Fluid line

Abstract

The invention relates to a fluid line (1), comprising a pipe (2), which has an inlet-side end segment (3) having a first connector (5) and an outlet-side end segment (4) having a second connector (10), wherein a cavity (17) bounded in the radially inward direction by at least one auxiliary element (16) is formed in the pipe (2). The problem addressed by the invention is that of minimizing the requirements for the suction performance of a pump that is used to convey a liquid through the pipe. This problem is solved in that a volume reduction element (18) is arranged in the cavity (17) at least in the region of the outlet-side end segment (4).

Claims

1. A fluid line comprising: a pipe which has an inlet-side end portion with a first connector and an outlet-side end portion with a second connector; at least one auxiliary element arranged in the pipe to form a radial inside wall of a radially delimited cavity, the pipe forming a radial outside wall of the cavity; and a volume reduction element being arranged in the cavity, at least in the region of the outlet-side end portion, wherein the volume reduction element has a recess extending along a length of the pipe to form a continuous flow channel, wherein the at least one auxiliary element comprises a heating rod, wherein the first connector has a first stub onto which the pipe is pushed and a connection geometry which is connectable to a pump, wherein the second connector has a second stub onto which the pipe is pushed and a connection geometry which is connectable to an injection device, and wherein the volume reduction element comprises at least a first axial portion that lies against the radial inside wall of the cavity and another axial portion that lies against the radial outside wall of the cavity.

2. The fluid line as claimed in claim 1, wherein the volume reduction element extends beyond the outlet-side end portion in a direction of the inlet-side end portion.

3. The fluid line as claimed in claim 2, wherein a gap is provided between axial portion of the volume reduction element and the another portion of the volume reduction element.

4. The fluid line as claimed in claim 3, wherein the pipe has a curved portion and the gap is arranged in the curved portion.

5. The fluid line as claimed in claim 1, wherein the volume reduction element extends over an entire length of the pipe.

6. The fluid line as claimed in claim 1, wherein the axial portion of the volume reduction element lies against the radial inside wall of the cavity under tension and the another axial portion of the volume reduction element lies against the radial outside wall of the cavity under tension.

7. The fluid line as claimed in claim 1, wherein the axial portion of the volume reduction element is connected to the radial inside wall of the cavity and the another axial portion of the volume reduction element is connected to the radial outside wall of the cavity.

8. The fluid line as claimed in claim 1, wherein the at least one auxiliary element at least intrudes into the second connector to form a ring gap with the connecting stub of the second connector, and wherein the ring gap has a cross-section area which corresponds to 0.7 to 1.3 times a cross-section area of the cavity formed by the volume reduction element.

9. A method to avoid a risk of damage to a injection device by freezing urea, the method comprising: arranging the fluid pipe according to claim 1 to transport a urea solution from a storage container to an injection device, injecting the urea solution into the exhaust tract of the diesel engine to reduce nitrous oxides; and after switching off the diesel engine, drawing back the urea solution from the fluid line so that at least the injection device is free from urea solution, wherein a pump, which is configured for drawing back the urea solution and for delivering urea solution from the storage container to the injection device with a specific pressure, has greater power for delivering the urea solution than for suctioning the urea solution.

Description

(1) The invention is described below with reference to a preferred exemplary embodiment in connection with the drawing. The drawing shows:

(2) FIG. 1 a highly diagrammatic section view of a fluid line, and

(3) FIG. 2 a section II-II from FIG. 1.

(4) A fluid line 1 has a pipe 2 which has an inlet-side end portion 3 and an outlet-side end portion 4.

(5) A first connector 5 is arranged at the inlet-side end portion 3. The first connector 5 has a stub 6 onto which the pipe 2 is pushed. The first connector 5 furthermore has a connection geometry 7 which is connected to a pump 8 (depicted diagrammatically). The pump 8, as indicated by a double arrow 9, has a reversible delivery direction, i.e. the pump 8 can deliver a fluid into the line 1 or it can extract the fluid from the line 1.

(6) A second connector 10 is arranged at the outlet-side end portion 4. The second connector 10 also has a stub 11 onto which the pipe 2 is pushed. The second connector 10 has a connection geometry 12 which is connected to an injection device 13. The injection device 13 has a nozzle 14 (depicted diagrammatically). A plurality of nozzles may also be provided. An electrically actuatable valve 15 is connected upstream of the nozzle 14, so that a fluid can be delivered from the line 1 via the injection device 13 in a targeted fashion.

(7) An auxiliary device 16 is arranged in the pipe 2, in the present case formed as a heating rod. The auxiliary device 16 is inserted both in the stub 6 of the first connector 5 and in the stub 11 of the second connector 10. The auxiliary device 16 leaves the first connector 5 and the second connector 10 at the side, i.e. out of the drawing plane, so that electrical energy can be introduced into the auxiliary element 16 at least in one of the connectors 5, 10, in order to generate a heating power.

(8) A cavity 17 is arranged between the pipe 2 and the auxiliary element 16. If just a single auxiliary element 16 is arranged in the interior of the pipe 2, the cavity 17 may be described as annular. This designation is however retained for the sake of simplicity and also applies if, instead of a single auxiliary element 16, for example two or more auxiliary elements 16 are provided, for example two heating wires running parallel.

(9) The cavity 17 has a volume which is delimited radially outwardly by the pipe 2 and radially inwardly by the auxiliary element 16. Since the auxiliary element 16 must also pass through the stubs 6, 11 of the connectors 5, 10, and the pipe 2 is pushed onto the stubs 6, 11 and therefore has a larger inner diameter than the stubs 6, 11, the cavity 17 necessarily has a relatively large radial extension and hence also a relatively large volume. A large volume imposes considerable requirements on the suction power of the pump 8.

(10) In order to keep these requirements low, a volume reduction element 18 is arranged in the cavity 17 and is formed from a plurality of portions 18a, 18b, 18c. A gap 19a is formed between the portions 18a and 18b. A gap 19b is arranged between the portions 18b and 18c. The gaps 19a and 19b each lie in curved portions 20, 21 of the pipe 2.

(11) On production of the fluid line 1, the pipe 2 is first extended straight. The auxiliary element 16 is also formed with a straight extension and can thus be inserted easily into the straight pipe 2. The portions 18a-18c of the volume reduction element 18 can in this state be introduced without difficulty into the interior of the pipe 2. Normally, the connectors 5, 10 are inserted in the end portions 3, 4 of the pipe 2. Then the pipe 2 is shaped and can be thermofixed. The gaps 19a, 19b do not disrupt the formation of the curved portions 20, 21 of the pipe 2.

(12) The volume reduction element 18 may have more than the three portions 18a, 18b, 18c shown. Outside the curved portions 20, 21 of the pipe 2, the portions may abut each other so that no significant gap results. The gaps 19a, 19b are shown excessively large here for reasons of clarity.

(13) The portions 18a, 18c lie with their radial inside against the auxiliary element 16. As can be seen from FIG. 2, the portion 18a of the volume reduction element has a recess 22 which extends along the length of the pipe 2.

(14) Between the portion 18a of the volume reduction element 18 and the pipe 2, a gap 23 is formed in which the volume available for the fluid has been greatly reduced. The drawing should not be interpreted as being to scale. However, there is a relatively large wetted surface area which increases the flow resistance for the fluid in the gap 23. This flow resistance may under certain circumstances lead to problems on extraction of the fluid by the pump 8. The recess 22 however provides a flow channel in which a far smaller wetted surface area is available, which therefore has a relatively low flow resistance, allowing the fluid to be extracted from the pipe 2.

(15) The portion 18a may therefore be formed as a C-shaped clip which simply consists of a pipe portion slotted in the longitudinal direction, the inner diameter of which is smaller than the outer diameter of the auxiliary element 16. The portion 18a of the volume reduction element 18 may then be clipped onto the auxiliary element 16 before the auxiliary element 16 is pushed into the pipe 2. The portion 18a then adheres to the auxiliary element 16 with a certain tension.

(16) Naturally, the portion 18a may also be glued or welded to the auxiliary element 16 if necessary.

(17) The portion 18c of the volume reduction element is configured accordingly and clipped onto the auxiliary element 16. The portion 18b however lies with its radial outside against the radial inside of the pipe 2. Here too, the portion 18b may be provided with a radially outward pretension so that it lies with a certain tension against the inside of the pipe 2. Here again, advantageously a recess 22 is provided which forms a flow channel.

(18) Normally, all portions 18a-18c are either fixed to the auxiliary element 16 or lie against the inside of the pipe 2. The depiction in FIG. 1 was selected to show that there are various ways of positioning the portions 18a-18c in the cavity 17.

(19) The depiction in the drawing is not to scale.

(20) It is clear that the auxiliary element 16 enters the second connector 10 and forms a ring gap 24 with the connecting stub 11. This ring 24 has a cross-section area which corresponds to 70% to 130% of the cross-section area of the gap 23. In other words, the cross-section area of the ring gap 24 is approximately the same size as the cross-section area of the gap 23.