EP1068450B1

EP1068450B1 - Adjustable face plate for hydraulic pump or motor

Info

Publication number: EP1068450B1
Application number: EP99913745A
Authority: EP
Inventors: Peter Augustinus Johannes Achten; Zhao Fu; Francis J. Raab
Original assignee: Noax BV
Current assignee: Noax BV
Priority date: 1998-04-07
Filing date: 1999-04-06
Publication date: 2003-09-17
Anticipated expiration: 2019-04-06
Also published as: DE69911386D1; EP1068450A1; DE69911386T2; JP2002510773A; WO1999051881A1

Description

The invention relates to a hydraulic device as described in the preamble of claim 1. Such a device is known, inter alia, from WO 9731165 or from NL 1008256 - which is not a prior publication - of the same applicant, both of which relate to a hydraulic pressure transformer. The disadvantage of the known device is that in the known device energy loss occurs due to high fluid speeds, with the result that the efficiency of the device is low. It has been found that a considerable part of the loss occurs during the closing of the inlet to or outlet from the fluid chamber. In the hydraulic device the inlet to or outlet from the fluid chamber is closed or opened gradually while the volume of the fluid chamber is changing. As a result of this, during the opening or closing of the fluid chamber high flow velocities can occur through the small surface area of the closing or opening aperture between the rotor port and the face plate port. These locally high flow velocities cause considerable losses, and it is important to make the duration of their occurrence as short as possible. In the case of the known device with the round rotor ports and the rounded face plate ports, during, for example, the shutting off of the rotor port with the wall, an ever-decreasing lens-shaped aperture is formed, through which, as a result of the change in the volume of the fluid chamber during opening or closing, liquid flows at ever-increasing velocity. These high flow velocities cause the energy loss.

The object of the invention is to avoid the above disadvantage, and to that end the known device is designed as claimed in the characterizing clause of claim 1. In this way the high flow velocity occurs only during a small rotor rotation, with the result that the losses are limited.

The invention also relates to a hydraulic device designed as claimed in claim 2. By this measure, the edges of the rotor port and the face plate port are formed by the line of intersection of a straight surface and the boundary surface. Such an edge can be simple in design and sharp, so that small cracks are avoided. This ensures that fewer losses occur.

According to a further improvement, the device is designed as claimed in claim 3. By this measure, while the surface area of the aperture to the fluid chamber remains the same, the duration of high flow velocity occurring is shortened further, with the result that fewer losses occur.

According to a further improved embodiment, the hydraulic device is designed as claimed in claim 4. By this measure, a pressure build-up in the fluid chambers is prevented in a simple manner, with the result that the efficiency increases, particularly at high speeds of rotation of the rotor.

The invention is explained below with reference to a number of exemplary embodiments with the aid of a drawing.

In the drawing:

Figure 1 shows a diagrammatic cross section of a hydraulic pressure transformer;

Figure 2a shows the view of the face plate of a pressure transformer from Figure 1 according to the prior art;

Figure 2b shows the view of the rotor of a pressure transformer from Figure 1 according to the prior art;

Figure 3a shows the view of the face plate of a pressure transformer from Figures 1 and 2 according to a first embodiment of the invention;

Figure 3b shows the view of the rotor of a pressure transformer from Figures 1 and 2 according to the first embodiment of the invention;

Figure 4 shows diagrammatically how the face plate ports and the rotor ports from Figures 3a and 3b interact;

Figure 5a shows the view of the face plate of a pressure transformer from Figures 1 and 2 according to a second embodiment of the invention;

Figure 5b shows the view of the rotor of a pressure transformer from Figures 1 and 2 according to the second embodiment of the invention;

Figure 6 shows diagrammatically how the face plate ports and the rotor ports of a third embodiment interact;

Figure 7 shows diagrammatically how the face plate ports and the rotor ports of a fourth embodiment interact; and

Figure 8 shows the efficiency of the hydraulic pressure transformer as a function of the speed of rotation of the rotor;

Figure 9 shows an embodiment corresponding to the first embodiment, in which the wall is narrower than the rotor port;

Figure 10 shows an exemplary embodiment corresponding to the third embodiment, in which the wall is narrower than the rotor port; and

Figure 11 shows an exemplary embodiment corresponding to the fourth embodiment, in which the wall is narrower than the rotor port.

In the various figures corresponding parts are indicated as far as possible by the same reference numerals.

Figures 1 and 2 show a hydraulic pressure transformer 1, the operation of which corresponds to that described in WO 9731185 . The hydraulic pressure transformer 1 has a rotor housing 4 containing bearings 2 in which a rotary shaft 3 can rotate. Attached to the rotary shaft 3 are plungers 5, which can slide in the fluid chambers 7 of a rotor 6. The rotor 6 can rotate freely about its axis of rotation in the rotor housing 4.

A face plate housing 10, in which a face plate 8 can rotate, is fixed on the rotor housing 4. The face plate 8 can be rotated by means of an adjusting shaft 9. The face plate housing 10 is provided with a first line connection 11, a second line connection 12 and a third line connection (not shown). The line connections are connected to the fluid chambers 7 by means of channels, which channels run through the face plate housing 10, the face plate 7 and the rotor 6. The rotor 6 and the face plate 8 are pressed against each other in a sealing manner in a boundary surface 13 by the oil pressure in the fluid chambers 7.

Three face plate ports 14 are provided in the face plate 8 (see Figure 2a), with three walls 15 between them. Each face plate port 14 according to the prior art has an inner radius 17, an outer radius 16 and a circular side edge 18. The rotor 6 is provided with seven rotor ports 19, each of which is in communication with a fluid chamber 7. During the rotation, the fluid chamber 7 goes into communication with a face plate port 14, is sealed off by a wall 15, and subsequently goes into communication with the next face plate port 14. The shutting off of a fluid chamber 7 by means of a wall 15 of a face plate 8 is commonly applied in a corresponding manner in the case of the known hydraulic plunger pumps and plunger motors. In this case there is generally a face plate 8 with two face plate ports 14, and the position of the walls 15 corresponds to the greatest or the smallest volume of the fluid chamber 7, positions in which the speed of changing of the volume of the fluid chamber 7 is minimal. In those situations it is usual to close the fluid chamber 7 gradually, in which case no pressure peaks occur in the fluid chamber 7, because the volume thereof hardly changes.

In the situations in which the stroke volume of the pump or motor or the setting of the hydraulic pressure transformer is changed by the rotation of the face plate, the fluid chamber 7 is shut off when the speed of change of the fluid chamber volume is great. In order to avoid great flow velocities during the shutting off of the fluid chamber 7, said chamber according to the invention must be closed quickly.

In the first embodiment according to the invention, shown in Figures 3a and 3b, to that end the side edges of the face plate 6 and the rotor 8 are adapted. Figure 4 shows how in this embodiment the face plate 6 and the rotor 8 are situated in relation to each other in the position in which a rotor port 19 is just not yet covered fully by the wall 15. A side edge 21 of the rotor port 19 at the left-hand side coincides with a side edge 20 of the face plate port 14. This causes the rotor port 19 to open or close over a common breadth 'b', which is the breadth of that part of the boundary surface 13 which has a rotating rotor port 19, viewed in the radial direction, in common with the face plate ports 14. The wall 15 is a distance 'a' broader than the rotor port 19, so that no short-circuiting can occur between the pressure in the one face plate port 14 and the other. The distance 'a' is more or less constant over the entire breadth, viewed in the directions of rotation of the rotor, so that when the rotor port 19 rotates to the right, the right-hand, adapted side edge 21 over the entire common breadth 'b' will simultaneously pass the left-hand side edge of the rotor port 14, with the result that the aperture is opened simultaneously over the entire common breadth 'b'.

The side edge 20 of the face plate port 14 and the side edge 21 of the rotor port 19 lie in a plane parallel to the axis of rotation of the rotor. This means that the holes on the inside can be worked accurately using simple means, while the boundary surface 13 can also be worked accurately in the known manner. In this way a sharp edge of the ports can be obtained, which increases the accuracy of the simultaneous closing over the entire breadth, thereby making loss reduction possible.

A second embodiment is shown in Figures 5a and 5b. In this case the rotor has twelve fluid chambers 7 and rotor ports 19. The common breadth 'b' has remained the same and, owing to the fact that the rotor ports 19 have become narrower, the common breadth 'b' is greater than the breadth of the rotor port in the direction of rotation. The flow velocity during closure is reduced by this, because the common breadth has remained the same and the volume of the fluid chamber 7 has been reduced because there are now more fluid chambers 7.

Figure 6 shows a third embodiment, in which the shape of the face plate ports 14 has been adapted to the round shape of the rotor ports 19. For a part like the rotor 6, round rotor ports 19 are simple to make (for example, by drilling and/or honing), while the face plate ports 14 are always a special shape which can be made in a special way (for example by spark erosion).

Figure 7 shows a fourth embodiment, in which the rotor port is formed in such a way that the greatest breadth, viewed in the direction of rotation, is situated near the axis of rotation. Here the oil flow to the fluid chamber 7 is directed largely towards the outside diameter of the rotor 6, with the result that cavitation is less likely to occur.

In Figure 8, curve I indicates how the efficiency of the hydraulic pressure transformers designed according to the above mentioned exemplary embodiments depends on the speed of rotation of the rotor. It can be seen here that at low speeds the efficiency is high, but that at high speeds the efficiency falls sharply. It is obvious here that the speed of the volume changes in the fluid chambers 7 when they are shut off by the walls 15 is important. By making the walls narrower, as a result of which a fluid chamber 7 is in communication with two face plate ports 14 through a small rotation angle of the rotor 6, for example through 1 to 3 degrees, it is ensured that no great pressure build-up occurs in the fluid chamber 7. The efficiency of the hydraulic pressure transformer is consequently slightly lower at low speeds, but it remains more or less constant over the entire speed range. This is indicated by curve II in Figure 8. Since the efficiency is now higher at high speed of rotation, the total loss is greatly reduced.

Figure 9 shows the first exemplary embodiment according to figures 3 and 4, in which the wall 15 between the face plate ports 14 has been made narrower. Viewed in the direction of rotation, the face plate port 19 is a distance 'u' greater than the wall 15 over the entire common breadth 'b'. This means that, through the overlapping of the face plate port 19 over the wall 15, a fluid chamber 7 is in communication with at least one aperture 'u' with a face plate port, so that volume changes during rotation of the rotor 6 do not cause a great pressure build-up in the fluid chamber 7, and high, loss-producing flow velocities are consequently avoided.

Figure 10 shows the adapted third exemplary embodiment according to Figure 6 in a corresponding manner, and Figure 11 shows the adapted fourth exemplary embodiment according to Figure 7.

The exemplary embodiments discussed above are based on the known pressure transformer which is designed with plungers 5 and a rotary shaft 3. Likewise in the case of hydraulic devices which are designed differently such as, for example, where the volume of the fluid chambers 7 changes by a movement along a cam disk, the same problems can occur if the fluid chambers 7 are shut off while the volume is changing. The solutions described above can then be used in a comparable manner.

In the exemplary embodiments the fluid chambers are shut off by valves formed by a face plate with ports. Embodiments are also possible in which the valves are designed differently and the control of the valves is by different mechanical means, for example with a cam disk. It is also possible for the valves to be operated electrically. In this situation the invention can also be designed accordingly, in which case the valves must be rapid-acting and the time of opening and closing of the valves is possibly selected in such a way that the fluid chambers are never fully shut off, but are in communication with two line connections over a limited rotation of the rotor.

Claims

A hydraulic device such as a hydraulic pump, a hydraulic motor or a hydraulic pressure transformer (1), comprising a housing (4,10) with line connections (11,12), a rotor (6) which is unlimited in its rotation around an axis of rotation relative to the housing and having fluid chambers (7) placed around the axis of rotation, the volume of which changes between a minimum and a maximum value during rotation, the rotor having rotor ports (19) each of which is in free communication with a fluid chamber (7), the device further comprises switching means (8) activated by the rotation of the rotor for alternately putting one of the line connections (11,12) via a rotor port into communication with a fluid chamber (7), the rotation position in which a line connection (11,12) is put into communication with a fluid chamber being adjustable relative to the rotation position in which the volume of the fluid chamber (7) has a minimum or maximum value, the switching means comprise a face plate (8) having a boundary surface (13) between the rotor and the face plate and face plate ports (14) each of which is in free communication with one line connection (11,12), and which are separated by walls (15), wherein in the boundary surface (13) the rotor ports (19) and the face plate ports (14) in the radial direction relative to the axis of rotation have a common breadth (b), characterised in that the rotor ports (19) and the face plate ports (14) have such leading and trailing edges that in positions in which the communication between a face plate port and a rotor port is established or broken a leading and a trailing edge cover each other substantially over the common breadth (b).
The hydraulic device as claimed in claim 1, wherein viewed in the common breadth (b), the edge (21) of the rotor port (19) or the edge (20) of a face plate port (14) lies substantially in a plane parallel to the axis of rotation of the rotor (6).
The hydraulic device as claimed in claim 1, wherein the common breadth (b) is greater then the average breadth of the rotor port (19) in the tangential direction relative to the axis of rotation.
The hydraulic device as claimed in one of the claims 1-3, wherein the walls (20) are dimensioned in such a way that a rotor port (19) is in communication with two face plate ports (14) through a rotation angle of the rotor (6) between 1 and 3 degrees.