Valve timing controller

Abstract

A valve timing controller has a case which defines a fluid chamber therein. A magnetic viscosity fluid is enclosed in the fluid chamber. The magnetic viscosity fluid including magnetic particles and its viscosity varies according to a magnetic field applied thereto. A coil and a control circuit applies magnetic field to the magnetic viscosity fluid to variably control a viscosity thereof. A brake rotor is rotatably accommodated in the fluid chamber and receives a brake torque from the magnetic viscosity fluid according to the viscosity thereof. A phase adjusting mechanism is connected to the brake rotor for adjusting a relative rotational phase between the crankshaft and the camshaft according to the brake torque. When it is estimated that the engine will be started, the coil is energized to generated heat in the magnetic viscosity fluid.

1 . A valve timing controller which adjusts a valve timing of a valve opened/closed by a torque transmitted from a crankshaft to a camshaft of an internal combustion engine, the valve timing controller comprising:
 a case defining a fluid chamber therein;   a magnetic viscosity fluid enclosed in the fluid chamber, the magnetic viscosity fluid including magnetic particles, the magnetic viscosity fluid having a viscosity which varies according to a magnetic field applied thereto;   a viscosity control means for variably controlling a viscosity of the magnetic viscosity fluid by applying a magnetic field to the magnetic viscosity fluid;   a brake rotor rotatably accommodated in the fluid chamber and receiving a brake torque from the magnetic viscosity fluid according to the viscosity thereof;   a phase adjusting mechanism connected to the brake rotor for adjusting a relative rotational phase between the crankshaft and the camshaft of the internal combustion engine according to the brake torque which is inputted into the brake rotor; and   a heating control means for generating a heat in the magnetic viscosity fluid when it is estimated that the internal combustion engine will be started.   
     
     
         2 . A valve timing controller according to  claim 1 , wherein
 the heating control means starts a heating of the magnetic viscosity fluid to generate heat therein when it is estimated that the internal combustion engine will be started and it is detected that a temperature of the magnetic viscosity fluid is lower than a lower-limit temperature which is required to vary the relative rotational phase.   
     
     
         3 . A valve timing controller according to  claim 1 , wherein
 the heating control means includes a coil disposed in the case, and   when the coil is energized, a magnetic field of which intensity is variable is applied to the magnetic viscosity fluid, whereby the magnetic viscosity fluid generates the heat therein.   
     
     
         4 . A valve timing controller according to  claim 1 , wherein
 the heating control means includes a coil disposed in the case, and when the coil is energized, the coil generates heat which is transmitted to the magnetic viscosity fluid, whereby the magnetic viscosity fluid is heated.   
     
     
         5 . A valve timing controller according to  claim 3 , wherein
 the heating control means energizes the coil to generate a magnetic field which is applied to the magnetic viscosity fluid, whereby the viscosity of the magnetic viscosity fluid is variably controlled.   
     
     
         6 . A valve timing controller according to  claim 5 , wherein
 the heating control means sets a first variable frequency of the magnetic field when it is estimated that the engine will be started, and   the heating control means sets a second variable frequency of the magnetic field which is higher than the first variable frequency when the engine is started.   
     
     
         7 . A valve timing controller according to  claim 5 , wherein
 the heating control means sets a first electric power supplied to the coil when it is estimated that the engine will be started, and   the heating control means sets a second electric power supplied to the coil, which is lower than the first electric power, when the engine is started.   
     
     
         8 . A valve timing controller according to  claim 3 , wherein
 the heating control means further includes a second coil, and   the viscosity control means energizes the second coil to generate a magnetic field which is applied to the magnetic viscosity fluid, whereby the viscosity of the magnetic viscosity fluid is variably controlled.   
     
     
         9 . A valve timing controller according to  claim 8 , wherein
 the viscosity control means controls the viscosity of the magnetic viscosity fluid in order to vary the relative rotational phase when the engine is started, and   the heating control means terminates heating of the magnetic viscosity fluid when a variation in the relative rotational phase is detected.   
     
     
         10 . A valve timing controller according to  claim 1 , wherein
 the heating control means terminates heating of the magnetic viscosity fluid when it is detected that a temperature of the magnetic viscosity fluid exceeds a lower-limit temperature which is required to vary the relative rotational phase.   
     
     
         11 . A valve timing controller according to  claim 1 , wherein
 the heating control means terminates heating of the magnetic viscosity fluid when a specified heating period has elapsed, which is required to increase the temperature of the magnetic viscosity fluid higher than a lower-limit temperature which is required to vary the relative rotational phase.   
     
     
         12 . A valve timing controller according to  claim 1 , wherein
 the heating control means terminates heating of the magnetic viscosity fluid when the internal combustion engine is started.