Actuator system for a controlled coolant pump

Abstract

A coolant pump of an internal combustion engine, with a pump housing and a hollow shaft rotatably mounted therein. Coolant is delivered via an impeller wheel from a suction connection. The flow is controlled by a guide plate on the impeller wheel that is variably displaceable axially between two end positions. The guide plate is adjustable by a push rod actuator guided in the pump shaft. The actuator has a radial piston pump integrated within the coolant pump with an intake piston and a counterpiston guided in the pump shaft, that are inserted lying opposite one another and delimit a pressure space. The pistons are enclosed outside by a linearly displaceable control element guided in the pump housing. Adjustment of the control element takes place as a function of a rotary angle of the pump shaft via an actuator unit having an electrically operated actuating element and a linear freewheel.

1 . A coolant pump of an internal combustion engine, comprising a pump housing in which a pump shaft is mounted rotatably, the pump shaft is configured as a hollow shaft and has an associated impeller wheel connected on one end thereof which delivers a coolant as volumetric flow via a suction connection into a spiral channel, a guide plate on the impeller wheel to adjust a volumetric flow that is axially displaceable between two end positions in an infinitely variable manner and is connected in a rotationally rigid manner to a push rod that is guided in the pump shaft and is connected to an actuator system, the actuator system comprises a radial piston pump which is integrated within the coolant pump and includes a main or intake piston and a counterpiston, which are guided in a through hole of the pump shaft, and are inserted so as to lie opposite one another, to delimit a pressure space, and are enclosed on an outside by a radially or linearly displaceable control element which is guided in a cutout in the pump housing, an adjustment of which takes place via an actuator unit which includes an electrically operated actuating element and a linear freewheel. 
     
     
         2 . The coolant pump as claimed in  claim 1 , wherein a clamped assembly of the linear freewheel of the actuator unit, which makes a self-locking action possible, comprises at least two clamping bodies which are inserted in a guide sleeve, are guided on an outside on a cutout of the pump housing and on an inside enclose a clamping cone which is assigned to the control element. 
     
     
         3 . The coolant pump as claimed in  claim 2 , wherein the clamping cone which tapers in a direction of the guide sleeve engages in regions into the guide sleeve and is enclosed by a compression spring which is inserted between the control element and the guide sleeve. 
     
     
         4 . The coolant pump as claimed in  claim 3 , wherein, for a powerless actuating element, the compression spring exerts an axial force which releases the clamped assembly of the linear freewheel and moves it into an initial position or a neutral position. 
     
     
         5 . The coolant pump as claimed in  claim 1 , wherein an electromagnet is provided as the actuating element for the actuator unit. 
     
     
         6 . The coolant pump as claimed in  claim 1 , wherein the actuator unit provides a range of force of ≧10 N for the actuating element, the compression spring has a range of force of from ≧1.2 N to ≦3 N, and the linear freewheel has a wedge angle α of ≦5.7° with a coefficient of friction μ of 0.1 in order to achieve a self-locking action. 
     
     
         7 . The coolant pump as claimed in  claim 1 , wherein an eccentricity (E) of the main piston and counterpiston which are offset by 180° with respect to one another and are guided on an inner contour of the control element can be influenced by the control element which is inserted in the pump housing such that it is sealed, fixed rotationally and displaceable radially in an infinitely variable manner. 
     
     
         8 . The coolant pump as claimed in  claim 1 , wherein a spring element is inserted between the main piston and the counterpiston of the radial piston pump, and the main piston includes an intake channel or an intake valve for entry of hydraulic fluid, and the hydraulic fluid exits into the pressure space via a one-way valve. 
     
     
         9 . The coolant pump as claimed in  claim 8 , wherein, in the actuation phase, a partial quantity of the hydraulic fluid is displaced, in the case of a pressure gradient, out of the pressure space via a closing valve of the pump shaft into a high pressure space, in which an actuating piston which is coupled to the push rod of the guide plate is loaded. 
     
     
         10 . The coolant pump as claimed in  claim 1 , wherein, as a failure safeguard for the actuator system, the push rod interacts with a failsafe device which comprises a spring element.