Pump unit, in particular for delivering pressure medium in brake circuit of electronically slip-adjustable brake system of motor vehicle

Abstract

The invention relates to a pump unit (10) for delivering a pressure medium in a brake circuit of an electronically slip-adjustable brake system of a motor vehicle. Known pump units (10) have a pump cylinder (12) in which a pump piston (14) that can be driven in a reciprocating movement is arranged. The pump piston (14) and the pump cylinder (12) together form a pump working chamber (16), and the pressure medium flows into the pump working chamber under the control of an inlet valve (20) and flows out under the control of an outlet valve (22). The outlet valve (22) comprises an outlet valve sealing seat (34) and an outlet valve closure (24) interacting therewith, said outlet valve closure being actuated by an outlet valve spring (86). According to the invention, the outlet valve (22) has a valve seat contour (28) consisting of two conical bores (30, 32) which are concentric to one another and transition into one another and which have cone angles of different sizes, an outlet valve sealing seat (34) which interacts with the outlet valve closure (24) being arranged at the first conical bore (30), the cone angle of which is smaller than the cone angle of the second conical bore (32).

Description

TECHNICAL FIELD

[0001] The invention relates to a pump unit according to the preamble of claim 1, in particular for feeding pressure medium in a brake circuit of an electronically slip-controllable brake system of a motor vehicle. Such a pump unit is known, for example, from the document DE 10 2014 212 292 A1. Figure 1 BACKGROUND

[0002] In the known pump unit, the outlet valve comprises a steel ball which is pressed against an outlet valve seat under the action of a helical spring. The outlet valve seat is configured as a conical seat, the contour of which is formed by a conical bore. The narrowest point of the conical seat transitions into a cylindrical channel which in turn opens into the working chamber of the pump. Downstream of the conical seat, the pressure medium is discharged through a housing assembly which has an annular channel and radial channels branching off from the annular channel, which channels open into the brake circuit with which the pump unit is in contact. SUMMARY

[0003] Against this background, the object of the invention is to further improve the known pump unit, to increase its delivery capacity, to reduce the operating noise, to increase the service life and the reliability, and in addition to reduce the material and production costs of the pump unit.

[0004] To achieve the above object, the pump unit according to the features of claim 1 has an outlet valve with a valve seat contour which is formed by two conical bores which are concentric to one another and transition into one another, the two conical bores having different cone angles, wherein an outlet valve sealing seat for an outlet valve closure is provided at the first conical bore, the cone angle of which is smaller than the cone angle of the second conical bore.

[0005] The valve seat contour of the outlet valve limits the radial oscillations of the outlet valve closure, thereby contributing to a reduction in the noise of the pump unit, more precisely to a reduction in the operating noise of the pump unit. The amplitude of the pressure oscillations which are forced to occur is smaller, which can prevent wear of the outlet valve and increase the service life and the reliability of the pump unit and its components.

[0006] Further advantages or expedient refinements of the invention are given by the dependent claims and / or the following description.

[0007] The configuration of the outlet valve closure is adapted to the valve seat contour of the outlet valve, thereby ensuring that the pump unit delivers a high flow rate with low wear even in low-temperature environments.

[0008] The configuration of the outlet valve closure optimizes the axial guidance of the opening or closing movement of the outlet valve closure inside the valve seat contour and in addition centers the resilient outlet valve spring with respect to the outlet valve closure. In addition, the configuration also serves to limit the stroke.​

[0009] At the transition from the intermediate section of the valve closing member to the spring support, a recess, notch, groove or similar structure is provided, so that, if the valve closing member is inadvertently assembled incorrectly, i.e. with the second end section of the valve closing member facing the sealing seat, an appreciable leakage will occur in the closed state of the outlet valve. From the measured leakage during production, the assembly error can easily be detected and the assembly quality improved.

[0010] Furthermore, immediately upstream of the outlet valve, a filter screen is provided, by means of which the outlet valve is protected from the ingress of foreign particles and thus from the resulting wear. By means of the filter screen arranged in the pump working chamber, the annular filter upstream of the inlet valve in the prior art can be omitted, so that the resulting pressure loss is avoided. The filter screen is configured as a flat plate and is therefore cost-effective. In contrast to conventional annular filters, the invention uses a frame-like annular support element which has a plurality of open flow-through windows for the pressure medium along the circumference. These open flow-through windows have a negligible throttling effect on the flowing pressure medium.

[0011] Finally, a flow cross-section is formed inside the pump unit by the valve seat contour and the wall of the housing part which accommodates the outlet valve closing member and its associated outlet valve spring, through which the pressure medium flows out of the pump unit in a specific manner. The pressure medium flows around the outlet valve closing member, so that optimum opening and closing properties of the outlet valve closing member are achieved, which reduces the noise effect and increases the service life of the pump unit. BRIEF DESCRIPTION OF DRAWINGS

[0012] Embodiments of the invention are shown in the drawings and described in detail below.

[0013] The description of the drawings comprises six figures, in which corresponding parts are identified using uniform reference numerals. Shown in the figures are:

[0014] Figure 1 is a longitudinal section through a perspective view of a pump unit according to a first embodiment of the invention;

[0015] Figure 2 is a longitudinal section through a perspective view of a pump unit according to a second embodiment of the invention;

[0016] Figure 3 is a perspective view of an annular support element as a single part;

[0017] Figure 4 is a perspective view of a filter screen as a single part;

[0018] Figure 5 is a perspective view of a valve closing member as a single part; and

[0019] Figure 6 This is a perspective view of the housing component as a single part. Detailed Implementation

[0020] Figure 1 The pump unit 10 shown includes: a pump cylinder 12; a pump piston 14 movably housed in the pump cylinder 12 and driven to perform periodic up-and-down (as shown in the figure) reciprocating motion; a pump working chamber 16 defined by the pump cylinder 12 and the pump piston 14; a piston reset element 18 disposed in the pump working chamber 16; an inlet valve 20 for controlling the inflow of pressure medium into the pump working chamber 16; and an outlet valve 22 for controlling the outflow of pressure medium from the pump working chamber 16.

[0021] The pump cylinder 12 is composed of a cylindrical body closed on one side by a cylinder bottom 12a. The cylindrical body has a surrounding cylinder shank 12b that surrounds the pump working chamber 16, and its inner wall guides the pump piston 14 axially and radially. A through-hole 26, closed by an outlet valve closing element 24, is constructed at the center of the cylinder bottom 12a. The outlet valve 22 is configured as a center valve, and its valve seat profile 28, viewed along the flow direction of the pressure medium, is connected downstream of the through-hole 26. According to the invention, the valve seat profile 28 is composed of two concentric tapered holes 30 and 32 that transition into each other, and these two tapered holes have different cone angles. An outlet valve sealing seat 34 for the outlet valve closing element 24 is provided at the first tapered hole 30 facing the through-hole 26. The cone angle of the first tapered hole 30 is smaller than the cone angle of the second tapered hole 32 connected downstream therefrom.

[0022] Upstream of the outlet valve 22, a filter screen 36 is provided inside the pump working chamber 16. This filter screen protects the downstream outlet valve 22 from contamination by particulate matter and / or other contaminants in the pressurized medium, thereby contributing to the trouble-free and low-wear operation of the pump unit 10, and more specifically, its outlet valve 22. The installed filter screen 36 is plate-shaped and preferably has a generally circular shape. The filter screen has multiple through openings 38 for the pressurized medium. Each through opening 38 may optionally have a circular cross-section or an arbitrary free-form cross-section. By selecting the material of the filter screen 36, its material thickness, the number of through openings 38, the opening profile of the through openings 38, the total cross-sectional area of ​​the openings, and the spacing between the through openings 38, the filtration effect of the filter screen 36 can be adapted to the specific application without adversely affecting the flow coefficient of the pump unit 10.

[0023] In the illustrated embodiment, the pump piston 14 is constructed in two parts, including a solid cylindrical first piston portion 40 located outside the pump working chamber 16 and a hollow cylindrical second piston portion 42 extending at least partially into the pump working chamber 16. A receiving area is formed on the second piston portion 42, into which the first piston portion 40 partially extends and rests flush with the stepped portion of the second piston portion 42.

[0024] The second piston portion 42 has a plurality of radial holes 44 that lead to an axial hole 46 passing through the second piston portion 42. The end of the axial hole 46 facing the pump working chamber 16 forms an inlet valve seat 48 of the inlet valve 20 of the pump unit 10. The inlet valve is controlled by an inlet valve element 50, which in this embodiment of the invention is constructed as a sphere and is pressed against the inlet valve seat 48 by an inlet valve spring 52. The inlet valve spring 52 is a helical spring, the end of which is supported on a valve housing 54 away from the inlet valve element 50. The valve housing 54 extends into the pump working chamber 16 and is fixed at one end to the second piston portion 42. The valve housing 54 has a circumferential through hole 56 through which the pressure medium reaches the pump working chamber 16 when the inlet valve element 50 is lifted from the inlet valve seat 48 under pressure against the force of the inlet valve spring 52. Furthermore, a surrounding shoulder 58 is constructed on the piston-side end of the valve housing 54, and one end of the piston reset element 18 abuts against this shoulder. This shoulder 58 forms a surrounding sealing lip, which seals the pump working chamber 16 or the guide portion of the pump piston 14 in the pump cylinder 12 relative to the outside.

[0025] The portion of the pump unit 10 extending from the pump cylinder 12 is surrounded by a frame-like annular support element 60. The annular support element is fixed to the open end of the pump cylinder 12 by an axial extension. This annular support element 60 is preferably made of plastic and has two opposing ends, which are respectively constructed as annular structures 62 and 64. Figure 3 And connected by longitudinal struts 66 to form a single rigid component. The longitudinal struts 66 are arranged at certain intervals along the circumference of the annular support element 60, and form open flow windows 68 therebetween. Figure 3 The pressurized medium can flow almost unimpeded from the outside into the inlet valve 20 of the pump unit 10 through the flow window. The annular support element 60, located above the pump cylinder 12, guides the first piston portion 40 of the pump piston 14 and has internal dimensions matching the external dimensions of this first piston portion 40. Furthermore, the upper annular structure 62 carries a molded sealing ring 70 disposed outside the annular support element 60. This molded sealing ring 70 seals the guide clearance between the outer circumference of the pump piston 14 and the inner diameter of the pump housing's corresponding pump housing portion.

[0026] The outlet valve closing element 24 is a rotationally symmetrical component, having an intermediate section 72 ( Figure 5 ) and two integrally molded end sections 74 and 76 ( Figure 5 These two ends protrude outward from the middle section 72 along the axial direction in opposite spatial directions.

[0027] The outlet valve closing element 24 engages with the outlet valve sealing seat 34 of the valve seat profile 28 via a first end section 74. This first end section 74 has an elliptical longitudinal cross section.

[0028] Multiple protrusions 78 or pointed portions protrude axially outward from the first end section 74 along the longitudinal axis of the outlet valve closing member 24. Their outer walls lie within an imaginary circle whose diameter corresponds to the diameter of the through portion 26 in the bottom 12a of the pump cylinder 12. During the opening or closing movement of the outlet valve closing member 24, the protrusions 78 axially guide the outlet valve closing member within the through portion 26 of the pump cylinder 12. The pressurized medium flows between the protrusions 78 and exits from the pump working chamber 16 along the circumference of the first end section 74 of the outlet valve closing member 24.

[0029] The second end section 76 of the outlet valve closing element 24 ( Figure 5 For example, it is pin-shaped, having a cylindrical base 80 and a truncated cone 82 that tapers outwards. The transition portion from the cylindrical base 80 at the second end section 76 to the middle section 72 forms a right-angled shoulder that surrounds the outer circumference, forming a spring support 84 for the outlet valve spring 86. The cylindrical base 80 centers the outlet valve spring 86 and the outlet valve closing element 24 together.

[0030] On the circumference of the outlet valve closing member 24, at least one recess 88 extending along the longitudinal axis of the outlet valve closing member 24 is formed at the transition portion of the spring support portion 84 from the intermediate section 72 to the second end section 76. Figure 5 In particular, notches, grooves, or the like. If the outlet valve shut-off part 24 is unintentionally misassembled, the recess 88 will cause measurable leakage when the outlet valve 22 is not operated, thus making it easy to detect assembly errors or monitor assembly quality.

[0031] The outlet valve spring 86 is supported in the receiving portion 90 of the housing component 92 at its end facing away from the pump unit 10. A wall portion 94 is formed on the end face of the housing component 92 facing the pump cylinder 12, protruding axially along the longitudinal axis of the pump unit 10, surrounding the recess 90 for housing the outlet valve spring 86. The wall portion 94 is radially surrounded externally by a groove-shaped annular channel 96 opening toward the pump cylinder 12, which connects with at least one radial channel 98 of the housing component 92.Figure 6 The housing component 92 has a raised wall 94 that is axially spaced from the wall of the second tapered bore 32 of the pump cylinder 12, thereby forming a flow cross section 100 between the two walls. The pressure medium flows through this flow cross section from the pump working chamber 16, into the annular channel 96, and then to the radial channel 98, or out of the pump unit 10.

[0032] Figure 2 A second embodiment of the pump unit according to the invention is shown, which differs from the first embodiment in that at least the inlet valve shut-off member 50 is constructed identically to the outlet valve shut-off member. Accordingly, both valve shut-off members 24, 50 are constructed as rotationally symmetrical components, each having a central section 72 and two end sections 74, 76 integrally formed on the central section and projecting axially from the central section 72 in opposite spatial directions. To avoid repetition, for other embodiments and design details regarding the outlet valve shut-off members 24, 50, please refer to the [reference to the original text]. Figure 1 The relevant descriptions were made.

[0033] Figure 3 The perspective view shows the already combined pair Figure 1 The description refers to the annular support element 60 as a single component. As previously mentioned, the annular support element 60 is preferably a plastic body with its two opposing ends constructed as annular structures 62 and 64. The annular structures 62 and 64 are interconnected as a single rigid component by longitudinal struts 66 arranged circumferentially. The annular support element 60 integrates the pump unit 10, more specifically the pump cylinder 12 and pump piston 14, with the inlet valve 20 and piston reset element 18 into a single assembly. According to the invention, the annular support element 60 has a plurality of flow windows 68 on its circumference, through which the pressure medium can flow to the inlet valve 20 as unobstructed as possible, thereby reducing the pressure loss coefficient of the pump unit 10 or achieving low-pressure-loss flow. The number and detailed structural design of the longitudinal struts 66 determine the delivery efficiency of the pump unit 10.

[0034] Figure 4The filter screen 36, as a single component, is shown and is arranged upstream of the outlet valve 22 in the pump unit 10. The filter screen 36 can be considered as a flat plate, preferably with a thickness of at least 0.05 mm and a maximum of 0.50 mm. In principle, the filter screen 36 can have an outer contour of any shape; the shape shown in the figure is at least approximately circular. It is recommended that the outer diameter of the filter screen 36 be between 0.5 mm and 12.0 mm. The filter screen 36 has a number of through openings 38 for the pressurized medium. These through openings 38 can also have any contour, but are preferably circular, with a diameter between 0.02 mm and 1.0 mm. The minimum hole spacing between two through openings 38 is between 0.01 mm and 1.00 mm. Through these geometric conditions, combined with the material strength of the filter screen 36, the viscosity of the pressurized medium, the peak flow rate of the pump unit 10, and the expected size of foreign particles, an optimal balance between pressure loss and strength can be achieved. The filter 36 protects the outlet valve 22 from contamination by foreign particles, thereby improving the reliability of the pump unit 10, or more precisely, the outlet valve 22, or reducing its risk of failure.

[0035] Figure 5 Valve shut-off elements 24 and 50, as separate components of an outlet or inlet valve, are shown. The valve shut-off elements 24 and 50 shown have a nearly rotationally symmetrical body with a central section 72 and two end sections 74 and 76 projecting axially outward from opposite sides of the central section 72. The outer diameter of the central section 72 is between 1.0 mm and 8.0 mm; the total axial length of the valve shut-off elements 24 and 50 is between 2.0 mm and 10.0 mm. The outer circumference of the central section 72 forms a contact surface with respect to the wall of the receiving portion 90 in the housing component 92. A first end section 74 is adjacent to the central section 72 and has an elliptical, and then circular, longitudinal cross-section. When the outlet valve 22 is closed, the first end section 74 seals the outlet valve seat 34. At least three and at most seven protrusions 78 project axially outward from the first end section 74. The outer walls of these protrusions lie within an imaginary circle on the circumference of the valve closing elements 24 and 50, the outer diameter of which is between 1.0 mm and 8.0 mm. The elongation of the protrusion 78 is a minimum of 0.2 mm and a maximum of 10.0 mm.

[0036] The second end section 76 of the valve closing elements 24 and 50, opposite the first end section 74, forms the spring support portion 84 of the piston reset element 18. This spring support portion 84 is formed by a right-angled shoulder constructed around the piston, which includes a pin-shaped core consisting of a cylindrical base 80 and a frustoconical body 82. The cylindrical base 80 centers the piston reset element 18 and the valve closing elements 24 and 50 together.

[0037] The second end section 76 can have any profile, such as cylindrical, conical, spherical, or even formed by ribs. Furthermore, the length of this second end section along the longitudinal direction of the valve shut-off members 24, 50 can be intentionally configured to be greater than the full compression length (Blocklänge) of the piston return element 18 to protect it from damage under operating conditions. A recess 88 is locally provided at the transition from the spring support 84 to the intermediate section 72; this recess can be designed as, for example, a groove, a notch, or the like. This recess 88 can have any shape, and leakage will occur if the valve shut-off members 24, 50 are unintentionally misassembled with the spring support 84 facing the valve seat 34. During the assembly of the pump unit 10, the amount of leakage can be measured to identify and remove the misassembled component.

[0038] In principle, the valve closing elements 24 and 50 can be made of any material, wherein the lower the mass of the valve closing element, the better its opening and closing performance.

[0039] Figure 6 As shown, the valve shut-off element 24 of the outlet valve 22, along with its associated outlet valve spring 86, is housed in a receiving portion 90 of the housing component 92. An observer viewing the housing component 92 from the end face facing the pump cylinder 12 can see a continuously surrounding wall 94, which is surrounded by an annular channel 96. The wall 94, together with the second tapered bore 32 of the valve seat profile 28 on the pump cylinder 12, forms a specific gap or flow cross-section 100 through which the pressure medium reaches the annular channel 96 in a specific manner. At least one side of the annular channel 96 leads to a radial channel 98.

[0040] The flow cross section 100, valve seat profile 28, annular channel 96, and at least one radial channel 98 are structurally adapted to each other, such that the flow of the pressure medium around the valve shut-off element 24 causes specific opening and / or closing movements of the valve shut-off element. This reduces the noise impact of the pump unit 10 and extends its service life.

[0041] Of course, modifications or advantageous improvements can be made to the embodiments without affecting the scope of protection defined by the claims.

Claims

1. A pump unit (10), particularly for delivering a pressure medium in the brake circuit of an electronically slip-adjustable braking device for a motor vehicle, the pump unit comprising: Pump cylinder (12); Pump piston (14), which is slidably guided to be housed in the pump cylinder (12) and can be driven to perform periodic reciprocating motion; Pump working chamber (16) defined by the pump cylinder (12) and pump piston (14); An inlet valve (20) for controlling the flow of pressure medium into the pump working chamber (16); and An outlet valve (22) for controlling the flow of pressure medium out of the pump working chamber (16). The outlet valve (22) includes an outlet valve sealing seat (34) and an outlet valve closing element (24) that cooperates with the outlet valve sealing seat (34). The outlet valve (22) is characterized in that it has a valve seat profile (28) consisting of two concentric tapered holes (30, 32) that transition into each other, the two tapered holes having different cone angles, wherein the outlet valve sealing seat (34) is disposed at the first tapered hole (30), the cone angle of the first tapered hole being smaller than the cone angle of the second tapered hole (32).

2. The pump unit according to claim 1, characterized in that, The outlet valve closing element (24) has an intermediate section (72) and two end sections (74, 76), the two end sections being arranged on opposite sides of the intermediate section (72) and protruding outward from the intermediate section (72) respectively.

3. The pump unit according to claim 2, characterized in that, The first end section (74) of the outlet valve sealing seat (34) has an elliptical longitudinal section, and the second end section (76) has a spring support (84) surrounding the outlet valve spring (86).

4. The pump unit according to claim 2 or 3, Its features are, At least three protrusions (78) protrude axially outward from the first end section (74), and the protrusions (78) are inserted into the through hole (26) of the pump cylinder (12) adjacent to the valve seat profile (28) in order to axially guide the outlet valve shut-off element (24).

5. The pump unit according to claim 3 or 4, Its features are, The second end section (74) extends along the longitudinal axis of the outlet valve shut-off member (24) for a length greater than the full compression length of the outlet valve spring (86).

6. The pump unit according to any one of claims 3 to 5, Its features are, On the circumference of the outlet valve closing member (24), at the transition position from the intermediate section (72) to the spring support (84), at least one recess, particularly a groove or pit, extending along the longitudinal axis of the outlet valve closing member (24) is constructed.

7. The pump unit according to any one of claims 1 to 6, Its features are, In the pump working chamber (16), a filter screen (36) is arranged upstream of the outlet valve (22).

8. The pump unit according to any one of claims 3 to 7, Its features are, The outlet valve closing element (24), together with the outlet valve spring (86), is housed in the receiving portion (90) of the housing component (92). The housing component (92) has a wall (94) surrounding the receiving portion (90) on the end face facing the pump cylinder (12). The receiving portion (90) is surrounded radially on the outside by an annular channel (96), and a radial channel (98) leads into the annular channel (96).

9. The pump unit according to claim 8, Its features are, The end face of the wall portion (94) of the housing component (92) forms a flow cross section (100) with the wall of the second conical hole (32), through which the pressure medium flowing out from the outlet valve (22) enters the annular channel (96) of the housing component (92).

10. The pump unit according to any one of claims 1 to 8, Its features are, The pump unit (10) has a frame-shaped annular support element (60), the opposite ends of the annular support element (60) are constructed as annular structures (62, 64), and the annular structures are connected into an integral component by multiple longitudinal pillars (66). The longitudinal struts (66) are arranged at intervals along the circumference of the annular support element (60), so that there is an open flow window (68) between every two longitudinal struts (66) through which the pressure medium can flow.

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