JPS5927293B2 - Processing method for assembly hob incisors for screw rotor of screw compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a machining method for providing a relief surface to the incisors of an assembled hob, and more specifically, for machining a male and female screw rotor of a screw compressor having a complex tooth profile. The present invention relates to a processing method for providing a relief surface to the incisors of an assembled hob used for.

As is well known, the tooth profile of the screw rotor of the In-type screw compressor has a very complex shape.

FIG. 4 shows a state in which the female rotor 1 and the male rotor 2 are engaged. As shown in this figure, the tooth profile of the female rotor 1 consists of a combination of straight lines, circular arcs, and cycloid curves, and 1 consists of a combination of cycloidal curves.

Machining of a rotor with such a complex tooth profile is
Conventionally, this is generally done using a compact price cutter.

However, recently, in order to further improve rotor machining efficiency and machining accuracy, machining using a hob has been proposed and prototypes have been made.

However, with this type of hob dedicated to rotor gear cutting, the incisors of a general bob have a straight rack, but the incisors have to have a very complex shape to correspond to the tooth profile of the rotor. , it is extremely difficult to process this with high precision.

The present invention aims to provide a processing method that can provide a flank surface with extremely high accuracy and efficiency when processing the incisors of an assembly hob for processing a threaded rotor having a complex tooth profile of this type. It is something.

The processing method according to the present invention attempts to perform continuous and efficient processing using a disc-shaped rotary grindstone that has been commonly used for this type of processing and has a contracted grinding surface on the circumference. As is well known, since the abrasive grains of this rotary grindstone are subject to severe wear, it is necessary to constantly grind the worn abrasive surface to bring out new abrasive grains onto the abrasive surface.

In other words, when grinding an assembled hob using this rotary grindstone, do you always use it on the other hand? It is necessary to correct the tooth profile.

In addition, as is well known, each cutting edge of the assembled hob is individually provided with a relief surface, so when each cutting edge of the assembled hob is fixed to the hob body, it is necessary to continuously grind the cutting edge using a rotating grindstone. There is a problem that it is not possible to grind.

In view of these points, the present invention uses a kind of rotary jig in which each cutting blade array unit of the assembled hob is fixed to the circumferential surface, and grinds the spirally arranged cutting blades of the assembled hob using a rotary grindstone. While machining can be carried out continuously and efficiently, at the same time, the tooth profile of the rotary whetstone is constantly corrected to create an appropriate grinding surface shape that corresponds to the diameter of the rotary whetstone, which decreases due to wear. It is characterized by the fact that it always embodies the following and enables highly accurate machining.

Hereinafter, the present invention will be specifically explained based on FIGS. 2 to 16.

FIG. 2 shows an assembled hob for a threaded rotor of a screw compressor, in which each incisor tooth l is provided with a flank surface by the processing method according to the present invention.

That is, this assembled hob has incisor row units 10a arranged in parallel in the axial direction.

10b, 10c, . . . are implanted at equal intervals on the circumferential surface of the hob main body 11, and in this implanted state, each incisor has a flank A with a clearance angle γ.

Now, in order to provide each incisor tooth of each half-processed incisor tooth row unit with a clearance surface A having a clearance angle γ, the rotating jig 12 shown in FIGS. 3 and 4 is used.

The above-mentioned semi-finished incisor row unit refers to one in which the incisor relief and the finished rake face B have not yet been provided.

The rotating jig 12 is substantially the same as the hob main body 11, and has a semi-processed incisor row unit 10a' on its peripheral surface.
, 10 b', 10 c'..., each cutting edge row unit) iQa'.

The rising angles of 10b', 10c', etc. in the implanted state are changed.

In other words, the direction of the top tooth trace of the imaginary flank A to be finished shown by the dashed dotted line on the declared incisor in Figure 3 should be positioned on the marked line C of a constant diameter centered on the rotation center O of the rotating jig. It is planted.

On the other hand, the rotary grindstone 13 for grinding the incisors fixed on the circumferential surface of the rotary jig 12 is of a disc type as shown in FIGS. 5I and If. It is provided with a contracted grinding surface 14 corresponding to the tooth profile.

That is, when grinding the incisors 15 (FIG. 5 I) of a hob for machining a male rotor of a screw compressor, for example, the grinding surface 14a that can give a female tooth profile to the hob incisors 15 is also Hob incisor 1 for machining rotor
6 (Fig. 5 ■), the hob incisor 16 is provided with a grinding surface 14b capable of imparting a female tooth profile.

Now, as shown in FIG. 4, the processing method according to the present invention includes incisor row units 10a', 10b', 10c', etc., in which the rotary grindstone 13 is implanted in a rotary jig 12.
(installation angle β)
While rotating at high speed and bringing the grinding surface 14 into contact with the hob cutting teeth 15 with a constant depth of cut, the rotating jig 12 is gradually rotated and the direction of its axis O? This will be moved.

By doing so, the portion D (see FIG. 8) above the flank surface A to be provided to each incisor tooth 15 is ground in sequence, and the flank surface A to be provided to each incisor tooth 15 can be obtained.

When the incisors are implanted in the rotary jig 12, this flank A is along a marked line C of a constant diameter centered on the rotation center O of the rotary jig 12. Main body 11
When it is planted, a relief angle γ can be formed.

As shown in FIG. 6, the relief angle γ is the front incisor 17
This is the clearance angle of the clearance surface A1 corresponding to , which can be obtained by the above-mentioned grinding method.On the other hand, in addition to the front cutting edge 17, the hob cutting tooth is provided with side cutting edges 18a and 18b on both sides thereof. (However, in the case of incisors such as hobs dedicated to screw rotors, the boundaries between them are not clear), and the relief A2 corresponding to these side cutting edges 18a and 18b can also be obtained at the same time by carrying out the above grinding method. can.

That is, as shown in FIG. 6, the side cutting blade 18a (18b)
has an inclination of a constant angle ρ with respect to the radial direction, so
If the incisor teeth that have been implanted and ground in the rotary jig 12 are implanted in the hob main body 11 with the rear part of the incisor dropped so that the flank surface A1 corresponding to the front cutting edge 17 has a clearance angle γ, A clearance surface (relief angle α) corresponding to the side cutting edge 18a (18b) can be obtained.

By the way, when the hob incisor is implanted in the rotating jig 12, its rake face B is aligned with the rotating jig 12 in FIG.
does not coincide with the line 19 connecting the rotation center O of the rotary grindstone and the rotation center O of the rotary grindstone (see FIG. 7).

However, the incisors implanted in the rotating jig 12 are attached to the rotating grindstone 13.
When grinding with
It touches the incisor on the line 19 connecting o'.

That is, the rotary grindstone having the reduced-shaped grinding surface 14 on the circumferential surface grinds each cross section of the incisor teeth gradually rotated by the rotary jig 12 on o-o'i, thereby imparting a predetermined tooth profile.

However, it is the front cutting edge 17 and the side cutting edges 18a, 18b that are used by the cutting teeth of the hob to cut a workpiece such as a rotor, and it is necessary to obtain a desired shape on the rake face B including these cutting edges. be.

Therefore, the shape of the contracted grinding surface of the rotary whetstone 13 is calculated by taking into account that the part where the rotary whetstone 13 actually grinds the cutting teeth is along the 0-0' line, The desired tooth profile is obtained on the rake face B including the blade.

As shown in FIG. 3, the present invention uses a rotating grindstone 13 to grind the hob incisors 15 implanted in the rotating jig 12, and at the same time, the tooth profile of the grinding surface 14 of the rotating grindstone 13 is constantly adjusted. It has been corrected.

In other words, the rotary grindstone 13 gradually wears out as the hob incisors are ground, and its diameter becomes smaller.
If the diameter of the rotary grindstone 13 changes in this way, the tooth profile of the grinding surface must be corrected to correspond to the predetermined tooth profile to be provided to the hob incisors.

If this correction is not made, the machining error of the hob incisors increases as the diameter of the rotary grindstone progresses.

The present inventor has discovered that the disk-shaped rotating grindstone 13 is the rotating jig 12.
By microscopically analyzing the grinding conditions of the hob cutting teeth 15 implanted in the grinding wheel, we found a method for determining and correcting the shape of the grinding surface that corresponds to changes in the diameter of the rotary grindstone.

Before describing the method for determining the tooth profile of a rotating grindstone, the nature of the helix angle of the hob cutting teeth 15 implanted in the rotating jig 12, which is the basis thereof, will be explained first.

FIG. 9 shows the helix angle of the hob incisors arranged along a certain marked line on the rotating jig 12, but as is clear from the figure, the helix angle differs depending on the part of the tooth surface. ing.

That is, the torsion angle F1 at the top of the tooth flank, the torsion angle F2 at the middle part of the tooth flank, and the torsion angle F3 at the bottom of the tooth flank become smaller values in this order.

This is due to the fact that the hob incisors draw a marked line.

Therefore, as shown in FIG. 10, the line of contact between the rotary grindstone 13 and the tooth surface of the hob incisor 15 does not coincide with the direction a perpendicular to each tooth, but instead forms a curved line labeled Xl to X. The curved line shows only one side of the tooth flank of the hob incisor).

The shape of the curve changes depending on the diameter of the rotary grindstone 13.

Therefore, in order to determine the grinding surface shape S1 of the rotary grindstone corresponding to the finished tooth shape X of the hob incisor, as shown in FIG. 10, the pitch circle diameter Dx, the tooth helix angle on the pitch circle;
For the hob incisor of Fl, tooth profile; (coinciding with the direction perpendicular to the tooth helix twist direction on the circle), at each point zo, zl to z5 in the thickness direction of the rotary grindstone, the axis O
Shortest distance between '-〇' and the tooth surface of the hob incisor y O) y
1 to y5 (at this time, the diameter of the rotating grindstone is D
81).

The point of the hob incisor stop that forms this shortest distance is of course
This is the point on the contact line between the hob incisor and the rotating grindstone.

Now, each point zO, zl ~ in the thickness direction of the axis 0'-0'l
Let the shortest distance corresponding to z5 be yO, and the points on the hob incisor surface of y1 to y5 be Xo and X1 to X.

At this time, as shown in FIG. 11, the tooth profile of the rotary grindstone is located at a distance of length yLy1 to y5 in the radial direction from each point zO, zl to z5 in the thickness direction of the axis O'-〇1'. 51X0
, 51X1 to S I X 5 may be sequentially determined.

A curve connecting these 5IXO2S1xl to 81X5 becomes the tooth profile S1 of the rotary grindstone.

That is, the grinding surface 14 of the rotary whetstone having the tooth profile S1 having this dimensional configuration is in close contact with each part of the incisor teeth having the pinch circle diameter Dx and the tooth profile X without any gaps while curving.

Therefore, the rotating grindstone with the tooth profile S1 has the tooth surface X of the hob incisor.
can be formed.

By the way, as mentioned above, the rotary grindstone 13 has the hob incisors 15
As it is ground, the grinding surface 14 gradually wears down and its diameter becomes smaller, until the amount of change in the diameter cannot be ignored.

As mentioned above, this diameter dimension is D8□ and the tooth normal cross section S
The rotary grindstone having No. 1 contacts and grinds a hob incisor having a pitch circle diameter Dx and a tooth helix angle F1 on the pitch circle at a curved position to form a tooth profile X.

Now, suppose that the diameter of the rotating whetstone becomes D8□ due to a non-negligible amount of wear, and if the hob incisor is ground with a rotating whetstone having the same tooth profile S1 as when the diameter is D8□,
The line of contact between the two will be different from a curved line.

Therefore, as a result, the shape formed on the tooth surface of the hob incisor becomes a shape different from X.

If the error between y and X is within the allowable range, tooth profile S1
However, if the diameter of the rotary whetstone decreases so as to fall outside this range, the rotary whetstone having the tooth profile S1 can no longer be used.

Therefore, the diameter dimensions of the rotating grindstone are D5□, D, 2. B83
. . ., the tooth profile must be sequentially corrected to S1, S2°, S3, . . . corresponding to each of these diameter dimensions.

Therefore, the present invention provides a rotary jig 12 as shown in FIG.
The tooth profile of the grinding surface 14 of the rotary grindstone 13 is corrected by grinding as necessary by making a diamond blade 42 placed on the opposite side draw a predetermined movement locus.

A specific example of this correction method is shown below. FIG. 12 shows one processing device for carrying out this correction method, 31
3 is a numerically controlled dressing device, 32 is a grindstone head, and 33 is a shaft of a rotating jig 12 in which hob incisors 15 are implanted.

As shown in FIG. 13, the numerically controlled dressing device 31 includes a dresser base 34 fixed to a support frame 46 that fixes the grindstone head 32, and a dresser base 34 mounted on the dresser base 34 so as to be pivotable in the direction of an arrow 35a. circular cradle 35,
An X sliding table 37 is placed on top of this to be movable in the Y-axis direction of the arrow shown in the figure by the drive of the X-axis pulse motor 36. An X sliding table 39 is movably mounted, and the upper end is rotatably supported by the drive of the X-axis pulse motor 40, and the lower end is supported via the support member 41. Rotatably supported by the X sliding table 39,
It also includes a bow-shaped dressing arm 43 with a diamond blade 42 fixed to the middle portion.

This dressing arm 43 is driven by an X-axis pulse motor 40 to rotate about a Z-axis 44 shown in the figure, and the diamond blade 42 fixed thereto is driven by an X-axis pulse motor 40.
, the tip 45 is always positioned on the Z-axis 44 and coincides with the rotation center line 35b of the cradle 35.

The dress arm 43 is driven by the X-axis pulse motor 36 to move in the Y-axis direction shown in the figure in synchronization with the Y-axis sliding table 37, and is driven by the X-axis pulse motor 38 to move in synchronization with the X-sliding table 39. It is designed to move in the illustrated X-axis direction.

The above-mentioned grindstone head 39 is connected to the above-mentioned numerically controlled dressing device 31.
It is attached to a support frame 46 connected to the dresser base 34 via bolts 47 and the like.

A shaft 48 is rotatably supported on this and is rotated by a drive source (not shown), and a shaft 48a shown in the figure is
It is designed to rotate in the direction.

The axis 49 of this shaft 48 is on the same plane as the plane formed by the X and Y axes, and is parallel to the X-axis direction line, and the rotating grindstone 13 is fixed to the tip of this axis,
Moreover, the center line of this rotary whetstone 13 coincides with the origin of the tip 45 of the diamond blade 42 and the center of rotation of the whetstone head.

The axis 50 of the shaft 33 is the axis 4 of the rotating grindstone shaft 48.
The plane parallel to and forming with 9 is the above X
, are provided parallel to the Y-axis plane, and at the same time are rotated by a drive device (not shown) and movable along this axis 50.

The rotating jig 12 is fixed to this shaft 33.

Thus, this processing device makes the diamond blade 42 of the numerically controlled dressing device 31 draw a required locus of motion to grind and correct the grinding surface 14 of the rotary grindstone 13, and also continuously grinds the hob cutting teeth 15 with the rotary grindstone 13. I try to grind it.

Next, a method of modifying the grinding surface of a rotary whetstone and grinding a hob cutting tooth with the rotary whetstone using the processing apparatus having the above configuration will be described.

As mentioned above, when a constant tooth profile Then, set the tooth profile of the rotating grindstone to 51jS2...
This must be corrected step by step.

Now, in advance, the diameter dimension of the rotary grindstone is D81. D.
2... Tooth profile S1 corresponding to... S2...
is digitized and set as a command value for the numerical control device, and the command values corresponding to the diameter of the rotary whetstone are sequentially input into the numerical control device to make the diamond blade 42 draw a constant motion trajectory, thereby controlling the speed of the rotary whetstone. The tooth profile is corrected to the appropriate shape.

More specifically, as shown in FIG. 35b as the center and tilt it until its center line 51 forms an angle θ with respect to the Are the X and Y axis planes perpendicular to the inclined center line of the rotating grindstone 13?
Tilt it like that.

Next, when the tooth profile command value corresponding to the diameter of the rotary grindstone at this next point is input into the numerically controlled dressing device and the device is operated, the X and Y axis pulse motors 38°3
At the same time, the Z-axis pulse motor 40 is driven and the diamond blade 42 moves along the axis 5 of the diamond blade 42.
4 rotates so as to be normal to the grinding surface of the rotary whetstone 13 at an arbitrary point, and its tip 45 moves along the illustrated tooth profile line 53 to grind and correct the grinding surface of the rotary whetstone 13. It is.

As detailed above, according to the processing method according to the present invention,
The grinding surface of the same-point grinding wheel is constantly corrected by a diamond blade to a tooth profile corresponding to the pinch circle diameter, and this rotating grinding wheel, which always has an accurate grinding surface, continuously grinds the hob incisors implanted in the rotating jig. Grinding can be done extremely efficiently.

The incisors are placed on the surface of the rotating grindstone so that the flank to be finished is located on a marked line of a constant diameter centered on the rotation center of the rotating grindstone, so while the rotating grindstone is rotated in a fixed position, By gradually rotating the rotating jig and moving the rotating jig in the direction of its axis,
The entire flank surface corresponding to the front cutting edge and side cutting edge of the hob incisor can be precisely and efficiently machined.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a screw compressor in which a pair of female M threaded rotors are engaged, Fig. 2 is a side view of an assembled hob, and Fig. 3 is an explanatory diagram showing the principle of the processing method according to the present invention. Fig. 4 is an explanatory plan view showing the relationship between the rotating jig in which hob incisors are implanted and the rotating grindstone, and Fig. 5 1. I is a cross-sectional view showing the contact state between the rotary grindstone and the hob incisor, Figure 6 is an explanatory diagram of the clearance angle created when the hob incisor is installed in the hob body, and Figure 7 is a cross-sectional view showing the contact state between the rotary grindstone and the hob incisor. Fig. 8 is a partial cross-sectional view showing the relationship between the half-finished hob incisor and the finished incisor, and Fig. 9 is a partially enlarged view of the hob incisor implanted in the rotating jig. An explanatory diagram showing the helix angle, Fig. 10 is an explanatory diagram showing the state in which the grinding surface of the rotary grindstone contacts the hob incisor, Fig. 11 is a cross-sectional view perpendicular to the tooth of the rotary grindstone, and Fig. 12 is the processing according to the present invention. 13 is a perspective view of the processing device for carrying out the method; FIG. 13 is a detailed perspective view of the numerically controlled dressing device in FIG. 12; FIG.
12 is a plan view of FIG. 12, FIG. 15 is a front view of FIG. 1, and FIG. 16 is a sectional view showing a tooth profile correction state of the rotary grindstone in FIG. 12. 10a, 10b, 10c... Incisor row unit,
11... Hob body, 12... Rotating jig, 13... Rotating grindstone, 14... Grinding surface, 15.15a... Hob incisor, 17...
・Front cutting blade, 18a, 18b...Side cutting blade, 1
9... 0-0' line, 31... Numerical control dressing device, 32... Grinding wheel head, 35...
...Cradle, 36...Y-axis pulse motor 38...X-axis pulse motor, 40...
・Z-axis pulse motor, 42...Diamond blade, 43...Dress arm, 44...Z
Axis line, 48...Axis, 49...Axis of the grindstone, 50...Axis line, 52...Motion trajectory line, 53...Tooth profile shape line.

Claims (1)

[Claims] 1 Each half-machined hob incisor tooth row unit is implanted on the circumferential surface of the rotating jig so that the top tooth trace direction of the finished flank surface to be applied to each hob incisor follows the constant diameter gauge line, while A disc-shaped rotary grindstone having a reduced grinding surface corresponding to the finished tooth profile to be imparted to the hob incisor is placed along the direction of the mark line of the hob incisor implanted in the Doi rotary jig, and this rotation As the whetstone is rotated, the grinding surface is brought into contact with the hob incisors implanted in the rotating jig with a predetermined depth of cut, and then The rotary jig is gradually rotated and moved relative to the rotary grindstone in the axial direction to sequentially grind each hob tooth. At the same time, the diameter of the rotary grindstone is reduced due to wear. The grinding surface of the rotating grindstone is corrected by grinding with a diamond blade that moves along a predetermined trajectory as the grinding speed decreases, and the grinding surface shape of the grinding wheel is adjusted so that the grinding surface shape should always give the desired tooth profile to the hob cutting teeth. In addition, the shape of the grinding surface corresponding to the respective diameter dimension of the rotary whetstone is determined by the shortest distance point from each point in the axial center plate thickness direction of the rotary whetstone to the finished tooth profile of the hob incisor. A method for machining an assembled hob incisor for machining a threaded rotor, characterized in that a curve connecting the specified shortest distance points is used as the predetermined locus of the diamond blade.