Abstract
The invention relates to a method for producing a net-shape vane for a rotary vane pump, which vane is preferably open-pored and consists of a metal sinter material. The vane has at least one first front face and one second front face which is preferably oriented parallel to the first front face, and a first lateral surface and second lateral surface that is oriented parallel to the first lateral surface. Furthermore, the vane comprises a first contour surface and a second contour surface. The method for producing the vane comprises at least the following steps: pressing (20) a powder mixture to a green body by means of a powder press, sintering (21) the green body inside a sintering furnace to a sintering element having an austenitic structure, quenching the sintering element inside the sintering furnace to a temperature below the martensitic start temperature for hardening (22), tempering (23) the sintering element preferably inside the sintering furnace, removing (24) the sintering element as net-shape vane, preferably as removal from the sintering furnace. After removing the sintering element, deburring (25) can optionally be made. The invention further relates to a vane and a rotary vane pump.
Claims
1. A method for producing a net-shape vane, consisting of a metallic sintered material for a rotary vane pump, wherein said vane has at least a first end face and a second end face, as well as a first side face, and a second side face oriented in parallel thereto, and further, the vane has a first contour surface and a second contour surface, and wherein the method for producing the vane comprises at least the following steps: pressing a powder mixture to form a green body using a powder press wherein said pressing is effected by forming one of the first contour surface and the first end surface by at least one lower force of the powder press and a respective corresponding one of the second contour surface and the second end surface by at least one upper force of the powder press under pressure, with the first side face and the second side face being formed by at least one die of the powder press in which the first side face and the second side face each have surface areas that are larger than surface areas of the first end surface, the second end surface, the first contour surface and the second contour surface; sintering the green body in a sintering furnace to form a sintered part with an austenitic structure; quenching the sintered part within the sintering furnace down to a temperature below a martensite start temperature of the sintered part to harden the sintered part; annealing the sintered part; removing the sintered part as a net-shape vane.
2. The method according to claim 1, wherein said pressing of the vane is effected by forming the first contour surface by at least one lower force of the powder press and the second contour surface by at least one upper force of the powder press under pressure, and the first end face, the second end face, the first side face and the second side face are formed by at least one die of the powder press.
3. The method according to claim 1, wherein said sintering is effected within a temperature range of from 1050 C. to 1300 C.
4. The method according to claim 1, wherein said quenching is performed down to a temperature within a temperature range of from 100 C. to 300 C.
5. The method according to claim 1, wherein said annealing of the sintered part is performed within a temperature range of from 150 C. to 300 C.
6. The method according to claim 1, wherein deburring of the net-shape vane is effected after the sintered part is removed as a net-shape vane.
7. The method according to claim 1, wherein said powder mixture comprises the following components: Cu 0-5.0% by weight, Mo 0.2-4.0% by weight, Ni 0-6.0% by weight, Cr 0-3.0% by weight, Si 0-2.0% by weight, Mn 0-1.0% by weight, C 0.2-3.0% by weight, and Fe as the balance.
8. The method according to claim 7, wherein said powder mixture comprises the following components: Cu 1.0-3.0% by weight, Mo 1.0-2.0% by weight, C 0.4-0.8% by weight, 0-2.0% by weight of one or more elements selected from the set {Ni, Cr, Si, Mn}, and Fe as the balance.
9. The method of claim 1, wherein the second end face is oriented in parallel to said first end face.
10. The method of claim 1, wherein the step of annealing the sintered part is within the sintering furnace and wherein the step of removing the sintered part as a net-shape vane involves removal from the sintering furnace.
11. The method of claim 1, wherein said quenching is performed down to a temperature is performed by direct air blowing.
Description
(1) Further advantageous designs and further embodiments can be seen from the following Figures. However, the details and features seen from the Figures are not limited thereto. Rather, one or more features can be combined with one or more features from the above description to provide new embodiments. In particular, the following statements do not serve as limitations of the respective scope of protection, but illustrate individual features and their possible interaction, wherein:
(2) FIG. 1 shows a representation of a method for producing a vane, consisting of a metallic sintered material, for a rotary vane pump according to the prior art;
(3) FIG. 2 shows a representation of another embodiment of a method for producing a vane, consisting of a metallic sintered material, for a rotary vane pump according to the prior art;
(4) FIG. 3 shows a method for producing a net-shape vane consisting of a metallic sintered material;
(5) FIG. 4 shows another representation of a method for producing a net-shape vane, consisting of a metallic sintered material, for a rotary vane pump;
(6) FIG. 5 shows vanes for a rotary vane pump in a face view;
(7) FIG. 6 shows a representation of a process step of pressing another embodiment of a vane;
(8) FIG. 7 shows another embodiment of a vane for a rotary vane pump, represented in a perspective view;
(9) FIG. 8 shows a representation of a process step of pressing in another embodiment;
(10) FIG. 9 shows a representation of another embodiment of the vane for a rotary vane pump, represented in a perspective side view;
(11) FIG. 10 shows a grinding pattern of the vane for a rotary vane pump;
(12) FIG. 11 shows a rotary vane pump for the illustrative representation of a possible use of the vane for a rotary vane pump.
(13) From FIG. 1, an illustrative representation of a possible method for producing a vane for a rotary vane pump can be seen, as can be performed according to the prior art. For example, vanes for an oil pump of a commercially available 8-speed automatic transmission are produced in this way. According to the method known from the prior art, a blank is punched 1 from a metal sheet in a first step. In the case of a vane for a rotary vane pump, this blank is a cuboid. the punching of the blank is followed by milling 2, which is provided for forming a contour surface on one, two or several side faces of the blank. The milling 2 of the vane for producing the final shape of the vane is followed, in the next step, by hardening 3, which is followed by annealing 4 of the vane. As a result, after the annealing 4 and further an optionally performed cooling, a vane is provided. Because of the tolerance variations caused by the production process, the vane does not yet have the tolerances necessary for using the vane in a rotary vane pump, after the annealing. Instead, according to the shown method, which is usual according to the prior art, it is common to plan the fabrication of the vane in such terms that the dimensions of the vane are larger than those required for the application after the annealing 4 of the vane, to enable afterprocessing for achieving the final tolerances necessary for the use. For the afterprocessing, in the embodiment of the method to be seen in FIG. 1, corresponding to the prior art, after removing 5 the vane from the furnace in which the annealing 4 took place, fine grinding 6 of the vane is performed. In order to remove any existing burrs, afterprocessing of the surface according to the prior art is generally performed, for example, by deburring 7, as in the shown representation of the illustrative embodiment of the method.
(14) Another embodiment of a method for producing a vane can be seen from FIG. 2. The method shown in FIG. 2 is a method for producing a vane according to the prior art consisting of a metallic sintered material as described in WO 2006/123502 A1. FIG. 2 differs from FIG. 1 in that a blank is not punched from a metal sheet, but instead the vane is produced from a metallic sintering material. In a first step, the material is pressed 8, after which the geometry of the vane as desired for the use of the vane already exists. Then, after the pressing 8, the vane is sintered as a so-called pressed body in a sintering furnace by means of a process step of sintering 9. The sintering 9 is followed by removing 10 the vane from the sintering furnace employed for sintering 9 the vane. This is followed by hardening 11 in a furnace provided therefor, and annealing 12 subsequent to said hardening 11. Generally, the dimensions of the vane are too large for application in a rotary vane pump even after production by this method according to the prior art. Therefore, the process steps of fine grinding 13 and deburring 14 are absolutely necessary according to the prior art, which are performed downstream of said annealing 12 and any cooling thereafter.
(15) FIG. 3 shows an embodiment of a method as a method for producing a vane consisting of a metallic sintered material. According to the embodiment of such a method as shown in FIG. 3, pressing 15 of a powder mixture to form a green body is performed in a first step b y means of a powder press. In a second step, the green body is sintered 16 within a sintering furnace to form a sintered part having an austenitic structure. This process step of sintering 16 is immediately followed by hardening 17, which is performed within the sintering furnace. Thus, in a first step, it is required that the sintered part is austenitized for the major part thereof, or preferably completely. Austenitization is performed by heating in a temperature range in which the powder mixture of the sintered part exists in, or is converted to, an austenitic structure. In the heating, it is provided that the sintering 16 and the austenitizing take place within the scope of the same process, at least partially during the sintering 16, i.e., that the sintering of the component to be sintered takes place at a temperature at which an austenitic structure is obtained, or an existing austenitic structure remains stable. After the austenitization, the sintered part is hardened by quenching the sintered part to a temperature below the martensite start temperature of the metallic sintered material. In this step, a sufficiently high quenching speed is brought about to cause a martensitic conversion of the austenitic structure. In a preferred embodiment, quenching can be to a temperature within a temperature range of from 100 C. to 300 C., and such quenching is preferably performed by means of direct air blowing. The hardening 17 is followed by annealing 18, wherein the annealing 18 is also performed within the sintering furnace in the embodiment shown in FIG. 3. The annealing 18 is performed by heating after the quenching, wherein said heating must be at a temperature that does not yet cause a complete or even partial phase transition of the vane. Following the annealing 18, optionally after intermediate cooling, removal 19 of the vane is performed as the last step, the vane being removed as a net-shape vane, i.e., has its designated tolerances immediately after the removal. The possibility of removing the vane as a net-shape vane, as surprisingly found in the presented and described developments, is a relevant innovation over the prior art.
(16) Another embodiment of a method for producing a vane consisting of a metallic sintered material can be seen from FIG. 4. The method shown in FIG. 4 differs from the method shown in FIG. 3, in particular, in that after pressing 20, sintering 21 and hardening 22 and annealing 23, respectively performed in the sintering furnace, with the subsequent removal 24 of the vane, a final deburring 25 is performed as an additional process step.
(17) An embodiment of the vane for a rotary vane pump can be seen from FIG. 5. In the representation shown, the vane 26 is represented in a top plan view onto a first end face 27. At an angle of 90 each to this first end face 27 and parallel to one another, a first side face 30 and a second side face 31 in an orientation parallel thereto are adjacent to the first end face 27. As fourth and fifth lateral surfaces of the body of the vane 26, the vane 26 further has a first contour surface 28 and a second contour surface 29. The first contour surface 28 and the second contour surface 29 are each outwardly warped in the embodiment shown, wherein said warping is caused by a curvature of the edges which the first end face 27 and the second end face, which is not shown, have in common with the first contour surface 28 and the second contour surface 29. The radius of curvature of these edges is the same for the first contour surface 28 and the second contour surface 29, as well as further respectively for the edges in common with the two end faces. For example, by selectively setting the radius of curvature, when the vane 26 is employed in a rotary vane pump, the one among the first contour surface 28 and the second contour surface 29 that is provided for movement in contact to an interior surface of the rotary vane pump can be optimized for such contact. Such an optimization can be performed, for example, in such terms that when the first contour surface 28 or the second contour surface 29 is pressed against the interior surface of the rotary vane pump by the centrifugal force, as tight as possible a closure of the two spaces separated by the vane is possible. For shaping the radius of curvature of the first contour surface 28 and/or the second contour surface 29, different embodiments of the method for producing a vane consisting of a metallic sintered material are possible.
(18) A process step of pressing during the method for producing a vane consisting of a metallic sintered material, for example, according to the process sequence shown in FIG. 4, can be seen from FIG. 6. The process step shown is an example of carrying out the process step shown as pressing 20 in FIG. 4. The vane 32 is inserted into a press in a standing position, so that the first contour surface 33 is formed by a lower force 36 according to the tool concept shown in the arrangement shown, while the second contour surface 34 is formed by an upper force 37. The formation of the first contour surface 33 and of the second contour surface 34 is effected by the pressure exerted by the lower force 36 and the upper force 37. At the same time, the first side surface and the second side surface of the vane are formed by forming the first side face and the second side face as well as, not visible here, also the first end face and the second end face, visible in a top plan view onto the image plane, by the die 35. As a consequence of the orientation of the vane as shown in FIG. 6 and the exertion of pressure by the lower force 36 and the upper force 37 onto the first contour surface 33 and the second contour surface 34, deburring is necessary in many cases. The reason for this is, in particular, the fact that the tool employed, i.e., the lower force 36, the upper force 37 and the die 35, in particular, have a clearance, i.e., a mutual relative movableness of the individual tools. Such a deburring is shown, for example, as deburring 25 in the process sequence shown in FIG. 4.
(19) Another embodiment of a vane 38 can be seen from FIG. 7. The vane 38 has a similar design as the vane shown in FIG. 6 and has in common with the vane shown in FIG. 6 especially the fact that the first contour surface 39 and the second contour surface 40 have edges in common with the first side face 42 and the invisible second side face, and that these contact edges are the longest contact edges of the vane 38. In contrast, the shortest contact edges are the contact edges of the first contour surface 39 with the first end face 41 as well as the invisible end face, and the contact edges of the second contour surface 40 with the first end face 41 and the invisible second end face. In such a ratio of the tolerances of the edges as well as the orientation of the vane to the upper pressing direction, shown by the arrow 43, and the lower pressing direction, shown by the lower arrow 44, deburring, as shown, for example, as deburring 25 in the embodiment of the method according to FIG. 4, is necessary in many cases.
(20) FIG. 8 shows another embodiment of a process step of pressing for producing a vane 45 consisting of a metallic sintered material. In the representation of FIG. 8, the vane 45 is oriented in such a way that the first end face 48 is visible in a top plan view. In the embodiment shown, the first end face 51 is formed by the upper force 50, and the second end face 52 is formed by the lower force 49, during the process step of pressing. In this embodiment of the process step of pressing as a part of the method for producing a net-shape vane consisting of a metallic sintered material, the first contour surface 46 as well as the second contour surface 47 are formed by the die 53. The pressing direction is an axial direction along the longitudinal axis, which is oriented in parallel to the pressing direction formed by the upper force 50 and the lower force 49. The embodiment of the process step of pressing as shown in FIG. 8 serves the purpose, in particular, of an immediate exertion of pressure onto the longitudinal side of the vane 45, wherein the longitudinal side represents the longest side of the vane 45 and is to be understood as edge surfaces between the side faces 48 as well as the invisible side face with the contour surfaces 46, 47 in the embodiment shown. In such a procedure, it is possible to emboss even significantly more complex contours into the first contour surface 46 and/or the second contour surface 47. Another advantage of the embodiment of the process step of pressing is the fact that deburring is not necessary in many cases, so that in many cases a method for producing a net-shape vane consisting of a metallic sintered material is possible without deburring after the removal of the sintered part as a net-shape vane in the embodiment of the process step of pressing as shown in FIG. 8. The process step shown in FIG. 8 is comparable, for example, with the process step of pressing according to the embodiment of the method for producing a vane as shown in FIG. 3.
(21) In another embodiment of the vane 54, the upper pressing direction is shown by an arrow 58, and the lower pressing direction is shown by an arrow 59, in a perspective side view. Here, the upper pressing direction shows the direction in which pressure is exerted to the first end face 56, while the lower pressing direction indicates the direction in which pressure is exerted to the second end face, not shown.
(22) An illustrative grinding pattern of the net-shape vane shown in FIG. 9, i.e., after its removal, in a longitudinal cut can be seen from FIG. 10. The structure is martensitic, wherein the martensitic structure is completely cubic.
(23) An illustrative embodiment of a rotary vane pump can be seen from FIG. 11. The rotary vane pump has a rotor 60, which is arranged within a control ring 61. Within the control ring, a number of seven vanes is arranged in slot-shaped guides, for example, vane 62, which is arranged in a slot-shaped guide in such a way that the first end face 63 is within the paper plane, and the first contour surface 64 of the vane 62 is positioned on an interior wall of the control ring and thus adjacent to an interior wall of the rotary vane pump. Because of the movable support of the vanes in the slot-shaped guides of the rotor, a densification of the space between the first contour surface 64 and the interior wall of the rotary vane pump is effected when the rotor rotates and the resulting centrifugal force acts on the vanes.
