JP7119715B2 - fluid pump - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pump that is mounted on a vehicle or the like and that greatly reduces pulsation of discharge pressure when supplying various fluids such as hydraulic oil.

Conventionally, as a fluid pump designed to reduce the pulsation of the discharge pressure, there is one described in, for example, Patent Document 1 below.

The fluid pump described in Patent Document 1 supplies hydraulic fluid to two hydraulic motors that turn propellers for propulsion of ships. Here, two swash plate type piston pumps are coaxially attached to the rotary shaft of the diesel engine, and are configured to discharge working oil in opposite phases.

Hydraulic fluid discharged in opposite phases is sent to each hydraulic motor via separate pressure pipes. A free piston is inserted in this pipeline, and the pulsating pressure generated by the two hydraulic pumps is propagated from one side to the other side. As a result, both pulsation waves cancel each other out, and the hydraulic pulsation is almost eliminated, thereby reducing vibration and noise during operation of the diesel engine.

Further, as another pump designed to reduce the pulsation of the discharge pressure, there is a vane pump described in Patent Document 2, for example.

This vane pump includes a housing, a cam ring, a rotor having a plurality of vanes, and a suction port and a discharge port for supplying and discharging fluid to and from a vane chamber formed between the rotor, vanes, and cam ring. In particular, the maximum inclination angle of the inner peripheral surface of the cam ring is set to 0.9 to 1.7 with respect to the inclination angle of the reference cam curve in the expansion section in the expansion section of the vane chamber.

Here, the "maximum inclination angle" of the cam ring refers to the inclination of the curve when the shape of the cam surface of the cam ring is represented in a graph. For example, when the horizontal axis is the rotation angle of the rotor and the vertical axis is the change in the amount of protrusion of the vane, the curve has a substantially trapezoidal shape. In other words, when the rotor rotates, the vane protruding amount is zero when the vane has entered the rotor most, and the vane protruding amount is maximum when the rotor rotates 180 degrees from that state. Connecting the middle of these two regions results in a substantially trapezoidal graph as a whole. The “maximum tilt angle” refers to the angle at which the graph obtained in this way has the maximum tilt. That is, the larger the maximum inclination angle, the larger the amount of protrusion of the vane with respect to the unit rotational angle of the rotor.

On the other hand, the "reference cam curve" is also obtained by dividing the process of one rotation of the rotor into four sections. However, the graph here is completely trapezoidal. That is, a section corresponding to one pitch of the vane is defined as a region in which the amount of protrusion of the vane is zero, and a region corresponding to a section corresponding to one pitch of the vane is provided at a position separated by 180 degrees from this region in which the amount of protrusion of the vane reaches a maximum. are straight lines connecting the regions of Therefore, the inclination angle in the expansion section of this "reference cam curve" is simply a single constant because the graph in that section is a straight line.

The technique disclosed in Patent Document 2 sets the maximum inclination angle of the cam ring to 0.9 to 1.7 with respect to the inclination angle of the reference cam curve. The reason why the lower limit is set is to prevent an increase in pulsation in the fluid when the lower limit is too small, the expansion section from which the vane protrudes becomes longer and other areas become narrower. On the other hand, the reason for setting the upper limit is that if the upper limit is too large, the maximum vane projection speed in the expansion section will increase, and the expansion speed of the vane chamber will become excessive, preventing smooth inflow of fluid and causing pulsation. This is to prevent it from increasing.

However, since this configuration includes setting the maximum inclination angle of the cam ring to 1.0, which is the same as the inclination angle of the reference cam curve, there is no difference from the earlier prior art. However, in Patent Document 2, the joints between the sections of the reference cam curve are rounded to prevent the vane from becoming excessively accelerated. It is described that the pulsation is reduced as. Although Patent Literature 2 does not describe a specific configuration for "rounding the connecting portion", it can be assumed that the cam surface is shaped in some way.

With such a configuration, the technique of Patent Document 2 aims to reduce the pulsation of the instantaneous discharge flow rate, reduce the flow rate pulsation and pressure pulsation in the discharge pipeline, and reduce the noise generated in the fluid system centering on the fluid pressure pump. and to reduce vibration.

JP-A-2002-48055 JP-A-59-162380

The fluid pump of Patent Document 1 simply sets the drive phases of the two fluid pumps to be opposite to each other. In that case, the overall vibration and noise generated by the two fluid pumps is reduced to some extent. However, the pulsation generated by each fluid pump is not eliminated.

In the technique disclosed in Patent Document 1, a swash plate type piston pump is used as the fluid pump. A single swash plate type piston pump is provided with a plurality of pistons, and hydraulic fluid discharged from these pistons is collected in one pipe and supplied to a hydraulic motor. However, the technique of Patent Literature 1 does not show any improvement proposals for the respective fluid pumps.

When a fluid pump is mounted on a vehicle or the like, it is not always possible to combine a plurality of fluid pumps as in the technique of Patent Document 1 due to the required amount of hydraulic oil to be discharged and mounting space. Rather, it is expected that there will be many situations where installation of a single fluid pump is unavoidable. Therefore, there is a limit to reducing the pulsation of hydraulic pressure generated from the fluid pump.

On the other hand, in the fluid pump of Patent Document 2, regarding the graph showing the amount of protrusion of the vanes, the curve of the boundary between the expansion section and the two sections sandwiching the expansion section is smoothly connected to regulate the projection speed of the vane, and the flow rate of the fluid in the expansion section is controlled. It can be understood that it is a technique for reducing sudden changes in the amount of supply.

However, what is disclosed here is only to note the launch velocity for one vane. For example, the graphs shown in the lower part of FIG. 2, the upper part of FIGS. 5 and 6, etc. in the specification only show the partial instantaneous discharge amount at which the vane projection speed is maximum. Therefore, if a plurality of vane chambers communicate with the discharge port of the vane pump, there is no description of how to eliminate pulsation in the total amount of fluid discharged from each vane chamber.

As described above, the generation of a certain amount of pulsation is unavoidable in any of the above-described conventional techniques, and there is a demand for a fluid pump that suppresses the generation of pulsation.

(characteristic configuration)
The characteristic configuration of the fluid pump according to the present invention is as follows:
three or more volume chambers for sequentially drawing and discharging fluid;
a moving element provided in each of the volume chambers and moving relative to the volume chambers to suck and discharge the fluid into and out of the volume chambers;
A non- rotatable cam that drives the moving element to abut against it by rotation, and has a circular cam area and a non-circular cam that reduces changes in the position of the moving element with respect to a unit rotation to reduce changes in the instantaneous discharge amount of the fluid. a cam having a perfectly circular discharge rate adjusting surface;
a drive unit that drives the cam to relatively rotate the mover and the cam, and discharges the fluid once from each of the volume chambers in one cycle of the relative rotation;
For each of the volume chambers, when the fluid is sucked/discharged, the momentary ejection amount of the fluid is zero after reaching a start phase in which the instantaneous ejection amount of the fluid is zero within one cycle rotation angle Z of the one cycle. The ejection rotation angle α from the maximum central phase to the end phase in which the instantaneous ejection amount is zero again is an integer of 2 to (M−1) where the number of the volume chambers is M. As N
α=(Z/M)×N
and
When any one of the volume chambers is in the end phase, the N-th volume chamber following the volume chamber is in the start phase,
When the phase exactly intermediate between the start phase and the center phase is defined as the first intermediate phase, the increasing tendency of the instantaneous ejection amount from the start phase to the first intermediate phase and the tendency from the first intermediate phase to the center the increasing trend up to the phase reverses across the first intermediate phase;
The tendency of increase from the start phase to the middle phase and the tendency of decrease of the fluid from the middle phase to the end phase are symmetrical with respect to the middle phase.

(effect)
In the case of a fluid pump of the type in which fluid is sucked and discharged by relatively moving a volumetric chamber and a moving element, the flow rate of fluid entering and exiting the volumetric chamber often changes periodically. As a result, the volume chamber vibrates, and the fluid pressure in the fluid pipe changes, causing pulsation.

Therefore, by providing three or more volumetric chambers and sliders as in the present invention, fluctuations in fluid pressure generated in the respective volumetric chambers cancel each other out, and a fluid pump free from pulsation as a whole can be obtained.

In the fluid pump of this configuration, the angle at which the cam rotates for one cycle is defined as one cycle rotation angle Z, and the angle at which the fluid is discharged from the volume chamber within the one cycle rotation angle Z is the discharge rotation angle α. and
It can be expressed as the ejection rotation angle α=(Z/M)×N.
Here, M is an integer greater than or equal to 3 representing the number of volume chambers, and N is an integer from 2 to (M-1).

Z/M is the difference in the rotation angles at which the respective volume chambers perform the discharge operation in one cycle. For example, when the number of volume chambers is 4 and the one-cycle rotation angle Z is 360 degrees, the discharge operation of each volume chamber is performed each time the cam rotates 90 degrees.

On the other hand, N indicates how many volume chambers are in the discharge state at a certain timing. Therefore, as the N value increases, one volume chamber discharges fluid over a longer rotation angle.

It is not possible that N=1, nor is N=M. In the case of N=1, one volume chamber always discharges the fluid, and pulsation is always generated in the discharge operation of one volume chamber as described above. This is because the pulsation cannot be eliminated even if it is made continuous.

On the other hand, N=M means that the fluid is always discharged from all the volume chambers, and it is not possible to secure the period for sucking the fluid in each volume chamber.

Furthermore, the N value is an integer. In other words, since it is impossible for one volume to be half discharged, a small number of N-values means that at one moment, say, three volumes are discharged, and at another instant, two volumes are discharged. Since the chamber is in the discharge state, the discharge state is not constant and the pulsation is not eliminated. Therefore, N is an integer between 2 and (M-1).

After satisfying the above conditions, when any one of the volume chambers is in the end phase, it is necessary that the volume chamber in which discharge is started Nth following this volume chamber is in the start phase. For example, if N=2, at a given moment, a particular volume will be dispensing with other volumes that have started dispensing before it. If an attempt is made to keep the overall discharge rate constant at the start and end of discharge from each volumetric chamber, when a specific volumetric chamber has just started discharging, the other volumetric chambers will be unable to secure a predetermined discharge volume. need to be

Then, the discharge work of a specific volume chamber joins the discharge work of the volume chamber that started discharging immediately before itself midway, and after the discharge work of the previous volume chamber is completed, the discharge work of the one volume chamber is completed. The volume chamber that starts the discharge operation later replaces this, and the decrease in the discharge amount of itself is compensated for by the discharge of the volume chamber one after that. Furthermore, when its own discharge is completed, it will be replaced by a volumetric chamber that starts discharging two times behind itself.

In this way, in order for N volume chambers to always perform the discharge operation, when a specific volume chamber is in the end phase, the next volume chamber is the first volume chamber, and the Nth volume chamber is in the start phase. There is a need.

Furthermore, in order to make the total discharge amount of the volume chambers that perform discharge operations at the same time constant, the first intermediate phase is the phase that is exactly in the middle between the start phase and the center phase for the mode of increase and decrease of the instantaneous discharge amount that each volume chamber has. Then, the increasing tendency of the instantaneous ejection amount from the start phase to the first intermediate phase and the increasing tendency from the first intermediate phase to the center phase are reversed with the first intermediate phase interposed therebetween, and the increase from the start phase to the center phase is reversed. It is sufficient that the tendency of increase and the tendency of decrease of fluid from the middle phase to the end phase are symmetrical with respect to the middle phase. The cam of this configuration is provided with a circular cam region and a non-perfect circular discharge amount adjustment surface that reduces the change in the position of the slider per unit rotation to reduce the change in the instantaneous discharge amount of the fluid. change in the amount of discharge becomes very smooth.

With this configuration , when adding the discharge amount from a plurality of volume chambers in order to obtain the total fluid discharge amount of the fluid pump , the fluid pump is free from discharge pulsation as a whole while increasing the degree of freedom in the number of volume chambers to be installed. can be obtained.

(characteristic configuration)
A fluid pump according to the present invention comprises:
The volume chamber is a cylinder having at least one opening for supplying and discharging the fluid, and
The mover is a piston that reciprocates inside the cylinder,
at least one of the cam and the cylinder are rotatable to repeatedly drive the piston through bottom dead center and top dead center;
the start phase is a phase in which the cam positions the piston at the bottom dead center;
Advantageously, said end phase is the phase in which said cam positions said piston at said top dead center.

(effect)
By using the cylinder and the piston in this way, it becomes easy to determine the driving mode of the piston by the cam. In addition, since the cylinder has an elongated shape, it is easy to arrange a plurality of cylinders around the cam, increasing the degree of freedom in designing the fluid pump.

(characteristic configuration)
A fluid pump according to the present invention comprises:
On the cam surface of the cam, a point corresponding to the bottom dead center that positions the piston at the bottom dead center and a point corresponding to the top dead center that positions the piston at the top dead center are defined as regions of the perfect circular cam. The discharge amount adjusting surface is provided on both sides of the point corresponding to the bottom dead and on both sides of the point corresponding to the top dead,
Since the discharge amount adjusting surfaces on both sides of the point corresponding to the bottom dead end are recessed inward in the radial direction with respect to the circular cam, the instantaneous discharge amount is increased in the region from the start phase to the first intermediate phase. With the rapid increase, the instantaneous ejection amount gradually increases in the region from the first intermediate phase to the central phase,
Since the discharge amount adjusting surfaces on both sides of the top dead corresponding point bulge outward in the radial direction with respect to the perfect circular cam, the second discharge amount adjustment surface is located between the center phase and the end phase. It is possible to configure such that the instantaneous ejection amount rapidly decreases in the area up to the intermediate phase, and the instantaneous ejection amount gradually decreases in the area from the second intermediate phase to the end phase.

(effect)
In this configuration, the area including the point corresponding to the bottom dead end and the area including the point corresponding to the top dead side of the cam surface are provided with discharge amount adjustment surfaces to mitigate changes in the instantaneous amount of fluid discharged near the start phase and near the end phase. ing. As a result, when one cylinder reaches the end phase, the degree of decrease in the instantaneous fluid discharge amount is moderated. In other words, it takes a long time to finish discharging the fluid. On the other hand, when the subsequent cylinder that replaces the one cylinder is in the start phase, the degree of increase in the instantaneous fluid discharge amount is suppressed. As a result, pressure fluctuations of the fluid are reduced and pulsation is eliminated when the discharge work is switched from a specific cylinder to another cylinder.

(characteristic configuration)
In the fluid pump according to the present invention, the cam can be rotatable around a rotation axis, and the cam surface of the cam can be formed on a cylindrical side surface positioned around the rotation axis.

(effect)
The fluid pump of this configuration is, for example, a radial pump. In the case of this configuration, the piston can be operated for one cycle by making one revolution of the cam arranged in the center. The cylinders can be placed around the cam in a predetermined number depending on size. With this configuration, the arrangement of the cylinders is easy, and a fluid pump with a stable discharge flow rate can be obtained mainly by configuring the cam surface to have a predetermined shape.

(delete)

(delete)

(delete)

(characteristic configuration)
A fluid pump according to the present invention comprises:
The mover is a rotor that rotates around a rotation axis and a plurality of vanes provided on the rotor that can extend and retract with respect to the rotor,
the volume chamber is formed by the rotor and the vanes, and a casing enclosing the rotor and the vanes, and is a suction chamber and a discharge chamber distributed around the rotation axis;
The cam is provided on the inner surface of the casing so as to be slidably contactable with the vane,
The casing is provided with a discharge port communicating with the discharge chamber for discharging the fluid,
In the discharge port, the upper side in the rotation direction of the rotor is defined as an upper edge, and the lower side in the rotation direction is defined as a lower edge,
Adjacent two of the vanes are used as a leading vane and a trailing vane,
the starting phase is the phase when the rotor positions the leading vane at the upper edge;
The ending phase may be the phase when the rotor positions the trailing vane at the trailing edge.

(effect)
As in this configuration, a vane pump can also be configured as a pump that suppresses pulsation during fluid discharge. A volume in a vane pump is defined by the space between adjacent vanes. The vanes are smaller in size than the cylinders and pistons described above, and the vanes and rotors can be provided inside one casing. Therefore, the overall size can be made compact with respect to the fluid discharge capacity.

In addition, a relatively large number of vanes can be arranged around the rotor, and there is a high degree of freedom in combining the number M of volume chambers and the number N of volume chambers simultaneously in the discharge state.

Furthermore, in the case of a vane pump, one discharge port is formed so as to face a plurality of volume chambers. Therefore, it is possible to easily obtain the fluid pump of the present invention without significantly changing the shape of the conventional vane pump, such as the need to assemble the fluid discharge passages separately as in the radial pump.

(characteristic configuration)
A fluid pump according to the present invention comprises:
Of the cam, a first position where the preceding vane slides in the start phase and a second position where the trailing vane slides in the end phase are defined as regions of the perfect circular cam. The discharge rate adjusting surface is provided on both sides and both sides of the second position,
The instantaneous ejection amount rapidly increases in the region from the start phase to the first intermediate phase, and the instantaneous ejection amount gradually increases in the region from the first intermediate phase to the center phase,
In a region from the center phase to a second intermediate phase exactly intermediate between the center phase and the end phase, the instantaneous ejection amount sharply decreases, and in a region from the second intermediate phase to the end phase, the instantaneous ejection amount. can be configured to taper off.

(effect)
One cause of pulsation in a vane pump is, for example, unbalanced fluctuations in discharge flow rates of discharge chambers on both sides of one vane. When one vane is located near the center of the discharge port, the discharge amount from the discharge chamber on the downstream side of the vane in the rotation direction is often in the process of decreasing, and the discharge amount from the discharge chamber on the rotation direction upper side is in the process of increasing. often in In other words, the pulsation is reduced if the decrease in the discharge amount associated with one discharge chamber and the increase in the discharge amount associated with the other discharge chamber are balanced.

In addition, when fluid is discharged from a specific discharge chamber and subsequently starts to be discharged from other discharge chambers, fluid pulsation is reduced if the increase and decrease of the instantaneous discharge flow rate change smoothly.

Therefore, in this configuration, by providing a discharge amount adjusting surface near the first position and near the second position as the shape of the cam surface for adjusting the discharge amount, a sudden decrease in the fluid discharge amount is suppressed at the end of the discharge. By suppressing a rapid increase in the amount of fluid to be discharged at the start of discharge, fluctuations in the discharge pressure when the discharge chambers are replaced are reduced. Thereby, a vane pump with little pulsation can be obtained.

Further, by providing such a discharge amount adjusting surface and adjusting the change in the instantaneous discharge amount at the end of discharge and at the start of discharge, the variation of the instantaneous discharge amount from the start phase to the first intermediate phase and the The mode of change of the instantaneous ejection amount from the first intermediate phase to the central phase tends to be reversed with the first intermediate phase as the boundary. This is the same when the instantaneous ejection amount reaches the end phase via the second intermediate phase from the center phase. Moreover, the variation of the instantaneous ejection amount from the start phase to the center phase and the variation of the instantaneous ejection amount from the center phase to the end phase are likely to be reversed at the center phase. As a result, when the instantaneous discharge amounts associated with the plurality of discharge chambers are summed up, the increment and decrement complement each other, making it possible to obtain a fluid pump with little pulsation as a whole.

(characteristic configuration)
In the fluid pump according to the present invention, the cam has a second discharge amount adjusting portion having a small change in inner diameter along the rotational direction in a region sandwiching a position exactly intermediate between the first position and the second position. A surface may be provided such that the instantaneous flow rate is maintained at a maximum value while the leading vane is in sliding contact with the second flow control surface.

(effect)
By widening the phase at which the instantaneous ejection amount is maximized as in this configuration, the phase region in which the instantaneous ejection amount changes during rotation of the rotor becomes narrower, and the time period during which the instantaneous ejection amount remains constant becomes longer. As a result, the pulsation generated by the entire vane pump is further reduced.

(characteristic configuration)
In the fluid pump according to the present invention, an inflection point is provided in the cam at an intermediate position between the first position and the second position, and when the preceding vane passes through the inflection point, The instantaneous discharge amount may be configured to suddenly change from an increasing state to a decreasing state.

(effect)
When an inflection point is provided in the middle of the cam surface as in this configuration, the movement of the vane with respect to the rotor abruptly changes before and after the inflection point, which may cause constant mechanical vibration. However, since the change in the instantaneous ejection amount at the inflection point is large, the change in the instantaneous ejection amount can be reduced in the area up to the inflection point and in the area after passing the inflection point.

As a result, it is possible to easily set the shape of the cam surface, and suppress the occurrence of cavitation in the fluid by suppressing abrupt changes in the discharge pressure in each region. is simplified and costs can be reduced.

Explanatory drawing showing the configuration of the radial pump according to the first embodiment. Explanatory drawing showing the detailed shape of the cam according to the first embodiment Graph showing stroke change of piston according to conventional example Graph showing changes in volume of a cylinder according to a conventional example Graph showing change in instantaneous discharge amount of each plunger according to the conventional example Graph showing changes in the instantaneous total amount of fluid discharged according to the conventional example Graph showing changes in piston stroke according to the first embodiment Graph showing changes in cylinder volume according to the first embodiment Graph showing change in instantaneous discharge amount of each plunger according to the first embodiment Graph showing changes in total instantaneous fluid discharge amount according to the first embodiment Explanatory drawing showing the structure of the radial pump according to the second embodiment. Explanatory drawing showing the configuration of each part of the radial pump according to the second embodiment. Explanatory drawing showing the configuration of the vane pump of the third embodiment Explanatory drawing showing the operation mode of the vane pump of the third embodiment Explanatory drawing showing the operation mode of the vane pump of the third embodiment Graph showing changes in vane-to-vane volume of the vane pump of the third embodiment Graph showing change in instantaneous discharge suction amount of the vane pump of the third embodiment Graph showing changes in instantaneous discharge amount of the vane pump of the third embodiment Explanatory drawing showing the configuration of the vane pump of the fourth embodiment. Explanatory drawing showing the configuration of the vane pump of the fifth embodiment. Graph showing changes in instantaneous discharge amount of the vane pump of the fifth embodiment Explanatory drawing showing the configuration of the vane pump of the sixth embodiment. Graph showing changes in instantaneous discharge amount of the vane pump of the sixth embodiment Explanatory drawing showing an operation mode of a conventional vane pump Graph showing changes in vane-to-vane volume of a conventional vane pump Graph showing changes in instantaneous discharge suction volume of a conventional vane pump Graph showing changes in instantaneous discharge volume of a conventional vane pump Graph showing changes in instantaneous discharge volume in a fluid pump with three volumetric chambers Graph showing changes in instantaneous discharge volume in a fluid pump with 4 volumetric chambers Graph showing changes in instantaneous discharge volume in a fluid pump with 5 volumetric chambers

(overall overview)
The fluid pump S according to the present invention is intended to prevent pulsation of the fluid W due to fluctuations in the discharge pressure and vibration of the fluid pump S or connecting pipes when the fluid W is discharged. The configuration of the fluid pump S includes three or more volume chambers B for sucking and discharging the fluid W in sequence, and three or more volume chambers B provided in each of the volume chambers B and moving relative to the volume chambers B to pump the fluid W into the volume chambers B. and a moving element D for inhaling and discharging.

The mover D and the cam C in contact therewith rotate relative to each other, and at least one of the mover D and the cam C is driven by the driving portion G. As the mover D and the cam C perform one cycle of relative rotation, the fluid W is discharged from each of the volume chambers B once.

In order to suppress the pulsation in the fluid pump S having a plurality of volume chambers B in this way, it is necessary to harmonize the characteristics of fluid discharge in a specific volume chamber B and the characteristics of fluid discharge in other volume chambers B. There is For this reason, the fluid pump S of the present invention is constructed so that the changes in the instantaneous discharge amounts of the fluid W in the respective volume chambers B are strictly defined so that the increases and decreases in the instantaneous discharge amounts in the respective volume chambers B complement each other well. I have

Below, an embodiment using a plunger P having a piston 1 and a cylinder 2 and an embodiment using a rotor r having vanes V will be described as the fluid pump S according to the present invention. Characteristic configurations will be described.

[First embodiment]
A first embodiment of a fluid pump S according to the present invention will be described with reference to FIGS. 1 to 10. FIG. This fluid pump S is a so-called radial pump S1 having a plurality of plungers P each having a cylinder 2 as a volume chamber B and a piston 1 as a mover D. As shown in FIG. As shown in FIGS. 1 and 2, for example, one cam C is arranged at the central position, which can move the piston 1 of the plunger P by one cycle for one revolution. Around the rotation axis X of the cam C, for example, a first plunger P1 to a fourth plunger P4 are arranged with a rotation angle of 90 degrees. The cam C drives the respective plungers P in turn, causing the piston 1 to reciprocate. As a result, the fluid W such as working oil is supplied to and discharged from the inside of the cylinder 2, and the fluid W is transported to a predetermined location.

A radial pump S1 using a plunger P has been widely used in the past. At least one flow path R is connected to the cylinder 2 . When there is only one flow path R, the flow path R is branched into two directions, each of which is provided with, for example, a check valve 4 . As a result, when the piston 1 is pushed out by the spring member 3, only one check valve 4 opens and the fluid W flows into the cylinder 2 from the suction port 5a. Subsequently, when the piston 1 is pushed by the cam C, only the other check valve 4 opens and the fluid W is discharged from the discharge port 5b. Thus, a radial pump S1 having a simple structure is formed.

However, in the radial pump S1 using only one plunger P, the supply and discharge of the fluid W are alternately performed. Therefore, in this embodiment, the pulsation is eliminated by combining a plurality of plungers P and devising the shape of the cam C. FIG.

(Cylinder)
As shown in FIG. 1, in this embodiment, four plungers P, ie, a first plunger P1 to a fourth plunger P4 are provided. Each plunger P1-P4 has a cylinder 2 and a piston 1; These plungers P are arranged at intervals of 90 degrees around the rotation axis X of the cam C, and are provided with a phase difference of 1/4 cycle with respect to the cycle of one rotation of the cam C. As shown in FIG. Each cylinder 2 is formed with, for example, a suction port 5a and a discharge port 5b for the fluid W separately. As a result, the fluid W can be sucked and discharged smoothly.

(piston)
A piston 1 that reciprocates along the inner surface is inserted in each cylinder 2 . A spring member 3 is provided over a portion of the piston 1 and a portion of the cylinder 2, and the piston 1 is always urged toward the cam C, so that the outer end surface 1a of the piston 1 and the cam C contact each other. contact is maintained.

(Flow path)
A supply channel R<b>1 as a channel R for supplying the fluid W to the inside of the cylinder 2 is connected to the suction port 5 a of each cylinder 2 . One discharge port 5b is connected to a discharge path R2 as a flow path R for conveying the fluid W to another fluid supply destination. The four supply paths R1 connected to each cylinder 2 may be branched from, for example, one large-diameter pipe. Also, the four discharge passages R2 may be combined into one pipe with a large diameter.

As shown in FIG. 1, a check valve 4, for example, is provided in each of the supply path R1 and the discharge path R2. As a result, the flow direction of the fluid W is restricted to one direction from the supply path R1 to the discharge path R2. The check valve 4 may have any structure as long as it has the function of a one-way valve.

(cam)
As shown in FIG. 1, the cam C of this embodiment has a nearly circular cross section and rotates around an eccentric rotation axis X. As shown in FIG. Rotational drive from the driving portion G is transmitted to the cam C, although illustration is omitted. The piston 1 abuts against the cam C in a direction perpendicular to the axis X of rotation. With this configuration, the arrangement of each plunger P is easy, and a radial pump S1 with a stable discharge flow rate can be obtained mainly by configuring the cam surface C1 of the cam C into a predetermined shape.

Before explaining the cam C of this configuration, an example in which the cross section of the cam C is a perfect circle as indicated by the dotted line in FIG. 2 will be explained. Characteristics of the radial pump S1 using this cam C are shown in FIGS. 3 to 6. FIG.

3, the horizontal axis represents the rotation angle of the cam C, and the vertical axis represents the stroke of the piston 1. In FIG. The piston stroke is set to zero when the piston 1 is at the bottom dead center, and the stroke increases toward the top dead center. When the cam C makes one revolution and the piston 1 makes one reciprocation, the stroke of the piston 1 associated with each of the plungers P1 to P4 is sequentially delayed by 1/4 cycle. The movement curve of the piston 1 becomes a sine curve.

FIG. 4 is a curve showing changes in the volume of the cylinder 2. As shown in FIG. The cylinder volume is the volume change amount when the piston 1 reciprocates. A cylinder volume of zero means that the piston 1 is at the top dead center. As the piston 1 moves from this position toward the bottom dead center, the cylinder volume increases. The value on the vertical axis can be calculated, for example, by multiplying the cross-sectional area of the cylinder 2 by the stroke distance of the piston 1 . This curve is also a sine curve.

5 shows the instantaneous flow rate of fluid W drawn into or expelled from plunger P. FIG. That is, it is synonymous with the curve in FIG. 4 differentiated by the rotation angle of the cam C.

FIG. 6 shows only the instantaneous discharge amount of the fluid W discharged, omitting the portion where the fluid W is sucked into the four cylinders 2 in the curve shown in FIG. Furthermore, the thick line that changes into a waveform in the figure indicates the total instantaneous ejection amount obtained by adding these four curves. A vertical change in the total amount of instantaneous ejection indicates the presence of pulsation.

When the cross-sectional shape of the cam C is a perfect circle, the curve indicating the instantaneous total discharge amount is formed by simply connecting approximately circular arc-shaped curves, as shown in FIG. In this case, the curve bends at an acute angle, especially at the moment when the discharge rate decreases and then increases again. Here, the instantaneous total amount of ejection changes abruptly and a constant pulsation occurs.

To reduce this pulsation, for example, the number of plungers P should be increased. By doing so, the fluctuation range of the fluid W ejected by each plunger P is moderated, and the cycle of pulsation is shortened. However, simply increasing the number of plungers P cannot completely eliminate the pulsation. Therefore, in the present embodiment, the cross-sectional shape of the cam C, which is a perfect circle, is modified as described below.

FIG. 10 shows the instantaneous ejection amount and the instantaneous ejection total amount of each plunger P when the cam C of this embodiment shown in FIG. 1 is used. In order to keep the total instantaneous discharge amount constant as in this example, the curve of the instantaneous discharge amount of each plunger P must be appropriately set. Specifically, the degree of change in the instantaneous flow rate is reduced when the instantaneous discharge amount becomes zero and when it reaches its maximum. As shown in FIG. 10, for example, when the instantaneous discharge amount of each plunger P is represented, each curve has a shape in contact with the horizontal axis indicating zero instantaneous discharge amount and the horizontal axis indicating the total instantaneous discharge amount.

In order to obtain such a curve of the instantaneous discharge amount, for example, as emphasized by the wavy line in FIG. A discharge amount adjusting surface C2 is formed in a region including a corresponding point Cd for positioning the piston 1 at the bottom dead center, which reduces the positional change of the piston 1 per unit movement of the cam C. As shown in FIG. More specifically, the basic configuration is a perfect circular cam C0 (indicated by a dotted line) including a top dead corresponding point Cu and a bottom dead corresponding point Cd in the radial direction. bulging outward in the radial direction. It is assumed that this bulge does not reach an intermediate position Cm in the middle between the point Cu corresponding to the top dead end and the point corresponding to the bottom dead end Cd on the outer peripheral surface of the cam C. On the other hand, both sides of the point Cd corresponding to the bottom dead end are recessed radially inward with respect to the circular cam C0. This recess also does not reach the intermediate position Cm on the outer peripheral surface of the cam C. As shown in FIG.

By configuring the shape of the cam C in this way, the amount of change in volume of the piston 1 (plunger The instantaneous discharge amount of P) becomes maximum at a position between the point corresponding to the bottom dead end Cd and the point corresponding to the top dead end Cu. For example, the middle position Cm is the position. Assuming that the intermediate position Cm of the cam C is the maximum instantaneous discharge amount position, as shown in FIG. The area up to point c, which is the position, is divided into two front and rear areas. The first half is the area from point a to point b, where the instantaneous discharge rate gradually increases and then sharply increases to the maximum slope of the curve. This is a region up to point c where the amount of increase gradually decreases and the instantaneous ejection amount reaches a maximum. This point c is just midway between the point Cd corresponding to the bottom dead and the point Cu corresponding to the top dead on the cam C.

On the other hand, the area from point c, which is the position of the maximum instantaneous discharge amount, to point e, which is the point corresponding to the top dead end Cu, is also divided into two front and rear areas. That is, the first half is the area from point c to point d where the instantaneous discharge amount gradually decreases and then sharply decreases and the slope of the curve reaches the maximum. This is the area up to the point e where the minute is reduced and the instantaneous ejection amount becomes zero. The change in the instantaneous discharge amount from point a to point e also occurs when the piston 1 sucks the fluid W entering the cylinder 2 .

By providing the cam surface C1 with the discharge amount adjusting surface C2 in this manner, the set of the first plunger P1 and the third plunger P3 and the set of the second plunger P2 and the fourth plunger P4 can obtain The change in the discharge amount of the fluid W to be applied becomes very smooth. Therefore, when adding the discharge amount of each set of plungers P to obtain the total fluid discharge amount of the fluid pump S, the change in the total discharge amount becomes smooth, and the pulsation is greatly reduced.

As shown in FIG. 9, when setting the area from point a to point c on the solid line for the first plunger P1, a predetermined discharge amount of the fluid W must be maintained. In other words, the volume of the fluid W in this region is obtained by multiplying the cross-sectional area of the cylinder 2 by the stroke of the piston 1, so as long as the cam stroke is the same, the discharge amount is the same. Therefore, the area of the hatched area in FIG. 5 and the area of the hatched area in FIG. 9 are set equal. Since the curve shape in FIG. 5 is different from the curve shape in FIG. 9, the height at the maximum instantaneous discharge amount position (point c in FIG. 9) is slightly higher in FIG.

As a result of forming the cam C in consideration of these points, two curves of the instantaneous discharge amount are obtained as shown in FIG. One of them is a composite curve by the first plunger P1 and the third plunger P3 which are opposite in phase to each other, and the other is a composite curve by the second plunger P2 and the fourth plunger P4 which are in opposite phase to each other. curve. With such a curve shape, the total instantaneous discharge amount obtained by adding the flow rates of both combined curves becomes substantially constant.

However, in order to keep the total instantaneous discharge amount, which is the sum of the flow rates of both synthetic curves, constant, it is necessary to further limit the shape of both synthetic curves. That is, as shown in FIG. 9, when the cam C rotates from the point a corresponding to the bottom dead center Cd to the point c which is the maximum position of the instantaneous discharge amount, the increase mode of the instantaneous discharge amount is the point a and the point c. is reversed across point b, which is the center position of . Points b and d are points of inflection, and a curve from point a to point b and a curve from point b to point c are symmetrical with respect to point b. Also, a curve from point c to point d and a curve from point d to point e, which is the top dead center corresponding point Cu, are configured point-symmetrically with respect to point d.

In addition to this, the increase mode of the instantaneous discharge amount when the cam C rotates from point a to point c in FIG. be symmetrical across the That is, the curve from the point a to the point c is configured to have a symmetrical shape with the curve from the point c to the point e across the point c. By configuring in this way, the total instantaneous discharge amount obtained by totaling the instantaneous discharge amounts of the first plunger P1 to the fourth plunger P4 becomes substantially constant as shown in FIG. 10, and the pulsation is eliminated. The height of the horizontal line indicating the instantaneous total amount of ejection in FIG. 10 is the average height position of the instantaneous total amount of ejection of the waveform in FIG.

The fluid pump S having such a structure includes a first set of a first plunger P1 and a third plunger P3 arranged in opposite directions with one cam C interposed therebetween, A combination of a second set of a second plunger P2 and a fourth plunger P4, which are arranged opposite to each other and have a phase difference of 1/4 period of the cam C with respect to the first set of plungers P1 and P3, is basic. becomes. Therefore, as another embodiment, such four plungers P may be grouped together, and four other plungers P having a phase difference of one-eighth of the cam C period may be provided.

[Second embodiment]
11 and 12 show a second embodiment of a fluid pump S according to the invention. The fluid pump S is, for example, an axial pump S2 having a basic configuration of four plungers P1 to P4. 12(a) is a perspective view showing the cam C seen from the II-II cross section of FIG. 11, and FIG. 12(b) shows the bottom wall portion Kc of the casing K seen from the II-II cross section of FIG. It is a top view.

The first plunger P1 to fourth plunger P4 are provided in a plunger holder H that rotates around the rotation axis X. As shown in FIG. Each plunger P has a cylinder 2, a piston 1, and a spring member 3 of the same shape, which are arranged around the rotation axis X with an angular difference of 90 degrees. Among them, the cylinder 2 is inserted into four cylindrical holes provided in the plunger holder H, for example. Pistons 1 are inserted into these cylinders 2 with spring members 3 arranged therein.

Reciprocating axes X1 along which the pistons 1 reciprocate in the respective plungers P are parallel to each other. Further, the distances between the rotation axis X and each reciprocation axis X1 are all set to be the same in the example of FIG. However, the position of the piston 1 in the diametrical direction of the annular cam surface C1' is arbitrary, since the piston 1 may perform desired protruding/retracting operations corresponding to the rotational angular velocity of the plunger holder H.

Four pistons 1 are exposed from one first end surface H1 along the rotation axis X of the outer surface of the plunger holder H in a state in which the amount of protrusion thereof can be changed. 11 and 12, four openings 5 communicating with the cylinders 2 are formed in the other second end surface H2 along the rotation axis X of the outer surface of the plunger holder H. . These ports serve as the fluid W suction port 6a and discharge port 6b.

The plunger holder H is enclosed in a casing K as shown in FIG. A rotating shaft H3 protrudes from the second end surface H2 of the plunger holder H so as to pass through the bottom wall portion Kc of the casing K. As shown in FIG. The rotating shaft H3 passes through a bearing portion Kb formed in the bottom wall portion Kc of the casing K and protrudes to the outside. At the end of the rotating shaft H3, there is provided a drive transmission section H4 such as a gear that receives a rotational driving force from a driving section G (not shown).

An annular cam C' is arranged on the first inner surface Ka of the casing K facing the first end surface H1 of the plunger holder H. As shown in FIG. An annular cam surface C<b>1 ′ is formed along the rotational trajectory of each piston 1 on the annular cam C′. The annular cam surface C1' is inclined when viewed in a direction perpendicular to the rotation axis X, as shown in FIG. 11, for example. By tilting in this way, every time a specific plunger P makes one turn around the rotation axis X, the piston 1 supplies and discharges the fluid W once.

As shown in FIGS. 11 and 12, the annular cam surface C1' of this embodiment is not a simple inclined surface, but a discharge rate adjusting surface C2' (hatched area in FIG. 12(a)) similar to that of the first embodiment. is provided. For example, when the plunger holder H rotates, the fluid W is discharged when a specific plunger P moves from point a to point e in FIG. 12(a). At the point a, the height of the annular cam surface C1' gradually increases, and reaches the maximum inclination angle at the point c via the point b. After that, the slope becomes gentle at point d, and becomes zero again at point e. The area on the opposite side of the annular cam surface C1' that forms the intake stroke is symmetrical with respect to the straight line connecting the points a and e.

By configuring in this way, the suction mode and the discharge mode of the fluid W are the same as those shown in the first embodiment, and the discharge flow rate of the fluid W becomes constant.

Further, with this configuration, the four plungers P1 to P4 rotate, and the opening 5 of the cylinder 2 sequentially communicates with the suction port 6a and the discharge port 6b. Therefore, at least one supply path R1 and at least one discharge path R2 should be formed in the casing K, which simplifies the construction of piping. Furthermore, unlike the first embodiment, there is no need to provide a check valve in each of the supply path R1 and the discharge path R2, further simplifying the structure.

With the fluid pump S of this configuration, the discharge flow rate of the fluid W can be changed by changing the rotation speed of the plunger holder H. Also, by reversing the rotational direction of the plunger holder H, the suction port 6a and the discharge port 6b can be interchanged. Furthermore, by setting the number of pistons 1 provided in the plunger holder H to, for example, 8, 12, etc., which is a multiple of 4, which is the basic configuration, a fluid pump S having different discharge flow rates while suppressing pulsation can be obtained. can also

[Third embodiment]
(overall overview)
In this embodiment, an example using a vane pump S3 as one of the fluid pumps S is shown. The vane pump S3 maintains a constant discharge flow rate when the fluid W is discharged, eliminates pulsation in the piping through which the fluid W flows, and reduces vibration and noise. The vane pump S3 will be described below with reference to FIGS. 13 to 18. FIG.

(overall structure)
The vane pump S3 of this embodiment includes a rotor r having at least four vanes V and a cam ring Cr having a cam surface Ca on which the tips of the vanes V slide. A mover D is formed by these vanes V and rotor r.

(rotor)
As shown in FIG. 13, the rotor r has, for example, a cylindrical side surface and two flat end surfaces, and is rotatable about the rotation axis X. As shown in FIG. The direction of rotation can be changed according to the installation location of the vane pump S3. The outer peripheral portion is provided with four grooves r1 for accommodating the vanes V so as to move forward and backward. When two vanes V adjacent to each other in the rotation direction are regarded as one set, the vane V leading in the rotation direction is called a leading vane V1, and the vane V following behind is called a trailing vane V2. The vane V is, for example, a rectangular flat plate member, and can smoothly slide in the radial direction along the groove r1. The outer edge of the vane V is in sliding contact with the cam surface Ca of the cam ring Cr. In the vane pump S3 of the present invention, it is convenient to set the number of vanes V to a multiple of 4, such as 8 or 16, for example.

(cam ring)
As shown in FIG. 13, the cam ring Cr is, for example, an annular member, and has a cam surface Ca with which the vane V is in sliding contact on its inner peripheral surface. The cam surface Ca is substantially circular, and its center is provided at a position eccentric to the rotation axis X of the rotor r. The cam ring Cr forms a discharge chamber 11 for discharging the fluid W and a suction chamber 21 for sucking the fluid W between the rotor r and the vane V. As shown in FIG. Among these, the discharge chamber 11 functions as the volume chamber B in particular.

(casing)
A cam ring Cr is fixed to the inner surface of the casing K, and a bearing portion (not shown) is provided for rotating the rotor r eccentrically with respect to the cam ring Cr. The shaft portion of the rotor r extends outside the rotor r, and is connected to a driving gear or the like so as to be rotationally driven by a driving portion G (not shown).

Further, the casing K is divided on the same plane as the outer surface of the rotor r and perpendicular to the rotation axis X, for example. One casing K1 is formed with a concave portion K3 in which the rotor r is installed. The other casing K2 is formed with a discharge port 10 and a suction port 20 that open into the space between the outer peripheral surface r2 of the rotor r and the cam surface Ca, as indicated by the two-dot chain line in FIG. . A discharge passage (not shown) communicating with the discharge chamber 11 to discharge the fluid W is connected to the discharge port 10 . The suction port 20 is connected to a suction path (not shown) that communicates with the suction chamber 21 and sucks the fluid W. As shown in FIG. In particular, in the discharge port 10, the edge portion on the upper side in the rotational direction is referred to as an upper edge portion 10a, and the edge portion on the lower side in the rotational direction is referred to as a lower edge portion 10b.

As shown in FIG. 13, the direction in which the rotation axis X of the rotor r is eccentric with respect to the cam surface Ca, that is, the position where the cam surface Ca and the outer peripheral surface r2 of the rotor r are closest to each other is taken as the rotation angle of the rotor r. Assuming that the position is 180 degrees, the ejection port 10 is formed over the range from the 45-degree position to the 135-degree position. Similarly, the inlet 20 is formed over a range of 225 degrees to 315 degrees. As a result, when the rotor r is in the state shown in FIG. 13, the vane chambers A at the positions of 0 and 180 degrees are momentarily shielded, the vane chamber A at the position of 90 degrees is in the discharging state, and the vane chamber A is in the discharge state. The vane chamber A at the position is in the suction state.

14(a) and 14(b) respectively show a state in which the discharge of the fluid W is started and a state in which the discharge of the fluid W is finished in the vane pump S3 formed in this way. FIG. 14(a) shows a state in which one vane V overlaps the discharge port 10, the fluid W1 in the first vane chamber A1 is being discharged, and the fluid W2 in the second vane chamber A2 has started to be discharged. On the other hand, in FIG. 14(b), the vane V approaches the terminal end of the discharge port 10, the discharge amount of the fluid W2 from the second vane chamber A2 increases, and discharge of the fluid W1 from the first vane chamber A1 ends. It shows the state just before

(discharge rate control surface)
In the present embodiment, as shown in FIG. 13, the cam surface Ca is basically a perfect circle, but a predetermined area of the cam surface Ca has a shape different from the perfect circle. A position corresponding to the upper edge portion 10a of the discharge port 10 on the cam surface Ca is defined as a first position C10, and a position corresponding to the lower edge portion 10b is defined as a second position C20. and a region extending from the second position C20 to a position near the upper side in the rotation direction, as indicated by the broken line, a discharge amount adjusting surface C3 having a small change in the inner diameter along the moving direction of the vane V. Prepare.

In FIG. 13, the discharge amount adjusting surface C3 is provided on both sides of the cam surface Ca in the circumferential direction across the first position C10 and on both sides in the circumferential direction across the second position C20. shows an example.

FIG. 15 shows how the discharge chamber 11 moves while changing its volume as the rotor r rotates. Of the two vanes V forming one vane chamber A, the leading vane V1 and the following vane V2 in the rotational direction of the rotor r are defined. FIG. 15(a) shows a state in which the leading vane V1 of the first vane chamber A1 is at the first position C10 on the cam surface Ca, and the phase of the rotor r at this time is the first phase. FIG. 15(e) shows a state in which the trailing vane V2 of the first vane chamber A1 has moved to the second position C20 on the cam surface Ca, and the phase of the rotor r at this time is the second phase. That is, the fluid W in the first vane chamber A1 is discharged from the discharge port 10 while the rotor r shifts from the first phase to the second phase.

(Conventional vane pump with perfectly circular cam surface)
Before describing the operation of the vane pump S3 of the present embodiment, the operation of the conventional vane pump S3 having the perfect circular cam surface Ca will be described. FIG. 24 shows how the rotor r shifts from the first phase to the second phase. 25 is a graph showing changes in the volume of each vane chamber A, FIG. 26 is a graph showing changes in the instantaneous discharge suction amount of each vane chamber A, and FIG. and the total instantaneous discharge amount of the entire vane pump S3.

25, the horizontal axis represents the rotation angle of the rotor r, and the vertical axis represents the volume of the vane chamber A. In FIG. The volume of the vane chamber A is set to zero when the rotor r is in the second phase, and increases toward the first phase. Assuming that the time when the rotor r completes one revolution is one period, the change in volume of each vane chamber A is sequentially delayed by 1/4 period. The volume change curve of vane chamber A resembles a sine curve.

26 shows the instantaneous flow rate of fluid W drawn into or discharged from vane chamber A. FIG. That is, it is synonymous with differentiating the curve in FIG. 25 with respect to the rotation angle of the rotor r.

FIG. 27 shows only the instantaneous discharge amount of the fluid W discharged, omitting the portion where the fluid W is sucked into the four vane chambers A from the curve shown in FIG. Furthermore, the thick line that changes into a waveform in the figure indicates the total instantaneous ejection amount obtained by adding these four curves. A vertical change in the total amount of instantaneous ejection indicates the presence of pulsation.

When the cross-sectional shape of the cam surface Ca is a perfect circle, the curve indicating the instantaneous total discharge amount has a shape obtained by simply joining together substantially arcuate curves, as shown in FIG. 27 . In this case, the curve bends at an acute angle, especially at the moment when the discharge rate decreases and then increases again. Here, the instantaneous total amount of ejection changes abruptly and a constant pulsation occurs.

To reduce this pulsation, for example, the number of vane chambers A should be increased. By doing so, the fluctuation range of the fluid W discharged from each vane chamber A is moderated, and the cycle of pulsation is shortened. However, simply increasing the number of vane chambers A cannot completely eliminate pulsation. Therefore, in the present embodiment, the cross-sectional shape of the cam surface Ca, which is a perfect circle, is modified as described below.

(Vane pump in which a cam surface is formed with a discharge amount adjusting surface)
(When the instantaneous discharge volume is maximized at the center phase)
Immediately after the rotor r rotates and enters the first phase, the discharge of the fluid W from the first vane chamber A1 is started. Discharge of the fluid W becomes zero when it reaches. In this embodiment, by forming the discharge amount adjusting surface C3, the rotor r is in the state shown in FIG. , the instantaneous discharge amount of the fluid W is maximized. This central phase is referred to as the maximum ejection phase.

As shown in FIG. 13, the discharge rate adjusting surfaces C3 are formed on both sides of the cam surface Ca in the circumferential direction across the first position C10 and on both sides in the circumferential direction across the second position C20. Form. Among them, on the side of the first position C10, as shown in FIG. 13, the inner diameter is formed to be larger than the perfect circular virtual cam surface Cb (indicated by the dotted line). In particular, on the downstream side of the first position C10, the diameter is slightly larger than that of the cam surface Cb, and the diameter is reduced more moderately than the diameter reduction rate of the cam surface Cb. That is, the cam surface Ca is configured so as to reduce the speed at which the vane V enters the groove r1.

On the other hand, at the second position C20, as shown in FIG. 13, the inner diameter is formed smaller than the imaginary perfect circle cam surface Cb. In particular, on the upper side of the second position C20, the diameter is slightly smaller than that of the cam surface Cb. Further, the diameter is reduced early from a position before the second position C20, so that the diameter is reduced more moderately than the diameter reduction rate of the cam surface Cb. Also in this case, the speed at which the vane V enters the groove portion r1 is moderated.

By configuring in this way, the vane V that has passed the first position C10 moves for a while, and then the speed at which it enters the groove portion r1 rapidly increases. In addition, the vane V approaching the second position C20 slows down the speed of entering the groove r1 before the second position C20. As a result, changes in the volume of the vane chamber A immediately after the first position C10 and before the second position C20 are moderated. On the other hand, in the vicinity of the center position between the first phase and the second phase, a state appears in which the instantaneous ejection amount rapidly increases and then decreases rapidly in order to secure the ejection amount of the fluid W. FIG. That is, during the period from the first phase to the maximum ejection phase of the rotor r, a state in which the instantaneous ejection amount rapidly increases and a state in which the instantaneous ejection amount gradually increases appear in succession. In between, a state in which the instantaneous discharge amount rapidly decreases and a state in which the instantaneous discharge amount decreases continuously appear.

Moreover, in this embodiment, the cam surface Ca is formed so that the instantaneous discharge amount of the fluid W is maximized when the rotor r is in the middle phase between the first phase and the second phase. Such a shape of the cam surface Ca is determined by calculating changes in the vane chamber A formed by the rotor r, the vanes V, and the cam surface Ca according to the rotation angle of the rotor r.

The above configuration will be specifically described using graphs. FIG. 16 is a graph showing changes in volume of each vane chamber A when the cam ring Cr of this embodiment shown in FIG. 13 is used, and FIG. FIG. 18 is a graph showing the instantaneous discharge amount and total instantaneous discharge amount of each vane chamber A. In FIG.

In order to keep the total instantaneous discharge amount constant as shown in FIG. 18, the curve of the instantaneous discharge amount of each vane chamber A must be appropriately set. Specifically, the degree of change in the instantaneous flow rate is reduced when the instantaneous discharge amount becomes zero and when it reaches its maximum. As shown in FIG. 18, for example, when the instantaneous discharge amount of each vane chamber A is represented, each curve has a shape in which the horizontal axis of zero instantaneous discharge amount and the horizontal axis of the total instantaneous discharge amount are in contact with each other.

As shown in FIG. 13, such an instantaneous discharge amount curve can be obtained by forming a discharge amount control surface C3 as indicated by a wavy line at the first position C10 and the second position C20. By configuring the shape of the cam surface Ca in this way, when the rotor r shifts from the first phase to the second phase, the amount of change in volume of the vane chamber A per unit rotation angle of the rotor r (instantaneous change from the vane chamber A discharge amount) is maximized at a position between the first phase and the second phase. That is, as shown in FIG. 17, for example, with respect to the solid line indicating the instantaneous discharge amount of the first vane chamber A1, the maximum discharge phase is reached at point c, which is an intermediate position between point a, which is the first phase, and point e, which is the second phase. becomes.

With this configuration, the process of increasing and decreasing the discharge amount of the fluid W can be most easily balanced. In particular, since the maximum ejection phase is located at an intermediate position between the first phase and the second phase, the shape of the cam surface Ca is provided with ejection amount adjusting surfaces C3 in the vicinity of the first position C10 and in the vicinity of the second position C20. Therefore, it becomes easy to balance the discharge increase amount and the discharge decrease amount of the fluid W with respect to the unit rotation angle of the rotor r. Therefore, the vane pump S3 with less pulsation of the fluid W can be obtained.

(Inflection point at the center between the first phase and the maximum ejection phase, and at the center between the maximum ejection phase and the second phase)
Further, the shape of the discharge amount adjusting surface C3 can be further configured as follows. That is, when the rotor r rotates from the first phase to the maximum ejection phase, the instantaneous ejection amount is switched from a rapid increase to a gradual increase at the middle phase between the first phase and the maximum ejection phase. Further, when the rotor r rotates from the maximum ejection phase to the second phase, the instantaneous ejection amount is switched from a sudden decrease to a gradual decrease at the middle phase between the maximum ejection phase and the second phase.

For example, as shown in FIG. 17, the solid line indicating the instantaneous discharge amount of the first vane chamber A1 is divided into two regions, the front and the back, from point a, which is the first phase, to point c, which is the maximum discharge phase. The first half is the area from point a to point b, where the instantaneous discharge rate gradually increases and then sharply increases to the maximum slope of the curve. This is a region up to point c where the amount of increase gradually decreases and the instantaneous ejection amount reaches a maximum. This point c is the maximum ejection phase.

On the other hand, the region from point c, which is the maximum ejection phase, to point e, which is the second phase, is also divided into two regions in front and behind. That is, the first half is the area from point c to point d where the instantaneous discharge amount gradually decreases and then sharply decreases and the slope of the curve reaches the maximum. This is the area up to the point e where the minute is reduced and the instantaneous ejection amount becomes zero. The change in the instantaneous discharge amount from point a to point e occurs similarly when the vane chamber A sucks the fluid W exposed to the suction port 20 .

In this way, by providing the cam surface Ca with the discharge rate adjusting surface C3, one set of the first vane chamber A1 and the third vane chamber A3 and one set of the second vane chamber A2 and the fourth vane chamber A4 are formed. The change in the discharge amount of the fluid W obtained by each pair becomes very smooth. Therefore, when adding the discharge amount from each set of vane chambers A in order to obtain the total fluid discharge amount of the vane pump S3, the change in the total discharge amount becomes smooth and the pulsation is greatly reduced.

As a result of forming the cam surface Ca in consideration of these points, two instantaneous discharge amount curves are obtained as shown in FIG. One of them is a composite curve of the first vane chamber A1 and the third vane chamber A3 which are opposite in phase to each other, and the other is the second vane chamber A2 and the fourth vane chamber which are in opposite phases to each other. It is a composite curve with A4. With such a curve shape, the instantaneous total discharge amount obtained by adding the flow rates of both synthetic curves becomes substantially constant.

As in this configuration, in the process of increasing and decreasing the instantaneous discharge amount of the fluid W, by providing the change point of the increase characteristic and the decrease characteristic exactly at the center position in the rotation phase of the rotor r, the maximum The change characteristic of the instantaneous ejection amount up to the ejection phase and the change characteristic of the instantaneous ejection amount from the maximum ejection phase to the second phase can be brought closer to symmetry. As a result, the balance between the increased amount and decreased amount of discharge of the fluid W with respect to the unit rotation angle of the rotor r becomes more appropriate. Therefore, the vane pump S3 with even less pulsation can be obtained.

(Point symmetrical at the center between the first phase and the maximum ejection phase, line symmetry across the maximum ejection phase)
However, in order to keep constant the total instantaneous discharge amount obtained by adding the flow rates of both synthetic curves as shown in FIG. 18, it is necessary to further limit the shape of both synthetic curves. That is, in the vane pump S3 of the present embodiment, the mode of increase in the instantaneous discharge amount from the first phase to the maximum discharge phase is reversed across the center position between the first phase and the maximum discharge phase, and increases from the first phase to the maximum discharge phase. The ejection amount adjustment surface C3 is formed so that the increase in the instantaneous ejection amount up to the ejection phase and the decrease in the instantaneous ejection amount from the maximum ejection phase to the second phase are symmetrical with respect to the maximum ejection phase. It is convenient to be there.

That is, as shown in FIG. 17, when the rotor r rotates from point a, which is the first phase, to point c, which is the maximum ejection phase, the increase in the instantaneous ejection amount is at the center position between points a and c. Assume that the image is inverted across a certain point b. Points b and d are points of inflection, and a curve from point a to point b and a curve from point b to point c are symmetrical with respect to point b. Also, a curve from point c to point d and a curve from point d to point e, which is the second phase, are configured point-symmetrically with respect to point d.

In addition to this, the increase mode of the instantaneous discharge amount when the rotor r in FIG. be symmetrical across the That is, the curve from the point a to the point c is configured to have a symmetrical shape with the curve from the point c to the point e across the point c. With this configuration, the total instantaneous discharge amount obtained by totaling the instantaneous discharge amounts of the first vane chamber A1 to the fourth vane chamber A4 becomes substantially constant as shown in FIG. 18, and the pulsation is eliminated.

[Fourth embodiment]
The vane pump S3 shown in the third embodiment includes, as shown in FIG. A second vane chamber A2 arranged opposite to each other across the rotation axis X and having a phase difference of 1/4 period of the rotor r with respect to the first pair of first vane chamber A1 and third vane chamber A3. and the second set of the fourth vane chamber A4 are basically combined.

This concept can be expanded, for example, as shown in FIG. It is also possible to provide another four vane chambers A1' to A4' having a total of eight vanes V. FIG. Furthermore, if four vane chambers are combined into one set, the total number of vanes V can be set to a multiple of 4, such as a 12-blade configuration or a 16-blade configuration.

With this configuration, for example, a plurality of vane chambers A4', A4, and A3' open to the discharge port 10. As shown in FIG. As a result, increases and decreases in the instantaneous discharge amount of the fluid W associated with the respective vane chambers are offset, pulsation of the fluid W is reduced, and the vane pump S3 with less vibration and noise can be obtained.

[Fifth Embodiment]
For example, as shown in FIGS. 20 and 21, it is also possible to change the instantaneous ejection amount in a trapezoidal manner. For this purpose, a region in which the contraction amount of the inner diameter is moderated is formed on a part of the cam surface Ca so that the maximum instantaneous discharge amount can be maintained for a certain period of time.

Specifically, when the angle at which the rotor r rotates from the first phase to the second phase is defined as the discharge rotation angle, the cam surface Ca is downstream from the first position C10 by half the discharge rotation angle. Locate. In most cases, the ejection rotation angle is 180 degrees, so the position 90 degrees from the first position C10 is specified. As shown in FIG. 20, in the area sandwiching this position along the rotation direction of the rotor r, the discharge amount adjustment is performed in which the degree of reduction of the inner diameter of the cam surface Ca centered on the rotation axis X of the rotor r is slightly gradual. A plane C3 (area of wavy line) is formed.

As a result, when the preceding vane V1 constituting the vane chamber A1 reaches the end portion C31 of the discharge amount adjusting surface C3 (point a in FIG. 21), the instantaneous discharge amount stops increasing, and the preceding vane V1 reaches the discharge amount adjusting surface C3. The instantaneous ejection amount maintains the maximum value during the passage (area from point a to point b in FIG. 21). After that, when the preceding vane V1 passes the downstream end C32 of the discharge amount adjusting surface C3 (point b in FIG. 21) and enters the cam surface Ca, which is reduced in diameter in a normal mode, the instantaneous discharge amount decreases. When the rotor r further rotates and the trailing vane V2' passes the second position C20, the instantaneous discharge amount from the vane chamber A1 becomes zero.

With this configuration, it is possible to widen the phase at which the instantaneous ejection amount is maximized. Accordingly, the phase region in which the instantaneous discharge amount changes is narrowed, and the time during which the instantaneous discharge amount is constant during the rotation of the rotor r is lengthened, and the pulsation generated by the entire vane pump S3 is reduced.

[Sixth embodiment]
As for the increase/decrease mode of the instantaneous discharge amount, it is also possible to adopt a mode in which it changes in a triangular shape as shown in FIGS. 22 and 23 . For this purpose, an inflection point C4 at which the amount of contraction of the inner diameter changes is provided on a part of the cam surface Ca, and the instantaneous discharge amount of the fluid W is reversed from increasing to decreasing at the inflection point C4.

Specifically, on the cam surface Ca downstream from the first position C10, there is an angle (90 degrees) half the discharge rotation angle (usually 180 degrees) at which the rotor r rotates from the first phase to the second phase. An inflection point C4 is provided at the position where Until the leading vane V1 reaches the inflection point C4, the discharge amount adjusting surface C3a is formed on the cam surface Ca so that the amount of protrusion of the leading vane V1 with respect to the rotor r is shortened at a predetermined rate. After passing the inflection point C4, a discharge amount adjustment surface C3b (indicated by a wavy line in FIG. 22) is formed so that the rate of decrease in the amount of protrusion is somewhat moderated. As a result, the reduction in the volume of the vane chamber A1 is alleviated, and the instantaneous discharge amount of the fluid W rapidly changes from an increase to a decrease as shown at point a in FIG.

With this configuration, when forming the cam surface Ca, one ejection amount adjusting surface C3a for increasing the instantaneous ejection amount and one ejection amount adjusting surface C3b for decreasing the instantaneous ejection amount may be formed before and after the inflection point C4. good. Therefore, the configuration of the cam surface Ca is simplified, and the manufacturing cost of the vane pump S3 can be reduced.

In FIGS. 21 and 23, a straight line indicates a region where the instantaneous discharge amount of the fluid W is maximum or a portion other than the maximum position. However, it is more effective to reduce the pulsation of the vane pump S3 if these regions are composed of curves, that is, the changes in the instantaneous discharge amount of the fluid W are made smoother.

[Determination of the number of volumetric chambers and the operating ratio of each volumetric chamber]
As shown in each of the above embodiments, in order to eliminate the pulsation, when the discharge of the fluid W from one of the volume chambers B such as the cylinder 2 and the vane chamber A ends, the discharge of the fluid from the other volume chambers B is started. , the instantaneous discharge amount of the fluid W needs to increase and decrease continuously. A plurality of sets of such increase/decrease characteristics are set by determining the configurations of the volume chamber B and the cam C. FIG.

For example, in the first embodiment, an example of the radial pump S1 using four cylinders 2 was shown, and in the third embodiment, an example of the vane pump S3 using four vanes V was shown. In these examples, as shown in FIG. 9 or FIG. 17, in each cylinder 2 or vane chamber A, the rotational angle of the cam C or the rotational angle of the rotor r when the fluid W is sucked and the fluid W discharged both angles are the same. In other words, the time required for suction and discharge is the same, and in such a fluid pump S, the change in the speed of the piston 1 and the change in the moving speed of the vane V provided on the rotor r are smooth, which is mechanically impossible. It is possible to obtain a fluid pump S without

In these examples, as shown in FIGS. 10 and 18, two cylinders 2 or two vane chambers A form pairs for discharging the fluid W, and the respective pairs discharge the fluid W alternately. Also, the number of cylinders 2 or vane chambers A discharging the fluid W at the same time is two.

However, in the fluid pump S of the present invention, it is not necessary to set the suction time and the discharge time for one volume chamber B equally. For example, by setting the profile of the cam C, it is possible to set the suction time shorter than the discharge time in each volume chamber B. In this case, the fluid W is sucked into the volume chamber B at once and then slowly discharged. However, especially when only the ejection process that affects the pulsation is considered, the pulsation is greatly reduced by the slow ejection. Therefore, in the fluid pump S of the present invention, the number of volume chambers B and the operating ratio of each volume chamber B are determined as follows.

In the fluid pump S of the present invention, by providing three or more volume chambers B and three or more sliders D, the pressure fluctuations of the fluid W generated in each volume chamber B cancel each other out, and the fluid pump S as a whole is free from pulsation. Obtainable.

First, the manner in which the fluid W is discharged per volume chamber B is determined. Among the one cycle rotation angle Z of the cam C that defines the discharge time of the fluid W, the rotation angle that defines the state of discharging the fluid W in one volume chamber B is defined as the discharge rotation angle α. The ejection rotation angle α is the rotation angle from the start phase at which the instantaneous ejection amount of the fluid W is zero, through the center phase at which the instantaneous ejection amount is maximized, to the end phase at which the instantaneous ejection amount is zero again.

When the number of volume chambers B is M, and N is any integer from 2 to (M-1),
Discharge rotation angle α=(Z/M)×N
Defined as
Here, M is an integer of 3 or more representing the number of volume chambers B, and N is any integer from 2 to (M−1).

FIG. 28 shows the relationship between the cam rotation angle and the instantaneous discharge amount in a radial pump S1 having three cylinders 2, for example. Similarly, FIGS. 29(a), (b), and (c) are for a radial pump S1 having four cylinders 2, and FIGS. is.

The value of Z/M is the difference in the rotation angles at which the respective volume chambers B discharge during one cycle. For example, when M=4 and one cycle rotation angle Z=360 degrees, the discharge operation of each volume chamber B is performed each time the cam C rotates 90 degrees, as shown in FIG.

On the other hand, the N value indicates how many volume chambers B are in the discharge state at a certain timing. Therefore, as the N value increases, one volume chamber B discharges the fluid W over a longer rotation angle.

N=1 never occurs. When N=1, one volume chamber B always discharges the fluid W, and pulsation is always generated in the discharge operation of one volume chamber B as described above. This is because the pulsation cannot be eliminated even if the ejection of B is continued.

On the other hand, it is also not true that N=M. N=M means that the fluid W is always discharged from all the volume chambers B, and in this case, the period for sucking the fluid W into each volume chamber B cannot be secured.

Therefore, as shown in FIG. 28, when M=3, the number N of volume chambers B simultaneously in the discharge state is only two. Further, as shown in FIG. 29, when M=4, the number N of the volume chambers B simultaneously in the discharge state is 2 or 3. Further, as shown in FIG. 30, when M=5, the number N of the volume chambers B simultaneously in the discharge state is 2 to 4.

Note that the N value is an integer. In other words, since it is impossible for one volume chamber B to be in the discharge state only half of the time, the N value becomes a small number, as shown in FIG. At another instant, the two volume chambers B are in the discharge state, so the discharge state is not constant and the pulsation is not eliminated. Therefore, N is an integer between 2 and (M-1).

In addition to satisfying the above conditions, when any one of the volume chambers B is in the end phase, the volume chamber B in which discharge starts next to this volume chamber B must be in the start phase. is. For example, if N=2, at a given moment, a particular volume chamber B is in the discharge state together with other volume chambers B that have started to discharge before it. If an attempt is made to keep the overall discharge rate constant at the start and end of discharge from each of the volume chambers B, when a specific volume chamber B has just started discharge, the other volume chambers B will have a predetermined discharge rate. must be secured.

Then, the discharge work of the specific volume chamber B joins the discharge work of the volume chamber B that started discharge immediately before itself, and after the discharge work of the volume chamber B immediately before is completed, the discharge work of the volume chamber B immediately before itself The volume chamber B that starts the discharge operation after one is replaced by this, and the decrease in the discharge amount of itself is compensated for by the discharge of the volume chamber B one after. Furthermore, when its own ejection is completed, it will be replaced by the volumetric chamber B that starts ejection two times behind itself.

In this way, in order for the N volume chambers B to always perform the discharge operation, when a specific volume chamber B is in the end phase, the next volume chamber B is the first volume chamber B, and the Nth volume chamber B is Must be the starting phase.

Furthermore, in order to keep the total discharge amount of the volume chambers B, which are simultaneously discharged, to be constant, the mode of increase and decrease of the instantaneous discharge amount of each volume chamber B is set to the phase exactly intermediate between the start phase and the center phase. When one intermediate phase is used, the increasing tendency of the instantaneous discharge amount from the start phase to the first intermediate phase and the increasing tendency from the first intermediate phase to the middle phase are configured to be reversed with the first intermediate phase interposed therebetween. . Further, the tendency of increase from the start phase to the middle phase and the tendency of decrease of the instantaneous ejection amount from the middle phase to the end phase are symmetrical with respect to the middle phase. For example, when imagining a graph with the rotational phase on the horizontal axis and the instantaneous ejection amount on the vertical axis, it is convenient for the continuous ejection curve to be like a sine curve or triangular wave.

By defining the increase/decrease mode of the instantaneous discharge amount of each volume chamber B in this manner, the overall instantaneous discharge amount is always constant regardless of the rotation angle of the cam C. FIG. Therefore, the pressure fluctuations of the fluid W occurring in the respective volume chambers B are canceled out while increasing the degree of freedom in the number of volume chambers B to be installed, and the fluid pump S free from pulsation as a whole can be obtained.

INDUSTRIAL APPLICABILITY The fluid pump according to the present invention can be widely applied to pumps such as radial pumps having a plurality of cylinders, vane pumps having a rotor with vanes, etc., in which a cam is used to relatively move a volume chamber and a mover. .

1 Piston 2 Cylinder 10 Discharge port 10a Upper edge 10b Lower edge 11 Discharge chamber 20 Suction port 21 Suction chamber C Cam C1 Cam surface C1' Annular cam surface C2 Discharge amount adjusting surface C3 Discharge amount adjusting surface C4 Inflection point C10 1st position C20 2nd position Ca Cam surface Cd Bottom dead line corresponding point Cr Cam ring Cu Top dead line corresponding point K Casing P Plunger R1 Supply passage R2 Discharge passage r Rotor S Fluid pump V Vane V1 Leading vane V2 Trailing vane W Fluid X Rotation shaft core

Claims (8)

three or more volume chambers for sequentially drawing and discharging fluid;
a moving element provided in each of the volume chambers and moving relative to the volume chambers to suck and discharge the fluid into and out of the volume chambers;
A non- rotatable cam that drives the moving element to abut against it by rotation, and has a circular cam area and a non-circular cam that reduces changes in the position of the moving element with respect to a unit rotation to reduce changes in the instantaneous discharge amount of the fluid. a cam having a perfectly circular discharge rate adjusting surface;
a drive unit that drives the cam to relatively rotate the mover and the cam, and discharges the fluid once from each of the volume chambers in one cycle of the relative rotation;
For each of the volume chambers, when the fluid is sucked/discharged, the momentary ejection amount of the fluid is zero after reaching a start phase in which the instantaneous ejection amount of the fluid is zero within one cycle rotation angle Z of the one cycle. The ejection rotation angle α from the maximum central phase to the end phase in which the instantaneous ejection amount is zero again is an integer of 2 to (M−1) where the number of the volume chambers is M. As N
α=(Z/M)×N
and
When any one of the volume chambers is in the end phase, the N-th volume chamber following the volume chamber is in the start phase,
When the phase exactly intermediate between the start phase and the center phase is defined as the first intermediate phase, the increasing tendency of the instantaneous ejection amount from the start phase to the first intermediate phase and the tendency from the first intermediate phase to the center the increasing trend up to the phase reverses across the first intermediate phase;
The fluid pump, wherein the tendency of increase from the start phase to the middle phase and the tendency of decrease of the fluid from the middle phase to the end phase are symmetrical with respect to the middle phase. The volume chamber is a cylinder having at least one opening for supplying and discharging the fluid, and
The mover is a piston that reciprocates inside the cylinder,
at least one of the cam and the cylinder are rotatable to repeatedly drive the piston through bottom dead center and top dead center;
the start phase is a phase in which the cam positions the piston at the bottom dead center;
2. The fluid pump of claim 1, wherein said end phase is a phase in which said cam positions said piston at said top dead center. On the cam surface of the cam, a point corresponding to the bottom dead center that positions the piston at the bottom dead center and a point corresponding to the top dead center that positions the piston at the top dead center are defined as regions of the perfect circular cam. The discharge amount adjusting surface is provided on both sides of the point corresponding to the bottom dead and on both sides of the point corresponding to the top dead,
Since the discharge amount adjusting surfaces on both sides of the point corresponding to the bottom dead end are recessed inward in the radial direction with respect to the circular cam, the instantaneous discharge amount is increased in the region from the start phase to the first intermediate phase. With the rapid increase, the instantaneous ejection amount gradually increases in the region from the first intermediate phase to the central phase,
Since the discharge amount adjusting surfaces on both sides of the top dead corresponding point bulge outward in the radial direction with respect to the perfect circular cam, the second discharge amount adjustment surface is located between the center phase and the end phase. 3. The fluid pump according to claim 2, wherein said instantaneous discharge amount rapidly decreases in a region up to an intermediate phase, and said instantaneous discharge amount gradually decreases in a region from said second intermediate phase to said end phase. 4. A fluid pump according to claim 2 or 3, wherein said cam is rotatable around a rotation axis, and a cam surface of said cam is formed on a cylindrical side surface positioned around said rotation axis. The mover is a rotor that rotates around a rotation axis and a plurality of vanes provided on the rotor that can extend and retract with respect to the rotor,
the volume chamber is formed by the rotor and the vanes, and a casing enclosing the rotor and the vanes, and is a suction chamber and a discharge chamber distributed around the rotation axis;
The cam is provided on the inner surface of the casing so as to be slidably contactable with the vane,
The casing is provided with a discharge port communicating with the discharge chamber for discharging the fluid,
In the discharge port, the upper side in the rotation direction of the rotor is defined as an upper edge, and the lower side in the rotation direction is defined as a lower edge,
Adjacent two of the vanes are used as a leading vane and a trailing vane,
the starting phase is the phase when the rotor positions the leading vane at the upper edge;
2. The fluid pump of claim 1, wherein said ending phase is the phase when said rotor positions said trailing vane at said trailing edge. Of the cam, a first position where the preceding vane slides in the start phase and a second position where the trailing vane slides in the end phase are defined as regions of the perfect circular cam. The discharge rate adjusting surface is provided on both sides and both sides of the second position,
The instantaneous ejection amount rapidly increases in the region from the start phase to the first intermediate phase, and the instantaneous ejection amount gradually increases in the region from the first intermediate phase to the center phase,
In a region from the center phase to a second intermediate phase exactly intermediate between the center phase and the end phase, the instantaneous ejection amount sharply decreases, and in a region from the second intermediate phase to the end phase, the instantaneous ejection amount. 6. The fluid pump of claim 5 , wherein . a second discharge amount adjusting surface having a small change in inner diameter along the direction of rotation is provided in a region of the cam that is positioned exactly midway between the first position and the second position;
7. The fluid pump of claim 6 , wherein said instantaneous displacement is maintained at a maximum value while said leading vane is in sliding contact with said second displacement control surface. An inflection point is provided in the cam at an intermediate position between the first position and the second position, and when the preceding vane passes through the inflection point, the instantaneous discharge amount decreases from an increasing state. 7. A fluid pump according to claim 6 , adapted for abrupt changes in state.

Images