Camshaft adjuster

Abstract

A camshaft adjuster for relative angle adjustment of a camshaft with respect to a driving crankshaft, having a hydraulically operable adjustment apparatus with chambers into which and from which a hydraulic fluid can be supplied and carried away alternately for angle adjustment of the chamber-specific pressure-medium channels, and having a control valve via which the hydraulic fluid, which is supplied via a pump, can be supplied to the pressure-medium channels and can be carried away from the pressure-medium channels into a tank, with operating connections A and B, which lead to the pressure-medium channels, a pressure connection P which can be coupled to the pump, and an outlet connection T which can be coupled to the tank being provided on the valve body of the control valve, which operating connections A and B can be selectively coupled to the pressure connection P or to the outlet connection T, depending on the angle adjustment required, via a valve piston which can be moved in a controlled manner via a decoupled pulling or pushing magnet which is arranged externally with respect to the camshaft adjuster, in which case the fluid distribution area in the control valve ( 1, 20, 26, 34 ) is designed in such a manner that the hydraulic fluid acts on surfaces of the valve piston ( 4, 22, 28, 36 ) which point essentially in mutually opposite directions, so that local forces (F p1 , F p2 ), which are essentially in opposite directions to one another, act on the valve piston ( 4, 22, 28, 36 ).

1 . A camshaft adjuster for relative angle adjustment of a camshaft with respect to a driving crankshaft, comprising: a hydraulically operable adjustment apparatus with chambers into which and from which a hydraulic fluid can be supplied and carried away alternately for angle adjustment of the chamber-specific pressure-medium channels, and having a control valve via which the hydraulic fluid, which is supplied via a pump, can be supplied to the pressure-medium channels and can be carried away from the pressure-medium channels into a tank, with operating connections A and B, which lead to the pressure-medium channels, a pressure connection P which can be coupled to the pump, and an outlet connection T which can be coupled to the tank being provided on the valve body of the control valve, which operating connections A and B can be selectively coupled to the pressure connection P or to the outlet connection T, depending on the angle adjustment required, via a valve piston which can be moved in a controlled manner via a decoupled pulling or pushing magnet which is arranged externally with respect to the camshaft adjuster, wherein the fluid distribution area in the control valve is designed in such a manner that the hydraulic fluid acts on surfaces of the valve piston which point essentially in mutually opposite directions, so that local forces (F p1 , F p2 ), which are essentially in opposite directions to one another, act on the valve piston.  
   
   
       2 . The camshaft adjuster as claimed in  claim 1 , wherein the mutually opposite forces (F p1 , F p2 ) are essentially of equal magnitude.  
   
   
       3 . The camshaft adjuster as claimed in  claim 1 , wherein the pressure connection P is at an angle, preferable at right angles, to the valve axis and opens into an annular channel which is formed between the valve piston and the valve body, can be connected to the operating connection A as a function of position, and leads into the hollow-cylindrical valve piston, which is closed at both ends and whose cavity can be connected as a function of position to the operating connection B, with pressure being applied to the end cavity surfaces via the hydraulic fluid.  
   
   
       4 . The camshaft adjuster as claimed in  claim 3 , wherein the two operating connections A, B can be connected as a function of position to the outlet connection T, which is at right angles to the valve longitudinal axis, via an annular channel which is formed between the valve piston and the valve body.  
   
   
       5 . The camshaft adjuster as claimed in  claim 3 , wherein the pressure connection P, the outlet connection T and the operating connections A and B are arranged running at right angles to the valve longitudinal axis and in the sequence B-T-A-P, or A-T-B-P.  
   
   
       6 . The camshaft adjuster as claimed in  claim 1 , wherein the pressure connection P is at an angle, preferably at right angles, to the valve longitudinal axis and opens into an annular space which is formed between the valve piston and the valve body and can be connected as a function of position to the operating connection A or B, in which case the operating connections A, B can be connected as a function of position via connecting openings to the cavity in the hollow-cylindrical valve piston, and the cavity leads to the outlet connection T.  
   
   
       7 . The camshaft adjuster as claimed in  claim 6 , wherein the pressure connection P and the operating connections A and B are arranged such that they run at right angles to the valve longitudinal axis and in the sequence A-P-B.  
   
   
       8 . The camshaft adjuster as claimed in  claim 1 , wherein the pressure connection P is on the valve longitudinal axis and opens via guide channels into an annular space which is formed between the valve piston and the valve body and can be connected as a function of position to the operating connection A or B, in which case the operating connections A, B can be connected as a function of position via connecting openings to the cavity in the hollow-cylindrical valve piston and the cavity leads to the outlet connection T.  
   
   
       9 . The camshaft adjuster as claimed in  claim 1 , wherein the pressure connection P runs aligned with the valve longitudinal axis and opens into the hollow-cylindrical valve piston on which radial openings are provided through which the hydraulic fluid enters the annular space which is formed between the valve piston and the valve body and is bounded by the end face of the valve piston.  
   
   
       10 . The camshaft adjuster as claimed in  claim 1 , wherein the control valve is integrated centrally in the adjustment apparatus, and rotates with it.