JP3978304B2 - Gear pump or gear motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gear pump or a gear motor with reduced pulsation.
[0002]
[Prior art]
The gear pump shown in FIG. 2 has a pair of gears 2 and 3 that engage with each other in its body bore 1.
The gears 2 and 3 are fixed to shafts 4 and 5, respectively, and these shafts 4 and 5 are rotatably supported via bearings 6 and 7 fixed to shaft holes formed in a body (not shown). .
[0003]
A drive source (not shown) is connected to one shaft 4.
When one shaft 4 is rotated by the drive source, the gear pump configured as described above rotates while the gear 2 and the gear 3 are engaged with each other.
When the gear 2 rotates with the one shaft 4 in the direction of arrow A, the other gear 3 rotates in the direction of arrow B. At this time, the pressure oil is carried from the suction chamber 8 by the tooth spaces of both the gears 2 and 3 and discharged from the discharge chamber 9.
Also, the gear motor has the same configuration as the gear pump described above, and rotates the gear by supplying pressure oil to extract the rotational force from the shaft on which the rotating gear is fixed.
[0004]
[Problems to be solved by the invention]
If there is a gap, a so-called backlash, in the meshing portion of the pair of gears 2 and 3 that mesh and rotate as described above, rattling occurs and pulsation occurs. This pulsation causes fluctuations in the discharge flow rate of the gear pump and also causes noise.
Further, in the case of a gear motor, it causes noise and uneven rotation.
Therefore, the smaller the backlash, the better. However, in order to reduce the backlash to zero, the dimensions of each part, such as the shape and dimensions of the gear tooth surface, and the assembly position, must be managed with high accuracy.
[0005]
However, it is very difficult to manage the dimensions to make backlash zero.
This is because the shaft and gear positions of the gear pump and the gear motor are deviated from those at the time of assembly due to the pressure oil during operation. It is very difficult to control the dimensions assuming this deviation.
This will be described below using the gear pump shown in FIG.
[0006]
When the gear pump is operated and pressure oil is sent from the blowing chamber 8 side to the discharge chamber 9 side, a pressure distribution is generated in the body bore 1. Then, high pressures in the directions of arrows C and D act on both gears 2 and 3 in the portion immediately before the discharge stroke of the pressure oil, respectively.
As described above, when the gears 2 and 3 are pressed in the directions of the arrows C and D, the gears 2 and 3 move in the directions of the arrows C and D together with the shafts 4 and 5. This is because a slight gap is provided between the bearings 6 and 7 and the shafts 4 and 5 in order to rotatably support the shafts 4 and 5. FIG. 2 shows a state where the gears 2 and 3 are moved by the oil pressure.
[0007]
As shown in FIG. 2, the gears 2 and 3 are moved in the directions of the arrows C and D, and the shafts 4 and 5 are settled in a state where they are in contact with the bearings 6 and 7.
In the case of a gear motor, the oil pressure that moves the gear from the pressure oil supply side to the discharge side acts, and the shaft settles in a state where the shaft abuts against the bearing.
In other words, the shape of the tooth surface and the dimensions of other parts must be controlled so that the backlash is zero when the shafts 4 and 5 are moved by the hydraulic pressure and abut against the bearings 6 and 7. It is very difficult.
[0008]
Accordingly, an object of the present invention is to provide a gear pump or gear motor in which backlash is zero or close to zero and pulsation and noise are reduced without strict dimensional control.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a gear pump or a gear motor including a pair of gears that mesh with each other, a pair of shafts fixed to the pair of gears, and a bearing that rotatably supports the shafts. A wear layer is provided on both or one of the meshing tooth surfaces of this gear, and this wear layer is characterized in that its thickness is made larger than the initial gap between the shaft and the bearing .
The second invention is based on the first invention and is characterized in that the wear layer is a coating layer of a fixed lubricant.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a gear pump according to the present invention.
In the gear pump of this embodiment, a coating layer 10 of a solid fluidizing material is provided on the meshing tooth surfaces of a pair of gears 2 and 3 that mesh and rotate. The solid fluidizing material is made of molybdenum disulfide, tetrafluoroethylene, or the like, and thereby forms a soft coating layer 10 on the meshing tooth surfaces of the gears 2 and 3.
Except for the provision of the coating layer 10, the configuration is the same as that of the conventional gear pump.
The coating layer 10 is a wear layer of the present invention.
[0011]
At the time when the gear pump is assembled and the operation is started, as shown in FIG. 1, there is a gap in the meshing portion of the gears 2 and 3 with a gap secured between the shafts 4 and 5 and the bearings 6 and 7. Dimension that cannot be set.
On the other hand, also in the gear pump of this embodiment, oil pressure in the directions of arrows C and D acts on the gears 2 and 3 during operation as in the conventional example.
Therefore, when the operation is started, each of the gears 2 and 3 receives oil pressure in the directions of arrows C and D, and moves until the shafts 4 and 5 hit the bearings 6 and 7 while the soft coating layer 10 is worn. At the start of operation of the gear pump, the gaps d1 and d2 between the shafts 4 and 5 and the bearings 6 and 7 disappear.
[0012]
At this time, since the oil pressure indicated by the arrows C and D is supported by the bearings 6 and 7, the wear of the coating layer 10 formed on the tooth surface is stopped. And the tooth surface shape of each gear 2 and 3 is decided, and the meshing part settles in a balanced state.
Further, if the thickness of the coating layer 10 on the tooth surface is made larger than the initial gap between the shafts 4 and 5 and the bearings 6 and 7, the shafts 4 and 5 can be connected to the inner periphery of the bearings 6 and 7 during operation. The coating layer 10 is easily worn until it hits and settles down, so that a stable state is achieved quickly.
[0013]
As described above, in this embodiment, the coating layer 10 provided on the meshing tooth surfaces of the gears 2 and 3 is worn during the initial operation, and the position shift of the shafts 4 and 5 due to the oil pressure is absorbed. Therefore, even when the backlash of the meshing portion is made zero, it is not necessary to perform dimensional management in consideration of the displacement due to the oil pressure during operation. Therefore, the backlash of the gear pump or the gear motor can be zero or close to zero without performing strict dimensional control as in the prior art. Therefore, pulsation can be prevented.
[0014]
Further, since the meshing tooth surfaces mesh with each other via the solid lubricant, the meshing becomes smooth, and in the case of zero backlash, the occurrence of noise can be suppressed even if the backlash is not zero.
In this embodiment, the coating layer 10 is formed of a solid lubricant, but a wear layer made of a material that easily wears even if not a lubricant is formed on the meshing tooth surface of each gear. Then, zero backlash can be realized as in the above embodiment.
Further, in the above embodiment, the wear layer is formed on the meshing tooth surfaces of both of the pair of gears 2 and 3, but the wear layer may be provided only on either the gear 2 or the gear 3. A similar effect can be obtained.
[0015]
【The invention's effect】
According to the first invention, the backlash can be brought close to zero without strict control of the dimensions of each member. Therefore, pulsation and noise can be reduced.
In addition, since the thickness of the wear layer is larger than the initial gap between the shaft and the bearing, the wear layer easily wears until the shaft hits the inner periphery of the bearing and settles during operation. It becomes stable quickly.
According to the second aspect of the present invention, it is possible to smoothen the rotation of the meshing gears and further reduce noise.
[Brief description of the drawings]
FIG. 1 shows a gear pump according to an embodiment of the present invention.
FIG. 2 is a view showing a conventional gear pump.
[Explanation of symbols]
1 Body bore 2 Gear 3 Gear 4 Shaft 5 Shaft 6 Bearing 7 Bearing 10 Coating layer

Claims (2)

In a gear pump or gear motor comprising a pair of gears that rotate in mesh with each other in a body bore, a pair of shafts fixed to each of the pair of gears, and a bearing that rotatably supports both shafts. A gear pump or gear motor in which a wear layer is provided on both or one of the meshing tooth surfaces, and the wear layer has a thickness larger than an initial gap between the shaft and the bearing .   The gear pump or gear motor according to claim 1, wherein the wear layer is a coating layer of a fixed lubricant.

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