Patent Application
20190128256
The present disclosure relates to a fluid pump that includes a shim and related methods of manufacture.
This section provides background information related to the present disclosure which is not necessarily prior art.
Gear pumps include one or more gears that rotate within a gear housing to displace a fluid from an inlet of the pump to an outlet of the pump. The relative spacing of the gears and other components inside the gear housing is a factor that can determine the efficiency and reliability of the gear pump.
In some types of gear pumps, the gears and other internal components are physically stacked next to each other in the gear housing. It is desirable to maintain a desired clearance between the stacked components so that unwanted fluid leakage is minimized. In addition, the desired clearance ensures that the gear (or gears) in the pump can freely rotate during operation. To achieve a desired clearance, various types of traditional manufacturing methods are used to manufacture the components in the pump with tight tolerances such as machining, grinding, polishing and the like. Such manufacturing methods that achieve the tight tolerances can be expensive and time consuming processes. In addition, the stack-up of tolerances of the pump components can increase the variation between pumps assembled with components manufactured according to the same specifications.
There exists a need, therefore, for a pump design that can be assembled with a repeatable desired clearance between internal components. In addition, there is a need for a fluid pump that minimizes unwanted internal leakage of fluid and that can be manufactured with less variation.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
In one example embodiment of a fluid pump in accordance with the present disclosure, the fluid pump includes a gear housing with a pocket wall and a base. The pocket wall and the base define a pocket that projects into the gear housing from a pocket surface. The base is oriented parallel to the pocket surface and the pocket wall connects the pocket surface to the base. The fluid pump also includes a first gear rotatably positioned in the pocket. The first gear includes a first face that is oriented parallel to the pocket surface. The first face is spaced from the pocket surface by a first gap. The fluid pump also includes a second gear rotatably positioned in the pocket that engages the first gear. The second gear includes a second face that is oriented parallel to the pocket surface. The second face is spaced from the pocket surface by a second gap. The fluid pump also includes a selected shim positioned in the pocket over the first gear and the second gear. The selected shim is selected from a plurality of shims in a shim set by comparing thicknesses of the shims in the plurality of shims to the first gap or the second gap. The selected shim has a thickness that results in a desired clearance between the selected shim and the first face or the second face.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
Although not required by the present disclosure, exhaust after-treatment system 16 can further include components such as a thermal enhancement device or burner 26 to increase a temperature of the exhaust gases passing through exhaust passage 14. Increasing the temperature of the exhaust gas is favorable to achieve light-off of the catalyst in the exhaust treatment component 18 in cold-weather conditions and upon start-up of engine 12, as well as initiate regeneration of the exhaust treatment component 18 when the exhaust treatment substrate 22 or 24 is a DPF.
To assist in reduction of the emissions produced by engine 12, exhaust after-treatment system 16 can include a dosing module 28 for periodically dosing an exhaust treatment fluid into the exhaust stream. As illustrated in
The amount of exhaust treatment fluid required to effectively treat the exhaust stream may vary with load, engine speed, exhaust gas temperature, exhaust gas flow, engine fuel injection timing, desired NOx reduction, barometric pressure, relative humidity, EGR rate and engine coolant temperature. A NOx sensor or meter 38 may be positioned downstream from exhaust treatment component 18. NOx sensor or meter 38 may also be positioned upstream or between the exhaust treatment components 18 and 20. NOx sensor 38 is operable to output a signal indicative of the exhaust NOx content to an engine control unit 40. NOx sensor or meter 38 may also be replaced by a particulate matter sensor. All or some of the engine operating parameters may be supplied from engine control unit 40 via the engine/vehicle databus to a reagent electronic dosing controller 42. The reagent electronic dosing controller 42 could also be included as part of the engine control unit 40. Exhaust gas temperature, exhaust gas flow and exhaust back pressure and other vehicle operating parameters may be measured by respective sensors, as indicated in
The amount of exhaust treatment fluid required to effectively treat the exhaust stream can also be dependent on the size of the engine 12. In this regard, large-scale diesel engines used in locomotives, marine applications, and stationary applications can have exhaust flow rates that exceed the capacity of a single dosing module 28. Accordingly, although only a single dosing module 28 is illustrated for dosing exhaust treatment fluid, it should be understood that multiple dosing modules 28 for reagent injection are contemplated by the present disclosure.
As described, the pump 32 can be any suitable fluid pump for dosing the exhaust treatment fluid into the exhaust stream. One suitable type of pump 32 is a gear pump. As depicted in
The filter casing 52, in this example, is also positioned over a portion of fluid pump head 60. The filter casing 52 can include a filter assembly (not shown) that can be in fluid communication with the fluid pump head 60 to filter contaminants from the fluid contained in or flowing through the pump 32 during operation. The filter casing 52 and the motor casing 50 can be joined to each other to surround the fluid pump head 60 as shown. In other examples, the pump 32 can include other configurations and/or casings and may include other assemblies that can be joined to the fluid pump head 60.
The gear housing 62, as shown in
The gear housing 62 further includes, in this example, a first inlet 94 and a first outlet 96. The first inlet 94 and the first outlet 96 are openings that extend through the gear housing 62 to fluidly connect the pocket 74 to a fluid source, a fluid conduit, a nozzle or other element that may be connected to the fluid pump head 60. When the fluid pump head 60 is operating, the fluid flowing through the fluid pump head 60 enters through the first inlet 94 and exits through the first outlet 96.
The fluid pump head 60 can be made of any suitable material. In this example, the gear housing 62 is made of stainless steel. The gear housing 62 can be cast and then machined into the configuration described. In another example, the gear housing 62 can be machined from stainless steel bar stock. In other examples, other metals, alloys, plastics and composites can also be used.
As shown in
The first post 86 and the second post 88, in this example, are cylindrical features of the gear guide 72 that project away from the footing 84. The first post 86 is located at or near the center of the first lobe 90 and the second post 42 is located at or near the center of the second lobe 92. In this manner, the first post 86 and the second post 88 are located at or near the center of the first circular depression 80 and the second circular depression 82 when the gear guide is installed in the pocket 74.
The first post 86 and the second post 88 are spaced apart from one another such that the first gear 68 and the second gear 70, when received over the first post 86 and the second post 88, respectively, engage with one another. When installed over the first post 86 and the second post 88, the first gear 68 rotates around the first post 86 and the second gear 70 rotates around the second post 88. As shown in
Referring back to
The first gear 68 includes teeth 102 and the second gear 70 includes teeth 152. The teeth 102 of the first gear 68 and the teeth 152 of the second gear 70 are sized such that they can mesh and engage with one another to displace fluid in the pocket 74 of the gear housing 62 when the first gear 68 and the second gear 70 rotate around the first post 86 and the second post 88, respectively.
The teeth 102 and the profile of the first gear 68 and the teeth 152 and the profile of the second gear 70 can be similar to one another. In the example shown, the teeth 102 have a rounded triangular shape. The first gear 68 and the second gear 70 each have nine teeth 102, 152 evenly spaced around their peripheries. In other examples, the teeth 102, 152 can have other shapes and the first gear 68 and/or the second gear 70 can more or less than nine teeth 102, 152.
The first gear 68, as shown in the example of
The second gear 70, in the example shown, includes a second engaging portion 110 and a collar 112. The second engaging portion 110 is the portion of the second gear that includes the teeth 102 that engage the teeth 102 of the first gear 68. The collar 112 is a circular boss that projects away from the second engaging portion 110. The collar 112 can be used to interface with the shim 66 (as will be explained further below) or other element of the fluid pump head 60 to maintain the second gear 70 in a desired position in the pocket 74. To this end, the collar 112 is positioned at or near the center of the second gear 70.
The first gear 68 and the second gear 70 can be made of any suitable material. In this example, the first gear 68 and the second gear 70 are made of polyether ether ketone (PEEK). This material has mechanical and chemical resistant properties at high temperatures. Other materials, such as stainless steel, can also be used.
The shim 66, in this example, is located in the pocket 74 and is inserted over the first gear 68 and the second gear 70. The shim 66 has a two-lobed profile and includes a first ring 114 and a second ring 116. The shim 66 is sized such that the outer diameter of the first ring 114 is less than the inner diameter of the first lobe 90 of the pocket 74. The outer diameter of the second ring 116 is less than the inner diameter of the second lobe 92 of the pocket 74.
The shim 66 also includes a first aperture 118 and a second aperture 120. The first aperture 118 is positioned at or near the center of the first ring 114. The inner diameter of the first aperture 118 is greater than the outer diameter of the drive extension 106. The second aperture 120 is positioned at or near the center of the second ring 116. The inner diameter of the second aperture 120 is greater than outer diameter of the collar 112. With this configuration and as shown in
The shim 66 can also include a first notch 122 and/or a second notch 124. The first notch 122 and the second notch 124, in the example shown in
As shown, the shim 66, the first gear 68, the second gear 70 and the gear guide 72 are located in the pocket 74. These components stack inside in the pocket 74 such that the shim 66 does not project beyond a pocket surface 130 of the gear housing 62. As can be appreciated, the shim 66, the first gear 68, the second gear 70 and the gear guide 72 are located within the pocket 74 and do not project beyond the pocket surface 130 because interference between these components and the cover plate 64 is undesirable. When the cover plate 64 is installed over the pocket 74, interference between the shim 66, the first gear 68, the second gear 70 or the gear guide 72 and the cover plate 64 can cause inefficiencies if the components were to bind or otherwise contact one another.
As shown in
In another example of the fluid pump head 60, the cover plate 64 can be positioned over the pocket 74 such that a portion of the cover plate 64 can be separated from the pocket surface 130 of the gear housing 62. In such examples, the shim 66 can project above the pocket surface 130 and into the portions of the cover plate 64 that may be separated from the pocket surface 130. In these examples, the stack up of the components positioned in the pocket 74 (i.e., the gear guide 72, the first gear 68, the second gear 70 and the shim 66) is configured so that a desired clearance is maintained between the components to ensure efficient and reliable operation.
Referring back to the example shown in
As shown in
In the example of
As further shown in
It is desirable that the stack-up of the thicknesses of the footing 84, the first gear 68 and the shim 66 (T1+T2+T3) is less than the height H1. As previously described, if the stack-up of the thicknesses of the footing 84, the first gear 68 and the shim 66 are greater than the height H1 of the pocket 74, the components can bind or interfere and cause inefficiencies in the fluid pump head 60.
It is also desirable that clearances between the gear guide 72, the first gear 68, the shim 66 and the cover plate 64 are minimized. The reduction of the clearance between these components reduces leakage that may otherwise occur between these components. Internal leakage between these components can lead to inefficiencies in the fluid pump head 60.
One way of achieving the desired clearance C and minimizing the clearances between the components is to control the variation of the thickness of the gear guide 72, the first gear 68, the shim 66 and the height of the pocket 74. Since the gear guide 72, the first gear 68 and the shim 66 are stacked next to each other, the variation of the stacked thickness is difficult to control since the tolerances associated with the thicknesses of the individual components are also stacked with each other. The control of tight tolerances for the thicknesses of the gear guide, the first gear 68, the shim 66 and the height of the pocket 74 can be expensive and time consuming.
Instead of specifying tight or reduced tolerances for the thicknesses of the gear guide 72, the first gear 68, the shim 66 and/or the height of the pocket 74, one method of assembling the fluid pump head 60 to achieve a desired clearance C in accordance with the present disclosure includes measuring a gap after one or more of the components is assembled into the pocket 74 and then choosing a shim 66 from a plurality of shims with different thicknesses to obtain the desired clearance C.
As shown in
Similarly, the second gear 70 has a second face 150. The second face 150 is a surface of the second engaging portion 110 of the second gear 70 that is oriented away from the base 78 of the pocket 74. The second face 150 is spaced apart from the pocket surface of the gear housing 62 by a second gap 146. The second gap 146 is measured along the pocket wall 76 in a direction parallel to the center axis of the first post 86.
The first gap 144 and/or the second gap 146 can be measured during the assembly process. A gauge, micrometer, coordinate measuring machine (CMM) or caliper can be used to measure the first gap 144 and/or the second gap 146. After determining the first gap 144 and/or the second gap 146, an appropriately sized shim 66 can be selected from a plurality of shims with varying thicknesses such that when the selected shim is inserted into the pocket 74, the resulting clearance is the desired clearance C.
A shim set (not shown) can be supplied to aid in the previously described assembly process. The shim set can be a bundle of the shims 66. The shims 66 have varying thicknesses T3. In one example fluid pump head 60, the desired clearance C is approximately 20 microns. To achieve this desired clearance, the shim set can include shims 66 that vary in thickness from 0.5 mm to 0.71 mm. The shims 66, in this example shim set, would each have a thickness that varies by approximately 3 microns. In another example, the shim set can be a bundle consisting of ten to fifteen of the shims 66. The ten to fifteen shims 66, in this alternate example, each have a different thickness T3 that varies between 0.5 mm to 1.5 mm. In this example, the shim set consists of shims 66 having thickness T3 of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm and 1.5 mm. In other examples, there can be more than fifteen shims in the shim set or there can be less than ten shims in the shim set. The shims in the shim set can have other variations in thicknesses T3 as well. As can be appreciated, for different sizes of the fluid pump head 60, the size and thicknesses of the shims 66 in the shim set can be different to accommodate larger or smaller fluid pump heads 60. In still other examples, the pump head 60 can be assembled with gear guides 72 with differing thicknesses T1 of the footing 84 to achieve a desired clearance C or to accommodate different shim sets or different sizes of the pump head 60.
The shims 66 can be made of any suitable material such as ceramic or stainless steel. In other examples, other materials can also be used. In order to achieve the necessary varying thicknesses of the shims 66, a grinding or lapping operation can be used to produce the shims 66. In other examples, other processes can be used.
In another example of the fluid pump head 60, the first gap 144 and/or the second gap 146 can be measured relative to a pocket side 162 of the cover plate 64. The pocket side 162 of the cover plate 64 is the surface of the cover plate 64 oriented toward the gear housing 62. In the example shown in
At step 176, the first gap 144 is measured. As described, the first gap 144 is a height between the first face 148 and the pocket surface 130 measured in the direction parallel to the center axis 160 of the first post 86. Alternatively, the first gap 144 can be measured as the height between the first face 148 and the pocket side 162 of the cover plate 64.
At step 178, the second gap 146 is measured. As described, the second gap is a height between the second face 150 and the pocket surface measured in the direction parallel to the center axis 160 of the first post 86. Alternatively, the second gap 146 can be measured as the height between the second face 150 and the pocket side 162 of the cover plate 64.
At step 180, the measured first gap 144 is compared to the measured second gap 146. The smaller of the first gap 144 and the second gap 146 is used in the subsequent steps of the process. As can be appreciated, the shim 66 that is selected at the later steps is smaller than the first gap 144 or the second gap 146 if the desired clearance is to be achieved. Therefore, at step 180, the first gap 144 is compared to the second gap 146 to determine which of the first gap 144 and the second gap 146 is smaller.
At step 182, the smaller of the first gap 144 and the second gap 146 is compared to the thicknesses of the shims 66 in the shim set. As described above, the shim set includes a plurality of shims of varying thicknesses.
At step 184, the shim 66 with a thickness closest to but less than the smaller of the first gap 144 and the second gap 146 is selected from the shim set. Alternatively, at step 184, the shim 66 can be selected from the shim set so that the desired clearance C is achieved. In one example, the desired clearance is a minimum clearance.
At step 186, the selected shim 66 is inserted into the pocket 74 over the first gear 68 and the second gear 70. At step 188, the cover plate 64 is installed over the pocket 74 to retain the gear guide 72, the first gear 68, the second gear 70 and the shim 66 inside the gear housing 62.
As can be appreciated, one or more of the previously described steps of the example method can be excluded. In addition, additional steps can be performed. Such alterations to the previously described method may be desirable or advantageous in other example embodiments of the fluid pump head 60.
In one such alternate example of the fluid pump head 60 (not shown), the fluid pump head 60 does not include a separate gear guide 72. In this alternate example, the first post 86 and the second post 88 can be press fit or otherwise secured in the base 78 of the pocket 74. The first post 86 and the second post 88 can be similarly configured as previously described. In this example, the first gear 68 and the second gear 70 are positioned directly adjacent the base 78 of the pocket 74 over the first post 86 and the second post 88, respectively. The shim 66, as previously described, can still be used in this example to achieve a desired clearance C between the first gear 68 and/or the second gear 70 and the shim 66.
In still another example, the second gear 70 is not positioned on the second post 88. In this example, the second gear 70 is positioned in the second circular depression 82 of the pocket 74 without a supporting axial member (e.g., second post 88). The second gear 70 is retained in its position by the pocket wall 76 and its engagement to the first gear 68. In this example, the shim 66 does not include a second aperture 120. Instead, the second ring 116 is a planar member that covers the second lobe 92 of the pocket 74. The shim 66 can still be used to achieve a desired clearance C between the first gear 68 and/or the second gear 70 and the shim 66.
The previously described fluid pump head 60, and variations thereof, advantageously reduces the amount of internal leakage in the fluid pump head 60 by reducing the clearances between the internal components. This reduction increases the efficiency of the fluid pump head 60 and also reduces the variation from pump to pump. The foregoing fluid pump head 60 and the related method of manufacture also reduce the likelihood of interference or binding of internal components. Given that the structure of the fluid pump head 60 and the related method of manufacture ensure that the desired clearance between the internal components is maintained, it may also be possible to reduce the size and/or power of the pump motor that is used to drive the fluid pump head 60. These improvements can reduce the cost and increase the reliability of the fluid pump head 60.
As can be appreciated, the fluid pump head 60 can be used in a variety of applications. In the example application previously described, the fluid pump head 60 is used in the exhaust system 10. The fluid pump head 60, however, can be used to transfer fuel, oil or other fluids as well. In addition, the fluid pump head 60 can be used in a variety of industrial applications including in the automotive, chemical, manufacturing, and energy industries.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
