JPS6238559B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention introduces low pressure oil around a gear shaft,
This invention relates to a gear pump that lubricates the gear.

(Conventional Gear Pump) A gear pump disclosed in Japanese Patent Publication No. 49-43605 has been known as a pump of this type.

In this gear pump, the outlet side of the lubrication path communicates with an expansion chamber that increases the confined volume in the meshing portion of the gears, and the inlet side of the lubrication path communicates with the suction hole side of the pump. This expansion chamber becomes a negative pressure when its volume is increased, and this negative pressure causes the lubricating oil in the circulation path to be sucked out into the expansion chamber.

This lubricating oil suction method has a fatal drawback as a bearing when used in a gear pump, but in order to clarify this drawback, we will first explain the principle of general journal bearings in Section 9. This will be explained based on the diagram.

Figure 9 shows the oil film distribution when the shaft J is rotating in the direction of the arrow in the bearing hole B and the shaft load is acting in the W direction, and the area around the bearing is at atmospheric pressure. It shows.

In other words, the lubricating oil supplied from the oil supply groove S forms an oil film R in a range of 180 degrees + α from the oil supply groove S toward the rotation direction, but this oil film R becomes a contracting flow. produces positive pressure. The axial load of the shaft J is supported by the positive pressure generated in the oil film R.

Further, in a range other than the range where the oil film R is formed (180 degrees - α), negative pressure is created due to the expanding flow, resulting in a cavitation state.

However, in gear pumps, the pressure around the bearings is generally lower than atmospheric pressure due to piping resistance, strainer fluid resistance, etc. Therefore, the range in which the oil film R is formed is narrower in the gear pump than in the general case.

In gear pumps where the range of oil film R formation is narrower than in the general case, if a conventional suction system is adopted, the negative pressure around the bearing will become even greater, so as shown in Figure 8, In addition, the range of oil film formation becomes narrower.

In this way, when the formation range of oil film R becomes narrower,
Since the axial load W cannot be supported by oil film pressure alone, this suction type low pressure lubrication has the disadvantage that seizure is likely to occur.

(Objective of the present invention) The purpose of the present invention is to provide a gear pump that forcibly pushes low-pressure oil flowing from a suction hole into a low-pressure lubrication path, reduces negative pressure around a bearing, and prevents seizure, etc. Make it.

(Embodiment of the present invention) A housing a is formed with circular holes 1 and 2 that communicate with each other, and gears 3 and 4 are housed in the circular holes 1 and 2.

The bushes 5 to 8, which are fitted into the circular holes 1 and 2 on both sides of the gears 3 and 4, have curved sides and abut the flat parts of the chord parts of the bushes 5a, 6a, 7a,
8a, and the buttons 5 that are paired with each other
By abutting the abutting surfaces of 6, 7, and 8, the paired bushes fit snugly into the circular holes 1 and 2.

And the shaft holes 5b, 6b of the bushes 5 to 8,
The shafts 9 to 12 of the gears 3 and 4 are inserted into the shafts 7b and 8b, thereby holding the gears 3 and 4 at predetermined positions.

Since the bushes 5, 6 and 7, 8 are symmetrical, the pair of bushes 5, 6 will be explained below.

Therefore, each of the bushes 5 and 6 is formed with a notch stepped portion 13 and 14 (see FIG. 3) on the side surface facing the gears 3 and 4 and on the suction side of the pump. By abutting the abutting surfaces 5a, 6a of both bushes 5, 6, the stepped portions 13, 14 together form a concave portion 16 (see FIGS. 2 and 4) directly connected to the suction hole 15. .

Lubricating oil introduction holes 19 and 20 are formed at positions adjacent to this concave portion 16, and these lubricating oil introduction holes 19 and 20 are located at positions where the gears have completely meshed. The concave portion 16 is located near the dedendum circle of the gear and is provided with check walls 17 and 18 that are at the same level as the side surfaces of the bushes 5 and 6.
surrounded on the sides. And this introduction hole 19,2
0 is directly connected to the annular grooves 21, 22 formed in the shafts 9, 10, and the annular grooves 21, 22 are connected to the shaft holes 5b, 22, respectively.
The slits 6b are in communication with the slits 23 and 24 formed in the slits 6b.

The slits 23 and 24 reach the opposite side of the bushes 5 and 6 from the side facing the gears, so the lubricating oil introduction holes 19 and 20 extend through the annular grooves 21 and 22 and the slits 23 and 24. It communicates with the outside of the shafts 9 and 10 via the shaft.

The outside of the shaft 910 and the rear cover 2 of the housing a
Gaps 26 and 27 are formed between the bushes 5 and 5, and these gaps 26 and 27 communicate with each other through recesses 28 and 29 (see FIG. 5) formed in both the bushes 5 and 6.

Grooves 30 and 31 are formed in the abutting surfaces 5a and 6a of the bushes 5 and 6, and these grooves 30 and 31 (see FIG. 3)
6 are matched by abutting against each other, and together they form a lubricating oil outlet hole 32 (see FIGS. 2, 4, and 5). This lead-out hole 32 has one end in the recess 16 and the other end in the recess 28, 29.
Openings are made at the connecting portions of each.

When the gears 3 and 4 are rotated in the direction of the arrow in FIG. 2, low pressure oil from a pump (not shown) is sucked into the suction hole 15. At this time, gear 3,
4 is rotating in a direction opposite to this suction flow, so the suction flow and the gear collide. This collision generates a very large amount of kinetic energy in the suction flow.

As shown in Fig. 6, this suction flow with large kinetic energy is forced into the lubricating oil introduction holes 19 and 20 along the roots of the gears 3 and 4, and the flow reflected at the roots is reversed. Stopping wall 17,
It collides with the inside of 18, and also the lubricating oil introduction hole 1.
9, 20, and the lubricating oil introduction hole 1.
The low pressure oil flowing into check walls 17 and 18
The force of the fluid that collides with and flows in one after another pushes it in further and further.

The suction flow forced into the lubricating oil introduction holes 19, 20 in this way is as follows: annular grooves 21, 22 → slits 23, 24 → gaps 26, 27 → recesses 28, 29 →
The lubricating oil is forcibly fed into the low-pressure lubrication path formed by the lubricating oil outlet hole 32. Therefore, in the process of passing through the slits 23 and 24, this low-pressure oil returns to the concave portion 16 while lubricating and cooling the journal.

In this way, the kinetic energy generated when the suction flow collides with the gears 3 and 4 is used to force the low-pressure oil into the lubrication path, which reduces the negative pressure around the bearings and reduces the negative pressure around the bearings. As shown in FIG. 7, the formation range of the oil film R can be maintained broadly.
Therefore, the range in which the oil film R is formed is reduced, and problems such as seizure, which occur in the conventional case, are eliminated.

Note that in this embodiment, the lubricating oil outlet hole 32
the return side opening of is located within the recessed portion 16;
This reduces the influence of negative pressure that occurs when the confined volume of the gear increases. However, the force for pushing the low-pressure oil into the lubricating oil introduction holes 19 and 20 becomes considerably large due to the kinetic energy.
Even if the opening of the lubrication outlet hole 32 is affected by negative pressure to some extent, there is no need to worry about the pressure around the bearing becoming low. Therefore, the position of the opening of the lubrication outlet hole 32 does not need to be strictly determined.

Reference numerals 33 and 34 in the figure are sealing members, and the space between them is a high-pressure area, and the inside of the sealing member 34 is a low-pressure area to balance the pressing force of the bushes 5 and 6 against the gears 3 and 4. , numeral 35 is a discharge hole.

Further, in the above embodiment, the grooves 30 and 31 are formed in the abutting surfaces 5a and 6a of the bushes 5 and 6, respectively.
However, the groove may be formed only in one of the bushes, and the hole formed by the groove may be one that serves as a part of the lubricating oil circulation path. It is not limited to the lubricating oil outlet hole as in the above embodiment.

(Structure of the present invention) The structure of the present invention is such that a pair of gears is housed inside the housing, and a bushing is provided on the side surface of the gear to support the shaft thereof, while a lubricating oil introduction hole is provided on the low pressure side directly connected to the suction hole. A gear pump having one end open and configuring a lubrication path in which low pressure oil introduced from the one end opening of the lubricating oil introduction hole is guided back to the low pressure side via the journal part of the gear, which faces the gear. A concave portion directly connected to the suction hole is formed on one side of the bushing, and a position adjacent to the concave portion where both the gears have completely engaged, and near the dedendum circle of the gear. , is characterized in that a lubricating oil introduction hole is formed and the concave side of the lubricating oil introduction hole is surrounded by a check wall.

(Effects of the present invention) In this invention, the flow of low-pressure oil that flows in from the suction hole collides with the gear and has large kinetic energy, and is forcibly pushed into the lubricating oil introduction hole. can be made smaller, and the range of oil film formation becomes larger accordingly. Since the oil film is formed over a wide area, the shaft load can be supported by the oil film pressure, and problems such as seizure will not occur.

In addition, since the concave side of the lubricating oil introduction hole is surrounded by a check wall, the suction flow reflected from the teeth of the gear collides with this check wall and is pushed into the lubricating oil introduction hole. Greater efficiency.

[Brief explanation of the drawing]

Drawings 1 to 6 show an embodiment of the present invention, in which Fig. 1 is a longitudinal sectional view, Fig. 2 is a sectional view taken along the line - - of Fig. 1, and Fig. 3 is a cross-sectional view of a pair of bushes. One perspective view, FIG. 4 is a perspective view of the pair of bushes butted against each other, FIG. 5 is a sectional view taken along the - line in FIG. Figure 7 is an explanatory diagram showing the oil film distribution around the bearing, Figure 8 is an explanatory diagram showing the oil film distribution in a conventional gear pump, and Figure 9 is an explanatory diagram showing the oil film distribution in a typical journal bearing. FIG. a...Housing, 3, 4...Gear, 5-8...
...button, 9-12...shaft, 15...suction hole,
16... Concave portion, 17... Check wall, 19... Lubricating oil introduction hole.

Claims (1)

[Claims] 1 A pair of gears is housed in the housing, and a bushing is provided on the side of the gear to support the shaft.One end of the lubricating oil introducing hole is opened on the low pressure side directly connected to the suction hole, and the lubricating oil introducing hole is In a gear pump that has a lubrication path in which low-pressure oil introduced from an opening at one end is guided back to the low-pressure side via the journal portion of the gear, one side of the bushing facing the gear is directly connected to the suction hole. A lubricating oil introduction hole is formed adjacent to this recess, at a position where the meshing of both the gears is completely completed, and near the dedendum circle of the gear. A gear pump with a check wall surrounding the concave side of the lubricating oil introduction hole.