Patent Grant
7178490
This application claims the benefit of priority to German Application No. 103 23 877.8, filed on May 26, 2003 in the German language, the contents of which are hereby incorporated by reference.
The invention relates to a device for electrohydraulic valve lift switching.
Such devices for electrohydraulic valve lift switching are deployed in modern internal combustion engines, to adjust the operation of the engine to the respective operating situation, so that engine power, fuel consumption or emission response can be optimized as a function of the operating situation. The aim is to reduce fuel consumption and emissions when the power requirement is low but otherwise to make maximum engine power available. An engine equipped thus is for example known from the article “Der neue Motor des Porsche 911 Turbo” (The new Porsche 911 Turbo engine”, MTZ Motortechnische Zeitung 61 (2000) 11, pages 730 to 743.
In the case of engines with electrohydraulic valve lift switching however not only is the valve lift switched but numerous engine control parameters are also changed. For an optimum effect it is of essential importance for all parameters to be coordinated in respect of each other and to be adjusted when a valve lift switch is effected. The time of the valve lift switch also has to be coordinated with the time of the other parameter changes. The problem arises here that the precise time of the valve lift switch is not known. It is known when a corresponding control signal is emitted but not the time when the valve lift switch is actually effected. One significant uncertainty factor when determining this time is the on/off valve, the switch response of which depends on temperature, oil pressure and many other influencing variables, which can in turn depend on the arrangement of the on/off valve within the engine. A precise conclusion about the switch time of the on/off valve or the occurrence of th e valve lift switch cannot therefore be obtained from the time of activation of the on-off valve. It cannot therefore be ensured that optimum coordination of the valve lift switch and other engine control parameters is achieved under all operating conditions.
It is known from the prior art that valve lift switching can be identified by means of a valve lift sensor. However this is relatively complex and expensive.
The invention relates to a device for electrohydraulic valve lift switching with a hydraulically activatable actuating element for bringing about valve lift switching, which is connected to an oil line, whereby the action of pressurized oil on the actuating element can be controlled by an on/off valve arranged in the oil line, and connected to a control device.
The invention discloses a device for electronic valve lift switching, with which the time when the valve lift switch is effected can be determined more precisely but which is still economical.
In one embodiment of the invention, there is a device in which an oil pressure metering device arranged in the oil line is provided, which is connected to the control device and a device is also provided for detecting the time period between activation of the on/off valve by the control device and a characteristic change in the measured oil pressure.
The inventive device utilizes the knowledge that a characteristic change in oil pressure takes place when the actuating element is activated. This is a brief pressure trough after the valve movement caused by the fact that after the on/off valve opens, a defined volume of oil flows to or into the actuating element. This pressure pattern can be measured by the oil pressure metering device and converted to an electrical signal proportional to pressure, which is sent to the control device. As the general pressure pattern during a valve lift switch is known, the measured pressure pattern can be used to identify the existence of a valve lift switch in a reliable manner.
The time between activation of the on/off valve by the control device and identification of a characteristic pattern of the measured oil pressure is analyzed by the control device or the engine control device. The coordination in respect of time of further valve lift switching processes can therefore be adjusted.
In a preferred embodiment, the oil pressure metering device is arranged on the supply side of the on/off valve.
It is also advantageous for the control device or the engine control device to see whether a pressure change or awaited characteristic pressure pattern has taken place and thereby to identify whether or not a switching process has taken place in the on/off valve.
In one advantageous embodiment of an inventive device for electrohydraulic valve lift switching, the on/off valve can be activated electrically. In an alternative embodiment, an additional pressure generator is provided, which can be activated by the control device and for its part activates the on/off valve hydraulically or pneumatically.
In a simple and therefore economical embodiment, the on/off valve is connected on the supply side to an engine oil circulation system. The actuating element is therefore activated via the standard engine oil and no additional hydraulic circuit is required.
The invention is described in more detail below with reference to exemplary embodiments in the figures, in which:
The on/off valve 4 is activated by a control device 3 by means of an electrical signal. On activation the on/off valve 4 opens and the pressurized oil in the oil line 2 on the supply side can therefore act on the actuating element 1. Displacement of an activation element in the actuating element 1 on the one hand brings about the valve lift switch, on the other hand oil has to follow from the oil line 2. This causes a short-term drop in oil pressure, from which it can be identified that a valve lift switch has taken place. The characteristic change in the measured oil pressure is advantageously detected on the supply side of the on/off valve 4 by an oil pressure metering device 5 and reported to the control device 3. The control device 3 analyzes the measured pattern of the oil pressure and is thereby able to detect and further process the time period between activation of the on/off valve 4 and the occurrence of a characteristic oil pressure change.
It would also be possible to arrange the oil pressure metering device 5 in a control section 10 of the oil line 2, located between the on/off valve 4 and the actuating element 1. However measurement is more complex, as when the on/off valve switches, the oil pressure in the control section 10 first increases and the short-term drop in pressure only occurs after movement of the activation element in the actuating element 1.
With an exemplary embodiment according to
With the embodiment according to
A further difference between the device in
If such a positive identification is made, the timer is stopped and the switch time is determined from the timer reading. If the switch time is within a predefined tolerance range, the existence of predefined conditions for repeat valve lift switching is awaited.
Otherwise coordination of the valve lift switch in respect of time is adapted based on the change in other parameters.
In the event that no characteristic change is identified in the oil pressure pattern, even though a switch operation should have taken place in the on/off valve 4, i.e. a corresponding switch signal was generated, the valve lift switch is “canceled”, which means that the parallel change in other engine control parameters is canceled. The existence of conditions for valve lift switching is then awaited again.
The time period Ts therefore refers to the time period from emission of the switch pulse for the on/off valve 4 to completion of the switching process. This represents important information for the control device 3 or the engine controller 9, as it provides knowledge about the response in respect of time of the control distance, which is of major significance for regulatory intervention in particular. The decisive factor in this context is the time, at which the switch pulse has to be emitted, so that switching takes place at a defined time in the future. Also detection of the switch time allows the long-term response of the system to be detected and the changed initial conditions can therefore be taken into account during valve lift switching processes.
If the awaited pressure pattern does not manifest itself, this means that a valve lift switch is not taking place or has not taken place and the measures already taken parallel to the valve lift switch can be canceled, as set out above. This relates for example to adjustment of the control variables of the throttle valve angle, the ignition angle or injection and cam phasing, which are quickly canceled.
The switch time Ts does not directly give the time at which the valve lift switch is effected but the biggest uncertainty factor, namely the switch time Ts, can be directly detected and differences can be compensated for.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 23 877 | May 2003 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6092495 | Hackett | Jul 2000 | A |
| Number | Date | Country |
|---|---|---|
| 02042107 | Feb 1990 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050005882 A1 | Jan 2005 | US |
