Stroke piston for a stroke piston compressor

Abstract

A stroke piston for a stroke piston compressor for generating compressed air for a vehicle, such as a commercial vehicle, includes a piston body with a piston floor, a piston skirt with piston skirt walls and pin hubs for receiving a piston pin, and at least two piston rings, which can be inserted into circumferential ring grooves of the piston body. Ridges of the piston body are provided between each two ring grooves and between the piston floor and the first ring groove arranged closest to the piston floor and the ring groove arranged closest to the piston skirt facing away from the other ring groove or grooves. At least one of the ridges is recessed at least over a partial section of its ridge height, which is measured parallel to the axis of the piston body, with at least one recess relative to the diameter of the piston body.

Claims

1. A reciprocating piston for a reciprocating piston compressor for generating compressed air for a vehicle, the reciprocating piston comprising: a piston body having a piston head, a piston skirt with piston skirt walls and pin bosses for receiving a gudgeon pin; a first ring groove being disposed closest to the piston head, a third ring groove being disposed closest to the piston skirt, a first piston ring being a compression ring disposed in the first ring groove and a second piston ring being an oil control ring disposed in the third ring groove; and a plurality of lands on the piston body, the plurality of lands including a land between the first ring groove and the third ring groove, a land on a side of the first ring groove distal from the third ring groove, and a land on a side of the third ring groove distal from the first ring groove, at least one of the plurality of lands being set back from a diameter of the piston body in the form of at least one recess at least over a partial section of a land height measured parallel to an axis of the piston body, wherein the at least one recess includes a depth, relative to the axis of the piston body, that varies continuously about the circumference of the recess.

2. The reciprocating piston as claimed in claim 1, wherein a second one of the plurality of lands is configured with a different recess.

3. The reciprocating piston as claimed in claim 2, wherein the recess of the second one of the plurality of lands has a step.

4. The reciprocating piston as claimed in claim 1, wherein the at least one recess includes a groove encircling the piston body.

5. The reciprocating piston as claimed in claim 1, wherein the at least one recess includes a chamfer encircling the piston body.

6. The reciprocating piston as claimed in claim 5, wherein the chamfer is adjacent to one of the first and third ring grooves and faces toward or faces away from one of the first and third ring grooves.

7. The reciprocating piston as claimed in claim 1, wherein the at least one recess encircles the piston body in a rotationally asymmetrical manner with respect to the axis of the piston body.

8. The reciprocating piston as claimed in claim 7, wherein the at least one recess includes an orbital path that is substantially an elliptical shape.

9. The reciprocating piston as claimed in claim 1, wherein at least one of the first and second piston rings is a taper-faced Napier ring.

10. The reciprocating piston as claimed in claim 1, wherein the second piston ring is a coil spring loaded slotted oil control ring.

11. The reciprocating piston as claimed in claim 10, wherein the coil spring loaded slotted oil control rig has at least two outward-projecting lands.

12. The reciprocating piston as claimed in claim 11, wherein the outward-projecting lands of the coil spring loaded slotted oil control ring have land heights that, when measured parallel to the axis of that piston ring, correspond jointly to no more than 20% of the height of that piston ring and correspond individually to more than 10% of the height of that piston ring.

13. The reciprocating piston as claimed in claim 11, wherein the outward-projecting lands of the coil spring loaded slotted oil control ring have land heights that, when measured parallel to the axis of that piston ring, are different.

14. The reciprocating piston as claimed in claim 11, wherein connection angles of the outward-projecting lands of the coil spring loaded slotted oil control ring are in the range of about 0 to 60 degrees.

15. The reciprocating piston as claimed in claim 11, wherein connection angles of the outward-projecting lands of the coil spring loaded slotted oil control ring have different angle sizes.

16. The reciprocating piston as claimed in claim 10, wherein the coil spring loaded slotted oil control ring is one of a coil spring loaded double beveled oil control ring and a coil spring loaded beveled edge oil control ring.

17. The reciprocating piston as claimed in claim 1, wherein the oil control ring has at least one oil drain for the radial passage of oil.

18. The reciprocating piston as claimed in claim 17, wherein the at least one oil drain is one of a hole and a slot.

19. The reciprocating piston as claimed in claim 17, wherein the at least one oil drain is a slot and extends in a circumferential direction of the oil control ring.

20. The reciprocating piston as claimed in claim 17, wherein the at least one oil drain of the oil control ring corresponds at least partially to at least one oil drain of the third ring groove.

21. The reciprocating piston as claimed in claim 1, wherein the third ring groove has at least one oil drain.

22. The reciprocating piston as claimed in claim 1, wherein the third ring groove includes an oil drain that is closed with respect to a hollow interior of the piston body.

23. The reciprocating piston as claimed in claim 1, wherein the third ring groove includes an oil drain that leads into a hollow interior of the piston body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in greater detail below using exemplary embodiments and with reference to the accompanying drawing figures, in which:

(2) FIG. 1 shows a section through a reciprocating piston according to an embodiment of the present invention;

(3) FIG. 2 shows the detail 1b in FIG. 1 on an enlarged scale;

(4) FIG. 3 shows a cross section through a compression ring designed as a taper-faced Napier ring;

(5) FIGS. 4 a) to d) show further illustrative embodiments of details according to FIG. 2;

(6) FIGS. 5 a) to d) and FIGS. 6 a) to d) show different possibilities for recess shapes in lands according to FIG. 1 or 4;

(7) FIG. 7 shows a detail of a land with a recess in section;

(8) FIG. 8 shows a circumferential line of the recess according to FIG. 7 in a plan view of the section line indicated by A, A in FIG. 7;

(9) FIGS. 9 a) to c) show an exemplary oil control ring in various sectional and detail views;

(10) FIG. 10 shows a sectional view of another illustrative embodiment of an oil control ring; and

(11) FIG. 11 and FIG. 12 show two different examples of a ring groove for an oil control ring in section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) FIG. 1 shows a section through a reciprocating piston according to an embodiment of the present invention. The reciprocating piston has a piston head 1a, pin bosses 1c, a piston skirt with loadbearing piston skirt walls 1d and box walls 1e, which connect the piston skirt walls 1d to the pin bosses 1c.

(13) Moreover, the reciprocating piston has a ring zone 1b with three ring grooves, which are described in greater detail below. However, as shown in FIG. 1, some of the lands delimiting the ring grooves can have recesses.

(14) FIG. 2 show the ring zone 1b according to FIG. 1 on an enlarged scale. The ring grooves are numbered as a first ring groove 1, a second ring groove 2 and a third ring groove 3, starting from the piston head 1a. The lands delimiting the three ring grooves are likewise numbered consecutively as a first land 3a1, a second land 3a2, a third land 3a3 and a fourth land 3a4. The first land 3a1 is the fire land. Lands 3a2 to 3a4 show examples of encircling recesses 3b, which are set back or notched radially relative to the outer circumferential surfaces 3c of the reciprocating piston. In the illustrative embodiment shown in FIG. 2, the recesses 3b are each set back in the form of steps.

(15) The first ring groove 1 and the second ring groove 2 are provided for compression rings, which, as shown in section by way of example in FIG. 3, can be designed as taper-faced Napier rings.

(16) The third ring groove 3 is provided for an oil control ring of the kind shown, for example, in FIG. 9 or 10.

(17) FIGS. 4 a) to d) show further possible illustrative embodiments of a ring zone 1b, in which the respective lands 3a2 to 3a3 show different possible cross sectional shapes of recesses 3b. The fire land 3a1 can also have a recess. The lands 3a1 to 3a4 shown in FIGS. 4a) to d) can also be varied independently of one another. Here, the reference signs correspond to those in FIG. 2.

(18) FIGS. 5 a) to d) show further possible cross sections of the recesses 3b, in particular of the land below the compression piston ring grooves (first ring groove 1 and/or second ring groove 2).

(19) FIGS. 6 a) to d) show further possible cross sections of the recesses 3b, in particular for the land below the oil control piston ring groove (third ring groove 3).

(20) In FIG. 5a), the diameter Y of the recess 3b is set back in the form of a step from the diameter X of the piston skirt or piston skirt wall 1d (see FIG. 1), i.e., the diameter X of the piston skirt is greater than the diameter Y of the recess 3b. The configuration in FIG. 5b) is similar to that according to FIG. 5a), but, here, a chamfer at an angle is provided between the diameter X and the diameter Y. According to FIG. 5c), the recess 3b is in the form of a groove, wherein the diameter Y of the groove is less than the diameter X of the piston skirt. FIG. 5d) shows a combination of FIG. 5a) or 5b) and FIG. 5c), in which both the diameter Z of a groove of the recess 3b and a region of the recess situated below the groove and having a diameter Y are less than the diameter X of the piston skirt.

(21) According to FIG. 6a), the diameter A of the recess 3b is set back from the diameter B of the piston skirt or of the piston skirt wall 1d (see FIG. 1) in the form of a step, i.e., the diameter B of the piston skirt is greater than the diameter A of the recess 3b. The configuration in FIG. 6b) is similar to that according to FIG. 6a), but, here, a chamfer at an angle relative to the third ring groove 3 is provided at the diameter B. FIG. 6e) is similar to FIG. 6a), but, here, the depth of the recess 3b is less than in FIG. 6a), FIG. 6d) is a combination of FIG. 6a) or 6c) and FIG. 6b). Here, the diameter B of the piston skirt is once again greater than the diameter A of the recess 3b and, in addition, a chamfer at an angle is arranged between the diameter B of the piston skirts and the diameter A of the recess 3b.

(22) FIG. 7 shows a cross sectional view of any land between ring grooves having a recess 3b with a section line A, A. If this section line A, A is viewed in accordance with FIG. 8, it is clear from this example that the recess 3b can also be formed asymmetrically and/or eccentrically with respect to the axis of the reciprocating piston. That is, the cutting depth of the recess 3b can vary in size, for example, in the course of its orbit. In particular, an oval shape or elliptical shape of the recess orbit is conceivable. Here, the direction of the gudgeon pin is indicated by an arrow K and the direction of connecting rod oscillation is indicated by an arrow P.

(23) FIGS. 9 and 10 show in section, on the one hand, an example of a coil spring loaded double beveled oil control ring (FIG. 9) and, on the other hand, of a coil spring loaded beveled edge oil control ring (FIG. 10) as a possible embodiment of an oil control ring. The examples of an oil control ring each have a main body 5d or 9d with two radially projecting lands 5a, b and 9a, b. Moreover, both illustrative embodiments have a spring element 5e or 9e. Respective holes 5c and 9c are provided between the lands 5a, hand 9a, b as oil drains in both examples. As FIGS. 5b) and 5c) show, these oil drains can be designed as holes 5c1 distributed over the circumference of the oil control ring or, alternatively, as more extended slots 5c2.

(24) The coil spring loaded double beveled oil control ring shown in FIG. 9 can, for example, be of a geometrical design such that the land height 5d1 of land 5a added to the land height 5d2 of land 5b is less than 20% of the ring height 5f of the overall coil spring loaded double beveled oil control dog ring, wherein the respective land heights 5d1 and 5d2 are each only 10% of the ring height 5f. If the ring height 5f=4 mm, for example, it follows that the land height 5d1 of land 5a and the land height 5d2 of land 5b must each be less than 0.4 mm.

(25) The coil spring loaded beveled edge oil control ring shown in FIG. 10 can, for example, be of a geometrical configuration such that the land height 9d1 of land 9a added to the land height 9d2 of land 9b is less than 20% of the ring height 9f of the overall coil spring loaded double beveled oil control ring, wherein the respective land heights 9d1 and 9d2 are each only 10% of the ring height 9f. If the ring height 9f=4 mm, for example, it follows that the land height 9d1 of land 9a and the land height 9d2 of land 9b must each be less than 0.4 mm.

(26) Preferably, lands 5a, b and 9a, b should have an axial height such that the respective land height is no more than 10% of the total height of the oil control ring and the land heights together are no more than 20% of this total height of the oil control ring.

(27) The connection angles can vary, as is likewise indicated, merely by way of example, in FIGS. 9 and 10.

(28) Yet another possible example of a third ring groove 3 for an oil control ring is shown in section in FIGS. 11 and 12. In these figures, the third ring groove 3 can also have at least one, preferably a plurality of, oil drain(s) 11c and 12c, which can pass through the piston skirt wall 1d (in the case of 11c) or be designed as a blind hole (in the case of 12c) and can correspond at least partially to the oil drains 5c (FIG. 9) and 9c (FIG. 10) of the oil control ring.

(29) It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

(30) It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.