TECHNICAL FIELD: The present invention relates to a hydraulic rotating axial piston engine having a housing, enclosing a cylinder barrel journalled in said housing for rotation around a barrel axis and having a number of circumferentially arranged cylinders with a number of pistons reciprocating between two defined end positions, said pistons cooperating with an angled plate in order to obtain said reciprocating move- ment, said axial piston engine having an input/output shaft, said cylinder barrel having channels connecting each cylinder to ports in the cylinder barrel, said ports alternatively acting as inlet and outlet ports, said housing having at least one inlet and outlet channel, each having a kidney shaped port, facing towards said inlet and outlet ports of said cylinder barrel, said kidney shaped ports communicating with a number of said ports at said barrel, at least a number of said cylinder barrel ports extending in both directions outside the cylinders in the two circumferential directions of the cylinder barrel.

PRIOR ART: From EP-A1-0 567 805 a hydraulic piston engine is prior known, which has a number of axial cylinders, which are circumferentially arranged in a rotatable cylinder barrel. Each of said cylinders is provided with a channel, which alternatingly communicates with an inlet port or an outlet port in a housing. From said reference it is apparent that the dimension of said channel in the radial direction of the cylinder barrel is considerably less than the diameter of the cylinder assuming that said channel has a circular

cross sectional shape. The cross sectional area of said channel is considerably less than the cross sectional area of the corresponding cylinder. This involves that maximal flow capacity of the cylinders and the total capacity of the engine will not be fully utilized.

THE PRESENT INVENTION: The object of the present invention is to provide a hydraulic rotating axial piston engine of the above discussed type having maximal flow capacity for a certain volume of the cylinders.

The present object is obtained by means of an engine according to the present invention, which is characterized in that said channels open to said cylinders along the peripheral wall of each cylinder, said opening to said cylinders having substantially the same area as the area of the ports of the barrel and extends completely outside the nearest end position of said piston in each cylinder.

BRIEF DESCRIPTION OF DRAWINGS: The invention will now be described in more detail with reference to preferred embodiments shown in the drawings, in which Fig. 1 shows an axial section of a pump according to the present invention, in a first embodiment, Fig. 2 is a plan view of a connecting part in said first embodiment of the pump as seen separately from the inside, Fig. 3 is an end view of a housing part of the pump according to Fig. 1, Fig. 4 is an end view of the connecting part in a second embodiment of the pump,

Fig. 5 is a cross sectional view of the pump along the lines V-V in fig. 4, Fig. 6 is a plan view of the connecting part in said second embodiment of the pump as seen separately from the inside, Fig. 7 is an axial section of a cylinder barrel of the pump according to the second embodiment, Fig. 8 is an end view of the cylinder barrel as seen from the connecting part, Fig. 9 is an end view of the cylinder barrel as seen from the opposite end, Fig. 10 is a partial section of the cylinder barrel along the lines X-X according to fig. 8.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS: The hydraulic rotating axial piston engine according to the present invention is shown in a first embodiment in Fig. 1- 3 as an axial piston pump 1 having a housing 2 which is comprised by at least two parts, in the shown example three parts, namely a housing part 3 and a connecting part 4, having connecting openings, namely an inlet opening 5 and an outlet opening 6 for connecting input and output conduits for hydraulic fluid to and from the pump respec- tively. A third part 7 of the housing is a support part for the input shaft 8 which is provided to be connected with a drive motor, not shown.

In Fig. 1 the general parts of the pump are shown. The pump is of a so called bent axis type, having a first rotational axis 9, forming a rotational axis for the input shaft 8 and a second rotational axis 10 inclined relative to the first axis by an angle of for example 40°. The second rotational axis is an axis for a cylinder barrel 11 which is rotatably journalled in the housing. The cylinder barrel 11 has a number of axially extending pistons 12, movable axially,

i. e. substantially in parallel with the axis 10 in a reciprocating movement in a corresponding number of cylinders 13, also extending axially with the axis 10, and circumferentially equally spaced along a circle line 14, see Fig. 3. Each cylinder 13 has a fluid passage or channel 15 with a port 16 in the planar end surface 17 of the cylinder barrel 11. Each opening 16 has its largest length along the peripheral circle line 14 and are kidney-shaped.

From Fig. 1 it is further apparent that each piston 12 has a piston rod 18 having spherical heads 19, supported in spherical bearing surfaces, forming recesses 20 in a swash plate 21 which forms an integral part of the input shaft 8.

The spherical recesses 20 are rotatably around a radial plane which is angled relative to the radial plane of the cylinder barrel 11 which results in the reciprocating movement of the pistons 12 and the pumping action according to a prior known principle, in order to create vacuum i. e. suction in the inlet opening 5 and pressure in the outlet opening 6, see for example US patent No. 5,176,066.

Synchronizing means are arranged in order to synchronize the rotational movements of the cylinder barrel with the rotation of the swash plate 21. In the shown example the synchronizing means are made in the form of tooth gear formed by a tooth wheel rim 22 on the cylinder barrel cooperating with a tooth wheel 23 of the input shaft 8. A support pin 24 supports the cylinder barrel 11 along the axis 10 cooperating with a shaft 25 which forms the rotational axis 10 and projects through a bore 26 of the cylinder barrel and supported in a bore 26'of the connec- ting piece 4 of the housing.

Fig. 2 shows the connecting part 4 of the housing separate- ly and from the inside. The connecting part 4 has on its inside a substantially planar, circular surface 27 which in the mounted position is faced to the planar surface 17 of the cylinder barrel 11. The two planar surfaces 17,27 are

arranged to contact each other with a sealing fit. On its inside the connecting part 4 is provided with one inlet port 28 and one outlet port 29, which are kidney-shaped. The inlet port 28 communicates through a channel 5'with the inlet opening 5 and the inner outlet port 29 communica- tes through a separate channel with the outlet opening 5 on the outside of the connecting part 4. The inlet and outlet port 28,29 extend along a peripheral circle line 30 which has a corresponding radius as the circle line 14 of the openings 16 of the cylinder barrel 11. The inlet and outlet opening 28,29 extend on each half of said circle line 30, separated by a main plane 31 extending through the connec- ting part 4. The inlet and outlet port 28,29 are further divided by a second main plane 32 extending 90° relative to the first main plane 31. The inlet and outlet port 28,29 further extend along the circle line 30 along a predetermi- ned peripheral angle which in the shown example is somewhat larger for the inlet opening 5 than for the outlet opening 6 and are arranged so that simultaneously more than one cylinder port 16 communicate with the inlet port 28 and the outlet port 29 respectively. However, the inlet and outlet ports 28,29 can be provided with slit extensions 6', the ends of which determine the total angular extension of the inlet and outlet ports.

In the above first embodiment there has been described a so called single pump, serving a single hydraulic system by means of one single outlet pressure opening 6. Therefore there is one single fluid passage and one single inner port 29. Consequently the cylinder barrel has one single set of cylinders circumferencally positioned along one single periferal circle line 14.

In the second embodiment it is shown a so called double pump, serving two independent hydraulic systems. The second embodiment will now be described with reference to primari-

ly fig. 4-9. From the end view of the connecting part 104 it is apparent that in the double pump there are two outlet pressure openings 106a, 106b. The inlet suction opening 105 is dimensioned to receive sufficient flow of fluid in order to serve the two outlet openings and the correspon- ding hydraulic systems. By means of the section in fig. 5 the extension of the fluid passages 105'and 106'a are shown as an example as well as the inlet port 128 as well as one of the outlet ports 129a. Also the planar surface 127 is shown facing the end surface of the cylinder barrel.

From fig. 6 it is apparent that the inlet port 128 has considerable radial extension contrary to the outlet ports 129a, 129b, which extend substantially concentrically relatively to said second rotational axis 110 which is the axis for the cylinder barrel 111, which is shown in fig. 7- 9.

From figs. 7-9 it is apparent that in the second embodiment there are two sets of axial cylinders 113a, 113b which are circumferentially arranged around the rotational axis 110.

An inner set of cylinders 113a are equally spaced along an inner circle line 114a and an outer set of cylinders 113b are equally spaced along an outer circle line 114b.

Especially when having two circumferentially arranged sets of cylinders 113a, 113b the radial space in the planar end surface 117 facing the planar inner surface 127 of the connecting piece is very limited as the radially inner set of cylinders merely has to communicate with the radially inner pressure port 129a and the radially outer set of cylinders 113b has to communicate with the radially outer pressure port 29b. However, the cylinder ports 116a, 116b are higly extended along their circle lines 114a, 114b respectively. This is especially expressed in the outer set of cylinder ports 116b. It is namely important that the

cross sectional area of the cylinder barrel ports 116a, 116b is as large as possible and not too much smaller than the cross sectional area of the cylinders. It is namely important that the cylinder barrel ports 116a, 116b do not reduce the flow capacity of the pump as a whole.

However, not only the cross sectional area of the cylinder barrel ports 116a, 116b in the cylinder barrel end surface is important for the flow capacity. From the sectional view of fig. 10 the section through one of the radially outer cylinder port channels 115b is shown. In the radially outer cylinder port channels it is especially visible that according to the present invention the channel 115b has an inner opening 150 to the cylinder which extends along the peripheral wall 151 of the cylinder and has substantially the same area as the area of the ports of the barrel.

Furthermore, the cross sectional area of each channel 115b is nowhere less than the area of said opening 150. Further- more, as seen best in fig. 7 said opening 150 has a contour line which is U-shaped. It is apparent from fig. 10 that the opposite walls 152 at the end portions 153,154 converge in direction towards said inner opening 150 of the channel 115b. Said walls 152 pass near said opening 150 over to a wall portion 155 which extends to the planar end surface 117 of the cylinder barrel 111. The transition between wall 152 and the wall portion 155 forms an angle exceeding 90 degrees.

By means of the shape and the arrangement of the cylinder port channels 115b the channels will not form a limitation of the flow capacity of the pump which substantially will be determined by the volume of the cylinders 113a, 113b.

The extension of the cylinder barrel ports 116a, 116b along their peripheral circle lines 114a, 114b and also the corresponding peripheral extension of the suction port 128

and pressure ports 129a, 129b determines the time sequence and operation of the cylinder barrel ports as alternatingly suction ports and pressure ports in syncronization with the angular positions in the end positions, i. e. for upper dead point UPD and lower dead point LDP for the pistons in a principally prior known manner. Further the opening extends along the peripheral wall of the cylinders along at least the outer circle line 114b completely outside the nearest end position of the piston in the cylinder. However, in the example as shown in fig. 8 and 9 the openings extend along the peripheral wall of the cylinders along both circle lines 114a, 114b.

The design of the cylinder barrel channels has been described and shown with reference to the second embodiment with the double pump. However, the same principle is applied to the single pump in order to achieve a maximum of capacity for a certain cylinder volume. The detailed shape of the channel can be modified without changing the principle of the present invention. For example the peripherial extension as described as shown can be excluded for the openings of the cylinders along the inner circle line 116a.