DE102009047456A1 - Check valve for piston pump of brake assembly of passenger car, has resetting unit pushing mobile valve body to valve seat and partially formed from elastomer, and plastic foil provided between resetting unit and valve body - Google Patents

Abstract

The valve (10) has a resetting unit (16) pushing a mobile valve body (18) to a valve seat (20) and partially formed from elastomer. The resetting unit comprises two parts, where one of the parts guides the valve body with movement. A plastic foil is provided between the resetting unit and the valve body and engaged with an engaging unit at a neighboring component. A wavy recess is arranged with a cup-shaped valve cover (14). Fingers are formed at the resetting unit for partially holding the valve body, where the resetting unit is surrounded by a pulsation damper.

Description

The invention relates to a check valve, in particular for a piston pump, with a return means for urging a movable valve body on a valve seat. Furthermore, the invention relates to a piston pump with such a check valve and a vehicle brake system with such a check valve.

State of the art

Check valves are known as intake or exhaust valves, in particular of piston pumps. Such piston pumps are used for example in hydraulic units of modern vehicle brake systems in passenger cars or trucks to provide the brake system regulated braking pressures. For dosing the brake pressure, the hydraulic unit has a pump with several pump elements and with a motor. On the individual pump elements check valves are formed, in particular to prevent backflow of the pumped brake fluid from the pressure side of the pump. As a rule, such check valves have a valve closing body, an associated valve seat and a spring which presses the valve closing body against the valve seat with spring force. These springs are generally made of a special spring steel or a copper beryllium alloy.

Piston pumps have principle-induced flow pulsations, which can lead to intense pressure pulsations and mechanical vibrations. This pressure pulsations or pressure surges caused by a design-related, regular stall on the piston pump. Due to the sudden tearing off of the flow, the kinetic energy of a fluid, on the suction side and the pump causes a rapid increase in pressure. At the pressure side, however, vapor bubbles occur when the vapor pressure falls below the vapor pressure. The resulting vapor bubbles implode at backflow of the fluid which also very strong pressure surges, in the order of several 100 MPa, can arise (cavitation). Pressure increase and cavitation can in extreme cases lead to the destruction of individual pump components or the entire pump.

In addition, the mechanical vibrations can be heard as sounds audible or as vibrations. This effect is called NVH (Noise, Vibration, Harshness). For example, this NVH effect can adversely affect customer acceptance of a vehicle having such a pump. This increases the risk of complaints.

The invention has for its object to provide a check valve, in particular for a piston pump, which has an improved behavior compared to pressure pulsations compared to known check valves and thus has an improved NVH behavior.

Disclosure of the invention

The object is achieved with a check valve according to claim 1 and a piston pump according to claim 11. Furthermore, the object is achieved with a vehicle brake system according to claim 12.

According to the invention, a check valve, in particular for a piston pump, is provided, with at least one return means, for urging a movable valve body onto a valve seat, in which the return means is formed at least partially from elastomer.

The check valve comprises a return means, for example a spring element, which urges a movable valve body on a valve seat. The return means is at least partially formed of elastomer and has a predefined shape. Under load, the return means can deform and thus enables a lifting of the valve body from the valve seat. When released, the return means returns to its original shape and urges the valve body back onto the valve seat. In an advantageous use of such an elastomeric spring, in contrast to a conventional coil spring, no tension energy must be predetermined or prestressed.

The elasticity of the elastomer is based on a static-dynamic equilibrium. The balance is due to a structural property of the macromolecular compounds of the elastomer. These macromolecular compounds, so-called polymer chains, have a pronounced Drehneigung, which causes a twisting of the polymer chains to their individual chain elements. This creates polymer balls. If a force acts on the elastomer, a tension is created on the individual polymer coils. Under the influence of this elasticity, the polymer balls stretch and the elastomer begins to deform. If the elasticity disappears, the stretched polymer coils twist again and the elastomer returns to its original shape. With a return means, which is at least partially formed of elastomer, a progressive spring characteristic can be achieved. In such a progressive spring characteristic, a spring force increases in response to a load of a spring. This means that a large load counteracts a large spring force, whereby a breakthrough, for example by a pressure surge, can be avoided. At normal load, however, the spring speaks soft. With the return means according to the invention can be cost effective dampen pressure surges and thus improve the NVH behavior of the piston pump.

With the elastomer, a pressure damper is advantageously created, such that the pressure pulse is simultaneously reduced and damped when opening the valve.

According to a first advantageous embodiment of the check valve according to the invention, the return means is designed in several parts and at least a first part of the return means is formed from the elastomer.

The return means is formed according to the invention of several parts and a first part made of elastomer. The elastomer has elastic or resilient properties and is therefore advantageous for resetting the movable valve body. Due to the multi-part design of the return means different materials can advantageously be used for the individual parts. Due to the different properties of the materials used, each part can solve a different task. A use of expensive composite materials, in particular on a one-piece return means, can thus be avoided.

According to a second advantageous embodiment of the check valve according to the invention at least a second part of the return means is adapted to guide the valve body during its movement.

A second part of the return means is advantageously formed of a rigid material, such as metal. Due to the solid properties of the material on the one hand a largely lossless transmission of a restoring force, in particular an elastomeric spring possible. On the other hand, the part can perform a supporting or guiding function in the movement of the valve body. The valve body is guided through the second part with a precise fit to the associated valve seat. This compression losses are avoided and there is a better pressure build-up dynamics, especially on an associated piston pump.

According to a third advantageous development of the check valve according to the invention, a plastic film is provided between the return means and the valve body.

This plastic film is advantageously made of PEEK (polyetheretherketone). In particular, this plastic has a high mechanical strength and good sliding properties. The use of such a film increases the abrasion resistance of the return means and the valve body and thereby selectively protects areas which are exposed to high mechanical stress. A costly design of an entire component of such a material can be avoided by this film and the check valve is a total of more durable and less expensive to produce. Other plastic films with these or similar properties can be used for the check valve according to the invention.

According to a fourth advantageous development of the check valve according to the invention, the plastic film is locked with a latching means on one of the adjacent components.

The plastic film is inventively attached to one of the adjacent components, such as the return means. The plastic film is clipped with a latching means, for example locking lugs, to the return means. For this purpose, the return means may advantageously have recesses into which the locking lugs engage. The locking lugs are then fixed, for example with barbs, in the recesses. The engagement of the plastic film, in particular a PEEK plastic film on the adjacent component allows for easy production, which can be carried out without great technical effort.

According to a fifth advantageous development of the check valve according to the invention, the plastic film is shrunk on one of the adjacent components.

For shrinking the plastic film on an adjacent component, such as the valve body, the film is applied to the component and heated. Due to the heat energy provided thereby relax polymer chains that have already been put into an extended state during the production of the thermoplastic film. The plastic film contracts. This creates a frictional connection between the plastic film and the component. For shrinking a variety of thermoplastics are suitable. However, thermoplastics having a high mechanical strength and good sliding properties, such as PEEK, are advantageously shrink-wrapped. The shrunk-on plastic film increases the abrasion resistance of the neighboring components.

According to a sixth advantageous development of the check valve according to the invention, a cup-shaped valve cover is provided, in which at least one wave-shaped recess is arranged circumferentially on the inside.

The cup-shaped valve cover has in its interior a cavity with an inner circumference. Along this inner circumference is at least one undulating recess. In the cavity is the return means, which is thus held by the valve cover. If a pressure force is now exerted on the return means via a valve body, then this deforms.

In this case, the return means, for example an elastomer spring, expands into the wave-shaped recess. Since a volume of the return means remains unchanged during the deformation, a sufficient evasion volume must be provided for this purpose. This evasive volume is provided in a simple manner with the wave-shaped recess or with a plurality of wave-shaped recesses.

According to a seventh advantageous development of the check valve according to the invention, the return means is at the same time designed to act as a damper of a fluid flow passing through the valve seat.

Piston pumps generate, as mentioned above, no continuous flow. Between two strokes of such a pump, there is usually a stall of the pumped fluid. This creates pressure surges that cause additional mechanical stress on the components. In addition, these pressure surges create a NVH behavior described above. To improve the NVH behavior and to dampen the pressure surges, a return means is provided according to the invention, which at least partially consists of an elastomer. The elastomer is particularly suitable for achieving this object, since it also has a damping property in addition to a resilient one. This damping property manifests itself in the deformation of the elastomer. The elastomer does not store energy during deformation. The supplied energy is converted to heat energy and then radiated by the elastomer. To return to its original shape after deformation, the elastomer re-absorbs energy in the form of heat from the environment. Due to the advantageous use of such restoring means according to the invention, resilient and damping properties are combined in one component. An additional damping element as in a conventional metal coil spring is eliminated. This allows for space-saving and lower-cost check valves, with improved NVH performance and increased service life.

According to an eighth advantageous development of the check valve according to the invention, fingers are formed on the return means, which hold the valve body at least partially.

The return means has a plurality of fingers which at least partially enclose the valve body. If the valve body is pressed by a compressive force against the fingers, which are advantageously made of elastomer, these can deform and allow movement of the valve body. If the pressure force decreases, the fingers return to their original shape, thereby guiding the valve body onto the valve seat. A design of the return means with fingers allows a targeted guided movement of the valve body. As a result, as already explained, compression losses can be avoided, resulting in improved pressure build-up dynamics.

According to a ninth advantageous development of the check valve according to the invention stages are formed on the return means, where the valve body comes to rest.

At the return means according to the invention successive stages are formed. The valve body can rest on only one or more stages at the same time. If the valve body is pressed by a pressure force acting on it against the advantageously formed from elastomer stages, they deform. The valve body shifts until it comes to rest on a next stage. With a corresponding pressure force, this next step is deformed and the valve body is pressed further into the return means. While the return means respond softly under normal load, the stiffness increases through the stepped training with increasing pressure force. As a result, a progressive spring characteristic of the return means can be achieved in a particularly advantageous manner, and penetration, for example in the case of push impacts, is thereby prevented.

According to the invention, a check valve, in particular for a piston pump, is provided, with at least one return means, for urging a movable valve body onto a valve seat, in which the return means is surrounded by a pulsation damper.

The pulsation damper, which is designed in particular as an insert, encloses the return means, which is for example a conventional coil spring made of spring steel. The pulsation damper itself is advantageously designed as a hollow cylinder and formed from elastomer and has a spring force increasing with the pressure force. If there is a pressure surge in the check valve, the pulsation damper deforms in the radial direction, whereby the stall is damped. Due to the progressive spring characteristic of the pulsation damper a uniform damping of pressure surges is achieved, which leads to an improved NVH behavior of the piston pump.

Furthermore, the invention relates to a piston pump with such a check valve and a vehicle brake system with such a check valve.

Hereinafter, embodiments of the solution according to the invention will be explained with reference to the accompanying schematic drawings. It shows:

1 a longitudinal section of a check valve according to the invention with a formed with fingers return means,

2 a longitudinal section of the check valve according to 1 with a return means formed with steps,

3 a longitudinal section of the check valve according to 1 with a multi-part return means,

4 a perspective side view of a return means according to the invention with trained fingers,

5 a perspective cross section through a valve cover with wave-shaped recesses,

6 a longitudinal section of the check valve according to the invention, with plastic film with latching means,

7 a longitudinal section of the check valve according to 2 , with shrunk plastic film and

8th a longitudinal section of the check valve according to the invention with a pulsation damper.

In the 1 to 3 is a check valve 10 to see it on a pump housing 12 a (not shown) piston pump is mounted. The check valve comprises as components a cup-shaped valve cover 14 , a means of return 16 and a valve body 18 with an associated valve seat 20 , The valve seat 20 is at an opening 22 of the pump housing 12 educated. Is the valve body 18 sealing on the valve seat 20 up, that's the opening 22 sealed fluid-tight.

The cup-shaped valve cover 14 has inside, centrally on a substantially cylindrically shaped cavity. In this cavity is formed as an elastomer spring return means 16 , The return means 16 does not completely fill the cavity of the valve cover, but leaves alternative areas 24 free. The return means 16 urges the valve body 18 against the valve seat 20 , The valve body 18 closes the opening with it 22 fluid-tight.

If the piston pump starts to deliver a fluid, it is created in the pump housing 12 Print. This causes the valve body 18 a compressive force which the valve body 18 in the direction of the return means 16 suppressed. By this pressure force, the return means begins 16 to deform. In the deformation, as explained above, a clamping force acts on the individual polymer coils of the elastomer spring, which thereby begin to stretch. Because the volume of the return agent 16 remains unchanged, this extension takes place in the appropriate alternative spaces 24 , Due to the deformation of the return means 16 can the valve body 18 now from the valve seat 20 take off. The previously through the valve body 18 closed opening 22 is now free and can be traversed by fluid.

When the delivery stroke performed by the piston pump is completed, the pressure in the pump housing drops 12 from. Due to the thereby decreasing pressure force on the valve body 18 begins the return means 16 to relax. The valve body 18 gets back to the valve seat 20 pushes and closes the opening 22 , A backflow of the previously funded fluid into the pump housing 12 will be prevented.

Furthermore, in the 1 and 4 the return means 16 trained with fingers. The fingers are elastomeric and partially enclose the valve body. The fingers guide the valve body 18 when closing the check valve 10 back to the valve seat 20 , This targeted recycling of the valve body 18 prevents compression losses and improves the noise behavior of the check valve 10 ,

In 2 , are at the return means 16 several stages formed at which the valve body 18 is applied. The return means 16 is made of elastomer, so that the steps can deform under the action of a force and then a movement of the valve body 18 allow. After the deformation of the steps, the valve body passes 18 to a nearest step, which also deforms at a correspondingly high force. Depending on the force acting, the return means reacts 16 So with a different stiffness and thus has a favorable for the application progressively stepped spring characteristic.

3 shows the above arrangement with a multi-part, in this case two-part, return means 16 , This is a first part 26 frusto-conical and made of elastomer. This first part 26 lies on an inner end face of the cup-shaped valve cover 14 and is partially embedded in this. A second part 28 is located between the first part 26 and the valve body 18 , The second part 28 is formed as a substantially circular cylinder, each with a recess at its two end faces. One of the first part 26 facing end face of the second part 28 has a circular cross-section depression into which the elastomer protrudes. A the valve body 18 facing end face of the second part 28 has a substantially hemispherical recess formed on the valve body 18 fits perfectly. This will cause the valve body 18 purposefully guided in one movement. The second part 28 of the return means 16 is formed of a rigid material, in this case made of metal.

In 5 is a cross section through a valve cover 14 shown in perspective. In this case, the valve cover 14 along an inner circumference wavy recesses 30 on. Within this inner circumference is formed as an elastomer spring return means 16 , As at a deformation of the return means 16 whose volume remains constant, an evasion volume is necessary for the deformation. This evasive volume is with the wave-shaped recesses 30 provided in exactly the amount needed for opening the opening 22 and the damping of pressure pulsations is needed.

In 6 is at the return means 16 a PEEK plastic film 32 engaged. It will be on the plastic film 32 trained locking lugs 34 in recesses of the return means 16 pressed. Through at the locking lugs 34 formed barbs arise between the return means 16 and the plastic film 32 a form-fitting connection.

Due to the high mechanical resistance of the PEEK plastic film 32 The abrasion resistance and durability of the return agent 16 elevated.

In 7 is a PEEK plastic film 32 on the valve body 18 shrunk. The PEEK plastic film 32 Due to its thermoplastic properties, it is particularly well suited for shrink-fitting onto an adjacent component. In addition to increased abrasion resistance, the PEEK plastic film improves 32 with its good sliding properties the movement of the valve body 18 along the steps of the return means.

In 8th is a check valve 10 to see that on a pump housing 12 is appropriate. The check valve 10 includes the with wavy recesses 30 trained valve cover 14 , A presently designed as a helical spring return means 16 , the valve body 18 and a trained as insert pulsation damper 36 , The valve cover 14 holds the return means 16 and the pulsation damper 36 , The pulsation damper 36 is formed hollow cylindrical, lies with its front sides on the one hand on the valve cover 14 and on the other hand on the pump housing 12 and surrounds the return means 16 that the valve body 18 with its spring force against the valve seat 20 pressed.

The check valve 10 is, as explained above, flows through a fluid in a delivery stroke of the piston pump. At the end of the stroke, there is a stall and thus a pressure surge, especially in the valve cover 14 , In such a pressure surge pressure forces inside the valve cover 14 , Due to these compressive forces, the pulsation damper formed of elastomer deforms 36 and expands radially into the recesses 30 out. Due to the deformation of the pulsation damper 36 the pressure surge is mitigated. Because the pulsation damper 36 has a spring force increasing with the pressure force, a lower as a high pressure is equally reliably damped.

Claims (13)

Check valve ( 10 ), in particular for a piston pump, with at least one return means ( 16 ), for urging a movable valve body ( 18 ) on a valve seat ( 20 ), characterized in that the return means ( 16 ) is formed at least partially of elastomer. Check valve according to claim 1, characterized in that the return means ( 16 ) is designed in several parts and at least a first part ( 26 ) of the return means ( 16 ) is formed from the elastomer. Check valve according to claim 2, characterized in that at least a second part ( 28 ) of the return means ( 16 ) is designed to the valve body ( 18 ) in his movement. Check valve according to one of claims 1 to 3, characterized in that a plastic film ( 32 ) between the return means ( 16 ) and the valve body ( 18 ) is provided. Check valve according to claim 4, characterized in that the plastic film ( 32 ) with a latching means ( 34 ) is engaged on one of the adjacent components. Check valve according to one of claims 4 and 5, characterized in that the plastic film ( 32 ) is shrunk on one of the adjacent components. Check valve according to one of claims 1 to 6, characterized in that a cup-shaped valve cover ( 14 ) is present, at the inside circumferentially at least one wave-shaped recess ( 30 ) is arranged. Check valve according to one of claims 1 to 7, characterized in that the return means ( 16 ) is at the same time designed as a damper one through the valve seat ( 20 ) to act through fluid flow. Check valve according to one of claims 1 to 8, characterized in that on the return means ( 16 ) Fingers are formed, which the valve body ( 18 ) at least partially. Check valve according to one of claims 1 to 9, characterized in that on the return means ( 16 ) Are formed at which stages the valve body ( 18 ) comes to the concern. Check valve ( 10 ), in particular for a piston pump, with at least one return means ( 16 ), for urging a movable valve body ( 18 ) on a valve seat ( 20 ), characterized in that the return means ( 16 ) of a pulsation damper ( 36 ) is surrounded. Piston pump with a check valve ( 10 ) according to one of claims 1 to 11. Vehicle brake system with a check valve ( 10 ) according to one of claims 1 to 11.

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