Method and control device for determining a characteristic viscosity variable of an oil

Abstract

In order for the viscosity of the engine oil to be determined as directly as possible, particularly in the case of a motor vehicle with hydraulic control of the gas exchange valves, provision is made for a time period which a hydraulic component, in particular a solenoid valve, requires to move from a first position to a second position to be used as a measure of the viscosity. In particular, an electrical control signal for the solenoid valve is evaluated in the process. An additional sensor arrangement is not required. The determined viscosity is preferably actively used for controlling the gas exchange valves.

1 - 13 . (canceled) 
     
     
         14 . A method for determining a characteristic viscosity variable of a hydraulic liquid in a motor vehicle having gas exchange valves and a hydraulic control system with a hydraulic component for hydraulically controlling the gas exchange valves, the method comprising the steps of:
 adjusting the hydraulic component from a first position to a second position by means of a control signal;   determining a time period which the hydraulic component requires for changeover from the first position to the second position; and   using the determined time period determined to measure the characteristic viscosity variable   
     
     
         15 . The method according to  claim 14 , wherein the hydraulic liquid is engine oil. 
     
     
         16 . The method according to  claim 14 , wherein the hydraulic component is an electrically controllable switching valve. 
     
     
         17 . The method according to claim  6 , wherein the electrically controllable switching valve is a solenoid valve. 
     
     
         18 . The method according to  claim 16 , wherein the switching valve is supplied with a control signal and the control signal is evaluated to determine the time period. 
     
     
         19 . The method according to  claim 18 , wherein the control signal is a switching valve. 
     
     
         20 . The method according to  claim 19 , wherein a switching time of the switching valve between the control signal and an end position of the switching valve is used as the time period. 
     
     
         21 . The method according to  claim 14 , wherein there is a linear correlation between the viscosity of the hydraulic liquid and the time period. 
     
     
         22 . The method according to  claim 21 , wherein the time period is linked directly to the viscosity such that the time period and the viscosity have a linear relationship and individual measurement points of the time period and viscosity with respect to each other can be connected by a regression line, which is determined by means of linear regression. 
     
     
         23 . The method according to  claim 14 , wherein the time period is repeatedly determined at a specific temperature of the hydraulic liquid and a check for a change is made. 
     
     
         24 . The method according to  claim 23 , wherein a conclusion can be drawn about aging of the hydraulic component and/or about aging of the hydraulic liquid at a specific operating point based on the time period. 
     
     
         25 . The method according to  claim 24 , wherein the aging of the hydraulic component is taken into consideration when determining the characteristic viscosity variable. 
     
     
         26 . The method according to  claim 15 , wherein the aging of the hydraulic component is derived from the time period at a high temperature of the oil at a temperature of greater than 80° C. 
     
     
         27 . The method according to  claim 24 , wherein an association between the time period and the viscosity of the hydraulic liquid is made by a regression line, which is determined by means of linear regression, and a shift in the regression line in relation to an unaged state of the hydraulic liquid is used as a measure of aging. 
     
     
         28 . The method according to  claim 14 , wherein the determined characteristic viscosity variable is evaluated and used selectively or in combination for:
 determining a measure of an oil quality;   identifying impermissible engine oils;   establishing an oil change interval;   diagnosing the hydraulic component; and   valve control.   
     
     
         29 . A control device for determining a characteristic viscosity variable of an engine oil in a motor vehicle having a gas exchange valves with the gas exchange valves being hydraulic controlled by a hydraulic component being adjusted from a first position to a second position with by means of a control signal,
 wherien the hydraulic component requires a measurement of a time period for changeover from the first position to the second position and the time period is used as a measure of the characteristic viscosity variable.