[0001] The present invention relates to a variable displacement pump/motor system, particularly to a pump/motor system in which the displacement can be linear concentrically varied.

BACKGROUND OF THE INVENTION

[0002] Variable displacement pumps/motors operate by converting mechanical power to hydraulic energy, and vice-versa. Several patents have been issued on such concept of variable displacement. For example, variable displacement gear pumps/motors are disclosed in documents US 8,348,635 and US 7,588,431. A gear pump/motor produces flow by carrying fluid in between the teeth of two meshing gears. One gear is driven by the drive shaft and turns the idler gear. The chambers formed between adjacent gear teeth are enclosed by the pump/motor housing and side plates. A partial vacuum is created at the pump/motor inlet as the gear teeth unmesh. Fluid flows in to fill the space and is carried around the outside of the gears. As the teeth mesh again at the outlet end, the fluid is forced out.

[0003] Another example of variable displacement pumps/motors are variable displacement piston pumps/motors, which may be seen in document US 3,270,674. The piston pump/motor is a rotary unit in which part of the pump/motor mechanism rotates about a drive shaft to generate the reciprocating motions, which draw fluid into each cylinder and then expels it, producing flow,

[0004] Still another example of variable displacement pumps/motors are gerotor pumps/motors, disclosed in US 6,244,839. A gerotor pump/motor consists of a pair of gears which are always in sliding contact. The internal gear has one more tooth than the gerotor gear. Both gears rotate in the same direction. Oil is drawn into the chamber where the teeth are separating, and is ejected when the teeth start to mesh again. The seal is provided by the sliding contact.

[0005] Finally, another example of variable displace pumps/motors are variable displacement vane pumps/motors, which may be found in document US 3,847,515. In such pumps/motors, a number of vanes slide in slots in a rotor which rotates in a housing. The housing may be eccentric with the center of the rotor. In some designs, centrifugal force holds the vanes in contact with the housing, white the vanes are forced in and out of the slots by the eccentricity of the housing. In vane pumps/motors, light springs may hold the vanes against the housing or pressurized pins may urge the vanes outward. During rotation, as the space enclosed by vanes, rotor, and housing increases, a vacuum is created, and atmospheric pressure forces oil into this space, which is the inlet sfde of the pump/motor. As the space or volume enclosed reduces, the liquid is forced out through the discharge ports.

[0006] Although the known prior art discloses several types of variable displacement pumps/motors, these pumps/motors fail to address the need for a pump/motor system having no slip between fluid and rotor, and simultaneously being capable of delivering a non-pressurized fluid when there is ho load at the output. The sum of both characteristics results in a variable displacement pump/motor system having a high efficiency.

SUMMARY OF THE INVENTION

[0007] The linear concentric displacement pump/motor system of the present invention fixes two existing problems of the state of the art, as previously mentioned. The first problem to be addressed is the inner slip between the fluid and the rotor, which is not desired if the pump/motor system is intended to be used in power transmission operations. Such inner slip between the fluid and the rotor results in power loss, which increases when operating with higher resistances at the output of the pump/motor system.

[0008] The second problem to be addressed is the existence of a default internal pressure cycle inside the pump. When using a pump to operate a closed circuit transmission system, it is important that the pump only pressurizes the fluid the amount required due to the resistance at the output Pressurizing the fluid when there is no resistance at the output results in power loss, and speed up the deterioration of the fluid by submitting it to unnecessary high-low pressure cycles. It should also be noted that, when it comes to power transmission, the default maximum output pressure in the pump/motor system is directly related to the maximum output torque in the transmission associated thereto, which results in dependence of the efficiency on the maximum output torque of the transmission.

[0009] In order to achieve these objects, solving these problems, according to an aspect of the present invention, a linear concentric variable displacement pump/motor system system is provided, comprising rotors with synchronized movement which are placed parallel and tangent to each other within the pump/motor system housing.

[0010] A main rotor comprises a primary shaft and a cylindrical body bearing vanes in the radial direction. Preferably, the rotor comprises two blades in opposite direction. The system also comprises at least a secondary rotor having a cylindrical body, which body has a longitudinal groove that allows the vanes of the first rotor to pass through the secondary shaft upon synchronized movement of rotation of both rotors.

[0011] Each of the primary and secondary shafts is concentrically placed within a main rotor and secondary rotor cylindrical chambers, respectively, in the pump/motor system housing. The first and second chambers intercepting each other in the longitudinal direction. Two channels are made in the main rotor chamber for each secondary rotor, close to the location both the main rotor chamber and the secondary rotor chamber intercept each other, one at each side of the main rotor chamber, which are used as input and output to the fluid.

[0012] The vanes of the first rotor move tangent to the main rotor chamber wail, and the secondary rotor chambers have a diameter similar to the secondary rotor diameter.

[0013] A piston, having an external diameter similar to the one of the main rotor chamber, has an internal shape matching that of the main rotor and its blades and is placed around the main rotor.

[0014] The secondary rotors are set in a longitudinal sliding system. The synchronized longitudinal movement of these secondary rotors and the piston in the main rotor will then vary the displacement capacity of the pump/motor system.

[0015] These and other features and advantages of the present invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figures 1a to 1e illustrate the main rotor of the pump/motor system of the present invention.

[0017] Figures 2a to 2c illustrate the secondary rotor of the pump/motor system of the present invention.

[0018] Figures 3a to 3c illustrate the main rotor synchronizer of the pump/motor system of the present invention.

[0019] Figures 4a to 4c illustrate the secondary rotor synchronizer of the pump/motor system of the present invention.

[0020] Figures 5a and 5b illustrate the piston of the pump/motor system of the present invention.

[0021] Figures 6a to 6c illustrate the housing of the pump/motor system of the present invention.

[0022] Figure 7a and 7b illustrate a primary rotor guiding rod of the pump/motor system of the present invention.

[0023] Figure 8a to 8c illustrate the secondary rotor guiding rod of the pump/motor system of the present invention.

[0024] Figures 9a and 9b illustrate the actuator system of the pump/motor system of the present invention.

[0025] Figure 10 illustrates the pump/motor system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] As can be seen from Figures 1a to 1e, the variable displacement pump/motor system main rotor 10 comprises a cylindrical body 20 having two longitudinal grooves 30, 30' at opposite directions, passing through the radial direction of the rotor 10. These grooves 30, 30' are responsible for receiving the blades of the rotor (not shown). The wall of the cylindrical body 20 of the rotor has through holes 40, 40' which, together with bolts (not shown), are responsible for fixing the blades to the rotor 10. The cylindrical body 20 of the rotor has two channels 50, 50', perpendicular to the grooves 30, 30' and, consequently, to the blades of the rotor. The channels 50, 50' extend along the entire longitudinal direction of the rotor 10, creating a path to a sliding piston of the rotor to move along. The outer edges of the channels 50, 50' may be slightly slanted to facilitate manufacturing of the matching piston.

[0027] The rotor 10 has a cylindrical hole 60 extending along its center, which is responsible for receiving a piston guide, which will move along the length of the bore 60.

[0028] Figures 3a to 3c illustrate the main rotor synchronizer 200 comprising a striated shaft 210 having a gear 220 attached to one of its ends. The ratio used in such synchronizer 200 is given by the following formula (1):

wherein

R is the ratio of the main rotor related to a secondary rotor;

B is the number of blades in the main rotor; and

G is the number of grooves in each secondary rotor.

[0029] A secondary rotor is illustrated in Figures 2a to 2c. The secondary rotor 100 also has a cylindrical body 110, similar to the body 20 of the rotor 10. The secondary rotor body 110 has a cylindrical channel 120 extending along its length, in the longitudinal direction of the rotor 100, and a cylindrical hole 130 extending along its center. During the synchronized movement of the main rotor and the secondary rotor, the blades of the main rotor pass through the channel 120 and immediately afterwards seal the passage between both rotors. A grooved bush 140 is located inside the secondary rotor central hole 130, thereby transmitting the rotary movement from the synchronizer to the rotor.

[0030] The secondary rotor synchronizer 400, as shown in Figures 4a to 40, comprises a rod 410 having a gear 420 attached to one of its ends. The rod 410 has a keyway 430 along part of its entire length, in the longitudinal direction. The rod 410 is responsible for transmitting the rotary movement to the secondary rotor 100. [0031] A piston 500, also having a cylindrical shape, surrounds the assembly of the main rotor 10, the blades 90 and the main rotor synchronizer 200, housing all these elements. Internally, the piston profile matches that of the main rotor and its blades, as can be seen from the cross-sectional view of Figure 5a. The piston has a central hole 510 configured to receive a cylindrical guiding rod 520 (Figure 5b) which will extend into the center hole 60 of the main rotor 10. Said guiding rod is responsible for sealing the hole walls and allow the piston 500 to longitudinally slide.

[0032] The housing 600 of the pump/motor system, as illustrated in Figures 6a to 6c, comprises two cylindrical inner chambers 610, 620 which are parallel and intersect each other. The pump/motor system housing 600 has at least two channels 630, 630', preferably disposed oppositely, which extend inwardly to the chamber 610 which houses the main rotor 10, at the intersection between the two chambers 610, 620. It should be noted that the position of the channels 630, 630' may vary along the surface of the housing 600. These channels 630, 630' are configured for inputting fluid into the pump/motor system and outputting fluid from the pump/motor system. The front portion of the housing 600 has at least two additional holes; a first guiding rod 700 extends through a first hole 640 inwardly to the main rotor chamber 610 and the main rotor 10 and a second guiding rod 800 extends through a second hole 650 inwardly to the secondary rotor chamber 620 and the secondary rotor 100.

[0033] Exemplarily, as seen in Figures 7a and 7b, a first guiding rod 700 may be cylindrical with two ends 710, 720, one of the ends 710 being internally threaded so as to receive a complimentary threaded pin. The second guiding rod 800, an example of its configuration is shown in Figures 8a to 8c, comprises a rod having two ends 810, 820, a disc 830 being attached to one of its ends 820 which fits one of the ends of the secondary rotor 100. The other of said two ends 810 being internally threaded so as to receive a further complimentary threaded pin. A plurality of cavities 840, 840', 840", 840''' is formed at the edges of said disc 830 so as to allow the fluid to flow while the guiding rod 800 is moved.

[0034] Alternatively, an actuator system 900, as shown in Figures 9a and 9b may be provided, so as to move all the parts of the sliding system synchronously. An actuator system similar to a crank is illustrated but several other types of actuator systems may be used.

[0035] Figure 10 illustrates the pump/motor system completely assembled. As can be noted from the figure, the housing $00 encloses the main rotor 10 with blades 90 and the secondary rotor 100 which are mounted to the main rotor synchronizer 200 and the secondary rotor synchronizer 400, respectively, actuating the same, The main rotor synchronizer 200 and the secondary rotor synchronizer 400 are meshed. The piston 500 then encloses the main rotor 10. The first guiding rod 700 extends through the piston 500 and the main rotor 10 while the second guiding rod 800 extends through the secondary rotor 100. Externally to the housing, the actuator system is depicted, so as to actuate the whole pump/motor system 1000- Upon operation as a pump, torque is applied to the shaft 210, thereby actuating the whole system. If otherwise pressurized fluid is provided at one of the channels 630, 630' {input channel), then the system will act as a motor.

[0036] While this invention has been described by reference to a particular embodiment, it should be understood that numerous changes could be made within the spirit and scope of the Inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiment, but that it have the full scope permitted by the language of the following claims.