Piston pump for delivering fluids, and associated vehicle brake system

Abstract

A piston pump for delivering fluids includes a piston, a cylinder element and a pressure chamber which is arranged between an inlet valve and an outlet valve and is closed by a cover, wherein a throttling mechanism for throttling the fluid flow is provided in the fluid flow downstream of the outlet valve, and a vehicle brake system has a piston pump of this type. The throttling mechanism includes a movable annular disc which is guided on the cylinder element and the internal diameter of which is adapted to the external diameter of the cylinder element, wherein the axial travel of the annular disc sets a variable first throttle cross section.

Claims

1. A piston pump for delivering fluids, comprising: a piston; a cylinder element in which the piston is operable; a pressure chamber defined in the cylinder element and arranged between an inlet valve and an outlet valve; a cover arranged at an end portion of the cylinder element so as to close the pressure chamber; and a throttling mechanism configured to throttle a fluid flow, the throttling mechanism being provided in the fluid flow downstream of the outlet valve, wherein the throttling mechanism includes a movable annular disk guided so as to move axially on the cylinder element, wherein an internal diameter of the movable annular disk is adapted to an external diameter of the cylinder element, and wherein an axial travel of the annular disk sets a variable first throttle cross section, and wherein the piston pump further comprises a pretension device configured to dynamically throttle the fluid flow which is guided through at least one outflow opening between the cover and the cylinder element by pressing the annular disk axially against a throttle point arranged on the cover.

2. The piston pump as claimed in claim 1, wherein the pretension device includes a spring element, which defines the axial travel of the annular disk.

3. The piston pump as claimed in claim 1, wherein the pretension device includes one of a spiral spring, a leaf spring, a cup spring, and an undulating ring.

4. The piston pump as claimed in claim 2, further comprising: a ring shoulder structure defined in the exterior surface of the cylinder element and configured to support the pretension device.

5. The piston pump as claimed in claim 1, wherein a face of the cover forms the throttle point.

6. A vehicle brake system comprising: at least one piston pump including: (i) a piston; (ii) a cylinder element in which the piston is operable; (iii) a pressure chamber arranged between an inlet valve and an outlet valve; (iv) a cover arranged at an end portion of the cylinder element so as to close the pressure chamber; and (v) a throttling mechanism configured to throttle a fluid flow, the throttling mechanism being provided in the fluid flow downstream of the outlet valve, wherein the throttling mechanism includes a movable annular disk guided so as to move axially on an outer circumferential surface of the cylinder element, wherein an internal diameter of the movable annular disk is adapted to an external diameter of the outer circumferential surface, wherein an axial travel of the annular disk sets a variable first throttle cross section, and wherein the piston pump further comprises a pretension device configured to dynamically throttle the fluid flow which is guided through at least one outflow opening between the cover and the cylinder element by pressing the annular disk axially against a throttle point arranged on the cover.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a diagrammatic perspective view of an embodiment example of a piston pump according to the disclosure for delivering fluids.

(2) FIG. 2 shows a perspective cross section through a rear region of the piston pump according to the disclosure shown in FIG. 1 for delivering fluids.

DETAILED DESCRIPTION

(3) As evident from FIGS. 1 and 2, a piston pump 1 according to the disclosure for delivering fluids comprises a piston 3, a cylinder element 5, a sealing element 7 and a fluid filter 9 which are arranged in front of an inlet opening (not visible), behind which is arranged an inlet valve (not visible). Between the inlet valve (not shown) and an outlet valve (not shown), in the interior of the cylinder element 5 is arranged a pressure chamber 5.2 which is closed by a cover 16 in which the outlet valve is arranged. In the depiction only one sealing seat 20 of the outlet valve arranged at an outlet opening 5.4 of the pressure chamber 5.2 is shown. In addition the outlet valve usually comprises a closing body, a pretension device acting on the closing body and means for supporting the pretension device. In the fluid flow 18 downstream of the outlet valve are provided means 10 for throttling the fluid flow 18 in order to reduce the noise formation.

(4) The cover 16 can in the known manner be produced either by material removal or by shaping, wherein from an economic aspect the shaping process is suitable for large quantities. The outflow geometry influences the noise behavior of the piston pump and is therefore formed suitably. In piston pumps known from the prior art, this element is usually a suitable constriction of the outflow channel which then constitutes a throttle effect. This throttle effect creates a hydraulic low-pass filter which has a positive effect on the undesirable noise development. The behavior of the dynamic viscosity of the brake fluid in the range between 0 and 120 C. can be regarded as almost constant and the optimum throttling effect is defined for this temperature range. As a result of the great change in kinematic viscosity of the brake fluid over the required temperature range from 40 to 120 C., the throttlein particular at low temperaturesstresses the pressure-loaded components of the piston pump and the entire pump drive. Due to the reduced cross section, at lower temperatures a significantly increased fluid friction is indicated which leads to a significant rise in pump internal pressure and results in the stresses mentioned above.

(5) According to the disclosure, the throttling means 10 comprise a movable annular disk 14 guided on the cylinder element 5, the internal diameter of which is adapted to the external diameter of the cylinder element 5. Here the axial travel of the annular disk 14 defines a variable first throttle cross section. The piston pump 1 according to the disclosure shown can for example be arranged in a receiver bore (not shown) of a pump housing or a fluid block. Transverse-running pressure medium channels can open into the receiver bore, through which fluid is guided via the fluid filter 9 to the inlet opening of the piston pump 1 or away from the at least one outflow opening 16.6 of the piston pump 1.

(6) As further evident from FIGS. 1 and 2, for dynamic throttling of the fluid flow 18 guided through the at least one outflow opening 16.6 between the cover 16 and cylinder element 5, a pretension device 12 presses the annular disk 14 against a throttle point 16.4 arranged in the cover 16. In the embodiment example shown, the pretension device 12 is formed as a cup spring. Alternatively the pretension device 12 can be designed as a spiral spring and/or leaf spring and/or undulating ring. The fluid can be guided via several fluid channels 16.2 from the outlet valve seat 20 to the outflow opening 16.6 when the outlet valve is opened.

(7) As further evident from FIG. 2, the annular disk 14 is guided over a guide face 14.2 of the cylinder element 5 and in the initial state of the pretension device 12 is pressed axially with a sealing face 14.4 against the throttle point 16.4 on the cover 16, which in the embodiment example shown is formed by a face of the cover 16. The axial travel of the annular disk 14 is defined by the selected spring properties of the pretension device 12. Furthermore means 5.6 for supporting the pretension device 12 formed as a spring element in the embodiment example shown are formed as a ring shoulder on the periphery of the cylinder element 5.

(8) In addition the annular disk 14 can have at least one opening which fixedly predefines a second throttle cross section. The second throttle cross section can be optimized for a volume flow in a predefined temperature range. Thus the second throttle cross section can for example be optimized for a volume flow in a temperature range from 0 to 120 C. Because of temperature change, the viscosity of the fluid also changes and hence the flow resistance at the second fixedly predefined throttle cross section of the annular disk 14. Thus the annular disk 14 is now displaced additionally axially so that via the pretension device 12, the free cross section can be enlarged or a new free cross section set. As a result the internal pressure of the piston pump 1 advantageously does not rise, in particular at low temperatures, so that other components of the piston pump 1 are not damaged.

(9) Embodiments of the present disclosure advantageously allow optimum use of the construction space and excellent NVH behavior. By means of the sprung annular disk, the internal pressure of the piston pump can advantageously be reduced when the fluid is in a highly viscous state. As a result the drive power and the load on the force-transmitting components such as bearings, pistons, high pressure sealing rings etc. are reduced. This can be utilized for cost saving in future constructions with suitable design.