CN112400077B

CN112400077B - Pneumatic actuator and pneumatic system comprising a pneumatic actuator

Info

Publication number: CN112400077B
Application number: CN201980044900.7A
Authority: CN
Inventors: 吉安马克·科波拉; 科迪·奥尔
Original assignee: Litens Automotive Partnership
Current assignee: Litens Automotive Partnership
Priority date: 2018-07-05
Filing date: 2019-07-05
Publication date: 2023-04-07
Anticipated expiration: 2039-07-05
Also published as: WO2020006646A1; CN112400077A

Abstract

In one aspect, a vacuum actuator for use in a vehicle vacuum system is provided that includes a housing, an output member, an inter-chamber valve member, a first membrane, a second membrane, a first membrane biasing member, and a second membrane biasing member. The actuator housing includes a first chamber and a second chamber. The first chamber can be fluidly connected to a first vacuum source. The first diaphragm is movable at a first selected pressure in the first chamber by a pressure differential across the first diaphragm against the first biasing member to move the inter-chamber valve member from the closed position to the open position. The second membrane biasing member urges the output member toward the second position. The second diaphragm is movable by a pressure differential across the second diaphragm at a second selected pressure in the second chamber to move the output member to the first position. The first selected pressure is less than the second selected pressure.

Description

Pneumatic actuator and pneumatic system comprising a pneumatic actuator

Cross Reference to Related Applications

This application claims the benefit of U.S. patent application No. 62/694,158, filed on 5/7/2018, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The specification relates generally to pneumatic actuators and pneumatic systems. In particular, the following relates to a vacuum actuator for a vacuum pump.

Background

In the automotive industry, it is known to provide vacuum systems for various purposes, such as powering brake boosters, for operation of turbine wastegates, and for other functions. In some applications, a vacuum actuator is used to mechanically initiate operation of the vacuum pump when the vacuum level in the vacuum system is too low (i.e., when the pressure in the vacuum system is too high such that there is not enough vacuum to generate the force required for the intended device operation). Vacuum actuators typically include a diaphragm in a housing, with a spring urging the diaphragm in one direction. The actuator arm is connected to the diaphragm. The amount of vacuum present on one side of the diaphragm indicates whether the diaphragm has overcome the spring and moved the actuator to a new position. A problem with typical vacuum actuators is that these vacuum actuators tend to flutter when the pressure is very close to the pressure that triggers actuation of the vacuum actuator, causing the vacuum actuator to repeatedly activate and deactivate the vacuum pump. To address the problem of jitter, some vacuum pumps have been fitted with solenoids that are operated by an ECU that reads the pressure in the vacuum system via a pressure sensor. However, such a solution can be expensive and increase the complexity of the vacuum system of the vehicle. It would be desirable to provide a vacuum actuator that: the vacuum actuator is relatively simple and inexpensive, avoids the use of electronics, but solves the problem of jitter caused by typical vacuum actuators.

Disclosure of Invention

Broadly, in some aspects, the present disclosure relates to pneumatic actuators and pneumatic systems. In some aspects, the pneumatic actuator is a vacuum actuator and the pneumatic system is a vacuum system.

In one aspect, a vacuum actuator for use in a vehicle vacuum system is provided that includes an actuator housing, an actuator output member, an inter-chamber valve member, a first diaphragm, a second diaphragm, a first diaphragm biasing member, and a second diaphragm biasing member. The actuator housing includes a first chamber and a second chamber. The first chamber can be fluidly connected to a first vacuum source to provide a first chamber pressure to the first chamber. The second chamber is fluidly connectable to a first vacuum source through a second chamber feed conduit. The second chamber has a second chamber pressure. The actuator output member is movable relative to the actuator housing between a first output member position and a second output member position. The inter-chamber valve member is movable between a closed position in which the inter-chamber valve member prevents fluid communication between the first and second chambers, and an open position in which the inter-chamber valve member allows fluid communication between the first and second chambers. The first membrane serves as a wall of the first chamber such that a first side of the first membrane is exposed to a first chamber pressure and a second side of the first membrane is exposed to a first membrane external pressure. The first membrane is connected to the inter-chamber valve member. The second membrane serves as a wall of the second chamber such that a first side of the second membrane is exposed to a second chamber pressure and a second side of the second membrane is exposed to a second membrane external pressure. The second membrane is connected to the actuator output member. The first membrane biasing member is positioned to apply a first biasing force to urge the inter-chamber valve member toward the closed position. The first diaphragm is movable by a pressure differential across the first diaphragm against a first biasing force to move the inter-chamber valve member from the closed position to the open position when the first chamber pressure is less than a first selected pressure. The second membrane biasing member is positioned to apply a second biasing force to urge the actuator output member toward the second output member position. The second diaphragm is movable to move the actuator output member from the second position to the first position by a pressure differential across the second diaphragm against a second biasing force when the second chamber pressure is less than a second selected pressure. The first selected pressure is less than the second selected pressure. The first vacuum source has a first volume and the second chamber has a second volume, wherein the first volume and the second volume are sized relative to each other such that: the reduction of the first chamber pressure to less than the first selected pressure causes movement of the first diaphragm to move the inter-chamber valve member from the closed position to the open position, which exposes the second chamber to the first chamber, thereby reducing the second chamber pressure below the second selected pressure.

In another aspect, a vehicle vacuum system is provided and includes: a first vacuum source that is less than an ambient air pressure outside of the vehicle vacuum system; a vacuum load operating using the first vacuum source to increase a pressure in the first vacuum source; a vacuum pump fluidly connected to the first vacuum source and operable to reduce a pressure in the first vacuum source; and a vacuum actuator. The vacuum actuator includes an actuator housing having a first chamber and a second chamber, an actuator output member, and an inter-chamber valve member. The first chamber is fluidly connectable to a first vacuum source to provide a first chamber pressure to the first chamber, wherein the second chamber is fluidly connectable to the first vacuum source through a second chamber feed conduit, and wherein the second chamber has a second chamber pressure, a first membrane, a second membrane, a first membrane biasing member, and a second membrane biasing member. The actuator output member is movable relative to the actuator housing between a first output member position and a second output member position. The actuator output member is connected to a clutch that controls a connection between a rotor of the vacuum pump and a rotor drive source for operation of driving the rotor, such that movement of the actuator output member to a second output member position connects the rotor drive source to the rotor through the clutch to drive the rotor to reduce pressure in the first vacuum source, and such that movement of the actuator output member to the first output member position disconnects the rotor drive source from the rotor to stop driving the rotor. The inter-chamber valve member is movable between a closed position in which the inter-chamber valve member prevents fluid communication between the first and second chambers, and an open position in which the inter-chamber valve member allows fluid communication between the first and second chambers. The first membrane serves as a wall of the first chamber such that a first side of the first membrane is exposed to a first chamber pressure and a second side of the first membrane is exposed to a first membrane external pressure, wherein the first membrane is connected to the inter-chamber valve member. The second membrane serves as a wall of the second chamber such that a first side of the second membrane is exposed to a second chamber pressure and a second side of the second membrane is exposed to a second membrane external pressure. The second membrane is connected to the actuator output member. The first membrane biasing member is positioned to apply a first biasing force to urge the inter-chamber valve member toward the closed position. The first diaphragm is movable by a pressure differential across the first diaphragm against a first biasing force to move the inter-chamber valve member from the closed position to the open position when the first chamber pressure is less than a first selected pressure. The second membrane biasing member is positioned to apply a second biasing force to urge the actuator output member toward the second output member position. The second diaphragm is movable by a pressure differential across the second diaphragm against a second biasing force to move the actuator output member from the second position to the first position when the second chamber pressure is less than a second selected pressure. The first selected pressure is less than the second selected pressure. The first vacuum source has a first volume and the second chamber has a second volume, wherein the first volume and the second volume are sized relative to each other such that: the reduction of the first chamber pressure to less than the first selected pressure causes movement of the first diaphragm to move the inter-chamber valve member from the closed position to the open position, which exposes the second chamber to the first chamber, thereby reducing the second chamber pressure to less than the second selected pressure.

In yet another aspect, a vacuum actuator for use in a vehicle vacuum system is provided and includes an actuator housing, an actuator output member, a first membrane, a second membrane, a first membrane biasing member, and a second membrane biasing member. The actuator housing includes a first chamber and a second chamber, wherein the first chamber is at a first chamber pressure. The second chamber has a second chamber pressure. The actuator output member is movable relative to the actuator housing between a first output member position and a second output member position. The first membrane serves as a wall of the first chamber such that a first side of the first membrane is exposed to a first chamber pressure and a second side of the first membrane is exposed to a first membrane external pressure. The first diaphragm is operatively connected to the actuator member to move the actuator output member to the first output member position. The second membrane serves as a wall of the second chamber such that a first side of the second membrane is exposed to a second chamber pressure and a second side of the second membrane is exposed to a second membrane external pressure. The second diaphragm is operatively connected to the actuator output member to move the actuator output member to the second output member position. The first membrane biasing member is positioned to apply a first biasing force to the first membrane. The first diaphragm is movable to move the actuator output member from the second output member position to the first output member position by a pressure differential across the first diaphragm against a first biasing force when the first chamber pressure is less than a first selected pressure. The second membrane biasing member is positioned to apply a second biasing force to the second membrane and the actuator output member to urge the output member toward the second output member position. The second diaphragm is movable to move the actuator output member from the second position to the first position by a pressure differential across the second diaphragm that opposes the second biasing force when the second chamber pressure is less than the second selected pressure. The first selected pressure is less than the second selected pressure. The first membrane biasing member has a first spring rate that determines the first selected pressure and the second membrane biasing member has a second spring rate that determines the second selected pressure.

Other technical advantages will be readily apparent to one skilled in the art upon review of the following figures and description.

Drawings

For a better understanding of the embodiments described herein and to show more clearly how the embodiments may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which:

FIG. 1 is a schematic illustration of a vehicle engine including a vacuum pump according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram showing various components of a vacuum system including a vacuum pump and a vacuum actuator for the vacuum pump, wherein a clutch is in a disengaged state;

FIG. 2A is a schematic diagram showing a vacuum pump and an actuator for the vacuum pump with a clutch in an engaged state;

FIG. 3 is a cross-sectional perspective view of the actuator shown in FIG. 2;

FIG. 4 is a cross-sectional side view of a portion of the vacuum system including an actuator as shown in FIG. 2 in a first state;

FIG. 5 is a cross-sectional side view of a portion of the vacuum system shown in FIG. 2 including an actuator in a second state;

FIG. 6 is a cross-sectional side view of a portion of the vacuum system including an actuator as shown in FIG. 2 in a third state;

FIG. 7 is a cross-sectional side view of a portion of the vacuum system including an actuator as shown in FIG. 2 in a fourth state; and

fig. 8 is a cross-sectional side view of a portion of the vacuum system including an actuator as shown in fig. 2 in a fifth state.

Objects depicted in the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

Detailed Description

For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the embodiments described herein. It should be understood at the outset that although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below.

Unless the context indicates otherwise, various terms used throughout this specification may be read and understood as follows: as used throughout, "or" is inclusive, as written as "and/or"; the singular articles and pronouns as used throughout include their plural forms, and the plural forms and pronouns as used throughout include their singular forms; similarly, sexed pronouns include their corresponding pronouns, and thus the pronouns should not be construed as limiting any of the matter described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplary," and not necessarily as "preferred" over other embodiments. Further definitions of terms may be set forth herein; as will be understood from a reading of this specification, these further definitions may apply to previous and subsequent examples of those terms.

Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, components of the systems and devices may be combined or separated. Moreover, the operations of the systems and devices disclosed herein may be performed by more, fewer, or other components, and the methods described may include more, fewer, or other steps. Further, the steps may be performed in any suitable order. As used herein, "each" refers to each member of a group or each member of a subgroup of a group.

In one aspect, the present disclosure relates to a vacuum actuator 36, which vacuum actuator 36 may be connected, for example, to a clutch for a vacuum pump or to some other device. In some embodiments, the vacuum actuator 36 operates more stably between one actuation state and another actuation state without suffering from jitter as is typical with other vacuum actuators of the prior art. In addition, the vacuum actuator 36 achieves this stability without the need for electronic solenoids that have been used in the past on conventional prior art vacuum actuators to address the problem of shudder. Further, in some embodiments, by selecting two springs that determine the pressure required to move the vacuum actuator 36 between the actuated states of the vacuum actuator 36, the vacuum actuator 36 can have a selectable pressure at which the vacuum actuator 36 moves to one actuated state and another selectable pressure at which the vacuum actuator 36 moves to another actuated state.

Referring to fig. 1, fig. 1 is a schematic diagram of a vehicle engine 10. The engine 10 includes a crankshaft 12, the crankshaft 12 driving one or more camshafts 14 via an endless drive member 16, which endless drive member 16 may be, for example, a timing belt or chain. For purposes of illustration only, camshaft 14 is shown with two cams 18 located on camshaft 14. It should be appreciated that the actual number of cams 18 on camshaft 14 will depend on the number of cylinders that the engine has, the number of valves per cylinder, and the total number of camshafts used to control the opening and closing of the valves, among other possible factors. For the purpose of avoiding extraneous details, the engine 10 is shown in simplified form.

Fig. 1 and 2 show (in schematic form) a vacuum pump 22. The vacuum pump 22 may be any suitable type of vacuum pump, such as a rotary vane vacuum pump. An example of a vacuum pump suitable for use in the vacuum pump 22 is shown and described in PCT publication WO2018137045, the contents of which are incorporated herein by reference in their entirety. The vacuum pump 22 is part of a vacuum system 24 located within the vehicle that can be used for multiple purposes. For example, the vacuum system 24 may be used to provide power to a vacuum power plant 25, such as a brake booster, or for operation of a turbine wastegate (in a vehicle equipped with a turbine), or for any other suitable purpose. The vacuum power means 25 may be referred to as a vacuum load 25.

Fig. 2 also shows a clutch 26, which clutch 26 controls the connection between a rotor 28 of the vacuum pump 22 and a rotor drive source for driving the operation of the rotor 28. In the present example, the rotor drive source is the aforementioned camshaft 14 of the one or more camshafts 14, however, the rotor drive source may alternatively be any other suitable power source for the rotor 28.

The clutch 26 may be any suitable type of clutch. The clutch 26 schematically shown in the present drawing is, for example, a friction plate clutch. Alternatively (and preferably), the clutch 26 may be a wrap spring clutch as disclosed in WO 2018137045.

The vacuum system 24 also includes a first vacuum source 30, the first vacuum source 30 being at a pressure P1, which pressure P1 may initially be equal to or less than an ambient air pressure outside of the vehicle vacuum system 24. Ambient air pressure is indicated at P3. The first vacuum source 30 may include a vacuum reservoir 32 and one or more vacuum conduits 34 (or portions of vacuum conduits 34), the one or more vacuum conduits 34 forming part of the vacuum system 24 and being in fluid communication with the vacuum reservoir 32. For example, in the present embodiment, the first vacuum source 30 includes at least portions of vacuum conduits shown at 34a, 34b, 34c, and 34d, respectively.

The vacuum load 25 can be fluidly connected to the first vacuum source 30 via vacuum conduit 34d and operated using the first vacuum source 30 consuming vacuum, thereby increasing the pressure in the first vacuum source 30. As can be seen, the vacuum pump 22 is in fluid communication with the first vacuum source 30 and the vacuum pump 22 is operable to reduce the pressure in the first vacuum source 30 (i.e., draw a vacuum in the first vacuum source 30).

A vacuum actuator 36 is provided and the vacuum actuator 36 includes an actuator housing 38 having a first chamber 40 and a second chamber 42, shown more clearly in fig. 3. The vacuum actuator 36 also includes an actuator output member 44, an inter-chamber valve member 46, a first membrane 48, a second membrane 50, a first membrane biasing member 52, and a second membrane biasing member 54.

The first chamber 40 is fluidly connected to the first vacuum source 30 (via vacuum conduit 34 a) to provide a first chamber pressure to the first chamber 40 as pressure P1. The first chamber 40 is defined between an inner partition wall 56 of the actuator housing 38, an outer wall 58 of the actuator housing 38 (which in this example is the first portion 38a of the actuator housing 38), and the first membrane 48.

The second chamber 42 can be fluidly connected to the first vacuum source 30 through a second chamber feed conduit as the vacuum conduit 34 c. Second chamber 42 is defined between inner partition wall 56, outer wall 58, and second membrane 50. The second chamber 42 has a second chamber pressure P2.

The first membrane 48 may be sealingly connected to the actuator housing 38 in any suitable manner. For example, the first membrane 48 may be sandwiched between the first portion 38a of the actuator housing 38 and the second portion 38b of the actuator housing 38. The second membrane 50 may also be sealingly connected to the actuator housing 38 in any suitable manner. For example, the second membrane 50 may be sandwiched between the first portion 38a of the actuator casing 38 and the third portion 38c of the actuator casing 38. The first and

second membranes

48, 50 may be made of any suitable material known to those skilled in the art for use in vacuum actuators.

The actuator output member 44 is movable relative to the actuator housing 38 between a first output member position (shown in fig. 2) and a second output member position (shown in fig. 2A). The actuator output member 44 is connected to the clutch 26 such that movement of the actuator output member 44 to the second output member position connects the rotor drive source (e.g., the camshaft 14) to the rotor 28 through the clutch 26 to drive the rotor 28 to reduce the pressure in the first vacuum source 30, and such that movement of the actuator output member 44 to the first output member position disconnects the rotor drive source 44 from the rotor 28 to stop driving the rotor 28.

The actuator output member 44 may have any suitable configuration. In the figures, the actuator output member 44 is an actuator arm, and the first output member position is a retracted position of the actuator arm relative to the actuator housing, and the second output member position is an extended position of the actuator arm relative to the actuator housing, the actuator arm extending further from the actuator housing in the extended position than in the retracted position.

First diaphragm 48 serves as a wall of first chamber 40 such that first side 60 of first diaphragm 48 is exposed to first chamber pressure P1 and second side 62 of first diaphragm 48 is exposed to first diaphragm external pressure. In the example embodiment shown, the first diaphragm external pressure is ambient air pressure P3, however, in alternative embodiments not shown, the first diaphragm external pressure may be any other suitable pressure, such as a pressure in other portions of the actuator housing 38 that are isolated from the ambient environment outside of the vacuum actuator 36.

The first membrane 48 is connected to the inter-chamber valve member 46. Thus, movement of the first membrane 48 drives movement of the inter-chamber valve member 46. The inter-chamber valve member 46 is movable between a closed position in which the inter-chamber valve member 46 prevents fluid communication between the first and

second chambers

40, 42 and an open position in which the inter-chamber valve member 46 allows fluid communication between the first and

second chambers

40, 42.

In the example embodiment shown in the figures, the inter-chamber valve member 46 comprises a piston 46a located in the second chamber 42, and a connecting arm 46b, the connecting arm 46b extending from the piston 46a through a hole in the inner partition wall 56 to the first membrane 48 in the first chamber 40. Preventing air flow through the inter-chamber valve member 46 when the inter-chamber valve member 46 is in the closed position may be accomplished in any suitable manner, such as by an O-ring 57 on the rear surface of the piston 46a that seals against the inner partition wall 56. As the piston moves away from the inner partition wall 56, air may flow around the piston 46a and around the connecting arms 46b through the holes in the inner partition wall 56 to provide fluid communication between the second chamber 42 and the first chamber 42.

The second membrane 50 acts as a wall of the second chamber 42 such that the first side 64 of the second membrane 50 is exposed to the second chamber pressure P2 and the second side 66 of the second membrane 50 is exposed to the second membrane external pressure. In the example embodiment shown, the second diaphragm external pressure is ambient air pressure P3, however, in alternative embodiments not shown, the second diaphragm external pressure may be any other suitable pressure, such as a pressure in other portions of the actuator housing 38 that are isolated from the ambient environment outside of the vacuum actuator 36.

The second membrane 50 is connected to the actuator output member 44. Thus, movement of the second membrane 50 drives movement of the actuator output member 44 between the first output member position and the second output member position.

The first membrane biasing member 52 is positioned to apply a first biasing force to urge the inter-chamber valve member 46 toward the closed position. The first diaphragm is movable by a pressure differential across the first diaphragm against a first biasing force to move the inter-chamber valve member 46 from the closed position to the open position when the first chamber pressure P1 is less than the first selected pressure.

The second membrane biasing member 54 is positioned to apply a second biasing force F2 to urge the actuator output member 44 toward the second output member position. The second diaphragm 50 is movable to move the actuator output member 44 from the second position to the first position by a pressure differential across the second diaphragm 50 against a second biasing force when the second chamber pressure P2 is less than a second selected pressure. In some embodiments, the first selected pressure is less than the second selected pressure.

The first vacuum source 30 has a first volume and the second chamber has a second volume. The first volume and the second volume are dimensioned relative to each other such that: the reduction of the first chamber pressure P1 to less than the first selected pressure causes movement of the first diaphragm 48 to move the inter-chamber valve member 46 from the closed position to the open position, which fluidly exposes the second chamber 42 to the first chamber 40, thereby reducing the second chamber pressure P2 to less than the second selected pressure.

A check valve 68 is disposed in second chamber feed conduit 34c, check valve 68 preventing air from flowing from second chamber 42 to first vacuum source 40 through second chamber feed conduit 34c if second chamber pressure P2 is higher than first chamber pressure P1, but check valve 68 allowing air to flow from first chamber 40 to second chamber 42 through second chamber feed conduit 34c if first chamber pressure P1 is higher than second chamber pressure P2. The check valve 68 may be any suitable type of check valve.

The operation of the vacuum system 24 will now be described with reference to fig. 4-8 and with reference back to fig. 2 and 2A. Fig. 4 shows the vacuum actuator 36 in an initial state when the vehicle is stopped and all pressures, i.e., P1, P2, and the first and second diaphragm external pressures are equal to each other. As these pressures equalize, the first and second

diaphragm biasing members

52, 54 hold the inter-chamber valve member 46 in the closed position and the actuator output member 44 in the second position, which engages the clutch 26, as shown in fig. 2A, thereby operatively connecting the rotor drive source (camshaft 14) with the rotor 28 of the vacuum pump 22. Due to this operative connection, the vacuum pump 22 operates to reduce the pressure P1. During this reduction of the first chamber pressure P1, the inter-chamber valve member 46 remains in the closed position and the check valve 68 prevents air from flowing from the second chamber 42 through the second chamber feed conduit 34c, thereby preventing the second chamber pressure P2 from equaling the first chamber pressure P1.

After a period of operation, the first chamber pressure P1 falls below the first selected pressure and the first diaphragm external pressure (e.g., pressure P3) overcomes the first chamber pressure P1 plus the first biasing force of the first diaphragm biasing member 52, and the first diaphragm 48 moves to drive the inter-chamber valve member 36 to the open position, as shown in fig. 5.

Once the inter-chamber valve member 36 is in the open position, the second chamber 42 is in fluid communication with the first chamber 40 and thus the second chamber pressure P2 decreases toward the first chamber pressure P1 until the first and second chamber pressures P1 and P2 reach an equilibrium (equibrium) based on the size of the first volume V1 compared to the second volume V2. As described above, the drop in second chamber pressure P2 is sufficient to cause second chamber pressure P2 to be significantly lower than the second selected pressure. Thus, the second diaphragm external pressure (e.g., pressure P3) overcomes the second chamber pressure P2 plus the second biasing force of the second diaphragm biasing member 54, and the second diaphragm 50 moves to drive the actuator output member 44 to the first output member position, as shown in fig. 6, thereby disengaging the clutch 26 (fig. 2) and operatively disconnecting the rotor drive source from the rotor 28.

With the rotor 28 inoperative, the first chamber pressure P1 rises as the vacuum load 25 operates using vacuum from the first vacuum source 30. However, with the inter-chamber valve member 46 in the open position, the second chamber pressure P2 remains equal to the first chamber pressure P1.

After a period of time, the first chamber pressure P1 rises sufficiently that the first diaphragm external pressure is no longer able to overcome the first biasing force and the first chamber pressure P1, and thus the first diaphragm 48 moves to drive the inter-chamber valve member 46 to the closed position, as shown in fig. 7. As the first chamber pressure P1 continues to rise, the check valve 68 opens as needed to allow the second chamber pressure P2 to continue to equalize with the first chamber pressure P1. Thus, the second chamber pressure P2 also continues to rise. After a further period of time, sufficient vacuum used by vacuum load 25 causes first chamber pressure P1, and correspondingly second chamber pressure P2, to rise sufficiently that the second chamber external pressure can no longer overcome the second biasing force plus second chamber pressure P2. Thus, the second diaphragm 50 moves to drive the actuator output member 44 to the second output member position, as shown in fig. 8, which drives engagement of the clutch 26, thereby operatively connecting the rotor drive source with the rotor 28 (fig. 2A) to cause operation of the vacuum pump 22 so as to reduce the pressure in the first vacuum source 30. At this point, the second chamber pressure P2 will be higher than the first chamber pressure P1 and thus the check valve 68 will close.

As mentioned above, an advantage of the vacuum system 24 and vacuum actuator 36 is that it is not prone to flutter. This occurs due to a number of features. As can be seen, the second chamber 42 is evacuated as long as the inter-chamber valve member 36 is open to equalize the pressure P2 of the second chamber 42 with the first chamber pressure P1. The relative volumes V1 and V2 and the spring rates (rates) of the first and second

membrane biasing members

52, 54 may be selected such that: once the pressure P2 of the second chamber 42 is equal to the first chamber pressure P1 (which occurs quickly), it takes longer for the second chamber pressure P2 to reach the second selected pressure in order for the actuator output component 44 to be driven to the second output member position. As seen in fig. 7, the actuator output member 44 remains in the first output member position even though the inter-chamber valve member 46 has moved to the closed position of the inter-chamber valve member 46. Thus, even if fluttering of the first diaphragm 48 and the inter-chamber valve member 46 occurs in the event that the first chamber pressure P1 rises over a period of time very close to the pressure required to move the diaphragm in one direction or the other, fluttering of the actuator output member 44 does not occur because: as long as the inter-chamber valve member 46 is open, the second chamber pressure P2 drops very quickly (e.g., in less than 0.5 seconds) well below the second selected pressure and it may take some time before the second chamber pressure P2 rises to the second selected pressure as the vacuum load 25 consumes vacuum.

The volumes V1 and V2 may be selected such that the second chamber pressure P2 drops to substantially the same pressure as the first chamber pressure P1 that existed before the inter-chamber valve member 46 opened. For example, if the first volume V1 is about 20 times the size of the second volume V2, the second chamber pressure P2 and the first chamber pressure P1 will be equal to a pressure very close to the first chamber pressure P1 before the chamber valve member 46 opens. In an example, the second volume V2 may be about 200ml, while the first volume V1 may be in the range of 4l to 5 l. It will be appreciated that a larger ratio of the first volume V1 to the second volume V2 will be better, at least for some first selected pressures and second selected pressures, as this could potentially result in a faster drop in pressure in the second chamber 42 and a greater drop in pressure in the second chamber 42. Alternatively, if the first and second volumes V1, V2 are equal, the second chamber pressure P2 will drop by 50% of the difference between the first and second chamber pressures P1, P2 once the inter-chamber valve member 46 is opened. Thus, the first volume V1 and the second volume V2 can be selected to control the following time periods: the second chamber pressure P2 is restored to the length of time it takes for the actuator output member 44 to move to the second output member position based on the average rate of consumption of vacuum by the vacuum load 25.

It should be noted that the effective surface area of the first membrane is greater than the effective area of the piston 46a for the air in the second chamber 42 to exert pressure. Thus, the inter-chamber valve member 46 will move from the closed position if the pressure differential across the first diaphragm 48 is sufficiently large, even if the second chamber pressure P2 is higher than the first chamber pressure P1. Effectively, it is beneficial to: second chamber pressure P2 has a relatively small effect on the first selected pressure in first chamber 40 at which first diaphragm 48 moves to actuate inter-chamber valve member 46.

It should be noted that vacuum load 25 is shown as a single device, such as a brake booster, but those skilled in the art will appreciate that vacuum load 25 may be multiple devices, and each of the multiple devices may be independently connected to first vacuum source 30 or connected to first vacuum source 30 via one or more manifolds.

It should also be noted that in an alternative embodiment, the actuator output member 44 may instead be a rotary device: the rotation means is caused to rotate by movement of the second membrane 50 rather than translating between the first and second output member positions of the actuator output member 44.

It should also be noted that the vacuum system 24 illustrated herein is simplified in the sense that: for some purposes, there may be other control valves or the like that are not shown or described but are understood to be present that form part of the vacuum system 24, such as including a check valve to allow air to flow into the vacuum pump 22 but prevent air from flowing out of the vacuum pump 22 to the first vacuum source 30.

It should also be noted that selection of the spring coefficients of the first and second

membrane biasing members

52, 54 may control the first and second selected pressures that move the actuator output member 44 between the first and second output member positions of the actuator output member 44. In other words, the first membrane biasing member 52 has a first spring rate that determines the first selected pressure, and the second membrane biasing member 54 has a second spring rate that determines the second selected pressure. Thus, by selecting different springs having different spring coefficients, the vacuum actuator 36 may be customized to the vacuum system 24 of the vehicle to accommodate different vehicles having different operating ranges. This advantage exists whether or not the vacuum actuator 36 incorporates a membrane. For example, the vacuum actuator 36 may operate using first and second chamber pistons instead of first and second membranes. Accordingly, the first and second

membrane biasing members

52, 54 may be more broadly referred to simply as first and second biasing members.

As described above, the first membrane 52 and the second membrane 54 are examples of the differential pressure response member. Any other pressure differential responsive member may alternatively be used, such as first and second chamber pistons in place of first and

second membranes

52, 54, respectively.

The vacuum pump 22 is an example of a pneumatic pump. Similarly, the vacuum system 24 is an example of a pneumatic system. Accordingly, the vacuum conduit 34 may be more broadly referred to as a pneumatic conduit 34. Similarly, the vacuum actuator 36 may be more broadly referred to as a pneumatic actuator 36, and the first vacuum source 30 may be referred to as a first pneumatic source 30. In an example, a pneumatic actuator 36 may be used to control the operation of the pneumatic pump 22. Where the pneumatic pump 22 is provided to increase the pressure in the first pneumatic source 30, the pneumatic actuator 36 may be configured to operate in a manner opposite to that shown in the drawings in the following sense: the actuator output member 44 may be driven to the second position to cause operation of the pneumatic pump 22 when the pressure in the second chamber 42 (i.e., the second chamber pressure P2) falls beyond a second selected pressure (rather than increases). Similarly, the inter-chamber valve member 46 may be configured such that: if the pressure P1 in the first chamber 40 is sufficiently high, the pressure P1 overcomes the first diaphragm external pressure (e.g., pressure P3) and the first biasing force of the first diaphragm biasing member 52 moves the first diaphragm 48 to move the inter-chamber valve member 46 to the open position, which in turn causes fluid communication between the first and

second chambers

40, 42, which increases the pressure P2 in the second chamber 42, which moves the second diaphragm 50 to drive the actuator output member to the first output member position, which disengages the clutch and stops operation of the pneumatic pump 22. For this embodiment, it is possible that the inter-chamber valve member 46 may be oriented such that the piston 46a of the inter-chamber valve member 46 is located inside the first chamber 40, rather than in the second chamber 42 as shown.

Thus, in the present disclosure, the term "pneumatic" refers to the use of air (or other gas) and is not intended to be limited to positive pressure (i.e., pressure greater than atmospheric pressure), but is intended to broadly encompass vacuum systems and positive pressure systems.

Although specific advantages have been enumerated above, embodiments may include some, none, or all of the enumerated advantages.

Those skilled in the art will appreciate that there are many more alternative embodiments and modifications possible, and that the above examples are merely illustrative of one or more embodiments. Accordingly, the scope is limited only by the appended claims and any modifications made thereto.

Claims

1. A vacuum actuator for use in a vehicle vacuum system, the vacuum actuator comprising:

an actuator housing comprising a first chamber and a second chamber, wherein the first chamber is fluidly connectable to a first vacuum source to provide a first chamber pressure to the first chamber, wherein the second chamber is fluidly connectable to the first vacuum source through a second chamber feed conduit, and wherein the second chamber has a second chamber pressure;

an actuator output member movable relative to the actuator housing between a first output member position and a second output member position;

an inter-chamber valve member movable between a closed position in which the inter-chamber valve member prevents fluid communication between the first and second chambers and an open position in which the inter-chamber valve member allows fluid communication between the first and second chambers;

a first membrane serving as a wall of the first chamber such that a first side of the first membrane is exposed to the first chamber pressure and a second side of the first membrane is exposed to a first membrane external pressure, wherein the first membrane is connected to the inter-chamber valve member;

a second membrane serving as a wall of the second chamber such that a first side of the second membrane is exposed to the second chamber pressure and a second side of the second membrane is exposed to a second membrane external pressure, wherein the second membrane is connected to the actuator output member;

a first diaphragm biasing member positioned to apply a first biasing force to urge the inter-chamber valve member towards the closed position, wherein the first diaphragm is movable to move the inter-chamber valve member from the closed position to the open position by a pressure differential across the first diaphragm against the first biasing force when the first chamber pressure is less than a first selected pressure; and

a second membrane biasing member positioned to apply a second biasing force to urge the actuator output member toward the second output member position, wherein the second membrane is movable to move the actuator output member from the second output member position to the first output member position by a pressure differential across the second membrane that opposes the second biasing force when the second chamber pressure is less than a second selected pressure,

wherein the first selected pressure is less than the second selected pressure,

wherein the first vacuum source has a first volume and the second chamber has a second volume, wherein the first volume and the second volume are dimensioned relative to each other such that: the reduction of the first chamber pressure to less than the first selected pressure causes movement of the first membrane to move the inter-chamber valve member from the closed position to the open position, which exposes the second chamber to the first chamber, thereby reducing the second chamber pressure to less than the second selected pressure.

2. The vacuum actuator of claim 1, wherein the second chamber feed conduit includes a check valve that prevents air from flowing from the second chamber through the second chamber feed conduit when the second chamber pressure is higher than the first chamber pressure, and that allows air to flow from the first vacuum source into the second chamber when the first chamber pressure is higher than the second chamber pressure.

3. A vacuum actuator as claimed in claim 1, wherein the actuator output member is connected to a clutch which controls a connection between a rotor of a vacuum pump and a rotor drive source for driving operation of the rotor, such that movement of the actuator output member to the second output member position connects the rotor drive source to the rotor through the clutch to drive the rotor, wherein the vacuum pump is fluidly connected to the first vacuum source to reduce the first chamber pressure, and such that movement of the actuator output member to the first output member position disconnects the rotor drive source from the rotor to stop driving the rotor.

4. The vacuum actuator of claim 1, wherein the actuator output member is an actuator arm, and wherein the first output member position is a retracted position of the actuator arm relative to the actuator housing, and the second output member position is an extended position of the actuator arm relative to the actuator housing, the actuator arm extending further from the actuator housing in the extended position than in the retracted position.

5. The vacuum actuator of claim 1, wherein the first volume is at least 20 times greater than the second volume.

6. The vacuum actuator of claim 1, wherein the first membrane external pressure and the second membrane external pressure are both ambient air pressures external to the vacuum actuator.

7. A vehicle vacuum system comprising:

a first vacuum source less than ambient air pressure outside of the vehicle vacuum system;

a vacuum load operating using the first vacuum source, thereby increasing a pressure in the first vacuum source;

a vacuum pump fluidly connected to the first vacuum source and operable to reduce pressure in the first vacuum source;

a vacuum actuator, the vacuum actuator comprising:

an actuator output member movable relative to the actuator housing between a first output member position and a second output member position, wherein the actuator output member is connected to a clutch that controls a connection between a rotor of the vacuum pump and a rotor drive source for operation of driving the rotor, such that movement of the actuator output member to the second output member position connects the rotor drive source to the rotor through the clutch to drive the rotor to reduce pressure in the first vacuum source, and such that movement of the actuator output member to the first output member position disconnects the rotor drive source from the rotor to stop driving the rotor;

a first diaphragm biasing member positioned to apply a first biasing force to urge the inter-chamber valve member toward the closed position, wherein the first diaphragm is movable to move the inter-chamber valve member from the closed position to the open position by a pressure differential across the first diaphragm that opposes the first biasing force when the first chamber pressure is less than a first selected pressure; and

wherein the first selected pressure is less than the second selected pressure,

8. The vehicle vacuum system of claim 7, wherein the second chamber feed conduit includes a check valve that prevents air from flowing from the second chamber through the second chamber feed conduit when the second chamber pressure is higher than the first chamber pressure, and the check valve allows air to flow from the first vacuum source into the second chamber when the first chamber pressure is higher than the second chamber pressure.

9. The vehicle vacuum system of claim 7, wherein the actuator output member is an actuator arm, and wherein the first output member position is a retracted position of the actuator arm relative to the actuator housing, and the second output member position is an extended position of the actuator arm relative to the actuator housing, the actuator arm extending further from the actuator housing in the extended position than in the retracted position.

10. The vehicle vacuum system of claim 7, wherein the first volume is at least 20 times greater than the second volume.

11. The vehicle vacuum system of claim 7, wherein the first membrane external pressure and the second membrane external pressure are both ambient air pressures external to the vacuum actuator.

12. A vacuum actuator for use in a vehicle vacuum system, the vacuum actuator comprising:

an actuator housing comprising a first chamber and a second chamber, wherein the first chamber is at a first chamber pressure, wherein the second chamber has a second chamber pressure;

a first diaphragm serving as a wall of the first chamber such that a first side of the first diaphragm is exposed to the first chamber pressure and a second side of the first diaphragm is exposed to a first diaphragm external pressure, wherein the first diaphragm is operatively connected to the actuator output member to move the actuator output member to the first output member position;

a second diaphragm serving as a wall of the second chamber such that a first side of the second diaphragm is exposed to the second chamber pressure and a second side of the second diaphragm is exposed to a second diaphragm external pressure, wherein the second diaphragm is operatively connected to the actuator output member to move the actuator output member to the second output member position;

a first diaphragm biasing member positioned to apply a first biasing force to the first diaphragm, wherein the first diaphragm is movable to move the actuator output member from the second output member position to the first output member position by a pressure differential across the first diaphragm that opposes the first biasing force when the first chamber pressure is less than a first selected pressure; and

a second membrane biasing member positioned to apply a second biasing force to the second membrane and the actuator output member to urge the output member toward the second output member position, wherein the second membrane is movable to move the actuator output member from the second output member position to the first output member position by a pressure differential across the second membrane that opposes the second biasing force when the second chamber pressure is less than a second selected pressure,

wherein the first selected pressure is less than the second selected pressure,

wherein the first membrane biasing member has a first spring rate that determines the first selected pressure and the second membrane biasing member has a second spring rate that determines the second selected pressure.