Ignition coil tester

The present invention relates to an ignition coil tester having a control module and an output electronics for testing the functioning of rod-type ignition coils, which is connectible to a diagnostic tester, the rod-type ignition coil having a primary winding and a secondary winding for generating the ignition voltage as well as a field guide plate, a plug connector and a secondary output. To be able to perform a component test on a rod-type ignition coil uninstalled from an internal combustion engine, the present invention provides for the ignition coil tester to have a housing and a spark plug dome for receiving the rod-type ignition coil, the dimensions and shape of which essentially correspond to those of a spark plug dome in an internal combustion engine and/or are adjustable to the dimensions of the latter.

FIELD OF THE INVENTION

The present invention relates to an ignition coil tester for testing the functioning of rod-type ignition coils, which is connectible to a diagnostic tester, the rod-type ignition coil having a primary winding and a secondary winding for generating the ignition voltage as well as a field guide plate, a plug connector and a secondary output.

BACKGROUND INFORMATION

To measure the high voltage transmitted from an ignition coil to the spark plug via a cable for the purpose of testing the functioning of single-spark ignition coils, a tong-test instrument is already known, which can be clamped onto the outer shell of the line carrying the high voltage. For this purpose, two conductor surfaces of the tong-test instrument surround the high-voltage cable. In this manner, the ignition coil can be tested in the installed state. Ignition devices having multiple rod-type ignition coils for an internal combustion engine are known from German Published Patent Application No. 298 18 882. In this instance, the rod-type ignition coils are located within a so-called spark plug dome of the cylinder head of the internal combustion engine.

A high-voltage connector attached to the respective rod-type ignition coil, which establishes the connection between a high-voltage output of the rod-type ignition coil and a terminal stud of the spark plug that is mounted in a stationary manner in the spark plug dome, is inserted into the spark plug dome.

In internal combustion engines having rod-type ignition coils, in which the latter are directly connected to the spark plugs without the interconnection of a cable, an ignition coil test cannot be performed in the installed state of the rod-type ignition coils by using the known tong-test instrument since the secondary winding and the secondary circuit of the rod-type ignition coils for the ignition voltage diagnosis are partly inaccessibly located inside the spark plug domes.

For this reason, rod-type ignition coils today are tested in the uninstalled state. Requiring numerous auxiliary devices, the loose measuring structures used for this purpose, however, for safety-related reasons do not allow for the measurement to be carried out directly on the internal combustion engine. Moreover, the testing conditions of an uninstalled rod-type ignition coil are different that those of one that is installed. Consequently, the testing results do not completely match the actual values in the operating state or it is not possible to perform all tests under actual conditions.

The objective of the present invention is to provide an ignition coil tester in connection with a diagnostic tester for the component testing of a rod-type ignition coil uninstalled from an internal combustion engine.

SUMMARY OF THE INVENTION

The objective of the present invention is achieved in that an ignition coil tester has a housing and a spark plug dome for receiving the rod-type ignition coil, the dimensions and shape of which essentially correspond to those of a spark plug dome in an internal combustion engine and/or are adjustable to the dimensions of the latter. The ignition coil uninstalled from the internal combustion engine is installed into the ignition coil tester, where it is tested. Adjusting the shape of the ignition coil dome of the ignition coil tester to the shape of the ignition coil dome in the internal combustion engine allows the test to be performed under nearly actual ambient conditions. The compact construction of the ignition coil tester, into which the required auxiliary devices for spark plug testing are integrated, allows for ignition coils to be tested while respecting the safety-related requirements without having loose measuring structures outside of the internal combustion engine.

In a preferred specific embodiment, the diameter of the spark plug dome is adjustable to the diameter of the rod-type ignition coil and of the spark plug dome of the internal combustion engine by way of an interchangeable insulator and/or an interchangeable metal sleeve. This variable construction allows for the ignition coil tester to be optimally adapted to the geometry of the spark plug dome of the internal combustion engine. Through coupling capacitances to the electrical ground of the metal sleeve or of the housing of the ignition coil tester, the distance between the metal sleeve and the rod-type ignition coil determines the damping ratio, which in this manner can be adjusted to the actual conditions.

If the height of the spark plug dome can be adjusted to the length of the rod-type ignition coil and of the spark plug dome of the internal combustion engine using an interchangeable or adjustable distance adjustment piece, then the ignition coil tester can be used for different rod-type ignition coils of different lengths as well as for different internal combustion engines having spark plug domes of different lengths. Due to the fact that a spark plug or a gas spark gap can be inserted into the ignition circuit, the necessary tests can be carried out at the rod-like ignition coil. Thus, the spark plug may be switched into the ignition circuit for measuring ignition voltage and for testing diodes. For diagnosing the ignition signal and for testing the ignition reserve, on the other hand, a suitable gas spark gap may be used.

The electrical connection between the rod-type ignition coil and the chosen spark gap may be established by an adjustment sleeve as a connecting piece from the secondary output of the rod-type ignition coil to the gas spark gap or the spark plug. The adjustment sleeve may be adjusted in its dimensions as well as in the design of its end contacts to the rod-type ignition coil to be tested in the respective installation configuration and to the contacts of the spark gaps, which allows for a correspondingly versatile use of the ignition coil tester.

For capacitive ignition signal uncoupling for diagnosing the ignition voltage, a capacitive sensor may be attached to the adjustment sleeve. In this region it is possible to provide sufficient space for accessing the secondary electric circuit. Furthermore, the construction of the adjustment sleeve may be optimally adjusted to the measuring task of determining the precise ignition voltage by choosing suitable dimensions and materials.

Due to the fact that the housing in the region of the capacitive sensor has an aperture for a measuring line of the capacitive sensor and/or in the region of the field guide plate has an aperture for contacting the field guide plate, the corresponding measuring signals may be transmitted via measuring and/or signal lines from the housing of the ignition coil tester to the output electronics and the diagnostic system.

The aperture for contacting the field guide plate and the metal sleeve is preferably insulated with respect to a signal line by a high-voltage insulation. This prevents the measuring signal from being diverted to the housing of the ignition coil tester when an insulation test is performed at this location regarding high-voltage flashovers in the rod-type ignition coil to the field guide plate or to the surroundings.

For reasons of a simple manufacture of the ignition coil tester, the housing may be provided as a one-part or multi-part design. Particularly a multi-part construction may avoid difficult undercutting processes.

A particularly compact and user-friendly design of the entire assemblage is achieved when the control module is connected with the housing as one unit.

The ignition coil tester may also be designed in such a way that it can be used for testing single-spark ignition coils having secondary windings situated outside of the spark plug dome. Here too it is an advantage that the single-spark ignition coil can be tested in the spark plug dome of the ignition coil tester under almost actual conditions. The ignition coil tester may thus be used in a very versatile manner.

DETAILED DESCRIPTION

The FIGURE shows an ignition coil tester1with an inserted rod-type ignition coil20. Ignition coil tester1is made of a housing30, which is made up of an upper housing part40and a lower housing part50.

Upper housing part40surrounds a recess41, the dimensions of which essentially correspond to the dimensions of a spark plug dome of common internal combustion engines. An interchangeable insulator11and within it an interchangeable metal sleeve12are inserted in recess41.

Recess41, insulator11and metal sleeve12have a cylindrical shape in the design shown. However, depending on the shape of rod-type ignition coil20and of the spark plug dome of the internal combustion engine to be adjusted, other geometries are possible as well.

On the side facing lower housing part50, the cylindrically shaped region11aof insulator11is bounded by a peripheral frontal termination11b, which has metal sleeve12abutting against it. Metal sleeve12is thus completely insulated with respect to housing30. If no insulation test is conducted, then metal sleeve12may be connected to ground (B−) via a switch75.

Rod-type ignition coil20having primary winding21and secondary winding22, field guide plate24and secondary output25is located within metal sleeve12, which bounds spark plug dome10of ignition coil tester1. Only plug connecter23of rod-type ignition coil20having built-in switch-on diode26and integrated output stage is located outside of spark plug dome10.

At the upper opening of recess41, a receptacle42in the form of a peripheral, stepped milled-out recess is provided for receiving an interchangeable distance adjustment piece13. Using this distance adjustment piece13, it is possible to adjust the height of spark plug dome10to the length and to the diameter of rod-type ignition coil20. Rod-type ignition coil20rests with its plug connector23against distance adjustment piece13.

On the opposite side, recess41passes over into a cylindrical duct45having a smaller diameter than recess41of upper housing part40.

In the region of field guide plate24of rod-type ignition coil20, upper housing part40has a radially positioned aperture43in the form of a bore hole, the surface of which is lined with a high-voltage insulation44. Aperture43receives a signal line71.

Lower housing part50is flanged to upper housing part40on the side of duct45. Together with the bottom side of upper housing part40, it forms a recess51, which, separated by a moveable mounting plate53, is closed off by a spark chamber52. On or at grounded mounting plate53in the design shown, a gas spark gap15is mounted as well as, in a specifically provided tape hole, a spark plug16, the electrodes of which project into spark chamber52. However, additional spark gaps, for example various gas spark gaps, may also be provided.

An adjustment sleeve14is provided between secondary output25of rod-type ignition coil20and spark plug16switched into the ignition circuit as a spark gap in the example shown. This is made up of a conductive core14a, which is embedded in an insulating sleeve14b. Insulating sleeve14bitself is fitted into duct45of upper housing part40and projects with its one side into recess41of upper housing part40and with its other side into recess51of lower housing part50. On the side of upper housing part40, an input contact14cconnected to conductive core14aprovides a conductive connection to secondary output25of rod-type ignition coil20, and an output contact14d, likewise connected to conductive core14a, provides a conductive connection to the chosen spark gap, in the case shown to spark plug16.

On the side of lower housing part50, a capacitive sensor17is situated on the outer surface of adjustment sleeve14in the region of conductive core14a. This is connected to a measuring line72, which is guided to the outside via an aperture54radially positioned in lower housing part50. The sensor is used for uncoupling the ignition signal for the diagnosis of the ignition voltage.

Measuring line72and signal line71are guided into a schematically represented output electronics70, which in turn has two measuring outputs73,74for connecting a diagnostic system (not shown).

Plug connector23of rod-type ignition coil20is connected to a control module60via an adapter line61. Ignition coil tester1is supplied with voltage via a voltage input63on control module60. Control module60has a shunt64for measuring the secondary ignition current (measuring point (69)) and, in the variant of the embodiment shown, an output stage62. In the case of rod-type ignition coils20that have an integrated output stage, this output stage62may be omitted, although the fundamental construction of ignition coil tester1and its mode of operation remain the same. Supply voltage B+ (input (65)) of rod-type ignition coil (20) may be set in a variable manner, whereby the secondary voltage can be adjusted to the specification of the ignition coil. This makes it possible to test the ignition reserve and the voltage endurance of the insulation of rod-type ignition coil (20). Within control module (60), primary control signal (66) adjustable in terms of pulse duration, primary voltage (measuring point (67)), primary current (measuring point (68)), adjustable supply voltage (input (65)) and secondary ignition current (measuring point (69)) are available for evaluation. By disconnecting the supply voltage, the spark gaps can be safely changed.

An extension of the described ignition coil tester (1) makes it possible also to adjust parameters such as the operating temperature of the rod-type ignition coil (20) and the compression pressure in spark chamber (52) to the actual conditions existing in the internal combustion engine. It is then possible to test rod-type ignition coils (20) under the same conditions as in the internal combustion engine.