JPH112191A - Gear pump or motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate production of noise caused by containment of liquid without causing deterioration in pump discharge quantity, large-sizing, or increase in tooth work precision. SOLUTION: In setting a contact ratio to 1, tooth form curves to form outer form of teeth 4, 5 are cut inward at specified positions, tips 4x, 5x are left as they are, and cut positions and the tips 4x, 5x are set to be continuous along lines inside original tooth form curves, so containment of liquid will not occur, the reduction in theoretical discharge quantity is prevented, and that a large change of the contact ratio like that in the case of adjusting a cut-down position in shaving, etc., can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a vehicle, a construction machine,
The present invention relates to a gear pump or a motor widely used in various fields including agricultural and forestry machines, fishing machines, and the like (hereinafter, a pump will be described as a representative).

[0002]

2. Description of the Related Art FIG. 3 shows a conventional general gear pump. In this case, a case 3 is constituted by a body-integrated front cover 1 and a rear cover 2, and a pair of gears 4 and 5 are housed in a pair of gears 4 and 5 in an eyeglass-shaped hole 1 x provided in the front cover 1. Side plates 6 and 7 are attached to the side surfaces of the gears 4 and 5 to close the volume space. The front cover 1 and the rear cover 2 are provided with bearing holes 1a, 2a, and the rotating shafts 4a, 5a to which the gears 4, 5 are attached are rotatably supported in the bearing holes 1a, 2a. The front cover 1 is provided with a suction port and a discharge port (not shown) at positions facing the meshing portions of the two gears 4 and 5, respectively.

A driving force is externally applied to a driving-side rotating shaft 4a having one end extended to the outside, so that the two gears 4, 5 are synchronously rotated in reverse, and the liquid sucked from the suction port is rotated. 4, 5 tooth grooves, side plates 6, 7 and eyeglass-shaped hole 1
The pump performs a well-known pump action of being confined in a volume space closed by x and guided to the discharge port to discharge.

[0004]

However, in such a gear pump, when the meshing ratio exceeds 1, the liquid is trapped, and the trapped liquid is compressed and expanded to generate noise. There is. Specifically,
4 and 5 show the meshing state of the gear having the meshing ratio of about 1.4. FIG. 4 shows when the teeth B, B 'start meshing, and FIG. 5 shows when the teeth A, A' gear meshing ends. During this time, the gears 4 and 5 have their teeth (B, B '), 2 (A, A')
Meshing at points. In the figure, r1 is the pitch circle diameter, r
2 is the base circle diameter, r3 is the tooth tip circle diameter, and L is the meshing line. The meshing line L represents a locus in which the meshing point changes from the start of meshing of the specific teeth to the end of meshing. Further, the meshing ratio indicates a ratio at which the other teeth simultaneously mesh with each other while the specific teeth mesh with each other on the meshing line L. That is, the meshing ratio of 1.4 indicates that two pairs of teeth mesh with each other in a range of 40% of the meshing line L, and only a pair of teeth mesh with each other in the other range. Similarly, if the meshing ratio is 2.4, it indicates that three pairs of teeth mesh with each other within a range of 40% of the meshing line, and that the other two teeth mesh with each other.
Indicates that only a pair of teeth are always engaged. As described above, the meshing ratio represents the average value of the number of pairs of teeth that mesh simultaneously while the pair of gears are rotating, and is determined by the quotient obtained by dividing the length of the contact arc by the circular pitch.

In the state shown in FIG. 4, a contact portion b between the teeth B and B 'and a contact portion a between the teeth A and A' form a closed portion X indicated by oblique lines in the figure. Is trapped. This closed state continues until the gears 4 and 5 rotate to the positions shown in FIG. 5 where the engagement of the teeth A and A 'ends. Then, there is a problem that the liquid confined during this period is compressed and expanded, which leads to generation of sound.

[0006] In order to solve such a problem, FIG.
As shown in FIGS. 8A and 8B, a structure in which appropriate escape grooves c and d are provided has been considered. The gears 4 and 5 in FIG. 6 are in the same position as in FIG. 4, and the gears 4 and 5 in FIG. 8 are in the same position as in FIG. FIG. 7 shows a state in the middle. From the position shown in FIG. 6, the gears 4 and 5 start to contact at two points b and a, but the liquid is connected to the high pressure side by the relief groove c, and the closing portion X
The liquid does not compress / expand at this point. Teeth B as it is
When the contact point b of B ′ moves to the end of the clearance groove c as shown in FIG. 7, the passage to the high pressure side is blocked, but the moment the further rotation from the position, the contact of the teeth A, A ′ The point a moves in the direction of the escape groove d, and the liquid in the confined portion X remains connected to the low-pressure portion up to the position shown in FIG. 8, so that no compression or expansion of the liquid occurs during this time.

As described above, by providing the appropriate escape grooves c and d, it is possible to effectively prevent the liquid from being trapped. However, when the amount of liquid flowing in is large due to a large tooth width or the like, compression / expansion occurs due to pressure loss, which also leads to generation of noise. If the depth of the escape grooves c and d is increased in order to increase the amount of liquid escape in response to this, the thickness of the portions (side plates 6 and 7 in the illustrated example) in contact with the gear side surface becomes unnecessarily large, As a result, the axial dimension of the casing 3 also becomes longer, so that an increase in cost and an increase in the size of the entire pump are inevitable.

Therefore, as an effective method for solving the above-mentioned problems, setting the engagement ratio to 1.00 is considered as one effective method. In this way, teeth 4 and 5 are always 1
This is because they come into contact only at a point, and the liquid does not compress and expand. However, for example, as shown in FIG. 9, if the tooth tip diameter r3 is reduced, the theoretical discharge amount per unit length is reduced, so that the gear 4 shown in FIGS.
In order to obtain the same discharge amount as in No. 5, it is indispensable to increase the tooth width, and it is necessary to increase the size of the pump.

Another method for setting the engagement ratio to 1 is as follows.
Although a method of adjusting the amount of cut-off is also conceivable, usually, the finish processing of the tooth surface is performed by shaving processing, and before and after this processing, the cut-off position greatly changes due to a slight difference in finishing allowance, so that an appropriate meshing ratio can be adjusted. There is a problem that implementation is difficult. As a specific example, FIG. 10 shows a tooth profile curve e before shaving processing by a broken line, and a tooth profile curve f after shaving processing by a solid line. Here, when the shaving amount m is set to 3%, the cut-down position g after shaving is reduced by n = 11% in circle diameter ratio as compared with the cut-down position h before shaving. Such a change in the amount of cut-down greatly affects the engagement ratio, and there is also a dimensional error at the time of shaving, so that it is actually difficult to accurately control the position of the cut-down after shaving.

An object of the present invention is to solve these problems effectively.

[0011]

SUMMARY OF THE INVENTION To solve the above problems, the present invention comprises a pair of intermeshing gears,
In those gears having a tooth profile with a meshing ratio exceeding 1 and before the tooth profile reaches the tooth tip, the position where the meshing ratio becomes 1 is cut inward to terminate the tooth profile at that position, It is characterized in that the area from the cutting position to the tooth tip is continuous through a line inside the original tooth profile curve.

If the meshing ratio is maintained at 1, the liquid is not trapped, so that the problem of the compression / expansion of the liquid and the noise generated by the pump can be effectively solved. In addition, since the tooth tip circle diameter is maintained as it is, it is possible to prevent the disadvantage that the discharge amount is reduced.
In addition, when the meshing ratio is set to 1 by cutting the tooth profile curve inward, the cutting position does not change significantly before and after shaving, so that the meshing ratio 1.00 can be adjusted relatively easily. Becomes Needless to say, there is no need to change the passage of the escape groove in accordance with the change in the tooth width unlike the case where the escape groove is provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. The basic configuration of the entire gear pump is the same as that shown in FIG. 3, and a description thereof will be omitted.
In this embodiment, an involute curve having a meshing ratio exceeding 1 is adopted as the tooth profile of a pair of gears 4 and 5 meshing with each other. And the tooth profile curve is a tooth tip 4x,
Before reaching 5x, the tooth profile curve ends at the position p where the meshing ratio becomes 1.00 by cutting inward, and the portion between the cutting position p and the tooth tip is inside the original tooth profile curve. Through the line q. It is needless to say that the inner line q is not limited to the illustrated shape. Further, the cutting position p is the same position as the tip diameter r3 in FIG.

However, if the involute curve is interrupted so that the meshing ratio becomes 1.00, the gears 4 and 5 are always in contact with each other at only one point. Does not occur. Therefore, the problem of pump noise generation can be effectively solved. In addition, since the tooth tip circle diameter r3 maintains the same value as that shown in FIGS. 4 to 8, it is possible to eliminate the disadvantage that the discharge amount is reduced.

In addition, the tooth profile curve is cut inward at a cutting position p at which the meshing ratio becomes 1.00.
Since the tooth shape curve hardly changes even if the tooth profile curve changes from e to f in the drawing due to shaving, the state of the meshing ratio of 1.00 can be properly maintained before and after shaving. For this reason, the engagement ratio can be adjusted to 1.00 with high accuracy without impairing the simplicity of processing. Needless to say, there is no need to change the passage of the escape groove in accordance with a change in the tooth width as in the case where the escape groove is employed.

The specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the present invention can be similarly applied to a gear pump or a motor configured with a tooth profile curve other than the involute, with a meshing ratio exceeding 1.

[0017]

According to the present invention, since the meshing ratio is set to 1 as described above, the liquid can be effectively prevented from being trapped by the liquid and the noise caused by this can be set. This is achieved by cutting a part of the outer curve inward, so that it is possible to prevent a decrease in the discharge amount as compared with a case where the diameter of the addendum circle is reduced, and it is possible to reduce shaving and the like as compared with a case where the cut-down position is adjusted. It is possible to easily and accurately manufacture a member having a predetermined meshing ratio without being affected by the machining of the member. Further, the size of the pump can be effectively prevented from being increased as compared with a method employing a relief groove.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tooth profile according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the embodiment.

FIG. 3 is a schematic longitudinal sectional view of a conventional gear pump or motor.

FIG. 4 is a diagram showing a state where gears are in contact at two points.

FIG. 5 is a diagram showing a state where gears are in contact at two points.

FIG. 6 is a diagram in which a liquid escape groove is provided in a member that contacts a gear side surface.

FIG. 7 is a diagram in which a liquid escape groove is provided in a member that contacts a gear side surface.

FIG. 8 is a diagram in which a liquid escape groove is provided in a member that contacts a gear side surface.

FIG. 9 is a diagram in which the tip diameter is reduced so that the meshing ratio becomes 1.

FIG. 10 is a view showing tooth shapes before and after shaving processing when the meshing ratio is adjusted to 1 by a cut-down position.

[Explanation of symbols] 4, 5 ... gear 4x, 5x ... tooth tip p ... cutting position q ... inner line

Claims (1)

[Claims] 1. A gear pump or motor comprising a pair of meshing gears having a tooth profile such that the gear ratio exceeds one, wherein the gear ratio is reduced before the tooth profile reaches the tooth tip of the gear. The tooth profile curve ends at that position by cutting inward the position where is 1, and the space from the cutting position to the tooth tip is continued through a line inside the original tooth profile curve. Gear pump or motor.