Abstract:
This injection apparatus injects and fills the inside of a mold with a molding material, and increases the pressure. The injection apparatus is provided with a unit for a low speed step, a unit for a high speed step, a unit for a pressure increasing step, and an injection plunger. A rod of a first unit, which is any one of the three units, is mechanically coupled to the injection plunger. A rod of a second unit, which is one of the two units other than the first unit, is mechanically coupled to the first unit. A rod of a third unit, which is the unit other than the first and second units, is mechanically coupled to the second unit.

Description:
TECHNICAL FIELD 
     The present invention relates to an injection apparatus that injects, fills, and pressurizes molding material in a mold. 
     BACKGROUND ART 
     Generally, an injection apparatus for a molding machine moves an injection plunger forward in a sleeve with an injection cylinder and extrudes molding material (e.g., molten material) out of the sleeve into a cavity formed between molds (mold unit) to inject and fill the molding material into the cavity. The injecting and filling operation includes a low speed operation, a high speed operation, and a pressurizing operation. More specifically, in an initial state of the injection, the injection apparatus moves an injection plunger forward at a relatively low speed to prevent the inclusion of air in the molding material. Then, to shorten the molding cycle, the injection plunger is moved forward at a relatively high speed. Subsequently, the injection apparatus pressurizes the molding material in the cavity by applying force in the direction the injection plunger moves forward so that sink marks are not included in the molded product. Patent document 1 discloses an example of an injection apparatus (die cast machine) that realizes the operations of such an injection apparatus. 
     Referring to  FIG. 6 , the injection apparatus of patent document  1  includes a hydraulic circuit and executes hydraulic pressure control on the hydraulic circuit to perform the injection and filling operation. More specifically, in the injection apparatus, an injection cylinder  80  includes a head chamber  80   a  connected by a flow passage to a filling accumulator  82 , which is in communication with a gas tank  81 . The flow passage includes a pilot check valve  84  and a speed control valve  85 . The filling accumulator  82  is supplied with hydraulic oil that is pressurized to a predetermined pressure by a hydraulic pump  83   a.    
     A flow passage, which is in communication with the speed control valve  85 , is connected to a pressurizing operation accumulator  87 , which is in communication with a gas tank  86 . A flow passage connecting the filling accumulator  82 , the pressurizing operation accumulator  87 , and the head chamber  80   a  of the injection cylinder  80  includes a flow rate control valve  88 . The flow rate control valve  88  regulates the flow rate of the hydraulic oil to control the movement speed of a piston in the injection cylinder  80 . 
     In the injection apparatus of patent document  1 , the low speed operation and the high speed operation supply the head chamber  80   a  of the injection cylinder  80  with the hydraulic oil accumulated in the filling accumulator  82  to move the piston  80   c  at a low speed or a high speed. The speed control valve  85  controls the movement speed of the piston  80   c . The pressurizing operation is performed by supplying the head chamber  80   a  of the injection cylinder  80  with high-pressure hydraulic oil from the pressurizing operation accumulator  87 . In this case, the flow rate control valve  88  regulates the flow rate of the hydraulic oil to control the pressurizing time. 
     PRIOR ART DOCUMENT 
     Patent Documenet 
     Patent Document 1: Japanese Patent No. 3662001 
     SUMMARY OF THE INVENTION 
     The injection apparatus disclosed in patent document 1 controls the speed control valve  85  and the flow rate control valve  88  to control the hydraulic pressure in the hydraulic circuit and perform the low speed operation, the high speed operation, and the pressurizing operation. In the low speed operation, it is desirable that the injection velocity be finely controlled to prevent the inclusion of air in the molding material. In the high speed operation, it is desirable that the injection time be further reduced. In the pressurizing operation, it is desirable that the thrust source used for pressurization be reduced in size. However, when only controlling the hydraulic pressure of the hydraulic pressure circuit like in patent document  1 , it is difficult to execute control that satisfies the demands unique to each operation. 
     It is an object of the present invention to provide an injection apparatus capable of realizing control that is specialized for a low speed operation, a high speed operation, and a pressurizing operation. 
     Means for Solving the Problems 
     To achieve the above object, one aspect of the present invention is an injection apparatus that injects, fills, and pressurizes molding material in a mold. The injection apparatus includes a low speed operation unit, a high speed operation unit, a pressurizing operation unit, and an injection plunger. The low speed operation unit includes a low speed operation cylinder, which includes a low speed operation rod, and an electric drive source, which drives the low speed operation cylinder. The high speed operation unit includes a high speed operation cylinder, which includes a high speed operation rod, and a hydraulic pressure drive source, which drives the high speed operation cylinder. The pressurizing operation unit includes a pressurizing operation cylinder, which includes a pressurizing operation rod, and a drive source, which drives the pressurizing operation cylinder. The injection plunger injects the molding material into the mold. A rod of a first unit, which is one of the three units, is mechanically connected to the injection plunger. A rod of a second unit, which is one of the two units other than the first unit, is mechanically connected to the first unit. A rod of a third unit, which is the unit other than the first and second units, is mechanically connected to the second unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an injection apparatus according to an embodiment of the present invention. 
         FIG. 2  is a graph showing changes in the injection pressure and the injection velocity of the injection apparatus of  FIG. 1 . 
         FIG. 3  is a schematic diagram showing the injection apparatus of  FIG. 1  during a low speed operation. 
         FIG. 4  is a schematic diagram showing the injection apparatus of  FIG. 1  during a high speed operation. 
         FIG. 5  is a schematic diagram showing the injection apparatus of  FIG. 1  during a pressurizing operation. 
         FIG. 6  is a diagram showing a prior art injection apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the present invention will now be described with reference to  FIGS. 1 to 5 . 
     As shown in  FIG. 1 , a mold K includes a fixed mold  12  and a movable mold  13 . A mold fastening device (not shown) opens and closes the mold K and fastens the fixed mold  12  and the movable mold  13 . An injection apparatus  11  injects and fills a metal material serving as the molding material into a cavity  14  formed in the mold K. The metal material, which is injected into the mold K, is solidified and then removed from the mold K to obtain a desired molded product. 
     The fixed mold  12  includes an injection sleeve  15 , which is in communication with the cavity  14 , and an injection plunger  16 , which is arranged in the injection sleeve  15  in a movable manner. When the injection sleeve  15  is supplied with metal material through a supply port (not shown) formed in the injection sleeve  15 , the injection plunger  16  is moved in the injection sleeve  15  toward the cavity  14  to inject and fill the metal material into the cavity  14 . 
     A connection member  17  connects the injection plunger  16  to a distal end of a rod  18   c  of a pressurizing operation cylinder  18 . In the pressurizing operation cylinder  18 , a cylinder tube  18   a  accommodates a movable piston  18   b , which is formed integrally with the rod  18   c . The piston  18   b  divides the interior of the cylinder tube  18   a  into a rod chamber  18   e , from which the rod  18   c  extends, and an opposite head chamber  18   d.    
     The rod chamber  18   e  opens to the atmosphere through a supply/discharge port (not shown) formed in the cylinder tube  18   a . An amplification oil passage  19  connects the head chamber  18   d  to an operation cylinder  20 . The operation cylinder  20  has a smaller cylinder diameter than the pressurizing operation cylinder  18 . The operation cylinder  20 , which has a smaller diameter than the pressurizing operation cylinder  18 , and the amplification oil passage  19 , which connects the operation cylinder  20  to the pressurizing operation cylinder  18 , form an amplification circuit that amplifies the thrust of the rod  18   c  in the pressurizing operation cylinder  18 . 
     The operation cylinder  20  includes a cylinder tube  20   a  that accommodates a movable piston  20   b . A rod  20   c  is formed integrally with the piston  20   b . The piston  20   b  divides the interior of the cylinder tube  20   a  of the operation cylinder  20  into a rod chamber  20   e , from which the rod  20   c  extends, and an opposite head chamber  20   d . The amplification oil passage  19  connects the head chamber  20   d  of the operation cylinder  20  and the head chamber  18   d  of the pressurizing operation cylinder  18 . Hydraulic oil serving as an incompressible fluid is sealed in the two head chambers  18   d  and  20   d.    
     An operation ball screw/nut mechanism BN 1  that moves the rod  20   c  forward and rearward is connected to the rod  20   c  of the operation cylinder  20 . In detail, an operation nut N 1  is connected to the distal end of the rod  20   c , and the operation nut N 1  is fastened to an operation ball screw B 1 , which is rotated by an operation motor M 1  that serves as an operational electric drive source. The operation ball screw B 1  is rotated so that the operation nut N 1  moves forward or rearward in the axial direction of the operation ball screw B 1 . In this manner, the operation ball screw/nut mechanism BN 1  includes the operation nut N 1 , the operation ball screw B 1 , and the operation motor M 1 . 
     In the present embodiment, the pressurizing operation cylinder  18 , the amplification oil passage  19 , the operation cylinder  20 , and the operation ball screw/nut mechanism BN 1  form a pressurizing operation unit U 1 . 
     In the pressurizing operation unit U 1 , the side opposite to the mold K is mechanically connected to a rod  30   c  of a low speed operation cylinder  30  in a low speed operation unit U 2 . The low speed operation cylinder  30  includes a cylinder tube  30   a  that accommodates a movable piston  30   b , which is formed integrally with the rod  30   c . The piston  30   b  divides the interior of the cylinder tube  30   a  into a first operational chamber  30   e , at the side of the mold K, and an opposite second operational chamber  30   d.    
     A low speed operation ball screw/nut mechanism BN 2  that moves the rod  30   c  forward and rearward is connected to the rod  30   c . In detail, a low speed operation nut N 2  is connected to the rod  30   c , and the low speed operation nut N 2  is fastened to a low speed operation ball screw B 2 . The low speed operation ball screw B 2  is rotated by a low speed operation motor M 2  serving as an electric drive source. 
     The low speed operation motor M 2  moves the low speed operation nut N 2  forward or rearward in the axial direction of the low speed operation ball screw B 2 . The low speed operation ball screw/nut mechanism BN 2  includes the low speed operation nut N 2 , the low speed operation ball screw B 2 , and the low speed operation motor M 2 . 
     The first operational chamber  30   e  of the low speed operation cylinder  30  is connected to one end of a low speed operation oil passage  31 . The second operational chamber  30   d  is connected to the other end of the low speed operation oil passage  31 . In other words, the first operational chamber  30   e  and the second operational chamber  30   d  form a closed circuit with the low speed operation oil passage  31 . Further, a low speed operation electromagnetic switch valve  32  is arranged in the low speed operation oil passage  31 . The low speed operation electromagnetic switch valve  32  is switchable between a first position  32   a , which disconnects the second operational chamber  30   d  and the first operational chamber  30   e , and a second position  32   b , which allows hydraulic oil to flow from the second operational chamber  30   d  to the first operational chamber  30   e.    
     The low speed operation oil passage  31  includes a bypass oil passage  33  that bypasses the low speed operation electromagnetic switch valve  32 . A check valve  34  is arranged in the bypass oil passage  33 . When the low speed operation electromagnetic switch valve  32  is at the first position  32   a , the check valve  34  inhibits the flow of hydraulic oil from the second operational chamber  30   d  to the first operational chamber  30   e  and permits the flow of hydraulic oil from the first operational chamber  30   e  to the second operational chamber  30   d.    
     When the low speed operation electromagnetic switch valve  32  is at the first position  32   a , even if back pressure force from the mold K acts on the rod  30   c  such that the rod  30   c  pushes the piston  30   b  toward the second operational chamber  30   d , the check valve  34  inhibits the discharge of hydraulic oil from the second operational chamber  30   d  to the first operational chamber  30   e , and the hydraulic oil receives the back pressure force. Accordingly, in the present embodiment, the low speed operation unit U 2  includes the low speed operation cylinder  30 , the low speed operation ball screw/nut mechanism BN 2 , and a back pressure receiving portion. 
     In the low speed operation unit U 2 , the side opposite to the pressurizing operation unit U 1  is mechanically connected to a first rod  40   c  of a high speed operation cylinder  40  in a high speed operation unit U 3 . The high speed operation cylinder  40  is a double rod cylinder and includes a cylinder tube  40   a , which accommodates a movable piston  40   b  formed integrally with the first rod  40   c . A second rod  40   f , which is formed integrally with the first rod  40   c , extends opposite to the piston  40   b . The piston  40   b  divides the interior of the cylinder tube  40   a  into a first chamber  40   e , at the side of the first rod  40   c , and a second chamber  40   d , at the side of the second rod  40   f  that is the opposite side. 
     A supply/discharge mechanism T is connected to the first chamber  40   e . The supply/discharge mechanism T supplies hydraulic oil to the first chamber  40   e  and discharges hydraulic oil from the first chamber  40   e . The supply/discharge mechanism T includes an oil tank  43 , a pump  44  that draws hydraulic oil from the oil tank  43 , and an electromagnetic switch valve  45  arranged in a supply/discharge oil passage  47 . The electromagnetic switch valve  45  may be switched to a first position  45   a , at which the electromagnetic switch valve  45  may supply the hydraulic oil drawn from the oil tank  43  by the pump  44  to the first chamber  40   e , and a second position  45   b , at which the electromagnetic switch valve  45  discharges the hydraulic oil from the first chamber  40   e  into the oil tank  43 . An accumulator  46  serving as a hydraulic pressure drive force is connected to the second chamber  40   d  of the high speed operation cylinder  40 . Hydraulic oil is accumulated in the accumulator  46 . The hydraulic oil from the accumulator  46  is supplied to the second chamber  40   d . Hydraulic pressure (operational pressure) directed toward the low speed operation unit U 2  constantly acts on the piston  40   b.    
     The second rod  40   f  of the high speed operation cylinder  40  defines a connection portion  40   g . The high speed operation unit U 3  includes a connection driver  49  that is discrete from the high speed operation cylinder  40 . The connection driver  49  may be mechanically connected to or disconnected from the connection portion  40   g . The connection driver  49  may be rotated by a connection motor  49   a . When the connection driver  49  is connected to the connection portion  40   g , forward movement of the piston  40   b  (first and second rods  40   c  and  40   f ) produced by the hydraulic oil from the accumulator  46  may be restricted. 
     When the connection motor  49   a  drives the connection driver  49 , the connection driver  49  is disconnected from the connection portion  40   g . This permits forward movement of the piston  40   b  produced by the hydraulic oil from the accumulator  46 . In the present embodiment, the connection portion  40   g  and the connection driver  49  form a connection mechanism R, and the connection portion  40   g  and the connection driver  49  form a chuck structure. The high speed operation unit U 3  includes the connection mechanism R, the high speed operation cylinder  40 , the supply/discharge mechanism T, and the accumulator  46 . 
     In the present embodiment, the injection plunger  16  mechanically connects the rod  18   c  of the pressurizing operation unit U 1  to the mold K, and mechanically connects the rod  30   c  of the low speed operation unit U 2  to the pressurizing operation unit U 1 . Further, the rod  40   c  of the high speed operation unit U 3  is mechanically connected to the low speed operation unit U 2 . The rods  18   c ,  30   c , and  40   c  are arranged along the same axis. The pressurizing operation cylinder  18 , the low speed operation cylinder  30 , and the high speed operation cylinder  40  are arranged in series. 
     The operation pattern (ejection pattern) when the injection apparatus  11  performs injection will now be described with reference to  FIG. 2 . 
     The injection apparatus  11  performs three operations, the low speed operation, the high speed operation, and the pressurizing operation. The low speed operation is performed in the initial stage of injection and operates the injection plunger  16  with the low speed operation unit U 2 . 
     The high speed operation follows the low speed operation and operates the injection plunger  16  at a higher speed than the low speed operation. The high speed operation operates the injection plunger  16  in the high speed operation unit U 3 . 
     The pressurizing operation, which follows the high speed operation and which is the final stage of injection, pressurizes the metal material in the cavity  14  with the force generated when the injection plunger  16  moves forward toward the mold K. The pressurizing operation operates the injection plunger  16  in the pressurizing operation unit U 1 . 
     In each of these operations, the injection apparatus  11  is operated in different patterns, as shown in  FIG. 2 . More specifically, in the high speed operation, the injection plunger  16  needs to be operated at a higher speed than the low speed operation. However, speed is not necessary in the pressurizing operation. Further, the injection plunger  16  needs to be operated to apply a higher pressure than the low speed operation and the high speed operation in the pressurizing operation but does not have to be operated to apply as much pressure as the pressurizing operation in the low speed operation and the high speed operation,. 
     The operation of the injection apparatus  11  in the present embodiment will now be described with reference to  FIGS. 1 and 3 . 
     Before starting the low speed operation, the injection plunger  16  of the injection sleeve  15 , the rod  18   c  of the pressurizing operation cylinder  18 , the rod  20   c  of the operation cylinder  20 , the rod  30   c  of the low speed operation cylinder  30 , and the two rods  40   c  and  40   f  of the high speed operation cylinder  40  are located at predetermined initial positions as shown in  FIG. 1 . The rods  18   c ,  20   c ,  30   c ,  40   c , and  40   f  located at the initial positions do not apply injection pressure to the metal material supplied to the injection sleeve  15  (time T 1  in  FIG. 2 ). 
     The low speed operation electromagnetic switch valve  32  of the low speed operation unit U 2  is switched to the first position  32   a  during molding to disconnect the first operational chamber  30   e  and the second operational chamber  30   d . Further, the electromagnetic switch valve  45  in the supply/discharge mechanism T of the high speed operation unit U 3  is switched to the first position  45   a  so that hydraulic oil does not return from the first chamber  40   e  in the high speed operation cylinder  40  to the oil tank  43 . 
     After completing molding preparations such as the fastening of the fixed mold  12  and the movable mold  13  and the supply of metal material to the injection sleeve  15 , the low speed operation unit U 2  starts the low speed operation. In the low speed operation, the rod  30   c  of the low speed operation cylinder  30  moves at the injection velocity V 1  shown in  FIG. 2 . The low speed operation motor M 2  is driven to rotate the low speed operation ball screw B 2  and move forward the low speed operation nut N 2 , which is fastened to the low speed operation ball screw B 2 . As a result, referring to  FIG. 3 , the low speed operation nut N 2  applies drive force to the rod  30   c  of the low speed operation cylinder  30  and moves the rod  30   c  forward. The forward movement of the rod  30   c  entirely pushes the pressurizing operation unit U 1  toward the mold K. 
     When the pressurizing operation unit U 1  moves forward, the pressurizing operation cylinder  18  moves forward. The injection plunger  16 , which is connected to the rod  18   c  of the pressurizing operation cylinder  18 , is also moved forward. The forward movement of the injection plunger  16  injects the metal material from the injection sleeve  15  to the cavity  14 . 
     When the rod  30   c  of the low speed operation cylinder  30  reaches a terminal position in the low speed operation (time T 2  of  FIG. 2 ), the low speed operation is shifted to the high speed operation. 
     The high speed operation will now be described with reference to  FIG. 4 . 
     In the high speed operation, the injection plunger  16  accumulates the hydraulic oil in the accumulator  46  and drives the connection motor  49   a  of the connection driver  49  to obtain the injection velocity V 2  shown in  FIG. 2 . Simultaneously, the electromagnetic switch valve  45  is switched to the second position  45   b . When the first connection member  52  and the second connection member  53  are disconnected, the piston  40   b , on which the hydraulic oil from the accumulator  46  acts, is immediately moved toward the first chamber  40   e  at a high speed. Here, hydraulic oil is discharged from the first chamber  40   e  to the oil tank  43  through the electromagnetic switch valve  45 . As the piston  40   b  moves at a high speed, the first rod  40   c  is also moved at a high speed. Further, the low speed operation unit U 2  moves the pressurizing operation unit U 1  forward toward the mold K. 
     When the low speed operation unit U 2  moves the pressurizing operation unit U 1  forward at the injection velocity V 2 , the pressurizing operation cylinder  18  moves forward. This moves the injection plunger  16  forward, which is connected to the rod  18   c  of the pressurizing operation cylinder  18 , at the injection velocity V 2  and injects metal material from the injection sleeve  15  into the cavity  14 . During the high speed operation, the pressurizing operation unit U 1  and the low speed operation unit U 2  are operated at higher speeds compared to the low speed operation. 
     During the high speed operation, the pressurizing operation unit U 1  applies back pressure force from the mold K to the low speed operation cylinder  30  of the low speed operation unit U 2 . However, in the low speed operation cylinder  30 , the check valve  34  inhibits the flow of the hydraulic oil from the second operational chamber  30   d  to the first operational chamber  30   e . This inhibits rearward movement of the rod  30   c  toward the second operational chamber  30   d  caused by the back pressure force. As a result, rotation is inhibited in the low speed operation ball screw B 2  caused by the low speed operation nut N 2 , which is fastened to the rod  30   c . This inhibits the rotation of the low speed operation motor M 2 . 
     The pressurizing operation will now be described with reference to  FIG. 5 . 
     In the pressurizing operation, the pressure applied by the rod  18   c  of the pressurizing operation cylinder  18  produces the injection pressure P shown in  FIG. 2 . The rotation produced by the operation motor M 1  moves forward the operation nut N 1 , which is fastened to the operation ball screw B 1 . The operation nut N 1  applies drive force to the rod  20   c  of the operation cylinder  20  and moves the rod  20   c  forward. 
     When the rod  20   c  of the operation cylinder  20  moves forward, hydraulic oil is supplied from the head chamber  20   d  to the head chamber  18   d  of the pressurizing operation cylinder  18  through the amplification oil passage  19 . In the present embodiment, when the hydraulic oil is supplied from the operation cylinder  20  to the head chamber  18   d  of the pressurizing operation cylinder  18 , in accordance with the Pascal&#39;s principle, the pressure in the head chamber  18   d  increases, and the pressure received by the injection plunger  16  from the pressurizing operation cylinder  18  increases. This increases the force of the injection plunger  16  that pressurizes the metal material in the cavity  14 . During the pressurizing operation, air is forced out of the rod chamber  18   e  of the pressurizing operation cylinder  18  and into the atmosphere. 
     During the pressurizing operation, the back pressure force from the mold K also acts on the low speed operation cylinder  30  of the low speed operation unit U 2  through the pressurizing operation unit U 1 . However, in the low speed operation cylinder  30 , the flow of hydraulic oil from the second operational chamber  30   d  to the first operational chamber  30   e  is inhibited by the check valve  34 . Thus, the back pressure does not move the rod  30   c  rearward toward the second operational chamber  30   d . This inhibits the rotation of the low speed operation ball screw B 2  and the low speed operation motor M 2  through the low speed operation nut N 2  fastened to the rod  30   c.    
     Then, when the metal material in the cavity  14  is solidified, the operation motor M 1  produces rotation in a direction reversed from the pressurizing operation. The operation motor M 1  moves the operation nut N 1 , which is fastened to the operation ball screw B 1 , rearward. This applies drive force to the rod  20   c  of the operation cylinder  20  with the operation nut N 1 . When the rod  20   c  of the operation cylinder  20  moves rearward, hydraulic oil is drawn from the head chamber  18   d  of the pressurizing operation cylinder  18  into the head chamber  20   d  of the operation cylinder  20  through the amplification oil passage  19 . This moves the rod  18   c  of the pressurizing operation cylinder  18  rearward. As a result, the injection plunger  16  moves rearward in the injection sleeve  15 . 
     Subsequently, the low speed operation electromagnetic switch valve  32  in the low speed operation unit U 2  is switched to the second position  32   b  to allow the flow of hydraulic oil from the second operational chamber  30   d  to the first operational chamber  30   e . The low speed operation motor M 2  produces rotation reversed from the low speed operation. The low speed operation motor M 2  moves the low speed operation nut N 2 , which is fastened to the low speed operation ball screw B 2 , rearward. This applies drive force to the rod  30   c  of the low speed operation cylinder  30  with the low speed operation nut N 2 . When the rod  30   c  of the low speed operation cylinder  30  moves rearward, hydraulic oil flows from the second operational chamber  30   d  of the low speed operation cylinder  30  to the first operational chamber  30   e  through the low speed operation oil passage  31  and the low speed operation electromagnetic switch valve  32 . As a result, the rod  30   c  moves rearward, and the pressurizing operation unit U 1 , to which the rod  30   c  is connected, moves rearward. This moves the injection plunger  16  rearward in the injection sleeve  15 . 
     Then, in the high speed operation unit U 3 , the electromagnetic switch valve  45  is controlled and switched to the first position  45   a . The pump  44  is driven to supply hydraulic oil from the oil tank  43  to the first chamber  40   e . This moves the piston  40   b  rearward toward the second chamber  40   d , and the hydraulic oil of the second chamber  40   d  is accumulated in the accumulator  46 . At the same time, the piston  40   b  moves rearward. This applies drive force to the first rod  40   c  and the second rod  40   f  that moves the first rod  40   c  and the second rod  40   f  rearward and moves the low speed operation unit U 2 , to which the first rod  40   c  is connected, rearward. The pressurizing operation unit U 1 , to which the rod  30   c  of the low speed operation unit U 2  is connected, is also moved rearward. As a result, the injection plunger  16  moves rearward in the injection sleeve  15 . 
     When the second rod  40   f  moves rearward and the connection portion  40   g  reaches the connection driver  49 , the connection motor  49   a  is driven to connect the connection driver  49  to the connection portion  40   g  and restrict forward movement of the piston  40   b . Accordingly, the injection plunger  16  of the injection sleeve  15 , the rod  18   c  of the pressurizing operation cylinder  18 , the rod  20   c  of the operation cylinder  20 , the rod  30   c  of the low speed operation cylinder  30 , and the two rods  40   c  and  40   f  of the high speed operation cylinder  40  are located at the initial positions shown in  FIG. 1 . Then, the fixed mold  12  and the movable mold  13  are separated to remove the molded product from the mold. 
     The above embodiment has the advantages described below. 
     (1) The injection apparatus  11  includes the pressurizing unit U 1 , the low speed operation unit U 2 , and the high speed operation unit U 3 , each specialized in a certain operation. In the injection apparatus  11 , the rod  18   c  of the pressurizing operation cylinder  18  in the pressurizing operation unit U 1  is mechanically connected to the mold K by the injection plunger  16 , and the rod  30   c  of the low speed operation cylinder  30  in the low speed operation unit U 2  is mechanically connected to the pressurizing operation unit U 1 . Further, the rod  40   c  of the high speed operation cylinder  40  in the high speed operation unit U 3  is mechanically connected to the low speed operation unit U 2 . 
     The high speed operation unit U 3  that performs high speed operations uses the accumulator  46  as a drive source. The accumulation amount in the accumulator  46  is adjusted to adjust the injection time during a high speed operation. This allows for the injection time to be reduced. 
     The pressurizing unit U 1  that performs pressurizing operations includes the pressurizing operation cylinder  18 , which performs pressurizing operations and is independent, and the operation cylinder  20  and the operation motor M 1 , which serve as the drive source of the pressurizing operation cylinder  18 . Thus, in comparison to when an accumulator, a flow rate control valve, and a hydraulic circuit are needed as a drive source to perform a pressurizing operation like in the prior art, the drive source may be reduced in size. Further, under the control of the operation motor M 1 , the operation cylinder  20  moves the piston  20   b  to the desired position. This accurately controls the amount (pressure) of the hydraulic oil supplied to the pressurizing operation cylinder  18 . 
     Accordingly, the low speed operation, the high speed operation, and the pressurizing operation are independently performed by the units U 1 , U 2 , and U 3 . This enables movements that are specialized for each operation, and allows for demands to be met that are unique to each operation. Further, the units U 1 , U 2 , and U 3  are mechanically connected. This eliminates the need for hydraulic circuits or control valve to operate the units U 1 , U 2 , and U 3  in cooperation with one another. Thus, the structure of the injection apparatus  11  may be simplified. 
     (2) The operation motor M 1  is employed as the drive source for the pressurizing operation unit U 1 , and the low speed operation motor M 2  is used as a drive source for the low speed operation unit U 2 . Further, the accumulator  46  is employed as the drive source for the high speed operation unit U 3 . For example, in the high speed operation, when the drive source is an electric drive source, the electric drive source would be enlarged since the high speed operation cylinder  40  is operated at a high speed. However, the use of the accumulator  46  as the drive source for the high speed operation allows for the high speed operation cylinder  40  to be operated at a high speed without enlarging the drive source. Thus, by using different electric drive sources and hydraulic pressure drive sources in accordance with the characteristics for each operation, the injection apparatus  11  may lower costs while obtaining high quality. 
     (3) The low speed operation unit U 2  includes a back pressure receiving portion that receives back pressure from the mold K. The back pressure receiving portion inhibits rearward movement of the rod  30   c  of the low speed operation cylinder  30  caused by a back pressure. That is, the back pressure receiving portions inhibits movement of the rod  30   c  in a direction heading away from the mold K. This impedes rotation of the low speed operation ball screw B 2  with the low speed operation nut N 2  caused by back pressure. Thus, even when using the low speed operation motor M 2  as the drive source for the rod  30   c , there is no need for the low speed operation motor M 2  to receive the back pressure. This prevents rotation of the low speed operation motor M 2  caused by back pressure. Further, since the back pressure receiving portion receives the back pressure, there is no need to enlarge the low speed operation motor M 2 . This allows for the employment of the low speed operation motor M 2  having only the minimum output required to move the low speed operation cylinder  30 . Thus, the costs of the low speed operation motor M 2  may be reduced. 
     (4) In the low speed operation unit U 2 , the low speed operation nut N 2  is connected to the rod  30   c  of the low speed operation cylinder  30 , and the low speed operation ball screw B 2  rotated by the low speed operation motor M 2  is fastened to the low speed operation nut N 2 . The back pressure receiving portion is formed by the low speed operation oil passage  31 , which connects the first operational chamber  30   e  and the second operational chamber  30   d  of the low speed operation cylinder  30 , and the check valve  34 , which is arranged in the bypass oil passage  33  of the low speed operation oil passage  31 . Thus, the back pressure from the mold K may be received with the simple structure of the hydraulic pressure circuit (closed circuit) and the check valve, and rearward movement of the rod  30   c  caused by a back pressure may be prevented. 
     (5) In the high speed operation unit U 3 , the accumulator  46  is connected to the second chamber  40   d  of the high speed operation cylinder  40 . Further, the connection portion  40   g , which is integral with the second rod  40   f , may be mechanically connected to and disconnected from the connection driver  49 . Thus, by restricting movement of the second rod  40   f  with the connection mechanism R when hydraulic pressure of the accumulator  46  is acting on the second rod  40   f , hydraulic oil may be kept acting on the second rod  40   f . When the connection portion  40   g  and the connection driver  49  are disconnected, the piston  40   b , on which the hydraulic pressure from the accumulator  46  acts, may be immediately moved toward the second chamber  40   d , and the first rod  40   c  of the high speed operation cylinder  40  may be immediately moved. This reduces the time until which the desired hydraulic pressure is reached compared to, for example, when opening a valve to supply the hydraulic oil accumulated in the accumulator  46  to the second chamber  40   d , in which there would be a time lag from when the desired open degree of the valve is obtained to when the desired hydraulic pressure is obtained. As a result, the injection time for a high speed operation may be reduced. 
     (6) In the pressurizing operation unit U 1 , the drive source for the pressurizing operation cylinder  18  is formed by the operation cylinder  20 , which has a smaller diameter than the pressurizing operation cylinder  18  and which moves the pressurizing operation cylinder  18  by applying fluid pressure of a non-compressible fluid to the pressurizing operation cylinder  18 , and the operation motor M 1 , which drives the operation cylinder  20 . By using cylinders with different diameters, the pressurizing operation cylinder  18  may generate a large pressure even when using the small-diameter operation cylinder  20  as the drive source. This allows for the employment of a motor having only the minimum output required to operate the operation cylinder  20 . Thus, the operation motor M 1  may be reduced in size, and the cost of the operation motor M 1  may be reduced. 
     The above embodiment may be modified as follows. 
     In the embodiment, the connection mechanism R is formed by a chuck structure including the connection portion  40   g  and the connection driver  49 . However, the connection portion  40   g  and the connection driver  49  may be changed to a collet structure, a ball coupler structure, a BNC connector structure, or the like. 
     The check valve  34  may be omitted from the low speed operation unit U 2 . In this case, the low speed operation motor M 2  may be enlarged to receive the back pressure. 
     In the pressurizing operation unit U 1  and the low speed operation unit U 2 , the drive sources for the operation cylinder  20  and the low speed operation cylinder  30  may be linear motors. In this case, the rod  20   c  of the operation cylinder  20  and the rod  30   c  of the low speed operation cylinder  30  may be directly moved straight by the linear motors. 
     In the high speed operation unit U 3 , a flow rate control valve may be arranged between the accumulator  46  and the second chamber  40   d  of the high speed operation cylinder  40 . In this case, the flow rate control valve regulates the amount of hydraulic oil discharged from the accumulator  46  to control the operation speed of the high speed operation cylinder  40 . 
     In the embodiment, the pressurizing operation unit U 1  connected to the injection plunger  16 , the low speed operation unit U 2  connected to the pressurizing operation unit U 1 , and the high speed operation unit U 3  connected to the low speed operation unit U 2  are sequentially arranged in the injection apparatus  11 . However, the arrangement of the three units U 1 , U 2 , and U 3  may be changed. 
     In the embodiment, the operation motor M 1  is operated to move the rod  18   c  of the pressurizing operation cylinder  18  rearward in the pressurizing operation unit U 1 . Instead, hydraulic oil, which serves as a non-compressible fluid, may be supplied to the rod chamber  18   e  of the pressurizing operation cylinder  18 . Further, a supply/discharge mechanism may be used to discharge hydraulic oil from the rod chamber  18   e . The supply/discharge mechanism may be used to move the rod  18   c  rearward. 
     The injection apparatus  11  may be applied to an injection apparatus that injects resin material into the cavity  14  to manufacture a resin molded product.