BACKGROUND

[001] The present disclosure relates to vehicle braking systems, and more particularly to a fluid reservoir construction for an integrated power brake unit (IPB). The IPB includes a pressure unit having both a brake booster (e.g., an electromechanical booster) and a brake master cylinder. The pressure unit supplies pressurized brake fluid to one or more brake circuits that contain one or more wheel cylinders to apply braking force to a wheel. The brake fluid reservoir of the IPB stores the brake fluid, and makes the brake fluid available to the pressure unit under all driving conditions via ports formed in a bottom surface of the brake fluid reservoir. Brake function may be lost in certain situations in which brake fluid outlet ports of the reservoir are exposed to air. For example, situations in which brake fluid within the reservoir may migrate away from the ports can include some dynamic conditions due to vehicle acceleration or deceleration, or conditions in which the vehicle is parked or operated at a severe inclination. Thus, it is desirable to provide a brake fluid reservoir having a construction that prevents brake fluid from migrating away from the ports, regardless of vehicle conditions.

SUMMARY

[002] In some aspects, a brake fluid reservoir for a vehicle is provided having a construction that prevents brake fluid (e.g., the liquid within the reservoir) from migrating away from the ports such as may occur when a vehicle experiences certain dynamic conditions such as acceleration or deceleration, and/or is parked or operated at a severe inclination. In some embodiments, the reservoir is part of an IPB that also includes an input rod operable to receive a driver braking input force, a pressure unit operable to provide pressurized fluid for braking in response to the driver braking input force, and a controller that controls the flow of pressurized fluid within the brake system via valves.

[003] The reservoir is segregated into three portions that are arranged serially along a reservoir longitudinal axis that is aligned with the vehicle forward driving direction. The three portions include a first chamber, also referred to as a wear compensation chamber, that is disposed at a first end of the reservoir and includes a fill opening, a second chamber, also referred to as a functional chamber, that is disposed at an opposed or second end of the reservoir and includes ports that communicate with the IPB, and a separator that is disposed between the first chamber and second chamber. The separator is separated from the first and second chambers via partitions. The separator is free of moving parts and defines a fluid passage that follows a labyrinth passage. The labyrinth fluid passage serves to prevent brake fluid (e.g., liquid) from migrating from the functional chamber including the ports and into the wear compensation chamber under certain conditions described below. In addition, the separator, including the labyrinth fluid passage, allows air (e.g., gas) to escape the functional chamber after the certain conditions described above have ended. The reservoir can be compared to some conventional brake fluid reservoirs that include flow restriction devices such as valves, flaps, etc. to control fluid migration. Such restriction devices often include moving parts which are relatively expensive and may malfunction. In addition, such devices may provide only time based protection, and/or may create volumes with separation (e.g., blind spots) between ports and the fluid level monitoring mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[004] Fig. 1 is a side view of an integrated power brake unit including a brake fluid reservoir.

[005] Fig. 2 is a schematic diagram of the vehicle brake hydraulic system including the integrated power brake unit and the reservoir of Fig. 1.

[006] Fig. 3 is a top perspective view of the reservoir of Fig. 1.

[007] Fig. 4 is a bottom perspective view of the reservoir of Fig. 1.

[008] Fig. 5 is a perspective cross sectional view of the reservoir of Fig. 1 as seen along line 5—5 of Fig. 3.

[009] Fig. 6 is a cross sectional view of the reservoir of Fig. 1 as seen along line 6— 6 of Fig. 3.

[0010] Fig. 7 is an enlarged view of a portion of Fig. 6 illustrating the separator in detail.

[0011] Figs. 8A-8D illustrate relative top side and bottom side heights for various locations along the reservoir longitudinal axis, where Fig. 8A is a cross sectional view of the reservoir as seen along line 8A— 8A of Fig. 3, Fig. 8B is a cross sectional view of the reservoir as seen along line 8B— 8B of Fig. 3, Fig. 8C is a cross sectional view of the reservoir as seen along line 8C— 8C of Fig. 3, and 8D is a cross sectional view of the reservoir as seen along line 8D— 8D of Fig. 3.

[0012] Fig. 9 is a side view of the reservoir of Fig. 1 oriented at an angle -Θ that is much less than a predetermined reservoir angle a, where the angles Θ and a are measured relative to a horizontal plane P, and illustrating retention of brake fluid (represented by hatching and stipples) in the second chamber by the separator for angles Θ less than the predetermined reservoir angle a.

[0013] Fig. 10 is a perspective view of a reservoir oriented at the angle Θ illustrated in Fig. 1, in which a top portion of the reservoir is omitted to permit a view of an interior of the reservoir, and in which the liquid within the reservoir has shifted such that an angle γ of an axis aligned with the surface of the liquid within the reservoir 30 is greater than a predetermined liquid angle β. In Fig. 10, the angles γ and β are measured relative to a longitudinal axis of the reservoir that is aligned with a bottom side of the reservoir, and Fig. 10 illustrates the retention of brake fluid (represented by hatching and stipples) in the second chamber by the separator for angles γ greater than the predetermined liquid angle β.

DETAILED DESCRIPTION

[0014] Referring to Figs. 1 and 2, an IPB unit 10 includes a housing 12 that contains a pressure unit 8 having at least one of a brake booster (not shown) and a brake master cylinder (not shown) for supplying pressurized brake fluid to one or more brake circuits, which in turn contain one or more wheel cylinders 8 that apply braking force to a wheel (e.g., squeeze a brake disc fixed to the wheel). The IPB unit 10 further includes an electronic controller 22 and a series of electronically-controlled valves. The controller 22 is coupled to the valves, and is programmed to carry out anti-lock braking (ABS) performance strategy and/or electronic stability control (ESC) strategy. An electric motor 18 is coupled to the housing 12 and has an output inside the housing 12 operable to run at least one pump to generate a flow of pressurized brake fluid. The IPB unit 10 also includes a brake fluid reservoir 30 that is connected to the pressure unit 8 via ports 53, 54, 55 formed in a bottom side 36 of the reservoir 30. The reservoir 30 is operable to store a quantity of hydraulic brake fluid to ensure that the braking circuits have a reserve quantity of fluid to draw from during braking operations. In addition, the reservoir 30 has a construction that prevents brake fluid from migrating away from the ports 53, 54, 55, regardless of vehicle conditions, as discussed in detail below.

[0015] Fig. 1 illustrates the orientation of the IPB unit 10 as installed in a vehicle that is supported on level ground. The IPB unit 10 has a defined orientation for mounting within a vehicle as defined by a brake input rod 14 that extends in a rear direction R and is angled downward with respect to the horizontal. In use, the IPB unit 10 is mounted via an adaptor plate 28 in the engine bay or under-hood area of the vehicle near or on the dash wall, with the brake input rod 14 extending toward a cabin space of the vehicle so that the brake input rod 14 is coupled to a driver-actuated brake pedal 24. Opposite the rearward direction R is a forward direction F, which is consistent with a normal forward travel direction of the vehicle. The description herein of the IPB unit 10 includes terms such as upper, lower, front, forward, rear, rearward, over, under, top, bottom and lateral which are used with reference to the orientation of the IPB unit 10 as illustrated in Fig. 1. These terms are relative and are not intended to be limiting, and it is understood that the IPB unit 10 and reservoir 30 may be used in other orientations as required by the specific application.

[0016] The reservoir 30, which stores brake fluid and supplies it to the pressure unit 8, is mounted to an upper side of the IPB unit housing 12 so that it overlies the housing 12. The shape of the reservoir 30 is dictated by specific vehicle packaging constraints. For example, in some embodiments, the IPB unit 10 may be designed in such a way that the reservoir 30 is placed in very close proximity to the vehicle dash so that the available vertical package space for the reservoir 30 within the vehicle is significantly reduced. As a result, the reservoir 30 has an irregular shape that is elongated in the front-to-rear direction relative to some conventional brake fluid reservoirs.

[0017] Referring also to Figs. 3 and 4, the reservoir 30 has the form of a hollow shell, and includes a first end 31 , a second end 32 that is opposed to the first end 31 , and a longitudinal axis 37 that extends between the first end 31 and the second end 32. When viewed in top plan view, the longitudinal axis 37 is generally aligned with the front-to-rear axis of the vehicle, and the reservoir 30 is mounted on the IPB unit housing 12 such that the first end 31 is forward relative to the second end 32. When viewed in side plan view (Fig. 1.), the longitudinal axis 37 is oriented at an angle Θ relative to a horizontal plane P such that the first end 31 is above the second end 32. For example, in some embodiments, the angle Θ may be about 15.5 degrees.

[0018] The reservoir 30 has four sides that extend between the first end 31 and the second end 32. In particular, the reservoir 30 includes a first side 33 and a second side 34 that are mutually spaced apart and provide the lateral sides of the reservoir 30 in the orientation of the reservoir 30 shown in Fig. 1. In addition, the reservoir 30 includes a third side 35 that provides the top side of the reservoir 30 and a fourth side 36 that provides a bottom side of the reservoir 30 in the orientation of the reservoir 30 shown in Fig. 1. Thus, when the reservoir 30 is mounted on the IPB unit housing 12, the fourth, or bottom, side 36 faces the IPB unit housing 12, and the third, or top, side 35 is opposed to the bottom side 36 and faces the vehicle hood.

[0019] The reservoir 30 is secured to the IPB unit housing 12 via a front bracket 82 and a rear bracket 80. The front bracket 82 protrudes from the reservoir bottom side 36 an engages a front facing surface of the IPB unit housing 12. The rear bracket 80 protrudes rearwardly from the reservoir second end 32, and engages the adaptor plate 28 via a pin 83 that passes through openings 81 in the rear bracket 80.

[0020] Referring to Figs. 5-7, the internal space of the reservoir 30 is segregated into three separate portions that are arranged serially along the longitudinal axis 37. The three portions include a first chamber 38, a second chamber 39 and a separator 40 that is disposed between the first chamber 38 and the second chamber 39 and separates the first chamber 38 from the second chamber 39.

[0021] The first chamber 38, also referred to as a wear compensation chamber, is disposed at the first end 31 of the reservoir 30 and includes a fill opening 59 through which brake fluid is added to the reservoir 30. The fill opening 59 is formed in the top side 35 at a location that is closer to the first end 31 than to the separator 40, and is closed by a vented fill cap 66. The outer surface of the reservoir second side 34 includes chevrons that indicate a maximum and minimum fill level of the reservoir 30. In use, the reservoir 30 is typically filled to the maximum fill level at the time of manufacture. However, even with no brake system leakage, the level of brake fluid within the reservoir 30 typically goes down due to wear of brake system components such as brake pads and rotors. Thus, the first chamber 38 is used to contain the volume of brake fluid needed to compensate for component wear.

[0022] The second chamber 39, also referred to as a functional chamber, is disposed at the second end 32 of the reservoir 30, and is used to contain brake fluid required to operate the vehicle brake hydraulic system. The second chamber 39 includes first, second and third outlet ports 53, 54, 55 that are formed in the bottom side 36 and that communicate with the IPB unit 10. The first outlet port 53 and the second outlet port 54 are in communication with respective inlet ports of the master cylinder 20. The third outlet port 55 is in communication with the booster 16. The second chamber 39 is segregated into sub-chambers 60, 61 , 62, and each outlet port 53, 54, 55 is disposed in a unique sub chamber.

[0023] During normal operation in which the IPB unit 10 provides brake -by-wire braking, fluid drawn into the housing 12 by the motor-driven pump for braking is drawn in through the third outlet port 35. This is indicative of an open system (or "open circuit") configuration where the active boosting circuit and stability controlled circuit is always in fluid communication with the reservoir 30, as opposed to a closed system configuration (or "closed circuit") in which the reservoir 30 and the circuit are fluidly isolated when activated in its normal operation. Non- limiting, detailed examples of braking systems with an open circuit configuration can be found in U.S. Patent 9,315,182. During operation of the vehicle, it is important to ensure that inlets into the housing 12 are continuously bathed in fluid to prevent air from being entrained and introducing compressibility to the braking circuits. This is normally achieved by the design of the reservoir 30 and the placement of the reservoir outlet ports 53, 54, 55 to ensure that the reservoir outlet ports 53, 54, 55 cannot lose fluid coverage at any point during an established set of design parameters, which can include maximum design vehicle deceleration or lateral acceleration. However, with increased packaging constraints placed on the reservoir 30, this proves to be increasingly difficult.

[0024] The separator 40 is configured to ensure that the outlet ports 53, 54, 55 are continuously covered with brake fluid. The separator 40 is disposed between the first chamber 38 and the second chamber 39, and is separated from the first and second chambers 38, 39 via first and second partitions 42, 43. The first and second partitions 42, 43 cooperate with the first side 33 of the reservoir 30 to define a fluid passage 41 that provides a fluid path between the first chamber 38 and the second chamber 39.

[0025] In particular, the separator includes a first partition 42 that is shared in common with the first chamber 38 and a second partition 43 that includes a portion 43a that is shared in common with the second chamber 39.

[0026] The first partition 42 includes a first transverse portion 42a that intersects the reservoir first side 33 and extends in a direction perpendicular to the longitudinal axis 37, and a second transverse portion 42c that is spaced apart from the first transverse portion 42a along the longitudinal axis 37 and is spaced apart from the reservoir first and second sides 33. In addition, the first partition 42 includes a longitudinal portion 42b that extends longitudinally between, and joins, the first transverse portion 42a to the second transverse portion 42c.

[0027] The second partition 43 includes a third transverse portion 43a that is perpendicular to the longitudinal axis 37, and is disposed between the second transverse portion 42c and the reservoir second end 32. The third transverse portion 43a is spaced apart from the reservoir first and second sides 33, 34. The second partition 43 includes a longitudinal portion 43b that is disposed between, and is spaced apart from, the reservoir first side 33 and the longitudinal portion 42b of the first partition 42. The longitudinal portion 43b extends generally longitudinally along a curved path that mirrors the curved shape of the reservoir first side 33 in that vicinity. Here, the first transverse portion 42a of the first partition 42 and the third transverse portion 43a of the second partition 43 each extend in a direction perpendicular to the longitudinal axis 37, and define the longitudinal outer boundaries of the separator 40.

[0028] The partitions 42, 43 are configured so that the fluid passage 41 follows a labyrinth path. The fluid passage 41 includes a first portal 50 at one end that permits the fluid passage 41 to communicate with the second chamber 39, and a second portal 52 at an opposed end that permits the fluid passage 41 to communicate with the first chamber 38. The first portal 50 is formed between the third transverse portion 43a and the reservoir first side 33, and opens facing the reservoir second end 32. The second portal 52 is formed between the third transverse portion 43a and the second transverse portion 42c, and opens facing the reservoir second side 34. [0029] The fluid passage 41 includes a first portion 46 that extends longitudinally between the first portal 50 and the first transverse portion 42a. The fluid passage 41 includes a second portion 47 that extends between the first transverse portion 42a and the third transverse portion 43a. The fluid passage 41 includes a third portion 48 that is curved and provides a connection between the first portion 46 and the second portion 47. The first, second, and third portions 46, 47, 48 together define a U-shaped structure in which the first portion 46 and the second portion 47 share a common partition, e.g. the longitudinal portion 43b of the second partition 43. The U- shaped structure is disposed between the reservoir first side 33 and a longitudinal midline 56 of the reservoir 30, where the midline 56 is parallel to the longitudinal axis 37 and is disposed midway between the reservoir first side 33 and the reservoir second side 34. In addition to the U-shaped structure, the fluid passage 41 includes a fourth portion 49 that extends in a direction parallel to the third transverse portion 43a. One end of the fourth portion 49 is connected to the third portion 48, and an opposed end of the fourth portion 49 defines the second portal 52. In addition, the third transverse portion 43a of the second partition 43 is common to the second chamber 39 and the fourth portion 49.

[0030] The reservoir 30 includes a fluid sensor 68 that detects a depth of liquid in the second chamber 39, and outputs a corresponding signal to the controller 22. The fluid sensor 68 is disposed in the second chamber 39 at a location adjacent to the first portal 50 of the fluid passage 41. In the illustrated embodiment, the fluid sensor 68 includes is a float switch that includes a float 69. However, it is understood that other appropriate liquid level detecting sensors may be substituted for the float switch.

[0031] Both the first chamber 38 and the second chamber 39 include internal reinforcing ribs 65 that extend between the top and bottom sides 35, 36, and provide structural reinforcement of the reservoir 30. Each of the internal reinforcing ribs 65 includes a free end 71 and a fixed end 72. The fixed end 72 is integrally formed with one of the reservoir first side 33 or the reservoir second side 34, and the free end 71 is opposed to the fixed end 72 and spaced apart from the respective side 33, 34. The internal reinforcing ribs 65 are oriented at an angle relative to the respective side 33, 34 such that the free end 71 is closer to the reservoir first end 31 than is the fixed end 72. By providing the internal reinforcing ribs 65 at an angle, movement toward the first end 31 of air bubbles that are trapped by the ribs 65 is promoted. [0032] In addition to the internal reinforcing ribs 65, the reservoir 30 includes external reinforcing ribs 63, 64 formed on an outer surface thereof. For example, the reservoir 30 includes external reinforcing ribs 63 formed on the top side 35 in a region overlying the separator 40. In addition, the reservoir 30 includes external reinforcing ribs 64 formed on the bottom side 36 in a region underlying the separator 40. The external reinforcing ribs 63, 64 extend longitudinally between the first chamber 38 and the second chamber 39.

[0033] As previously discussed, the reservoir 30 has an irregular shape. As a result, a depth of the reservoir 30 in a portion of the reservoir 30 corresponding to the separator 40 is less than a depth of the reservoir 30 in portions of the reservoir 30 corresponding to the first chamber 38 and the second chamber 39. As used herein, the term "depth" refers the distance between the top side 35 and the bottom side 36.

[0034] When the reservoir 30 is installed in a vehicle that is supported on a level surface, the reservoir 30 is configured such that the top wall 35 is above the bottom wall 36 with respect to a vertical axis aligned with gravity. In addition, the top wall 35 in the portion of the reservoir 30 corresponding to the separator 40 is level with or above the top wall 35 in the portion of the reservoir 30 corresponding to the second chamber 39. Still further, the bottom wall 36 in the portion of the reservoir 30 corresponding to the separator 40 is level with or below the bottom wall 36 in the portion of the reservoir 30 corresponding to the first chamber 38.

[0035] When the reservoir 30 is installed in a vehicle that is supported on a level surface, the top and bottom walls 35, 36 are configured such that brake fluid disposed in the reservoir 30 flows from the first end 31 to the second end 32, and air disposed in the reservoir 30 flows from the second end 32 to the first end 31, as will now be described in more detail.

[0036] Referring to Figs. 1 and 8A-8D, for the orientation of the reservoir 30 illustrated in Fig. 1, which corresponds to the orientation of the reservoir 30 as installed in a vehicle that is supported on a level surface, the height hi of the bottom side 36 at the first portal 50 is less than the height h2 of the bottom side 36 at the second portal 52, where the term "height" refers to the distance between the element and a horizontal plane P passing through a center of the rear bracket opening 81. Thus, the bottom side 36 within the fluid passage 41 slopes downward from the second portal 52 to the first portal 50, facilitating movement of brake fluid to from the first chamber 38 to the second chamber 39.

[0037] In addition, for the orientation of the reservoir 30 illustrated in Fig. 1 , the height h3 of the top side 35 at the first portal 50 is less than the height h4 of the top side 35 within the separator third portion 48, and the height h4 of the top side 35 within the separator third portion 48 is less than the height h5 of the top side 35 at the second portal 52. To achieve the relative heights h3, h4, h5 of the top side 35, it can be seen in Fig. 5 that top side 35 in the vicinity of the fluid path third portion 48 is formed to be recessed relative to adjacent portions of the top side 35 that overlie the first chamber 38 and overlie the second portal 52. Thus, the top side 35 within the fluid passage 41 slopes upward from the first portal 50 to the second portal 52, facilitating movement of air from the second chamber 39 to the first chamber 38.

[0038] Referring to Fig. 9, the labyrinth path of the fluid passage 41 defined by the separator 40 is free of moving parts and advantageously permits brake fluid flow between the first chamber 38 and the second chamber 39 (e.g., permits liquid flow from the first chamber 38 to the second chamber 39, and from the second chamber 39 to the first chamber 38) when the angle Θ of the longitudinal axis 37 relative to a horizontal plane P is greater than a predetermined reservoir angle a. In addition, the labyrinth path of the fluid passage 41 prevents brake fluid flow from the second chamber 39 to the first chamber 39 (e.g. retains liquid in the second chamber 39) when the angle Θ of the longitudinal axis 37 relative to a horizontal plane P is less than the

predetermined reservoir angle a. This occurs, at least in part, due to brake fluid being trapped within the U-shaped portion of the fluid passage 41 when the angle Θ of the longitudinal axis 37 relative to a horizontal plane P is less than the predetermined reservoir angle a, and forming an air tight seal therein. That is, despite the presence of brake fluid in the second chamber 39 that results in an elevation head at the first portal 50, the brake fluid is trapped within the fluid passage 14 due to the presence of air disposed in the first chamber 38, which applies an atmospheric pressure at the second portal 52. The labyrinth shape of the fluid passage 41 prevents the air within the first chamber 39 from migrating upward into the second chamber 39.

[0039] The predetermined reservoir angle a at which the fluid becomes trapped within the fluid passage 41 depends on the geometry of the separator 40, for example the depth D of the separator at the portal 52 (Fig. 8C) and the length L of the separator 40 (Fig. 7), where the depth D of the separator at the portal 52 corresponds to the height h5 minus the height h2, and the length L of the separator is the longitudinal distance between a tip 43d of the longitudinal portion 43b and the second transverse portion 42c, and thus will depend on the requirements of the specific application. In particular, the predetermined reservoir angle a at which the fluid becomes trapped within the fluid passage 41 corresponds approximately to [ arctan (D) / (L) ]. In the illustrated embodiment, for example, the predetermined reservoir angle a is about (-1.2) degrees relative to the horizontal plane P.

[0040] Thus, the separator 40 is configured such that when the reservoir 30 is oriented at an angle that is less than the predetermined reservoir angle a, the brake fluid is trapped within the fluid passage 41 and cooperates with the air trapped in the first chamber 38 to prevent fluid residing in the second chamber 39 from passing through the fluid passage 41 and into the first chamber 38.

[0041] Referring to Fig. 10, in addition to serving as a fluid trap when the reservoir 30 is oriented at an angle that is less than the predetermined reservoir angle a, the separator 40 can also serve as a fluid trap when the vehicle including the IPB unit 10 experiences certain conditions that result in a shift of the liquid within the reservoir 30 such that an angle γ of an axis 92 aligned with the surface of the liquid within the reservoir 30 is greater than a predetermined liquid angle β. In one example, such a liquid shift may occur dynamic conditions such as vehicle acceleration or deceleration. In another example, such a liquid shift may occur when the vehicle is parked or operated at a severe inclination.

[0042] The predetermined liquid angle β at which the fluid becomes trapped within the fluid passage 41 depends on the geometry of the separator 40, for example the depth of the separator in the third portion 48 and the length L of the separator 40 (Fig. 7), and thus will depend on the requirements of the specific application. In particular, the predetermined liquid angle β corresponds to an angle at which a surface of the liquid within the reservoir 30 is in contact with the top side 35 within the separator third portion 48 and in contact with the bottom side 36 along the longitudinal extent of the separator first portion 46. In the illustrated embodiment, for example, the predetermined liquid angle β is about 16.7 degrees relative to the longitudinal axis 37.

[0043] When the angle of the reservoir 30 is less than the predetermined reservoir angle a, and/or when the liquid within the reservoir 30 shifts within the reservoir 30 such that an angle of an axis 92 aligned with the surface of the liquid within the reservoir 30 is greater than a predetermined liquid angle β, the separator 40 including the fluid passage 41 having the labyrinth shape serves to prevent brake fluid from migrating into the first chamber 38 (e.g., the chamber designated for storing sufficient brake fluid to compensate for wear within the brake system) and away from the second chamber 39 which provides fluid to the fluid ports 53, 54, 55 and includes the fluid sensor 68. For this reason, fluid level monitoring within the reservoir 30 is more accurate than in some conventional brake fluid reservoirs that do not include the separator 40. In addition, the separator 40 allows air to escape from the second chamber 39 after the dynamic conditions have ended or the vehicle is no longer severely inclined.

[0044] The separator 40 in the reservoir 30 allows for the active port 55 to be fully covered with brake fluid at all times during normal operation of the vehicle. In particular, the separator 40 allows for a top-mounted reservoir solution with the packaging constraints of the reservoir 30 as shown.

[0045] The reservoir 30 as illustrated in Figs. 1-9 is configured to be used, for example, in vehicles in which the steering wheel is positioned on the left side of the vehicle with respect to the vehicle forward direction (e.g. a "left hand drive vehicle"), but is not limited to being used in a left hand drive vehicle. For example, an alternative embodiment reservoir 130 (Fig. 10) may be configured for use in a "right hand drive vehicle" in which the steering wheel is positioned on the right side of the vehicle with respect to the vehicle forward direction. The alternative embodiment reservoir 130 is very similar to the reservoir 30 described above with respect to Figs. 1-9, particularly with respect to the location and function of the first chamber 28, the second chamber 39, and the separator 40. The alternative embodiment reservoir 130 differs from the reservoir 30 described above with respect to Figs. 1 -9 with respect to an angle of the fluid sensor 68 and float 69 relative to the longitudinal axis 37. In addition, curvatures of the first and second sides 33, 34 are modified to accommodate the presence of ancillary devices within the vehicle in the vicinity of the IPB unit 10.

[0046] Although the reservoir 30 is described here for use with the IPB unit 10, it is

contemplated that the reservoir 30 may be used with other types of pressure units, including, but not limited to, those including only master cylinders and those including only boosters.

[0047] Selective illustrative embodiments of the IPB unit and brake fluid reservoir are described above in some detail. It should be understood that only structures considered necessary for clarifying these devices have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the IPB unit and brake fluid reservoir, are assumed to be known and understood by those skilled in the art. Moreover, while working examples of the IPB unit and brake fluid reservoir have been described above, the IPB unit and brake fluid reservoir are not limited to the working examples described above, but various design alterations may be carried out without departing from the devices as set forth in the claims.