Pump device

Abstract

Pumping device for fluid, in particular for diesel fuel, with a pump piston (16) which is longitudinally movable within a pump housing (10) by means of an actuating device (36, 38) and which, depending on its position within the pump housing (10), separates individual pump chambers (26, 28) with different volumes from one another, at least temporarily. The pump piston (16) has a pressure limiting device (72) which, if a predefinable pump pressure is exceeded in one of the pump chambers (26), provides pressure relief for the fluid towards the other pump chamber (28) adjacent to the first pump chamber (26).

Description

[0001] The invention relates to a pumping device for fluid, in particular for diesel fuel, with the features in the preamble of claim 1.

[0002] EP 3 352 877 B1 discloses a filter device, in particular intended for use with diesel fuels, with a filter element that can be exchanged in a filter housing, wherein a fluid pump device with two pump chambers is provided as part of the filter device, which are fluid-tightly separated from each other at least in one of its two directions of travel by means of a pump piston that is longitudinally movable in these chambers, wherein a valve is provided for each pump chamber which opens or closes in the opposite direction to the other valve when the pump device is actuated, and wherein at least one of the valves is part of the filter element and, in its open position, directs fluid into its assigned pump chamber and, in its closed position, blocks this path.When changing a filter element, and if air is unintentionally introduced into the filter housing, this air is manually directed into the pump chamber via the open valve when the pump is activated, thus removing it from the system so that the fuel supply system can be restarted without further ado.

[0003] US 6,186,118 B1 describes a pumping device for fluid, in particular for diesel fuel, with the features in the preamble of claim 1, comprising a pump piston that is longitudinally movable within a pump housing by means of an actuating device and that, depending on its position within the pump housing, separates individual pump chambers with different volumes from one another, at least temporarily, wherein the respective fluid connection in the pump piston can be covered by a control means which, as part of the pressure limiting device, releases the respective fluid connection in one pump chamber at a predefinable pressure threshold and allows backflow to the other pump chamber, wherein an energy storage device, preferably in the form of a compression spring, serves to set the predefinable pressure threshold, wherein the control means is formed from a control disk whose outer diameter is smaller than the outer diameter of the pump piston.that a circumferential annular gap is formed between the control disc and the inner circumferential side of the pump housing, wherein the pump piston has a pressure limiting device which, when a predefinable pump pressure is exceeded in one of the pump chambers, provides pressure relief for the fluid towards the other pump chamber adjacent to the first pump chamber, and wherein the actuating device has an actuating rod with an operating element outside the pump housing.

[0004] Further pump devices are described in DE 1 166 004 B, WO 2015 / 071397 A1, EP 3 352 877 B1, DE 10 2009 040 655 B4 and US 9 951 730 B2.

[0005] Based on this state of the art, the invention aims to further improve the known device solution relating to pump operation.

[0006] A pump device with the features of claim 1 in its entirety solves such a problem.

[0007] According to the characterizing feature of claim 1, it is provided that the actuating rod is guided at its one free end with a drag clearance in the pump piston such that, during a return stroke, the control disc lifts off the pump piston against the action of the energy storage device, releasing the respective fluid connection, and during a delivery stroke, under the action of the energy storage device and with "zero" clearance, the respective fluid connection is closed.

[0008] By incorporating a pressure-limiting device into the pump piston, which, when a predefined pump pressure is exceeded in one of the pump chambers, provides pressure relief for the fluid towards the other pump chamber adjacent to the first, a common technical problem is solved: namely, that the pressure applied by a hand pump to a fuel system can become unacceptably high, potentially damaging seals and other components sensitive to excessive pressure within the supply system. This risk is effectively countered by the pressure-limiting device according to the invention, and unacceptably high pressures during pump operation are reliably prevented.

[0009] In a preferred embodiment of the pump device according to the invention, the pump piston is guided longitudinally within the pump housing by means of a sealing device. The pump housing has at least one fluid connection which, during a return stroke of the pump piston, connects the adjacent pump chambers to each other in a fluid-carrying manner. One of these chambers has a progressively smaller volume, and the other a progressively larger volume. This arrangement allows the pump housing to be filled with fluid from one inlet side for subsequent discharge by moving the pump piston in an actuation direction.

[0010] Each fluid connection in the pump piston can be covered by a control device that, acting as a pressure limiter, releases the respective fluid connection in one pump chamber at a predefined pressure threshold, allowing backflow to the other pump chamber. In this way, the fluid previously drawn into the pump housing can be manually expelled in the opposite direction to an outlet or consumer side by actuating the pump piston. If this results in an unwanted pressure increase on the outlet or discharge side, the pressure limiter in the pump piston is activated, and fluid exceeding the pressure can flow back to the pressure-relieved outlet side of the pump housing, which is open to the air from the pump piston.This ensures reliable pressure limitation on the delivery side, protecting any pressure-sensitive components in the downstream supply circuit from pressure-related damage or even destruction. This approach is unprecedented in the prior art.

[0011] A particularly simple mechanism for the pressure limiting function of the pump device results from the fact that an energy storage device, preferably in the form of a compression spring, serves to set the pressure threshold value and furthermore a control means is used which is formed from a control disc whose outer diameter is so smaller than the outer diameter of the pump piston that a circumferential annular gap is formed between the control disc and the inner circumferential side of the pump housing.In this way, during the usual forward pump movement, the spring-loaded control disc can initially block fluid connections in the pump piston, so that pressure-building pumping by hand towards the discharge side is effectively possible, and if the pressure limiting function is activated, the control disc is opened and the fluid connections thus released allow the backflow of high-pressure fluid from the discharge side to the relief side of the pump piston within the pump housing.

[0012] In a further preferred embodiment of the pump device according to the invention, it is provided that after completion of the pumping process, which may include several pump strokes with the pump piston, the piston is moved to a position within the pump housing in which both pump chambers are open, thus establishing a direct fluid-carrying connection between the inlet of the pump housing and its outlet. This places the pump piston in a neutral position within the pump housing, allowing a main fluid flow to pass unimpeded from the inlet side to the outlet side of the pump housing.

[0013] Further embodiments of the pump device according to the invention are the subject of the other dependent claims.

[0014] Im The pump device according to the invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing, including longitudinal sections. The drawings show, in a general and not to-scale representation, the Fig. 1 shows the pump device in a blocked flow position for a scheduled filter element change; Figs. 2 and 3 show the pump device after the Fig. 1 once in a filling position or in pump operation; Fig. 4 one of the Fig. 1 bis 3 corresponding illustration with the pressure limiting function shown; and Fig. 5 the pump device according to the Fig. 1 bis 4 in a neutral position releasing a main fluid volume flow, wherein in the Fig. 2 bis 5 The respective main flow direction is shown in arrow representation.

[0015] The Fig. 1 Figure 1 shows the essential components of the pump device in a longitudinal section view. The pump device comprises a pump housing 10 with a partially cup-shaped base housing 12, which is fluid-tightly sealed to the outside by a cover part 14. A pump piston 16 is longitudinally guided within the pump housing 10 and can be actuated by means of an actuating device designated 18. For this purpose, the base housing 12 has a cylindrical cavity 20, which, in the direction of view towards the Fig. 1 Looking to the left, the space 22 widens along a conical section into a fluid chamber 24, the diameter of which is larger than the diameter of the cylindrical cavity 20. In this way, the pump piston 16 divides the spaces 20, 22, and 24 shown into two pump chambers, namely one pump chamber 26 and the other pump chamber 28. Depending on the position of the pump piston 16 in the base housing 12, the volume of either pump chamber 26 or the other pump chamber 28 is increased or decreased accordingly.

[0016] As the Fig. 1 As further shown, an inlet 30, in the form of a fluid-carrying channel, opens into one cavity 20. At its free upper end, this channel is equipped with a conventional check valve 32. In contrast, an outlet 34, also in the form of a fluid channel, opens into the enlarged fluid chamber 24. This outlet leads to a consumer (not shown in detail) that is connected to the pumping device and could, for example, be part of a conventional (diesel) fuel supply system.

[0017] The actuating device 18 has an actuating rod 36, which is provided at one free end with a handle 38, for example in the form of an actuating knob or button. At its other opposite end, the actuating rod 36 is tapered in diameter and thus transitions into a cylindrical pin guide 40 for the pump piston 16. The pin guide 40, which tapers to a point at its free end, has an annular stop disc 42 that is wider than the free diameter of the pin guide 40 and thus provides a stop for the pump piston 16 in its position, viewed from the Fig. 1 seen, forming the far left stop position. In the Fig. 1 In the central position shown, however, the pump piston 16 is shown in its far right position and the distance between the front of the pump piston 16 and the adjacent opposite back of the stop disk 42 forms a kind of drag clearance 44 for the movement of the pump piston 16, the function of which will be explained in more detail below.

[0018] The pump piston 16 is formed from a disc-shaped, cylindrical plate which carries a sealing device 46 on its outer circumference in the form of two conventional sealing rings spaced apart from each other and received in radial grooves of the pump piston 16. The pump piston 16 also has at least one continuous axial bore 48, wherein preferably several such axial bores 48 are grouped concentrically around a longitudinal axis 50 of the pump device, which is also simultaneously the actuating axis for the actuating device 18. In the Fig. 1 In the central position shown, the respective axial bore 48 is covered by a control element 52 in the form of a control disc 54. The outer diameter of the control disc 54 is smaller than the outer diameter of the pump piston 16, so that a circumferential annular gap 56 is formed between the outer circumference of the control disc 54 and the cylindrical inner circumference of the base housing 12, which encompasses the cavity 20 in the pump housing 10. The annular gap 56 serves to allow fluid to flow from one pump chamber 26 as needed, which is evident from the Fig. 4 as will be explained in more detail, to bring in the direction of the other pump chamber 28, namely via the respective axial bore 48, which is controlled by the control disk 54 for a fluid passage.

[0019] The control disc 54 is supported with one plate side against the corresponding piston side of the pump piston 16 and with the other side against an energy storage device in the form of a compression spring 58. For this support by the compression spring 58, it is held at its other free end against a further stop disc 60, which is always pressed against a snap ring 62, which engages in the actuating rod 36, by means of the compression spring 58. Furthermore, the control disc 54 is supported in a central region by a radial extension 64, which extends between the pin guide 40 and the other parts of the actuating rod 36 in the direction of the handle 38, with a corresponding radial recess 66 in the pump piston 16 for guiding the extension 64. In the position shown after the Fig. 1 The adjacent piston side of the pump piston 16 is flush with the contact surface of the widening 64, against which the control disc 54 is applied in a vertical plane under the force of the compression spring 58.

[0020] The actuating rod 36 can be moved into a fully retracted position by means of the handle 38, as shown in the illustration. Fig. 5 The handle 38 is brought into position, resting on the cover part 14, and a cylindrical projection 68 of the cover part 14 with an internal thread 70 allows it to be screwed into place via threaded sections of the handle 38 and the actuating rod 36 (not shown) in this area. In this way, a locked position of the handle 38 and the actuating rod 36 on the pump housing 10 is achieved, and the pump piston 16 moves completely from the cavity 20 into the widened fluid chamber 24. This will be explained in more detail later. Furthermore, the actuating rod 36 is guided in the cover part 14 along a seal (not shown), of which only the associated annular groove 71 is shown in the figures. In addition, the pump device shown, with its essential components, incorporates a pressure limiting device designated as a whole by 72.

[0021] First, the filling of the pump housing 10 is determined based on the piston position after the Fig. 2 described in more detail. For filling, the piston or actuating rod 36 is moved from its position to the following position by means of the handle 38. Fig. 1 As the actuating rod 36 moves to the right, fluid is drawn from the inlet 30 into the other pump chamber 28 via the check valve 32. Since the actuating rod 36 moves to the right, its widening 64 also moves the control disc 54 to the right, so that fluid enters the space created between the control disc 54 and the exposed piston side of the pump piston 16 via the permanently present annular gap 56. From there, it flows through the individual axial bores 58 in the pump piston 16 into one pump chamber 26. In this way, one pump chamber 26 is completely filled with fluid in the direction of the outlet 34. The corresponding fluid flow direction is shown in the Fig. 2 The direction of flow is indicated by arrows, and the backflow of fluid volume from the other pump chamber 28 towards the inlet 30 is effectively prevented by the aforementioned check valve 32. During this return stroke, the widening 64 disengages from the corresponding recess 66 in the pump piston 16, and the stop disk 42 comes into contact with one free end face of the pump piston 16. Furthermore, the cylindrical pin guide 40 is retracted towards the pump piston 16. Additionally, the control disk 54 of the control mechanism 52 pre-tensions the compression spring 58, which is supported at its other free end by the further stop disk 60 on the actuating rod 36.

[0022] The fluid previously supplied to chamber 28 via inlet 30 is displaced by the return stroke of the pump piston 16 through the axial bores 48 towards chamber 26, with the check valve 32 closed. If, subsequently, the process is carried out according to the diagram... Fig. 3 the piston or actuating rod 36 is moved from its right position to the other position by means of the handle 38. Fig. 2 to the left according to the representation after the Fig. 3 When pressed, the fluid located in a pump chamber 26 is expelled, as shown by the arrow, through the outlet 34 in the pump housing 10 towards a hydraulic consumer or a fluidic working machine (a diesel engine). The axial bores 48 in the pump piston 16 are again closed by the control valve 54, and the cylindrical pin guide 40 is, as shown, after the Fig. 1 again in their foremost left position; as shown in the illustration after the Fig. 1 Furthermore, the control slide 54 is held in the position closing the axial bores 48 by the force of the relaxing compression spring 58.

[0023] During the movement of the pump piston 16 from right to left, a vacuum is created in the rear area of ​​the pump volume, i.e., in the other pump chamber 28, which opens the check valve 32 so that fluid, such as fuel, can flow into the other pump chamber 28, while at the same time, as already explained, the front fluid volume in one pump chamber 26 decreases and is conveyed further via the outlet 34 by pushing the corresponding amount of fluid out of the pump housing 10 by the pump piston 16.

[0024] The sequence of actions according to the Fig. 2 und 3 This process is repeated alternately until the desired delivery volume is reached at outlet 34 or until the pressure limiting device 72 is activated, which is indicated by the Fig. 4 This will be explained in more detail below. The pump chamber 28 is alternately emptied and refilled with fluid on the inlet side.

[0025] Provided that the pump pressure on the side of outlet 34, starting from the position after the Fig. 3 If an impermissibly high value is reached, this has an effect according to the arrow representation after the Fig. 4 The fluid flows through the axial bores 48 onto the control slide 54 of the control means 52, which moves to the right in the opposite direction to the action of the compression spring 58. The fluid then passes through the axial bores 48 and the exposed space between the pump piston 16 and the control slide 54, via the permanent annular gap 56, to the side with the other pump chamber 28. In this way, pressure is relieved from one pump chamber 26 towards the other pump chamber 28, and an impermissibly high pressure on the outlet 34 side is reduced. Depending on the selected spring characteristic for the compression spring 58, the pressure threshold for activating the pressure limiting device 72 can be specified. Furthermore, the Fig. 4 As shown, the actuating rod 36 with its cylindrical pin guide 40 remains in a sliding position according to the Fig. 1 and / or 3. According to its function shown, the pressure limiting device 72 essentially consists of the spring-loaded control means 52, which opens or closes the fluid connection in the pump piston in the form of the respective axial bore 48 depending on the pressure situation in the pump housing.

[0026] After the described filling process and the possible reduction of impermissible pressure peaks by means of the pressure limiting device 72, the actuating rod or piston rod 36 can be moved as shown in the illustration. Fig. 5 now shift completely to the left and is screwed into the projection 68 of the cover part 14 using the handle 38 with the internal thread 70. Thus, according to the illustration, the Fig. 5 The pump piston 16 with the pressure limiting device 72 is fully inserted into the fluid chamber 24, which widens conically at the inlet, and is thus brought into a neutral position in which a main fluid flow can flow unimpeded from the inlet 30 towards the outlet 34, as illustrated by arrows. Both pump chambers 26 and 28 are equally permeated by the fluid, as is the outer circumference of the pump piston 16 with the associated pressure limiting device 72.

[0027] Finally, it should be mentioned that in the piston representation according to the Fig. 1 The volume flow between inlet 30 and outlet 34 is blocked to allow for a filter element change (not shown) without interference. After the element change, it is then possible, as shown by the Fig. 2 bis 5described, fluid, such as fuel, is returned to the fuel supply system (common rail), which is simultaneously "vented".

[0028] The present solution according to the invention, in which a pressure limiting device 72 is integrated into a pump piston 16 of a pump device, allows the described pressure limiting to be implemented in a simple and space-saving manner, and additional costly pressure limiting valves can be dispensed with. Furthermore, in an embodiment not shown, it is also possible to move the handle 38 and / or the actuating rod 36 back and forth by means of a motorized drive, so that manual pump operation is not absolutely necessary.

Claims

1. Pump device for fluid, in particular for diesel fuel, having a pump piston (16) which is guided in a longitudinally displaceable manner in a pump housing (10) by means of an actuating apparatus (18) and which at least temporarily separates individual pump chambers (26, 28) with different volumes inside the pump housing (10) from one another as a function of its travel position, the pump piston (16) comprising a pressure-limiting apparatus (72), which, if a predefinable pump pressure is exceeded in one of the pump chambers (26), provides pressure relief for the fluid in the direction of the other pump chamber (28) adjacent to the first pump chamber (26), the respective fluid connection in the pump piston (16) being able to be covered by a control means (52), which, as part of the pressure-limiting apparatus (72), releases the respective fluid connection (48) in one pump chamber (26) at a predefinable pressure threshold and allows fluid to flow back to the other pump chamber (28), an energy accumulator, preferably in the form of a compression spring (58), serving to set the predefinable pressure threshold, the control means (52) being formed by a control disc (54), the outer diameter of which is smaller than the outer diameter of the pump piston (16) such that a peripheral annular gap (56) is formed between the control disc (54) and the inner circumferential side of the pump housing (10), and the actuating apparatus (18) comprising an actuating rod (36) having a control unit (38) outside the pump housing (10), characterised in that one free end of the actuating rod (36) is guided in the pump piston (16) with a trailing clearance (44) such that, on a return stroke, the control disc (54) lifts off the pump piston (16) against the action of the energy accumulator (58), releasing the respective fluid connection (48), and, on a delivery stroke, closes the respective fluid connection (48) under the action of the energy accumulator (58) and with 'zero' clearance.

2. Pump device according to claim 1, characterised in that the pump piston (16) is guided in a longitudinally displaceable manner by means of a sealing apparatus (46) in the pump housing (10), having at least one fluid connection that connects the mutually adjacent pump chambers (26, 28) to one another in a fluid-conveying manner in a return stroke movement of the pump piston (16), one (28) of said chambers assuming a gradually smaller volume, while the other (26) assumes a gradually larger volume.

3. Pump device according to either claim 1 or claim 2, characterised in that, if the pump pressure is below the pressure threshold, the control means (52) keeps the respective fluid connection (48) closed and, by means of the actuating apparatus (18), pushes the fluid contained in one pump chamber (26) in the direction of the outlet (34) of the pump housing (10) from the latter.

4. Pump device according to any of the preceding claims, characterised in that, on completion of the pump operation, in particular as part of a filling operation, the pump piston (16) releases both pump chambers (26, 28) by means of the actuating apparatus (18) and a direct fluid-conveying connection is established between an inlet (30) of the pump housing (10) and its outlet (34).

5. Pump device according to any of the preceding claims, characterised in that a check valve (32) is inserted in the inlet (30) of the pump housing (10), said check valve opening on a delivery stroke with the pump piston (16) and releasing the fluid path from the inlet (30) into the other pump chamber (28) and closing said fluid path on a return stroke.

6. Pump device according to any of the preceding claims, characterised in that, in order to achieve the trailing clearance (44), the actuating rod (36) passes through the pump piston (16) in the direction of one pump chamber (26) with a predefinable projection and, as part of the return stroke, the aforementioned projection becomes zero until the front end region (40, 42) of the actuating rod (32) stops against the pump piston (16).

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