_changes1. |
size 1 |
Indicates the number of items stored in the mem_cam_changes1 and profile1 tables. |
mem_cam_changes2 |
Table of size1 items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur on the cam signal during the driving shaft rotation relevant to
phase one. |
profile2 |
Indicates the expected value of the cam profile stored in mem_cam_changes2. |
size2 |
Indicates the number of items stored in the mem_cam_changes2 and profile2 tables. |
mem_cam_r |
Table of sizer items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur for the reconstructed cam signal. |
profiler |
Indicates the expected value of the cam profile stored in mem_cam_r. |
sizer |
Indicates the number of elements stored in the mem_cam_r and profilerl tables. |
delta |
Indicates the width of the interval around the timing moment when the system is expecting
a tooth of the camshaft phonic wheel. |
offset_out |
Indicates the extent that the cam signal has to be shifted with respect to the driving
shaft phonic wheel signal. |
a_ns |
Indicates whether the shift has to occur in the forward or the backward direction. |
cfg_phase |
Indicates if the teeth counter of the driving shaft phonic wheel is to be shifted. |
Output to "pend_camma" |
|
mask_inter |
Mask of the interrupts. |
Input from "cams_shaft" |
|
error_at |
Indicates the number of the tooth where the last error occurred. |
teeth_cnt |
Indicates the driving shaft angular position as phonic wheel teeth counter from 1
to 2* (n_tooth_holes). |
cam_phase |
Indicates the motor phase. |
lock_cam |
Indicates that the motor operating phase is found. |
stato_out |
Indicates the current state of the "cams_shaft" state machine. |
rec_out |
Desired camshaft profile. |
Input from "pend_cams" |
|
pending |
Indicates the type of error ocurred. |
[0039] The second "cams_shaft" module 6 functions to find the motor operating phase, and
to signal it properly in connection with the driving shaft 3 angular position. The
phase is found by monitoring the signal from the camshaft sensor 8 (
cam_signal) and the signal indicating the driving shaft angular position (
tooth_num).
[0040] An example of the camshaft signal linked to the driving shaft signal is given in
Figure 3. The signal
fonica_signal is the signal generated by the sensor of the driving shaft phonic wheel. In the example
of Figure 3, the driving shaft phonic wheel 9 has ten teeth and two holes. The distribution
of the teeth of the phonic wheel 7 of the camshaft 4 generates a different number
of pulses for the two driving shaft rotations relating to the rotation of the camshaft.
[0041] The third "pend_camma" module 10 functions to generate an interrupt signal toward
the controller of the ECU.
[0042] Briefly, the third "pend_inter" module 10 functions to generate an interrupt signal
toward the controller of the ECU when a signal is input to the "dec_camma" module
5 which indicates the type of error ocurred. The module 10 in turn generates a signal
for module 5 to set properly the "pending" register, from whose reading the ECU controller
then identifies the type of error so as to decide the action to be taken accordingly.
[0043] Let us now see the operation of the "cams_shaft" module 6 in greater detail.
[0044] The input "cams_shaft" signals are those shown in Table 2 under
'Output toward
"cams_shaft"' section, plus
camsignal, lock_f signals, and
tooth_num signals among the input signals to the "Camshaft Manager" device 1. The output signals
are those shown in Table 2 under
'Input from
"cams_shaft"' section, plus the
alert signal indicating the type of error likely to occur.
[0045] Shown in Figure 4 is the state machine 11 describing the behaviour of the "cams_shaft"
module 6.
[0046] The initial state of the state machine 11 is called "idle", and is attained when
starting and/or resetting the system. By activating the
start signal, the state machine enters the "waiting x lock" state (transition T_1), and
awaits the activation of the
lock_f signal, indicating that the
tooth_num signal is supplying the right driving shaft angular position values.
[0047] As the
lock_f signal is activated, the state machine enters the "check_cm" state (transition T_2),
where the motor operating phase is found.
[0048] This is done by simultaneously analysing the
mem_cam_changes1-profile1 and
mem_cam_chanes2 - profile2 tables according to the value of the
tooth_num signal at each instant. By way of example, the above tables are defined as follows:
Table 3
Phase 0 |
Phase 1 |
mem_cam_changes1 |
profile 1 |
mem-cam_changes2 |
profile2 |
2 |
1 |
14 |
1 |
3 |
0 |
15 |
0 |
|
|
16 |
1 |
|
|
17 |
0 |
[0049] The table for Phase 0 will contain the transitions of the
cam_signal signal during the first driving shaft rotation, and the table for Phase 1 will contain
the transitions of the
cam_signal signal during the second driving shaft rotation.
[0050] The values of the columns indicated as
mem_cam_changes1 and
mem_cam_changes2 should be entered in ascending order. The phonic wheel of the driving shaft 3 considered
in the example of Figure 1 has twelve teeth (two of which are missing to mark the
reference). As is known, for each revolution of the camshaft 4 this wheel makes two,
so that twelve should be subtracted from the number indicated in mem_cam_change2 in
order to identify the correct tooth, given that the
tooth_num signal will indicate numbers from one to twelve.
[0051] Two pointers always indicates the item that must be examined in each table according
to the current value of the
tooth_num signal. From the transition to the "check_cm" state, the two pointers, indicating
the first item in each table, are updated in such a way that they point to the first
item that contains a tooth number larger than or equal to that being indicated by
the
tooth_num signal.
[0052] At each variation in the
tooth_num signal on both tables a in parallel it is controlled that the item pointed to by
the value of the current pointer contains the value indicated by
tooth_num. If it does, it is further checked that the item pointed to by the other pointer does
not contain the same tooth number value (added to the total number of teeth and holes),
or, if so, that it does not contain the same transition value.
[0053] If the above condition is verified, the state machine 11 enters the "locked" state
(transition T_3), otherwise the "check_cm" state is maintained until the condition
is met. In the "locked" state, it is continually checked that the transitions of the
cam_signal signal follow one another correctly and at the time points stored in the tables.
The process is continued from the table that has caused the transition toward the
"locked" state from the "check_cm" state, alternately between the two tables to track
the stored profile.
[0054] In this state, a filtering process of sort may also be carried out on the
cam_signal signal, by using the
delta signal, which indicates the width of an interval around the tooth number where the
transition is expected. The transition toward the "diff" state (transition T_4) occurs
when, inside the time window being examined, the
cam_signal signal does not track the profile stored in the tables.
[0055] In this case, the value of
tooth_num at which the error has occurred is indicated. In the "diff" state it is indicated
thatthat the phase can no longer be tracked properly, and that the state machine goes
back to the "idle" state (transition T_5). During the stay in the "locked" state,
the motor phase is indicated by the
cam_phase signal, as shown in Figure 5.
[0056] Another feature of the "cams_shaft" module is that a camshaft signal can be obtained
from the
rec_out output signal, with the arbitrary profile stored in the
profiler and the
mem_cams_r tables, in relation to the
tooth_num signal. An example is given in the following Table 4, where the signal denoted
rec_out has the herebelow profile:
Table 4
mem_cam_r |
profiler |
6 |
1 |
7 |
0 |
9 |
1 |
10 |
0 |
13 |
1 |
14 |
0 |
19 |
1 |
20 |
0 |
[0057] Thanks to the features previously described, the device 1 can be applied to any motor
type equipped with a camshaft phonic wheel, and can be adapted for any type of phonic
wheels employed in the automotive industry.
[0058] All this is thank you to the extensive configurability of the parameters of modules
5, 6 and 10 which make the device of this invention the more flexible and re-usable
in different applications as possible.
1. An electronic device architecture for determining the operating phase of an internal
combustion motor (2), of the type structured to cooperate with an electronic motor
control unit (ECU) and inputting a signal issued from a sensor (8) of a phonic wheel
(7) associated with the motor (2) camshaft (4);
characterized in that it comprises:
a first I/O interface module (5) incorporating a plurality of registers and receiving
signals from said motor control unit (ECU);
a second module (6) connected bidirectionally to the first module (5) and inputting
the signal issued from said sensor (8) to identify a camshaft (4) reference and to
supply the operating phase of the motor;
a third module (10) adapted to issue an interrupt signal toward said unit (ECU) according
to an error signal incoming from said second module (6).
2. A device according to Claim 1, characterized in that the registers of said first module (5) can be accessed both while reading and writing
from said unit (ECU) via a standard interface.
3. A device according to Claim 1, characterized in that the search for the reference and the following calculation of the camshaft position
(4) are carried out in said second module (6) by continually monitoring the signal
(cam_signal) from the sensor (8) of the camshaft phonic wheel (7).
4. A device according to Claim 1, characterized in that a second set of registers, inside the first module (5), contain data about the internal
state and the results of the second module (6).
5. A device according to Claim 1, characterized in that once an interrupt signal is generated, a relevant internal register of the first
module (5) is also updated, from which the type of error caused by the second module
(6) can be found.
6. A device according to Claim 1,
characterized in that the registers included in said first module (5) are:
start |
Starts the state machine implemented in "cams_shaft" |
Stop |
Stops the state machine implemented in "cams_shaft" and brings it back to its initial
state ready to start again. |
mem_cam_changes1 |
Table of size1 items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur on the cam signal during the driving shaft rotation corresponding
to phase zero. |
profile 1 |
Indicates the expected value of the cam profile stored in mem_cam_changes1. |
size 1 |
Indicates the number of items stored in the mem_cam_changes1 and profile1 tables. |
mem_cam_changes2 |
Table of size1 items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur on the cam signal during the driving shaft rotation corresponding
to phase one. |
profile2 |
Indicates the expected value of the cam profile stored in mem_cam_changes2. |
size2 |
Indicates the number of items stored in the mem_cam_changes2 and profile2 tables. |
mem_cam_r |
Table of sizer items, containing the number-of-tooth values of the driving shaft phonic wheel where
transitions occur for the reconstructed cam signal. |
Profiler |
Indicates the expected value of the cam profile stored in mem_cam_r. |
Sizer |
Indicates the number of items stored in the mem_cam_r and profiler1 tables. |
Delta |
Indicates the width of the interval around the time point when the system is expecting
a tooth of the camshaft phonic wheel. |
offset_out |
Indicates the extent that the cam signal has to be shifted from the driving shaft
phonic wheel signal. |
a_ns |
Indicates whether the shift has to occur in the forward or the backward direction. |
cfg_phase |
Indicates if the teeth counter of the driving shaft phonic wheel has to be shifted. |
7. A device according to Claim 6,
characterized in that the second set of registers of said first module is updated by said second module
(6) are the following:
error_at |
Indicates the number of the tooth where the last error occurred. |
teeth_cnt |
Indicates the driving shaft angular position as phonic wheel teeth counter from 1
to 2* (n_tooth_holes). |
cam_phase |
Indicates the motor phase. |
lock_cam |
Indicates that the motor operating phase is found. |
stato_out |
Indicates the current state of the "cams_shaft" state machine. |
rec_out |
Desired camshaft profile. |
8. A device according to Claim 1, characterized in that said second module (5) constantly checks the pulses of the signal (cam_signal) from
said sensor (8), and it evolves according to a state machine (11) on the basis of
a table correlating the profile of a driving shaft (3) phonic wheel (9) with the camshaft
phonic wheel (7).
9. A device according to Claim 8,
characterized in that the format of said correlation table is, according to the example of Figure 3, the
following:
Phase 0 |
Phase 1 |
mem_cam_changes1 |
profile 1 |
mem-cam_changes2 |
profile2 |
2 |
1 |
14 |
1 |
3 |
0 |
15 |
0 |
|
|
16 |
1 |
|
|
17 |
0 |
and includes a firs table for Phase 0, containing the transitions of said signal
(cam_signal) during the first rotation of the driving shaft (3), and a table for Phase
1 containing the transitions of the signal (cam_signal) during the second rotation
of the driving shaft (3).