Fluid-working machine and operating method

Abstract

A fluid-working machine has a plurality of working chambers, e.g., cylinders, of cyclically changing volume, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber to each manifold, and electronic sequencing means for operating said valves in timed relationship with the changing volume of each chamber, wherein the electronic sequencing means is arranged to operate the valves of each chamber in one of an idling mode, a partial mode in which only part of the usable volume of the chamber is used, and a full mode in which all of the usable volume of the chamber is used, and the electronic sequencing means is arranged to select the mode of each chamber on successive cycles so as to infinitely vary the time averaged effective flow rate of fluid through the machine.

1 - 15 . (canceled) 
     
     
         16 . A method of operating a fluid-working machine having a plurality of working chambers of cyclically changing volume, said working chambers comprising cylinders in which pistons are arranged to reciprocate, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber of said working chambers to each manifold, the method comprising:
 operating the valves of at least one of said working chambers in a partial motoring mode in which only part of the usable volume of the one working chamber is used.   
     
     
         17 . The method according to  claim 16 , wherein the valve linking said one of the working chambers to the low-pressure manifold is closed before top dead centre and the valve linking said one of the working chambers to the high-pressure manifold is opened after top dead centre. 
     
     
         18 . The method according to  claim 17 , wherein the valve linking said one of the working chambers to the high-pressure manifold is closed after the induction of a fraction of the working chamber volume to thereby cause only part of the usable volume of the one working chamber to be used. 
     
     
         19 . A method of operating a fluid-working machine having a plurality of working chambers of cyclically changing volume, said working chambers comprising cylinders in which pistons are arranged to reciprocate, a high-pressure fluid manifold and a low-pressure fluid manifold, at least one valve linking each working chamber of said working chambers to each manifold, the method comprising:
 operating the valves of at least one of said working chambers in a partial pumping mode in which only part of the usable volume of the one working chamber is used, wherein after bottom dead centre the valve linking the cylinder to the low-pressure manifold is initially open while the valve linking the cylinder to the high-pressure manifold is closed and wherein, later in the stroke, the valve linking the cylinder to the low-pressure manifold is closed and the valve linking the cylinder to the high-pressure manifold is opened.   
     
     
         20 . The method according to  claim 19 , wherein the valve linking said one of the working chambers to the low-pressure manifold is closed in advance of top dead centre to thereby determine the fraction of working chamber volume pumped into the high-pressure manifold. 
     
     
         21 . The method according to  claim 19 , wherein in the partial pumping mode, valve actuations are delayed almost to an end of a stroke such that a rate of change of working chamber volume will be at an acceptably low level to permit valve actuation. 
     
     
         22 . A machine comprising: a plurality of working chambers of cyclically changing volume; a high-pressure fluid manifold; a low-pressure fluid manifold; at least one valve linking each working chamber to each manifold; and a controller having a configuration to: determine a mode of each chamber on successive cycles of changing working chamber volume so as to vary the time averaged effective flow rate of fluid through the machine according to a demand level, wherein the controller is configured to operate the valves of at least one of said working chambers in a partial motoring mode in which only part of the usable volume of the one working chamber is used. 
     
     
         23 . A machine according to  claim 22 , wherein the controller is configured to close the valve linking said one of the working chambers to the low-pressure manifold before top dead centre and to open the valve linking said one of the working chambers to the high-pressure manifold after top dead centre. 
     
     
         24 . A machine according to  claim 22 , wherein the controller is configured to close the valve linking said one of the working chambers to the high-pressure manifold after the induction of a fraction of the working chamber volume to thereby cause only part of the usable volume of the one working chamber to be used. 
     
     
         25 . A machine according to  claim 24 , wherein in the partial motoring mode, the controller delays the valve actuations almost to an end of a stroke such that a rate of change of working chamber volume will be at an acceptably low level to permit valve actuation. 
     
     
         26 . A machine comprising: a plurality of working chambers of cyclically changing volume; a high-pressure fluid manifold; a low-pressure fluid manifold; at least one valve linking each working chamber to each manifold; and a controller having a configuration to: determine a mode of each chamber on successive cycles of changing working chamber volume so as to vary the time averaged effective flow rate of fluid through the machine according to a demand level, and to operate the valves of at least one of the said working chambers in a partial pumping mode in which only part of the usable volume of the one working chamber is used, wherein after bottom dead centre the valve linking the cylinder to the low-pressure manifold is initially open while the valve linking the cylinder to the high-pressure manifold is closed and wherein, later in the stroke, the valve linking the cylinder to the low-pressure manifold is closed and the valve linking the cylinder to the high-pressure manifold is opened. 
     
     
         27 . A machine according to  claim 26 , wherein the controller is configured to close said valve linking said one of the working chambers to the low-pressure manifold in advance of top dead centre to thereby determine the fraction of working chamber volume pumped into the high-pressure manifold. 
     
     
         28 . A machine according to  claim 26 , wherein in the partial pumping mode, the controller delays valve actuations almost to an end of a stroke such that a rate of change of working chamber volume will be at an acceptably low level to permit valve actuation. 
     
     
         29 . A machine comprising: a plurality of working chambers of cyclically changing volume; a high-pressure fluid manifold; a low-pressure fluid manifold; at least one valve linking each working chamber to each manifold; and a controller having a configuration to: determine a mode of each chamber on successive cycles of changing working chamber volume so as to vary the time averaged effective flow rate of fluid through the machine according to a demand level, and operate the valves of each of the chambers to select the determined mode in accordance with an operation sequence which, in the successive cycles of changing working chamber volume, intersperses modes including at least (i) partial stroke modes in which only part of the usable volume of the working chamber is used, and (ii) full stroke modes in which all of the usable volume of the working chamber is used. 
     
     
         30 . A machine according to  claim 29 , wherein the said partial stroke modes are partial stroke pumping modes and the said full stroke modes are full stroke pumping modes. 
     
     
         31 . A machine according to  claim 29 , wherein the said partial stroke modes are partial stroke motoring modes and the said full stroke modes are full stroke motoring modes. 
     
     
         32 . A machine according to  claim 29 , wherein the demand level is varied in used. 
     
     
         33 . A machine according to  claim 29 , wherein the sequence of modes of operation is tailored for one or more of the smoothest flow result, the most seamless change in audible noise, minimal pressure ripple, and optimum actuator motion.