JP2022120971A - Gear bearing structure of external gear pump - Google Patents

Abstract

To provide a gear bearing structure of an external gear pump which can inhibit leakage of a fluid to discharge the fluid with stable discharge rate accuracy.SOLUTION: In an external gear pump, a pair of gear is housed within a pump body. A suction chamber is formed at one side of an engagement part of the pair of gears, and a discharge chamber is formed at the other side. The pair of gears rotates to send a fluid from the suction chamber to the discharge chamber along a circumferential direction. A gear bearing structure of the external gear pump includes a cylindrical bush F which forms a lubricating liquid film with a rotary shaft of at least one of the pair of gears to hold the rotary shaft in a rotatable manner. One end P3 of the bush F faces a high pressure (discharge chamber side) liquid and the other end faces a low pressure (suction chamber side) liquid. One end (high pressure side) of a discharge groove 107 formed on an inner peripheral surface 100 of the bush F is closed and the other end (low pressure side) is open. The discharge groove 107 has a length which is longer than or equivalent to a half of a length of the bush F as seen in a direction of the rotary shaft.SELECTED DRAWING: Figure 5

Description

TECHNICAL FIELD The present disclosure relates to a gear bearing structure in an external gear pump that pumps out fluid with a pair of gears.

Patent Document 1 discloses an external gear pump. A circumscribed gear pump comprises a pair of drive and driven gears within a pump body. Gear teeth are formed on the outer circumferences of the drive gear and the driven gear. The drive gear and the driven gear are sandwiched by side plates from both sides in the axial direction while being meshed with each other. A suction chamber for sucking fluid (liquid) is formed on one side of the meshing portion of the drive gear and the driven gear, and a discharge chamber for discharging the fluid is formed on the other side of the meshing portion.

The drive gear and the driven gear begin to mesh on the discharge chamber side and disengage on the suction chamber side. Fluid enters between the disengaged gear teeth, and as the gear teeth rotate, the fluid is held between the gear teeth and the inner surface of the pump body and sent circumferentially to the discharge chamber. Each gear shaft (rotating shaft) of the driving gear and the driven gear is rotatably held by a bush. A lubricating liquid film is formed between the inner peripheral surface of the bush and the outer peripheral surface of the rotating shaft by the fluid sent by the gear pump. That is, the fluid sent by the gear pump also functions as lubricating oil. In the circumscribed gear pump disclosed in Patent Document 1, a lubricating groove for supplying lubricating liquid for forming a lubricating liquid film on a lubricating sliding surface between the inner peripheral surface of the bush and the outer peripheral surface of the rotating shaft is formed in the bush. is formed on the inner peripheral surface of the The lubricating groove is formed parallel to the rotating shaft.

Japanese Patent Application Laid-Open No. 2004-204952

In the circumscribed gear pump disclosed in Patent Document 1, one end of the bush faces the high pressure side (gear side) of the fluid and the other end faces the low pressure side. A lubricating fluid groove that supplies lubricating fluid to the lubricating sliding surface is open at one end of the bush and not open at the other end. The lubricating fluid groove positively supplies high-pressure fluid from one end side of the bush to the lubricating sliding surface. Lubricating oil forming a lubricating film moves to the low pressure side of the other end of the bushing. By not allowing the other end of the bush to open, the outflow of lubricating oil from the other end of the bush is suppressed. However, since the fluid discharged by the circumscribed gear pump is used as a lubricating liquid, when the amount of lubricating oil (fluid) supplied to the lubricating sliding surface increases due to an increase in the number of revolutions of the gear, etc., the other end of the bush will The outflow of lubricating oil (fluid) from the gear pump is also increased, which reduces the efficiency of the gear pump. In addition, when precision is required for the discharge amount of the pump, the precision of the discharge amount is also lowered. An object of the present disclosure is to provide a gear bearing structure for an external gear pump that can suppress fluid leakage and discharge fluid with stable accuracy.

In the gear bearing structure of the circumscribed gear pump according to the present disclosure, a suction chamber is formed on one side of a meshing portion of a drive gear and a driven gear that are rotatably housed inside a pump body, and a discharge chamber is formed on the other side of the meshing portion. A gear bearing structure for an external gear pump in which a chamber is formed and rotation of the driving gear and the driven gear sends fluid from the suction chamber to the discharge chamber along the circumferential direction, wherein at least the driving gear or the driven gear A cylindrical bush is provided for rotatably holding the rotating shaft by forming a lubricating film of the fluid between the rotating shaft and one of the rotating shafts. One end of the bush is in sliding contact with at least one of the drive gear and the driven gear via a lubricating liquid film of the fluid, and the fluid in the suction chamber is introduced to the other end of the bush. It is On the inner peripheral surface of the bush, a discharge groove for discharging the fluid forming the lubricating film between the rotating shaft and the inner peripheral surface from the other end of the bush is formed in the direction of the rotating shaft. formed along the The discharge groove is closed without being opened at the one end of the bush, is open at the other end of the bush, and has a length of at least half the length of the bush in the direction of the rotation axis. have.

The gear bearing structure may further include a flow path for introducing fluid from the discharge chamber on the inner peripheral surface, and an end of the flow path may open onto the inner peripheral surface.

Here, the end of the flow path may be arranged on the opposite side of the discharge groove with respect to the rotating shaft.

According to the gear bearing structure of the circumscribed gear pump according to the present disclosure, it is possible to suppress fluid leakage and discharge fluid with stable discharge amount accuracy.

1 is a cross-sectional view of a circumscribed gear pump having a gear bearing structure according to a first embodiment; FIG. FIG. 2 is a sectional view taken along the line II-II in FIG. 1; FIG. 2 is a cross-sectional view taken along line III-III in FIG. 1; It is a perspective view of a bush in a first embodiment. It is the perspective view which looked at the said bush from the other side. FIG. 4 is a perspective view showing a part (circular convex portion) of the midplate of the circumscribed gear pump; FIG. 4 is a perspective view showing a high-pressure supply passage formed inside the pump body of the circumscribed gear pump;

An embodiment of the gear bearing structure of the circumscribed gear pump will be described below with reference to the drawings.

A circumscribed gear pump (hereinafter simply referred to as gear pump) P having a gear bearing structure according to the embodiment is used as a pump for feeding liquid fuel (hereinafter also simply referred to as fuel) to an engine. In the gear pump P, this fuel is also used as a lubricating liquid (hereinafter also referred to as lubricating oil) for lubricating each part of the gear pump P. That is, in this embodiment, the fuel and the lubricating oil are the same. In the following, depending on the context, the terms fuel (fluid that is pumped) and lubricant (fluid that provides lubrication) are both used.

As shown in FIGS. 1 and 2, the gear pump P has a pair of gears G within a pump body B. As shown in FIGS. The pump body B is composed of a main body B1, a side plate B2, a mid plate B3 and an end plate B4 in this embodiment. A gear housing chamber 1 for housing a pair of gears G in mesh is formed inside the main body B1. The gear storage chamber 1 has a figure-of-eight cross section perpendicular to the rotation axis O of the gear G. As shown in FIG.

The gears G will be described later in detail, but each gear G has a plurality of gear teeth formed on its outer circumference, and the tips of the gear teeth slide against the inner peripheral surface of the gear storage chamber 1 via a lubricating oil film. Contact. An intake chamber 2I for sucking fuel from the outside is formed on one side of the constricted portion of the gear storage chamber 1, that is, the meshing portion of the gear G, and a discharge chamber 2O for discharging fuel is formed on the other side. there is The gear pump P is a positive displacement pump, and the pressure PH in the discharge chamber 2O is higher than the pressure PL in the suction chamber 2I (PL<PH) due to flow path resistance on the side of the discharge chamber 2O.

A side plate B2 and a mid plate B3 are fixed to the main body B1 by bolts 3 and the like from both sides in the direction of the rotation axis O (bolts on the side plate B2 side are not shown). Both ends of each rotating shaft GS of the gear G are rotatably held by a side plate B2 and a mid plate B3 via a cylindrical bush F, which will be described later. Although the bushes F will also be described in detail later, each bush F has a lubricating liquid film (oil film) formed between its inner peripheral surface 100 (see FIGS. 4 and 5) and the outer peripheral surface of the rotating shaft GS. Construct a fluid bearing (slide bearing) that utilizes A ring-shaped end plate B4 is fixed to the outer surface of the mid plate B3. A rotating shaft GS (GS1) of one of the pair of gears G (first gear G1) extends outside from the center of the end plate B4.

One of the pair of gears G (first gear G1) is a drive gear rotated by external power. A spline is formed at the end of the rotating shaft GS1 of the first gear G1 (see FIG. 7), and the first gear G1 is connected to the drive source via the spline. The other of the pair of gears G (second gear G2) is a driven gear that rotates with the rotation of the first gear G1. The first gear G1 and the second gear G2 rotate in opposite directions to each other as indicated by arrows in FIG. The gear profiles (shape and number of gear teeth, etc.) of the first gear G1 and the second gear G2 are the same. The fuel in the suction chamber 2I is conveyed along the circumferential direction (along the inner peripheral surface of the gear storage chamber 1) while being retained between the gear teeth of the first gear G1 and the second gear G2. and sent to the discharge chamber 2O.

A rotating shaft GS1 of the first gear G1 is a solid cylinder and is integrally formed with the first gear G1 so as to pass through the first gear G1. Oil seals S are provided between the rotating shaft GS1 and the side plate B2 and between the rotating shaft GS1 and the mid-plate B3 to prevent leakage of lubricating oil while allowing rotation of the rotating shaft GS1. there is On the other hand, the rotating shaft GS2 of the second gear G2 is a hollow cylinder, but is also formed integrally with the second gear G2 so as to pass through the second gear G2. Both ends of the rotating shaft GS2 are held by a side plate B2 and a mid plate B3 via bushes F, respectively. Lubricating oil can flow through the inside of the rotating shaft GS2.

A portion of the rotating shaft GS1 of the first gear G1 on the mid plate B3 side is held by a first bush F11, and a portion on the side plate B2 side is held by a second bush F12. Similarly, the portion of the rotating shaft GS2 of the second gear G2 on the mid plate B3 side is held by a first bush F21, and the portion on the side plate B2 side is held by a second bush F22. The first bushing F11 of the first gear G1 and the first bushing F21 of the second gear G2 are, as shown in FIG. It is constructed symmetrically with respect to a plane of symmetry parallel to the center O). However, the first bushing F11 of the first gear G1 and the first bushing F21 of the second gear G2 are slightly different in the shape of the low-pressure side recess 101 and the high-pressure side recess 102a, which will be described later.

Symmetrically configured first bushings F11 and F21 are described below with reference to the first bushing F11 shown in FIGS. The first bushing F11 has a cylindrical shape, and a stepped portion is formed on its outer peripheral surface. A ring-shaped second surface P2 is formed on the stepped portion. That is, the first bushing F11 is formed with a large-diameter portion and a small-diameter portion bordering on the second surface P2, and the outer diameter of the large-diameter portion is equal to the gear outer diameter of the first gear G1 (Fig. 2 reference). A lubricating groove 103 is formed on the outer peripheral surface of the large-diameter portion to facilitate sliding of the rotation shaft GS in the axial direction.

A portion of the outer peripheral surface of the large-diameter portion of the first bushing F11 is formed as a contact plane 104 . The first bushes F11 and F21 are arranged in the gear storage chamber 1 on the side of the mid plate B3 with the contact plane 104 in contact with the contact plane 104 of the first bush F21 of the second gear G2. Therefore, the first bushes F11 and F21 are housed in the gear housing chamber 1 so as not to rotate. The plane containing the contact plane 104 is the aforementioned plane of symmetry of the first bushings F11 and F21.

The second surface P2 is a plane perpendicular to the rotation axis GS1 (rotational axis O1), and corresponds to the first surface P1 (see FIG. 6) of the circular projection 6 (see FIG. 1) of the mid plate B3 (pump body B). See). The inner diameter of the inner peripheral surface 100 of the first bushing F11 is substantially equal to the outer diameter of the rotating shaft GS1 of the first gear G1, and a lubricating oil film is formed between the inner peripheral surface 100 and the rotating shaft GS1. That is, the inner peripheral surface 100 is in sliding contact with the outer peripheral surface of the rotating shaft GS1 via the lubricating oil film. A recess 105 is formed on the inner peripheral surface 100 to supply high-pressure lubricating oil between the inner peripheral surface 100 and the outer peripheral surface of the rotating shaft GS1. The recess 105 is arranged in the center of the inner peripheral surface 100 in the direction of the rotation axis O1 so that the lubricating oil supplied from the recess 105 spreads efficiently between the inner peripheral surface 100 and the outer peripheral surface of the rotation shaft GS1. there is

The recess 105 has a substantially rectangular internal space, but its bottom surface is formed as a curved concave surface. The recess 105 is formed by electric discharge machining or cutting. An introduction port 106a, which is the inlet of the in-bush supply passage 106 for high-pressure lubricating oil, is opened on the second surface P2 described above. The high-pressure supply passage 5 (see FIG. 7) for supplying high-pressure lubricating oil to the introduction port 106a will be described later in detail. Inside the first bush F11, an in-bush supply passage 106 is formed that communicates between the recess 105 and the introduction port 106a. An orifice 106b having a narrower inner diameter is formed at the recess 105 side end of the in-bush supply passage 106 . Further, the in-bush supply passage 106 penetrates to the outer peripheral surface of the first bushing F11, and a secondary port 106c is opened on the outer peripheral surface. By penetrating the in-bush supply passage 106 to the outer peripheral surface of the first bush F11, the in-bush supply passage 106 connecting the inlet 106a and the recess 105 can be easily formed.

Specifically, first, a part of the in-bush supply passage 106 is formed by using a large-diameter drill from the position where the secondary port 106 c on the outer peripheral surface is opened toward the vicinity of the recess 105 . A small diameter drill is then used to extend the in-bush supply passage 106 to the vicinity of the recess 105 (below the bottom). Further, the orifice 106b is formed by drilling or electrical discharge machining using a very small diameter drill. Further, the remaining portion is formed using a drill from the position where the introduction port 106a is formed on the second surface P2. The formation order of the introduction port 106a, the orifice 106b and the secondary port 106c does not necessarily have to be the order described above. Either the recess 105 or the in-bush supply passage 106 may be formed first.

The first bushing F11 has a third surface P3 facing the first gear G1. The third surface P3 is also a plane perpendicular to the rotation axis GS1 (the rotation axis O1), and is in sliding contact with the side surface of the first gear G1 via a lubricating oil film. A low-pressure side recess 101 is formed from the third surface P3 to the outer peripheral surface and a portion of the contact plane 104 on the side of the suction chamber 2I. The curved concave inner surface of the low pressure side concave portion 101 is part of the suction chamber 2I. A high pressure side concave portion 102a is formed from the third surface P3 to the outer peripheral surface and a portion of the contact plane 104 on the discharge chamber 2O side. The curved concave inner surface of the high pressure side concave portion 102a serves as the inner surface of the discharge chamber 2O. A tapered portion 102b extends in the circumferential direction from the high pressure side recessed portion 102a. The tapered portion 102b forms a tapered surface between the third surface P3 and the outer peripheral surface. The first bushing F11 has a fourth surface P4 facing the midplate B3. The fourth plane P4 is also a plane perpendicular to the rotation axis GS1 (the rotation axis O1).

On the inner peripheral surface 100 of the first bushing F11, the lubricating oil of the lubricating oil film formed between the outer peripheral surface of the rotating shaft GS1 and the inner peripheral surface 100 of the first bushing F11 is discharged to the fourth surface P4 side. A discharge groove 107 is also formed for the purpose. One end of the discharge groove 107 on the side of the fourth surface P4 communicates with the low-pressure lubricating oil (fuel) in the suction chamber 2I through the interior of the mid plate B3. By circulating the lubricating oil by discharging the lubricating oil through the discharge groove 107, the lubricating sliding surface between the outer peripheral surface of the rotating shaft GS1 and the inner peripheral surface 100 of the first bushing F11 is cooled. One end of the discharge groove 107 on the side of the third surface P3 does not reach the third surface P3 and is closed. On the other hand, the other end of the discharge groove 107 on the side of the fourth surface P4 reaches the fourth surface P4 and is open.

High-pressure lubricating oil supplied from the recess 105 to between the inner peripheral surface 100 of the first bushing F11 and the rotating shaft GS is discharged from the end (low-pressure side) of the discharge groove 107 on the side of the fourth surface P4. The discharge groove 107 is formed parallel to the rotation axis GS1 (rotational axis O1), and has a length of at least half the length of the first bushing F11 in the direction of the rotation axis GS1 (rotational axis O1). ing. The inner surface of the discharge groove 107 is formed as a concave curved surface. The discharge groove 107 is located on the opposite side of the recess 105 with respect to the rotation axis O1.

A plurality of (twelve in this embodiment) spring housing holes 108 are formed at equal intervals along the circumferential direction on the second surface P2. The spring housing hole 108 is formed parallel to the rotation axis GS1 (rotational axis O1). A coil spring 109 is housed in each spring housing hole 108 . The coil spring 109 is housed in the spring housing hole 108 in a state of being compressed by a spring seating surface inside the spring housing hole 108 and a first surface P1 (to be described later) facing the second surface P2. Therefore, the first bushing F11 is biased away from the first surface P1 by the coil spring 109 (and the high pressure of the lubricating oil). Note that the coil spring 109 is not shown in the spring housing hole 108 in FIG.

As described above, the second surface P2 of the first bushing F11 (F21) faces the first surface P1 of the pump body B (mid plate B3). The first plane P1 is also a plane perpendicular to the rotation axis GS (rotational axis O). As shown in FIG. 6, the first surface P1 is formed as an end surface of the circular protrusion 6 of the midplate B3. A circular protrusion 6 protrudes from the surface of the midplate B3 facing the main body B1. A first housing hole H1 for housing the end of the first bushing F11 and a second housing hole H2 for housing the end of the first bushing F21 are formed on the first surface P1 of the circular projection 6. . The first housing hole H1 is a through hole having a step (annular bottom surface) on the inner peripheral surface, and the rotation shaft GS1 of the first gear G1 passes through the through hole. The second storage hole H2 is a bottomed hole.

The first housing hole H1 houses the small diameter portion of the first bushing F11. Therefore, the second surface P2, which is the boundary between the small diameter portion and the large diameter portion of the first bushing F11, faces the first surface P1. Similarly, the second housing hole H2 houses the small diameter portion of the first bushing F21. Therefore, the second surface P2, which is the boundary between the small diameter portion and the large diameter portion of the first bushing F21, also faces the first surface P1. The coil springs 109 in the compressed state described above are in contact with the seating surfaces in the spring housing holes 108 formed in the first surface P1 and the second surface P2, and move the first bushings F11 and F21 away from the first surface P1. , that is, toward gear G.

Seal grooves 7 are formed on the outer peripheral surface of the circular convex portion 6 and on the inner peripheral surfaces of the first housing hole H1 and the second housing hole H2 to accommodate an O-ring for preventing leakage of lubricating oil. there is FIG. 6 also shows a high-pressure supply passage 5 for supplying high-pressure lubricating oil between the second surface P2 and the first surface P1. The high-pressure supply path 5 will be described later in detail, but the open end 5c, which is the outlet end of the high-pressure supply path 5 of the present embodiment, is branched into a T shape, and one end is connected to the second surface P2 of the first bush F11. and the other end faces the second surface P2 of the first bushing F21. That is, the open end 5c faces the second surfaces P2 of both the first bushing F11 and the first bushing F21. The high-pressure lubricating oil supplied between the first surface P1 and the second surface P2 urges the first bushes F11 and F21 together with the coil springs 109 .

The first bushing F11 (F21) arranged on the mid-plate B3 side has been described above. In this embodiment, the second bush F12 (F22) arranged on the side plate B2 side is partially different from the first bush F11 (F21). The spring housing hole 108 and the coil spring 109 are not arranged at the position of the second surface P2 of the second bushing F12 (F22). The second bushing F12 has a shape substantially symmetrical to the first bushing F11 with respect to the first gear G1, and the second bushing F22 has a shape substantially symmetrical to the first bushing F21 with respect to the second gear G2. have. High-pressure lubricating oil (fuel) in the discharge chamber 2O is supplied from the high-pressure supply port 4H (see FIG. 1) to the inner peripheral surface 100 of the second bush F12 (F22). On the other hand, low-pressure lubricating oil (fuel) in the suction chamber 2I is supplied from the low-pressure supply port 4L (see FIG. 1) to the fourth surface P4 of the second bushing F12 (F22) facing the side plate B2. High-pressure lubricating oil supplied between the inner peripheral surface 100 of the second bushing F12 (F22) and the rotating shaft GS is discharged from the end (low pressure side) of the discharge groove 107 on the side of the fourth surface P4. The fourth surface P4 of the second bushing F22 facing the side plate B2 and the fourth surface P4 of the first bushing F21 facing the mid plate B3 communicate with each other through the inside of the rotation shaft GS2 of the second gear G2. there is

The second bushes F12 and F22 are housed on the side plate B2 side of the gear housing chamber 1 . Here, as described above, the first bushes F11 and F21 are urged in a direction away from the first surface P1 (leftward in FIG. 1), that is, toward the pair of gears G. As shown in FIG. Since the second surfaces P2 of the second bushes F12 and F22 abut against the stepped portion of the main body B1, their positions in the direction of the rotation axis GS (rotational axis O) are determined. The pair of gears G are pushed by the biased first bushings F11 and F21, and their side surfaces come into sliding contact with the third surfaces P3 of the second bushings F12 and F22 via lubricating oil films. As described above, the pair of gears G are also in sliding contact with the third surfaces P3 of the first bushings F11 and F21 biased on the opposite side surfaces thereof via the lubricating oil film. Thus, the sliding states of the gear G, the first bushes F11 and F21, and the second bushes F12 and F22 are stabilized.

The lubricating oil is applied to the above-described sliding parts (between the peripheral surface of the gear G and the pump body B, between the side surface of the gear G and the third surface P3, and between the outer peripheral surface of the rotating shaft GS and the inner peripheral surface of the bush F). surface 100). Lubricating oil can also move through a minute gap between the bushing F and the pump body B. Inside the gear pump P, there are places where the lubricating oil (fuel) is at high pressure and places where it is at low pressure, and the lubricating oil tries to move from the place with high pressure to the place with low pressure. If high-pressure lubricating oil is stably supplied to a certain place, that place can maintain a stable high-pressure state. In this embodiment, high-pressure lubricating oil is stably supplied to the inner peripheral surface 100 to increase the allowable value of the load acting on (the rotation axis GS of) the pair of gears G (that is, to increase the allowable load). ). By increasing the allowable load, it is possible to prevent seizure due to running out of oil on the sliding surface even if a large load acts. Equalizing the pressure distribution in the lubricating oil film (at high pressure) contributes to increasing the allowable load.

Here, pressure regions formed in the circumferential direction of the pair of gears G will be described with reference to FIG. As described above, the pressure PH within the discharge chamber 2O is higher than the pressure PL within the suction chamber 2I (PL<PH). Accordingly, a low pressure region L is formed facing the suction chamber 2I along the inner periphery of the gear housing chamber 1 corresponding to the outer periphery of the first gear G1 and the second gear G2. This low pressure region L corresponds to the low pressure side recess 101 described above. On the other hand, a high pressure region H is formed facing the discharge chamber 20 along the inner periphery of the gear storage chamber 1 corresponding to the outer periphery of the first gear G1 and the second gear G2. This high pressure area H corresponds to the high pressure side concave portion 102a described above. Here, the high pressure side concave portion 102a is enlarged in the circumferential direction by the tapered portion 102b. Therefore, the high pressure region H is expanded to the tapered portion 102b.

As described above, the fuel (lubricating oil) is accumulated between the gear teeth of the gear G and carried in the circumferential direction. During this time, the pressure of the fuel (lubricating oil) between the gear teeth is low if it is in the low pressure region L, and is high if it is in the high pressure region H. A pressure transition region T is formed between the low pressure region L and the high pressure region H, where the pressure of the fuel (lubricating oil) gradually shifts from low pressure to high pressure via the lubricating oil film of the sliding portion. The pressure transition region T can also be called a boost region. Thus, the low pressure area L, the pressure transition area T and the high pressure area H are defined corresponding to the outer circumference of the gear G. FIG.

That is, a pressure distribution is formed along the outer circumference of the gear G. As shown in FIG. Due to this pressure distribution, a pressure distribution may also be formed in the lubricating oil film between the outer peripheral surface of the rotating shaft GS and the inner peripheral surface 100 of the bush F. However, in this embodiment, as described above, high-pressure lubricating oil is supplied between the outer peripheral surface of the rotating shaft GS and the inner peripheral surface 100 of the bush F via the recess 105 . The recess 105 is located in the low pressure area L opposite the drain groove 107 (see FIG. 3) located in the high pressure area H. FIG. Therefore, high-pressure lubricating oil can be supplied to the lubricating oil film in the low-pressure region L so as to eliminate the pressure distribution of the lubricating film described above. In particular, the recess 105 is arranged on the rotation leading side of the rotating shaft GS in the low pressure region L, and the high-pressure lubricating oil supplied to the lubricating oil film is easily supplied to the entire low pressure region L by the rotation of the rotating shaft GS. .

Although the discharge groove 107 is arranged in the high pressure region H, its end on the gear G (third surface P3) side is closed. Here, if the discharge groove 107 penetrates from the third surface P3 side to the fourth surface P4, the lubricating oil passes through the discharge groove 107 from the high-pressure third surface P3 (gear) side to the low-pressure first surface P3. There is a possibility that the efficiency of the gear pump will decrease because it will flow to the P4 side of the four surfaces. However, in the present embodiment, the end portion of the discharge groove 107 on the third surface P3 side is closed, and leakage of lubricating oil (fuel) from the discharge groove 107 from the high pressure side to the low pressure side is suppressed. Furthermore, in this embodiment, the first bushes F11 and F21 are pushed toward the side surface of the gear G by the pressure of the high-pressure lubricating oil supplied between the first surface P1 and the second surface P2 and the coil spring 109. energized. Therefore, leakage of lubricating oil (fuel) from the high pressure side to the low pressure side through the lubricating oil film between the third surface P3 and the side surface of the gear G is suppressed. Therefore, the discharge groove 107 only discharges the high-pressure lubricating oil supplied between the rotating shaft GS and the inner peripheral surface 100 via the in-bush supply passage 106 and the recess 105 for circulation cooling. efficiency.

On the other hand, the introduction port 106a, which is the inlet of the in-bush supply passage 106 for supplying high-pressure lubricating oil to the recess 105, is arranged in the high-pressure region H. As shown in FIG. High-pressure lubricating oil is introduced from the introduction port 106a, but since the introduction port 106a is arranged in the high-pressure region H, the pressure of the supplied lubricating oil does not decrease. In addition, the introduction port 106a is arranged in the high-pressure region H on the trailing side of the rotating shaft GS. Here, the in-bush supply passage 106, which connects the recess 105 in the low-pressure region L and the inlet 106a in the high-pressure region H, is formed inside the first bushing F11 (F21). can cause However, by arranging the recess 105 on the rotation leading side in the low pressure region L and arranging the introduction port 106a on the rotation trailing side in the high pressure region H, the in-bush supply passage 106 is formed linearly and as short as possible. It is possible to suppress pressure loss and supply lubricating oil at a higher pressure from the recess 105 .

In this embodiment, the in-bush supply passage 106 penetrates to the outer peripheral surface of the first bushing F11, and the secondary port 106c is opened on the outer peripheral surface. By doing so, it is easy to linearly form (drill) the in-bush supply passage 106 . Since the secondary port 106c is arranged in the high pressure region H, the pressure of the lubricating oil supplied through the in-bush supply passage 106 does not decrease. The in-bush supply passage 106 communicates the introduction port 106a and the recess 105, and a branch passage leading to the secondary port 106c is not necessarily required. However, the branched passage leading to the sub-port 106c facilitates the machining of the in-bush supply passage 106 and does not cause a pressure drop, so there is no need to close the sub-port 106c (branched passage).

The orifice 106 b formed at the recess 105 side end of the in-bush supply passage 106 prevents the lubricating oil in the recess 105 from being pushed back into the in-bush supply passage 106 . That is, it is possible to suppress variations in thickness of the lubricating oil film formed between the outer peripheral surface of the rotating shaft GS and the inner peripheral surface 100 of the bush F in the circumferential direction. Therefore, it is possible to suppress fluctuations in the thickness of the lubricating oil film and increase the allowable load of the rotating shaft GS and the bush F.

Next, the high-pressure supply passage 5 for supplying high-pressure lubricating oil to the introduction port 106a will be described with reference to FIG. The high-pressure supply passage 5 also supplies high-pressure lubricating oil between the first surface P1 and the second surface P2. Since a minute gap is formed between the first surface P1 and the second surface P2 by urging the first bushings F11 and F21 by the coil spring 109, this minute gap is a reservoir for high-pressure lubricating oil. function as As a result, high-pressure lubricating oil can be stably supplied from the open end 5c to the introduction port 106a. A supply port 8 for supplying high-pressure lubricating oil to the high-pressure supply passage 5 is provided on the outer surface of the pump body B (mid plate B3). The supply port 8 is connected by a pipe (not shown) to a discharge port 9 for discharging high-pressure (pressure PH) fuel (lubricating oil) in the discharge chamber 2O. A main passage 5 a of the high-pressure supply passage 5 is formed linearly from the supply port 8 toward the axially outer position of the circular projection 6 . The main path 5a is formed perpendicular to the rotation axis GS (rotational axis O).

A secondary channel 5b of the high-pressure supply channel 5 is connected to the tip of the main channel 5a (see also FIG. 6). The secondary path 5b is formed parallel to the rotation axis GS (rotational axis O), that is, perpendicular to the first plane P1 (and the second plane P2). The secondary passage 5b passes through the circular convex portion 6, and as described above, the opening end 5c, which is the outlet of the high-pressure supply passage 5, is formed at the tip of the secondary passage 5b. As described above, the open end 5c of the present embodiment is formed in a T shape in plan view on the first surface P1, and the inlet 106a of the first bush F11 and the inlet 106a of the first bush F21 facing both.

In order to form the high-pressure supply passage 5, the position of the supply port 8 on the outer surface of the mid plate B3 is shifted to the axially outer position of the circular convex portion 6 (and the position of the first housing hole H1 and the second housing hole H1 when viewed from the axial direction). A large-diameter drill is used to form a portion of the main passage 5a toward the center of the housing hole H2. Next, the main passage 5a is extended using medium and small diameter drills in sequence. Also, the secondary path 5b is drilled from the first surface P1 toward the tip of the main path 5a. The shape of the opening (that is, opening end 5c) of the secondary path 5b on the first surface P1 is formed into the above-described T-shape by cutting or electrical discharge machining. Such processing of the opening end 5c is also easy because it can be performed on the flat first surface P1. The order of formation of the main path 5a, the secondary path 5b and the open end 5c does not necessarily have to be the order described above. The reason why the inner diameter is gradually narrowed to form the high-pressure supply passage 5 and the in-bush supply passage 106 is that it is difficult to machine a long supply passage at once with a small-diameter drill. However, according to the high-pressure supply passage 5 whose inner diameter gradually narrows, pressure loss can be suppressed.

The high-pressure supply passage 5 may communicate the opening end 5c and the discharge chamber 2O only inside the pump body B. Further, the high-pressure supply path 5 and the in-bush supply path 106 are flow paths for introducing fluid (lubricating oil/fuel) from the discharge chamber 20 to the inner peripheral surface 100 .

According to the gear bearing structure according to the present embodiment, the discharge groove 107 is located on the third surface P3 side of the first bushings F11 and F21 (lubricant film side of sliding contact with gear G/low pressure side of fluid). One end is closed without being opened. On the other hand, the discharge groove 107 is open at the other ends of the first bushes F11 and F21 on the side of the fourth surface P4 (high pressure side of the fluid). In addition, the discharge groove 107 has a length of half or more of the length of the first bushes F11 and F21 in the direction of the rotation axis GS. Since the end of the discharge groove 107 on the gear G side is closed, the discharge groove 107 from the gear G side (third surface P3 side) of the first bushes F11 and F21 to the opposite side (fourth surface P4 side) is formed. Movement of fluid through is inhibited. Therefore, the discharge groove 107 does not reduce the efficiency of the gear pump.

Here, even if the pressure on the high pressure side (discharge chamber 20 side) of the fluid rises as the rotational speed of the gear G rises, since one end of the high pressure side of the discharge groove 107 is closed, the discharge groove 107 is passed through. Movement of the fluid from the high pressure side to the low pressure side is stably suppressed. Therefore, the fluid can be ejected with stable ejection amount accuracy. Since the discharge groove 107 has a length of at least half the length of the first bushes F11 and F21, lubricating oil between the rotating shaft GS and the inner peripheral surface 100 can be efficiently discharged. , the lubricated sliding surface can be effectively cooled. If the length of the discharge groove 107 is less than half the length of the first bushings F11 and F21, the lubricating oil on the third surface P3 side is not sufficiently discharged, and the lubricating sliding surface cannot be cooled effectively.

Further, according to the gear bearing structure of this embodiment, the flow path (the high-pressure supply path 5 and the in-bush supply path 106) for introducing the fluid (fuel/lubricating oil) from the discharge chamber 20 to the inner peripheral surface 100 of the bush F is provided. further formed. An end portion (recess 105 ) of the flow path is opened on the inner peripheral surface 100 . That is, high-pressure fluid is directly supplied to the inner peripheral surface 100 through the channel. The discharge groove 107 sequentially discharges part of the lubricating liquid film formed by the high-pressure fluid supplied through the flow path. The discharged fluid is replenished through the flow path described above. Therefore, it is possible to reliably cool the lubricating sliding surface by circulating the fluid forming the lubricating liquid film while stably forming a good lubricating liquid film.

Furthermore, according to the gear bearing structure of the present embodiment, the end portion (recess 105) of the above-described flow path (in-bush supply path 106) is arranged on the opposite side of the discharge groove 107 with respect to the rotation axis GS. . The high-pressure fluid supplied to the inner circumferential surface 100 from the end of the flow path (recess 105) spreads over the entire lubricating sliding surface and is then discharged from the discharge groove 107 on the opposite side. Therefore, a good lubricating liquid film is formed on the entire lubricated sliding surface, and the fluid that has received heat from the entire sliding surface can be discharged from the discharge groove 107 . Therefore, the sliding surface of the bearing is effectively cooled, and the temperature rise of the bearing is suppressed. In addition, since the film thickness variation of the lubricating oil film can be suppressed, the allowable load of the rotating shaft GS and the bush F can be increased.

Although several embodiments have been described, modifications or variations of the embodiments are possible based on the above disclosure. All components of the above embodiments and all features recited in the claims may be extracted individually and combined as long as they are not inconsistent with each other.

For example, in the above-described embodiment, high-pressure lubrication is applied from the recess 105 to the inner peripheral surface 100 via the passages (the high-pressure supply channel 5 and the in-bush supply channel 106) for introducing the fluid from the discharge chamber 2O to the inner peripheral surface 100. supplied oil. However, it is possible to supply high-pressure lubricating oil to the inner peripheral surface 100 without forming such a flow path or recess 105 . As described above, lubricating oil (fuel) tends to move from a high-pressure location to a low-pressure location via a lubricating oil film. It is also possible to supply high-pressure lubricating oil to the inner peripheral surface 100 via the . Even in such a case, since the end of the discharge groove 107 on the side of the third surface P3 is closed, lubricating oil (fuel ) from the high pressure side to the low pressure side is suppressed. Therefore, the exhaust groove 107 does not reduce the efficiency of the gear pump. In this case also, since the first bushings F11 and F21 are urged toward the side surface of the gear G, lubricating oil (fuel) flows through the lubricating oil film between the third surface P3 and the side surface of the gear G. Movement is controlled so as not to be excessive.

P External gear pump B Pump body G Gear G1 First gear (drive gear)
G2 second gear (driven gear)
GS (GS1, GS2) Rotation shaft F Bushings F11, F21 First bushing 100 (F11, F21 of first bushing) Inner peripheral surface 105 Recess (end of flow path for introducing fluid from discharge chamber 2O to inner peripheral surface 100 )
106 Intra-bush supply channel (channel for introducing fluid from discharge chamber 2O to inner peripheral surface 100)
107 discharge groove 2I suction chamber 2O discharge chamber 5 high-pressure supply passage (flow passage for introducing fluid from discharge chamber 2O to inner peripheral surface 100)

Claims (3)

A suction chamber is formed on one side of a meshing portion of a drive gear and a driven gear that are rotatably housed inside a pump body, and a discharge chamber is formed on the other side of the meshing portion. A gear bearing structure for an external gear pump that sends fluid along the circumferential direction from the suction chamber to the discharge chamber by rotation of the
a cylindrical bush that rotatably holds the rotating shaft by forming a lubricant film with the fluid between the rotating shaft of at least one of the driving gear and the driven gear;
One end of the bush is in sliding contact with at least one of the drive gear and the driven gear via a lubricating liquid film of the fluid, and the fluid in the suction chamber is introduced to the other end of the bush. and
A discharge groove for discharging the fluid forming the lubricating film between the rotating shaft and the inner peripheral surface from the other end of the bush is formed on the inner peripheral surface of the bush in the direction of the rotating shaft. formed along the
The discharge groove is closed without being opened at the one end of the bush, is open at the other end of the bush, and has a length of at least half the length of the bush in the direction of the rotation axis. A gear bearing structure for a circumscribed gear pump, comprising: A gear bearing structure for an external gear pump according to claim 1,
further comprising a channel for introducing fluid from the discharge chamber to the inner peripheral surface,
A gear bearing structure for a circumscribed gear pump, wherein an end of the flow path is open on the inner peripheral surface. A gear bearing structure for an external gear pump according to claim 2,
A gear bearing structure for a circumscribed gear pump, wherein the end of the flow path is arranged on the opposite side of the discharge groove with respect to the rotating shaft.

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