Control systems for a variable displacement pump

Claim 2

An automatic control device for a variable displacement fluid energy translating device having a rocker cam pivotally mounted in a rocker cam support for changing the displacement of the device, fluid motor means for pivoting the rocker cam including a first fluid motor member attached to the rocker cam and a second fluid motor member cooperative with the first fluid motor member to define first and second sealed fluid receiving chambers, a servo pump for supplying servo pressure fluid, manual control means for selectively supplying servo pressure fluid to said fluid motor to selectively position the rocker cam between a first position of maximum pump displacement in which said one port is the working port and the other port is the inlet port and a second position of maximum pump displacement in which said other port is the working port and said one port is the inlet port, and the improvement comprising automatic control means for overriding said manual control means including compensating means operable when working fluid exceeds a first predetermined pressure to supply working fluid to said fluid motor to reduce displacement of the device until the working fluid maintains the first predetermined pressure, a first relief valve responsive to working fluid pressure and servo fluid pressure to limit the pressure of the working fluid supplied to said fluid motor to a second predetermined pressure and a second relief valve responsive to inlet fluid pressure and modified servo fluid pressure to maintain and limit the fluid exhausted from said fluid motor to a third predetermined pressure.

Claim 3

The automatic control device recited in claim 1, including biasing means for positioning said second relief valve, the force of said biasing means being directly proportional to servo fluid pressure.

Claim 4

The automatic control device recited in claim 2, including a third relief valve for limiting the pressure of the servo fluid to a fourth predetermined pressure and bypassing servo fluid when it exceeds the fourth predetermined pressure, said second relief valve biasing means including differential area means having a first area and a seconD area, means for reducing the pressure of the servo fluid, first passage means interconnecting said servo pump and said first area to supply said servo fluid at reduced pressure to said first area to bias said second relief valve closed to thereby set the second relief valve at the third predetermined pressure, and second passage means connecting said fluid motor exhaust fluid to the second area to bias said second relief valve open and bypass exhaust fluid through said second relief valve when said exhaust fluid exceeds the third predetermined pressure.

Claim 5

The automatic control device recited in claim 3, wherein said servo pressure reducing means includes an orifice in said first passage means.

Claim 6

The automatic control device recited in claim 3, including replenishing means connected to the pump ports for making excess fluid available to the inlet port, third passage means connecting said third relief valve and said replenishing means to supply servo fluid by-passed through said third relief valve to said replenishing means, fourth passage means connecting the first relief valve and said replenishing means to supply working fluid by-passed through the first relief valve to said replenishing means, and fifth passage means connecting said second relief valve and said replenishing means to supply fluid by-passed through said second relief valve to said replenishing means.

Claim 7

The automatic control device recited in claim 5, including a fourth relief valve to limit the fluid in said replenishing means to a fifth predetermined pressure and fifth passage means connecting said fourth relief valve to said pump casing to bypass fluid thereto when fluid in said replenishing means exceeds the fifth predetermined pressure.

Claim 8

The automatic control device recited in claim 6, including fifth passage means connecting said casing with a reservoir, and a fifth relief valve in said fifth passage means to maintain the fluid in said casing at a sixth predetermined pressure so fluid in said casing can flow backwards through said fifth passage means, said fourth relief valve and said replenishing means to the inlet port of the pump when the pressure of replenishing fluid falls below case pressure.

Claim 9

The automatic control device recited in claim 3, wherein the first relief valve includes biasing means for positioning the first relief valve.

Claim 10

The automatic control device recited in claim 8, wherein the first relief valve biasing means includes a differential area means having a first area and a second area, and servo fluid is supplied to said first area to bias the first relief valve closed to thereby set the first relief valve at the second predetermined pressure.

Claim 11

The automatic control device recited in claim 9, including third passage means connecting said compensating means with said fluid motor and the second area to operate the fluid motor and bias said first relief valve open when working fluid bypasses said compensating means, the relationship between the first and second areas being such that the bypassed working fluid pressure is reduced to a desired level above servo fluid pressure.

Claim 12

The automatic control device recited in claim 10, including replenishing means for making excess fluid available to the inlet port, fourth passage means connecting the first relief valve and said replenishing means and the fluid bypassed through the first relief valve is supplied to said replenishing means, a fourth relief valve to limit the fluid in said replenishing means to a fifth predetermined pressure and fifth passage means interconnecting said fourth relief valve and said pump casing to bypass fluid thereto when fluid in said replenishing means exceeds the fifth predetermined pressure, sixth passage means connecting said casing with a reservoir, and a fifth relief valve in said sixth passage means to maintain the fluid in said casing at a sixth predetermined pressure so fluid in said casing can flow backwards through said fifth passage means, said fourth relief valve and said replenishing means to the inlet port of the pump when said replenishing fluid pressure falls below case pressure.

Claim 13

The automamtic control device recited in claim 1, wherein the compensating means includes a flow control orifice in the working fluid port and said compensating means being responsive to a pressure differential across the orifice corresponding to an excessive flowrate to supply working fluid to said fluid motor to reduce displacement of the device until the working fluid maintains a predetermined flowrate.

Claim 14

An automatic control device for a variable displacement fluid energy translating device having a rocker cam pivotally mounted in a rocker cam support for changing the displacement of the device, fluid motor means for pivoting the rocker cam including a first fluid motor member attached to the rocker cam, a second fluid motor member cooperative with the first fluid motor member to define first and second sealed fluid receiving chambers, a servo pump for supplying servo pressure fluid, manual control means for selectively supplying servo pressure fluid to said fluid motor to selectively position the rocker cam between a first position of maximum pump displacement in which said one port is the working port and a second position of maximum pump displacement in which said other port is the working port, the improvement comprising automatic control means for overriding said manual control means including compensating means operable when working fluid exceeds a predetermined pressure to bypass working fluid and supply working fluid to said fluid motor to reposition said rocker cam to reduce displacement of the device until the quantity of working fluid maintains the predetermined pressure, a relief valve having differential area means including a first area and a second area, first passage means interconnecting the servo pump and the first area to supply servo fluid to the first area to bias the relief valve closed, second passage means interconnecting the first area and a pump port, a check valve in the second passage means, pressure reducing means for reducing servo fluid pressure acting on the first area when servo fluid flows therethrough, third passage means connecting the compensating means and the second area, fourth passage means interconnecting the fluid motor means and the second area, the relief valve being operable alternatively between a first mode in which the port is the working port and working fluid biases the check valve closed to prevent servo fluid flow through the pressure reducing means whereby servo fluid pressure acts on the first area and bypassed working fluid at greater than servo fluid pressure acts on the second area to bias the relief valve open and provide fluid at greater than servo fluid pressure to said fluid motor and a second mode in which the port is an inlet port and servo fluid flows through the pressure reducing means and the check valve whereby servo fluid at reduced pressure acts on the first area and fluid discharged from the fluid motor acts on the second area to bias the relief valve open.

Claim 15

An automatic control device for a variable displacement fluid energy translating device having a rocker cam pivotally mounted in a rocker cam support for changing the displacement of the device, fluid motor means for pivoting the rocker cam including a first fluid motor member attached to the rocker cam, a second fluid motor member cooperative with the first fluid motor member to define first and second sealed fluid receiving chambers, a servo pump for supplying servo pressure fluid, manual control means for selectively supplying servo pressure fluid to said fluid motor to selectively position the rocker cam between a first position of maximum pump displacement in which said one port is the working port and a second position of maximum pump displacement in which said other port is the working port, the improvement comprising automatic control means for overriding said manual control means including compensating means operable when working fluid exceeds a predetermined pressure to bypass working fluid and supply working fluid to said fluid motor to reposition said rocker cam to reduce displacement of the device until the quantity of working fluid maintains the predetermined pressure, a relief valve having differential area means including a first area and a second area, first passage means interconnecting the servo pump and the first area to supply servo fluid to the first area to bias the relief valve closed, second passage means interconnecting the first area and a pump port, a check valve in the second passage means, pressure reducing means for reducing servo fluid pressure acting on the first area when servo fluid flows therethrough, third passage means connecting the compensating means and the second area, fourth passage means interconnecting the fluid motor means and the second area, the relief valve being operable alternatively between a first mode in which the port is the working port and working fluid biases the check valve closed to prevent servo fluid flow through the pressure reducing means whereby servo fluid pressure acts on the first area and bypassed working fluid at greater than servo fluid pressure acts on the second area to bias the relief valve open and provide fluid at greater than servo fluid pressure to said fluid motor and a second mode in which the port is an inlet port and servo fluid flows through the pressure reducing means and the check valve whereby servo fluid at reduced pressure acts on the first area and fluid discharged from the fluid motor acts on the second area to bias the relief valve open.

Claim 16

The automatic control device recited in claim 13, wherein said pressure reducing means includes a first orifice in the first passage and a second orifice in the second passage means.

Claim 17

The automatic control device recited in claim 13, wherein the relationship of the first and second areas is such that the fluid discharged from the fluid motor at approximately servo pressure acts on the second area to open the relief valve.

Claim 18

The automatic control device recited in claim 13, wherein the relationship of the first and second areas is such that the fluid discharged from the fluid motor at less than servo pressure acts on the second area to open the relief valve.

Claim 19

An automatic control device for a variable displacement fluid energy translating device having a rocker cam pivotally mounted in a rocker cam support for changing the displacement of the device, fluid motor means for pivoting the rocker cam incLuding a first fluid motor member attached to the rocker cam and a second fluid motor member cooperative with the first fluid motor member to define first and second sealed fluid receiving chambers, a servo pump for supplying servo pressure fluid, manual control means for selectively supplying servo pressure fluid to said one of fluid receiving chambers and simultaneously exhausting fluid from the other of said fluid receiving chambers to selectively position the rocker cam between a first position of maximum pump displacement in which said one port is the working port and the other port is the inlet port and a second position of maximum pump displacement in which said other port is the working port and said one port is the inlet port, and the improvement comprising automatic control means for overriding said manual control means including compensating means operable when working fluid exceeds a first predetermined pressure to supply working fluid to one of said fluid receiving chambers to reduce displacement of the device until the working fluid maintains the first predetermined pressure, said compensating means including a first compensator valve having an inlet connected to the one port and an outlet connected to the one fluid receiving chamber and a second compensator valve having an inlet connected to the other port and an outlet connected to the other fluid receiving chamber, a first relief valve connected to the one fluid receiving chamber, a second relief valve connected to the other fluid receiving chamber, said first relief valve including means for sensing the pressure in the one port and automatically setting the first relief valve at one setting if the one port is the inlet port and setting the first relief valve at another higher setting if the one port is the working port.

Claim 20

An automatic control device for a variable displacement fluid energy translating device having a rocker cam pivotally mounted in a rocker cam support for changing the displacement of the device, fluid motor means for pivoting the rocker cam incLuding a first fluid motor member attached to the rocker cam and a second fluid motor member cooperative with the first fluid motor member to define first and second sealed fluid receiving chambers, a servo pump for supplying servo pressure fluid, manual control means for selectively supplying servo pressure fluid to said one of fluid receiving chambers and simultaneously exhausting fluid from the other of said fluid receiving chambers to selectively position the rocker cam between a first position of maximum pump displacement in which said one port is the working port and the other port is the inlet port and a second position of maximum pump displacement in which said other port is the working port and said one port is the inlet port, and the improvement comprising automatic control means for overriding said manual control means including compensating means operable when working fluid exceeds a first predetermined pressure to supply working fluid to one of said fluid receiving chambers to reduce displacement of the device until the working fluid maintains the first predetermined pressure, said compensating means including a first compensator valve having an inlet connected to the one port and an outlet connected to the one fluid receiving chamber and a second compensator valve having an inlet connected to the other port and an outlet connected to the other fluid receiving chamber, a first relief valve connected to the one fluid receiving chamber, a second relief valve connected to the other fluid receiving chamber, said first relief valve including means for sensing the pressure in the one port and automatically setting the first relief valve at one setting if the one port is the inlet port and setting the first relief valve at another higher setting if the one port is the working port.

Claim 21

An automatic control device as recited in claim 17, including first means connecting the top of the first relief valve to servo pressure fluid, second means connecting the top of the first relief valve to the one port, a first orifice in the first connecting means, a second orifice in the second connecting means and a check valve in the second connecting means operable between an open position to permit servo fluid to flow through the check valve and the first and second orifices to provide a first setting for the first relief valve and a closed position to prevent servo fluid flow through the check valve and the first and second orifices to provide an increased setting for the first relief valve and working fluid in the one port operates the check valve to the closed position.

Claim 22

An automatic control device as recited in claim 17, wherein said second relief valve includes means for sensing the pressure in the other port and automatically setting the second relief valve at the one setting if the port is the inlet port and setting the second relief valve at another higher setting if the other port is the working port.