US20110129359A1

US20110129359A1 - Variable output pump

Info

Publication number: US20110129359A1
Application number: US12/627,231
Authority: US
Inventors: Colin Anthony Hawkins
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2009-11-30
Filing date: 2009-11-30
Publication date: 2011-06-02

Abstract

An variable output pump is disclosed. The variable output pump having a rotatable first shaft, a first pumping element mounted to the rotatable first shaft, and a coupling mechanism configured to couple the first pumping element to the first shaft for rotation therewith in a first mode, and decouple the first pumping element from the rotatable first shaft in a second mode. A method for varying the output of a fluid pump is also disclosed. The method including rotating a first pumping element and a second pumping element; and preventing rotation of the first pumping element in response to an increase in fluid pressure, while continuing to rotate the second pumping element.

Description

TECHNICAL FIELD

The present disclosure relates generally to a pump and, more particularly, to a variable output pump.

BACKGROUND

Internal combustion engines, including diesel engines, gasoline engines, natural gas engines, turbine engines, and other engines known in the art, are used to drive many types of power systems. Internal combustion engines typically include an oil lubrication system and an oil pump to circulate oil through the system. The oil pressure needed to properly lubricate an internal combustion engine may vary with the operating conditions of the engine. As a result, pumps have been developed that allow for the pump output to be changed or varied as desired.
U.S. Pat. No. 5,620,315 (hereinafter the '315 patent), by Pfuhler, discloses a variable output gear pump. The '315 patent discloses a pair of gears arranged axially parallel to each other. One gear is axially fixed while the other gear is movable in the axial direction to change the amount of mating surface between the two gear, and thus, change the output from the gear pump.
While the pump disclosed in the '315 patent may provide for variable output, it requires a housing of sufficient size to allow one gear to translate axially relative to another gear. Furthermore, it presents gear loading and sealing problems due to the change in contact surface between the gears and translating nature of one gear relative to the other gear.
The present disclosure is directed to overcoming one or more of the shortcomings in the existing technology.

SUMMARY

In accordance with one aspect, the present disclosure is directed to a variable output pump having a rotatable first shaft, a first pumping element mounted to the rotatable first shaft, and a coupling mechanism configured to couple the first pumping element to the first shaft for rotation therewith in a first mode, and decouple the first pumping element from the rotatable first shaft in a second mode.
According to another aspect, the present disclosure is directed toward a method for varying the output of a fluid pump. The method rotating a first pumping element and a second pumping element; and preventing rotation of the first pumping element in response to an increase in fluid pressure, while continuing to rotate the second pumping element.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which are incorporated in and constitute a part of this specification, exemplary embodiments of the disclosure are illustrated, which, together with the written description, serve to explain the principles of the disclosed system:

FIG. 1 is a schematic illustration of an exemplary power system;

FIG. 2 is schematic illustration of an embodiment of variable output pump for the power system of the power system of FIG. 1;

FIG. 3 is a partial cross section view of the variable output pump of FIG. 2 in a first mode; and

FIG. 4 is a partial cross section view of the variable output pump of FIG. 2 in a second mode.

DETAILED DESCRIPTION

Referring to FIG. 1, an exemplary power system 10 is disclosed. The power system 10 may include an engine 12 having a lubrication system 14. The engine 12 may include features not shown, such as fuel systems, air systems, cooling systems, peripheries, drivetrain components, turbochargers, etc. The engine 12 may be any type of engine (internal combustion, turbine, gas, diesel, gaseous fuel, natural gas, propane, etc.), may be of any size, with any number of cylinders, and in any configuration (“V,” in-line, radial, etc.). The engine 12 may be used to power any machine or other device, including locomotive applications, on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, pumps, stationary equipment, or other engine powered applications.
The engine 12 may include an engine block 16 that at least partially defines a plurality of cylinders (not shown), a piston (not shown) slideably disposed within each cylinder and one or more cylinder heads 18 associated with the cylinders. The engine 12 may also include a crankshaft (not shown) that is rotatable supported within the engine block 16 by way of a plurality of journal bearings (not shown). The engine 12 may also include one or more turbochargers 20 configured to recover energy from the exhaust of the engine 12 and use the energy to compress air that the engine 12 will use for combustion. The one or more turbochargers 20 may include a turbine wheel 22 and a compressor wheel 24 mounted onto a rotatable shaft 26.
The lubrication system 14 transports lubricating fluid to the journal bearing, rotatable shaft 26, and other locations that require lubrication and/or cooling. The lubrication system 14 may be configured in a variety of ways. Any system capable of delivery lubricating fluid at appropriate pressure and temperature to critical areas in the power system 10 may be used.
In the depicted embodiment, the lubricating system includes a sump 32, a pump 34, a pressure relief valve 36, a cooler 38, a filter 40, and a first fluid passage 42, and a second fluid passage 44. The sump 32 may be any suitable metallic or polymeric chamber capable of holding a volume of lubricating fluid. For example, the sump 32 may be positioned at a bottom portion of the engine 12 and function as a reservoir for the lubrication system 14.
The pump 34 is fluidly connected to the sump 32 via the first fluid passage 42 and is configured to draw lubricating fluid from the sump 32. The pump 34 will be described in more detail below. The pressure relief valve 36 may be disposed in the first fluid passage 42 and configured to fluidly connect the first fluid passage 42 with the second fluid passage 44 when the pressure in the first fluid passage way exceeds a pressure threshold. Thus, the pressure of the lubricating fluid delivered to the engine 12 may be regulating by returning excess lubricating fluid back to the sump 32.
The filter 40 may be disposed in the first fluid passage 42 and configured to remove undesirable particles and foreign matter from the lubricating fluid. The filter 38 may be any suitable lubricating filter known in the art. The cooler 38 may be disposed in the first fluid passage 42 and configured to utilize a cooling medium, such as engine coolant, to control the temperature of the lubricating fluid to a desired range prior to the fluid entering the engine 12.
The engine 12 may contain a plurality of fluid passages within the engine block 16 and cylinder head(s) 18 for routing lubricating fluid to appropriate locations within the engine 12. For example, the engine 12 may include a main gallery 48 that receives lubricating fluid from the first fluid passage 42. From the main gallery 48, lubricating fluid may be routed under pressure to the journal bearings (not shown), the pistons (not shown), the turbocharger shaft 26, and other engine components before being returned to the sump 32.
Referring to FIGS. 2-4, the pump 34 may be configured in a variety of ways. Any pump 34 capable of selectively disengaging a pumping element from a rotatable shaft may be used. In the depicted embodiment, the pump 34 includes a pump housing 52 configured to form a fluid inlet 54, a fluid outlet 56, and a cavity 58 connecting the fluid inlet 54 to the fluid outlet 56. Disposed within the cavity 58 are a first pumping element 60 mounted onto a rotatable first shaft 62 and a second pumping element 64 mounted onto the rotatable first shaft 62. The first shaft 62 extends along a first axis 65.
The pump 34 includes a third pumping element 66 disposed within the cavity 58 and configured to be rotatably driven by the first pumping element 60. The third pumping element 66 may be rotatable mounted in any suitable way. For example, the third pumping element 66 may be mounted on a rotatable second shaft 68 or a rotatable axle. A fourth pumping element 70 is also disposed within the cavity 58 and is mounted onto the rotatable third shaft 72. The second shaft 68 and the third shaft 72 may be coaxial along a second axis 73. The first axis 65 may be arranged in parallel to the second axis 73.
The first pumping element 60, the second pumping element 64, the third pumping element 66, and the fourth pumping element 70 may be configured substantially similar to each other, though that is not required. In the depicted embodiment, the pumping elements are configured as spur gears (i.e. a disc-shaped body having a straight gear face around the circumference and a central bore for receiving a shaft). The first pumping element 60 is configured to mate with the third pumping element 66 to form a first pumping element pair 74 and the second pumping element 64 is configured to mate with the fourth pumping element 70 to form a second pumping element pair 76.
The second pumping element 64 and the fourth pumping element 70 may be fixably mounted onto the rotatable first shaft 62 and the rotatable third shaft 72, respectively, in any suitable manner, such as but not limited to, fasteners, press fit, welding, pinned or keyed, or other suitable means. The first pumping element 60 may be mounted onto the first shaft 62 such that in a first mode, the first pumping element 60 is fixed to the first shaft 62 and rotates with the first shaft 62 and in a second mode, the first pumping element 60 is held stationary while the first shaft 62 rotates. A coupling mechanism 78 may be provided to couple and decouple the first pumping element 60 and the first shaft 62. The pump housing 52 may at least partially enclose the coupling mechanism 78.
Referring to FIGS. 3 and 4, in the depicted embodiment, the first pumping element 60 includes an inner surface 80 that defines a central bore configured to receive the first shaft 62. The first shaft 62 may be configured as an elongated, generally cylindrical structure having a first end 82 configured to extend through the bore of the first pumping element 60. The first shaft 62 may include an inner bore 84 extending axially from the first end 82 along a length of the first shaft 62. The first shaft 62 may include one or more apertures 86 extending radially from the inner bore 84 through the first shaft 62.
The coupling mechanism 78 may be configured in a variety of ways. Any structure capable of selectively coupling and decoupling the first pumping element 60 and the first shaft 62 may be used. In the depicted embodiment, the coupling mechanism 78 includes a fluid passage 88, a inner housing surface 89 defining a cylinder 90 in fluid communication with the fluid passage 88, a plunger 92 disposed within the cylinder 90 and configured to move axially within the cylinder, an actuator 94, a drive element 96, and a first biasing element 98.
The fluid passage 88 is configured to fluidly couple the high pressure portion of the cavity 58 (i.e. portion exposed to the outlet pressure of the pump 34) to the cylinder 90. A temperature actuated valve 100 may be disposed in the fluid passage 88. The temperature actuated valve 100 may be configured to open the fluid passage 88 when the temperature of the lubricating fluid exceeds a temperature threshold and close the fluid passage when the temperature of the lubricating fluid is below the temperature threshold. For example, the temperature actuated valve 100 may be a wax bulb type thermostat that moves a valve element (not shown) at a preset temperature to open the fluid passage 88 and at another preset temperature to close the fluid passage 88.
The plunger 92 may be a substantially cylindrical structure having an end portion 102 that forms an end face 104 and a cylindrical skirt 106 extending axially from the end portion 102. The skirt 106 forms a recess configured to receive the first end 82 of the first shaft 62. Positioned at the distal end of the skirt 106 is an interface 108 configured to engage the first pumping element 60 and prevent the first pumping element 60 from rotating when the first pumping element 60 is decoupled from the first shaft 62. The interface may be configured in a variety of ways. For example, the interface 108 may be an edge or projection configured to engage an interface surface 110 or recess in the first pumping element 60.
The actuator 94 may be configured to move axially in the cylinder 90 in response to movement of the plunger 92. The actuator 94 may be generally cylindrical projection extending along the first axis 65 and include a first end 112 configured to engage the end portion 102 of the plunger 92 and a second end 114 configured to be received within the inner bore 84 the first shaft 62. The actuator 94 may have an intermediate portion 116 having a diameter less than the diameter of the second end 114 connected to the second end 114 by a tapered portion 118. The first end 112 may be disposed radially inward from the skirt 106 and may loosely engage, be fixably attached to, or be integrally formed with the end portion 102 of the plunger 92.
The drive element 96 may include one or more engagement portions 120 and a second biasing element 122. The drive element 96 may be configured to move between a first position in which the engagement portions 120 are radially expanded to engage the inner surface 80 of the first pumping element 60 and a second position in which the engagement portions 120 are radially retracted away from the inner surface 80. The second biasing element 122 may be connected to the engagement portions 120 to bias the engagement portions 120 away from the inner surface 80.
The first biasing element 98 may be positioned within the inner bore 84 of the first shaft 62 between an inner radially extending surface 124 of the first shaft 62 and the second end 114 of the actuator 94. The first biasing element 98 being configured to bias the actuator 94 axially away from the first shaft 62.
One or more sealing elements 126 may be configured to provide a fluid seal between the plunger 92 and the inner housing surface 89. For example, an annular seal 126 may be received in a groove (not shown) in the inner housing surface 89 to provide a seal against lubricating fluid that enters the cylinder 90 from flowing past the plunger 92 toward the first pumping element 60.

INDUSTRIAL APPLICABILITY

The disclosed pump 34 may be applicable to any application in which it would be beneficial to have more variable output from the pump. For example, the disclosed pump 34 may be used as a lubricating fluid pump for a power system, such an engine and thus provide sufficient lubricating fluid pressure at idle conditions without wasting energy with excessive capacity at higher engine speeds. The operation of exemplary power system 10 will now be explained.
During engine operation, to prevent damage to engine components from metal-to-metal contact, the lubrication system 14 is configured to transport lubricating fluid to the journal bearing, turbocharger shaft 26, and other locations in the engine that require lubrication and/or cooling. In operation, the pump 34 draws lubricating fluid from the sump 32 and through the lubrication system and engine 12 as described above in relation to FIG. 1.
The pump 34 is driven via the third shaft 72 by the engine 12, for example. Since the fourth pumping element 70 is fixably mounted to the third shaft 72, rotation of the third shaft 72 rotates the fourth pumping element 70. The second pumping element 64 mates with the fourth pumping element 70. Thus, rotation of the fourth pumping element 70 rotates the second pumping element 64. Since the second drive element 64 is fixably attached to the first shaft 62, rotation of the second pumping element 64 rotates the first shaft 62.
In a first mode, the first pumping element 60 is fixed for rotation with the first shaft 62. In particular, as shown in FIG. 3, the temperature actuated valve 100 is in closed and blocking the fluid passage 88. This occurs when the temperature of the lubricating fluid in the pump 34 is below the temperature threshold. When the fluid passage 88 is blocked, the plunger 92 is not exposed to fluid pressure from the lubricating fluid, thus the first biasing element 98 will bias the plunger 92 to a first position in the cylinder 90 (to the far right as illustrated in FIG. 3).
When the plunger 92 is in the first position, the second end 114 of the plunger 92 is radially inward of the drive element 96. Thus, the engagement portions 120 are radially extended against the bias of the second biasing element 122 to engage the inner surface 80 of the first pumping element 60. As a result, the first pumping element 60 is fixed relative to the first shaft 62 for rotation therewith.
The third pumping element 66 mates with the first pumping element 60 and is rotatably mounted. Thus, rotation of the first pumping element rotates the third pumping element 66. In the first mode, both the first pumping element pair 74 and the second pumping element pair 76 are active.
If the temperature of the lubricating fluid exceeds the temperature threshold and the lubricating fluid exceeds a pressure threshold, the pump will be placed in a second mode. In the second mode, the first pumping element 60 is decoupled from the first shaft 62, thus deactivating the first pumping element pair 74.
In particular, as shown in FIG. 3, when the lubricating fluid temperature exceeds the temperature threshold, the temperature actuated valve 100 will open and lubricating fluid under pressure will flow through the fluid passage 88 and impinge upon the end face 104 of the plunger 92. If the fluid pressure exceeds the pressure threshold (i.e. sufficient tot overcome the bias of the first biasing element 98), the plunger 92 will move from the first position to a second position (as shown in FIG. 4).
When the plunger 92 is in the second position, the intermediate portion 116 of the plunger 92 is radially inward of the drive element 96. Since the diameter of the intermediate portion 116 is smaller than the diameter of the second end 114, the second biasing element 122 may bias the engagement portions 120 are radially inward, thus; disengaging the engagement portions 120 with the inner surface 80 of the first pumping element 60.
In addition, when the plunger 92 is in the second position, the interface 108 engages the interface surface 110 of the first pumping element 60 to prevent the first pumping element 60 from rotating or spinning freely. Thus, in the second mode, the first pumping element pair 74 is deactivated while the second pumping element pair 76 remains active.
The disclosed pump, therefore, may provide full pumping capacity when the temperature and the pressure of the lubricating fluid are below predetermined thresholds, such as when the engine is operating a low idle. When the temperature and the pressure exceed predetermined threshold, the capacity of the pump may be reduced since at higher speeds the lubricating fluid quantity required to maintain sufficient pressure is significantly less than the full pump capacity. As a result, wasted energy in the form of pressurized lubricating fluid returned to the sump 32 can be reduced.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed dosing system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and apparatus. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A variable output pump, comprising:

a rotatable first shaft;

a first pumping element mounted to the rotatable first shaft; and

a coupling mechanism configured to couple the first pumping element to the first shaft for rotation therewith in a first mode, and decouple the first pumping element from the rotatable first shaft in a second mode.

2. The variable output pump of claim 1 wherein the coupling mechanism switches between the first mode and the second mode in response to a change in fluid pressure.

3. The variable output pump of claim 2 wherein the coupling mechanism switches between the first mode and the second mode in response to a change in fluid temperature.

4. The variable output pump of claim 1 further comprising a second pumping element mounted to the rotatable first shaft, wherein the second pumping element remains coupled to the first shaft in the second mode.

5. The variable output pump of claim 1 wherein the first pumping element is a first gear and the second pumping element is a second gear, and the pump further comprises a third gear configured to mate with the first gear and a fourth gear configured to mate with the second gear

6. The variable output pump of claim 5 wherein the third gear is mounted on a second rotatable shaft and the fourth gear is mounted on a third rotatable shaft.

7. The variable output pump of claim 1 comprising a plunger configured to translate axially between a first position and a second position to switch the variable output pump from the first mode to the second mode.

8. The variable output pump of claim 8 further comprising a biasing element configured to bias the plunger toward the first position.

9. The variable output pump of claim 8 wherein the plunger includes an interface configured to prevent the first pumping element from rotating when the plunger is in the second position.

10. The variable output pump of claim 1 further comprising a drive element configured to move radially inward to decouple the first pumping element from the rotatable first shaft.

11. A method for varying the output of a fluid pump, comprising:

rotating a first pumping element and a second pumping element; and

preventing rotation of the first pumping element in response to an increase in fluid pressure, while continuing to rotate the second pumping element.

12. The method of claim 11 wherein the step of rotating a first pumping element and a second pumping element further comprising rotating a first shaft.

13. The method of claim 12 comprising decoupling the first pumping element from the first shaft.

14. The method of claim 13 comprising opening a fluid passage in response to a fluid temperature exceeding a temperature threshold.

15. A power system, comprising:

an engine;

a sump configured to hold a volume of fluid; and

a variable output pump configured to draw fluid from the sump and deliver the fluid to the engine, the variable output pump, comprising:

a rotatable first shaft;

a first pumping element mounted to the rotatable first shaft; and

16. The power system of claim 15 wherein the coupling mechanism switches between the first mode and the second mode in response to a change in a pressure of the fluid.

17. The power system of claim 16 wherein the coupling mechanism switches between the first mode and the second mode in response to a change in fluid temperature.

18. The power system of claim 15 further comprising a second pumping element mounted to the rotatable first shaft, wherein the second pumping element remains coupled to the first shaft in the second mode.

19. The power system of claim 17 wherein the first pumping element is a first gear and the second pumping element is a second gear, and the pump further comprises a third gear configured to mate with the first gear and a fourth gear configured to mate with the second gear.

20. The variable output pump of claim 15 comprising an interface configured to prevent the first pumping element from rotating when the coupling mechanism is in the second mode.