BACKGROUND Oil pumps circulate oil to various components of an engine to assist with friction reduction and cooling. During circulation, the oil can experience changes in pressure based on various factors, such as where the oil is in the cycle and the type of pump utilized. In some instances, rapid changes in oil pressure can cause undesirable engine noise, such as a “whining” sound. SUMMARY An embodiment of the present invention is directed to a noise-reduction mechanism for an oil pump. The noise-reduction mechanism attaches to the oil-pump outlet tube through which oil is pumped and functions to reduce the rate of oil-pressure change. Embodiments of the invention are defined by the claims below, not this summary. A high-level overview of various aspects of the invention is provided here for that reason, to provide an overview of the disclosure, and to introduce a selection of concepts further described below in the detailed-description section. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in isolation to determine the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS Illustrative embodiments of the present invention are described in detail below with reference to the attached figures, which are incorporated herein by reference, wherein: FIG. 1 depicts an exemplary variable-displacement oil pump environment in accordance with an embodiment of the present invention; FIG. 2 depicts an exemplary variable-displacement oil pump (VDOP) in accordance with an embodiment of the present invention; FIG. 3 depicts a graph showing changes in pressure rates versus crank angle in a noisy oil pump, which does not include a noise-reduction device, in accordance with an embodiment of the present invention; FIG. 4 depicts a graph showing changes in pressure rates versus crank angle in a quiet oil pump, which may or may not include a noise-reduction device, in accordance with an embodiment of the present invention; FIG. 5A depicts a graph that compares oil-pump noise of a variable-displacement oil pump and a fixed-displacement oil pump, neither of which includes a noise-reduction device, in accordance with an embodiment of the present invention; FIG. 5B depicts a graph showing changes in pressure rates versus crank angle in an originally noisy oil pump, after adding a noise-reduction device, in accordance with an embodiment of the present invention; FIG. 6A depicts a VDOP that is coupled with a noise-reduction device in accordance with an embodiment of the present invention; FIG. 6B depicts an exploded view of a VDOP and a noise-reduction device in accordance with an embodiment of the present invention; FIG. 6C depicts a VDOP that is coupled with a noise-reduction device in accordance with an embodiment of the present invention; and FIG. 7 depicts a plan view of a noise-reduction device in accordance with an embodiment of the present invention. DETAILED DESCRIPTION The subject matter of embodiments of the present invention is described with specificity herein to meet statutory requirements. But the description itself is not intended to necessarily limit the scope of claims. Rather, the claimed subject matter might be embodied in other ways to include different elements or combinations of elements similar to the ones described in this document, in conjunction with other present or future technologies. As indicated in other parts of this specification, the present invention is directed to a noise-reduction device for any noisy fixed, or variable-displacement, oil pump. The noise-reduction device attaches to the oil-pump outlet tube through which oil is pumped out and helps to control the rate at which the oil pressure changes. Referring now to FIG. 1, a portion of an oil-pump arrangement 10 is depicted, including an oil-pump housing 12, an inlet region 14, and an outlet-port tube 16. The oil-pump housing 12 functions to encase an oil pump, and in one embodiment, the oil pump is a variable-displacement oil pump. For exemplary purposes, a cross-section view of a type of variable-displacement oil pump is shown in FIG. 2. Referring briefly to FIG. 2, the variable-displacement oil pump 20 includes an inlet port 22, an outlet port 24, a rotor 26 having sliding vanes 28, a spring 30 (e.g., solenoid actuated), and a slider mechanism 32. The rotor 26 rotates (such as by way of a shaft drive) causes oil to be sucked into the pump 20 through the inlet and pushed out of the pump through the outlet 24. The spring 30 moves the slider mechanism 32 and changes the eccentricity of the rotor 26 which determines the oil-pressure level at the pump output. The outlet 24 is in fluid communication with the outlet-port tube 16 illustrated in FIG. 1. Because of the relative “straight” design of the vanes 28, variable-displacement oil pumps often create rapid transitions from low pressure to peak pressure and more ripples in the oil pressure pulses. For instance, FIG. 3 depicts a line graph of pressure readings against crank angles in a system that utilizes a variable-displacement oil pump (or some other noisy pump) and that does not include the present invention. In comparison, FIG. 4 depicts a line graph of pressure readings against crank angles in a system that utilizes a quiet oil pump. A comparison of Line A in FIG. 3 and Line B in FIG. 4 depicts a more rapid transition from lower to peak pressure in the noisy oil pump (e.g., variable-displacement oil pump), absent the present invention. In some cases, the more rapid increase in oil pressure associated with a noisy oil pump translates into excessive whine noises at the critical pump orders (i.e. harmonics of the primary pump order). Referring briefly to FIG. 5A, a bar graph is depicted that shows a comparison of noise levels of a noisier oil pump (e.g., variable-displacement oil pump) and a quieter oil pump (e.g., some fixed-displacement oil pumps). FIG. 5A illustrates that the overall noise level of a noisy oil pump is often 5 to 10 dB higher when the pump does not include the present invention. For illustrative purposes, FIG. 5B includes a line graph showing pressure readings against crank angle in both a noisy pump that has not been modified (FIG. 3) and a noisy pump that has been modified to include an embodiment of the present invention. FIG. 5B illustrates that the present invention can reduce the rate of pressure increase and ripples. Referring now to FIG. 6A, an embodiment of the present invention is depicted in which a noise-reduction mechanism 18 is coupled to the outlet tube 16. The noise-reduction mechanism, or parts thereof, might also be referred to as a “muffler” in this description. The noise-reduction mechanism includes a series of communication channels 34A-D coupled directly to a reservoir 36. Although only a handful of the channels are labeled with numerical identifiers in the figures, embodiments of the invention are not limited to those labeled channels. In addition, although FIG. 6A depicts the communication channels as tubular structures, in other embodiments, the communication channels are formed by drilling holes in an at least partially solid block. In an embodiment of the present invention, each of the channels 34A-D includes a respective first end 38 for communication with an oil-pump outlet tube 16 and a respective second end 40 for communication with the reservoir 36. In addition, in FIG. 6A, the channels 34 are arranged such that axes 42 and 44 of the channels are substantially parallel to one another. However, the communication channels might be angled relative to one another in other embodiments of the present invention to tune the operation of the noise-reduction device. The reservoir 36 includes a hollow tubular structure that is capped at both ends. In operation, the channels 34A-D and the reservoir 36 function to reduce noise originating from oil pulsations. As depicted in FIGS. 6A, 6B, and 7, in one embodiment the channels include a first row (e.g., Row A-50) and a second row (e.g., ROW B-52) that might be substantially parallel to one another. In addition, the volume of the reservoir, as well as the length, diameter, number, spacing, and orientation of the channels 34A-D are modifiable to tackle specific frequency ranges of noise. In one embodiment, each of the channels 34A-D includes a diameter 54 of about 3.175 mm. In a further embodiment, each channel in the first row (e.g., 34B) is spaced apart from an adjacent channel in the first row (e.g., 34C) by a distance 56 of about 9.21 mm, and is spaced apart from an adjacently aligned channel (e.g., 34D) in the second row by a distance 58 of about 7.41 mm. In addition, a channel 34B that is outermost in a row is spaced apart from an end of the reservoir tube a distance 61 about 7.6 mm. Each channel is spaced apart from an adjacent edge of the reservoir a distance 63 of approximately 6.3 mm. In a further embodiment, the first row of channels includes nine channels, and the second row of channels includes nine channels. The reservoir is also tunable to control specific frequency ranges, such as by modifying a tube length 60 and a shape. For instance, in one embodiment, the tube includes a length 60 of approximately 90 mm. In addition, a shape of the reservoir includes a round wall 62 and a flat wall 64 to which the channels are connected. The round wall 62 and flat wall 64 are coupled to form a tube, which is capped on each end. As depicted in FIGS. 6A-6C, the round or curved wall 62 is not a complete circle, but instead includes an arc of a circle, which includes an inside diameter of about 19 mm. In addition, the flat wall 64 includes a width 65 of about 20 mm and a length 60 of about 90 mm. The noise-reduction device 18 might be coupled to an outlet tube 16 in various manners. For instance, referring to an embodiment depicted in FIGS. 6B and 6C, a block 66 is affixed (e.g., welded) to an underneath side 70 (i.e., surface) of the outlet tube 16. Then, a series of holes (e.g., 68) are drilled from a bottom of the block 66, through the block 66 and through a wall of the outlet tube 16, and in a pattern that corresponds with the hole pattern for the noise-reduction device and with holes drilled in the flat wall 64 of the reservoir 62. The reservoir 62 is then affixed (e.g., welded) to the block 66. The holes (e.g., 68) that are drilled in the block 66 establish a fluid connection between the oil-pump outlet tube and the reservoir 62. For illustrative purposes, FIG. 6C depicts the channels in ghost view to illustrate that the channels are formed in the block 66 when the reservoir 62 is attached. Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the scope of the claims below. Embodiments of our technology have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to readers of this disclosure after and because of reading it. Alternative means of implementing the aforementioned can be completed without departing from the scope of the claims below. Certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. |
