DE102015106945A1 - Self-aligning piston spring accumulator - Google Patents

Abstract

A memory (22) for a vehicle may include a cylinder (24) defining a bore (26) having an interior surface (40) and a piston (28) moveable within the bore (26). The piston (28) may include a seal (50) and a guide portion (34) defined by a truncated sphere. The guide portion (34) aligns the piston (28) in the bore (26) so that the seal (50) maintains contact with the inner surface (40) of the bore (26).

Description

TECHNICAL AREA

The present application relates to memory for transmissions in vehicle drive trains.

BACKGROUND

Stores are part of a transmission in a vehicle powertrain. They store potential hydraulic energy when the engine is off. When the internal pressure of the accumulator is lower than the pressure from a hydraulic pump, the hydraulic fluid flows into the accumulator and fills it. The accumulator stores this fluid volume under pressure to store potential hydraulic energy. In an engine restart command, accumulators apply pressurized hydraulic fluid to the shifting elements that is required by the transmission to transfer power following an engine start. This is useful for vehicles using engine start / stop systems.

Engine start / stop systems turn off a vehicle engine when no torque is required, such as when the vehicle is stopped at a traffic light. This helps to reduce fuel consumption, but increases the number of times the engine has to be restarted. Therefore, it is advantageous to supply the energy required for the switching elements at a motor restart command faster.

SHORT VERSION

An accumulator for a vehicle includes a cylinder defining a bore having an interior surface and a piston moveable within the bore. The piston includes a seal and a guide portion defined by a cut ball. The guide portion is configured to align the piston in the bore so that the seal maintains contact with the inner surface of the bore.

A reservoir includes a cylinder that defines a bore and a cylinder axis, and a piston that is movable in the bore. The piston has a piston axis. The piston axis and the cylinder axis define a tilt angle. The accumulator further includes a seal disposed on the piston and a guide portion formed on the piston. The guide portion has a curvature such that the seal maintains contact with the cylinder at a maximum tilt angle greater than 2 degrees.

A powertrain for a vehicle includes a motor, a pump that is mechanically driven by the engine to pressurize hydraulic fluid when the engine is running, a plurality of shift elements, a hydraulic control system configured to supply pressurized fluid from the pump to the engine to direct a plurality of switching elements, and a memory which is configured to store the pressurized fluid and to supply the pressurized fluid to the plurality of switching elements when the engine is not running. The accumulator includes a cylinder, a piston defining a chamber disposed in the cylinder, and a spring biasing the piston to reduce the volume of the chamber. The piston includes a guide portion having a cut spherical portion.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic representation of a vehicle drive train;

2 is a cross-sectional view of a vehicle memory;

3 is a partial cross-sectional view which is enlarged at a part of a vehicle piston; and

4 is a partial cross-sectional view which is enlarged at a part of a vehicle piston with a misaligned spring.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It should be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed herein are therefore not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As would be apparent to one of ordinary skill in the art, various features illustrated and described with reference to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of the illustrated features provide representative embodiments for typical applications. However, various combinations and modifications of the features that conform to the teachings of this disclosure could be made for certain applications or implementations may be desired.

With reference to 1 schematically is a plan view of a vehicle drive train 10 shown. An engine 12 leads the gearbox 14 Torque too. The gear 14 contains a gear pump 16 , Hydraulic controls 18 , Switching elements 20 and a memory 22 , While the engine 12 is running, is the gear pump 16 hydraulically with the hydraulic controls 18 coupled. The gear pump 16 sucks fluid from a transmission sump 17 , The hydraulic controls 18 conduct through the gear pump 16 supplied fluid to the switching elements 20 , The memory 22 will be filled when the pressure from the hydraulic pump 16 is greater than the internal pressure of the memory 22 ,

The larger pressure of the hydraulic pump 16 creates a pressure difference that allows the hydraulic fluid to drain the reservoir 22 to fill. When the pressure of the gear pump 16 under pressure in the store 22 lies, the memory becomes 22 not filled. The hydraulic controls allow through a valve and a check valve to the memory 22 to store the hydraulic fluid under pressure to maintain a stored potential hydraulic energy while the engine is shut down to save fuel. The hydraulic controls 18 point at the restart command of the motor 12 the memory 22 To do this, the required hydraulic energy to the switching elements 20 dissipate. Storing more hydraulic energy requires either increasing the space or storage 22 with a higher energy density. A store 22 , which stores more hydraulic energy density, more quickly energizes the required switching elements 20 at a restart of the engine 12 ,

As in 2 includes one for vehicle powertrain configurations 10 suitable memory 22 one a hole 26 defining cylinder 24 , one in the hole 26 movable piston 28 and a spring 30 that is configured to the piston 28 in the hole 26 pretension. A misalignment of the spring 30 can lead to increased wear on the piston 28 can cause and damage the piston 28 increase what a frictional resistance force between the piston 28 and the cylinder 24 arises. To compensate for this additional wear, and to take into account the Reibwiderstandskraft, usually a piston 28 with a large length to diameter ratio, for example, over 1.2, and bushings on the inside of the cylinder 24 used. As a result, space is in the hole 26 reduces and the energy storage capacity for a given available space of the memory 22 reduced.

2 shows a cross section of a memory 22 for a vehicle according to the present disclosure. The memory 22 includes a cylinder 24 , a feather 30 and a piston 28 , The cylinder 24 defines a hole 26 that have an inside diameter 32 having. By reducing the ratio of length to diameter of the piston 28 By removing a piston skirt and eliminating the need for guide bushes, an increase in the outer diameter 44 the feather 30 allowed. Removing the skirt clears the limitations on the outside diameter 44 the feather 30 out of the way, reducing the potential hydraulic energy density of the store 22 is increased.

As stated above, space in the memory 22 be significant. By enlarging the installation space, thereby allowing a spring 30 with a larger outside diameter 44 in the pistons 28 fits, the hydraulic energy is increased. Storing more hydraulic energy can result in a higher stored energy density. By eliminating the need for guide bushes, there is space in the bore 26 increases and becomes the hydraulic energy density of the store 22 elevated.

To enlarge the outside diameter 44 the feather 30 is the piston 28 with a guide section 34 educated. By heat treatment or coating and low microfinish, for example polishing, the guide section 34 with a truncated spherical curvature 36 be formed. The guide section can be made using surface hardened steel with a Rockwell hardness of at least 50 RC. This allows the guide section 34 to prevent the wear typically absorbed by the bushings. In addition, the truncated spherical curvature reduces 36 of the guide section 34 Contact between the piston 28 and the hole 26 , The truncated spherical curvature 36 of the guide section 34 reduces itself against the hole 26 moving piston surface 38 , This reduces friction imposed by friction and the discharge response time of the memory 22 will be improved.

The missing contact of the piston surface 38 with the cylinder 24 , resulting in a reduction of the resistance of the piston 28 on the cylinder 24 leads, coupled with the increase in the hydraulic energy density, allows the memory 22 furthermore, the switching elements 20 to re-energize the engine for an engine restart. The response time of the memory 22 can be reduced to approximately 250 milliseconds. This can be a vehicle powertrain 10 the engine 12 start anew, before the hydraulic pump 16 is capable of the vehicle transmissions 14 To supply energy. Feeding the for a restart of the engine 12 required hydraulic energy and the improved response time of the memory 22 improve the overall fuel economy of the vehicle.

With reference to 3 is a partially enlarged cross-sectional view A of the memory 22 shown, referring to a part of the guide section 34 concentrated. 3 shows the guide section 34 of the piston 28 , which is aligned on the spring 30 sitting.

The diameter 42 of the guide section 34 can be essentially equal to the outside diameter 44 the feather 30 be. This will give a better balance of the piston 28 on the pen 30 reached to the resistance between the piston 28 and the inner surface 40 the bore 26 continue to reduce. Furthermore, the diameter 42 of the guide section 34 also substantially equal to the inner diameter 32 the bore 26 be. Therefore, the outer diameter 44 the feather 30 essentially equal to the inner diameter 32 the bore 26 be. The enlarged bore space allows the spring 30 a larger outer diameter 44 having. With a larger outside diameter 44 is the spring 30 capable of the piston 28 continue to support under a higher pressure. This allows an increase in the pressure in the cylinder 24 and thus an increase in the hydraulic energy density of the memory 22 ,

A feather 30 with a larger outside diameter 44 can support a larger volume of hydraulic fluid, reducing the pressure in the cylinder 24 can be increased. Increasing the volume and the resulting increase in pressure results in an increase in the hydraulic energy density of the reservoir 22 , By increasing the hydraulic energy density of the accumulator 22 will be the response time of the memory 22 improved. By storing a larger volume of hydraulic fluid under a higher pressure through the use of a valve and a check valve, the accumulator is replaced 22 allows to energize the switching elements faster.

Furthermore, the increase in the spring diameter allows 44 a longer piston stroke volume of the accumulator 22 , A feather 30 with a larger outside diameter 44 can be compressed more, resulting in a longer stroke of the piston 28 is allowed. Increasing the stroke volume of the piston 28 allows a higher hydraulic energy density of the memory 22 , As mentioned above, a high hydraulic energy density allows the memory 22 when supplying hydraulic power to the transmission 14 reacts faster. Therefore, enlarging the diameter allows 44 the feather 30 and forming the guide section 34 with a diameter 42 which is substantially equal to the outside diameter 44 the feather 30 is a significant reduction in the response time of the memory 22 ,

With reference to 4 is a partially enlarged cross-sectional view A of the memory 22 at a part of the guide section 34 of the piston 28 shown. The guide section 34 can with a curved surface 36 and two straight edges 46 be educated. The two straight edges 46 blunt the spherical texture of the curved surface 36 from. This allows self-alignment of the piston 28 , The piston 28 hovers on the spring 30 in the hole 26 of the cylinder 24 , and the spring 30 tenses the piston 28 to an end 27 the bore 26 in front. A slight misalignment α of the spring 30 tilts the piston 28 , whereby contact between the guide section 34 and an inner surface of the bore 26 is effected.

For example, the spring 30 be misaligned by about 2 °. This low degree of misalignment α can lead to tilting of the piston 28 against the inner surface 40 the bore 26 to lead. When the piston 28 on the pen 30 can be tilted, the curved surface 36 of the guide section 34 the inner surface 40 the bore 26 touch. The guide section 34 acts as an adjustment mechanism that controls the misalignment α of the spring 30 balances.

The tilting reduces a gap γ between the guide portion 34 and the hole 26 , By reducing the gap γ between the guide portion 34 and the hole 26 becomes the distance between a base edge 48 of the piston 28 and an inner surface 40 the bore 26 elevated. This is due to the angular misalignment α of the spring 30 due. The enlargement of the gap γ may require that the piston 28 a seal 50 at a greater distance from the inner surface 40 the bore 26 holds. The guide section 34 with a diameter 42 which is substantially equal to the inside diameter 32 the bore 26 is, this enlargement of the gap γ account and allows the piston 28 , a seal 50 opposite the inner surface 40 the bore 26 maintain.

The guide section 34 achieves this by a ratio between the length 52 and the diameter 42 the curved surface 36 , The ratio of the length 52 to the diameter 42 of the guide section 34 is greater than a tangent to the misalignment α of the spring 30 , This allows the guide section 34 , the Misalignment α of the spring 30 compensate. The ratio of the length 52 to the diameter 42 can be such that the guide section 34 more than 5 ° of a tilt angle β between a piston axis 56 in a cylinder axis 58 balances.

Because the guide section 34 a tilt angle β of over 5 ° and the misalignment α of the spring 30 may be about 2 to 3 °, is the guide section 34 further configured to the piston 28 in the hole 26 Take into account and align it. The truncated spherical curvature 36 of the guide section 34 align the piston 28 in the hole 26 out. A self-aligning guide section 34 allows the piston 28 , without use of guide bushes on the spring 30 to float. The guide section 34 therefore allows as part of the piston 28 a self-alignment of the piston 28 in the hole 26 despite hovering on a misaligned spring 30 , This allows the cylinder 24 despite the potential low degree of misalignment α of the spring 30 a feather 30 with a larger outside diameter 44 to use. The self-aligning guide section 34 can the hydraulic energy density of the store 22 increase by about 20%.

The truncated spherical curvature 36 of the guide section 34 further prevents seizure between the piston 28 and the hole 26 , As explained above, the curved surface minimizes 36 of the guide section 34 Contact between the piston 28 and the inner surface 40 the bore 26 , Due to the spherical nature of the curved surface 36 can the piston 28 the inner surface 40 the bore 26 only touch in one place. Despite a misalignment α of the spring 30 therefore supports the leadership section 34 of the piston 28 Furthermore, the reduction of wear on the piston 28 , Minimize the contact between the piston 28 and the inner surface 40 the bore 26 allows a longer life of the memory 22 , This saves time, costs and production costs.

By reducing the seizure between the inner surface 40 the bore 26 and the guide section 34 Further, the frictional resistance force between the piston 28 and the cylinder 24 reduced. By reducing the resistance, not only damage to the guide portion becomes 34 of the piston 28 due to friction reduces, but also the response time of the memory 22 improved. Further, by reducing the frictional resistance force, the memory is allowed 22 the hydraulic energy to energize the switching elements 20 instead of using the hydraulic energy to overcome the drag force. Therefore, the guide portion allows 34 the memory 22 to store more potential hydraulic energy, to have a higher energy density and an improved response time.

While embodiments have been described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The terms used in the specification are terms of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments of the invention, which may not be explicitly described or illustrated. While various embodiments may be presented as advantages or preferred over other embodiments or implementations of the prior art regarding one or more desired properties, as will be apparent to one of ordinary skill in the art, trade-offs may be made between one or more features or one or more features to achieve the desired overall system characteristics, depending on the particular application and implementation. These features may include, but are not limited to, cost, strength, longevity, life cycle cost, marketability, appearance, packaging, size, ease of maintenance, weight, manufacturability, ease of assembly, and so forth. Embodiments that are described as being less desirable than other embodiments or prior art implementations with respect to one or more features are thus not outside the scope of the disclosure and may be desirable for particular applications.

• A. Speicher für ein Fahrzeug, umfassend: einen Zylinder, der eine Bohrung mit einer Innenfläche definiert; und einen Kolben, der in der Bohrung beweglich ist, wobei der Kolben eine Dichtung und einen Führungsabschnitt, der durch eine abgeschnittene Kugel definiert wird, enthält, wobei der Führungsabschnitt dazu konfiguriert ist, den Kolben in der Bohrung so auszurichten, dass die Dichtung Kontakt mit der Innenfläche der Bohrung bewahrt.
• B. Speicher nach A, ferner umfassend eine Feder, die in der Bohrung angeordnet ist und dazu konfiguriert ist, den Kolben zu einem Ende der Bohrung vorzuspannen.
• C. Speicher nach A, wobei der Führungsabschnitt unter Verwendung von oberflächengehärtetem Stahl mit einer Rockwell-Härte von mindestens 50 RC hergestellt ist.
• D. Speicher nach A, wobei der Führungsabschnitt einen Durchmesser und eine Länge aufweist, die Feder einen Fehlausrichtungswinkel aufweist und ein Verhältnis der Führungsabschnittslänge zu dem Führungsabschnittsdurchmesser größer als eine Tangente des Fehlausrichtungswinkels ist.
• E. Speicher nach D, wobei der Fehlausrichtungswinkel kleiner als 2 Grad ist.
• F. Speicher nach D, wobei das Verhältnis von der Länge zu dem Durchmesser der abgeschnittenen Kugel größer als eine Tangente von 5 Grad ist.
• G. Speicher, umfassend: einen Zylinder, der eine Bohrung und eine Zylinderachse definiert; einen Kolben, der in der Bohrung beweglich ist, wobei der Kolben eine Kolbenachse aufweist, wobei die Kolbenachse und die Zylinderachse einen Kippwinkel definieren; eine Dichtung, die an dem Kolben angeordnet ist; und einen Führungsabschnitt, der an dem Kolben ausgebildet ist, wobei der Führungsabschnitt eine Krümmung aufweist, so dass die Dichtung Kontakt mit dem Zylinder bei einem maximalen Kippwinkel von über 2 Grad bewahrt.
• H. Speicher nach G, wobei der Führungsabschnitt eine abgeschnittene Kugel definiert.
• I. Speicher nach G, ferner umfassend eine Feder, die zum Vorspannen des Kolbens zu einem Ende des Zylinders konfiguriert ist, wobei die Feder eine Federachse aufweist, wobei die Federachse und die Zylinderachse einen Fehlausrichtungswinkel definieren, der kleiner ist als der maximale Kippwinkel.
• J. Speicher nach G, wobei das Verhältnis von Länge zu Durchmesser des Führungsabschnitts derart ist, dass die Dichtung Kontakt mit dem Zylinder beim maximalen Kippwinkel hält.
• K. Antriebsstrang für ein Fahrzeug, umfassend: einen Motor; eine Pumpe, die durch den Motor mechanisch angetrieben wird, um Hydraulikfluid mit Druck zu beaufschlagen, wenn der Motor läuft; mehrere Schaltelemente; ein Hydrauliksteuersystem, das dazu konfiguriert ist, druckbeaufschlagtes Fluid von der Pumpe zu den mehreren Schaltelementen zu leiten; und einen Speicher der dazu konfiguriert ist, das druckbeaufschlagte Fluid zu speichern und den mehreren Schaltelementen das druckbeaufschlagte Fluid zuzuführen, wenn der Motor nicht läuft, wobei der Speicher einen Zylinder, einen in dem Zylinder angeordneten eine Kammer definierenden Kolben und eine Feder, die den Kolben zum Reduzieren des Volumens der Kammer vorspannt, enthält, wobei der Kolben einen Führungsabschnitt, der einen abgeschnittenen sphärischen Teil aufweist, enthält.
• L. Antriebsstrang nach K, wobei eine Länge des abgeschnittenen sphärischen Teils derart ist, dass der abgeschnittene sphärische Teil eine Fehlausrichtung der Feder im Speicher ausgleicht.
• M. Antriebsstrang nach K, wobei der abgestumpfte sphärische Teil den Kolben im Zylinder ausrichtet.
• N. Antriebsstrang nach K, wobei der abgeschnittene sphärische Teil den Zylinder an einer einzigen Stelle berührt.

It is further described:

• A. A storage for a vehicle, comprising: a cylinder defining a bore having an inner surface; and a piston movable in the bore, the piston including a seal and a guide portion defined by a cut ball, the guide portion configured to align the piston in the bore so that the seal contacts preserved the inner surface of the bore.
• B. A reservoir, further comprising a spring disposed in the bore and configured to bias the piston to an end of the bore.
• C. Memory according to A, wherein the guide section is made using surface hardened steel having a Rockwell hardness of at least 50 RC.
• D. A memory according to A, wherein the guide portion has a diameter and a length, the spring has a misalignment angle, and a ratio of the guide portion length to the guide portion diameter is larger than a tangent of the misalignment angle.
• E. Memory to D where the misalignment angle is less than 2 degrees.
• F. Memory to D where the ratio of the length to the diameter of the cut ball is greater than a 5 degree tangent.
• G. A memory comprising: a cylinder defining a bore and a cylinder axis; a piston movable in the bore, the piston having a piston axis, the piston axis and the cylinder axis defining a tilt angle; a gasket disposed on the piston; and a guide portion formed on the piston, the guide portion having a curvature such that the gasket maintains contact with the cylinder at a maximum tilt angle greater than 2 degrees.
• H. Memory according to G, wherein the guide section defines a cut ball.
• An accumulator according to claim 1, further comprising a spring configured to bias the piston toward an end of the cylinder, the spring having a spring axis, the spring axis and the cylinder axis defining a misalignment angle that is less than the maximum tilt angle.
• J. Memory according to G, wherein the ratio of length to diameter of the guide portion is such that the seal makes contact with the cylinder at the maximum tilt angle.
• K. A powertrain for a vehicle, comprising: an engine; a pump mechanically driven by the motor to pressurize hydraulic fluid when the engine is running; a plurality of switching elements; a hydraulic control system configured to direct pressurized fluid from the pump to the plurality of switching elements; and a reservoir configured to store the pressurized fluid and supply the pressurized fluid to the plurality of shift elements when the engine is not running, the reservoir having a cylinder, a piston defining a chamber and a spring defining the piston for reducing the volume of the chamber biases, wherein the piston includes a guide portion having a cut spherical portion.
• L. Driveline to K, wherein a length of the cut spherical portion is such that the cut spherical portion compensates for misalignment of the spring in the accumulator.
• M. Drive train to K, with the truncated spherical part aligning the piston in the cylinder.
• N. drivetrain to K, with the cut off spherical part touching the cylinder at a single point.

Claims (10)

A memory for a vehicle, comprising: a cylinder ( 24 ), which has a bore ( 26 ) with an inner surface ( 40 ) Are defined; and a piston ( 28 ), in the hole ( 26 ) is movable, the piston ( 28 ) a seal ( 50 ) and a guide section ( 34 ) defined by a truncated sphere, the guide portion (FIG. 34 ) is configured to move the piston ( 28 ) in the hole ( 26 ) so that the gasket ( 50 ) Contact with the inner surface ( 40 ) of the bore ( 26 ). A memory according to claim 1, further comprising a spring ( 30 ), in the hole ( 26 ) is arranged and configured to the piston ( 28 ) to one end of the bore ( 26 ) to bias. A memory according to claim 1, wherein the guide section (16) 34 ) is made using surface hardened steel having a Rockwell hardness of at least 50 RC. A memory according to claim 1, wherein the guide section (16) 34 ) a diameter ( 42 ) and a length ( 52 ), the spring ( 30 ) has a misalignment angle and a guide section length ratio ( 52 ) to the guide section diameter ( 42 ) is greater than a tangent of the misalignment angle. The memory of claim 4, wherein the misalignment angle is less than 2 degrees. A memory according to claim 4, wherein the ratio of the length ( 52 ) to the diameter ( 42 ) of the truncated sphere is greater than a 5 degree tangent. A memory comprising: a cylinder ( 24 ), which has a bore ( 26 ) and a cylinder axis ( 58 ) Are defined; a piston ( 28 ), in the hole ( 26 ) is movable, the piston ( 28 ) a piston axis ( 56 ), wherein the piston axis ( 56 ) and the cylinder axis ( 58 ) define a tilt angle; a seal ( 50 ) attached to the piston ( 28 ) is arranged; and a guide section ( 43 ) attached to the piston ( 28 ) is formed, wherein the guide portion ( 43 ) has a curvature, so that the seal ( 50 ) Contact with the cylinder ( 24 ) at a maximum tilt angle of over 2 degrees. A memory according to claim 7, wherein the guide section (16) 34 ) defines a truncated sphere. A memory according to claim 7, further comprising a spring ( 30 ) used to bias the piston ( 28 ) to one end of the cylinder ( 24 ) is configured, the spring ( 30 ) has a spring axis, wherein the spring axis and the cylinder axis ( 58 ) define a misalignment angle that is less than the maximum tilt angle. Memory according to claim 7, wherein the ratio of length ( 52 ) to diameter ( 42 ) of the guide section ( 34 ) is such that the seal ( 50 ) Contact with the cylinder ( 24 ) at the maximum tilt angle.

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