SENSOR UNIT FOR A LENGTH-ADJUSTABLE CONNECTING ROD

Abstract

A device for an internal combustion engine, in particular a spark ignition engine, with a length-adjustable connecting rod and a sensor unit for detecting the adjustment in length of the connecting rod is provided. The length-adjustable connecting rod comprises a first connecting rod member for receiving a piston pin and a second connecting rod member for receiving a crankshaft journal, where the distance in length between the piston pin and the crankshaft journal is adjustable by way of the connecting rod. The sensor unit comprises a sensor and an index region provided on the length-adjustable connecting rod, where a property of the index region that is dependent upon the adjustment in length of the connecting rod can be detected by way of the sensor. An internal combustion engine with such a device, comprises a length-adjustable connecting rod and a sensor unit as well as the use of such a sensor unit and a length-adjustable connecting rod.

Claims

1. A device for an internal combustion engine, in particular a spark ignition engine, with a length-adjustable connecting rod, said length-adjustable connecting rod comprises a first connecting rod end for receiving a piston pin and a second connecting rod end for receiving a crankshaft journal, where the length between said piston pin and said crankshaft journal is adjustable by way of said connecting rod; wherein said device comprises a sensor unit for detecting the adjustment in length of said connecting rod, where said sensor unit comprises a sensor and an index region provided on said length-adjustable connecting rod, and where a property of said index region that is dependent upon the adjustment in length of said connecting rod is detectable by said sensor.

2. The device according to claim 1, wherein said sensor is an optical, inductive, capacitive or acoustic sensor.

3. The device according to claim 1 or 2, characterized in that wherein said sensor is a contactless distance sensor, preferably an optical, inductive, capacitive or acoustic distance sensor.

4. The device according to claim 1, wherein said index region is formed on a surface of said length-adjustable connecting rod.

5. The device according to claim 4, wherein said index region on said length-adjustable connecting rod has a structured surface, preferably a structured surface with projections projecting in the direction of a distance sensor.

6. The device according to claim 1, wherein said length-adjustable connecting rod comprises at least a first connecting rod member with said first connecting rod end and a second connecting rod member with said second connecting rod end, where said first connecting rod member is movable relative to said second connecting rod member in the longitudinal direction of said connecting rod in order to adjust the distance between said piston pin and said crankshaft journal, and where said index region is arranged on said second connecting rod member for receiving said crankshaft journal.

7. The device according to claim 6, wherein at least one cylinder-piston assembly is provided for moving said first connecting rod member relative to said second connecting rod member, where said first connecting rod member is connected to an adjustable piston of the cylinder-piston assembly and said second connecting rod member comprises a cylinder bore of the cylinder-piston assembly.

8. The device according to claim 1, wherein, said sensor unit comprises a control device which is coupled to said sensor for detecting the property of said index region which is dependent upon the adjustment in length of said connecting rod.

9. Use A use of a sensor unit for detecting the adjustment in length of a length-adjustable connecting rod with an index region provided on said length-adjustable connecting rod and a sensor, preferably a contactless distance sensor, where said length-adjustable connecting rod comprises a first connecting rod end for receiving a piston pin and a second connecting rod end for receiving a crankshaft journal, where the distance between said piston pin and said crankshaft journal is adjustable and said sensor detects a property of said index region that is dependent upon the adjustment in length of said connecting rod, preferably the distance between said index region and said sensor.

10. A use of a length-adjustable connecting rod with an index region (26) internal combustion engine (1), where a sensor (6), preferably a contactless distance sensor, detects a property of said index region (25) that is dependent upon the adjustment in length of said connecting rod (26), preferably the distance between said index region (26) on the said length-adjustable connecting rod (6.1) and the distance sensor affixed relative to said internal combustion engine (1).

11. An internal combustion engine with at least one cylinder, a reciprocating piston moving in said cylinder and at least one adjustable compression ratio in a cylinder, and with a length-adjustable connecting rod connected to said reciprocating piston and a sensor unit according to said device according to claim 1.

12. A method for detecting the adjustment in length of a length-adjustable connecting rod with an index region provided on said length-adjustable connecting rod (6.1), a sensor (25) and a control device, comprising the steps of: detecting by way of said sensor a property of said index region that is dependent upon the adjustment in length of said connecting rod, comparing the detected property of said index region with a reference value in said control device, and calculating the adjustment in length of a length-adjustable connecting rod (64) using said control device.

13. The method according to claim 12, where said sensor is a contactless distance sensor, comprising the steps of: detecting the distance between said index region and said sensor, comparing the distance with a reference value in said control device, and calculating the adjustment in length of a length-adjustable connecting rod using said control device.

14. The method according to claim 12, where said control device triggers the detection by way of said sensor of a property of said index region that is dependent upon the adjustment in length of said connecting rod.

Description

[0026] In the following, an embodiment shall be explained in more detail with reference to a drawing, where:

[0027] FIG. 1 shows a schematic cross-sectional view through an internal combustion engine, and

[0028] FIG. 2 shows a side view of a device according to the invention for an internal combustion engine with a length-adjustable connecting rod and a sensor unit,

[0029] FIG. 3 shows a sectional view through the internal combustion engine from FIG. 1 along a length-adjustable connecting rod in a short position and

[0030] FIG. 4 shows a sectional view through the internal combustion engine from FIG. 1 along a length-adjustable connecting rod in a long position.

[0031] FIG. 1 shows a schematic representation of an internal combustion engine (spark ignition engine) 1. Internal combustion engine 1 has three cylinders 2.1, 2.2 and 2.3, in each of which a reciprocating piston 3.1, 3.2, 3.3 moves up and down. Furthermore, internal combustion engine 1 comprises a crankshaft 4 which is rotatably mounted by way of crankshaft bearings 5.1,5.2, 5.3 and 5.4. Crankshaft 4 is connected to associated reciprocating pistons 3.1, 3.2 and 3.3 by way of respective connecting rods 6.1, 6.2 and 6.3. Crankshaft 4 comprises an eccentrically arranged crankshaft journal 7.1, 7.2 and 7.3 for each connecting rod 6.1, 6.2 and 6.3. Second connecting rod end 8.1, 8.2, and 8.3 is respectively supported on associated crankshaft journal 7.1, 7.2 and 7.3 First connecting rod end 9.1, 9.2 and 9.3 is respectively mounted on a piston pin 10.1, 10.2 and 10.3 and is thus pivotally connected to associated reciprocating piston 3.1, 3.2 and 3.3. In technical parlance, first connecting rod ends 9.1, 9.2 and 9.3 receiving piston pins 10.1, 10.2 and 10.3 are referred to as the connecting rod small end and second connecting rod ends 8.1.8.2 and 7.3 receiving crankshaft journals 7.1.7.2 and 7.3 are referred to as the connecting rod large end, where no absolute or relative size association can be derived from these terms, but they only serve to differentiate the components and the association to the internal combustion engine shown in FIG. 1. Accordingly, the dimensions of the diameters of first connecting rod ends 9.1, 9.2 and 9.3 can be smaller, equal or larger than the dimensions of the diameters of second connecting rod ends 8.1, 8.2 and 8.3.

[0032] Crankshaft 4 is provided with a crankshaft sprocket 11 and coupled to a camshaft sprocket 13 by way of a timing chain 12. Camshaft sprocket 13 drives a camshaft 14 with its associated cams for operating the intake and exhaust valves (not shown in detail) of each cylinder 2.1, 2.2 and 2.3. The return span of timing chain 12 is tensioned by use of a pivotally arranged tensioning rail 15 which is pressed thereagainst by way of a chain tensioner 16. The drive span of timing chain 12 can slide along a guide rail. The essential mode of operation of this timing system, including fuel injection and ignition by way of a spark plug, shall not be explained in detail and is assumed to be known. The eccentricity of crankshaft journals 7.1, 7.2 and 7.3 substantially determines the stroke H.sub.K, in particular where, as presently, crankshaft 4 is arranged exactly centrically beneath cylinders 2.1, 2.2 and 2.3. Reciprocating piston 3.1 is shown in its lowermost position in FIG. 1, whereas reciprocating piston 3.2 is shown in its uppermost position. The difference presently defines stroke the H.sub.K. The remaining height H.sub.c (see cylinder 2.2) determines the remaining compression height in cylinder 2.2. In connection with the diameter of reciprocating piston 3.1, 3.2 or 3.3 or associated cylinders 2.1, 2.2 and 2.3, respectively, the displacement V.sub.h is obtained from the stroke H.sub.K and the compression volume V.sub.c is calculated from the remaining compression height H.sub.c. The compression volume V.sub.c is of course decisively dependent on the design of the cylinder cover. The compression ratio ε arises from these volumes V.sub.h and V.sub.c. In detail, the compression ratio ε is calculated from the sum of the displacement volume V.sub.h and the compression volume V.sub.c divided by the compression volume Vc. Typical values today for spark ignition engines range between 10 and 14.

[0033] To allow for the compression ratio ε to be adapted in dependence of the operating point (rotational speed n, temperature T, throttle position) of internal combustion engine 1, connecting rods 6.1, 6.2 and 6.3 are designed to be adjustable in their length. As a result, a higher compression ratio can be obtained in the partial load range than in the full load range.

[0034] FIG. 2 shows by way of example a side view of length-adjustable connecting rod 6.1, which is identical to connecting rods 6.2 and 6.3 of internal combustion engine from FIG. 1. The description therefore applies accordingly. Connecting rod 6.1 comprises a first connecting rod member 18.1 with a connecting rod head 17.1 and said first connecting rod end 9.1, where first connecting rod member 18.1 is guided in a telescoped manner in a second connecting rod 19.1. The relative motion of first connecting rod member 18.1 in the longitudinal direction toward second connecting rod member 19.1 is effected in particular by way of a cylinder-piston assembly (not shown) integrated into second connecting rod member 19.1 with an adjustable piston which is movably received in a cylinder bore, as well as a sealing device between the adjustable piston and the cylinder bore. Arranged at second connecting rod member 19.1 is a lower bearing shell 20.1 which, together with the lower portion of second connecting rod member 19.1, surrounds second connecting rod end 8.1. Lower bearing shell 20.1 and second connecting rod member 19.1 are attached to each other with attachment bolts 21.1. First connecting rod member 18.1 between connecting rod head 17.1 and second connecting rod member 19.1 comprises a piston rod 22.1 which is typically connected at the lower end of first connecting rod member 18.1 to the adjustable piston of the cylinder-piston assembly. At the upper end of second connecting rod member 19.1, piston rod 22.1 is slidably inserted into second connecting rod member 19.1 through a correspondingly sealed bore. To change the length of connecting rods 6.1 by way of the cylinder-piston assembly, a hydraulic adjustment mechanism (not shown) is provided which controls the inlet and outlet of the engine oil into and out of the cylinder-piston assembly and thereby causes connecting rod 6.1 to be affixed in the short and long position.

[0035] Shown in FIG. 2 are length-adjustable connecting rods 6.1 as well as a sensor unit 24 as parts of device 23 according to the invention. Sensor unit 24 comprises a sensor 25 and an index region 26 provided on second connecting rod member 19.1. The shape and structure of index region 26 is dependent upon sensor unit 24 selected and its arrangement, mode of operation and sensitivity. Sensor 25 detects the distance from index region 26 as indicated by the double arrow between sensor 25 and index region 26 Accordingly, sensor 25 in the embodiment shown is configured as a contactless distance sensor. In the embodiment shown in FIG. 2, index region 26 on the side of second connecting rod member 19.1 facing sensor 25 is configured as a structured surface 27 with several projections 28 projecting rectangularly in the direction of sensor 25.

[0036] The sectional view through internal combustion engine 1 in FIG. 3 shows device 23 according to the invention with length-adjustable connecting rod 6.1 in a short position. Sensor 25 is affixed in position in internal combustion engine 1 and detects the distance from index region 26 on second member 19.1 of length-adjustable connecting rod 6.1. FIG. 4 shows device 23 according to the invention from FIG. 3 with length-adjustable connecting rod 6.1 in a long position.

[0037] As can be seen from the comparison between Figures. 3 and 4, in a long position of connecting rod 6.1, reciprocating piston 3.1 is inserted deeper into cylinder 2.1 while the angular position of crankshaft 4 or crankshaft journal 7.1 remains the same, so that a higher compression ratio arises during operation in cylinder 2.1 of FIG. 4. In addition to the difference between the position of reciprocating piston 3.1 in cylinder 2.1 due to the adjustment in length of connecting rod 6.1 to the extended long position, the changed distance between second connecting rod member 19.1 and sensor 25 affixed in internal combustion engine 1 is also very clearly evident in FIG. 4. The measured values of sensor 25, in particular a distance measurement to index region 26 on second connecting rod member 19.1, can be detected with a control device (not shown) connected to sensor 25 and be compared with a reference profile. At the same time, the control device can control the measurement of sensor unit 24 in such a way that the measurement takes place only at a specific angular position of crankshaft 4. In addition to the detection of the current position of length-adjustable connecting rod 6.1, the control device can also evaluate the position of connecting rod 6.1 in dependence of parameters and performance data of internal combustion engine 1 from the engine control device and can generate a corresponding signal independently of the engine control device for driver information and for consideration in the operational safety of internal combustion engine 1 if the expected switching position deviates over a certain number of cycles.

LIST OF REFERENCE NUMERALS

[0038] 1. internal combustion engine [0039] 2.1.2.2.2.3 cylinder [0040] 3.1.3.2.3.3 reciprocating piston [0041] 4 crankshaft [0042] 5.1,5.2,5.3,5.4 crank shaft bearing [0043] 6.1.6.2.6.3 connecting rod [0044] 7.1.7.2.7.3 crankshaft journal [0045] 8.1.8.2.8.3 second connecting rod end [0046] 9.1.9.2.9.3 first connecting rod end [0047] 10.1.10.2.10.3 piston pin [0048] 11 crankshaft sprocket [0049] 12 timing chain [0050] 13 camshaft sprocket [0051] 14 camshaft [0052] 15 tensioning rail [0053] 16 chain tensioner [0054] 17.1 connecting rod head [0055] 18.1 first connecting rod member [0056] 19.1 second connecting rod member [0057] 20.1 bearing shell [0058] 21.1 attachment bolt [0059] 22.1 piston rod [0060] 23 device [0061] 24 sensor unit [0062] 25 sensorF [0063] 26 index region [0064] 27 structured surface [0065] 28 projections [0066] V.sub.h displacement volume [0067] V.sub.c compression volume [0068] H.sub.c compression height [0069] H.sub.K stroke [0070] εcompression ratio [0071] n rotational speed [0072] T temperature