The present invention relates to a method for diagnosing an electromagnetic actuator of a sliding cam valve train of an internal combustion engine. The actuator has at least one actuator pin which, as a result of electrical energizing of the actuator, is released and dips into a groove-like displacement slot which passes through a cylindrical slot section of the associated sliding cam and ends, in the rotation direction of the cam, with an upward slope onto the cylindrical circumference of the slot section.
The sliding cam valve trains, which are known in various configurations, serve for actuating, with variable lift, the gas exchange valves of internal combustion engines. The variability in lift is generated by the camshaft, which includes a carrier shaft and a sliding cam situated thereon rotatably fixed and movable between axial positions. The sliding cam has at least one set of cams, including cams having different bumps, and a groove-like displacement slot into which an actuator pin, which extends out of an actuator, dips in order to move the sliding cam on the carrier shaft between the axial positions and thus to shift the present lift pick-up from one cam to the other cam.
Valve trains including electromagnetic actuators and displacement slots of the type mentioned at the outset are known from DE 10 2007 010 149 A1 with two Y-shaped and circumferentially parallel grooves, from DE 10 2009 053 116 A1 with two X-shaped and circumferentially parallel grooves, and from DE 10 2009 009 080 A1 with two S-shaped grooves arranged circumferentially in series.
The sliding cam switchover process is intended to be able to take place in a precise and reproducible manner even at a preferably high rotational speed of the camshaft and therefore within an extremely short period of time and is intended to be completed for all cylinders of the internal combustion engine within one working cycle and without any shifting errors. Ideally, therefore, all actuators of the valve train are not only sufficiently fast but also are without appreciable time variations with regard to the release and movement behavior of the actuator pins extending out of the actuator. Actuators which are particularly suitable for this have actuator pins which are held in the retracted state by the holding force of a permanent magnet counter to the force of a spring. The actuator pins are released by briefly energizing an electromagnet, which temporarily neutralizes the effect of the permanent magnet, whereupon the actuator pin extends out of the actuator due to the spring force. The return retracting movement into the actuator is brought about by the groove which slopes upward at the end of the displacement slot onto the cylindrical circumference of the slot section. The operating principle of such an actuator is known from EP 1 421 591 B1.
Of course, the minimum duration of the energization time necessary to release the respective actuator pin, in which the holding force of the permanent magnet is not yet overcome and the actuator pin remains in the retracted position, nevertheless varies in real operation. Causes for the variation in this time interval, which will also be referred to below as dead time, are in particular the mechanical and electrical manufacturing tolerances of the actuator components and their operation-related differing progression of wear. In order to ascertain the extent of this variation, often complicated parameter studies are required which may be carried out with reasonable effort but only on a limited number of samples. The maximum value for the dead time variation ascertained during these studies must then be adhered to during operational actuation of all actuators, so that the operating range, in particular the speed and temperature range, in which the sliding cam valve train could be switched over with sufficient precision is undesirably limited.
It is an object of the present invention to provide a method for diagnosing an actuator of the type mentioned at the outset, which enables an individual and up-to-date dead time ascertainment for the actuator pins with preferably little effort.
The present invention provides that the following diagnostic steps are to be carried out during operation of the internal combustion engine:
a) energizing the actuator with current parameters of a variable actuator characteristic map in such a way that the actuator pin is released when the cylindrical circumference overlaps the actuator pin circumferentially and a directly subsequent dip of the actuator pin into the displacement slot does not result in any displacement of the sliding cam;
b) detecting whether the released actuator pin generates in the actuator a rejection signal due to the upward slope from the displacement slot onto the cylindrical circumference;
c) if no rejection signal is detected, repeating step a) using at least one changed current parameter and step b);
d) updating the actuator characteristic map with the changed current parameter.
The diagnostic method according to the present invention is based on the concept of ascertaining, with predefined accuracy requirements, the dead time of preferably all actuator pins, without this leading to any displacement of the sliding cam. The instantaneously diagnosed actuator pin may be extended in order to check its present actual dead time, but may carry out no displacement in the process since it may dip only into the groove section, which is then without axial lift, at the end of the displacement slot immediately adjacent to the cylindrical circumference. Depending on the actuator energization parameters initially used in this diagnostic shifting, a rejection signal is either detected or not detected. The rejection signal is generated (for example in the form of an induced voltage that is relatively easy to detect and to process) by the actuator pin when the latter is guided back into the actuator by the displacement slot which slopes upward at the end back onto the cylindrical circumference of the slot section. A prerequisite for this is the previous release and dip of the actuator pin into the displacement slot and a corresponding energization of the actuator, from which sufficiently accurate conclusions may be drawn about the present duration of the dead time of the individual actuator pin. Based hereupon, the actuator characteristic map serving for operational control of the actuator may be updated as often as desired and with the desired accuracy in terms of the dead time to be adhered to individually for each actuator pin, and the operating range of the valve train that is permitted for switchovers may be maximized.
Further features of the present invention result from the following description and from the drawings, which serve to explain the method according to the present invention by way of example. Unless mentioned otherwise, identical or functionally equivalent features or components are provided with the same reference numerals.
If, as shown in
The situation is different in
The diagnostic shifting is carried out not only at predefined long-term intervals to update the actuator characteristic map with the dead times, which change due to progressive wear, individually for all actuators. Instead, the diagnosis also takes place in different operating states of the internal combustion engine, in particular at a different operating temperature or with a different supply voltage (vehicle electrical system voltage) as characteristic map parameters.
Number | Date | Country | Kind |
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10 2013 201 827 | Feb 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/DE2013/200349 | 12/11/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/121771 | 8/14/2014 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
6967550 | Elendt | Nov 2005 | B2 |
8047065 | Cinpinski | Nov 2011 | B2 |
8181508 | Cinpinski | May 2012 | B2 |
8186320 | Schiepp | May 2012 | B2 |
8191524 | Elendt | Jun 2012 | B2 |
8365692 | Schoeneberg | Feb 2013 | B2 |
8474421 | Gregor | Jul 2013 | B2 |
8584639 | Elendt | Nov 2013 | B2 |
8707917 | Schiepp | Apr 2014 | B2 |
20040201441 | Elendt et al. | Oct 2004 | A1 |
20100126445 | Schiepp | May 2010 | A1 |
20100224154 | Elendt et al. | Sep 2010 | A1 |
20100269769 | Schoeneberg | Oct 2010 | A1 |
20110016958 | Cinpinski | Jan 2011 | A1 |
20110056448 | Cinpinski | Mar 2011 | A1 |
20110247577 | Elendt et al. | Oct 2011 | A1 |
20120152193 | Schiepp | Jun 2012 | A1 |
20130228039 | Nendel | Sep 2013 | A1 |
Number | Date | Country |
---|---|---|
10 2007 010 149 | Sep 2008 | DE |
102008020893 | Oct 2009 | DE |
102008060166 | Jun 2010 | DE |
10 2009 009 080 | Aug 2010 | DE |
10 2009 053 116 | Sep 2010 | DE |
1 421 591 | May 2004 | EP |
1811161 | Jul 2007 | EP |
WO2012072305 | Jun 2012 | WO |
Number | Date | Country | |
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20150377095 A1 | Dec 2015 | US |