US3633464A

US3633464A - Controlling system for positioning a swashplate of a multiple-piston rotary fluid pump or motor

Info

Publication number: US3633464A
Application number: US887515A
Authority: US
Inventors: Ryozo Aoyama; Akira Koiwai
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1968-12-28
Filing date: 1969-12-23
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11
Also published as: JPS4940242B1

Abstract

A controlling system for positioning a swashplate of a multiplepiston rotary fluid pump or motor, comprising a servo piston, a changeover valve, an operating lever, and a link mechanism connecting the above three components one after another. When the operating lever is swung, the changeover valve is slid intermediate the link mechanism so as to actuate the servo piston and vary the inclination of the swashplate. By the sliding of the servo piston, the changeover valve is again slid to the neutral position. When the inclination of the swashplate is forced to be varied from the multiple pistons, the changeover valve serves to resist such variation.

Description

United States Patent CONTROLLING SYSTEM FOR POSITIONING A SWASI-IPLATE OF A MULTIPLE-PISTON ROTARY FLUID PUMP 0R MOTOR 7 Claims, 3 Drawing Figs.

US. Cl 91/505, 60/52 VS, 91/384 Int. Cl. F0lb 3/00, FOlb 13/04, F15b 9/10 Field of Search 91/505,

Primary ExaminerCarlton R. Croyle Assistant Examiner.lohn .l. Vrablik Attorney-Steinberg & Blake ABSTRACT: A controlling system for positioning a swashplate of a multiple-piston rotary fluid pump or motor, comprising a servo piston, a changeover valve, an operating lever, and a link mechanism connecting the above three components one after another. When the operating lever is swung, the changeover valve is slid intermediate the link mechanism so as to actuate the servo piston and vary the inclination of the swashplate. By the sliding of the servo piston, the changeover valve is again slid to the neutral position. When the inclination of the swashplate is forced to be varied from the multiple pistons, the changeover valve serves to resist such variation.

CONTROLLING SYSTEM FOR POSITIONING A SWASIIPLATE OF A MULTIPLE-PISTON ROTARY FLUID PUMP R MOTOR This invention relates to improvements in a controlling system for positioning a swashplate of a multiple-piston rotary fluid pump or motor, that is, a variable displacement plunger pump, whereby a displacement thereof is varied.

l-Ieretofore, in case an engine comprising such a pump or motor of the class described of a hydraulically driven car or the like accidentally stops, there is a disadvantage such that a controlling pressure for controlling a servo piston which controls the inclination of a swashplate is not obtained and therefore the swashplate is not restored to its neutral position, ending in that it is impossible to push or pull the car by another car.

The primary object of this invention is to provide a controlling system and a means therefor improved for overcoming the above defect.

Another object of this invention is to provide a controlling system of the class described, in which slight inclination of the swashplate to be derived from variation in load externally subjected to the pump and unbalanced moments by itself are not directly transmitted to other parts as excessive loads.

Still another object of this invention is to provide a controlling system of the class described, in which the servo piston is movable well in response to the theoretical output of the charging circuit.

Briefly stated in accordance with one aspect of this invention, there is provided a controlling system for positioning a swashplate of a multiple-piston rotary fluid pump or motor, comprising a changeover valve adapted to be slid by an operating lever intermediate a link mechanism for actuating a servo piston by acting a pressured fluid medium thereto whereby the inclination of the swashplate is varied and the changeover valve is restored. By virtue of the actuation of the servo piston intermediate the link mechanism, the action of the pressured fluid medium is interrupted.

In accordance with this invention, a multiple-piston rotary fluid pump or motor having a swashplate, comprises, in combination, a servo piston, of which a piston rod is connected with a displaceable link at a pivot on an. end of the displaceable link, and adapted to control the inclination of the swashplate, a changeover valve having a spool, of which the valve rod is connected with the displaceable link at an intermediate point thereof, and adapted to control the servo piston, and an operating lever connected with the displaceable link at another pivot on the other end of the displaceable link for operating the changeover valve, the spool being adapted to be slid in the changeover valve along such a stroke when the firstnamed pivot is a fulcrum, as equal with another stroke along which the spool is adapted to be slid when the another pivot is another fulcrum.

By virtue of this controlling system, any variation in the operating speed of the operating lever does not relate to the sliding speed of the servo piston and other balancing relations in pressure. It is possible to operate the operating lever at an optional speed without any unreasonableness in the link mechanism.

By virtue of this controlling system, when the inclination of the swashplate is slightly varied by the action of the multiple pistons of the pump or motor, the pressured fluid medium is admitted to act on either side of the servo piston so as to resist the sliding motion of the latter and interrupt the transmission of the variation in load, and therefore, a margin in strength of the construction may be left. Thus any external variation in load subjected to the swashplate and-any internal unbalancing moment, which acts on the swashplate so as to slightly vary the inclination thereof, are not directly transmitted to link mechanism. By virtue of this fact, it is possible to provide a neutral returning spring for the swashplate in such a manner that the rotation thereof is not disturbed, and therefore, it is very easy to restore the swashplate to the neutral position.

By virtue of this controlling system, the changeover valve is operated at a speed in proportion to the operating speed of the controlling lever and yet the servo piston is not forcedly slid in accordance with the operation of the operating lever, and therefore, the servo piston is moved in response to a theoretical output of a charging circuit therefor without any influence of a sliding friction and an unbalance due to a back pressure.

The invention will be better understood and other objects and additional advantages of the invention will become apparent upon perusal of the following description taken in connection with the drawings, in which:

FIG. I is a schematic view of a controlling means embodying this invention, in which a swashplate is in its neutral position;

FIG. 2 is an enlarged cross-sectional view of a friction clutch provided in the controlling means; and

FIG. 3 is a schematic view similar to FIG. 1 but showing the swashplate in its inclined position.

Similar numerals refer to similar parts throughout the three views. I

Referring more particularly to the drawings, the preferred embodiment of this invention will now be described; however, the description will be understood to be illustrative of the invention and not as limiting it to the particular construction shown and described. A variable displacement plunger pump 1 l is provided with a swashplate l2 and with a neutral position restoring means 18. That is, the neutral position restoring means 18 is connected with an end 12a of the swashplate by a connecting link 30 for restoring the swashplate 12 into the neutral position. The variable displacement plunger pump 11 is adapted to be driven by an engine and drive a fluid medium when the swashplate I2 is inclined. The inclination of the swashplate I2 is controlled by means of a servo piston 13 as shown in FIGS. 1 and 3. The extent of the inclination of the swashplate is about 2. The servo piston I3 is hydraulically driven by a fluid medium supplied from a fixed displacement pump 50 through a fluid duct 51. The fixed displacement pump 50 is connected with a reservoir 53 through a filter 52. The fluid duct 51 is branched to the reservoir 53 through a check valve 21.

A pin 13 rotatably mounted on the servo piston 13 is adapted to be slidably inserted in a slot 12b formed in the other end of the swashplate 12. A changeover valve 14 having a spool is connected to the fluid duct 51 so as to change over the fluid duct 51 to direct the pressured fluid medium to either side of the servo piston 13.

There is a displaceable link 32, of which a pivot A on an end thereof is pivoted with a piston rod I3a by a link 31. Another pivot C formed at an intermediate part of the displaceable link 32 is connected with an end of a valve rod of the spool of the changeover valve 14 intermediate a link 33. The spool comprises three parts: a pair of parallel flow passages arranged in the left part thereof, a pair of neutral flow passages in the central part thereof, and a pair of crossflow passages in the right part thereof, as shown in FIGS. 1 and 3. The other end of the valve rod of the spool of the changeover valve 14 is connected with a returning spring means 15, which serves for positioning the spool and facilitates the returning motion thereof.

The other end of the displaceable link 32 is provided with still another pivot B, on which the displaceable link 32 is connected with an operating lever 17 by a connecting link 34, a connecting lever 16 and a friction clutch comprisinga lining I9 and an initially coned disc spring 20 mounted on a rotary shaft 22, on which the connecting lever 16 and the operating lever 17 are fixed, as shown in FIG. 2.

In operation, when the swashplate I2 is not inclined for any reason, when the operating lever 17 is swung in the counterclockwise direction in FIG. I from the neutral position, the displaceable link 32 is swung in the clockwise direction in FIG. I on the fulcrum A, because the swashplate I2 is not inclined, so that the servo piston 13 is not slid and the pivot A is not displaced. When the displaceable link 32 is swung in the clockwise direction as above, the link 33 is displaced leftward together with the valve rod of the spool of the changeover valve 14, so that the pressured fluid duct 51 is changed over from the central neutral flow passages to the right crossflow passages of the spool. When the pressured fluid duct 51 is changed over as above, the fluid medium pressured by the fixed displacement pump 50 is admitted into a space on the left side of the servo piston 13 through the crossflow passages so as to slide the servo piston 13 rightward, to incline the swashplate 12 as shown in FIG. 3. Upon inclination of the swashplate 12, the variable displacement plunger pump 11 may serve for translating power to either direction.

The pivot B is displaced to another position B whereby the pivot A is indirectly displaced to another position A. In this case the rightward displacement of the servo piston 13 together with the pivot A causes a rightward displacement of the intermediate pivot C together with the valve rod and the spool of the changeover valve 14, because the pivot 13 in the position B is fixed thereto together with the connecting link 34 by virtue of the friction clutch and serves as a fulcrum on which the displaceable link 32 is swung in the clockwise direction in FIG. 1. When the spool is thus slid rightward into the neutral position, the communication of the pressured fluid medium through the crossflow passages of the spool is interrupted as shown in FIG. 3.

When the operating lever 17 is swung in the clockwise direction in FIG. 1, it will be apparent that the swashplate 12 is inclined in the opposite direction to the above-mentioned motion, and yet the changeover valve 14 is restored to its neutral position. That is, the spool of the changeover valve 14 is at first slid rightward, ending in that the pressured fluid medium is fed into a space on the right side of the servo piston 13 through the parallel flow passages of the spool. Secondary the leftward displacement of the servo piston 13 accompanying the counterclockwise swinging of the displaceable link 32 causes the restoration of the spool into the neutral position thereof.

When the inclination of the swashplate 12 is slightly varied by the action of the variable displacement plunger pump 11,

such a variation is not transmitted to the operating system in the following manner. For example, when a component of a force intends to restore the swashplate l2 inclined as shown in FIG. 3 to the neutral position, the servo piston 13 is rendered to be slid leftward. Because the pivot B in the position B is fixed by virtue of the friction clutch, the displaceable link 32 is swung in the counterclockwise direction in FIG. 3 on the fulcrum B and the spool of the changeover valve 14 is slid leftward. When the spool is displaced from its neutral position to the crossflow passages, the pressured fluid medium is admitted into the space of the left side of the servo piston 13 so as to push it rightward and the inclination of the swashplate 12 is restored. Thus by virtue of the controlling system in accordance with this invention, any fluctuation in position of the swashplate 12 is resisted automatically hydraulically.

It is thus apparent from the above description that the swashplate 12 is operatively connected directly to a single servo piston means 13 so that the position of the single piston 13 will always correspond to a given angular position of the swashplate 12, as is apparent from a comparison of FIGS. 1 and 3, for example. The single elongated control link means 32 is pivotally connected at one end to the single servo piston means and at its opposite end to a manually operable means formed by the

levers

16 and 17 with the rod 22 interconnecting the latter. The friction

clutch assembly

19, 20 forms a retaining means for releasably retaining the manually operable means l6, 17, 22 in the position to which it is manually displaced. Between its ends which are thus respectively pivotally connected directly to the single servo piston means 13 and the manually operable means, the single elongated link means 32 is pivotally connected to the single spool valve means 14 which has the central neutral portion providing communication between the ends of the cylinder of the single servo piston means and the pair of end portions between which the central neutral portion is located, with one of these end portions providing for a flow of fluid to induce movement of the servo piston means in one direction and with the other of the end portions providing for a flow of fluid which will bring about movement of the servo piston means in the opposite direction. These end portions of the spool valve means will always provide for the single servo piston means a direction of movement which will act through the single link means 32 with its connection to the manually operable means as a fulcrum to restore the spool valve means to its neutral position so that in this way any tendency of the swashplate to be moved away from its adjusted position will be opposed with automatic return of the swashplate to its adjusted position, and with this construction the forces which tend to displace the swashplate from its adjusted position will not be transmitted to the linkage components. On the other hand, when the manually operable means is moved by the operator the single elongated link means 32 will swing about its connection to the single servo piston means as a fulcrum, for displacing the single spool valve means in one direction or the other bringing about a corresponding change in the adjusted angle of the swashplate, and with the manually operable means retained in its set position by the retaining means formed by the friction clutch, the movement of the single servo piston means will again operate to restore the single spool valve means to its neutral position, thus providing a predetermined inclination for the swashplate. The means 18 forms a spring means urging the swashplate back toward its neutral position, and it will be noted that this single spring means 18 is connected only to one part of the swashplate, at a portion of the latter opposed to the part of the swashplate which is connected to the single servo piston means. Also the spring means 15 forms a means which acts on the spool valve means to continuously urge the latter to return to its neutral position, so that the operation is enhanced by the spring means 15.

While a preferred embodiment of the invention has been shown and described, modifications thereof will readily occur to those skilled in the art. It should be understood therefore that the invention is not limited to the particular arrangement disclosed but that the appended claims are intended to cover all modifications which do not depart from the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a multiple-piston rotary fluid pump or motor, a tiltable swashplate tiltable about a predetermined axis, a single servo piston means operatively connected with said swashplate for tilting the latter about said axis, said single servo piston means including a single servo piston and a cylinder in which the latter is movable, so that the angular position of the swashplate will always correspond to a given position of the single servo piston in its cylinder, a single spool valve means having'a central neutral portion for providing communication between opposed ends of the cylinder of said single servo piston means and a pair of end portions one of which provides for movement of said single servo piston in one direction in said cylinder and the other of which provides for movement of said single servo piston in the opposite direction in said cylinder, manually operable means for manually setting the angular position of the swashplate, a single elongated link means having opposed ends respectively connected pivotally to said single servo piston and said manually operable means, said single elongated link means being pivotally connected intermediate its ends to said single spool valve means, so that said manually operable means may be operated to swing said single link means about its connection to said single servo piston means for displacing said single spool valve means in a direction which will bring about movement of said servo piston to adjust the angle of the swashplate while restoring said spool valve means to its neutral position where said central portion thereof provides communication between the opposed ends of said cylinder, and retaining means coacting with said manually operable means for releasably retaining the latter in the position to which it is moved by the operator, so that when a force tends to displace said swashplate from its adjusted angle the single servo piston will move to tilt the single link means about its connection to said manually operable means for displacing said spool valve means in a direction which will automatically return the single servo piston to its adjusted position and thus return the swashplate to its adjusted position.

2. The combination of claim 1 and wherein a spring means is operatively connected to said single spool valve means for urging the latter back to its neutral position.

3. The combination of claim 1 and wherein said retaining means is a friction clutch.

4. The combination of claim 1 and wherein three links are respectively pivotally connected directly to said single servo piston, said single spool valve means, and said manually operable means, and are all connected directly to said single elongated link means for providing the pivotal connection between the latter and said single servo piston means, said spool valve means, and said manually operable means 5. The combination of claim 1 and wherein said manually operable means includes a pair of levers and a single rod ex tending between and fixed to said levers, said rod being supported for rotary movement so that said manually operable means is turnable about the axis of said rod, one of said levers being connected with said link means and the other of said levers being available for manual movement.

6. The combination of claim I and wherein a spring means is operatively connected to said swashplate for urging the latter to a neutral position.

7. The combination of claim 6 and wherein said spring means is operatively connected to said swashplate at a part thereof opposed to a part of the swashplate which is directly connected to said single servo piston means.

Claims

1. In a multiple-piston rotary fluid pump or motor, a tiltable swashplate tiltable about a predetermined axis, a single servo piston means operatively connected with said swashplate for tilting the latter about said axis, said single servo piston means including a single servo piston and a cylinder in which the latter is movable, so that the angular position of the swashplate will always correspond to a given position of the single servo piston in its cylinder, a single spool valve means having a central neutral portion for providing communication between opposed ends of the cylinder of said single servo piston means and a pair of end portions one of which provides for movement of said single servo piston in one direction in said cylinder and the other of which provides for movement of said single servo piston in the opposite direction in said cylinder, manually operable means for manually setting the angular position of the swashplate, a single elongated link means having opposed ends respectively connected pivotally to said single servo piston and said manually operable means, said single elongated link means being pivotally connected intermediate its ends to said single spool valve means, so that said manually operable means may be operated to swing said single link means about its connection to said single servo piston means for displacing said single spool valve means in a direction which will bring about movement of said servo piston to adjust the angle of the swashplate while restoring said spool valve means to its neutral position where said central portion thereof provides communication between the opposed ends of said cylinder, and retaining means coacting with said manually operable means for releasably retaining the latter in the position to which it is moved by the operator, so that when a force tends to displace said swashplate from its adjusted angle the single servo piston will move to tilt the single link means about its connection to said manually operable means for displacing said spool valve means in a direction which will automatically return the single servo piston to its adjusted position and thus return the swashplate to its adjusted position.

4. The combination of claim 1 and wherein three links are respectively pivotally connected directly to said single servo piston, said single spool valve means, and said manually operable means, and are all connected directly to said single elongated link means for providing the pivotal connection between the latter and said single servo piston means, said spool valve means, and said manually operable means.

5. The combination of claim 1 and wherein said manually operable means includes a pair of levers and a single rod extending between and fixed to said levers, said rod being supported for rotary movement so that said manually operable means is turnable about the axis of said rod, one of said levers being connected with said link means and the other of said levers being available for manual movement.

6. The combination of claim 1 and wherein a spring means is operatively connected to said swashplate for urging the latter to a neutral position.