Pre-treatment assembly and method for pre-treating a compensation device

Abstract

 A Pre-treatment assembly for pre-treating a compensation device (30) having a variable length (L) comprises an assembly body, a pressure transferring body (84), an actor (90), and a heating device (56). The assembly body comprises a guidance (58) and a positive stop (60). The pressure transferring body (84) is coupled to the guidance (58) movable towards the positive stop (60). The actor (90) is coupled to the pressure transferring body (84). The pressure transferring body (84), the heating device (56), and the positive stop (60) are formed and arranged in such a way that in a given state of the pre-treatment assembly the compensation device (30) is thermally coupled to the heating device (56) while the actor (90) presses the compensation device (30) via the pressure transferring body (84) against the positive stop (60) in such a way that the length (L) of the compensation device (30) decreases.

Description

[0001] The invention relates to a pre-treatment assembly and a method for pre-treating a compensation device. The compensation device has a variable length.

[0002] The object of the invention is to create a pre-treatment assembly and a method for pre-treating a compensation device of an injector which enables a stable and precise function of the compensation device.

[0003] The object of the invention is achieved by the features of the independent claims 1 and 11. Advantageous embodiments of the invention are given in the sub-claims.

[0004] The invention is distinguished concerning a first aspect of the invention by a pre-treatment assembly for pre-treating a compensation device. The compensation device has a variable length. The pre-treatment assembly comprises an assembly body, a pressure transferring body, an actor, and a heating device. The assembly body comprises a guidance and a positive stop. The pressure transferring body is coupled to the guidance movable towards a positive stop. The actor is coupled to the pressure transferring body. The pressure transferring body, the heating device, and the positive stop are formed and arranged in such a way that in a given state of the pre-treatment assembly the compensation device is thermally coupled to the heating device while the actor presses the compensation device via the pressure transferring body against the positive stop in such a way that the length of the compensation device decreases.

[0005] The compensation device may be used for compensating a change of an axial length of an injector, for example because of a thermal expansion of the injector. The pre-treatment assembly enables to expose the compensation device to working conditions of the compensation device in the injector. This is especially advantageous, if the compensation device changes its behavior after being heated and/or after being pressed the first time. Then, the pre-treatment assembly contributes to a stable behavior and so to a precise function of the compensation device in the injector.

[0006] In an advantageous embodiment of the first aspect of the invention the guidance has a guidance recess which at least partly takes in the pressure transferring body. This enables in a simple way a proper guiding of the pressure transferring body.

[0007] In a further advantageous embodiment of the first aspect of the invention the guidance recess and the pressure transferring body are formed and arranged in such a way that the pressure transferring body protrudes from both axial ends of the guidance recess. This enables to act easily on the pressure transferring device from that side of the guidance facing away from the positive stop.

[0008] In a further advantageous embodiment of the pre-treatment assembly the actor comprises a pre-treatment spring which radially surrounds a part of the pressure transferring body. The assembly body has a step which forms a first spring rest for the pre-treatment spring. The pressure transferring body has a second spring rest for the pre-treatment spring. This enables in a simple way to press the pressure transferring body against the compensation device.

[0009] In a further advantageous embodiment of the first aspect of the invention the pressure transferring body is piston-shaped having a piston head and a piston rod. The pre-treatment spring radially surrounds a part of the piston rod. The piston head comprises the second spring rest for the pre-treatment spring. This contributes to a proper pressure transfer from the pre-treatment spring to the pressure transferring body.

[0010] In a further advantageous embodiment of the first aspect of the invention the heating device comprises a tube-shaped heating body which has at least one heating line. This enables a proper thermal coupling of the compensation device to the heating device.

[0011] In a further advantageous embodiment of the first aspect of the invention the heating line is surrounded by a material of the tube-shaped heating body. So, the material of the tube-shaped heating body protects the heating line. This contributes to a long lifetime of the heating device.

[0012] In a further advantageous embodiment of the first aspect of the invention the tube-shaped heating body is formed in such a way that the compensation device arranged in the tube-shaped heating body has a clearance fit to an inner wall of the tube-shaped heating body. This enables simply and effectively the proper thermal coupling of the compensation device and the heating device.

[0013] In a further advantageous embodiment of the first aspect of the invention a thermal conductor is arranged in such a way that the thermal conductor couples the compensation device with a wall of the recess of the tube-shaped heating body.

[0014] This enables the proper thermal coupling of compensation devices with different dimensions. The thermal conductor in this way works as an adapter for coupling different compensation devices with the pre-treatment assembly.

[0015] In a further advantageous embodiment of the first aspect of the invention the heating line comprises an electric conductor. This enables simply a heating of the heating device.

[0016] In a further advantageous embodiment of the first aspect of the invention the pre-treatment assembly comprises a mechanical stop for the pressure transferring body. The mechanical stop is formed and arranged in such a way that the movement of the pressure transferring body towards the positive stop is limited by the mechanical stop. This contributes to apply a given stress on the compensation device by the pressure transferring body in an easy way.

[0017] The invention is distinguished concerning a second aspect of the invention by a method of pre-treating the compensation device for the injector. For pre-treating the compensation device, the compensation device is arranged in the pre-treatment assembly. A force is applied on a first axial end of the compensation device. The compensation device gets heated while the force is applied on the first axial end of the compensation device.

[0018] Advantageous embodiments of the invention are explained in the following with the aid of schematic drawings.

Figure 1

an injector,

Figure 2

a first embodiment of a pre-treatment assembly,

Figure 3a

second embodiment of the pre-treatment assembly,

Figure 4a

flow chart of pre-treating a compensation device.

[0019] Elements of the same design and function that appear in the different illustrations are identified by the same reference characters.

[0020] An injector (figure 1) comprises an injector housing 1, a nozzle body 4 having a nozzle body recess 6, a needle 8, a needle spring 10, and a spring washer 12. The needle 8 is arranged movable in axial direction in the nozzle body recess 6. The needle spring 10 is arranged circumferential the needle 8 and in axial direction intermediate the nozzle body 4 and the spring washer 12. The injector is preferably suited for injecting fluid into a combustion chamber of an internal combustion engine.

[0021] An actor 14 is arranged in an inner tube 15 of the injector housing 1. The actor 14 comprises a ground plate 16 and a top plate 18. The injector is arranged intermediate the spring washer 12 and a compensation device 13. The actor 14 acts on the needle 8 and on the spring washer 12 via the ground plate 16. The actor 14 acts on the compensation assembly 30 via the top plate 18. In an alternative embodiment, the compensation assembly 30 may be arranged intermediate the actor 14 and the spring washer 12 and the needle 8. A fluid, which is in this embodiment preferably fuel, may flow from a connection 20 to the nozzle body 4 through a free volume between the inner tube 15 and the injector housing 1.

[0022] In a closed position of the needle 8, the needle 8 and the nozzle body 4 prevent a fluid flow into the combustion chamber of the internal combustion engine. Outside of the closed position of the needle 8, there is a nozzle formed between a tip of the needle 8 and a tip of the nozzle body 4 facing away from the actor 14. Whether the needle 8 is in its closed position or not depends on a force balance between a first force acting on the needle 8 because of the needle spring 10 and a second force acting on the needle 8 because of the actor 14. The actor 14 preferably is a piezoelectric actuator. If the actor 14 gets energized, the actor 14 expands its axial length. If the actor 14 gets de-energized, the axial length decreases.

[0023] If the temperature of the injector increases while the operation of the injector, the injector, especially the injector housing 1, expands its axial length. In general, the injector housing 1, which is preferably made of stainless steel, expands more with the temperature than the actor 14. The compensation device 30 is arranged for compensating the thermal expansion of the injector housing 1.

[0024] The compensation device 30 comprises a first compensation body and a second compensation body. The first and the second compensation body are movable relative to each other in axial direction. In a first embodiment of the compensation device 30 (figure 2) the first compensation body comprises a cup-shaped compensation device body 33 having a recess and a bottom portion. Preferably, the cup-shaped compensation device body 33 is sealed by a first membrane 44. The second compensation body comprises a piston 32 which is arranged movable in axial direction in the recess of the cup-shaped compensation device body 33. The piston 32 comprises a piston head 34 and a piston rod 36. The piston rod 36 protrudes through a recess of the first membrane 44. The piston head 34 separates the recess of the cup-shaped compensation device body 33 in a first fluid chamber 38 and a second fluid chamber 40. Preferably, there is a slight clearance between the piston head 34 and the wall of the recess of the cup-shaped compensation device body 33. The clearance preferably is formed in such a way that a fluid in the first or the second fluid chamber 38, 40 may flow to the second or, respectively, the first fluid chamber 38, 40. Preferably, the fluid flow from the first to the second fluid chamber 38, 40 or vice versa in that way is throttled by the clearance. Additionally there may be a fluid line 42 of the piston 32 for guiding the fluid from the first to the second fluid chamber 38, 40 or vice versa. The first fluid line 42 of the piston 32 may be formed in such a way that a fluid flow through the fluid line 42 of the piston gets throttled. For this reason, the fluid line 42 of the piston may comprise a throttle, a check valve and/or an other valve which is suitable for the compensation device 30.

[0025] During the operation of the compensation device 30, the first and the second fluid chamber 38, 40 are filled with fluid, preferably oil. The fluid in the first and the second fluid chamber 38, 40 is pressurized. Preferably, the fluid is pressurized by a first compensation device spring 46 which is arranged in such a way that the compensation device spring 46 acts on the first membrane 44.

[0026] If the compensation device 30 is arranged in the injector, it is arranged in such a way that the compensation device 30 is preloaded. If the injector housing 1 expands with the changing temperature, the preload on the compensation device is decreasing and the compensation device 30 expands and so the actor 14 never loses contact to the piston rod 36. So, the thermal expansion of the injector housing 1 is compensated by the compensation device 30.

[0027] If the actor 14 gets energized, it may expand in a few microseconds. This duration is too short for the fluid to pass the clearance between the piston head 34 and the recess of the cup-shaped compensation device body 33 and/or the fluid line 42 of the piston 32. So, in that duration the piston 32 stays nearly in its position. Then, the actor 14 has nearly a solid base to act on in such a way that the ground plate 16 of the actor 14 acts on the needle 8 and on the spring washer 12 for moving the needle 8 out of its closed position.

[0028] In a second embodiment of the compensation device 30, additionally or alternatively, the compensation device 30 may comprise a second membrane 72 and a second compensation device spring 74 (figure 3). Then, the compensation device 30 comprises a third fluid chamber 71 which may communicate with the second fluid chamber 40 and which is bordered by a second membrane 72. In an alternative embodiment the compensation device 30 may only comprise the second membrane 72. Then, preferably, there is a sealing between the piston head 34 and the wall of the recess of the second compensation body 33 instead of the clearance and instead of the first membrane 44.

[0029] In the injector a force F acts on the compensation device 30 and the temperature of the injector and, especially, of the compensation device 30 increases to working temperature. If the force F acts on the compensation device 30 while the compensation device 30 has its working temperature for the first time, the first membrane 44 and/or the second membrane 72 of the compensation device 30 get deformed by the first and/or, respectively, the second compensation device spring 46, 74. Then, the first and/or, respectively, the second compensation device spring 46, 74 are pressed against the first membrane 44 and/or, respectively, the second membrane 72. The first and/or, respectively, the second membrane 44, 72 as a whole deform elastically towards the piston 32. Further, the first and/or, respectively, the second compensation device spring 46, 74 are pressed into the material of the first and/or, respectively, the second membrane 44, 72 and in that way the first and/or, respectively, the second membrane 44, 72 are deformed plastically.

[0030] Because of the plastic deformation of the first and/or, respectively, the second membrane 44, 72 the axial length of the compensation device 30 decreases. This decreasing leads to a different behavior of the compensation device 30 relative to the behavior of the compensation device 30 before it gets heated under pressure for the first time. Without a pre-treatment of the compensation device, this different behavior of the compensation device 30 should be taken in to consideration when the injector gets calibrated in order to have a very precise dosing of the fluid by the injector. This is very difficult and not precise.

[0031] A pre-treatment assembly (figure 2) enables to simulate the working conditions of the compensation device 30 in the injector. In that way, the plastic deformation and/or other nonreversible effects concerning the precise function of the compensation device 30 which occur by heating and pressurizing the compensation device 30 are simulated before the compensation device 30 is mounted in the injector and before the injector is calibrated. In that way, the behavior of the injector while its operation is similar to the behavior of the injector when the injector gets calibrated.

[0032] The pre-treatment assembly comprises an assembly body. The assembly body may be formed and arranged as a cup-shaped holder 52. The cup-shaped holder 52 preferably is formed in such a way that there is a proper thermal coupling between the compensation device 30 and the cup-shaped holder 52. This contributes to a homogenous heating of the compensation device 30. Further, the pre-treatment assembly comprises a pressure transferring body which may comprise a cap 54. The cap 54 covers the cup-shaped holder 52. Further, the pre-treatment assembly comprises a heating device which may comprise the first heating device 56. For example, the heating device 56 takes in the cup-shaped holder 52. A guidance of the pre-treatment assembly may comprise a first guidance 58 which is a recess of the first heating device 56 and/or the guidance may be formed by a slight clearance between the cap 54 and the cup-shaped holder 52. A mechanical stop for the pressure transferring body comprises, for example, a step 60 of the first heating device 30. The mechanical stop prevents the pressure transferring body from moving to far towards the compensation device 30 and in this way the mechanical stop contributes to a proper, given stress on the compensation device 30.

[0033] In an alternative embodiment (figure 3) of the pre-treatment assembly the pressure transferring body comprises a piston-shaped pressure transferring element 84. The piston-shaped pressure transferring element 84 comprises a piston rod 86 and a piston head 88. The piston-shaped pressure transferring element 84 is guided by the guidance which is in this embodiment a cylindrical recess 82 of the assembly body. The cylindrical recess 82 takes in the piston rod 86 of the piston-shaped pressure transferring element 84. Further, the cylindrical recess 84 takes in a pre-treatment spring 90. A step 92 of the assembly body forms a first spring rest for the pre-treatment spring 90. The piston head 88 of the piston-shaped pressure transferring element 84 comprises a second spring rest for the pre-treatment spring 90. An actor of the pre-treatment assembly may comprise a pre-treatment spring 90.

[0034] In this embodiment, the heating device comprises a tube-shaped heating device 96 and takes in a heating line 98. The tube-shaped heating device 96 preferably has a clearance fit to the outer diameter of the compensation device 30. The heating line 98 may guide a heated fluid or comprises an electric conductor which gets heated by applying a high voltage on the electric conductor. A positive stop for the compensation device 30 may comprise a ground plate 100 of the pre-treatment assembly. The ground plate 100 of the pre-treatment assembly preferably can be exchanged easily. In that way, it is possible to pre-treat compensation devices 30 with different axial lengths with the same pre-treatment assembly.

[0035] Additionally, there may be arranged a thermal conductor intermediate the compensation device 30 and the heating device which couples the compensation device and the heating device thermally. This is especially advantageous for a proper thermal coupling, if the dimension of the compensation device 30 does not fit to the heating device.

[0036] How to pre-treat the compensation device 30 is explained in the following. In a step S1 (figure 4) a machine which comprises the pre-treatment assembly is started for pre-treating the compensation device 30.

[0037] In a step S2 the compensation device 30 is arranged in the pre-treatment assembly.

[0038] In a step S3 the compensation device 30 gets heated by the heating device.

[0039] In a step S4 a force F is applied on the pressure transferring body towards the compensation device 30 while the compensation device 30 is heated. Preferably, the force F corresponds to that force which is applied on the compensation device 30 during its operation in the injector. The first and/or the second membrane 44, 72 get deformed plastically.

[0040] After that in a step S5, the pre-treatment of the compensation device 30 is finished. The compensation device 30 is ready for being assembled into the injector housing 1 and the injector may be calibrated.

[0041] The invention is not restricted to the explained embodiments. For example, the explained embodiments may be combined. For example, the first embodiment of the pre-treatment assembly may comprise the pre-treatment spring 90. Further, the first heating device 56 may comprise the heating line 98. Further, the ground plate 100 of the pre-treatment assembly may be arranged in the first embodiment of the pre-treatment assembly. Further, the second embodiment of the pre-treatment assembly may comprise the mechanical stop for the pressure transferring body.

Claims

1. Pre-treatment assembly for pretreating a compensation device (30) having a variable length (L),
the pre-treatment assembly comprising

- an assembly body which comprises a guidance and a positive stop,

- a pressure transferring body which is coupled to the guidance movable towards the positive stop,

- an actor which is coupled to the pressure transferring body,

- a heating device,

the pressure transferring body, the heating device, and the positive stop being formed and arranged in such a way that in a given state of the pre-treatment assembly the compensation device (30) is thermally coupled to the heating device while the actor presses the compensation device (30) via the pressure transferring body against the positive stop in such a way that the length (L) of the compensation device (30) decreases.

2. Pre-treatment assembly in accordance with claim 1 with the guidance having a guidance recess which at least partly takes in the pressure transferring body.

3. Pre-treatment assembly in accordance with claim 2 with the guidance recess and the pressure transferring body being formed and arranged in such a way that the pressure transferring body protrudes from both axial ends of the guidance recess.

4. Pre-treatment assembly in accordance with one of the preceding claims with the actor comprising a pre-treatment spring (90) which radially surrounds a part of the pressure transferring body and with the assembly body having a step (92) which forms a first spring rest for the pre-treatment spring (90) and with the pressure transferring body having a second spring rest for the pre-treatment spring (90).

5. Pre-treatment assembly in accordance with claim 4 with the pressure transferring body being piston-shaped and with the pressure transferring body having a piston head (88) and a piston rod (86) and with the pre-treatment spring (90) radially surrounding a part of the piston rod (86) and with the piston head (88) comprising the second spring rest for the pre-treatment spring (90).

6. Pre-treatment assembly in accordance with one of the preceding claims with the heating device comprising a tube-shaped heating body (96) which has at least one heating line.

7. Pre-treatment assembly in accordance with claim 6, with the heating line (98) being surrounded by the material of the tube-shaped heating body (96).

8. Pre-treatment assembly in accordance with claim 6 or 7 with the tube-shaped heating body (96) being formed in such a way that the compensation device (30) arranged in the tube-shaped heating body (96) has a clearance fit to an inner wall of the tube-shaped heating body (96).

9. Pre-treatment assembly in accordance with claim 6 or 7 comprising a thermal conductor which is arranged in such a way that the thermal conductor couples the compensation device (30) with a wall of the recess of the tube-shaped heating body (96).

10. Pre-treatment assembly in accordance with one of the claims 6 to 9 with the heating line comprising an electric conductor.

11. Pre-treatment assembly in accordance with one of the preceding claims comprising a mechanical stop (60) for the pressure transferring body which is formed and arranged in such a way that the movement of the pressure transferring body towards the positive stop is limited by the mechanical stop (60).

12. Method of pre-treating a compensation device for an injector comprising the steps of

- arranging the compensation device (30) in a pre-treatment assembly in accordance with one of the preceding claims,

- applying a force (F) on a first axial end of the compensation device (30),

- heating the compensation device (30) while the force (F) is applied on the first axial end of the compensation device (30).

Drawing