# US 10,309,390 B2 · Control unit for hydraulic variable displacement pumps and variable displacement pump with a control unit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,309,390 B2 - Document ID: US10309390B2 - Status: Granted - Kind: B2 - Application number: 14/452,112 - Filed: 2014-08-05 - Published: 2015-02-19 - Granted: 2019-06-04 - Earliest claimed: 2013-08-19 - Assignees: Danfoss Power Solutions Inc. - Applicants: Danfoss Power Solutions Inc. - Inventors: Peter Zavadinka; Stanislov Smolka; Pavol Sedo - Web page: https://patentgrep.com/patent/US10309390B2 ## CPC - F04B 49/08: Regulating by delivery pressure - F04B 1/324: by changing the inclination of the swash plate - F04B 49/002: {Hydraulic systems to change the pump delivery} - F04B 49/12: by varying the length of stroke of the working members - Y10T 137/86622: Motor-operated - F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Control device for hydraulic variable displacement pumps operated in an open hydraulic circuit and adjustable in their displacement volume by means of a servo control device. The control device comprises a control piston with two control edges to which pressure can be applied by means of pressurized pressure fluid from a variable displacement pump, the control piston being mounted in a housing so that it shifts longitudinally. The housing of the control piston comprises an inlet for the connection of a high pressure line of a variable displacement pump, an outlet which can be connected to a tank and a servo connection which can be linked to a servo cylinder, whereby a link between the inlet and the servo connection can be made via a first control edge. It is possible to create a link between the servo connection and the outlet via a second control edge. ## Claims ### Claim 1 A control device (20) for a hydraulic variable displacement pump (1) which is operated in an open hydraulic circuit and which is adjustable by a servo piston (4) configured to shift inside a servo cylinder (5), to which servo piston (4) pressure is applied by pressurized pressure fluid via the control device (20), the control device (20) comprising: a housing (11) of a control piston (6), an inlet (26) for the connection of a high pressure line of the variable displacement pump (1), an outlet (18) which is configured to connect to a tank (19) and a servo connection (27) configured to link to the servo cylinder (5), the control piston (6) having a first control edge (38) and a second control edge (39) and being mounted in the housing (11) so that the control piston (6) shifts longitudinally from a first end to a second end, whereby the control piston (6) is configured to create a connection between the inlet (26) and the servo connection (27) via the first control edge (38) and the control piston is configured to create a connection between the servo connection (27) and the outlet (18) via the second control edge (3), the control piston (6) is preloaded by a first spring (7) at the first end (28) which is adjacent to the outlet (26), at the second end (29) of the control piston (6) adjacent to the outlet (18) a second spring (8) engages the control piston (6), which counteracts a hydraulic force and the preload of the first spring (7), a power-adjustable actuator (9) at one of the two ends (28 or 29) of the control piston (6) that engages the control piston (6) by a tractive or a compressive force transmitted to another of the two ends (28 or 29) in parallel with the respective spring (7 or 8) of the control piston (6) such that the force of the actuator (9) is applied to the control piston (6) toward the another of the two ends (28 or 29), whereby pressure can only be applied to the control piston (6) with the pressure fluid under pressure from the variable displacement pump (1) to generate the hydraulic force toward the direction of the another of the two ends (28 or 29) of the control piston (6), and a spring guide (13, 14) configured to provide fluid communication between a longitudinal bore (36) of the control piston (6) and a first spring chamber (21) in one position of the control piston (6). ### Claim 2 (depends on 1) The control device (20) for the hydraulic variable adjustment pump (1) according to claim 1, characterized in that the control piston (6) is stepped and the pressurized pressure fluid of the variable displacement pump (1) acts on two diameters of differing sizes, whereby the diameter acting in the direction of the outlet (18) is larger. ### Claim 3 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in that the actuator (9) is an electric solenoid to which electric current is applied at adjustable levels by an electronic control unit (31). ### Claim 4 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in that the spring force of the first spring (7) or second spring (8) is set by a setting device (12). ### Claim 5 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in that the actuator (9) and the spring (7 or 8) positioned at the one of the two ends of the control piston (6) are arranged in series. ### Claim 6 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, the spring guide (13, 14) is configured to transmit the spring force to the one end of the two ends (28 or 29) of the control piston (6). ### Claim 7 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in the first spring (7) is mounted in the first spring chamber (21) and the second spring (8) is mounted in a second spring chamber (21), each of the first spring chamber (21) and the second spring chamber (21) are respectively configured so as to be adjacent to a respective one of the two ends of the control piston (6) and are connected to each other via the longitudinal bore (36) in the control piston (6). ### Claim 8 (depends on 7) The control device (20) for the hydraulic variable displacement pump (1) according to claim 7, characterized in that one of the two spring chambers (21) is connected to the outlet (18) by means of a channel (25) in the housing (11). ### Claim 9 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, wherein the pressurized pressure fluid from the variable displacement pump (1) is applied to the servo piston (4) via the control device (20)) in order to set a supply pressure. ### Claim 10 (depends on 9) The control device (20) for the hydraulic variable displacement pump (1) according to claim 9, characterized in that the variable displacement pump (1) is configured as an axial piston machine of the swash plate or bent axis design. ### Claim 11 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, further comprising the control piston (6) having two circumferential grooves (24) whose longitudinal limits form the first control edge (38) and the second control edge (39) respectively. ### Claim 12 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, wherein the longitudinal bore (36) passes through an axial length of the control piston. ### Claim 13 (depends on 12) The control device (20) for the hydraulic variable displacement pump (1) according to claim 12, wherein the longitudinal bore (36) is configured to balance pressure between the first end (28) and the second end (29) of the piston (6). ### Claim 14 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in that the actuator (9) is positioned on the opposite side of the pressure applied by the pressurized pressure fluid. ### Claim 15 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1, characterized in the actuator (9) having a tappet (30) that passes through the adjacent one of the two springs (7 or 8). ### Claim 16 (depends on 15) The control device (20) for the hydraulic variable displacement pump (1) according to claim 15, characterized in that the tappet (30) is configured to exert the force of the actuator at the spring guide (14). ### Claim 17 (depends on 1) The control device (20) for the hydraulic variable displacement pump (1) according to claim 1 wherein the force of the adjacent one of the two springs (7 or 8) is applied independently to the control piston (6) of the force of the actuator (9) throughout actuation of the actuator (9). ### Claim 18 A control device (20) for a hydraulic variable displacement pump (1) which is operated in an open hydraulic circuit and which is adjustable by means of a servo piston (4) configured to shift inside a servo cylinder (5), to which servo piston (4) pressure is applied by means of pressurized pressure fluid via the control device (20), the control device (20) comprising: a housing (11) of a control piston (6), an inlet (26) for the connection of a high pressure line of the variable displacement pump (1), an outlet (18) which is configured to connect to a tank (19) and a servo connection (27) configured to link to the servo cylinder (5), the control piston (6) having a first control edge (38) and a second control edge (39), whereby the control piston (6) is configured to create a connection between the inlet (26) and the servo connection (27) via the first control edge (38) and the control piston is configured to create a connection between the servo connection (27) and the outlet (18) via the second control edge (3), the control piston (6) is preloaded by a first spring (7) at a proximal end (28) which is adjacent to the outlet (26), at a distal end (29) of the control piston (6) adjacent to the outlet (18) a second spring (8) engages which counteracts a hydraulic force and the preload of the first spring (7), a power-adjustable actuator (9) at the proximal end (28) of the control piston (6) engages with a tractive or a compressive force is transmitted to the distal end (29) in parallel with the first spring (7) of the control piston (6) such that the force of the actuator (9) is applied to the control piston (6) toward the distal end (29) independently of the force of the first spring (7) towards the respective the distal end (29), whereby pressure can only be applied to the control piston (6) with the pressure fluid under pressure from the variable displacement pump (1) to generate the hydraulic force in the direction of the distal end (29) of the control piston (6), a spring guide (13, 14) configured to provide fluid communication between a longitudinal bore (36) of the control piston (6) and a spring chamber (21) in one position of the control piston (6). ### Claim 19 A control device (20) for a hydraulic variable displacement pump (1) which is operated in an open hydraulic circuit and which is adjustable by a servo piston (4) configured to shift inside a servo cylinder (5), to which servo piston (4) pressure is applied by pressurized pressure fluid via the control device (20), the control device (20) comprising: a housing (11) of a control piston (6), an inlet (26) for the connection of a high pressure line of the variable displacement pump (1), an outlet (18) which is configured to connect to a tank (19) and a servo connection (27) configured to link to the servo cylinder (5), the control piston (6) having a first control edge (38) and a second control edge (39), whereby the control piston (6) is configured to create a connection between the inlet (26) and the servo connection (27) via the first control edge (38) and the control piston is configured to create a connection between the servo connection (27) and the outlet (18) via the second control edge (3), the control piston (6) is preloaded by a second spring (8) at a distal end (29) which is adjacent to the inlet (28), at a proximal end (28) of the control piston (6) adjacent to the outlet (26) a first spring (7) engages which counteracts a hydraulic force and the preload of the second spring (8), a power-adjustable actuator (9) at the distal end (29) of the control piston (6) engages with a tractive or a compressive force is transmitted to the proximal end (28) in parallel with the second spring (8) of the control piston (6) such that the force of the actuator (9) is applied to the control piston (6) toward the proximal end (28) independently of the force of the second spring (8) towards the respective proximal end (28), whereby pressure can only be applied to the control piston (6) with the pressure fluid under pressure from the variable displacement pump (1) to generate the hydraulic force in the direction of the proximal end (28) of the control piston (6), a spring guide (13, 14) configured to provide fluid communication between a longitudinal bore (36) of the control piston (6) and a spring chamber (21) in one position of the control piston (6).