Camshaft adjuster having a chamber short-circuiting, pressure-controlled control unit

Abstract

A vane-type camshaft adjuster ( 1 ) including a rotor ( 2 ) which has radially projecting vanes ( 3 ) and forms vane cells ( 5 ) along with a stator ( 4 ) rotatably accommodating the rotor ( 2 ), each vane cell ( 5 ) being subdividable by a vane ( 3 ) into two adjustable chambers provided for holding hydraulic fluid; a hydraulic fluid-controlling device ( 12 ) for conducting hydraulic fluid is disposed and/or connected between the chambers ( 6, 7 ) in such a way that a drop in pressure in the chambers ( 6, 7 ) caused or reinforced by camshaft switching moments occurring during operation is used to open the hydraulic fluid-controlling device ( 12 ) such that fluid flows therethrough.

What is claimed is: 
     
       1. A vane-type camshaft adjuster comprising:
 a rotor having radially projecting vanes, the rotor, together with a stator rotatably accommodating the rotor, forming vane cells, each vane cell divided by one of the vanes into a first adjustable chamber and a second adjustable chamber provided for accommodating hydraulic fluid, 
 a hydraulic fluid control device entirely inside one of the vanes for conducting the hydraulic fluid between the first and second adjustable chambers being situated in such a way that a pressure drop in each of the first and second chambers is induced or amplified by camshaft alternating torques occurring during operation and is used to open the hydraulic fluid control device so that the hydraulic fluid flows therethrough, 
 wherein the hydraulic fluid control device is configured such that the hydraulic fluid flows from the second chamber through the hydraulic fluid control device to the first chamber when a pressure in the first chamber falls below a limit pressure, 
 wherein the limit pressure is a critical pressure at which air is sucked into the hydraulic fluid or at which the hydraulic fluid begins to degas. 
 
     
     
       2. The camshaft adjuster as recited in  claim 1  wherein the hydraulic fluid control device includes at least one bypass line closing device. 
     
     
       3. The camshaft adjuster as recited in  claim 2  wherein the at least one bypass line closing device includes a valve and a spring acting thereupon. 
     
     
       4. The camshaft adjuster as recited in  claim 3  wherein the spring pretensions the valve into a position in which the hydraulic fluid flow is prevented. 
     
     
       5. The camshaft adjuster as recited in  claim 2  wherein the at least one bypass line closing device is preset in such a way that, when a pressure in the first chamber falls below the limit pressure, a switching position of the at least one bypass line closing device is forced, the hydraulic fluid entering the first chamber from the second chamber through a bypass line in the switching position. 
     
     
       6. The camshaft adjuster as recited in  claim 5  wherein the at least one bypass line closing device includes a valve and a spring acting thereupon, the spring configured such that the valve opens when the pressure falls below the limit pressure. 
     
     
       7. The camshaft adjuster as recited in  claim 6  wherein the at least one bypass line closing device includes a pilot line establishing a pressure-transmitting connection between the first chamber and a closing element, the spring, in a basic position, forcing the closing element into the bypass line connecting the two chambers in a hydraulic fluid-suppressing manner, and the bypass line being open in an activating position, when the pressure in the first chamber reaches or falls below the limit pressure. 
     
     
       8. The camshaft adjuster as recited in  claim 1  wherein the hydraulic fluid control device includes two bypass line closing devices. 
     
     
       9. The camshaft adjuster as recited in  claim 8  wherein the two bypass line closing devices are situated in parallel to each other in a fluid-conductible manner. 
     
     
       10. The camshaft adjuster as recited in  claim 1  wherein two pistons movable toward and away from each other are situated in a channel or bore connecting the first and second chambers, the two pistons being situated in such a way that the two pistons are activated only by a pilot line assigned to the two pistons. 
     
     
       11. The camshaft adjuster as recited in  claim 1  wherein the hydraulic fluid control device is configured such that the hydraulic fluid flows from the first chamber through the hydraulic fluid control device to the second chamber when a pressure in the second chamber falls below the limit pressure. 
     
     
       12. The camshaft adjuster as recited in  claim 1  wherein the hydraulic fluid control device includes a first spring configured to move to allow the hydraulic fluid to flow through a first bypass line from the first chamber to the second chamber when the pressure in the second chamber falls below the limit pressure; and a second spring configured to move to allow the hydraulic fluid to flow through a second bypass line from the second chamber to the first chamber when the pressure in the first chamber falls below the limit pressure. 
     
     
       13. A vane-type camshaft adjuster comprising:
 a rotor having radially projecting vanes, the rotor, together with a stator rotatably accommodating the rotor, forming vane cells, each vane cell divided by one of the vanes into a first adjustable chamber and a second adjustable chamber provided for accommodating hydraulic fluid, 
 a hydraulic fluid control device inside one of the vanes for conducting the hydraulic fluid between the first and second adjustable chambers being situated in such a way that a pressure drop in each of the first and second chambers is induced or amplified by camshaft alternating torques occurring during operation and is used to open the hydraulic fluid control device so that the hydraulic fluid flows therethrough, 
 the hydraulic fluid control device being configured such that the hydraulic fluid flows from the first chamber through the hydraulic fluid control device to the second chamber when a pressure in the second chamber falls below a limit pressure, 
 the hydraulic fluid control device being configured such that the hydraulic fluid flows from the second chamber through the hydraulic fluid control device to the first chamber when a pressure in the first chamber falls below the limit pressure, 
 wherein the limit pressure is a critical pressure at which air is sucked into the hydraulic fluid or at which the hydraulic fluid begins to degas. 
 
     
     
       14. The camshaft adjuster as recited in  claim 13  wherein the hydraulic fluid control device includes a first spring is configured to move to allow the hydraulic fluid to flow through a first bypass line from the first chamber to the second chamber when the pressure in the second chamber falls below the limit pressure. 
     
     
       15. The camshaft adjuster as recited in  claim 13  wherein the hydraulic fluid control device includes a second spring is configured to move to allow the hydraulic fluid to flow through a second bypass line from the second chamber to the first chamber when the pressure in the first chamber falls below the limit pressure. 
     
     
       16. A vane-type camshaft adjuster comprising:
 a rotor having radially projecting vanes, the rotor, together with a stator rotatably accommodating the rotor, forming vane cells, each vane cell divided by a vane into two adjustable chambers provided for accommodating hydraulic fluid, 
 a hydraulic fluid control device for conducting the hydraulic fluid between the two chambers being situated in such a way that a pressure drop in the two chambers is induced or amplified by camshaft alternating torques occurring during operation and is used to open the hydraulic fluid control device so that the hydraulic fluid flows therethrough, and 
 
       wherein two pistons movable toward and way from each other are situated in a channel or bore connecting the two chambers, the two pistons being situated in such a way that the two pistons are activated only by a pilot line assigned to each of the two pistons.