JP2008069770A - Gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable displacement gear pump having an increased mechanical efficiency. <P>SOLUTION: A casing 2 having a storage space for holding a first gear 10 and a second gear 20 therein in the state that their addendums and both side surfaces are slid on each other comprises a main casing 30 holding the first gear 10 rotatably while restricting the movement in the axial direction and a gear holder 41 rotatably holding the second gear 20 and installed in the main casing 30 movably in the axial direction. A biasing member 70 biasing the gear holder 41 to the axial one end by acing a biasing force thereon and a piston 45 pressing the gear holder 41 to the axial other end against the biasing force by receiving a hydraulic force are installed in the main casing 30. Since the gear holder 41 receives a hydraulic pressure from the piston 45 against the biasing force by the biasing member 70 and is axially moved according to the hydraulic pressure, the width of engagement of the first gear 10 and the second gear 20 held on the holder 45 is changed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gear pump having a casing that holds a first gear and a second gear meshing with each other in a state where the tooth tip and both side surfaces are in sliding contact with each other, and more particularly, the first gear and the second gear. The present invention relates to a gear pump configured so that the meshing width can be changed.

  In such a gear pump, the capacity is determined by the tooth height, the tooth width, etc., and the discharge flow rate is determined by the capacity and the rotational speed of the gear (pump rotation speed). When a gear pump is used as an oil pump for supplying lubricating oil to a vehicle engine, for example, the capacity of this oil pump supplies the amount of oil necessary for lubrication even if the output of the engine that is the driving source is low and the pump speed is low. Set to be able to. For this reason, when the engine output increases and the pump speed increases, the discharge flow rate becomes excessive with respect to the required amount, and high driving force that does not meet the required amount is consumed by the oil pump, resulting in engine output loss. May be incurred.

As a gear pump that solves this problem, there is known a variable displacement gear pump that moves both or one of the drive gear and the driven gear in the axial direction to reduce the engagement width and reduce the capacity as the pump speed increases. (For example, see Patent Document 1 and Patent Document 2). In the gear pump disclosed in Patent Document 1, two side plates that sandwich the driven gear in the axial direction are provided, the support shafts of the driven gear are supported by both side plates, and an urging force is applied to the back surface of one side plate, and the other side plate. A pressing force corresponding to the discharged fluid pressure is applied to the back surface of the plate against the urging force. Thus, the driven gear sandwiched between the both side plates moves in the axial direction to a position where the pressing force and the urging force are balanced, and the meshing width with the drive gear is changed according to the discharge fluid pressure.
JP 2000-120559 A JP-A-57-73880

  Conventionally, when the driven force and the urging force are balanced and the driven gear is stopped, the pressing force and the urging force at that time act on each side plate in a direction opposite to the driven gear, and the support shaft has this pressing force. It is necessary to be supported against loads depending on the biasing force. For this reason, when the pressing force and urging force are increased and the side plate cannot fully resist this load, the side plate moves relative to the support shaft and directly presses the side surface of the driven gear. There is a possibility that a large sliding resistance is generated between the driven gear and the side plate, and the mechanical efficiency of the pump is lowered.

  The present invention has been made in view of such a problem, and provides a gear pump capable of suppressing reduction in mechanical efficiency in a gear pump configured to be able to change the meshing width of the first gear and the second gear. With the goal.

  The gear pump according to the present invention includes a first gear (for example, the drive gear 10 in the embodiment) and a second gear (for example, the driven gear 20 in the embodiment) that are provided so as to be rotatable about rotation axes parallel to each other. And a casing having an arrangement space for holding the first gear and the second gear in a state in which the tooth tips and both side surfaces are in sliding contact with each other, oil is applied to the casing in accordance with the rotation of the first gear and the second gear. In a gear pump in which a suction port for sucking in and a discharge port for discharging oil are formed, a casing includes a main casing for holding the first gear rotatably and restricting axial movement, and a second gear. It consists of a gear holder that is rotatably held and is movable in the direction of the rotation axis in the main casing. A biasing member (for example, the return spring 70 in the embodiment) that biases the holder toward one end in the rotation axis direction, and receives the hydraulic pressure to press the gear holder against the biasing force toward the other end in the rotation axis direction. A piston is provided. Then, the gear holder receives the oil pressure from the piston against the urging by the urging member, and moves in the direction of the rotation axis according to the oil pressure, so that the first gear and the second gear held by the gear holder The meshing width is changed.

  In this configuration, the gear holder is provided with a first side surface on which one side surface of the second gear is slidably contacted and an inner peripheral surface on which the tooth tip of the second gear is slidably contacted, and the piston is provided with the gear holder. A second side surface that is in sliding contact with the other side surface of the second gear, and one end portion of the shaft member that supports the second gear is supported by the piston, and the shaft member (for example, implementation) It is preferable that the other end of the driven side support shaft 25) is supported by the gear holder. Furthermore, it is preferable that at least one of the first side surface and the second side surface is formed with a recess in a part of a region where the side surface of the driven gear is slidably contacted.

  An internal oil passage is formed in the main casing to communicate the discharge port and the closed space formed on the back side with respect to the piston, and the piston is discharged by the discharge hydraulic pressure supplied to the closed space via the internal oil passage. You may comprise so that an oil pressure may be received.

  The piston is formed in a cylindrical shape and fitted to the main casing and attached, and the center of the outer peripheral surface and the center of the inner peripheral surface are decentered and a part of the outer peripheral surface is curved along the tooth tip of the first gear. It is preferable. The piston is composed of a substantially disc-shaped flat plate portion and a convex portion protruding in a cylindrical shape from the flat plate portion, and is fitted to the main casing to be attached. The center of the outer peripheral surface of the flat plate portion and the outer peripheral surface of the convex portion And a part of the outer peripheral surface of the flat plate portion may be curved along the tooth tip of the first gear.

  According to the gear pump of the present invention, the casing has a main casing that holds the first gear rotatably and restricts movement in the axial direction, and a rotating shaft in the main casing that holds the second gear rotatably. The gear holder is configured to be movably provided at the one end, and urges the gear holder to one end side in the rotation axis direction, and the gear holder moves from the piston to one end side in the rotation axis direction against urging by the urging member. The gear holder is moved in the direction of the rotation axis in the main casing in response to the oil pressure. As described above, since both the biasing force and the oil pressure opposite to each other act on the gear holder, the side surface of the second gear held by the gear holder is not pressed in the axial direction. The facing distance between the both side surfaces of the gear and the surfaces that are in sliding contact with the side surfaces does not change. For this reason, sliding resistance can be reduced and the mechanical efficiency of a gear pump can be improved.

  The gear holder is provided with a first side surface on which one side surface of the second gear is slidably contacted and an inner peripheral surface on which the tooth tip of the second gear is slidably contacted, and the piston is in contact with the gear holder to be second When the second side surface on which the other side surface of the gear is slidably contacted is provided, the second gear supported by the shaft member can be easily assembled to the gear holder and the piston. In addition, if any one of the first side surface and the second side surface is formed with a recessed portion in a part of the region that is slidably contacted with the second gear, the sliding resistance is surely reduced in the portion where the recessed portion is formed. The generation can be suppressed, and the mechanical efficiency of the gear pump can be further improved.

  By forming an internal oil passage that communicates the discharge port and the closed space formed on the back side with respect to the piston, the oil discharged to the discharge port can be supplied to the closed space, and the discharge hydraulic pressure is reduced. The pump capacity can be controlled accordingly.

  When the piston fitted and attached to the main casing is formed in a cylindrical shape, the center of the outer peripheral surface and the inner peripheral surface is decentered and a part of the outer peripheral surface is curved along the tooth tip of the first gear, It is attached to the main casing in a state where its rotation is restricted, and the piston operates stably. Similarly, a piston fitted and attached to the main casing is composed of a flat plate portion and a convex portion, and the center of the outer peripheral surface of the flat plate portion and the outer peripheral surface of the convex portion is decentered and a part of the outer peripheral surface of the flat plate portion Is curved along the tooth tip of the first gear, the piston is attached in a state in which the rotation is restricted with respect to the main casing, and the piston operates stably.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 5 show an oil pump 1 according to a first configuration example as an example of a gear pump according to the present invention. The oil pump 1 is provided in a vehicle (not shown) and uses an engine as a drive source. The oil pump 1 draws in lubricating oil stored in a tank (for example, an engine oil pan) provided in the vehicle and is connected to a lubricating oil path connected to each part of the engine. Discharge.

  The oil pump 1 is provided in a state in which a drive gear 10 and a driven gear 20 that are rotatably provided around rotation axes parallel to each other and are externally meshed with each other, and the tooth tip and both side surfaces of the drive gear 10 and the driven gear 20 are in sliding contact with each other. And a casing 2 having a pump chamber 5 that is housed and held in the outer meshing type gear pump.

  The drive gear 10 is supported on a drive side support shaft 15 that is rotationally driven by the rotational driving force of the engine output shaft transmitted through the transmission gear 9 and is rotated integrally with the drive side support shaft 15, and the driven gear 20 is The driven-side support shaft 25 is provided so as to be rotatable relative to the driven-side support shaft 25 via a bush 81 on a driven-side support shaft 25 that extends parallel to the drive-side support shaft 15. Both gears 10 and 20 are involute spur gears and have the same cross-sectional shape.

  The casing 2 includes a main casing 30 having a driving-side pump chamber 50 that rotatably supports the driving-side support shaft 15 to accommodate and hold the driving gear 10, and a lower portion of the driving-side pump chamber 50 in the main casing 30 on the driving side. A driven-side pump chamber 55 that is slidably disposed in the axial direction in a storage space 60 that extends in parallel with the shaft of the support shaft 15, supports the driven-side support shaft 25, and stores and holds the driven gear 20. And a gear holder 41 having The drive side pump chamber 50 and the driven side pump chamber 55 are vertically connected to form the pump chamber 5.

  The driving-side pump chamber 50 includes a driving-side inner peripheral surface 51 that makes sliding contact with the tooth tip 11 of the driving gear 10, a driving-side first side surface 52 that makes sliding contact with one side surface 12, and a driving-side second that makes sliding contact with the other side surface 13. It is surrounded by the side surface 53 and formed. The driven-side pump chamber 55 includes a driven-side inner peripheral surface 56 that makes sliding contact with the tooth tip 21 of the driven gear 20, a driven-side first side surface 57 that makes sliding contact with one side surface 22, and a driven-side second that makes sliding contact with the other side surface 23. It is surrounded by the side surface 58. The drive-side pump chamber 50 is communicated with the accommodation space 60 in the vertical direction, the lower end portion is opened, and the driven-side pump chamber 55 is also partially opened in the outer circumferential direction. When the gear holder 41 that houses and holds the driven gear 20 is disposed in the main casing 30, the open portion of the driven pump chamber 55 is directed upward, and the drive gear 10 and the driven gear 20 are externally meshed side by side. The

  A suction port 3 and a discharge port 4 are formed in the main casing 30 so as to be connected to the pump chamber 5, and the suction port 3 is communicated to the outside via a suction port 3 a connected to a tank. Is communicated to the outside through a discharge port 4a connected to the lubricating oil passage.

  In the oil pump 1 configured as described above, when both the gears 10 and 20 are rotated, the oil sucked into the suction port 3 from the tank enters the tooth gap, and is sent to the discharge port 4 by the rotational movement and lubricated. Pumped to the oil passage.

  The main casing 30 is assembled by fastening the case 31 and the cover 32 with the base end surface 31a of the case 31 covered with the front end surface 32a of the cover 32. A bottomed cylindrical space that opens to the base end surface 31a is formed in the upper portion of the case 31, and the drive-side pump chamber 50 has a cover 32 attached to the case 31 to close the cylindrical space in the axial direction. It is formed. That is, the inner circumferential surface of the cylindrical space forms the driving side inner circumferential surface 51, the bottom surface of the cylindrical space forms the driving side first side surface 52, and the tip surface 32 a of the cover 32 forms the driving side second side surface 53. .

  A drive side support hole 54 for supporting the drive side support shaft 15 is coaxially connected to the drive side pump chamber 50, and the drive side support shaft 15 has a tip 16 on the drive side first side surface 52. The base end portion 17 is supported by the drive side support hole 54 b on the cover 32 side that opens on the drive side second side surface 53. Thereby, the drive gear 10 is accommodated and held in the drive-side pump chamber 50 in a state where movement in the axial direction is restricted. Further, the drive side support hole 54 b on the cover 32 side is formed so as to penetrate the cover 32, and the base end portion 17 of the drive side support shaft 15 protrudes to the outside of the cover 32. A transmission gear 9 is attached to the protruding portion 17a.

  The housing space 60 in which the gear holder 41 is disposed is a bottomed cylindrical case-side space 61 formed on the case 31 side and opened to the base end surface 31a of the case 31, and the tip of the cover 32 formed on the cover 32 side. A substantially circular ring-shaped cover side space 62 opened in the surface 32a is formed in communication. The inner peripheral surface 61a of the case side space 61 and the outer inner peripheral surface 62a of the cover side space 62 have the same diameter, and the respective center axes are aligned when the case 31 and the cover 32 are assembled. The case-side space 61 is formed extending in parallel with the cylindrical space forming the drive-side pump chamber 50 and has an axial length longer than that of the cylindrical space. The lower end of the pump chamber 50 is opened. Therefore, the lower end portion of the drive side first side surface 52 that forms the drive side pump chamber 50 is curved upward along the inner peripheral surface 61 a of the case side space 61.

  The case 31 is formed with an oil space that communicates with the drive-side pump chamber 50 and the case-side space 61 and extends to the left and right with respect to the drive-side pump chamber 50 and the case-side space 61. The discharge port 4 is formed by attaching a cover 32 to the case 31 and closing these oil spaces in the axial direction.

  The gear holder 41 includes a semicircular ring-shaped accommodation portion 42 having an inner peripheral surface 42b that makes sliding contact with the tooth tip 21 of the driven gear 20, and a cylinder integrally connected to the axially proximal end side of the accommodation portion 42. The outer peripheral surface 42a of the accommodating part 42 and the outer peripheral surface 43a of the cylindrical part 43 are concentric and have the same diameter and form an integral outer peripheral surface 41a in the axial direction. The driven side support shaft 25 is supported on the gear holder 41 formed in this way by press-fitting the distal end portion 26 into the driven side support hole 59a opened in the base end surface 43b of the cylindrical portion 43, and the driven gear 20 is The side surface 22 is assembled in a state where the proximal end surface 43 b of the cylindrical portion 43 is closely opposed and the tooth tip 21 is closely opposed to the inner peripheral surface 42 a of the accommodating portion 42. The base end surface 43b of the cylindrical portion 43 is partially formed with a U-shaped depression 43c so as to surround the opening of the driven side support hole 59a. In this assembled state, the depression 43c is formed in the depression 43c. Is a portion of the side surface 22 of the driven gear 20 except for the teeth. The axial length of the accommodating portion 42 is substantially equal to the axial length of the driven gear 20. When the driven gear 20 is assembled to the gear holder 41, the tooth tip 21 is entirely accommodated in the tooth width direction (axial direction). The other side surface 23 of the driven gear 20 and the base end surface 42c of the accommodating portion 42 form substantially the same plane. Thus, the gear holder 41 accommodates and holds the driven gear 20 in the inner region of the accommodating portion 42, the inner peripheral surface 42 b of the accommodating portion 42 forms the driven inner peripheral surface 56 of the driven pump chamber 55, and the cylindrical portion 43. The base end surface 43 b forms a driven side first side surface 57 of the driven side pump chamber 55.

  The gear holder 41 that supports the distal end portion 26 of the driven side support shaft 25 and holds the driven gear 20 in this manner is fitted and accommodated in the case side space 61 from the distal end surface 43d of the cylindrical portion 43, and the case The side space 61 is slidable in the axial direction. Here, the cylindrical portion 43 is formed with a bottomed cylindrical spring chamber 43e that opens to the distal end surface 43d, and the gear holder 41 is placed in the case side space 61 in a state where the return spring 70 is accommodated in the spring chamber 43e. Is housed in. The return spring 70 has one end 71 in contact with the bottom surface 43 f of the spring chamber 43 e and the other end 72 in contact with the bottom surface 61 b of the case side space 61. It is disposed in the space 64. By this return spring 70, an urging force toward the base end side in the axial direction acts on the bottom surface 43f of the spring chamber 43e.

  Further, a piston 45 is disposed in the accommodation space 60 on the proximal end side of the gear holder 41. The piston 45 is formed into a substantially cylindrical shape with a bottom, and includes a bottom wall portion 46 that forms inner and outer bottom surfaces 46b and 46c, and a side wall portion 47 that forms a cylindrical inner peripheral surface 47b. Further, the outer peripheral surface 46a of the bottom wall portion 46 and the outer peripheral surface 47a of the side wall portion 47 are connected in the axial direction to form an integral outer peripheral surface 45a, and the piston 45 is a cover-side space having a substantially circular ring shape in cross section. It is fitted in 62 and is slidably disposed. As described above, the inner peripheral surface 61a of the cover-side space 61 and the outer inner peripheral surface 62b of the cover-side space 62 are concentric and concentric, and the piston 45 has the outer peripheral surface 45a in the case-side space 61 as well. It is slidably contacted with the inner peripheral surface 61a of the side space 61 and moved smoothly in the axial direction.

  The cover 32 has a cylindrical portion 32b surrounded by an inner inner peripheral surface 62b of the cover-side space 62 formed in a substantially cylindrical ring shape in cross section, and the piston 45 has a side wall portion 47 having a cylindrical portion 32b. Is fitted and attached. As shown in FIG. 5, the center of the inner peripheral surface 47 b of the side wall 47 is eccentric with respect to the center of the outer peripheral surface 47 a of the side wall 47. Furthermore, the outer peripheral surface 45 a of the piston 45 and the outer inner peripheral surface 62 a of the cover-side space 62 are curved downward along the addendum circle of the drive gear 10. As described above, the outer peripheral surface 47 a and the inner peripheral surface 47 b of the side wall 47 are eccentric, and the upper end portion of the outer peripheral surface 47 a is curved downward, so that the piston 45 is circumferential with respect to the cover side space 62. Is positioned, fitted and attached, and its rotation is restricted.

  The bottom wall portion 46 of the piston 45 has a driven side support hole 59b that opens to the outer bottom surface 46b, and the base end portion 27 of the driven side support shaft 25 is connected to the driven side support hole 59b on the piston 45 side. Mated. In this state where the driven side support shaft 25 is supported by the piston 45, the outer bottom surface 46 b of the piston 45 is in contact with the base end surface 42 c of the housing portion 42 of the gear holder 41 and is opposed to the other side surface 23 of the driven gear 20. Is done. Thus, the driven side support shaft 25 is supported by the piston 45 and the gear holder 41 and the piston 45 and the gear holder 41 are brought into contact with each other, whereby the driven side pump chamber 55 becomes a space closed in the axial direction. The bottom surface 46 b forms the driven side second side surface 58 of the driven side pump chamber 55.

  The outer bottom surface 46 b of the piston 45 and the base end surface 42 c of the housing portion 42 of the gear holder 41 are positioned and contacted in the circumferential direction via the knock pin 82. For this reason, the driven side support holes 59 a and 59 b on the piston 45 side and the gear holder 41 side are aligned, and the gear holder 41 is connected to the case side space 61 via the piston 45 positioned with respect to the cover side space 62. Positioned in the circumferential direction. By this positioning, the outer peripheral surface 42b of the accommodating portion 42 is slidably contacted with the lower portion of the inner peripheral surface 61a of the case side space 61, and the tooth tip 21 of the driven gear 20 accommodated and held in the driven side pump chamber 55 faces upward. As a result, the drive gear 10 accommodated and held in the drive-side pump chamber 50 and the driven gear 20 thus accommodated in the main casing 30 are externally meshed with each other.

Since the piston 45 is brought into contact with the gear holder 41 in this way, the piston 45 is also urged toward the axial base end in response to the urging force acting on the gear holder 41 toward the axial base end. The piston 45 biased toward the base end side in the axial direction is restricted from moving toward the base end side together with the gear holder 41 when the inner bottom surface 46c of the bottom wall portion 46 abuts against the end surface 32c of the cylindrical portion 32b. In this state, the outer bottom surface 46b of the piston 45 and the tip end surface 32a of the cover 32 form the same plane, and the two gears 10 and 20 are not axially displaced from each other in the tooth width direction. Engage the whole. Later, the called drive gear 10 and the mesh width meshing maximum [delta] width of the driven gear 20 [delta] _M in this case refers to a state in which the gears 10 and 20 is meshed with a maximum mesh width [delta] _M and the initial state.

  The cover side space 62 is a non-penetrating space having a bottom surface 62 c on the base end side, and a closed space 65 is formed on the base side in the axial direction with respect to the piston 45 in the cover side space 62. The cover 32 has an internal flow path 75 that allows the discharge port 4 and the closed space 65 to communicate with each other. The internal flow path 75 includes an inner peripheral surface 75 a of a groove formed by cutting out in an outer peripheral direction with respect to the outer inner peripheral surface 62 a of the cover side space 62, and the outer periphery of the piston 45 fitted in the cover side space 62. The groove is formed so as to extend in the axial direction of the cover side space 62, and one end reaches the front end surface 32 a of the cover 32 and the other end reaches the bottom surface 62 c of the cover side space 62. Has reached. One end of the internal flow path 75 formed in this way opens at the distal end surface 32 a of the cover 32 and communicates with the discharge port 4, and the other end communicates with the closed space 65.

  Hereinafter, the operation of the oil pump 1 will be described with reference to FIGS. The oil pump 1 is in the initial state shown in FIG. 3 when the engine is stopped. Even in this initial state, the urging force is applied to the gear holder 41 and the piston 45. Even in the state in which this urging force is applied, the gear holder 41 and the piston 45 are fitted and supported by the driven side support holes 59a and 59b. The driven-side support shaft 25 can be maintained in a state where it is supported by the gear holder 41 and the piston 45 against a load corresponding to the urging force, and the driven-side support shaft 25 is a shaft relative to the gear holder 41 and the piston 45. The opposing distance set between the side surfaces 22 and 23 of the driven gear 20 and the driven side first and second side surfaces 57 and 58 is not changed by relative movement in the direction.

  When the engine is started, the drive-side support shaft 15 is driven to rotate, and both gears 10 and 20 are driven to rotate. The oil stored in the tank is sucked into the suction port 3 and sent to the discharge port 4 to be lubricated. Pumped to the road. The lubricating oil passage is formed in the engine case and is configured to increase the supply hydraulic pressure as the supply oil amount increases. Further, FIG. 8 shows the pump rotational speed Ni when the engine is in an idling state. However, when the oil pump 1 is operated, the rotational speed Ni is hardly decreased, and the discharge flow rate Qi at this time is The amount of oil supplied for lubrication can be secured.

  Part of the oil discharged to the discharge port 4 is supplied to the closed space 65 through the internal flow path 75. The oil pressure of the oil supplied to the closed space 65 acts on the base end face 47 c of the side wall 47 of the piston 45. For this reason, a pressing force against the urging force of the return spring 70 is generated in the piston 45 toward the distal end side in the axial direction according to the hydraulic pressure in the closed space 65.

When the engine output increases and the pump rotation speed N reaches the first rotation speed N _A , the pressing force acting on the piston 45 is substantially balanced with the urging force. Therefore, when the pump rotational speed N exceeds the first rotational speed N _A, the piston 45 to compress the spring 70 back to move axially distal end side with the gear holder 41 against the urging force. The piston 45 and the gear holder 41 are moved to a position where the pressing force is balanced with the urging force. At this time, as shown in FIG. 7, the tip of the piston 45 is positioned in the case-side space 61 and overlaps the drive gear 10 vertically, but the upper end is curved downward along the tip circle. Therefore, interference between the drive gear 10 and the piston 45 is avoided.

  When the gear holder 41 and the piston 45 are thus moved toward the distal end in the axial direction, the driven gear 20 is moved in the axial direction while meshing with the drive gear 10, and the meshing width δ of both the gears 10, 20 becomes short. Pump capacity is reduced. In the oil pump 1 of this configuration example, as shown in FIG. 8, due to the balance between the increase in the pump rotational speed N and the decrease in the pump capacity that occurs when the pump rotational speed N increases and the meshing width δ shortens, As a result, the discharge flow rate Q is stabilized regardless of the increase or decrease of the pump rotational speed N. Thereby, even if the output of the engine increases, excessive oil is not discharged from the oil pump 1.

  The case 31 is formed with a communication hole 39 that opens to the bottom surface 61b of the case-side space 61 and allows the space 64 to communicate with the outside. The space 64 is always maintained at atmospheric pressure regardless of the volume change. . For this reason, the gear holder 41 and the piston 45 are smoothly moved according to the urging force and the pressing force. The outer peripheral surface 41 a of the gear holder 41 is recessed toward the inner peripheral side, leaving both axial ends, and only the both axial ends are in sliding contact with the inner peripheral surface 61 a of the case-side space 61. As described above, since the gear holder 41 has a small contact area with the inner peripheral surface 61a of the case side space 61, the sliding resistance is reduced and the gear holder 41 is smoothly moved in the housing space 60.

When the pump rotational speed N reaches a second rotational speed N _B, as shown in FIG. 6, the distal end surface 43d of the cylindrical portion 43 of the gear holder 41 abuts against the bottom surface 61b of the case side space 61. Therefore, the pump rotational speed N is even beyond the second rotational speed N _B, the gear holder 41 and the piston 45 is moved in the axial direction distal end side is regulated, does not become shorter than the mesh width [delta] _m in this case. Hereinafter, the meshing width δ _m at this time is also referred to as a minimum meshing width.

  As described above, in the oil pump 1 of this configuration example, the casing 2 that accommodates and holds the drive gear 10 and the driven gear 20 includes the main casing 30 that holds the drive gear 10 while allowing the drive gear 10 to rotate and restrict axial movement. The driven gear 20 is rotatably held, and is constituted by a gear holder 41 provided in the main casing 30 so as to be movable in the direction of the rotation axis. Further, a biasing force toward the axial base end side is applied to the gear holder 41. A pressing force against the urging force is applied to the piston 45 that is always in contact with the gear holder 41 by this urging. As described above, both the urging force and the pressing force act on the gear holder 41 that houses and holds the driven gear 20.

Therefore, the gear holder when the pump rotational speed N is between the first rotational speed N _A and the second rotational speed N _B, without movement is regulated by balance between the pressing force and the biasing force in the accommodating space 60 41 The piston 45 stops at a predetermined position. At this time, the urging force and the pressing force cancel each other out due to the contact between the gear holder 41 and the piston 45, so that the driven side support shaft 25 has a load corresponding to the urging force and the pressing force. Does not act, and the driven gear 20 does not move in the driven pump chamber 55 in the axial direction.

Incidentally, in a state where the engine is stopped, although the biasing force on the gear holder 41 and the piston 45 is acting, the biasing force, at which to begin to be shortened mesh width [delta] from the maximum mesh width [delta] _M It resists the pressing force, and a large load does not act on the driven-side support shaft 25 supported by press-fitting, and the driven-side support shaft 25 moves relative to the gear holder 41 and the piston 45 in the axial direction. Absent. Further, the gear holder 41 and the piston 45 are moved in the axial direction by increasing / decreasing the pressing force, but the driven side support shaft 25 is supported against the inertial force generated by the acceleration / deceleration before the movement starts and stops. There is no relative movement in the axial direction with respect to the gear holder 41 and the piston 45. Furthermore, the mesh width [delta] of the second rotational speed N _B Beyond the gears 10 and 20 is minimized mesh width [delta] _m, the gear holder 41 and the piston 45 is supported by the bottom surface 61b of the case-side space 61, the axial direction In this case, a vertical drag from the bottom surface 61b corresponding to the difference between the pressing force and the urging force acts, but the load acting according to the vertical drag is not large, and the driven support shaft 25 is connected to the gear holder in the same manner as described above. There is no relative movement in the axial direction with respect to 41 and the piston 45.

  Accordingly, the opposed distance between the driven gear 20, the side surfaces 22, 23 of the driven gear 20, and the driven side first side surface and the second side surfaces 57, 58 of the driven side pump chamber 55 does not change. The sliding resistance can be reduced compared to the above, and the mechanical efficiency of the oil pump 1 can be improved.

  Further, when the driven gear 20 is rotatably accommodated and held in the state in which the side surfaces 22 and 23 are slidably contacted with each other, the surface of the driven gear 20 adjacent to and opposed to the piston 45 (second driven side second) is provided. By forming the side surface 58), the assembly of the driven side support shaft 25 is simplified, and the driven gear 20 can be easily accommodated and held in the driven side pump chamber 55. Further, by forming a recess 43 c in a part of the driven first side surface 57 where the one side 22 of the driven gear 20 is closely opposed, the portion where the recess 43 c is formed is one side of the driven gear 20. Contact with 22 can be reliably avoided. For this reason, the sliding resistance is reduced and the oil pump 1 with good mechanical efficiency can be provided.

  Further, in this configuration example, the driven gear 20 is configured to be movable in the axial direction by receiving the discharge hydraulic pressure on the base end surface 47c of the piston 45 and applying a pressing force against the urging force of the return spring 70. Thereby, the variable control of the pump capacity using the discharge hydraulic pressure is performed, and the control for stabilizing the discharge flow rate Q can be easily performed regardless of the increase or decrease of the pump rotation speed N. In order to perform this variable control, an internal flow path 75 is formed in the main casing 30 to communicate the discharge port 4 and the closed space 65 on the proximal side in the axial direction with respect to the piston 45. Here, the main casing 30 in which the discharge port 4 is formed is configured by attaching a cover 32 so as to cover the base end surface 31 a of the case 31, and an oil space that opens to the base end surface 31 a of the case 31 is formed. A discharge port 4 is formed by being covered with a cover 32. For this reason, since the internal flow path 75 only needs to be formed inside the cover 32, the internal flow path 75 can be easily formed, and a seal structure that is necessary when formed across a plurality of members. Is also omitted.

  Next, the oil pump 101 of the second configuration example will be described with reference to FIGS. In the oil pump 101, the shape of the piston 145 is changed with respect to the first configuration example, and the same components as those in the first configuration example are denoted by the same reference numerals and redundant description is omitted.

  The piston 145 has an outer peripheral surface 146a that is pivoted from the center of the wall portion 146 having the same shape as the outer peripheral surface 46a of the bottom wall portion 46 of the piston 45 of the first configuration example and the base end surface 146c of the wall portion 146. A cylindrical convex portion 147 projecting toward the direction base end side is integrally formed. A cover-side space 162 into which the piston 145 is fitted is formed inside the cover 132, and the cover-side space 162 includes a cylindrical large-diameter space 166 that opens to the front end surface 132 a of the cover 132 and a large-diameter space 166. And a cylindrical small-diameter space 167 opened at the center of the bottom surface 166b. The piston 145 is disposed in the cover side space 162 with the convex portion 147 fitted in the small diameter space 167 and the wall portion 146 fitted in the large diameter space 166. Further, the outer peripheral surface 146a of the wall portion 146 is eccentric with respect to the central axis of the convex portion 147, and the upper end portion is curved downward. For this reason, the piston 145 is positioned and fitted in the circumferential direction with respect to the cover-side accommodation space 162, and the rotation is restricted.

  In the accommodation space 60, the base end surface 42 c of the accommodation portion 42 of the gear holder 41 and the distal end surface 142 b of the wall portion 146 of the piston 145 are brought into contact with each other via the knock pin 82, and the circumferential direction with respect to the cover side space of the gear holder 41 Positioning with respect to is performed. In the initial state, the base end surface 146c of the wall 146 is brought into contact with the bottom surface 166b of the large-diameter space 166, and the movement of the gear holder 41 and the piston 145 toward the base end side in the axial direction is restricted. At this time, the closed space 165 is formed on the proximal side with respect to the convex portion 147 in the small diameter space 167. An internal oil passage 175 formed inside the cover 132 connects the closed space 165 and the discharge port 4 and guides the discharged oil to the closed space 165.

Even when the oil pump 101 is operated and the pump rotation speed N exceeds the first rotation speed N _A and the piston 145 is slid to the front end side in the axial direction, the piston 145 remains at the upper end portion of the outer peripheral surface 146a of the wall portion 146. Is curved downward, so that interference with the drive gear 10 is avoided. Therefore, the axial length of the wall 146 is set to be longer than the slidable distance between the gear holder 41 and the piston 145 (that is, the difference between the maximum engagement width δ _M and the minimum engagement width δ _m ). Further, the axial length of the convex portion 147 is also set longer than the slidable distance so that the piston 145 and the cover-side space 162 are not disengaged by moving to the front end side in the axial direction.

  Further, a recess 146d is formed on the distal end surface 146b of the piston 145 with which the other side surface 23 of the driven gear 20 is closely opposed, similarly to the base end surface 43b of the cylindrical portion 43 of the gear holder 41 in the above configuration example. In addition, as shown in FIG. 13, this hollow part 146d is formed in the position which opposes the part except the tooth | gear part in the other side surface 23 of the driven gear 20. As shown in FIG.

  In this configuration example, the same operation as in the first configuration example is performed, and the facing distance between the side surfaces 22 and 23 of the driven gear 20 and the driven side first and second side surfaces 57 and 58 of the driven pump chamber 55 is changed. Therefore, the oil pump 101 with improved mechanical efficiency can be provided. In addition, a depression 146d is formed on the piston 145 side having the driven second side surface 58, and the sliding resistance is further reduced.

  The piston 145 of this configuration example is for avoiding interference with the drive gear 10 and for preventing the piston 145 and the cover-side space 162 from being disengaged with the movement toward the distal end in the axial direction. It is necessary to set the axial length of both the wall portion 146 and the convex portion 147 to be longer than the slidable distance. On the other hand, in the piston 45 of the first configuration example, since the outer peripheral surfaces 46a and 47a of the bottom wall portion 46 and the side wall portion 47 are integrally connected, at least the axial length of the side wall portion 47 is set longer than the slidable distance. The axial length of the bottom wall portion 46 is set regardless of the slidable distance. Accordingly, the piston 45 of the first configuration example is smaller in size than the oil pump in the sliding direction of the piston in the second configuration example. An oil pump having a large variable width of the pump capacity can be configured.

  As mentioned above, although embodiment of the gear pump which concerns on this invention was described, this invention is not restricted to the said structure. For example, the present invention can be applied not only to the externally connected dual gear pump but also to an externally connected triple (tandem) gear pump in which two driven gears are externally meshed with the drive gear. The same effect can be obtained by accommodating and holding both or one in the gear holder. The drive gear may be moved in the axial direction, and the transmission mechanism is not limited to a gear train, and may be a chain mechanism or a belt mechanism. Further, the oil pump is not limited to an oil pump that is provided in a vehicle and used to supply lubricating oil, and may be used for other applications in other devices such as an oil pump that supplies hydraulic oil to a hydraulic actuator. The present invention can also be applied to other fluid pumps such as an air pump and a water pump.

It is a top view of the oil pump of the 1st example of composition shown as an embodiment of the gear pump concerning the present invention. It is a sectional side view of the oil pump of the 1st example of composition shown along arrow AA of Drawing 1, and is a figure showing the initial state of an oil pump. It is sectional drawing of the oil pump of the 1st structural example shown along the arrow III-III of FIG. 1, FIG. 2, and is a rear view of a case and a gear holder. It is sectional drawing of the oil pump of the 1st structural example shown along arrow IV-IV of FIG. 1, FIG. 2, and is sectional drawing of a case and a gear holder. It is sectional drawing of the oil pump of the 1st structural example shown along the arrow VV of FIG. 1, FIG. 2, and is sectional drawing of a cover and a piston. It is a sectional side view of the oil pump of the 1st example of composition shown along arrow AA of Drawing 1, and is a sectional side view of the oil pump which shows the state where the meshing width of a drive gear and a driven gear is the minimum meshing width. It is. It is sectional drawing of the oil pump of the 1st structural example shown along arrow VI-VI of FIG. It is a figure explaining the action | operation of the oil pump of a 1st structural example, Comprising: It is explanatory drawing which shows the relationship between pump rotation speed, a discharge flow rate, and the meshing width of a gear. It is a fragmentary sectional side view of the oil pump of the 2nd example of composition. It is sectional drawing of the oil pump of the 2nd structural example shown along arrow XX of FIG. 9, and is a front view of a cover and a piston.

Explanation of symbols

1,101 Oil pump 2 Casing 4 Discharge port 5 Pump chamber (installation space)
10 Drive gear (first gear)
20 Driven gear (second gear)
25 Driven support shaft (shaft member)
30 Main casing 41 Gear holder 42 Housing part 43 Cylindrical part 43c, 146d Depression 45 Piston 50 Drive side pump chamber 55 Drive side pump chamber 56 Drive side inner peripheral surface 57 Drive side first side surface 58 Drive side second side surface 60 Storage space 65 Closed space 70 Return spring (biasing member)
75 Internal oil passage

Claims (6)

A first gear and a second gear, which are rotatably provided around rotation axes parallel to each other and mesh with each other, and an arrangement for holding the first gear and the second gear in a state where the tooth tips and both side surfaces are in sliding contact with each other. In a gear pump comprising a casing having a space, wherein a suction port into which oil is sucked and a discharge port from which oil is discharged is formed in the casing according to the rotation of the first gear and the second gear.
The casing holds the first gear rotatably and restricts movement in the axial direction, and holds the second gear rotatably, and can move in the main casing in the rotational axis direction. And a gear holder provided in
A biasing member that biases the gear holder toward one end in the direction of the rotation axis by applying a biasing force in the main casing, and a direction of the rotation axis against the biasing force by receiving oil pressure. And a piston that presses to the other end side of the
The gear holder is held by the first gear and the gear holder by receiving the oil pressure from the piston against the urging force of the urging member and moving in the direction of the rotation axis according to the oil pressure. A gear pump characterized in that the meshing width with the second gear is changed. The gear holder has a first side surface on which one side surface of the second gear is slidably contacted, and an inner peripheral surface on which a tooth tip of the second gear is slidably contacted,
The piston has a second side surface that is in contact with the gear holder and in which the other side surface of the second gear is in sliding contact.
2. The gear pump according to claim 1, wherein one end portion of a shaft member that supports the second gear is supported by the piston, and the other end portion of the shaft member is supported by the gear holder.   3. The recess according to claim 2, wherein at least one of the first side surface and the second side surface has a recess formed in a part of a region where the side surface of the second gear is slidably contacted. Gear pump. An internal oil passage is formed in the main casing to communicate the discharge port and a closed space formed on the back side with respect to the piston.
The gear pump according to claim 1, wherein the piston is configured to receive the oil pressure by a discharge hydraulic pressure supplied to the closed space via the internal oil passage.   The piston is formed in a cylindrical shape and is fitted and attached to the main casing. The center of the outer peripheral surface and the center of the inner peripheral surface are eccentric, and a part of the outer peripheral surface is the first. The gear pump according to claim 2, wherein the gear pump is curved along a tooth tip of the gear.   The piston has a substantially disc-shaped flat plate portion and a convex portion protruding in a cylindrical shape from the flat plate portion, and is fitted and attached to the main casing. The center of the surface and the center of the outer peripheral surface of the convex portion are eccentric, and a part of the outer peripheral surface of the flat plate portion is curved along the tooth tip of the first gear. Item 5. The gear pump according to Items 2 to 4.

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