Data acquisition method

Abstract

A method for transmitting the cylinder pressure data of a plurality of cylinder pressure sensors to a central processing unit, characterized by the use of a communication system for isochronous data transmission comprising a data bus, whereby the plurality of cylinder pressure sensors and the central processing unit are connected via the data bus, whereby each of the plurality of cylinder pressure sensors are combined with a data acquisition unit and a data communication unit to form a measurement node, whereby the cylinder pressure data is transmitted from the measurement node to the central processing unit via a time-slot method.

Claims

1. A method for transmitting cylinder pressure data of a plurality of cylinder pressure sensors to a central processing unit, the method comprising: using a communication system for isochronous data transmission comprising connecting the plurality of cylinder pressure sensors and the central processing unit via a data bus; combining each of the plurality of cylinder pressure sensors with a data acquisition unit and a data communication unit to form a measurement node; and transmitting the cylinder pressure data from the measurement node to the central processing unit via a time-slot method, wherein a cycle time of the time-slot method is selected to be smaller than a minimum achievable period of an internal combustion engine corresponding to a maximum speed of the internal combustion engine.

2. The method according to claim 1, wherein the communication system is a wired network.

3. The method according to claim 1, wherein the cycle time of the time-slot method is selected to be at least 50 times smaller than the minimum achievable period of the internal combustion engine corresponding to the maximum speed of the internal combustion engine.

4. The method according to claim 1, wherein evaluation of the cylinder pressure data is staggered in time and cylinder-specific.

5. The method according to claim 1, wherein assignment of data segments of the cylinder pressure data to a respective crank angle range is performed by measuring crank angle at a single measurement node.

6. A communication system for isochronous data transmission comprising: a plurality of cylinders in an internal combustion engine; a plurality of cylinder pressure sensors; a data acquisition unit; a data communication unit; a measurement node formed by combining the plurality of cylinder pressure sensors with the data acquisition unit and the data communication unit; a data bus; and a central processing unit operable to receive cylinder pressure data from the measurement node via a time-slot method, with the central processing unit and the plurality of cylinder pressure sensors connected via the data bus, wherein a cycle time of the time-slot method is selected to be smaller than a minimum achievable period of an internal combustion engine corresponding to a maximum speed of the internal combustion engine.

7. The system of claim 6, wherein the system is a wired network.

8. The system of claim 6, wherein the cylinder pressure data is cylinder specific.

9. The system of claim 6, wherein the system is a single line wired network.

10. The system of claim 6, wherein the system is a time-triggered hard real-time network.

11. The system of claim 6, wherein the measurement node and the central processing unit are each equipped with clocks.

12. The system of claim 6, further comprising a ring gear connected to a crankshaft of the internal combustion engine, with a pick-up arranged on the ring gear operable to record crank angle information.

13. A system, comprising: a central processing unit of an internal combustion engine, wherein the central processing unit is operable to receive cylinder pressure data via a time-slot method, wherein a cycle time of the time-slot method is smaller than a revolution of the internal combustion engine corresponding to a maximum speed of the internal combustion engine.

14. The system of claim 13, comprising: a pressure sensor for each cylinder of the internal combustion engine; a data acquisition unit; a data communication unit; and a measurement node formed by combining each pressure sensor with the data acquisition unit and the data communication unit, wherein the central processing unit is operable to receive the cylinder pressure data from the measurement node via the time-slot method.

15. The system of claim 13, comprising the internal combustion engine having the central processing unit.

16. The system of claim 15, wherein the internal combustion engine comprises a plurality of cylinders and a plurality of pressure sensors, and the central processing unit is operable to receive the cylinder pressure data for the plurality of cylinders with the plurality of sensors via the time-slot method.

17. The system of claim 15, comprising a ring gear connected to a crankshaft of the internal combustion engine, with a pick-up arranged on the ring gear operable to record crank angle information.

18. The system of claim 13, wherein the cylinder pressure data is cylinder specific.

19. The system of claim 13, wherein the cycle time is equal to a duration of the revolution of the internal combustion engine corresponding to the maximum speed of the internal combustion engine divided by a value greater than one, wherein the value is selected up to about 50.

20. The system of claim 13, wherein the cycle time is at least approximately 50 times smaller than the revolution of the internal combustion engine corresponding to the maximum speed of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In an embodiment explained in more detail with reference to the following figures. The drawings in detail:

(2) FIGS. 1A, 1B, and 1C are diagrams of the logical units combined in measurement nodes;

(3) FIG. 2 is a schematic representation of the arrangement of the measurement nodes in a topology according to a preferred exemplary embodiment;

(4) FIG. 3 is a schematic representation of cylinder pressure curves of an internal combustion engine to illustrate the cycle time; and

(5) FIG. 4 is a diagram of an internal combustion engine.

DETAILED DESCRIPTION

(6) FIG. 1A shows in a schematic representation that the cylinder pressure sensor 1, the data acquisition unit 3 and the data communication unit 4 are functionally combined to form a measurement node 5. The cylinder pressure sensor 1 measures cylinder pressure signals. The data acquisition unit 3 digitizes the cylinder pressure signals and stores them. The data communication unit 4 provides the digitized stored signals as data packets to the data bus 10 according to a time-slot method. The components can be structurally combined or also arranged separately from one another (only combined as logical units).

(7) FIG. 1B shows the variant in which a pick-up 9 for providing crank angle information is also included in the measurement node 5.

(8) The data acquisition unit 3 can thus process cylinder pressure signals and/or crank angle information.

(9) FIG. 1C shows a diagram of a crank angle measurement node 5, which does not process any cylinder pressure signals, but only crank angle information from the pick-up 9.

(10) FIG. 2 shows the arrangement of measurement nodes 5 and a central processing unit 2 in a preferred exemplary embodiment. The topology is designed here as a so-called line topology, i.e. the logical or physical units, in this case the measurement nodes 5, are in a serial communication connection with the central processing unit 2. Different topologies of the data bus 10 between the measurement nodes 5 are of course also possible, for example a star topology or a ring topology. The data packets are forwarded by the individual measurement nodes 5 via a common line to the central processing unit 2.

(11) FIG. 3 shows the cylinder pressure curve plotted over the crankshaft angle for four cylinders of an internal combustion engine. The representation serves to illustrate the cycle time t.sub.z during which cylinder pressure data is recorded via the measurement node 5 and stored there until the cycle time t.sub.z has elapsed.

(12) As soon as the cycle time t.sub.z has elapsed, the data packets are made available to the data bus 10 according to the time-slot method.

(13) A time-slot method is a modulation method in which the information of a participant is sent only in short time periods. A time slot is thus a time period of predetermined length within which a participant in a network can provide information. Applied to this invention, the time slot corresponds to the cycle time t.sub.z in which measured values of the cylinder pressure are transmitted by the individual cylinder pressure sensors 1. For a given length of the cycle time t.sub.z it depends on the current speed of the internal combustion engine and the resolution of the crankshaft angle signal, how many data points are acquired within a cycle time t.sub.z.

(14) It is in an embodiment provided that the cycle time t.sub.z of the time-slot method is selected to be smaller, in an embodiment approximately 50 times smaller than the minimum achievable period of one revolution of an internal combustion engine 6 corresponding to the maximum speed of the internal combustion engine 6. From the speed of an internal combustion engine 6, it is easy to calculate the period (duration) of one revolution. For example, if the speed is 1,000 rpm.sup.1, then the period is 60/100 seconds or 60 ms (milliseconds) long. A suitable cycle time t.sub.z of the time-slot method would therefore be 60/50=1.2 ms long.

(15) In the invention, the cylinder pressure data is distributed in a common communication system based on time, collected at the central processing unit 2 and combined there into the cylinder pressure curves. In the cycle time t.sub.z (=time required to interrogate all the measurement nodes 5) of the communication system, each cylinder pressure sensor 1 transmits the information (curve section) recorded by it in this time span via the communication network to the central processing unit 2.

(16) FIG. 4 shows a schematic representation of an internal combustion engine 6 with a plurality of the cylinders 7. The cylinders 7 are each equipped with at least one cylinder pressure sensor 1, from which cylinder pressure values are first transferred via a signal line 11 from the cylinder pressure sensor 1 to a data acquisition unit 3 and a data communication unit 4. This is shown by way of example in a cylinder 7.

(17) The cylinder pressure values are collected via the data acquisition unit 3 and the data communication unit 4 in a measurement node 5. The measurement node 5 is shown as a dashed box. The individual measurement nodes 5 are connected to a data bus 10. As an example, it is shown that a measurement node 5 is assigned to exactly one cylinder pressure sensor 1. It can also be provided that a plurality of cylinder pressure sensors 1 are combined in a measurement node 5. It has been found to be particularly advantageous to combine two adjacent cylinder pressure sensors 1 in a measurement node 5. To a crankshaft of the internal combustion engine 6, a ring gear is connected, on which a pick-up 9 for recording crank angle information (speed, crank angle) is arranged.

(18) It can be provided (illustrated as variant I) that the pick-up 9 transmits the crank angle information to a measurement node 5. In this variant, the measurement node 5 comprises the cylinder pressure sensor 1, the data acquisition unit 3, the data communication unit 4 and the pick-up 9.

(19) According to variant II, the pick-up 9 can transmit the crank angle information to a crank angle measurement node 5 which does not process cylinder pressure values from a cylinder pressure sensor 1.

(20) This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.