GB2574824A

GB2574824A - Piston pump with integrated leakage

Info

Publication number: GB2574824A
Application number: GB201809998A
Authority: GB
Inventors: Stoica Cosmin
Original assignee: Continental Automotive Systems SRL
Current assignee: Continental Automotive Systems SRL
Priority date: 2018-06-19
Filing date: 2018-06-19
Publication date: 2019-12-25
Also published as: GB201809998D0

Abstract

Piston pump with a piston 4 reciprocating within a pump bore 3 to draw fluid through an inlet check valve 7 into a compression chamber 5, pressurise it and discharge it through an outlet check valve 6. The piston is pushed in one direction by a camshaft rotated by a motor inside an eccentric chamber 2 around an axis orthogonal to the piston’s axis of reciprocation, and in the opposite direction by a return spring 8 inside the compression chamber. A sealing package comprising sealing rings 10.1, 10.2 and a piston sleeve is arranged around the piston, to prevent fluid flowing from the compression to the eccentric chamber. However, in the event of a leak due to wear of the sealing elements, a cavity 11 is provided in the pump bore to collect leakage fluid. The pump may be used to deliver brake fluid in vehicle brake systems. The cavity may be one or more radial bores or multiple radial fly-cuts within the piston sleeve. Alternatively, it may be a circular channel between the sealing rings, formed by recesses thereof, optionally with a further cylindrical fly-cut (12, fig. 3) and an additional bore leading to a separate reservoir (fig. 4).

Description

PISTON PUMP WITH INTEGRATED LEAKAGE

Field of the invention [0001] The present invention relates to a piston pump, which is utilizable for the delivery of the pressure fluid in electronically controlled brake systems.

Prior Art [0002] The piston pumps used for known vehicle brake systems serve to control the pressure in wheel brake cylinders, where the piston pumps are provided for instance for returning brake fluid from one or more-wheel brake cylinders to a master cylinder.

[0003] Such piston pumps are known per se. They have a piston that is received axially displaceable in a cylinder bore of a pump housing. A bush is inserted into the pump housing, or the piston can be received directly in the pump housing.

[0004] By means of an eccentric drive mechanism, being pressed with its face end against the outer circumference of the eccentric element, the piston is driven to execute an axially reciprocating stroke motion, at which the rotary motion of a shaft driven by means of an electric motor is converted into a translational motion of a piston rod of the piston.

[0005] In the known piston pumps, a sealing package is arranged around the pump piston preventing fluid to flow from the pressure area to the atmospheric pressure from the eccentric area.

Disadvantages of prior art [0006] During the lifetime of a piston pump, because of the wear caused by the friction of the piston with the mentioned sealing due to the axial movement during the stroke motion of the piston, a certain volume of fluid is leaking trough. This has the disadvantage that the sealing ring can convey a leakage flow from the piston pump into the eccentric area. Once the fluid reaches the eccentric, it could be flushed into the motor, thus determining an early damage of the motor brushes.

[0007] Ano the r disadvantage is that damming of the sealing package leads to air aspiration into the piston pump in the reverse direction, which may impair pump performance.

Problem to be solved by the invention [0008] The objective of present invention is to provide a piston pump which solves the problem of early damaging of the motor, by leaking fluid which enters into the eccentric chamber, by collecting said leaking fluid into designated areas.

Summary of the invention [0009] The object of the invention is to create a piston pump with integrated leakage comprising a pump housing including an eccentric cavity for receiving a driving shaft rotatable about an axis of a pump actuating motor, and an eccentric member extending therefrom, a pump bore generally orthogonal to the shaft axis, being adapted to receive a pump piston driveable with the eccentric element to execute an axially reciprocating stroke motion in the cylinder bore along a common axis in response to eccentric motion and being in fluid communi cation at one end with said eccentric cavity and at another end with a compression chamber. Said compression chamber of the piston pump comprises two check valves, an outlet check valve and an inlet check valve, which controls the flow of a fluid through compression chamber; the piston pump further comprising a pump piston having and an end face resting against of said eccentric and another and on a piston return spring within said compression chamber. Said piston return spring having one end supported on an outlet check valve and its other end on said piston pressing the pump piston against the circumference of the eccentric element; a piston guide bush inserted into said pump housing arranged around the pump piston configured to displaceably guide the pump piston in said multiply stepped bore; a sealing package comprising an x-sealing ring, back sealing ring and piston sleeve arranged around the pump piston sealing said pump piston radially with respect to the pump bore preventing fluid to flow from the compression chamber towards the eccentric area; said piston pump further comprises at least one cavity in fluid communication with said pump bore for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber and the eccentric chamber.

Advantages of the invention [0010]By using the piston pump according to the invention, the leakage of fluid is prevented to enter into the eccentric chamber and therefore early damage of the motor due to leaking of the fluid is prevented.

Brief description of the drawings:

[0011] Further features and advantages of the invention will stem from the following description and claims with reference to the accompanying drawings in which the reference characters designate the same component throughout the figures.

FIG. 1 is a longitudinal cross-sectional view of a part of a piston pump according to one embodiment of the piston pump according to the present invention;

FIG. 2 is a longitudinal cross-sectional view of a second embodiment of the piston pump according to the present invention;

FIG. 3 is a longitudinal cross-sectional view of a third embodiment of the piston pump according to the present invention;

FIG. 4 is a longitudinal cross-sectional view of another embodiment of the piston pump according to the present invention .

[0012] List of reference numbers in the drawings:

1.	pump hous	ing
2 .	eccentric	chamber
3 .	p ump b o r e
4 .	pump pist	on
5 .	compress!	on chamber
6 .	o u r, 1 e r, c h	eck valve
7 .	inlet che	ck valve
8 .	piston re	turn sprin

9. piston guide bush

10 .	sealing pa	ckage
10.1	x-sealing	ring
10.1.	.1 x -sealing	ring
10.1.	,2 x -sealing	ring
10.2	back sealing	ring

10.3 piston sleeve bore

11.1 piston sleeve recesses flycut for fluid inlet leakage reservoir

Detailed description of the invention and of the embodiments [0013] The piston pump includes a drive shaft which is driven by an electric motor (not shown in the figures) . An eccentric element arranged on the drive shaft bears against a pump piston 4, the rotation of the drive shaft being converted into a stroke motion of the pump piston in the axial direction by the eccentric element.

[0014] The pump piston is received axially displaceable in a pump bore 3 within a pump housing 1 which may be for e.g. the valve block of an electronically controlled brake system, which forms the pump housing 1 of said pump piston 4.

[0015] The pump piston 4 rests with its end face oriented toward the circumference of the eccentric element, which is located in a cylindrical eccentric chamber 2 in the pump housing 1, into which pump piston protrudes with its end. The piston bore is in fluid communication with the eccentric chamber 2.

[0016] The pump bore 3 is generally orthogonal to the shaft axis and is adapted to receive a pump piston 4 driven by the eccentric element to execute an axially reciprocating stroke motion in the cylinder bore along a common axis in response to eccentric motion, being in fluid communication at one end with said eccentric cavity at another end with a compression chamber.

[0017] Said compression chamber 5 comprising two check valves, an outlet check valve 6 and an inlet check valve 7, which control the flow of a fluid through compression chamber 5.

[0018] The piston is reciprocally driven by the eccentric and alternatingly moves inwards into the piston bore 3 and outwards. In the outwards motion of the pump piston 4, the piston bore 3 receives fluid from an inlet check valve 7. In the subsequent inwards motion, the piston exerts a certain pressure onto the liquid and provides it to outlet check valve (6), which in turn is connected to a common liquid injection system.

[0019] On the inlet stroke of the pump, the piston moves towards the shaft, that creates a low-pressure region in the compression chamber, which allows the outlet check valve to settle onto its seat, the low pressure inside the pump chamber cause the inlet check valve to rise off of its seat and allows liquid to enter into the pump chamber.

[0020] The piston reverses direction during the pressure, or delivery stroke of the pump, the increased pressure inside the pump chamber causes the inlet check valve to close, and when the pressure inside the pump exceeds the pressure downstream, the outlet check valve is forcedly open.

[0021]An annular sealing package 10 and a piston guide bush 9 are arranged between the pump piston 2 and the pump housing 1, surrounding the pump piston 2 at the outer surface thereof. The piston guide bush 9 is inserted into said pump housing 1 arranged around the pump piston 4, and is configured to displaceably guide the pump piston 4 in said pump bore 2.

[0022] The piston guide bush 9 is inserted in such a way that it radially inwardly lays against the inner surface of the pump housing 1, so as the pump piston 4 to slide along and seal said inner surface of the piston guide bush 9.

[0023] The sealing package 10, comprising an X- sealing ring 10.1, a back sealing ring 10.2 and a piston sleeve 10.3, is arranged around the pump piston 4, radially sealing said pump piston 4 with respect to the pump bore 3, preventing fluid to flow from the compression chamber 5 towards the eccentric chamber 2.

[0024] The sealing package 10 is also located between the pump piston 4 and the pump housing 1, being retained fixedly in pump housing land so as the pump piston 4 to slide along and seal said inner surface of the sealing package 10.

[0025] During operation of the piston pump arrangement, a small quantity of hydraulic fluid may escape between the guides and the pistons . Said escaping hydraulic fluid passes into a space, which surrounds the cam.

[0026] The solution of the present invention provides a cavity comprising an additional volume for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber 5 and the eccentric chamber 2, said cavity being placed between high pressure side sealing chamber and the motor interface placed in the eccentric area respectively.

[0027]According to an advantageous embodiment of the invention, said cavity is defined by a radial cavity placed radially within said piston sleeve 10.3. being in fluid communication with said pump bore 3 for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber 5 and the eccentric chamber 2.

[0028]According to another advantageous embodiment of the invention, presented in the figure 1 said radial cavity is formed by at least one bore 11 placed radially within said piston sleeve

10.3 .

[0029]According to another advantageous embodiment of the invention (not shown in the figures) , said radial cavity is formed by multiple radial flycuts placed radially within body of said piston sleeve 10.3. in order to receive a certain volume of fluid therein.

[0030] It is furthermore of particular advantage that the piston sleeve 10.3 to have a certain number of radial bores or flycuts within its body in order to achieve a certain fluid volume retention .

[0031]According to another advantageous embodiment of the invention, represented in the fig. 2, said cavity comprising an additional volume for leakage of hydraulic fluid is further formed by a flycut 12 place in the pump housing 1 in fluid communication with said radial cavity. The flycut may have a cylindrical form, or any other suitable form to receive liquid. [0032]According to another advantageous embodiment of the invention, represented in the fig. 3 said x-sealing ring 10.1. is formed by two x-sealing rings 10.1.1; 10.1.2 having at their ends inner recesses, said two x-sealing rings 10.1.1; 10.1.2 being mounted adjacently such that form in-between a circular channel

11.1 surrounding said pump piston 4 forming said cavity comprising an additional volume for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber 5 and the eccentric chamber 2 .

[0033] It is furthermore advantageous that said x-sealing ring 10.1 to be formed from multiple x-sealing rings, preferably three x-sealing rings, having at their ends inner recesses being mounted adjacently such that form in-between a circular channel

11.1 surrounding said pump piston 4 forming said cavity comprising an additional volume for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber 5 and the eccentric chamber 2. In addition, an additional volume for leakage of hydraulic fluid is further formed by a flycut 12 place in the pump housing (1) in fluid communication with each said radial cavity.

[0034]According to another advantageous embodiment of the invention, the additional volume is defined by an additional bore 13 in the pump housing in fluid communication with the flycut 12, as shown in the fig. 4, that leads to a separate reservoir which could collect a lot more fluid than the variants presented in the fig. 1, fig. 2 and fig.3.

[0035] The liquid may be collected from the above mentioned cavities during the lifetime of the pump assembly.

[0036]While the description is at least with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the claims .

[0037] In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. Therefore, it is intended that the claims not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that all embodiments fall within the scope of the appended claims.

Claims

claims

1. Piston pump with integrated leakage comprising:

-a pump housing (1) comprising:

• an eccentric chamber (2) for receiving a driving shaft rotatable about an axis of a pump actuating motor, and an eccentric element extending therefrom;

• a pump bore (3) generally orthogonal to the shaft axis being adapted to receive a pump piston (4) driveable with the eccentric element to execute an axially reciprocating stroke motion in the pump bore along their common axis in response to eccentric motion • being in fluid communication with said eccentric cavity at one end and with a compression chamber (5) at another end;

• said compression chamber comprising two check valves, an outlet check valve (6) and an inlet check valve (7) , which control the flow of a fluid through said compression chamber (5) said pump piston (4) having one end face resting against-said eccentric element and another end face resting on a piston return spring (8) within said compression chamber (5), and pressing said pump piston (4) against the circumference of said eccentric element and said piston return sprincj (8) having its another end resting on the outlet check valve (6) ; -a piston guide bush (9) inserted into said pump housing (1) arranged around the pump piston (4) configured to displaceably guide the pump piston (4) in said pump bore (2;;

- a sealing package (10) comprising an x-sealing ring (10.1) , a back sealing ring (10.2) and a piston sleeve (10.3) arranged around the pump piston (4), sealing said pump piston (4) radially with respect to the pump bore (3) , preventing fluid to flow from the compression chamber (2) towards the eccentric chamber (2) characterized in that said piston pump further comprises at least one cavity (11, 11.1, 12, 13) in fluid communication with said pump bore (3) for receiving an additional volume of leakage fluid escaping during operation from the piston pump between compression chamber (5) and the eccentric chamber (2).

2. Piston pump according to the claim 1 characterized in that said at least one cavity (11, 11.1, 12, 13) is a radial cavity (11, 11.1) placed radially within said piston sleeve (10.3.).

3. Piston pump according to any of the preceding claims characterized in that said radial cavity (11, 11.1) is formed by at least one bore (11) placed radially within said piston sleeve (10.3 . )

4. Piston pump according to any of the preceding claims characterized in that the piston sleeve (10.3 . ) has 4 , or 6 radial bores within its body in order to receive a certain volume of fluid therein.

5. Piston pump according to any of the preceding claims characterized in that said radial cavity (11, 11.1) is formed by multiple radial flycuts placed radially within body of said piston sleeve (10.3.) in order to receive a certain volume of fluid therein.

6. Piston pump according to the claim 1 characterized in that the said piston sleeve (10.1.) is formed by 10.1. by multiple x-sealing rings, preferable three x-sealing rings, and more preferable two x-sealing rings (10.1.1; 10.1.2) having at their ends inner recesses, said two x-sealing rings 10.1.1; 10.1. being mounted adjacently such that said inner recesses form in-between a circular channel (11.1) surrounding said pump piston (4) forming said at least one cavity (11, 11.1, 12, 13).

7. Piston pump according to the claim 6 characterized in that one cavity (11, 11.1, 12, 13) is further formed by a flycut (12) place in the pump housing (1) in fluid communication with each said radial cavity (11, 11.1), said flycut (12) having a cylindrical form, or any other suitable form to receive liquid.

8. Piston pump according to the claim 6 characterized in that

5 one cavity (11, 11.1, 12, 13) is further formed by an additional bore (13) in fluid communication with said flycut (12) that leads to a separate reservoir in order to receive a certain volume of fluid therein.

9. Piston pump according to any of the preceding claims

10 characterized in that the piston housing is a valve support of a braking system.