WO2023018934A1

WO2023018934A1 - Transmission oil cooler and bypass block system

Info

Publication number: WO2023018934A1
Application number: PCT/US2022/040158
Authority: WO
Inventors: Lars Stenvall
Original assignee: Polestar Performance Ab; Polestar Automotive Usa Inc.
Priority date: 2021-08-12
Filing date: 2022-08-12
Publication date: 2023-02-16

Abstract

A transmission oil cooling system including a transmission oil cooler and a transmission oil cooler bypass block coupled to the transmission oil cooler for directing a only portion of the coolant through the transmission oil cooler, while allowing the remaining portion of the coolant to bypass the transmission oil cooler. At an outlet end of the bypass block, the portion passing through the transmission oil cooler is combined with the portion passing through the bypass block where it exits the bypass block and is either disposed or returned to a cooling circuit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the benefit of U.S. Provisional Application No. 63/260,189 filed August 12, 2021, the disclosure of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present disclosure relates to cooling of transmission oil, and more particularly to a system for cooling transmission oil including a bypass block coupleable to a transmission oil cooler. BACKGROUND Vehicles, including electric vehicles (EVs), are equipped with transmissions that provide different speed ratios between an engine or motor and drive axles. Lubricants, including oil, fulfill a crucial function by making vehicles safer and more efficient, starting with lowering fuel consumption. Lubricating an internal combustion engine is very different from the same job for an EV motor. The former needs both oil to minimize engine friction and transmission fluid. Electric vehicles experience significant fluctuations in power flows and high motor speeds of up to 15,000 or more revolutions a minute. Due to the high rate of revolution, the transmission and thus oil is circulated to cool the transmission components. If the oil becomes too agitated and warm, it can foam or coalesce from the creation of small air bubbles. Foaming in gearboxes causes problems because foam does not pump or circulate, and it reduces the effectiveness of the lubricant, resulting in accelerated gear wear, gear slipping, and overheating. To prevent or reduce the occurrence of foaming of oil in the EV’s transmission, transmission oil is constantly moved through a transmission oil cooler secured to the transmission to cool or draw heat from the transmission oil before the oil is returned to the transmission. Conventional transmission oil coolers are heat exchangers in which a coolant, such as water, enters the cooler via an inlet and flows through a fluid channel proximate and countercurrent to the oil’s flow path to absorb heat from the oil before exiting at an outlet. The coolant can be sourced from another coolant circuit, such as coolant from the cooling circuit of an electric motor. However, a flow rate of coolant needed to sufficiently cool an electric motor is much higher than a flow rate of coolant needed to cool the oil. This can cause unwanted backpressure in the system, thereby reducing cooling efficiencies. There remains a need to cool the transmission oil without creating an excess backpressure environment within the cooling system. SUMMARY Embodiments according to the current disclosure relate to a transmission oil cooling system including a transmission oil cooler and a transmission oil cooler bypass block coupled to the transmission oil cooler for directing a only portion of the coolant through the transmission oil cooler, while allowing the remaining portion of the coolant to bypass the transmission oil cooler. At an outlet end of the bypass block, the portion passing through the transmission oil cooler is combined with the portion passing through the bypass block to be recycled within the vehicle. In an embodiment, a transmission oil cooler bypass block includes structure defining an inlet channel having an inlet cross-section at a first end of the bypass block, structure defining an outlet channel having an outlet cross-section similar to the inlet cross-section at a second end of the bypass block, and a bypass channel or tube positioned between and in fluid communication with the inlet channel and the outlet channel. The bypass tube has a bypass tube cross-section less than the inlet and outlet diameters. In various embodiments, the inlet cross-section, outlet cross-section and bypass tube cross-selection can be selected from one or more of circular, ovoid, square, triangular and rectangular cross-sections and the like. In embodiments where the inlet cross- section, outlet cross-section and bypass tube cross-selection are circular cross-sections, the inlet and outlet cross-sections can each have a diameter greater than a diameter of the bypass tube cross- section. The inlet channel is in fluid communication with an inlet of the transmission oil cooler, and is coupled to and in fluid communication with a coolant inlet and coolant source. Similarly, the outlet channel is in fluid communication with an outlet of the transmission oil cooler, and is coupled to and in fluid communication with a coolant outlet. As coolant is introduced into the inlet channel, due to the smaller diameter of the bypass tube, a portion of the coolant is forced into the transmission oil cooler while a remaining portion flows through the bypass tube. The portion of coolant moving through the transmission oil cooler exits the cooler and flows into the outlet channel of the bypass block to recombine with coolant moving through the bypass block. The coolant then exists the bypass block via the coolant outlet to be returned to the coolant circuit. In one embodiment, the bypass tube’s cross-sectional area is one-half of the cross-sectional area of the inlet and outlet channels such that one-half of the coolant moves through the transmission oil cooler while the other one-half moves through the bypass tube. In other embodiments, the ratio of inlet/outlet channel to bypass tube cross-sectional areas is 1.5: 1; 2:1; 2.5: 1; 3:1; 3.5:1; 4:1; 4.5:1; or 5:1, or anywhere in between 1.5:1 to 5:1. In embodiments in which the inlet, outlet and bypass tube cross-sections are circular, the inlet and outlet cross-section have diameters greater than that of the bypass tube cross-section. In embodiments, the bypass block can be removable coupled to the transmission oil cooler via an O-ring sealed connection of the bypass block over the inlet and outlet channels, respectively, for removably coupling to a coolant inlet source or hose and a coolant outlet source or hose. The summary above is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The figures and the detailed description that follow more particularly exemplify these embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The disclosure can be more completely understood in consideration of the following detailed description of various embodiments of the disclosure, in connection with the accompanying drawings, in which: FIG.1A is a perspective view of a transmission oil cooling system including a transmission oil cooler with a bypass block coupled thereto, and with inlet and outlet pipes coupled to inlet and outlet channels, respectively, according to an embodiment of the disclosure; FIG.1B is a perspective view of the transmission oil cooler system of FIG.1A coupled to a transmission of an electric vehicle transmission; FIG.2 is a partially exploded view of the transmission oil cooling system of FIG.1A with the bypass block in cross-section; and FIG.3 is an exploded view of the transmission oil cooling system of FIG.1A. While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof shown by way of example in the drawings will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIGS.1A and 1B, a transmission oil cooling system 100 generally comprises a transmission oil cooler 102, and a bypass block 104 coupled to and over a coolant inlet 106 and a coolant outlet 108 of cooler 102. An inlet pipe or coupler 110 is coupled to an inlet channel side 111 of bypass block 104, and an outlet pipe or coupler 112 is coupled to an outlet channel side 113 of bypass block 104. Referring to FIG.1B, inlet coupler 110 is configured to be coupled to an inlet source 111, such as a hose, pipe, or other conduit. In this particular embodiment, inlet coupler 110 is coupled to conduit 114, which fluidly couples bypass block 104 to a coolant outlet 115 from an electric motor M. Outlet coupler 112 is configured to be coupled to an outlet conduit (not shown), which in turn is coupled to a coolant source to chill the coolant before returning to cool electric motor M. Referring now to FIG.2, bypass block 104 includes structure defining an internal channel therethrough. The channel includes inlet channel 116, outlet channel 118, and bypass channel or tube 120. In an embodiment, bypass tube 120 has a substantially circular bypass cross-section 120a having a bypass tube diameter, and inlet channel 116 and outlet channel 118 each have substantially circular inlet and outlet cross-sections 116a, 118a having inlet and outlet diameters larger than the bypass tube diameter of bypass tube 120. In some embodiments the diameter of inlet channel 116 and outlet channel 118 are substantially similar or equal, while in other embodiments they are different. For example, the inlet diameter of the inlet channel 116 may be larger or smaller than the outlet diameter of the outlet channel 118, while both the inlet and outlet diameters are larger than the bypass tube diameter of bypass tube 120. In alternative embodiments not shown, inlet cross-section 116a and/or outlet cross-section 118a and/or bypass cross-section 120a can have a non-circular cross section, such as, but not limited to ovoid, square, triangular, rectangular, or any of a variety of shapes, or combinations thereof. Regardless of the shape, the cross-sectional areas defined by the inlet and outlet cross-sections 116a, 118a will be larger than the bypass cross-section 120a. In the embodiment shown in FIG. 2, a cross-sectional area defined within each of inlet channel 116, bypass tube 120, and outlet channel 118 is substantially constant. In alternative embodiments not shown, the cross-sectional area of the inlet channel 116 and/or outlet channel 118 may taper, i.e. the cross-sectional area may gradually reduce proximate each end of bypass tube 120. In embodiments, in which the inlet and outlet cross-sections 116a, 118a are circular cross-sections, this tapered portion can be defined by reducing the diameter proximate each end of the bypass tube 120. As shown in FIGS. 2 and 3, bypass block 104 fits over coolant inlet 106 and a coolant outlet 108 of cooler 102. More specifically, and referring to FIG.3, structure defining an opening 122 in inlet channel 116 is configured to fit around coolant inlet 106, while structure defining an opening 124 in outlet channel 118 is configured to around coolant outlet 108. Further, sealing means, such as a gasket or O-ring (not shown) around each of coolant inlet 106 and coolant outlet 108 can be used to secure bypass block 104 to cooler 102 with a substantially leak-tight seal. Referring to FIG. 3, an outside diameter of inlet coupler 110 and outlet coupler 112 is substantially similar to and slightly smaller than a diameter of inlet channel 116 and outlet channel 118, respectively, thereby forming a friction fit when inserted into inlet channel 116 and outlet channel 118. Each coupler 110 and 112 include an annular flange 126 for limiting an insertion length into respective channel 116, 118, thereby forming a substantially leak-tight seal. As above, a gasket or O-ring (not shown) can be incorporated to ensure the seal is leak-proof. In embodiments, inlet coupler 110 and outlet coupler 112 may be formed of rubber or another elastomeric material, a rigid plastic or polymeric material, a metal material such as stamped aluminum, composites, or combinations thereof. Similarly, bypass block 104 can be formed of any of the above materials or combinations thereof. In use, bypass block 104 is positioned over and secured to transmission oil cooler 102 by positioning opening 122 over coolant inlet 106 and opening 124 over coolant outlet 108. Couplers 110 and 112 are inserted into and secured to inlet channel 116 and outlet channel 118. Couplers 110 and 112 are then coupled to a fluid inlet source and a fluid outlet source as described above with respect to FIG.1. A cooling fluid, such as water or water and one or more additives enters inlet channel 116 via coupler 110 at a flow rate. Due to the smaller bypass cross-section 120a of bypass tube 120 compared to inlet cross-section 116a of inlet channel 116, a portion of the incoming fluid stream is forced into coolant inlet 106 of transmission oil cooler 102, while a remaining volume of the fluid flows through bypass tube 120. The ratio of fluid that flows through the coolant inlet 106 of transmission oil cooler 102 to bypass tube 120 is proportional to the ratio of cross-sectional areas of inlet cross-section 116a to bypass cross-section 120a. In one embodiment, the bypass cross- section 120a of bypass tube 120 is one-half of the cross-sectional areas of inlet cross-section 116a and outlet cross-section 118a such that one-half of the coolant moves through transmission oil cooler 102 while the other one-half moves through bypass tube 120. In other embodiments, the ratio of fluid flow to inlet/outlet channel to bypass tube is 1.5: 1; 2:1; 2.5: 1; 3:1; 3.5:1; 4:1; 4.5:1; or 5:1, or anywhere in between 1.5:1 to 5:1. The fluid forced into the cooler moves through the cooler to cool the transmission oil, and then exits via coolant outlet 108 into outlet channel 118, to combine with fluid moving through bypass tube 120. The flow rate through inlet channel 116, bypass tube 120, outlet channel 118, and cooler 102 is substantially equal with little to no backpressure. In embodiments in which the inlet, outlet and bypass tube cross-sections 116a, 118a, 120a are circular, the variation in cross-sectional areas is accomplished by simply changing the diameter wherein the diameter of the inlet and outlet cross-sections 116a, 118a is greater than a diameter of the bypass tube cross-section 120a. In some embodiments, bypass block 102 is permanently coupled to transmission oil cooler 102. In other embodiments, bypass block 102 is can be coupled and uncoupled to transmission oil cooler 102 as desired. Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.

Claims

CLAIMS What is claimed is: 1. A fluid bypass block, comprising: a bypass channel defining a bypass cross-section; an inlet channel defining an inlet cross-section, the inlet channel further including an inlet coupler and an inlet opening, the inlet coupler fluidly coupled to a coolant source and the inlet opening fluidly coupled to a transmission oil cooler inlet; and an outlet channel defining an outlet cross-section, the outlet channel further including an outlet coupler and an outlet opening, the outlet coupler fluidly coupled to a coolant destination and the outlet opening fluidly coupled to a transmission oil cooler outlet, wherein a cross-sectional area of the bypass cross-section is less than a cross- sectional area of the inlet cross-section and the outlet cross-section such that a coolant flow into the inlet coupler is divided into a bypass flow through the bypass channel and a cooling flow though the inlet opening.

2. The fluid bypass block of claim 1, wherein the cross-sectional areas of the inlet cross-section and the outlet cross- section are equal.

3. The fluid bypass block of claim 1, wherein a ratio of the cross-sectional area of the inlet cross-section to the cross- sectional area of the bypass cross-section is between 1.5 : 1 and 5 : 1.

4. The fluid bypass block of claim 3, wherein the ratio of the cross-sectional area of the inlet cross-section to the cross-sectional area of the bypass cross-section is 2 : 1.

5. The fluid bypass block of claim 1, wherein the bypass cross-section, the inlet cross-section and the outlet cross-section all have a circular cross-section.

6. The fluid bypass block of claim 5, wherein the inlet and outlet circular cross-sections each have an inlet and outlet diameter respectively that is greater than a bypass diameter of the bypass circular cross-section.

7. The fluid bypass block of claim 1, wherein the bypass cross-section, the inlet cross-section and the outlet cross-section comprise a cross-sectional shape selected from ovoid, square, triangular and rectangular.

8. A transmission oil cooling system, comprising: a transmission oil cooler including a cooler inlet in fluid communication with a cooler outlet; and a bypass block including an inlet channel, a bypass channel and an outlet channel, the bypass channel fluidly coupled to the inlet channel and the outlet channel, the inlet channel fluidly coupled to the cooler inlet and the outlet channel fluidly coupled to the cooler outlet, wherein a coolant flow into the inlet channel is separated into a bypass flow and a cooler flow, and wherein the bypass channel has a bypass cross-section that is less than an inlet cross-section of the inlet channel and an outlet cross-section of the outlet channel so as control the volume of bypass flow through the bypass channel relative to the volume of the cooler flow.

9. The transmission oil cooling system of claim 8, wherein the inlet cross-section and the outlet cross-section are equal.

10. The transmission oil cooling system of clam 8, wherein a ratio of the inlet cross-section and outlet cross-section to the bypass cross-section is between 1.5 : 1 and 5 : 1.

11. The transmission oil cooling system of claim 10, where the ratio is 2 : 1.

12. The transmission oil cooling system of claim 8, wherein the bypass cross-section, the inlet cross-section and the outlet cross-section all have a circular cross-section.

13. The transmission oil cooling system of claim 12, wherein a diameter of the inlet cross- section and the outlet cross-section is greater than a diameter of the bypass cross-section.

14. The transmission oil cooling system of claim 8, wherein the bypass cross-section, the inlet cross-section and the outlet cross-section comprise a cross-sectional shape selected from ovoid, square, triangular and rectangular.

15. A method of avoiding excess backpressure in a transmission oil cooling system, comprising: attaching a bypass block to a transmission oil cooler; supplying a coolant flow into an inlet channel of the bypass block; dividing the coolant flow into a bypass flow and a cooler flow; directing the cooler flow into the transmission oil cooler; and recombining the bypass flow and the cooler flow in an outlet channel of the bypass block.

16. The method of claim 15, wherein the step of dividing the coolant flow further comprises: providing a bypass channel between the inlet channel and the outlet channel, wherein a bypass cross-section of the bypass channel is less than an inlet cross-section of the inlet channel and an outlet cross-section of the outlet channel.

17. The method of claim 15, wherein the step of providing the bypass channel further comprises: selecting a ratio of the inlet cross-section and the outlet cross-section relative to the bypass cross-section wherein the ratio is between 1.5 : 1 and 5 : 1.

18. The method of claim 17, wherein the ratio is 2 : 1.

19. The method of claim 17, wherein the inlet, outlet and bypass cross-sections are circular and wherein the step of selecting the ratio further comprises: selecting an inlet diameter, outlet diameter and bypass diameter of the inlet cross- section, outlet cross-section and bypass cross-section respectively, wherein the inlet and outlet diameters are greater than the bypass diameter.