Patent Publication Number: US-7713034-B2

Title: Diaphragm pump and manufacturing device of electronic component

Description:
TECHNICAL FIELD 
   The present invention relates to a diaphragm pump for transferring a predetermined volume of liquid and a manufacturing device of electronic component. The diaphragm pump according to the present invention can find applications in the field of continuously transferring (discharging) liquid, which may be selected from acidic or alkaline medicinal liquids, soldering pastes, solvents such as alcohol and adhesives with minimal pulsation. The diaphragm pump can and further find applications in manufacturing devices of electronic components such as a die bonder, in which a semiconductor chip is fixed to the substrate by the adhesives discharged from a diaphragm pump, or a manufacturing device for manufacturing light-emitting diode (LED), in which the LED chip is sealed by the resin discharged from a diaphragm pump, or the like. 
   BACKGROUND ART 
   Diaphragm pumps using a diaphragm made of synthetic resin thin film are being used in various industrial fields including the chemical industry, the pharmaceutical industry, the semiconductor industry and the printing industry because of the advantages they provide including that the liquid can be transferred without being damaged, that it is not necessary to use an anti-leakage seal member and that it can be arranged so that liquid does not contact any metal. 
   However, such diaphragm pumps normally generate pulsation because liquid is taken in and discharged by reciprocating the diaphragm. 
   Arrangements of combining a pair of diaphragm pumps and using them complementarily so as not to generate any pulsation at the liquid discharge side are proposed for the purpose of suppressing the pulsation of a diaphragm pump (see, for instance, Reference 1: Japanese Patent Laid-Open Publication No. 2003-042069). 
   In addition, arrangements of sequentially closing three chambers with diaphragms, which functions as a pump without providing a check valve, has been also proposed (see, for instance, Reference 2: specification of U.S. Pat. No. 5,593,290). 
   However, such combined diaphragm pumps disclosed in Reference 1 are provided with a check valve for preventing liquid from flowing backward. In other words, they are accompanied by a problem that they cannot allow liquid to flow back. 
   In the pump disclosed in Reference 2, since the diaphragm is deformed by a liquid, it is difficult to speed up a drive operation, and since chambers of plural systems are provided in parallel, it is difficult to reduce size and weight. 
   DISCLOSURE OF THE INVENTION 
   An object of the present invention is to provide a diaphragm pump capable of operating with minimal pulsation and liquid to flow back without necessity of the use of a check valve, size and weight of which can be easily reduced, and also to provide a manufacturing device of electronic component using the diaphragm. 
   A diaphragm pump according to an aspect of the present invention includes: a flow path block; a diaphragm arranged so as to closely contact the flow path block; a drive unit for reciprocating the diaphragm; and at least three liquid flow paths defined by the flow path block and the diaphragm intercommunicating a suction flow path and a discharge flow path of a liquid. The flow path block is provided with either one of the suction flow path and the discharge flow path on a central axis portion of a diaphragm-contacting surface to which the diaphragm is closely contacted, and the other one of the suction flow path and the discharge flow path on an outer circumferential side of the diaphragm-contacting surface. A suction valve chamber intercommunicating with the suction flow path, a discharge valve chamber intercommunicating with the discharge flow path, and a metering chamber formed between the suction valve chamber and the discharge valve chamber so as to intercommunicate therewith are provided respectively on the middle of the respective flow paths of the liquid. The drive unit includes: a suction pressing member arranged in correspondence with the suction valve chamber with the diaphragm interposed therebetween; a discharge pressing member arranged in correspondence with the discharge valve chamber with the diaphragm interposed therebetween; a metering-chamber pressing member arranged in correspondence with the metering chamber with the diaphragm interposed therebetween; and a pressing member drive controller for controlling drives of the respective pressing members. The pressing member drive controller includes: a rotary drive source; a cam rotated by the rotary drive source; and a biasing unit for biasing the pressing members to abut on cam faces of the cam. The pressing member drive controller performs operations by a predetermined timing set for each of the pressing members by rotating the cam with the rotary drive source to reciprocate the respective pressing members to follow the cam faces, the operations including: a suction valve chamber sealing operation for moving the suction pressing member toward the flow path block to move a portion of the diaphragm corresponding to the suction valve chamber until the portion closely contacts the flow path block to hermetically seal the suction valve chamber; a discharge valve chamber sealing operation for moving the discharge pressing member toward the flow path block to move a portion of the diaphragm corresponding to the discharge valve chamber until the portion closely contacts the flow path block to hermetically seal the discharge valve chamber; a suction valve chamber opening operation for moving the suction pressing member in a direction away from the flow path block and detaching the portion of the diaphragm corresponding to the suction valve chamber that has closely contacted the flow path block from the flow path block to open the suction valve chamber; a discharge valve chamber opening operation for moving the discharge pressing member in a direction away from the flow path block and detaching the portion of the diaphragm corresponding to the discharge valve chamber that has closely contacted the flow path block from the flow path block to open the discharge valve chamber; a volume decrease operation for moving the metering-chamber pressing member toward the flow path block to move a portion of the diaphragm corresponding to the metering chamber toward the flow path block to gradually decrease the volume of the metering chamber; and a volume increase operation for moving the metering-chamber pressing member in a direction away from the flow path block to move the portion of the diaphragm corresponding to the metering chamber away from the flow path block to gradually increase the volume of the metering chamber. 
   With the above-described arrangement according to the present invention, each of the valve chambers can be opened and closed, and the volume of the metering chamber can be increased and decreased by driving each of the pressing members corresponding to each of the valve chambers and the metering chamber arranged along each of the liquid flow paths to reciprocate at predetermined timings. Therefore, liquid is prevented from flowing backward without using a check valve when each of the pressing members is moved at predetermined timings while the liquid is being transferred. Thus, since no check valve is provided, each of the pressing members can be driven to move reversely so as to allow liquid to flow backward. 
   Additionally, since at least three liquid flow paths are formed and each of the valve chambers and the metering chamber are arranged along each of the liquid flow paths, while pressing members are provided to correspond to the respective valve chambers and metering chamber so as to set the timing of transferring liquid for each of the flow paths, a predetermined volume of liquid can be transferred continuously simply by shifting the timings of transferring liquid of the liquid flow paths by a predetermined phase, and further the pump can be operated with minimal pulsation. 
   Still additionally, in a diaphragm pump according to the present invention, only the portions of the single diaphragm that corresponds to the respective valve chambers and metering chamber are driven to move separately unlike conventional diaphragm pumps in which the entire diaphragm is driven to reciprocate. Therefore, only a small area of the diaphragm may be driven and hence the error in the volume of liquid to be transferred that may arise due to deformation or the like of the diaphragm is minimized. As a result, a diaphragm pump according to the present invention can accurately transfer a very small amount of liquid. 
   Further, the side of the drive unit for driving the pressing members and the side where the liquid flow paths, the valve chambers and the metering chamber are provided and hence liquid flows are divided simply by arranging the diaphragm. Therefore, it is not necessary to provide seal members and hence the number of components is reduced accordingly. 
   Furthermore, since the diaphragm is made of an elastically deformable material such as rubber, particle-containing liquid such as silver paste, solder paste, resin with silica powder contained, or the like can be discharged without crushing particles contained therein so that liquid can be transferred without being damaged. 
   In the present invention, since one of the suction flow path and the discharge flow path is formed on the central axis portion of the diaphragm-contacting surface, and the other one of the suction flow path and the discharge flow path is formed on the outer circumferential side of the diaphragm-contacting surface, three or more liquid paths for intercommunicating the suction flow path and the discharge flow path can be formed radially or spirally from the central axis portion toward the outer circumference. The respective pressing members provided corresponding to the respective liquid flow paths are reciprocated by following the cam face only by rotating the cam with the rotary drive source. Thus, the pressing member drive controller can be constituted with the cam having the cam face on the end surface, the rotary drive source such as a motor for rotating the cam and the biasing unit such as spring for causing the respective pressing members abut on the cam face, so that the diaphragm pump can be reduced in size and weight. Thus, when used in dispensing adhesives, various pastes and the like in production lines of various products, the diaphragm pump of the present invention can be attached to robot arms and moved by high speed and high acceleration, so that the takt time of the production lines can be shortened, which enhances productivity. 
   In the present invention, only by rotating the cam by the rotary drive source including a motor and the like, each of the pressing members can be repeatedly operated with a predetermined timing. Since the liquid transfer rate can be set to constant for each one cycle of operation for each of the pressing members, the liquid transfer rate per unit of time can be adjusted only by adjusting rotation speed of the cam. Thus, the liquid transfer rate of the diaphragm pump can be controlled easily, so that the diaphragm pump (dispenser) with high convenience can be realized. 
   Preferably, in the present invention, the suction and discharge pressing members and the metering-chamber pressing member each have a substantially semispherical recess formed on an end surface on the cam face side and a ball disposed in the recess and adapted to abut on the cam face, in which and coefficient of friction between the ball and the recess is set to be smaller than coefficient of friction between the cam face and the ball. 
   In the present invention described above, a cam follower that abuts on the cam face can be formed with a recess formed on each of the pressing members and a ball disposed in the recess. Thus, as compared to a conventional arrangement using a roller, the cam face and the cam follower can be downsized, resulting in downsizing the diaphragm pump itself. When the roller is used, since a roller shaft has to be outwardly projected from the pressing member with the roller rotatably provided on the roller shaft, the diameter of locus of movement of the roller rotating along the cam face becomes large, so that the diameter of the cam also needs to be enlarged in accordance with the locus of movement of the roller. 
   On the other hand, in the present invention, the ball can be disposed in the recess of the pressing member and the pressing member does not have a projection projecting outwardly therefrom, the diameter of locus of movement of the ball can be small, so that the diaphragm pump can be simplified in its arrangement and downsized easily. 
   In the present invention, since the coefficient of friction between the ball and the recess holding the ball is set to be smaller than the coefficient of friction between the cam face and the ball, even if a force in a rotary shaft direction or the like is applied to the ball in accordance with the rotation, the force is absorbed as the ball and the recess of the pressing member slide. Thus, slide slipping or the like does not occur between the cam face and the ball, and thereby the ball can be rolled relative to the cam face without sliding. Therefore, unlike the conventional arrangement in which the cam face had to be formed with an oleoresin or the like in consideration of friction, the cam face can be formed with a hard material such as metal and the ball can also formed with a hard material, so that an error in stroke amount of the pressing member can be decreased, enhancing dispensing accuracy of the liquid. 
   Preferably, in the diaphragm pump according to the present invention, the pressing member drive controller performs steps including: a suction step for hermetically sealing the metering chamber by moving the metering-chamber pressing member provided corresponding to the metering chamber toward the flow path block to bring the portion of the diaphragm corresponding to the metering chamber into close contact with the flow path block and sucking liquid into the suction valve chamber from the suction flow path by moving the suction pressing member provided corresponding to the suction valve chamber away from the flow path block to detach the portion of the diaphragm corresponding to the suction valve chamber from the flow path block; a first transfer step for hermetically sealing the discharge valve chamber by moving the discharge pressing member provided corresponding to the discharge valve chamber toward the flow path block to bring the portion of the diaphragm corresponding to the discharge valve chamber into close contact with the flow path block, increasing the volume of the metering chamber by moving the metering-chamber pressing member in a direction away from the flow path block to detach the portion of the diaphragm corresponding to the metering chamber from the flow path block, and decreasing the volume of the suction valve chamber by moving the suction pressing member toward the flow path block to move the portion of the diaphragm corresponding to the suction valve chamber toward the flow path block to transfer the liquid from the suction valve chamber to the metering chamber; a metering step for hermetically sealing the suction valve chamber by moving the suction pressing member toward the flow path block to bring the portion of the diaphragm corresponding to the suction valve chamber into close contact with the flow path block while keeping the discharge valve chamber hermetically sealed, and dividedly isolating the liquid in the suction valve chamber and the discharge valve chamber to meter the volume of the liquid; a second transfer step for transferring the liquid from the metering chamber to the discharge valve chamber by moving the metering-chamber pressing member toward the flow path block to decrease the volume of the metering chamber to move the discharge pressing member in a direction away from the flow path block to increase the volume of the discharge valve chamber while keeping the suction valve chamber hermetically sealed; and a discharge step for transferring the liquid from the discharge valve chamber to the discharge flow path by hermetically sealing the metering chamber and moving the discharge pressing member toward the flow path block to decrease the volume of the discharge valve chamber. 
   With the above-described arrangement, since the metering chamber is hermetically sealed in the suction step and the discharge step, the liquid no longer flows back from the metering chamber to the suction valve chamber in the suction step and from the discharge valve chamber to the metering chamber in the discharge step. Therefore, any liquid is prevented from flowing back simply by operating the pressing members and hence it is not necessary to provide a check valve. 
   Additionally, since a metering step of hermetically sealing the suction valve chamber and the discharge valve chamber and dividedly isolating the liquid between the respective valve chambers, i.e. the metering chamber portion to meter liquid is provided, the volume of liquid that is transferred through each of the liquid flow paths can be secured accurately. 
   Preferably, in the diaphragm pump according to the present invention, the pressing member drive controller performs the suction step and the discharge step while hermetically sealing the metering chamber, by moving the suction pressing member toward the flow path block to suck the liquid from the suction flow path into the suction valve chamber and moving the discharge pressing member toward the flow path block to transfer the liquid from the discharge valve chamber to the discharge flow path. 
   With the above-described arrangement, since both the suction step and the discharge step are executed simultaneously, the cycle time of the liquid transferring step is curtailed to transfer liquid efficiently. 
   Preferably, in the diaphragm pump according to the present invention, the pressing member drive controller performs steps including: a suction step for sucking the liquid from the suction flow path into the metering chamber via the suction valve chamber; by moving the suction pressing member provided corresponding to the suction valve chamber in a direction away from the flow path block to detach the part of the valve chamber corresponding to the suction valve chamber from the flow path block to intercommunicate the suction flow path and the metering chamber while the discharge valve chamber is kept hermetically sealed; and by moving the metering-chamber pressing member arranged corresponding to the metering chamber away from the flow path block to detach the portion of the diaphragm corresponding to the metering chamber from the flow path block to increase the volume of the metering chamber; a metering step for hermetically sealing the suction valve chamber by moving the suction pressing member toward the flow path block to bring the portion of the diaphragm corresponding the suction valve chamber into close contact with the flow path block while keeping the discharge valve chamber hermetically sealed, and dividedly isolating the liquid in the suction valve chamber and the discharge valve chamber to meter the volume of the liquid; and a discharge step for transferring the liquid from the metering chamber to the discharge flow path via the discharge valve chamber; by moving the discharge pressing member in a direction away from the flow path block to intercommunicate the metering chamber and the discharge flow path while keeping the suction valve chamber hermetically sealed; and by moving the metering-chamber pressing member provided corresponding to the metering chamber toward the flow path block to decrease the volume of the metering chamber. 
   With such arrangement, since the discharge valve chamber is hermetically sealed in the suction step, the suction valve chamber is hermetically sealed in the discharge step, and the respective valve chambers are hermetically sealed in the metering step, the liquid does not flow back from the discharge flow path to the suction flow path in each of the steps. Therefore, the liquid can be securely prevented from flowing back only by operations of the respective pressing members, which does not require a check valve. 
   Since the metering step of hermetically sealing the suction valve chamber and the discharge valve chamber and dividedly isolating the liquid between the respective valve chamber (metering chamber portion) for metering, transfer rate of the liquid in each of the liquid flow paths can be set with high accuracy. Preferably, in the diaphragm pump according to the present invention, the pressing member drive controller includes the discharge step having a discharge rate increasing step for gradually increasing the discharge rate and a discharge rate decreasing step for gradually decreasing the discharge rate and, in which the discharge valve chamber includes a plurality of discharge valve chambers, one of the plurality of discharge valve chambers being in the discharge-rate increasing step and at least other one of the plurality of discharge valve chambers being in the discharge-rate decreasing step, thereby keeping a constant discharge level. 
   With the above-described arrangement, when liquid transfer from one of the liquid flow paths into the discharge flow path ends, another liquid transfer from other one of the liquid flow path into the discharge flow path can be started in an overlapping manner. Thus, the operation of switching a liquid transfer operation from one of the liquid flow paths to another liquid transfer operation from other one of the liquid flow paths is conducted smoothly so that the liquid transfer operation can be continued, maintaining a constant liquid transfer rate, and thus the overall liquid transfer operation is conducted with minimal pulsation. 
   Preferably, in the diaphragm pump according to present invention, the suction valve chamber, the metering chamber and the discharge valve chamber formed along the respective liquid flow paths are displaced from each other by a first predefined angle in a circumferential direction around a central axis of the diaphragm-contacting surface with the respective dimensions from the central axis differentiated from each other; the suction valve chambers, the metering chambers and the discharge valve chambers arranged along the respective flow paths are respectively displaced from each other by a second predefined angle in the circumferential direction around the central axis of the diaphragm-contacting surface; and the suction valve chamber, the discharge valve chamber and the metering chamber are spirally arranged from the central axis of the diaphragm-contacting surface. 
   Preferably, in the diaphragm pump according to the present invention, the first predefined angle is 30° and the second predefined angle is 72°; and a total of five sets of the liquid flow paths, suction valve chambers, metering chambers and discharge valve chambers are provided. 
   With the above-described arrangement, since the respective valve chambers and metering chamber are arranged to extend spirally from the central axis, it is possible to down size spaces for arranging the respective valve chambers and metering chamber, resulting in downsizing the diaphragm pump. 
   Additionally, the respective valve chambers and metering chamber are displaced from each other by a first predetermined angle. Therefore, if the pressing members driven by the cam are arranged so as to correspond to the respective valve chambers and the metering chamber, it is not necessary to shift the phases of the cam face of the cam and each of the areas of the cam face can be arranged radially as viewed from the central axis, so that the cam can be manufactured easily. 
   When the cam faces are angularly shifted from each other by 90° so that a cycle of operation is performed by rotating the cam by 90°, each of the liquid flow paths can realize four cycles of liquid transfer operation when the cam is driven to make a full turn. Therefore, if five liquid flow paths are provided, for instance, a total of 5×4=20 cycles of liquid transfer operation are realized by the entire pump during a full turn of the cam. With this arrangement, the volume of transferred liquid for each full turn of the cam is increased to reduce pulsation. 
   Preferably, in the diaphragm pump according to the present invention, the suction valve chamber, the metering chamber and the discharge valve chamber formed along the respective liquid flow paths are linearly formed in the circumferential direction around the central axis of the diaphragm-contacting surface with the respective dimensions from the central axis differentiated from each other; the suction valve chambers, the metering chambers and the discharge valve chambers formed along the respective flow paths are respectively displaced from each other by a second predefined angle in the circumferential direction around the central axis of the diaphragm-contacting surface; and the suction valve chamber, the discharge valve chamber and the metering chamber are radially arranged from the central axis of the diaphragm-contacting surface. 
   With such arrangement, since the valve chambers and the metering chamber are disposed radially from the central axis, the respective valve chambers and the metering chamber can be manufactured easily. 
   When the cam faces are angularly shifted from each other by 90° so that a cycle of operation is performed by rotating the cam by 90°, each of the liquid flow paths can realize four cycles of liquid transfer operation when the cam is driven to make a full turn. Therefore, if five liquid flow paths are provided, for instance, a total of 5×4=20 cycles of liquid transfer operation are realized by the entire pump during one rotation of the cam, and thus the liquid transfer rate per one rotation of the cam can be increased, which reduces pulsation. 
   Preferably, in the diaphragm pump according to the present invention, a recessed groove is formed on the diaphragm-contacting surface of the flow path block in close contact with the diaphragm; a flow-path-block contacting surface of the diaphragm in close contact with the flow path block has a planar profile; and the flow path of the liquid is defined by the recessed groove of the flow path block and the flow path block contacting surface of the diaphragm. 
   As the recessed groove is formed on the flow path block side to provide the liquid flow path, the diaphragm can be formed in a simple planar profile. Thus, the diaphragm that is a consumable and needs to be replaced whenever it is worn can be provided at low cost. Additionally, if the liquid flow paths are formed on the flow path block side, a dimensional precision of the flow path can be enhanced, so that the liquid transfer rate can be controlled accurately on a stable basis to reduce fluctuations in the liquid transfer rate. 
   Preferably, in the diaphragm pump according the present invention, the diaphragm-contacting surface of the flow path block in close contact with the diaphragm has a planar profile; a recessed groove is formed on the flow-path-block contacting surface of the diaphragm in close contact with to the flow path block; and the liquid flow path is defined by the diaphragm-contacting surface of the flow path block and the recessed groove of the diaphragm. 
   When the recessed groove is formed on the diaphragm side to provide liquid flow path, diaphragm-contacting surface of the flow path block can be formed in a planar profile. When, on the other hand, the recessed groove is formed on the flow path block side that is made of metal, the flow path block needs to be manufactured by preparing a metal mold or by cutting recessed grooves. When a metal mold for producing a molded metal product is used, the cost of initial investment will be high. When, the recessed groove is formed by cutting, the processing cost will be high and it is impossible to process the respective valve chambers, the metering chamber and communication grooves to be very small, so that transfer of a very small quantity of liquid will be difficult. 
   On the other hand, when the recessed groove is formed on the diaphragm side, a rubber die used to mold the rubber diaphragm is relatively inexpensive, so that the cost of initial investment is reduced. In addition, the valve chambers, the metering chamber and the flow paths having the communication grooves or the like can be dimensionally reduced when the rubber die is used, so that transfer of a very small quantity of liquid without difficulty. 
   In the diaphragm pump according to the present invention, both the diaphragm-contacting surface of the flow path block and the flow-path-block-contacting surface of the diaphragm may be provided with the recessed grooves. Preferably, in the diaphragm pump according to the present invention, the recessed groove includes: a suction-valve-chamber recess, a metering-chamber recess and a discharge-valve-chamber recess that respectively define the suction valve chamber, the metering chamber and the discharge valve chamber; a communication groove for intercommunicating the suction-valve-chamber recess and the suction flow path; a communication groove for intercommunicating the discharge-valve-chamber recess and the discharge flow path; and a communication groove for intercommunicating the suction valve-chamber recess/discharge-valve-chamber recess and the metering chamber-recess. The recess may have a width same as or larger than the width of the respective communication grooves. The values of the widths may be selected appropriately according to the quantity of the liquid to be transferred. 
   Preferably, in the diaphragm pump according to the present invention, the cam face of the cam includes a plane orthogonal to a rotary shaft of the cam, the plane provided with three cam grooves concentrically arranged around the rotary shaft of the cam. 
   With such arrangement, movements of the respective pressing members can be controlled by changing the depth of the cam groove. 
   In a ball is used as a cam follower, the cam groove can be a rounded groove having a substantially arcuate cross section, which can be formed and processed by a ball end mill, thereby reducing processing cost. 
   According to another aspect of the present invention, a manufacturing device of an electronic component includes: the above-described diaphragm pump of the present invention, a liquid supplier for supplying the liquid to the suction flow path of the diaphragm pump, a discharge nozzle provided on the discharge flow path, and a controller for controlling the drive unit of the diaphragm pump, in which the liquid supplied by the liquid supplier is discharged from the discharge nozzle through the diaphragm pump to manufacture the electric component. 
   In such a manufacturing device of electronic component, since the above-described diaphragm pump capable of accurately transferring a trace quantity of liquid is employed, the trace quantity of liquid can be accurately discharged from the discharge nozzle. Further, liquid containing silver powder, silica power or the like can be discharged without crushing particles. Accordingly, by applying the technology to the manufacturing process such as bonding the semiconductor chip, sealing the LED chip or the like, defective products can be reduced and manufacturing efficiency can be improved. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is an illustration showing a first embodiment of the present invention; 
       FIG. 2  is a plan view of a recess forming surface of a base block of the embodiment; 
       FIG. 3  is a cross section of a principal part of the embodiment; 
       FIG. 4  is an illustration of the disposition of a recess on the recess forming surface; 
       FIG. 5  is a plan view of a guide block of the embodiment; 
       FIG. 6A  is a cross section of a cam of the embodiment; 
       FIG. 6B  is a plan view of a cam face of the embodiment; 
       FIG. 7  is a cam diagram of the cam of the embodiment; 
       FIG. 8A  is a cross section showing a state where a first pressing rod of the embodiment is at the 0° position of the cam face; 
       FIG. 8B  is a plan view showing the state of  FIG. 8A ; 
       FIG. 8C  is a cross section showing a state where the first pressing rod of the embodiment is at the 15° position of the cam face; 
       FIG. 8D  is a plan view showing the state of  FIG. 8C ; 
       FIG. 9A  is a cross section showing a state where the first pressing rod of the embodiment is at the 27° position of the cam face; 
       FIG. 9B  is a plan view showing the state of  FIG. 9A ; 
       FIG. 9C  is a cross section showing a state where the first pressing rod of the embodiment is at the 45° position of the cam face; 
       FIG. 9D  is a plan view showing the state of  FIG. 9C ; 
       FIG. 10A  is a cross section showing a state where the first pressing rod of the embodiment is at the 57° position of the cam face; 
       FIG. 10B  is a plan view showing the state of  FIG. 10A ; 
       FIG. 10C  is a cross section showing a state where the first pressing rod of the embodiment is at the 75° position of the cam face; 
       FIG. 10D  is a plan view showing the state of  FIG. 10C ; 
       FIG. 11  is a graph showing the displacements of the first through third pressing rods relative to rotation angle of the cam of the embodiment; 
       FIG. 12  is a graph showing changes in liquid transfer rate of the embodiment; 
       FIG. 13  is a cross section of a principal part of a second embodiment of the present invention; 
       FIG. 14A  is a plan view of a pressing-rod-abutting surface of the diaphragm of the second embodiment; 
       FIG. 14B  is a cross section taken along line A-A in  FIG. 14A ; 
       FIG. 14C  is a plan view of a flow-path-block-contacting surface of the diaphragm of the second embodiment; 
       FIG. 15  is a cross section of a principal part of a third embodiment of the present invention; 
       FIG. 16A  is a cross section of a cam of the third embodiment; 
       FIG. 16B  is a plan view of a cam face of the third embodiment; 
       FIG. 17A  is an illustration showing a first cam groove of the third embodiment; 
       FIG. 17B  is an illustration showing a second cam groove of the third embodiment; 
       FIG. 17C  is an illustration showing a third cam groove of the third embodiment; 
       FIG. 18  is a cam diagram of the first cam groove of the cam of the third embodiment; 
       FIG. 19  is a cam diagram of the second cam groove of the cam of the third embodiment; 
       FIG. 20  is a cam diagram of the first cam groove of the cam of the third embodiment; 
       FIG. 21  is a graph showing the displacements of a first through third pressing rods relative to rotation angle of the cam of the third embodiment; 
       FIG. 22A  is a cross section showing a state where a first pressing rod of the third embodiment is at the 0° position of the cam face; 
       FIG. 22B  is a plan view showing the state of  FIG. 22A ; 
       FIG. 22C  is a cross section showing a state where the first pressing rod of the third embodiment is at the 21° position of the cam face; 
       FIG. 22D  is a plan view showing the state of  FIG. 22C ; 
       FIG. 23A  is a cross section showing a state where the first pressing rod of the third embodiment is at the 30° position of the cam face; 
       FIG. 23B  is a plan view showing the state of  FIG. 23A ; 
       FIG. 23C  is a cross section showing a state where the first pressing rod of the third embodiment is at the 39° position of the cam face; 
       FIG. 23D  is a plan view showing the state of  FIG. 23C ; 
       FIG. 24A  is a cross section showing a state where the first pressing rod of the third embodiment is at the 66° position of the cam face; 
       FIG. 24B  is a plan view showing the state of  FIG. 24A ; 
       FIG. 24C  is a cross section showing a state where the first pressing rod of the third embodiment is at the 75° position of the cam face; 
       FIG. 24D  is a plan view showing the state of  FIG. 24C ; 
       FIG. 25  is a plan view of a principal part of a modification of the present invention; 
       FIG. 26  is a cross section of a principal part of another modification of the present invention; and 
       FIG. 27  is a plan view of a principal part of still another modification of the present invention. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   Embodiments of the present invention will be described in more detail by referring to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a schematic view of the first embodiment of a diaphragm pump  1  according to the present invention. 
   The diaphragm pump  1  has a base block  2 , a holder ring block  3 , a guide block  4 , a fitting block  5  and a drive unit  6 . 
   Each of the blocks  2  through  5  is provided with through holes (not shown) at the four corners thereof. Each of the blocks  2  through  5  is assembled by means of a coupling bolt penetrating through the base block  2  and the holder ring block  3  to be screwed into the guide block  4 , a coupling bolt screwed into the guide block  4  via the fitting block  5 , a coupling bolt screwed into the drive unit  6  via the fitting block  5  and so on. Positioning pins are also used to align the blocks. 
   As shown in  FIGS. 2 and 3 , the base block  2  has a recess forming surface  21  that is a diaphragm-contacting surface opposed to the guide block  4 . The recess forming surface  21  is formed by a planar area defined to show a substantially circular boundary. A port  22  is formed around the central axis of the recess forming surface  21  so as to define a discharge flow path or suction flow path of liquid and a plurality of recesses  23  through  25  are formed around it. 
   The port  22  penetrates from the center of the recess forming surface  21  to the opposite surface  26  of the base block  2 . 
   In the present embodiment, a nozzle member  27  is fitted to the opening at an end of the port  22  on the side of surface  26  and the port  22  is utilized as discharge port (discharge flow path). 
   The recess forming surface  21  is provided with first recess  23  formed along the outer circumference of the recess forming surface  21 , second recess  24  formed on an inner side relative to the first recess  23  and third recess  25  arranged inside relative to the second recess  24  and hence around the port  22 . Each of recesses  23  through  25  is a recess formed in a semispherical profile. The first recess  23  intercommunicates with the outside of the outer circumference of the recess forming surface  21  via a communication groove  281 . The second recess  24  intercommunicates with the first recess  23  via a communication groove  282  and with the third recess  25  via a communication groove  283 . The third recess  25  intercommunicates with the port  22  via a communication groove  284 . 
   In other words, recessed grooves formed on the diaphragm-contacting surface include the first recess  23 , the second recess  24 , the third recess  25  and the communication grooves  281  through  284  formed on the recess forming surface  21 , which is the diaphragm-contacting surface of the base block  2 . Liquid flow paths  280  are formed by the spaces defined by the recessed grooves and a diaphragm  8 . A total of five sets of liquid flow paths  280  are provided in the present embodiment. 
   More specifically, the first recess  23  includes five recesses  23 A through  23 E and the second recess  24  includes five recesses  24 A through  24 E, while the third recess  25  includes five recesses  25 A through  25 E. 
   In the present embodiment, the first recesses  23  ( 23 A through  23 E) and the second recesses  24  ( 24 A through  24 E) are arranged in such a way that the lines connecting the centers of the recesses  23 ,  24  and the center of the port  22  form an angle of intersection of a first defined angle, which is equal to 30° as shown in  FIG. 4 . Similarly, the second recesses  24  ( 24 A through  24 E) and the third recesses  25  ( 25 A through  25 E) are arranged in such a way that the lines connecting the centers of the recesses  24 ,  25  and the center of the port  22  form an angle of intersection of the first defined angle, which is equal to 30°. 
   Additionally, the recesses  23 ,  24 ,  25  are arranged in such a way that the length of the lines connecting the center of the port  22  and the centers of the recesses  23 , the length of the lines connecting the center of the port  22  and the centers of the recesses  24 , and the length of the lines connecting the center of the port  22  and the centers of the recesses  25  become smaller in the mentioned order. 
   Thus, as a result, the recesses  23 A through  23 E,  24 A through  24 E and  25 A through  25 E are arranged to extend spirally from the center of the port  22 . 
   In the present embodiment, a total of five sets of recesses  23  through  25  are provided and the first recesses  23 A through  23 E are arranged around the port  22  at an angular pitch of 360/5=72° (a second defined angle). Similarly, the second recesses  24 A through  24 E are arranged at an angular pitch of 72° (the second defined angle) and so are the third recesses  25 A through  25 E. 
   The holder ring block  3  has a substantially hollow cylindrical profile and fitted to the outer periphery of the base block  2 . More specifically, the holder ring block  3  is pinched between the flange  28  of the base block  2  and the guide block  4 . The holder ring block  3  is provided with a port  31  that operates as liquid supply hole or discharge hole. In the present embodiment, the port  31  is threaded and a liquid transfer tube  30  is attached thereto. 
   The port  31  of the holder ring block  3  intercommunicates with a space  33  that is formed at the inner periphery side of the holder ring block  3 , or between the holder ring block  3  and the base block  2 , by way of a through hole  32 . 
   A seal member  34  that is typically an O-ring is arranged in the space  33  at a position closer to the flange  28  than the through hole  32  in order to prevent liquid in the space  33  from leaking to the outside through the abutting surfaces of the flange  28  and the holder ring block  3 . 
   The diaphragm  8  is fitted to an end surface of the holder ring block  3  that faces the guide block  4 . More specifically, a ring-shaped recessed groove  35  is formed on the end surface of the holder ring block  3  and the peripheral edge of the diaphragm  8  is fitted to the recessed groove  35 . The peripheral edge of the diaphragm  8  is pinched between the holder ring block  3  and the guide block  4 . 
   Thus, the space  33  is defined by the seal member  34  and the diaphragm  8  so that liquid in the space is prevented from leaking to the outside. In the present embodiment, a suction flow path of liquid is formed by the space  33  and a flow path block is formed by the base block  2  and the holder ring block  3 . 
   Therefore, in the present embodiment, the first recess  23  operate as suction valve chamber recess and the second recess  24  operate as metering chamber recess, while the third recess  25  operate as discharge valve chamber recess. 
   The diaphragm  8  is made of elastically deformable rubber (synthetic rubber, natural rubber) or the like and has a substantially disk-shaped profile. The flow-path-block-contacting surface of the diaphragm  8  that is closely contacted to the base block  2  shows a planar profile. Pressing-rod-abutting surface of the diaphragm  8  that abuts on pressing rods  73  through  75  also shows a planar profile. In the present embodiment, the diaphragm  8  has a thickness of about 1 mm. 
   The gap between the recess forming surface  21  and an end surface  41  of the guide block  4  that faces the recess forming surface  21  is 0.9 mm, which is slightly smaller than the thickness of the diaphragm  8 . Thus, when the blocks  2  through  5  are assembled, the diaphragm  8  is pinched between the planar area other than the recesses  23  through  25  and the guide block  4  and pressed against the recess forming surface  21  by a predetermined pressure. Therefore, each of the recesses  23  through  25  is defined by the diaphragm  8  that is closely contacted to the recess forming surface  21  so as to intercommunicate with all the other recesses  23  through  25  only by way of the communication grooves  281  through  284 . With this arrangement, the space defined by the first recess  23  and the diaphragm  8  operates as suction valve chambers and the space defined by the second recess  24  and the diaphragm  8  operates as valve chambers, while the space defined by the third recess  25  and the diaphragm  8  operates as discharge valve chambers. Additionally, the spaces defined by the communication grooves  281  through  284  and the diaphragm  8  operate as communication paths. The liquid flow paths  280  include the respective valve chambers, the metering chamber and the communication paths. 
   As shown also in  FIG. 5 , the guide block  4  is provided with guide holes  43  through  45  penetrating in an axial direction at respective positions corresponding to the recesses  23  through  25  of the base block  2 . More specifically, first guide holes  43 A through  43 E are arranged so as to be coaxial respectively with the first recesses  23 A through  23 E and second guide holes  44 A through  44 E are arranged so as to be coaxial respectively with the second recesses  24 A through  24 E, while third guide holes  45 A through  45 E are arranged so as to be coaxial respectively with the third recesses  25 A through  25 E. 
   Each of the guide holes  43  through  45  is provided with a step at an axially intermediate position to have different diameters. The guide hole has a small diameter hole section  46  at the side of the end surface  41  and a large diameter hole section  47  at the side of the fitting block  5 . The large diameter hole section  47  has a diameter larger than the small diameter hole section  46 . 
   Pressing members, or pressing rods  73  through  75 , are inserted into the respective guide holes  43  through  45 . More specifically, the first pressing rods  73  are inserted respectively into the first guide holes  43 A through  43 E and the second pressing rods  74  are inserted respectively into the second guide holes  44 A through  44 E, while the third pressing rods  75  are inserted respectively into the third guide holes  45 A through  45 E. The first pressing rods  73  that are arranged to correspond to the suction valve chambers operate as suction side pressing members and the second pressing rods  74  that are arranged to correspond to the metering chambers operate as metering-chamber pressing members, while the third pressing rods  75  that are arranged to correspond to the discharge valve chambers operate as discharge side pressing members. 
   The pressing rods  73  through  75  respectively have small diameter sections  76  that are inserted into the small diameter hole sections  46  and large diameter sections  77  that are inserted into the large diameter hole sections  47  of the respective guide holes  43  through  45 . The axial length of the small diameter sections  76  is larger than the axial length of the small diameter hole sections  46 , so that a space is produced between the step formed by the small diameter hole section  46  and the large diameter hole section  47  and the step formed by the small diameter section  76  and the large diameter section  77  as shown in  FIG. 3 . A coil spring  78  is arranged in the spaces to bias the pressing rods  73  through  75  in a direction away from the diaphragm  8 . 
   The end surface of each of the pressing rods  73  through  75  facing the diaphragm  8  is formed in a semispherical profile. Thus, as the pressing rods  73  through  75  are driven to move toward the diaphragm  8 , the diaphragm  8  are closely contacted to the semispherical surfaces of the recesses  23  through  25 . However, since the communication grooves  281  through  284  have a small width, the diaphragm  8  do not enter the communication grooves  281  through  284  and hence the communication grooves  281  through  284  always intercommunicate with each other. 
   On the other hand, a substantially semispherical recess is formed on the other end surface of each of the pressing rods  73  through  75  and a ball  79  is housed in the recess. 
   The fitting block  5  shows a hollow cylindrical profile with a through hole running inside. The through hole has a substantially circular cross section and a cam  51  that is driven to rotate by the drive unit  6  is provided therein. The cam  51  may be directly attached to an output shaft  61  of the drive unit  6 , although it is attached to the output shaft  61  via a spline boss  52  and a spline shaft  53  in the present embodiment. More specifically, the spline shaft  53  is attached to the output. Shaft  61  by means of a pin  54  so that it can rotate integrally with the output shaft  61 . The spline boss  52  is pressed into the cam  51 . The spline boss  52  and the cam  51  are arranged in such a way that they can slide relative to the spline shaft  53  in an axial direction of the output shaft  61  and rotate integrally with the spline shaft  53  and the output shaft  61 . 
   The cam  51  and the spline boss  52  are rotatably supported by a ball bearing  55  relative to the fitting block  5 . The ball bearing  55  and the cam  51  are biased toward the guide block  4  by a coned disk spring  57  and via a spacer ring  56  while the pressing rods  73  through  75  are biased toward the cam  51  by the respective coil springs  78 . Thus, cam face  511  of the cam  51  constantly abuts the ball  79 . In other words, the coned disk spring  57  and the coil springs  78  operate as biasing unit that forces the balls  79  of the pressing rods  73  through  75  to respectively abut the corresponding cam faces  511  of the cam  51 . 
   As shown in  FIGS. 6A and 6B , the cam  51  is an end cam (solid cam) having end surface that operates as cam face  511 . The cam face  511  has a profile as illustrated in the cam diagram of  FIG. 7 . More specifically, the cam  51  has a through hole at the central axis thereof and the cam face  511  is formed around the through hole to show a ring-shaped profile. 
     FIG. 7  shows a cam diagram illustrating the profile of the cam face  511 . The y-axis of the cam diagram is so selected as to define the lowest position of the cam (y=0) where the cam face  511  is located closest to the diaphragm  8  and the highest position of the cam (e.g., y=0.5 mm in the present embodiment) where the cam face  511  is located remotest from the diaphragm  8 . On the other hand, the x-axis of the cam diagram defining a state where the ball  79  of the first pressing rod  73  abuts the lowest positions of the cam (y=0) as 0° shows the rotation angle of the cam  51 , or the rotation angle of the cam face  511  relative to the ball  79  from the position. Note that the cam diagram also illustrates the locus of movement of the center position of the ball  79 . 
   In the present embodiment, the cam face  511  operates with a cycle of 90° and the above operation is repeated for every 90°, or from 90° to 180°, from 180° to 270° and from 270° to 360°. Therefore, only the cycle from 0° to 90° will be described below. 
   When the rotation angle of the cam  51  is between 0° and 15°, a cam face  511 A remains at the lowest position (y=0). In other words, the cam face  511 A is formed by a plane orthogonal to the rotary shaft of the cam  51 . 
   When the rotation angle of the cam  51  is between 15° and 27°, the radial profile of a cam face  511 B is expressed, for instance, by a quadratic curve of y=(x−15) 2 /864. 
   When the rotation angle of the cam  51  is between 27° and 33°, the radial profile of a cam face  511 C is expressed, for instance, by a straight line of y=x/36−7/12. 
   When the rotation angle of the cam  51  is between 33° and 57°, the radial profile of a cam face  511 D is expressed, for instance, by a quadratic curve of y=0.5−(x−45) 2 /864. 
   When the rotation angle of the cam  51  is between 57° and 63°, the radial profile of a cam face  511 E is expressed, for instance, by a straight line of y=−x/36+23/12. 
   When the rotation angle of the cam  51  is between 63° and 75°, the radial profile of a cam face  511 F is expressed, for instance, by a quadratic curve of y=(x−75) 2 /864. 
   When the rotation angle of the cam  51  is between 75° and 90°, the radial profile of a cam face  511 G is a plane same as that of the cam face  511 A. 
   The cam faces  511 A through  511 G are radially arranged from the central axis of the cam faces  511 . In other words, the boundary lines of the cam faces  511 A through  511 G are straight lines extending radially from the central axis of the cam face  511 . 
   Thus, as the spline shaft  53 , the spline boss  52  and the cam  51  are rotated by the drive unit  6 , the ball  79  and the pressing rods  73  through  75  axially advance and retract along the profile of the cam face  511 . Then, as the pressing rods  73  through  75  move toward the respective recesses  23  through  25 , the volumes of the respective valve chambers and the metering chamber defined by the portions of the diaphragm  8  that correspond to the recesses  23  through  25  (portions of the diaphragm  8  corresponding to the recesses on which the pressing rods  73  through  75  respectively abut) and the recesses  23  through  25  decrease until the portions of the diaphragm  8  corresponding to the recesses closely contacts the inner surfaces of the respective recesses  23  through  25 . In other words, the pressing rods  73  through  75  operate for volume decrease. 
   Then, as the pressing rods  73  through  75  move away from the respective recesses  23  through  25 , the portions of the diaphragm  8  corresponding to the recesses detach from the inner surfaces of the respective recesses  23  through  25 , to which they have been closely attached, to consequently increase the volumes of the respective valve chambers and the metering chamber defined between the recesses  23  through  25  and the diaphragm  8 . In other words, the pressing rods  73  through  75  operate for volume increase. 
   The materials of the pressing rods  73  through  75 , the ball  79  and the cam  51  are selected and the surfaces of any of them may or may not be coated by a selected coating method so as to make the coefficient of friction between each of the pressing rods  73  through  75  and the ball  79  lower than the coefficient of friction between the ball  79  and the cam face  511 . 
   More specifically, the ball  79  is hard ball made of a super hard alloy such as tungsten carbide. The cam  51  is also made of metal such as carbon tool steel processed by quenching and polishing, so that the cam face  511  is very hard. 
   On the other hand, the pressing rods  73  through  75  and the spline boss  52  may be made of plastic (synthetic resin). The pressing rod  73  is normally made of a resin material and hence softer than the ball  79 , but the surface may be finished with DLC coating or the like to provide as hard surface as that of the ball  79 . In short, the materials of the related components may be so selected that the coefficient of friction between each of the pressing rods  73  through  75  and the ball  79  becomes lower than the coefficient of friction between the cam face  511  and the ball  79 . However, it should be noted that, although each of the pressing rods  73  through  75  is mentioned to be softer compared to the ball  79 , but is should be hard enough not to be deformed in abutting the ball  79  because the displacement of the cam face  511  have to be transmitted to the diaphragm  8  via the ball  79  and each of the pressing rods  73  through  75 . 
   The drive unit  6  may take any form so long as it is a drive source that can rotate the output shaft  61 , and various motors may be used. In the present embodiment, a servo motor provided with a reduction gear is employed. 
   A fitting plate  9  is secured to the fitting block  5  by means of screws. The diaphragm pump  1  can be fitted to any of various manufacturing devices or robot arms by way of the fitting plate  9 . 
   Since liquid is transferred through each of the liquid flow paths  280  in the present embodiment, each of the liquid flow paths  280  operates as pump. More specifically, in the present embodiment, the respective valve chambers, the metering chamber (recesses  23  through  25 ), the pressing rods  73  through  75 , the communication paths (communication grooves  281  through  284 ) and the diaphragm  8  arranged along the liquid flow paths  280  form a plurality of pumps for transferring liquid and these plurality of pumps constitute the diaphragm pump  1  so that the pump  1  can continuously transfer liquid at a constant rate with minimal pulsation. 
   Additionally, in the present embodiment, a pressing member drive controller is formed by the cam  51 , the spline boss  52 , the spline shaft  53 , the coned disk spring  57 , the drive unit  6  and the coil springs  78  to control the operation of driving the pressing rods  73  through  75  and a drive unit for driving the diaphragm  8  to reciprocate is formed by the pressing member drive controller and the pressing rods  73  through  75 . 
   Next, an operation of the embodiment will be described with reference to  FIGS. 8A through 12 . 
   [Operation of Pressing Rods] 
   Firstly, the operation of the pressing rods  73  through  75  will be described. Each of the pressing rods  73  through  75  performs operation corresponding to the profile of the cam face  511  of the cam  51 . 
   As described above, when the rotation angle of the cam  51  is between 0° and 15°, the cam face  511  remains at the lowest position (y=0) so that the balls  79  and the pressing rods  73  through  75  do not move axially with the diaphragm  8  being closely contacted to the inner surfaces of the recesses  23  through  25 . 
   With the cam face  511  in the rotation angle between 15° and 27°, the balls  79  and the pressing rods  73  through  75  move away from the diaphragm  8  at a constant acceleration. 
   With the cam face  511  in the rotation angle between 27° and 33°, the balls  79  and the pressing rods  73  through  75  move away from the diaphragm  8  at a constant speed. 
   With the cam face  511  in the rotation angle between 33° and 45°, the balls  79  and the pressing rods  73  through  75  move away from the diaphragm  8  at a constant acceleration. 
   With the cam face  511  in the rotation angle between 45° and 57°, the balls  79  and the pressing rods  73  through  75  move toward the diaphragm  8  at a constant acceleration. 
   With the cam face  511  in the rotation angle between 57° and 63°, the balls  79  and the pressing rods  73  through  75  move toward the diaphragm  8  at a constant speed. 
   With the cam face  511  in the rotation angle between 63° and 75°, the balls  79  and the pressing rods  73  through  75  move away from the diaphragm  8  at a constant acceleration. 
   When the rotation angle of the cam  51  is between 75° and 90°, the cam face  511  remains at the lowest position (y=0), so that the balls  79  and the pressing rods  73  through  75  do not move axially with the diaphragm  8  being closely contacted to the inner surfaces of the recesses  23  through  25 . 
   The cam faces  511  operate with a cycle of 90° and the above operation is repeated for every 90°, namely, from 90° to 180°, from 180° to 270° and from 270° to 360°. 
   Therefore, each of the pressing rods  73  through  75  axially reciprocate as the ball  79  abuts on the respective cam faces  511  and revolves to move (rotate) along the cam faces  511 . By the time when the cam  51  makes a full turn, each of the pressing rods  73  through  75  finishes four cycles of reciprocation. The stroke of each cycle is 0.5 mm in the present embodiment. 
   As each of the pressing rods  73  through  75  reciprocates, the diaphragm  8  moves in a direction contacting the recesses  23  through  25  to decrease the volume of the respective valve chambers and the metering chamber and then moves in a direction away from the recesses  23  through  25  to increase the volume of the respective valve chambers and the metering chamber. As a result, liquid is sucked into and discharged from the respective valve chambers and the metering chamber. 
   [Operation of Pumps (Three Pressing Rods)] 
   Now, the operation of the pumps of the diaphragm pump  1  will be described by exemplifying the operation of the first pressing rod  73 , the second pressing rod  74  and the third pressing rod  75  that are inserted respectively into the first guide hole  43 A, the second guide hole  44 A and the third guide hole  45 A. 
   In the following description, the cam  51  rotates counterclockwise relative to the recess forming surface  21  shown in  FIG. 2  (or clockwise if the cam  51  is viewed from the side of the cam face  511 ) so that the liquid is sucked from the space  33  at the outer circumference side of the recess forming surface  21  and discharged from the central port  22 . 
     FIGS. 8A ,  8 B illustrate a state where the ball  79  of each of the first pressing rods  73  is at the 0° position of the cam face  511 . In this state, the second pressing rod  74  is located at a position behind the first pressing rod  73  by 30° and hence the ball  79  thereof is located at 330° position of the cam faces  511 . Similarly, in this state, the third pressing rod  75  is located at a position behind the second pressing rod  74  by 30° and hence the ball  79  thereof is located at 300° position of the cam face  511 . 
   Thus, the first pressing rod  73  is at the position of displacement 0, where it presses the diaphragm  8  against the first recess  23 A in a closely-contacted manner, and hence the suction valve chamber defined by the first recess  23 A and a portion of the diaphragm  8  corresponding to the recess  23 A is held to a hermetically sealed condition. The second pressing rod  74  is at the position of displacement of 0.25, or the position of a half of the stroke of movement. The third pressing rod  75  is also at the position of displacement of 0.25, namely, the position of a half of the stroke of movement. Since the pressing rods  74 ,  75  are located respectively at those positions, the volume of metering chamber and the discharge valve chamber defined by the second recess  24 A, the third recess  25 A and portions of the diaphragm  8  corresponding to the recesses  24 A,  25 A reflect the respective positions of the pressing rods  74 ,  75 . 
   As the cam  51  is rotated by 15° from the state of  FIGS. 8A ,  8 B, a state of  FIGS. 8C ,  8 D arises. More specifically, the ball  79  of the first pressing rod  73  reaches to the position of 15° of the cam face  511  but, since the cam face  511 A is a plane in this phase of operation, the first pressing rod  73  is not displaced and keeps the suction valve chamber to a hermetically sealed condition. 
   At this time, the ball  79  of the second pressing rod  74  moves from the 330° to 345° of the cam face  511  and the second pressing rod  74  moves from the position of displacement 0.25 mm to the position of displacement 0 mm to come closer to the diaphragm  8 . As a result of this movement, the volume of the metering chamber is gradually decreased so that the liquid in the metering chamber is transferred to the discharge valve chamber via the communication groove  283 . 
   Similarly, the ball  79  of the third pressing rod  75  moves from 300° to 315° of the cam face  511  and the third pressing rod  75  moves from the position of displacement 0.25 mm to the position of displacement 0.5 mm to be away from the diaphragm  8 . As a result, the volume of the discharge valve chamber is gradually increased, so that the liquid transferred from the metering chamber is sucked into the discharge valve chamber. In this way, the second transfer step is carried out between the state of  FIG. 8A  and that of  FIG. 8D . 
   As the cam  51  is rotated by 12° from the state of  FIGS. 8C ,  8 D, a state of  FIGS. 9A ,  9 B arises. More specifically, the ball  79  of the first pressing rod  73  moves from 15° to 27° of the cam face  511  and the first pressing rod  73  moves away from the diaphragm  8  from the position of displacement 0 mm to the position of displacement ⅙ mm. As a result of the movement, the volume of the suction valve chamber is gradually increased, so that the liquid is sucked into the suction valve chamber from the space  33  at the outer circumference of the recess forming surface  21  via the communication groove  281 . 
   At this time, the ball  79  of the second pressing rod  74  moves from 345° to 357° of the cam face  511  but the second pressing rod  74  remains at the position of displacement 0 mm without moving axially. Thus, the diaphragm  8  keeps in close contact with the second recess  24 A and hence the metering chamber is held to a hermetically sealed condition, so that no liquid is moved via the metering chamber. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 315° to 327° of the cam face  511  and the third pressing rod  75  moves toward the diaphragm  8  from the position of displacement 0.5 mm to the position of displacement ⅓ mm. As a result of the movement, the volume of the discharge valve chamber is gradually decreased, so that the liquid in the discharge valve chamber is transferred to the port  22  via the communication groove  284 . Thus, liquid is discharged from the nozzle member  27  at the end of the port  22  at a rate corresponding to the rate of decreasing the volume of the discharge valve chamber. 
   Thus, the liquid suction step and the liquid discharge step are carried out simultaneously between the state of  FIG. 8C  and that of  FIG. 9B . 
   Although not shown in the drawings, as the ball  79  of the first pressing rod  73  moves from 27° to 33° of the cam face  511  in response to the rotation of the cam  51 , the first pressing rod  73  moves further away from the diaphragm  8  from the position of displacement ⅙ mm to the position of displacement ⅓ mm. As a result of this movement, the volume of the suction valve chamber is gradually increased, so that the liquid is sucked into the suction valve chamber from the outer circumference of the recess forming surface  21  via the communication groove  281  to continue the suction step. 
   At this time, the ball  79  of the second pressing rod  74  moves from 357° to 3° of the cam face  511  but the second pressing rod  74  remains at the position of displacement 0 mm without moving axially. Thus, the diaphragm  8  is kept in close contact with the second recess  24 A and hence the metering chamber is held to a hermetically sealed condition, so that no liquid is transferred via the metering chamber. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 327° to 333° of the cam face  511  and the third pressing rod  75  further moves toward the diaphragm  8  from the position of displacement ⅓ mm to the position of displacement ⅙ mm. As a result of the movement, the volume of the discharge valve chamber is gradually decreased, so that the transfer of the liquid in the discharge valve chamber to the port  22  and the discharge of liquid from the nozzle member  27  are continued, and the discharge step is continued. 
   As the cam  51  is further rotated and the ball  79  of the first pressing rod  73  reaches 45° from 33° of the cam face  511 , a state of  FIGS. 9C ,  9 D arises. 
   More specifically, the first pressing rod  73  moves away from the diaphragm  8  from the position of displacement ⅓ mm to the position of displacement 0.5 mm. As the first pressing rod  73  reaches the position of 0.5 mm, the stroke of movement toward the cam  51  comes to an end and the volume of the suction valve chamber is maximized, so that the liquid suction step of sucking liquid from the space  33  into the suction valve chamber is completed. 
   At this time, the ball  79  of the second pressing rod  74  moves from 3° to 15° of the cam face  511  but the second pressing rod  74  remains at the position of displacement 0 mm without moving axially. As a result, the metering chamber is held to a hermetically sealed condition. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 333° to 345° of the cam face  511  and the third pressing rod  75  moves toward the diaphragm  8  from the position of displacement ⅙ mm to the position of displacement 0 mm. As a result, the volume of the discharge valve chamber is further decreased, so that the transfer of liquid from the discharge valve chamber to the port  22  and the discharge of liquid from the nozzle member  27  are continued until the third pressing rod  75  reaches 345° of the cam face  511 . As the third pressing rod  75  moves to 345° of the cam face  511 , the diaphragm  8  closely contacts to the third recess  25 A to hermetically close the discharge valve chamber, so that the discharge of liquid from the discharge valve chamber, namely, the liquid flow path  280 , to the port  22  stops to complete the liquid discharge step. 
   Therefore, the liquid suction step and the liquid discharge step are continued between the state of  FIG. 8C  and that of  FIG. 9D . 
   As the cam  51  is further rotated and the ball  79  of the first pressing rod  73  reaches 57° from 45° of the cam face  511 , a state of  FIGS. 10A ,  10 B arises. 
   More specifically, the first pressing rod  73  moves toward the diaphragm  8  from the position of displacement 0.5 mm to the position of displacement ⅓ mm. As a result of this movement, the volume of the suction valve chamber is gradually decreased so that liquid is transferred from the suction valve chamber to the metering chamber by way of the communication groove  282 . 
   At this time, the ball  79  of the second pressing rod  74  moves from 15° to 27° of the cam face  511  and the second pressing rod  74  moves away from the diaphragm  8  from the position of displacement 0 mm to the position of displacement ⅙ mm. As a result of this movement, the volume of the metering chamber is increased gradually, so that liquid is sucked into the metering chamber from the suction valve chamber by way of the communication groove  282 . In this way, the first transfer step is carried out. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 345° to 357° of the cam face  511  but the third pressing rod  75  remains at the position of displacement 0 mm without moving axially. Thus, the discharge valve chamber is held to a hermetically sealed condition and the suspension of the discharge of liquid from the discharge valve chamber to the port  22  is maintained. 
   Although not shown in the drawings, as the ball  79  of the first pressing rod  73  moves from 57° to 63° of the cam face  511  in response to the rotation of the cam  51 , the first pressing rod  73  moves further closer to the diaphragm  8  from the position of displacement ⅓ mm to the position of displacement ⅙ mm. As a result of this movement, the volume of the suction valve chamber is further decreased, so that the transfer of liquid from the suction valve chamber to the metering chamber (first transfer step) continues. 
   At this time, the ball  79  of the second pressing rod  74  moves from 27° to 33° of the cam face  511  and the second pressing rod  74  moves away from the diaphragm  8  from the position of displacement ⅙ mm to the position of displacement ⅓ mm. As a result of this movement, the volume of the metering chamber is gradually increased and hence the suction of liquid from the suction valve chamber into the metering chamber (first transfer step) continues. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 357° to 3° of the cam face  511  but the third pressing rod  75  remains at the position of displacement 0 mm without moving axially. Thus, the discharge valve chamber is held to a hermetically sealed condition, so that the suspension of discharge of liquid from the discharge valve chamber to the port  22  is maintained. 
   As the cam  51  is further rotated and the ball  79  of the first pressing rod  73  reaches 75° from 63° of the cam face  511 , a state of  FIGS. 10C ,  10 D arises. 
   More specifically, the first pressing rod  73  moves further closer to the diaphragm  8  from the position of displacement ⅙ mm to the position of displacement 0 mm. As a result of this movement, the volume of the suction valve chamber is decreased further, so that the transfer of liquid from the suction valve chamber to the metering chamber continues. When the first pressing rod  73  is moved to the position of displacement 0 mm, the diaphragm  8  is brought into the close contact with the first recess  23 A to hermetically seal the suction valve chamber, and the transfer of liquid is stopped to complete the first transfer step. 
   At this time, the ball  79  of the second pressing rod  74  moves from 33° to 45° of the cam face  511  and the second pressing rod  74  moves away from the diaphragm  8  from the position of displacement ⅓ mm to the position of displacement 0.5 mm. As a result of this movement, the suction of liquid from the suction valve chamber into the metering chamber continues until the second pressing rod  74  moves to the position of displacement 0.5 mm and the first transfer step is completed when the second pressing rod  74  reaches the position of 0.5 mm. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 3° to 15° of the cam face  511  but the third pressing rod  75  remains at the position of displacement 0 mm without moving axially. Thus, the discharge valve chamber is held to a hermetically sealed condition so that the suspension of discharge of liquid from the discharge valve chamber to the port  22  is maintained. 
   In this way, the first transfer step is carried out between the state of  FIG. 9C  and that of  FIG. 10D . When the state of  FIGS. 10C ,  10 D arises, both the suction valve chamber and the discharge valve chamber are hermetically sealed and the liquid is held to the metering chamber and hence metered by the volume of the metering chamber so that the metering step is carried out at this time. 
   As the cam  51  is further rotated and the ball  79  of the first pressing rod  73  reaches 90° from 75° of the cam face  511 , the state of  FIGS. 8A ,  8 B is restored. In other words, the first pressing rod  73  remains at the position of displacement 0 mm without moving. Therefore, both the hermetically sealed condition of the suction valve chamber and the suspension of liquid transfer to the metering chamber are maintained 
   At this time, the ball  79  of the second pressing rod  74  moves from 45° to 60° of the cam face  511  and the second pressing rod  74  moves toward the diaphragm  8  from the position of displacement 0.5 mm to the position of displacement 0.25 mm. As a result of this movement, the volume of the metering chamber is gradually decreased, so that liquid is transferred from the metering chamber to the discharge valve chamber. 
   On the other hand, the ball  79  of the third pressing rod  75  moves from 15° to 30° of the cam face  511  and the third pressing rod  75  moves away from the diaphragm  8  from the position of displacement 0 mm to the position of displacement 0.25 mm. As a result of this movement, the volume of the discharge valve chamber is gradually increased, so that the liquid transferred from the metering chamber is sucked into the discharge valve chamber. In this way, the second transfer step is carried out between the state of  FIG. 10D  and that of  FIG. 8C . 
   The shapes of the cam face  511  from 90° to 180°, from 180° to 270° and from 270° to 360° are identical with the shape of from 0° to 90°. In other words, the state where the ball  79  of the first pressing rod  73  is at 90° of the cam face  511  is identical with the state illustrated in  FIGS. 8A ,  8 B and hence the above-described operation is repeated from that state. Therefore, the description will be omitted. 
     FIG. 11  is a graph illustrating the change of displacement relative to the rotation angle of each of the pressing rods  73  through  75 . 
   Note that in  FIG. 11 , the above-described range of 90° from 15° to 105° is shown as a range of 90° from 0° to 90° for convenience of description. Additionally, in  FIG. 11 , the first pressing rod  73  disposed on the outer circumferential side of the recess forming surface  21  is referred to as “EXTERNAL”, the third pressing rod  75  disposed on the inner circumferential side is referred to as “INTERNAL” and the second pressing rod  74  disposed between the pressing rods  74 ,  75  is referred to as “INTERMEDIATE”. 
   As shown in  FIG. 11 , the first pressing rod  73  moves away from the diaphragm  8  between 0° and 12° (between 15° and 27° in the above description) at a constant acceleration. The change per unit angle (e.g., 1°) of displacement during this period is so defined as to gradually increase. 
   Subsequently, the first pressing rod  73  moves away from the diaphragm  8  between 12° and 18° (between 27° and 33° in the above description) at a constant speed. The change per unit angle of displacement during this period is so defined as to be constant. 
   Then, the first pressing rod  73  moves away from the diaphragm  8  between 18° and 30° (between 33° and 45° in the above description) at a constant acceleration. The change per unit angle of displacement during this period is so defined as gradually decrease. 
   Then, the first pressing rod  73  moves toward the diaphragm  8  between 30° and 42° (between 45° and 57° in the above description) at a constant acceleration. The change per unit angle of displacement during this period is so defined as to gradually increase. 
   Then, the first pressing rod  73  moves toward the diaphragm  8  between 42° and 48° (between 57° and 63° in the above description) at a constant speed. The change per unit angle of displacement during this period is so defined as to be constant. 
   Then, the first pressing rod  73  moves toward the diaphragm  8  between 48° and 60° (between 63° and 75° in the above description) at a constant acceleration. The change per unit angle of displacement during this period is so defined as to gradually decrease. 
   Then, the first pressing rod  73  is at halt with displacement 0 between 60° and 90° (between 75° and 105° in the above description). 
   On the other hand, the second pressing rod  74  moves in the same manner with a delay of 30° relative to the first pressing rod  73 . In other words, the second pressing rod  74  is at halt between 0° and 30° but moves between 30° and 90° just like the first pressing rod  73  between 0° and 60°. 
   Similarly, the third pressing rod  75  moves in the same manner with a delay of 30° relative to the second pressing rod  74  (and with a delay of 60° relative to the first pressing rod  73 ). In other words, the third pressing rod  75  is at halt between 30° and 60° but moves between 60° and 30° just like the first pressing rod  73  between 0° and 60°. 
   While the pressing rods operate in the above-described manner, liquid is discharged into the port  22  during the period where the third pressing rod  75  moves from the position of displacement 0.5 mm to the position of displacement 0 mm (between 0° and 30° in  FIG. 11 ). 
     FIG. 12  is a graph illustrating the change in the liquid discharge rate from each of the discharge valve chambers (third recesses  25 A through  25 E) during the period where the cam  51  is rotated by 90°. In  FIG. 12 , the liquid discharge rates from the discharge valve chambers (third recesses  25 A through  25 E) are denoted respectively by numbers  1  through  5 . 
   Between 0° and 12°, the third pressing rod  75  that corresponds to the third recess  25 A moves at a constant acceleration so as to gradually increase the displacement amount per unit angle. Therefore, the liquid discharge rate also gradually increases as shown in  FIG. 12 . Thus, a discharge rate increasing step is carried out. 
   Between 12° and 18°, since the third pressing rod  75  moves while maintaining the displacement amount per unit angle at a constant value, discharge rate of the liquid is also constant. Thus, a constant discharge rate step is carried out. 
   Between 18° and 30°, the third pressing rod  75  moves at a constant acceleration so as to gradually decrease the displace amount per unit angle. Therefore, the liquid discharge rate also gradually decreases. Thus, a discharge rate decreasing step is carried out. 
   On the other hand, as shown in  FIG. 12 , liquid is discharged from the discharge valve chamber (third recess  25 B) between 18° and 48° as in the case of the third recess  25 A because the third pressing rods  75  are angularly displaced from each other by 72° and the cam face  511  of the cam  51  cyclically changes at every 90°. The cam face  511  are defined in such a way that, while the liquid discharge rate of the third recess  25 A gradually decreases (discharge rate decreasing step), the liquid discharge rate of the third recess  25 B gradually increases (discharge rate increasing step) so that the sum of the discharge rates is kept at a constant level. The sum of the discharge rate is so selected as to be equal to the discharge rate that is observed when the third pressing rod  75  is moving at a constant speed (for example, the discharge rate of the third recess  25 A between 12° and 18°). 
   Since the other discharge valve chambers (the third recesses  25 C through  25 E) operate to discharge liquid with the same mutual phase difference of 18°, the liquid is discharged from the diaphragm pump  1  at a constant rate. 
   Since the diaphragm pump  1  has five liquid flow paths  280  that operate as pumps and the cam face  511  is adapted to make a single cycle of reciprocation during the time it rotates by 90°, which is equal to that a total of 20 pumps operates when the cam  51  makes a full turn. During this time period, a predetermined volume of liquid is continuously discharged and sucked. In other words, the liquid is sucked and discharged continuously without pulsation. 
   Since a constant volume is always discharged for a full turn of the cam  51 , the volume of the liquid to be discharged per unit time can be controlled by adjusting the rotation speed of the cam  51 . 
   The above-described embodiment provides the following advantages. 
   (1) The plurality of recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E are formed on the recess forming surface  21  and the diaphragm  8  is arranged to cover the recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E, while the plurality of pressing rods  73 ,  74 ,  75  are arranged to correspond to the respective recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E so as to produce five pumps, and the operations of the pressing rods  73  through  75  are defined by way of a cam  51 . Thus, liquid can be sucked and discharged, or transferred, at a constant rate in response to the rotation of the cam  51 , so that the liquid can be transferred continuously without pulsation by rotating of the drive unit  6  at a constant speed. 
   Particularly, since a metering step where the suction valve chamber and the discharge valve chambers are hermetically sealed and the liquid is dividedly isolated in the metering chamber, it is possible to accurately transfer even a very small amount of liquid. 
   Additionally, since the rate at which the liquid is transferred per unit time by the diaphragm pump  1  can be adjusted only by adjusting the rotation speed of the drive unit  6 , the operation of the diaphragm pump can be controlled very easily. 
   (2) Since a pulsation-free continuous pump can be formed by using a diaphragm  8 , the limitation to the types of liquid that can be discharged from the pump is minimized and hence the diaphragm pump can be widely used in various applications. In other words, since only the base block  2 , the holder ring block  3  and the diaphragm  8  contact liquid, liquid of various different types can be transferred when appropriate materials are selected for those components. Additionally, since the diaphragm  8  is made of an elastically deformable material such as rubber, liquid such as silver paste or solder paste can be discharged without crushing particles contained therein so that liquid can be transferred without being damaged. 
   As in the case with a plunger pump or the like, when a seal member is applied to the plunger to prevent leakage of liquid, the plunger is forced to slide on the seal member so that friction occurs between liquid and the plunger and the seal member. Then, if a liquid that can be easily polymerized as a result of friction with the seal member such as an ultraviolet curing adhesive or an aerophobic adhesive is transferred, the liquid can often be damaged as it is partly polymerized and set. To the contrary, the present embodiment employs a diaphragm  8  and hence eliminates the use of a seal member, which eliminates portions of liquid subjected to friction. Therefore, liquid such as the ultraviolet curing adhesive or the aerophobic adhesive can be transferred without any damage. 
   Therefore, the diaphragm pump  1  can transfer liquid of various different types, which can be used in various industrial fields including the chemical industry, the semiconductor industry and the printing industry. 
   (3) Since at least one of the respective suction valve chambers and the metering chamber of the respective liquid flow paths  280  is hermetically sealed as the diaphragm  8  closely contacts to the recesses  23  through  25 , the liquid is prevented from flowing back even without a check valve. Therefore, the liquid can be transferred from the port  22  to the space  33  at the outer circumferential side of the recess forming surface  21  by rotating the cam  51  in the opposite direction. In short, according to the present invention, the diaphragm pump  1  that allows liquid to flow back can be formed without difficulty. 
   Additionally, if a check valve is provided, the liquid can leak out from the check valve when the liquid supply side and the liquid discharge side of the check valve have a pressure difference so that it is not possible to apply pressure to the liquid supply side in order to pressure-feed the liquid. To the contrary, with the present embodiment, since the recesses  23  through  25  are hermetically sealed without necessity of the use of a check value the embodiment operates properly even in a condition having pressure difference, where the pressure is applied to the liquid supply side and/or the liquid discharge side is under negative pressure. In other words, the liquid can be supplied by applying pressure thereto and transferred while filing up the liquid flow paths  280  with the liquid without any space, so that the accuracy of the liquid discharge rate can be improved. Additionally, highly viscous liquid can also be transferred, further increasing types of liquid that can be transferred. In other words, the present embodiment can be used as a dispenser for a variety of liquids. 
   (4) The drive side including the pressing rods  73  through  75 , the cam  51  and the like and the pump side for transferring the liquid are separated by the diaphragm  8  so that it is not necessary to additionally provide a seal member that prevents liquid from leaking to the drive side. Additionally, the pressing rods  73  through  75  are only required to simply reciprocate with a stroke of 0.5 mm so that the overall arrangement of the embodiment can be simplified and downsized. Therefore, it is possible to provide a small diaphragm pump  1  that can discharge a very small quantity of liquid. Then, it can be attached to a robot arm on a semiconductor manufacture line. 
   (5) The recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E and the pressing rods  73  through  75  are arranged to extend spirally from the port  22 , so that the area of the recess forming surface  21  can be made compact. Then, the diaphragm pump  1  can be downsized. 
   (6) The first pressing rods  73 , the second pressing rods  74  and the third pressing rods  75  needs to be operated with phase differences. Such phase differences can be realized by shifting the areas that correspond to the respective pressing rods  73  through  75  on the cam face  511 . However, such an arrangement makes the cam manufacturing process a cumbersome one. To the contrary, with the present embodiment, the first recesses  23 A through  23 E, the second recesses  24 A through  24 E and the third recesses  25 A through  25 E are shifted from each other by 30° around the port  22  in the rotation direction. With this arrangement, it is not necessary to shift the areas that correspond to the respective pressing rods  73  through  75  on the cam face  511  of the cam  51  and the cam face  511  can be formed linearly, which facilitates manufacturing of the cam  51 . 
   (7) A single diaphragm  8  that covers the recess forming surface  21  is required, so that the diaphragm  8  can manufactured easily at low cast In conventional diaphragm pumps, the entire diaphragm  8  is reciprocated in order to discharge liquid, so that discharge errors may occur because the diaphragm  8  is deformed. Then, it is difficult to accurately transfer a very small quantity of liquid. 
   To the contrary, in the present embodiment, not the entire diaphragm  8  is reciprocated but only the portions of the diaphragm  8  that correspond respectively to the first recesses  23 A through  23 E, the second recesses  24 A through  24 E and the third recesses  25 A through  25 E (recess-corresponding portions) are reciprocated so that the diaphragm  8  can be moved with high accuracy by following the respective motions of the pressing rods  73  through  75 . Additionally, since the liquid is transferred by moving small portions of the diaphragm  8  that correspond to the respective recesses  23  through  25 , transfer rate can also be small. In other words, it is possible to realize a pump that can transfer a very small amount of liquid, which can be utilized as a device for discharging a very small amount of liquid (dispensers). 
   Additionally, the diaphragm  8  can be manufactured at low cost because both the flow-path-block contacting surface and the pressing-rod-abutting surface have a simple planar profile. In other words, when the diaphragm  8  is worn, it can be replaced at low cost. 
   (8) Since the cam followers that abut the cam face  511  include the pressing rods  73  through  75  and the balls  79  held respectively by the pressing rods  73  through  75  in the present embodiment, it is possible to downsize the drive section of the embodiment that is formed by the cam face  511  and the cam followers. If rollers are used instead of the balls  79 , rotary shafts need to be provided so as to project in a radial direction in order to rotatably support the rollers. Then, the diameters of tracks of the rollers moving (rotating) along the cam become large. To the contrary, since the balls  79  are used in the present embodiment, no roller shafts are needed and hence the diameters of the tracks of the rollers can be small accordingly. Thus, the diaphragm pump  1  can be downsized. 
   (9) When the rollers are used, the planar cam has to be made of oil-impregnated resin in order to reduce worn because side slips may occur between the planar cam and the rollers. Then, the oil-impregnated resin of the planar cam is deformed when it is pressed against the rollers, which generates an error in the stroke of the plunger and consequently reduces the discharge accuracy of the liquid. 
   To the contrary, in the present embodiment, the balls  79  are abuts on the cam faces  511  and the coefficient of friction between the pressing rods  73  through  75  and the balls  79  is set to lower than the coefficient of friction between the cam faces  511  and the balls  79 . Therefore, if radial force is applied to the rotating balls  79 , the force is absorbed as the balls  79  slide on the respective pressing rods  73  through  75 . Thus, no side slip occurs between the cam faces  511  and the balls  79 , and the balls  79  can rotate and move without slipping on the cam faces  511 . Therefore, it is no longer necessary to consider friction and use oil-impregnated resin for the cam faces  511 , and the cam  51  can be made of a hard material such as metal and the balls  79  can also be made of a hard material, which can reduce the error in the stroke of the pressing rods  73  through  75  and improve the accuracy of liquid discharge. 
   Additionally, since the reciprocating motions of the pressing rods  73  through  75  are unequivocally defined by the profile of the cam faces  511 , it is possible to accurately control the motions of the pressing rods  73  through  75  by appropriately setting the profile of the cam faces  511 . Thus, accurate discharge liquid can be realized without pulsation. 
   (10) Still additionally, while the pressing rods  73  through  75  are made of a resin material that is softer than the material of the balls  79 , each of the balls  79  is held in the semispherical recess that is adapted to house about a half of the ball  79 . Therefore, if the ball  79  slides in the recess, the force generated by the slide can be absorbed by the large area of the recess. Thus, the pressing rods  73  through  75  are prevented from being deformed. 
   As a result, no error occurs in the movements of the pressing rods  73  through  75  so that the pressing rods  73  through  75  can be accurately controlled for their movements and hence it is possible for the embodiment to accurately transfer a very small amount of liquid. 
   (11) The coil springs  78  are provided to bias the respective pressing rods  73  through  75  toward the cam faces  511  so that the pressing rods  73  through  75  reliably follow the cam faces  511 . Additionally, since the entire cam  51  is biased toward the diaphragm  8  by the coned disk spring  57 , the positions of displacement 0 of the pressing rods  73  through  75 , where they press the diaphragm  8  against the respective recesses  23  through  25 , can be automatically aligned to a certain extent. In other words, as the pressing rods  73  through  75  are pressed against the diaphragm  8  by a certain force, the diaphragm  8  closely contacts to the recesses  23  through  25  and the positions of the pressing rods  73  through  75  are determined when the diaphragm  8  is compressed to a certain extent and the repulsive force of the diaphragm  8  is balanced with the force being applied to the pressing rods  73  through  75 . Therefore, when the cam  51  is placed approximately at the designed position by referring to the height or the like of the spacer ring  56 , the positions of the pressing rods  73  through  75  and hence the position of the cam  51  are automatically adjusted as the cam  51  is pressed against the diaphragm  8  by the coned disk spring  57 . Thus, the cam  51  is accurately placed in a position when the diaphragm pump  1  is assembled without requiring accurate machining for the related components. In other words, the efficiency of machining the components can be improved to relatively reduce the manufacturing cost of the diaphragm pump. 
   (12) Only by rotating the cam  51  with the drive unit  6  as a rotary drive source, each of the pressing rods  73  through  75  can reciprocate by following the cam face. The pressing member drive controller can be formed in compact size, realizing the diaphragm pump  1  with reduced size and weight. Thus, when used in dispensing adhesives, various pastes and the like in production lines of various products, the diaphragm pump  1  can be attached to robot arms and moved by high speed and high acceleration, so that the takt time of the production lines can be shortened, which enhances productivity. 
   (13) In the present invention, only by rotating the cam  51  by the drive unit  6  including a motor and the like, each of the pressing rods  73  through  75  can be repeatedly operated with a predetermined timing. Since the liquid transfer rate can be set to constant for each one cycle of operation for each of the pressing rods  73  through  75 , the liquid transfer rate per unit of time can be adjusted only by adjusting rotation speed of the cam  51 . 
   Thus, the liquid transfer rate of the diaphragm pump  1  can be controlled easily, so that the diaphragm pump  1  (dispenser) with high convenience can be realized. 
   Second Embodiment 
   Next, the second embodiment of the present invention will be described by referring to  FIGS. 13 and 14A  through  14 C. 
   A diaphragm pump  1 A of the second embodiment differs from the diaphragm pump  1  of the first embodiment in arrangements of a base block  2 A and a diaphragm  8 A. More specifically, of the base block  2 A of the second embodiment, a diaphragm-contacting surface  21 A that closely contacts to the diaphragm  8 A is planar without grooves and recesses formed thereon, which is different from the recess forming surface  21  of the first embodiment where the recesses  23  through  25  and the communication grooves  281  through  284  are formed. 
   The diaphragm  8 A shows a substantially disk-like profile, which include a flow-path-block-contacting surface  81  that faces the base block  2 A and a pressing-rod-abutting surface  82  that faces the pressing rods  73  through  75 . 
   The flow-path-block-contacting surface  81  is not planar unlike the diaphragm  8  of the first embodiment, and the recesses  23  through  25  and the communication grooves  281  through  284  are formed thereon, as shown in  FIGS. 14B and 14C . In other words, like the recess forming surface  21  of the first embodiment, the recesses  23  through  25  and the communication grooves  281  through  284  are formed on the flow-path-block-contacting surface  81 . 
   On the other hand, as shown in  FIG. 14A , spherical projections  83  through  85  are formed on the pressing-rod-abutting surface  82  at positions corresponding to the respective recesses  23  through  25 . With this arrangement, the portions where the recesses  23  through  25  are formed have substantially the same thickness as the thickness of the remaining portions as shown in  FIG. 14B . The diaphragm  8 A is made of rubber and can be molded by means of a rubber die (rubber molding metal mold). 
   As shown in  FIG. 13 , the diaphragm  8 A is pinched between a flow path block that is formed by the base block  2 A and a holder ring block  3  and a guide block  4 . The projections  83  through  85  are arranged at the positions corresponding to respective guide holes  43  through  45  of the guide block  4  and adapted to abut respective pressing rods  73  through  75 . 
   Thus, the suction valve chamber, the metering chamber and the discharge valve chamber are formed by the spaces defined respectively by the recesses  23  through  25  of the diaphragm  8 A and the diaphragm-contacting surface  21 A of the base block  2 A. Additionally, communication paths are formed by the spaces defined respectively by the communication grooves  281  through  284  and the diaphragm-contacting surface  21 A. 
   The end surface of each of the pressing rods  73  through  75  on a side of the diaphragm  8 A is formed in a planar profile, into which each of the projections  83  through  85  can be pressed efficiently, although pressing rods  73  through  75  having a semispherical profile like those of the first embodiment may alternatively be used. 
   Thus, the present embodiment is identical with the first embodiment in terms of that it is provided with the respective valve chambers, the metering chamber and the communication paths between the diaphragm  8 A and the base block  2 A and the volume of each of the valve chambers and the metering chamber changes in accordance with reciprocation of the pressing rods  73  through  75 . Therefore, the liquid is transferred by the present embodiment just like the first embodiment. 
   The present embodiment provides the following advantages in addition to the advantages of the first embodiment. 
   Since the recesses  23  through  25  and the communication grooves  281  through  284  are not formed in the base block  2 A but in the diaphragm  8 A, the cost of initial investment can be reduced further, so that the manufacturing cost can be lowered when the manufacturing number of the diaphragm pumps  1 A is relatively small and a very small volume of liquid can be transferred with ease. More specifically, the metal base block  2  having recesses  23  through  25  of the first embodiment is formed by using a metal mold or by using machine tools. If a metal mold is used, the manufacturing cost of the base block  2  is reduced but the cost of preparing the metal mold is high, and thus the cost of initial investment is raised. If, on the other hand, machine tools are used, the machining cost is high and it is difficult to reduce the volumes of the recesses  23  through  25  for machining reasons. 
   To the contrary, when the recesses  23  through  25  and the communication grooves  281  through  284  are formed in the diaphragm  8 A, the rubber diaphragm  8 A is molded by using a rubber die. Such a rubber die is less expensive if compared with a metal mold for forming metal products so that by turn the cost of initial investment is reduced. Additionally, the metering chambers and the flow paths can be dimensionally reduced when a rubber die is used. Then, the manufactured diaphragm pump is adapted to transfer a very small amount of liquid without difficulty. 
   Third Embodiment 
   Next, a third embodiment of the present invention will be described with reference to  FIGS. 15 through 24 . 
   A diaphragm pump  1 B of the third embodiment differs from the diaphragm pump  1  of the first embodiment in arrangements of a flow path block  130  and a cam  150 . The flow path block  130  includes a metal base  131  and an abutment  132  made of synthetic resin such as polypropylene. 
   The abutment  132  includes a recess forming surface  132 A as a diaphragm-contacting surface for the diaphragm  8  to be closely attached thereto. Formed on the recess forming surface  132 A are the recesses  23  through  25  and communication grooves  281  through  284 , as with the recess forming surface  21  of the first embodiment shown in  FIG. 2 . 
   A plurality of protrusions  132 B are formed on the abutment  132 , the protrusions  132 B inserted into a fitting hole  131 A of the base  131  for positioning. 
   A through hole being the port  22  is formed at a central axis portion of the abutment  132 . A nozzle connector  133  is pressed into the port  22  made of stainless steel or the like. 
   The nozzle connector  133  is fixed to the flow path block  130  by the nozzle member  27  that is screwed on the flow path block  130 . Since the nozzle connector  133  is pressed into the port  22  of the abutment  132  the abutment  132  is fixed to the base  131  in a closely contacted manner. 
   An O-ring for preventing leakage is provided between the nozzle connector  133  and the abutment  132 . 
   The liquid discharged from the port  22  of the abutment  132  as a discharge flow path is then discharged to the outside of the pump via the nozzle connector  133  and the nozzle member  27 . 
   A connector  160  is fixed to the flow path block  130  with a cap nut, to which a tube for supplying the liquid and a container is attached. The flow path block  130  is provided with the through hole  32  intercommunicating with a liquid supply path  161  of the connector  160  and the ring-shaped space  33  intercommunicating with the through hole  32  and formed along the outer periphery of the diaphragm  8 . 
   A communication groove  281  formed by a notched groove for intercommunicating the space  33  and the recess  23  is formed on the outer periphery side of the abutment  132 , and the suction flow path is formed by the space  33  in the present embodiment. 
   The diaphragm  8  is held between the base  131  and a case block  10 . A through hole is formed at a central axis portion of the case block  10 , and the guide block  4  is held in the through hole. Since the arrangement of the guide block  4  is the same as the one in the first embodiment, description thereof will be omitted. 
   Incidentally, the guide block  4  is biased by a coned disk spring  11  toward the flow path block  130  via a cylindrical pressing member  12  located in the inner through hole of the fitting block  5 , so that the guide block  4  abuts on the diaphragm  8  with a predetermined pressure. 
   The spline shaft  53  is fixed to the output shaft  61  of the drive unit  6 , and the spline boss  52  is engaged with the spline shaft  53 . The spline boss  52  is rotatably supported relative to the pressing member  12  via the boll bearing  55 . The spline boss  52  is pressed into the cam  150  so as to rotate in conjunction with the cam  150 . 
   The cam  150  is biased by the coned disk spring  57  toward the guide block  4  via the spline boss  52  and the ball bearing  55 . 
   On the other hand, the pressing rods  73  through  75  guided by the guide block  4  are biased toward the cam  150  by the coil spring  78 . Thus, the ball  79  functioning as the cam follower disposed on the pressing rods  73  through  75  constantly abuts on the cam face of the cam  150  with a predetermined pressure. 
   As shown in  FIGS. 16A and 16B , three cam grooves  151  through  153  are substantially concentrically formed around the central axis on the end surface  150 A orthogonal to the rotary shaft of the cam  150   
   The first cam groove  151  is a cam groove for guiding the ball  79  of the first pressing rod  73 , which is formed on an outermost circumferential side of the cam  150  as shown in  FIG. 17A . 
   The second cam groove  152  is a cam groove for guiding the ball  79  of the second pressing rod  74 , which is formed on an inner circumferential side of the cam groove  151  as shown in  FIG. 17B . 
   The third cam groove  153  is a cam groove for guiding the ball  79  of the third pressing rod  75 , which is formed on an inner circumferential side of the cam groove  152  (i.e. innermost circumferential side of the cam  150 ) as shown in  FIG. 17C . 
   Cam diagrams of the respective cam grooves  151  through  153  are shown in  FIGS. 18 through 20 . The y-axis of the cam diagram shows bottom side portions on which the ball  79  abuts in the cam grooves  151  through  153 , in other words, height position (depth) of the cam face, when the flat portion of the end surface of the cam  150  is defined as y=0, where a portion closest to the diaphragm  8  (shallowest portion in the groove) is defined as the lowest position of the cam (y=0.2) and a portion remotest to the diaphragm  8  (deepest portion in the groove) is defined as the highest positions of the cam (e.g., y=0.7 mm in the present embodiment) in the bottom sides of the cam grooves  151  through  153 . On the other hand, the x-axis, defining a state where the ball  79  of the first pressing rod  73  abuts on the lowest positions of the cam (y=0.2) as 0°, shows a rotation angle of the cam  150  from the aforesaid position, i.e. a relative rotation angle of the cam face relative to the ball  79 . Note that the cam diagram also illustrates loci of movements of the center positions of the balls  79 . 
   In this embodiment, the cam faces of the respective cam grooves  151  through  153  operate with a cycle of 90° and the operation is repeated from 90° to 180°, from 180° to 270° and from 270° to 360°. Therefore, only the cycle from 0° to 90° will be described below. 
   As shown in  FIG. 18 , the cam diagram of the cam groove  151  shows that the cam face remains at the lowest position (y=0.2) when the rotation angle of the cam  150  is between 0° and 30°. In other words, the cam face is formed by a plane orthogonal to the rotary shaft of the cam  150 . 
   When the rotation angle of the cam  150  is between 30° and 39°, the cam face is expressed, for instance, by a quadratic curve of y=(x−30) 2 /810+1/5. 
   When the rotation angle of the cam  150  is between 39° and 48°, the cam face is expressed, for instance, by a straight line of y=x/45−17/30. 
   When the rotation angle of the cam  150  is between 48° and 57°, the cam face is expressed, for instance, by a quadratic curve of y=−(x−52.5) 2 /405+11/20. 
   When the rotation angle of the cam  150  is between 57° and 66°, the cam face is expressed, for instance, by a straight line of y=x/45+53/30. 
   When the rotation angle of the cam  150  is between 66° and 75°, the cam face is expressed, for instance, by a quadratic curve of y=(x−75) 2 /810+1/5. 
   When the rotation angle of the cam  150  is between 75° and 90°, the cam face remains at the lowest position (y=0.2). 
   As shown in  FIG. 19 , the cam diagram of the cam groove  152  shows that the cam face remains at the lowest position (y=0.3) when the rotation angle of the cam  150  is between 0° and 9°. 
   When the rotation angle of the cam  150  is between 9° and 18°, the cam face is expressed, for instance, by a quadratic curve of y=(x−9) 2 /810+3/10. 
   When the rotation angle of the cam  150  is between 18° and 27°, the cam face is expressed, for instance, by a straight line of y=x/45. 
   When the rotation angle of the cam  150  is between 27° and 36°, the cam face is expressed, for instance, by a quadratic curve of y=−(x−36) 2 /810+7/10. 
   When the rotation angle of the cam  150  is between 36° and 54°, the cam face is expressed, for instance, by a straight line of y=0.7. 
   When the rotation angle of the cam  150  is between 54° and 63°, the cam face is expressed, for instance, by a quadratic curve of y=−(x−54) 2 /810+7/10. 
   When the rotation angle of the cam  150  is between 63° and 72°, the cam face is expressed, for instance, by a straight line of y=−x/45+2. 
   When the rotation angle of the cam  150  is between 72° and 81°, the cam face is expressed, for instance, by a quadratic curve of y=(x−81) 2 /810+3/10. 
   When the rotation angle of the cam  150  is between 81° and 90°, the cam face remains at the lowest position (y=0.3). 
   As shown in  FIG. 20 , the cam diagram of the cam groove  153  shows that the cam face remains at the lowest position (y=0.2) when the rotation angle of the cam  150  is between 0° and 15°. 
   When the rotation angle of the cam  150  is between 15° and 24°, the cam face is expressed, for instance, by a quadratic curve of y=(x−15) 2 /810+1/5. 
   When the rotation angle of the cam  150  is between 24° and 33°, the cam face is expressed, for instance, by a straight line of y=x/45−7/30. 
   When the rotation angle of the cam  150  is between 33° and 42°, the cam face is expressed, for instance, by a quadratic curve of y=−(x−37.5) 2 /405+11/20. 
   When the rotation angle of the cam  150  is between 42° and 51°, the cam face is expressed, for instance, by a straight line of y=−x/45+43/30. 
   When the rotation angle of the cam  150  is between 51° and 60°, the cam face is expressed, for instance, by a quadratic curve of y=(x−60) 2 /810+1/5. 
   When the rotation angle of the cam  150  is between 60° and 90°, the cam face is expressed, for instance, by a straight line of y=0.2. 
   Accordingly, when the spline shaft  53 , the spline boss  52  and the cam  150  are rotated by the drive unit  6 , the balls  79  and the pressing rods  73  through  75  advance and retract in axes direction along the shape of the cam faces of the respective cam grooves  151  through  153 . 
   When the pressing rods  73  through  75  moves toward the side of the recesses  23  through  25 , the volumes of the valve chambers and the metering chambers defined by the parts of the diaphragm  8  that correspond to the recesses  23  through  25  (parts of the diaphragm  8  corresponding to the recesses on which the pressing rods  73  through  75  abut) and by the recesses  23  through  25  decrease, volume decrease operation is performed. When the ball  79  abuts on the position of y=0.2 (reference depth), the parts corresponding to the recesses closely contact with inner surfaces of the recesses  23  through  25 , and sealing operations for the respective valve chambers or the like are performed. 
   As the pressing rods  73  through  75  move away from the respective recesses  23  through  25 , the parts of the diaphragm  8  corresponding to the recesses detach from the inner surfaces of the respective recesses  23  through  25 , to which they have been closely contacted, opening operations are performed of the respective valve chambers is performed. When the pressing rods  73  through  75  move away from the recesses  23  through  25 , volume increase operations are performed for the respective valve chambers and metering chambers defined between the recesses  23  through  25  and the diaphragm  8 . 
   Next, advantages of a third embodiment of the present invention will be described with reference to  FIGS. 21 through 24D . 
   [Operation of Pressing Rod] 
   Firstly, the operation of the respective pressing rods  73  through  75  will be described. The pressing rods  73  through  75  operate in correspondence with the profile of the cam respective cam grooves  151  through  153 . At this time, the respective pressing rods  73  through  75  are respectively displaced by a first predefined angle (30°) as in the first embodiment. When the ball  79  of the pressing rod  73  is at 60° position in  FIG. 18 , the ball  79  of the pressing rod  74  is at 30° position in  FIG. 19  and the ball  79  of the pressing rod  75  is at 0° position in  FIG. 20 . 
   A graph of the displacements of the respective pressing rods  73  through  75  is shown in  FIG. 21 . In  FIG. 21 , the displacement of the first pressing rod  73  is indicated as “INLET”, the displacement of the second pressing rod  74  as “METERING”, and the displacement of the third pressing rod  75  as “OUTLET”. 
   [Operation of Respective Pumps (Three Pressing Rods)] 
   Next, operations of the respective pumps included in the diaphragm pump  1  will be described by exemplifying operations of the first pressing rod  73 , the second pressing rod  74  and the third pressing rod  75  inserted into the first guide hole  43 A, the second guide hole  44 A and the third guide hole  45 A. 
   It is to be noted that, in the description below, the cam  150  rotates counterclockwise relative to the recess forming surface  132 A (or clockwise if the cam  150  is viewed from the side of the cam face) and operates so as to suck the liquid from the space  33  at the outer circumferential side of the recess forming surface  21  and discharge the liquid from the central port  22 , as with the first embodiment. 
     FIGS. 22A ,  22 B show a state where the ball  79  of the first pressing rod  73  is at 0° position of the cam face. At this time, since the second pressing rod  74  is located behind the first pressing rod  73  by 30°, the ball  79  is at 330° position of the cam face. Since the third pressing rod  75  is located behind the second pressing rod  74  by 30°, the ball  79  is at 300° position of the cam face. 
   Thus, the first pressing rod  73  is at the position of displacement y=0.2, where it presses the diaphragm  8  against the recess  23 A in a closely-contacted manner, and hence the suction valve chamber defined by the first recess  23 A and the part of the diaphragm  8  corresponding to the recess  23 A is held to a hermetically sealed condition. The second pressing rod  74  is moved to a position of displacement 0.6556. The third pressing rod  75  is moved to a position of displacement 0.4333. Since the pressing rods  74 ,  75  are located respectively at the positions described above, the volume of metering chamber defined by the second recess  24 A and the part of the diaphragm  8  corresponding to the recess  24 A and the volume of the discharge valve chamber defined by the third recess  25 A and the part of the diaphragm  8  corresponding to the recess  25 A reflect the respective positions of the pressing rods  74 ,  75 . The metering chamber and the suction valve chamber are communicated with the port  22  via the communication grooves  283  and  284 . 
   As the cam  150  is rotated by 21° from the state of  FIGS. 22A ,  22 B, a state as shown in  FIGS. 22C ,  22 D arises. More specifically, the ball  79  of the first pressing rod  73  reaches 21° position of the cam face, but since the cam face is a plane, the first pressing rod  73  is not displaced and keeps the suction valve chamber in a hermetically sealed condition. 
   At this time, the ball  79  of the second pressing rod  74  moves from 330° to 351° of the cam face and the second pressing rod  74  moves from the position of displacement 0.6556 mm to the position of displacement 0.3 mm to come closer to the diaphragm  8 . As a result of this movement, the volume of the metering chamber is gradually decreased, so that the liquid in the metering chamber is transferred to the discharge valve chamber via the communication groove  283 . 
   Similarly, the ball  79  of the third pressing rod  75  moves from 300° to 321° of the cam face and the third pressing rod  75  moves from the position of displacement 0.4333 mm to the position of displacement 0.55 mm to be away from the diaphragm  8  and further moves to the position of displacement 0.3 mm back to the diaphragm  8 . As a result, the volume of the discharge valve chamber is once increased to suck the liquid from the metering chamber. Then, since the volume of the discharge valve chamber is gradually decreased, the liquid is discharged from the discharge valve chamber to the port  22 . Incidentally, when the volume of the discharge valve chamber is decreased, the volume of the metering chamber is also gradually decreased so as to be constantly smaller than the volume of the discharge valve chamber while the suction valve chamber kept in closed condition, so that, when the volume of the discharge valve chamber is decreased, the liquid is gradually discharged to the port  22  without flowing back to the metering chamber. 
   As the cam  150  is rotated by 9° from the state of  FIGS. 22C ,  22 D, a state of  FIGS. 23A ,  23 B arises. More specifically, the ball  79  of the first pressing rod  73  moves from 21° to 30° of the cam face. The first pressing rod  73  is kept at the displacement 0.2 mm until 30° while the suction valve chamber is maintained in the hermetically sealed condition. 
   More specifically, the ball  79  of the second pressing rod  74  moves from 351° to 360° of the cam face. At this time, the second pressing rod  74  is kept at the displacement 0.3 mm. In the displacement of 0.3 mm, the diaphragm  8  does not closely contact the second recess  24 A and a gap is formed therebetween, so that the metering chamber is maintained at a predefined volume. 
   At this time, the ball  79  of the third pressing rod  75  moves from 321° to 330° of the cam face and the third pressing rod  75  moves from the position of displacement 0.3 mm to the position of displacement 0.2 mm to come closer to the diaphragm  8 . As a result of the movement, the discharge valve chamber is hermetically sealed. 
   Thus, since the liquid is gradually discharged from the port  22  from a state of  FIGS. 22A ,  22 B to a state of  FIGS. 23A ,  23 B, the discharge step is performed. In the state of  FIG. 23 , since the discharge valve chamber is sealed, the discharge step ends. 
   As the cam  150  is rotated by 9° from the state of  FIGS. 23A ,  23 B, a state as shown in  FIGS. 23C ,  23 D arises. More specifically, the ball  79  of the first pressing rod  73  moves from 30° to 39° of the cam face. The first pressing rod  73  moves from position of displacement 0.2 mm to 0.3 mm to be away from the diaphragm  8 , the volume of the suction valve chamber is increased. In accordance with the increase in the volume, the liquid is sucked from the space  33  to the suction valve chamber via the communication groove  281 . 
   At this time, the ball  79  of the second pressing rod  74  moves from 360° to 9° of the cam face and the second pressing rod  74  is maintained at the position of displacement 0.3 mm. Accordingly, the metering chamber is maintained with a predefined volume. 
   At this time, the ball  79  of the third pressing rod  75  moves from 330° to 339° of the cam face and the third pressing rod  75  is maintained at the position of displacement 0.2 mm. As a result of the movement, the discharge valve chamber is maintained in the hermetically sealed condition. 
   As the cam  150  is rotated by 27° from the state of  FIGS. 23C ,  23 D, a state as shown in  FIGS. 24A ,  24 B arises. More specifically, the ball  79  of the first pressing rod  73  moves from 39° to 66° of the cam face. At this time, when the first pressing rod  73  once moves from the position of displacement 0.3 mm to the position of displacement 0.5 mm (52.5°) to be away from the diaphragm  8 , and again moves back to the position of displacement 0.3 mm so as to come closer to the diaphragm  8 . 
   At this time, the ball  79  of the second pressing rod  74  moves from 9° to 36° of the cam face and the second pressing rod  74  moves from the position of displacement 0.3 mm to the position of displacement 0.7 mm to come closer to the diaphragm  8 . As a result of the movement, the volume of the metering chamber is gradually increased. 
   The volume of the suction valve chamber once increases and then decreases. Thus, the liquid is sucked from the space  33  into the suction valve chamber, and then discharged from the suction valve chamber. At this time, since the volume of the metering chamber is gradually increased, the liquid discharged from the suction valve chamber is sucked into the metering chamber. 
   At this time, the ball  79  of the third pressing rod  75  moves from 339° to 6° of the cam face and the third pressing rod  75  is maintained at the position of displacement 0.2 mm. Thus, the discharge valve chamber is maintained in the hermetically sealed condition. 
   As the cam  150  is rotated by 9° from the state of  FIGS. 24A ,  24 B, a state as shown in  FIGS. 24C ,  24 D arises. More specifically, the ball  79  of the first pressing rod  73  moves from 66° to 75° of the cam face. At this time, since the first pressing rod  73  is moved from the position of displacement 0.3 mm to the position of displacement 0.2 mm to come closer to the diaphragm  8 , the suction valve chamber is hermetically sealed. 
   At this time, the ball  79  of the second pressing rod  74  moves from 36° to 45° of the cam face and the second pressing rod  74  is maintained at the position of displacement 0.7 mm. Thus, the volume of the metering chamber does not change. 
   At this time, the ball  79  of the third pressing rod  75  moves from 6° to 15° of the cam face and the third pressing rod  75  is maintained at the position of displacement 0.2 mm. Thus, the discharge valve chamber is maintained in the hermetically sealed condition. 
   Therefore, as the ball  79  of the first pressing rod  73  moves form the state of  FIGS. 23A ,  23 B to the state of  24 D, in other words, from 30° to 75° of the cam face, the volume of the suction valve chamber is gradually increased from the hermetically sealed condition and then deceased, where the suction process for sucking the liquid is performed until the suction valve chamber is hermetically sealed again. 
   In the state of  FIGS. 24C ,  24 D, in other words, when the suction valve chamber is sealed, the suction process ends. 
   Further in the state of  FIGS. 24C ,  24 D, since the suction valve chamber and the discharge valve chamber are hermetically sealed, the liquid is dividedly isolated in the suction valve chamber and the discharge valve chamber, more specifically, in the spaces with predefined volume of the metering chamber and the communication grooves  282 ,  283 . Thus, the metering process for dividedly isolating the liquid in the spaces with predefined volume for metering is performed. 
   As the cam  150  is rotated by 15° from the state of  FIGS. 24C ,  24 D, a state is returned to the state of  FIGS. 22A ,  22 B. More specifically, the ball  79  of the first pressing rod  73  moves from 75° to 90° of the cam face. The first pressing rod  73  is kept at the displacement 0.2 mm while the suction valve chamber is maintained in the hermetically sealed condition. 
   At this time, the ball  79  of the second pressing rod  74  moves from 45° to 60° of the cam face and the second pressing rod  74  is moved from the position of displacement 0.7 mm to the position of displacement 0.6556 mm. Thus, the volume of the metering chamber is gradually decreased. 
   At this time, the ball  79  of the third pressing rod  75  moves from 15° to 30° of the cam face and the second pressing rod  75  is moved from the position of displacement 0.2 mm to the position of displacement 0.4333 mm. Thus, the suction valve chamber is in the opened condition and the volume thereof is gradually increased, so that the liquid is sucked from the metering chamber into the discharge valve chamber. 
   Shapes of 90° through 180°, 180° through 270° and 270° through 360° of the cam face are the same as the shape of 0° through 90°. In other words, the state where the ball  79  of the first pressing rod  73  is at 90° position of the cam face is the same as the state of  FIGS. 22A ,  22 B, the operation is repeated. Therefore, the description thereof will be omitted. 
   In the present embodiment, as with the first embodiment, since the liquid is discharged from the discharge valve chamber (third recess  25 B) because the third pressing rods  75  are angularly displaced from each other by 72° and the cam faces of the cam  150  cyclically change at every 90°, liquid discharge is operated with the mutual phase difference of 18°. Thus, the liquid is discharged from the diaphragm pump  1 B at a constant rate. 
   Since the diaphragm pump  1 B has five liquid flow paths  280  that operate as pumps and the cam face is adapted to make a single cycle of back and forth movement during the time it rotates by 90°, which is equal to that a total of 20 pumps operate when the cam  150  makes a full turn. During this time period, a predefined volume of liquid is continuously discharged and sucked, and liquid is sucked and discharged continuously with little pulsation. 
   Since a discharge volume is also constant for every full turn of the cam  150  in the diaphragm pump  1 B, the volume of liquid to be discharged per unit time can be controlled by adjusting the rotation speed of the cam  150 . 
   The present embodiment is the same as the first embodiment in points that: the respective valve chambers, the metering chamber and communication groove are formed between the diaphragm  8  and the abutment  132 ; and the volumes of the respective valve chambers and metering chambers change in accordance with advancement and retraction of the pressing rods  73  through  75 , transfer operation of the liquid is performed by the operation same as that in the first embodiment. 
   The present embodiment provides the following advantages, in addition to the same functions and advantages of the first embodiment. 
   In other words, since the flow path block  130  includes the base  131  and the abutment  132 , the abutment  132  made of synthetic resin such as polypropylene and provided with the recesses  25  through  25  and the communication grooves  281  through  284 . Thus, the abutment  132  can be made of resin molding, so that production cost can be reduced as compared with the case in which the recesses and the communication grooves are formed on a metal block. 
   Even when the second pressing rod  74  comes closest to the flow path block  130 , the diaphragm  8  is not closely contacted to the second recess  24 , so that abrasion or the like of the diaphragm  8  and the abutment  132  can be reduced, extending life of the diaphragm pump  1 B. 
   Further, since one of the respective valve chambers is always hermetically sealed condition, while the metering chamber is not sealed, direct communication between the suction flow path and the discharge flow path can be securely prevented, so that the function as a pump (dispenser) can be securely maintained. 
   Since the ball  79  is used as a cam follower, the cam grooves  151  through  153  of the cam  150  can be round grooves with the bottom side thereof being rounded, and thus can be processed with a ball end mill. Therefore, production cost of the cam  150  can also be reduced, enabling production of the diaphragm pump  1 B at low cost. 
   Incidentally, the scope of the present invention is not restricted to the above-described embodiments, but includes modifications and improvements as long as an object of the present invention can be achieved. 
   For instance, in the aforesaid embodiments, while a plurality of sets of recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E are arranged to extend spirally, they may alternatively be arranged radially as shown in  FIG. 15 . With such an arrangement, the first cam face that corresponds to the first recesses  23 A through  23 E, the second cam face that corresponds to the second recesses  24 A through  24 E and the third cam face that corresponds to the third recesses  25 A through  25 E are shifted by 30° from each other. For example, the cam faces may be formed in a ring-shaped profile and combined so as to be displaced by 30° from each other. When, as with the third embodiment, the cam groove is formed on the cam  150 , the cam groove may be formed by displacing the phase. 
   However, the above-described embodiments are advantageous in that the diameter of the recess forming surface  21  can be made to have a small diameter and hence the diaphragm pump  1  can be downsized. While the sets of recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E that are arranged spirally in each of the above-described embodiments may require a complicated processing operation if compared with those that are arranged radially, it is in reality not difficult to prepare such sets of recesses when an advanced numerically controlled machine is used. Further, the recesses  23 A through  23 E,  24 A through  24 E,  25 A through  25 E have curved surfaces and are slight dent, and therefore can be formed by using a metal mold. They can be easily by preparing a metal mold. 
   Additionally, it may be so arranged that the recesses  23  through  25  are formed in the diaphragm or the flow path block and the communication grooves  281  through  284  are formed in the flow path block or the diaphragm. In short, it is only necessary that the diaphragm and the flow path block are so configured as to define liquid flow paths including the respective valve chambers, the metering chamber and communication paths. 
   The number of the liquid flow paths  280 , or the individual pumps, is not limited to five of the above-described embodiments as long as it is three or more. More specifically, each of the individual pumps is adapted to show any of three states including a state where transfer of liquid is stopped, a state where the liquid transfer rate is gradually decreasing and a state where the liquid transfer rate is gradually increasing so that the transfer of liquid is accompanied by pulsation if a diaphragm pump has only a single individual pump. Such pulsation cannot be eliminated if a diaphragm pump has two individual pumps because they cannot be used to transfer liquid simultaneously. In other words, at least three individual pumps are indispensable. If, on the other hand, a large number of individual pumps are involved, the influence of the increase and that of the decrease in the liquid transfer rate can be minimized because a plurality of pumps can be driven to operate simultaneously in order to transfer liquid. Then, it is possible to minimize pulsation and transfer liquid at a constant rate. However, as the number of individual pumps increases, the number of recesses  23  through  25  and that of pressing rods  73  through  75  also increase to consequently increase the dimensions of the diaphragm pump  1 . Thus, the use of five pumps as in the case of the above-described embodiments is advantageous because it possible to relatively reduce the dimensions of the pump and realize a constant liquid transfer rate with minimal pulsation. 
   The number of recesses  23  through  25  arranged in each of the liquid flow paths  280  is not limited to 3 and may alternatively be 4 or more than 4. However, a diaphragm pump that can effectively prevent liquid from flowing back can be realized by arranging three recesses in each of the liquid flow paths. Therefore, the use of three recesses in each of the liquid flow path is advantageous from the viewpoint of forming a compact diaphragm pump. 
   Additionally, the first defined angle of intersection and the second defined angle of intersection of the recesses  23  through  25  are not limited to the above-described respective values 30° and 72° and other values may be appropriately selected depending on the number of recesses and the number of liquid flow paths  280 . 
   The profile of the cam faces  511  of the cams  51 ,  150  is not limited to those illustrated by the cam diagrams of the above-described embodiments. For instance, the portions of the cam faces that are used for the respective pressing rods  73  through  75  to move at a constant acceleration may be modified to show a profile of sinusoidal curves. In short, it is only necessary to design the cam faces in such a way that the total liquid transfer rate produced by the pressing rods  73  through  75  is held to a constant level. 
   The combinations of the arrangement of the flow path block and the respective cams  51 ,  150  are not limited to the ones in the embodiments described above. For instance, the cam  150  including the cam grooves  151  through  153  of the third embodiment may be used in the first embodiment, or the cam  51  of the first embodiment may be used in the third embodiment. 
   The drive mechanism for driving the cams  51 ,  150  is not limited to the one that is used in the above-described embodiments. For instance, the cams  51 ,  150  may be directly and rigidly secured to the output shaft without using a spline boss  52  and a spline shaft  53 . The cams  51 ,  150  may be aligned without using a coned disk spring  57  or the like. 
   The motor that can be used for a diaphragm pump according to the present invention may be selected from stepping motors, servo motors, synchronous motors, DC motors, induction motors, reversible motors, air motors and other motors. 
   Further, as with the third embodiment, a biasing section for biasing the guide block  4  toward the diaphragm  8  can also be provided in the first and second embodiments. The biasing section can be arranged as appropriate. One example of the arrangement of the biasing section is shown in  FIG. 16  in which the guide block  4  is axially movably provided on the inner side of the case block  10 , and the guide block  4  is biased toward the diaphragm  8  by a biasing section constituted of the coned disk spring  11  and a cylindrical pressing member  12 . 
   Incidentally, in the case as shown in  FIG. 26 , a resin-made guide ring  13  is pressed into the inner periphery side of the case block  10 , the teeth formed on the inner periphery surface of the guide ring  13  is engaged with the teeth formed on the outer periphery surface of the guide block  4 . By such arrangement, the guide block  4  is movable in the axial direction without rotating. Further, the cam  51 ,  150 , the spline boss  52 , the ball bearing  55  and the coned disk spring  57  are provided on the inner periphery side of the pressing member  12 . 
   By providing a biasing section for biasing the guide block  4  toward the diaphragm  8 , even in the case that the base block  2  and the guide block  4  have relatively low processing accuracy, the accuracy of the liquid transfer rate can be prevented from being dropped. In other words, in the first and second embodiments, since the diaphragm  8  is disposed in the space between the base block  2  and the guide block  4 , and the width of the space is determined depending on processing accuracy of the base block  2 , the holder ring block  3  and the guide block  4 , if the dimension of the space is larger than that of the diaphragm  8 , the liquid may leak out due to the unclosed contact between the diaphragm  8  and the recess forming surface  21 , thereby the accuracy of the liquid transfer rate is dropped. Also, if the dimension of the space is smaller than that of the diaphragm  8 , then the diaphragm  8  may be excessively pressed, so that a portion of the diaphragm  8  may protrude into the recesses  23  through  25  or communication grooves  281  through  284  so as to clog the liquid flow paths  280  and thereby rise possibility that the transfer of the liquid cannot be continued. Therefore, in the first and second embodiment, high processing accuracy for both the base block  2  and the guide block  4  is necessary to get an accurate dimension of the space between the base block  2  and the guide block  4 . 
   In contrast, by providing a biasing section for biasing the guide block  4  toward the diaphragm  8 , even in the case that the base block  2  and the guide block  4  do not have very high processing accuracy, the diaphragm  8  can be kept in close contact with the recess forming surface  21 , and the diaphragm  8  can be prevented from being excessively pressed to clog the liquid flow paths  280 , thereby the accuracy of the liquid transfer rate can be prevented from being dropped, and liquid can be transferred without failure. 
   In the aforesaid embodiment, the width dimensions of the communication grooves  281  through  284  are specified to ⅙ of the width dimensions (diameters) of the recesses  23  through  25 , but the width dimensions of the communication grooves  281  through  284  also can be optionally specified to ½ of the width dimensions (diameters) of the recesses  23  through  25  or even be specified as the same as the width dimensions (diameters) of the recesses  23  through  25  according to the kind of the liquid to be transferred. Incidentally, in the case that the width dimensions of the communication grooves  281  through  284  are specified wide, if the diaphragm  8  is excessively pressed, the diaphragm  8  may protrude into the communication grooves  281  through  284  to possibly clog the liquid flow paths  280 . Accordingly, if the width dimensions of the communication grooves  281  through  284  are needed to be specified wide, it is preferred to either get a high processing accuracy for both the base block  2  and the guide block  4  to obtain an accurate dimension of the space between the base block  2  and guide block  4 , or provide a biasing section for biasing the guide block  4  toward the diaphragm  8 . 
   The profiles, the structures and the materials of any other components are not limited to those described above by referring to the preferred embodiments, which may be modified and/or altered appropriately. 
   Since a diaphragm pumps  1  through  1 B according to the present invention is adapted to drive liquid to flow reversely by reversely rotating the cam  51 ,  150 . Therefore, a diaphragm pumps  1  through  1 B according to the present invention can find applications where liquid is sucked through the port  22  in addition to those where liquid is discharged through the port  22 . 
   In addition to that a diaphragm pumps  1  through  1 B according to the present invention can find applications in the field of apparatus for discharging a small amount of liquid (dispensers) as described above by referring to the preferred embodiments having the nozzle member  27 , it can also be used for discharging a minute amount of liquid into a production line, where a predetermined liquid is flowing, to form a mixture according to the reading of a flow meter installed at the line and/or sampling liquid from the line. 
   Additionally, a diaphragm pumps  1  through  1 B according to the present invention may be installed to intervene somewhere in a production line, where a predetermined liquid is flowing, and operate the drive unit  6  so as to establish an equilibrated state between the pressure of the line upstream relative to the pump and the pressure of the line downstream relative to the pump and meter the flow rate of the liquid from the number of revolutions or pulses per unit time of the drive unit  6  in the equilibrated state. Particularly, a diaphragm pump  1  through  1 B according to the present invention is suited for sucking and discharging a very small amount of liquid and hence it can be utilized as a flow meter for metering a very low flow rate. 
   The material of the diaphragm  8  is not limited to rubber and the diaphragm  8  may be formed by a multilayer material prepared by laying fluorine resin and rubber. With such an arrangement, the surface layer of the diaphragm  8  that is brought to contact liquid may be formed by fluorine resin that is highly resistive against chemicals to remarkably broaden the number of types of liquid that can be used with the diaphragm  8  and consequently find a broader scope of applications. In short, any resiliently deformable material may be used for the diaphragm  8  so long as it can be deformed by the pressure applied by the pressing rods  73  through  75  and resiliently restore the original state when the pressure of the pressing rods  73  through  75  is removed. 
   When fluorine resin or the like that is less deformable than rubber is used for the diaphragm  8 , it may be necessary to reduce the depth of the recesses  23  through  25  to about 0.1 mm and design the profile in a specific way so that the less deformable diaphragm  8  may closely contact to the recesses  23  through  25 . In short, it is only necessary to appropriately design the profile and select the dimensions of the recesses  23  through  25  depending on the material of the diaphragm  8  and the liquid transfer rate of the diaphragm pump. 
   While the recesses  23  through  25  are formed in a width larger than the width of the communication grooves  281  through  284  in the above-described embodiments, they may alternatively be formed in the width same as that of the communication grooves. For instance, as shown in  FIG. 27 , the recessed grooves may be formed radially from the port  22  formed at the central axis of the flow path block. The recessed groove may have a substantially arcuate cross section with constant width. In such arrangement, by disposing the respective pressing rods  73  through  75  so as to align with the recessed grooves and moving the pressing rods  73  through  75  toward the recessed grooves (flow path block), the diaphragm  8  can be closely contacted to the recessed grooves, thereby closing the recessed grooves. On the other hand, by moving the pressing rods  73  through  75  away from the recessed grooves, the diaphragm  8  detaches from the recessed groove, thereby opening the recessed grooves. Therefore, even with the recessed grooves with constant width, the respective recesses  23  through  25 , the communication grooves  281  through  284  (the respective valve chambers, the metering chamber and the communication grooves) are substantially formed. 
   With such arrangement, it is only required to form a plurality of recessed grooves having constant width on the flow path block, so that processing can be simple and the cost can be reduced. Further, since the groove widths of the liquid flow paths are relatively large and constant, even a liquid with high viscosity can be discharged. However, as shown in  FIG. 27 , since the diaphragms  8  closely contact with the recessed grooves linearly in a direction orthogonal to the longitudinal direction of the grooves, close-contact areas are smaller as compared to the embodiments described above. Therefore, the respective embodiments described above advantageously have higher sealing performance of the liquid flow path. 
   The diaphragm pump according to the present invention can be incorporated into a manufacturing device of electronic component. The manufacturing device of electronic component is preferred to have the diaphragm pump, a liquid feeder for supplying the liquid to the suction flow path of the diaphragm pump, an discharge nozzle provided to discharge flow path, and a controller for controlling the drive section of the diaphragm pump, in which liquid supplied by the liquid feeder is discharged from the discharge nozzle through the diaphragm pump to manufacture electric component. 
   In such a manufacturing device of electronic component, since the diaphragm pump capable of accurately transferring a trace quantity of liquid is employed, a trace quantity of liquid is enable to be accurately discharged by the discharge nozzle, and even particle-containing liquid with silver powder, silica powder or the like contained therein can be discharged without crushing and particles contained. Thus, the diaphragm pump not only can be used as a dispenser for discharging every kinds of liquid such as adhesive and resin, but can be used to every kinds of manufacturing device of electronic component in which such a dispenser is incorporated. In particular, since a trace quantity of particle-containing liquid can be accurately transferred, it is most suitable to the manufacturing devices of electronic components such as a die bonder, in which a semiconductor chip is fixed to the substrate by the adhesive such as silver paste, or a manufacturing device for manufacturing LED, in which the LED chip is sealed by the resin with silica powder contained. 
   INDUSTRIAL AVAILABILITY 
   The present invention is applicable to diaphragm pumps that can transfer liquid at a constant rate without pulsation. Further, the present invention is applicable to manufacturing devices of electronic component such as a die bonder, in which a semiconductor chip is fixed to the substrate by the adhesive such as silver paste discharged from a diaphragm pump, or a manufacturing device for manufacturing light-emitting diode (LED), in which the LED chip is sealed by the resin with silica powder contained discharged from a diaphragm pump.