WO1989011035A1

WO1989011035A1 - Plunger pump arrangement

Info

Publication number: WO1989011035A1
Application number: PCT/EP1989/000508
Authority: WO
Inventors: Jacob Heidemans
Original assignee: Hei-Tech B.V.
Priority date: 1988-05-09
Filing date: 1989-05-09
Publication date: 1989-11-16
Also published as: NL8801198A

Abstract

A plunger pump arrangement comprises a plunger (2) guided in a cylinder (1). The cylinder is provided in the vicinity of its closed end with an inlet pipe (12) and a delivery pipe (13) for the pump medium, and is connected at this closed end with a delivery connection (11). The plunger (2) has at least one peripheral groove (5) which, during the compression stroke of the plunger, communicates with an annular channel (3) extending over the inner circumference of the cylinder.

Description

Plunger pump device

The invention relates to a plunger pump device with a plunger which is guided in a cylinder and movable therein, this cylinder being in the vicinity of a closed end with a supply for a medium and a discharge for this medium, both of which extend into the cylinder, and wherein this cylinder is connected at its closed end to a pressure connection and is further provided with at least one annular channel running over the inner circumference of the cylinder.

The invention further relates to a plunger for use in this plunger pump device.

For the sake of simplicity, the medium is referred to below as fuel. Such a plunger pump device, the z. B. can be used to inject fuel under high pressure in a piston internal combustion engine is generally known. Here, the ring channel is a fuel ring channel, which is usually connected to the supply or discharge for the fuel. This known plunger pump device is driven, for. B. by a camshaft, possibly via a rocker arm and / or a tappet mechanism. In the known plunger pumping devices, it is ensured that there is a narrow gap between the cylinder and the plunger, so that the fuel under high pressure cannot easily leak away. Any fuel that may leak through this gap is collected in the fuel ring channel. This fuel ring channel is under a relatively low pressure of less than 10 bar.

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A disadvantage of the known plunger pumping device is that fuel corners occur from the fuel ring channel, for example for driving the pump. This leak through the gap between the plunger and the cylinder has two main causes:

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1. Fuel pressure in the fuel supply and discharge.

The fuel pressure in the fuel supply and discharge leads to a pressure difference across the gap and, as a result, a viscous flow through the gap. At a low pressure .in the

25 This fuel leakage rate is small, but increases as the pressure in the fuel supply and discharge increases. In the case of fuel systems, this pressure must be kept at a certain level in order to prevent the volatile components from evaporating. For diesel fuel z. B.

30 generally a pressure of 1.5 bar. For heavy oil, a higher pressure is necessary because this fuel has a higher temperature, e.g. B. 130 degrees must be brought. In this case, pressures of 5 to 10 bar are used.

35 2. Pumping action in the gap between the plunger and the cylinder.

During the pressure stroke, when the plunger moves upwards, the plunger is under an axial compressive stress due to the back pressure of the medium. As a result, the piston diameter increases as a result of the transverse expansion and the gap between the plunger and the cylinder becomes smaller. At the end of the pressure stroke, the pressure drops and the gap increases again. The gap is then partially filled with fuel. The plunger then moves a little further up and then down again, causing fuel to be carried along in the gap. From the bottom dead center, the plunger then moves back up a little until the pressure stroke begins. At this moment the gap becomes smaller again and the fuel is squeezed out of the gap. The fuel entrained during the downward movement is partly pushed downwards. In this way, therefore, a net transport of fuel takes place and consequently a leakage flow down through the gap. The leak rate increases as the pump pressure increases. In fuel injection systems, there has recently been a development towards higher pressures, which can now be in the order of 600 to 1,800 bar.

It is an object of the invention to implement a plunger pumping device of the type mentioned at the outset, in which the aforementioned leakage losses of the medium are avoided. For this purpose, a plunger pump device according to this invention is characterized in that the plunger is provided with at least one groove running over its outer circumference, which is connected to the annular channel during the pressure stroke. This creates a pressure during the pressure stroke, the possibly leaking medium, for. B. fuel, in the direction of the ring channel. This is clarified further below. An embodiment of the plunger pump device according to the present invention, in which the supply and discharge for the medium is provided with an annular channel for this medium running over the inner circumference of the cylinder and the cylinder also has another ring channel also running over its inner circumference for another medium, which is located between the one ring channel for the one medium and a plunger drive device, the other ring channel being connected to a supply for the other medium, ια is characterized in that at least one groove during the plunger pressure stroke with either one or the other ring channel is connected. For clarification, the other medium or the other ring channel is referred to below as oil or as an oil ring channel.

15

To avoid the fuel corners mentioned under points 1 and 2 above in the direction of the plunger drive, an oil ring channel connected to the oil supply is often attached to the inner circumference of the cylinder, as already stated. The oil ring channel filled with the so-called sealing oil zα is located between the fuel ring channel and the plunger drive. A disadvantage of this known solution is that a special sealing oil system has to be attached and that even at a relatively high sealing oil pressure of 20 to 30 bar there is still a fuel leakage flow from the fuel ring channel to the oil ring channel

25 takes place.

Another method used to avoid fuel leaks is to provide a mechanical seal between the fuel pump and the drive device. The disadvantage of this

3Q- is that the construction is rather complicated and therefore expensive and that the effect is often insufficient in practice.

35 A further embodiment of the plunger pumping device according to the present invention is characterized in that the plunger is provided with an upper and a lower groove, both of which run over the outer circumference of the plunger and, during a piston pressure stroke, in each case the upper or the lower groove with the one or the other ring channel is connected.

The invention is explained in more detail below on the basis of the figures shown in a drawing. Here shows:

Figure 1 shows a plunger guided in a cylinder according to the present invention, the cylinder being drawn in longitudinal section; •

Figure 2 shows the principle of operation of the plunger pump device according to the present invention corresponding to I of Figure 1;

Figure 3 is a longitudinal section of the plunger pump device according to the present invention; and

Figures 4 and 5 show some embodiments of a plunger pump device according to the present invention in longitudinal section.

Figure 1 shows a plunger 2 movable in a cylinder 1. The inner circumference of cylinder 1 is provided with a fuel ring channel 3 and an oil ring channel 4. The plunger 2 has an upper groove 5 and a lower groove 6. At the height of the upper groove 5 there is, for example, diesel oil in the cylinder 1. At the level of the lower groove 6 there is, for example, lubricating oil. The two media may possibly be identical in both ring channels. ^■ 6-

In Figure 2, the function of a plunger pumping device according to Figure 1 according to the invention is explained in detail. Fuel is indicated with a hatching from bottom left to top right and lubricating oil with a hatching running top left to bottom right. The function is described in five steps with the aid of a complete piston movement, the plunger in FIG. 2e returning to the starting position in FIG. 2a.

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Figure 2a shows the situation that occurs shortly before the pressure stroke of the pump is ended. As a result of the pump pressure, the plunger 2 is under axial pressure. As a result, the diameter of the plunger 2 has become larger and the gap 16 between the piston 2 and the cylinder 1 is smaller. In the illustration

15 it is assumed that at this time the separation between fuel and lubricating oil is at the point where the upper groove 5 begins.

When the pressure stroke is completed, the pump pressure drops and the

As a result, gap 16 becomes larger. This situation is shown in Figure 2b. This larger gap is filled with fuel and lubricating oil, the dividing line between the two media is shown in dashed lines. It should be noted here that it is a simplified representation and that in reality it is in a be¬

25 delimited zone around which the separation of fuel and lubricating oil can never occur and that this separation line can also take a shape other than a straight line. This also applies to the other images.

30

Then the plunger 2 moves up again, then down and finally up until the start of the pressure stroke is reached. This state is shown in Figure 2c.

35 After this, the pump pressure increases until the final pressure is reached. As a result, the gap 16 between the plunger 2 and the cylinder 1 becomes smaller. As a result, fuel and lubricating oil are pressed out of the gap 16. The line of separation between fuel and lubricating oil is also shown here in simplified form (Figure 2d).

The plunger 2 then moves upwards until the end of the pressure stroke is reached (Figure 2e). As a result, the starting position of Figure 2a is reached again. A net transport of lubricating oil in the direction of the fuel ring channel 3 has now taken place. This prevents a net transport of fuel in the direction of the oil ring channel 4. This transport does not take place even if the pressure of the fuel is higher than the pressure of the lubricating oil. The transport of both fuel and lubricating oil can be reduced to zero if either the upper groove 5 or the lower groove 6 is omitted. In this case, the fuel pressure is equal to the lubricating oil pressure.

Figure 3 shows a longitudinal section of a high-pressure plunger pump device according to the present invention in the form of a high-pressure fuel pump. The pump comprises a cylinder 1, which is mounted in a pump housing 7. The plunger 2 guided in the cylinder 1 can be moved back and forth by means of the drive device 8. At the top of the plunger 2 there is a high-pressure chamber 9 which is connected to a high-pressure connection 11 via a check valve 10. The fuel is supplied to the pump via supply line 12 and the excess fuel is removed again via the discharge line 13. A fuel ring channel 3 provided in the cylinder 1 is connected to the discharge line 13. This contains fuel which has approximately the same pressure as that which prevails in the fuel discharge line 13. Furthermore, in the embodiment shown, an oil ring channel 4 is attached, through which the oil supply -8th-

drove 14 lubricating oil can be supplied. An upper groove 5 is provided in the plunger 2. This upper groove 5 is wider than the fuel ring channel 3 and remains connected to the latter during the pressure stroke or, if the fuel ring channel 3 is not present, to a line 15. A lower groove 6 is also provided in the plunger 2 . This lower groove 6 is wider than the oil ring channel 4 and remains connected to it during the pressure stroke. Between the upper groove 5 and the lower groove 6 is a cylindrical one

10 part of the plunger 2 is present, which moves back and forth in the cylinder 1 and whose play with the wall of the cylinder 1 varies under the influence of the pump pressure in chamber 9. The effect of this is that lubricating oil is pumped out of the oil ring channel 4 in the direction of the fuel ring channel 3 and the upper groove 5 and that any fuel which has penetrated into this upper groove 5 is pumped back. In order to

15 So a seal is achieved.

If the upper groove 5 is sufficiently deep according to Figure 3, the fuel ring channel 3 can be omitted and one can be satisfied with the bore 15 (see Figure 4a).

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If the lower groove 6 is sufficiently deep as shown in Figure 3, the oil ring channel 4 can be omitted and the bore 14 can be satisfied (see Figure 4a).

25

Instead of oil, fuel can also be supplied via the bore 14 according to ^" Figure 3. Through the lower groove 6, the downward pumping action for the fuel is canceled according to the invention and then only a leakage flow occurs from the lower groove as a result of there prevailing pressure. It is therefore appropriate

30 keep this pressure as low as possible in order to limit the leakage rate.

35 An embodiment is shown in Figure 4b, in which the plunger is only provided with an upper groove 5. According to the present invention, the leak rate is reduced to zero due to the pumping action in the gap. A leakage flow only occurs as a result of a pressure possibly present in the groove 5. This leakage flow can be reduced in that the channel 15 is not connected to the fuel supply or discharge of the pump, but rather to a leakage discharge which is approximately depressurized.

Another embodiment is shown in Figure 4c. Here there is a leakage of fuel from the ring channel 3 to the lower groove 6. According to the present invention, however, the presence of the lower groove 6 reduces the leakage flow from the lower groove 6 to the drive side to zero. In this version, if duct 4 is connected to a low-pressure fuel corner discharge line, the leakage rate of fuel downwards will be small.

Incidentally, other embodiments are also conceivable in accordance with the concept of this invention. Two of these are shown in Figures 4b and 4d.

The effect of the seal is based on the reduction of the game ate between the plunger and the cylinder during the pressure stroke of the pump. It has already been stated that this is caused by the transverse contraction of the material under the influence of the pressure stroke.

This reduction in the amount of play can also, and to an even greater extent, be achieved by one of the following constructions.

Figure 5a: The plunger 2 is made hollow and this cavity 19 is connected to the pressure chamber of the pump; Figure 5b: A second cylinder 16 is fitted around cylinder 1, in which the plunger is guided. The space 20 between these two cylinders 1 and 16 is connected via a line 17 to the pressure chamber of the pump;

Figure 5c: A cylinder 18 is attached around the plunger 2 and the annular space 28 between the core of the plunger 2 and the cylinder 18 is connected via a line 27 to the pressure chamber of the pump.

Claims

P a t e n t a n s r u c h e

^Q 1. Plunger pumping device with a plunger (2) guided in a cylinder (1) and movable therein, in which the cylinder near a closed end with a supply line (12) for a medium and with a discharge line (13) for this medium, both of which extend into the cylinder (1) 5 and the cylinder at this closed end is connected to a pressure connection (11) and also provided with at least one annular channel (3) running over the inner circumference of the cylinder is characterized in that the plunger (2) is provided (5) ^Q with at least one running around its outer circumferential groove, which is (3) in connection with the Kolbendruckhubes during Ringkana ^'l.

2. Plunger pumping device according to claim 1, in which the supply and discharge for the medium is connected to a ring channel (3) running over the inner circumference of the 5 cylinder for this medium, while the cylinder at the same time also runs another ring channel (4 ) for another medium, which is located between the one ring channel (3) for the one medium and a plunger drive (8), 0 the other ring channel (4) being connected to a feed (14) for the other medium , characterized in that at least one groove (5) is connected to either one or the other annular channel during the piston pressure stroke.

5

3. plunger pumping device according to claim 2, characterized ge indicates that the plunger is provided with an upper and a lower groove, both of which extend over the outer circumference of the plunger (2), the upper and the lower groove during a piston pressure stroke with the one or the other ring channel is connected.

4. plunger pumping device according to claim 2 or 3, characterized in that in the operating state, the pressure in the other annular channel (4) is lower than the pressure in an annular channel (3).

5. plunger pumping device according to one of the preceding claims, characterized in that the groove is in each case wider than the annular channel with which this groove is connected.

6. plunger pumping device according to one of the preceding claims, characterized in that the groove (5, 6) is in each case wider than approximately half the plunger stroke.

7. plunger pumping device according to one of the preceding claims, characterized in that the groove (5, 6) is a few micrometers (μ) deep.

8. Plunger pump device according to one of the preceding

Claims, characterized in that a second cylinder (16) surrounds the cylinder (1) to form a cylindrical annular space (20) and this annular space (20) is connected to the pressure chamber (9) via a connecting line (17) - fertilizer stands.

9. plunger with the features of claims 1, 3, 5, 6 or 7 for use in a plunger pumping device according to one of the preceding claims 1 to 8. -A3 -

10. plunger according to claim 9, characterized in that it is designed as a hollow cylinder body, the cavity (19) is connected to its high pressure side.

11. plunger according to claim 9, characterized in that it has a cylindrical annular space (28) in the region between the grooves (5, 6) between a piston core and the piston skirt, which via a line (27) with the pressure side of the piston in Ver ¬ binding.