JP3922972B2 - Rack manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a rack using a processing apparatus that operates based on rack model data created using a CAD system. The rack is, for example, a rack and pinion type vehicle steering system. Used for equipment.
[0002]
[Prior art]
Conventionally, as a method for manufacturing a rack, there is a method for manufacturing a variable gear rack disclosed in Japanese Patent Publication No. 3-33418. In this manufacturing method, the tooth profile of the electrode rack is created by a pinion tool formed by processing such as cutting and grinding from specifications for determining the pinion shape. Then, a forging die is formed by electric discharge machining using this electrode rack, and a rack is manufactured by forging using the forging die.
[0003]
[Problems to be solved by the invention]
By the way, in the said prior art, a rack is manufactured through the following process.
Design drawing → Pinion tool forming → Electrode rack forming → Forging die forming → Forging → Rack (product)
In this manufacturing process, the transfer from the electrode rack to the forging die and the transfer from the forging die to the product rack are performed, so the transfer is performed twice for the pinion tool reflecting the specifications of the pinion. Since the rack is manufactured after that, it is difficult to obtain a rack having a highly accurate tooth profile. In particular, in a variable gear type (variable gear type) rack, a rack having a high precision tooth profile cannot be obtained. A meshing sound was generated.
[0004]
Moreover, since each process of forming a pinion tool and an electrode rack is included, the number of manufacturing steps is increased, resulting in an increase in cost, and a great amount of time is required from the creation of the design drawing to the completion of the rack. Furthermore, in the manufacturing method using the electrode rack, the tooth profile cannot be confirmed unless the rack is actually completed. Therefore, before the step of forming the forging die, the meshing state of the pinion with the rack as a product, for example, meshing However, there was a waste of time and cost until a forging die meeting the accuracy requirement was obtained.
[0005]
The present invention has been made in view of such circumstances, and the inventions of claims 1 and 2 can improve the accuracy of the tooth profile of the rack, and further reduce the manufacturing cost and the manufacturing time. It is an object of the present invention to provide a method for manufacturing a rack capable of performing the above. A second object of the present invention is to suppress the occurrence of meshing noise in a low gain region in a rack and pinion type vehicle steering device using a variable gear ratio type rack.
[0006]
[Means for Solving the Problems and Effects of the Invention]
The invention according to claim 1 is a rack including the following steps (A) to (D) for creating a rack model by a computer constituting a CAD system and the following step (E) for forming a rack. It is a manufacturing method.
(A) A step of creating a pinion cutter model and a rack material model based on the pinion shape and the rack material shape input to the computer.
(B) A step of positioning the pinion cutter model with respect to the rack material model so that the pinion and the rack meshing with the pinion have a set positional relationship.
(C) creating a pinion cutter motion trajectory model from a trajectory obtained by rotating and translating the positioned pinion cutter model in accordance with a rack gain that is a translational movement amount of the rack with respect to the rotation angle of the pinion. .
(D) A step of creating a rack model by cutting the rack material model by the pinion cutter motion trajectory model.
(E) A step of forming a rack by processing a rack material by a processing device that operates based on the three-dimensional data of the rack model, or by forming a forming die using the processing device and using the forming die Forming the rack;
[0007]
As a result, the rack material model is cut and tooth gaps are created by the pinion cutter motion trajectory model obtained by simulating the actual movement of the pinion and the rack that mesh with each other according to the rack gain, and the rack model is created. Is done. Then, the rack is directly formed by a processing device that operates based on the three-dimensional data obtained from the created rack model, or a forming die for forming the rack is directly formed. Further, since the pinion cutter motion trajectory model is created from the trajectory of the pinion motion, the rack material model is cut and the rack model is created without moving the pinion cutter motion trajectory model.
[0008]
As a result, according to the first aspect of the present invention, the following effects can be obtained. That is, a pinion cutter model and a rack material model are created based on the pinion shape and rack material shape input to the computer, the pinion cutter model is positioned with respect to the rack material model, and the positioned pinion cutter model is set to the rack gain. In principle, a pinion cutter motion trajectory model is created from the trajectory obtained by rotating and translating, and the rack material model is cut by the pinion cutter motion trajectory model to create a rack model, which is used to manufacture the rack. Is operated based on the three-dimensional data of the rack model, so that the processing device that operates based on the three-dimensional data of the rack model created by simulating the actual meshing state of the rack and the pinion Machining directly or forming a rack Since the mold for processing is directly processed, the number of times of transfer is less than that of the conventional technique, and the data for controlling the operation of the processing apparatus reflects the actual meshing state with the pinion. A rack having a highly accurate tooth profile is obtained . Upon its, unlike the the prior art, it is not necessary to mold the pinion tools and electrodes rack, decreased production man-hours, the rack of the production cost and shorten the manufacturing time can be reduced. In addition, since the rack model is created by superimposing the pinion cutter motion trajectory model and the rack material model without rotating the pinion cutter motion trajectory model, the performance requirements for the computer can be reduced, Processing with a computer becomes easy. Further, when the rack model is created, it is possible to evaluate the state meshing utilizing solid model of the pinion which is separately prepared, with processing data obtained based only on the teeth to satisfy the design shape, dead In this respect, it is possible to reduce the manufacturing cost and the manufacturing time of the rack.
[0009]
According to a second aspect of the present invention, in the rack manufacturing method according to the first aspect, the rack is used in the rack and pinion type vehicle steering apparatus, and the rack gain depends on a meshing position with the pinion. It is a variable gear ratio type rack that changes as a result.
[0010]
Thereby, in the variable gear ratio type rack of the steering device, the tooth portion including the low gain region constituted by the row of teeth with a small pitch of the tooth portion is constituted by a tooth having a highly accurate tooth profile. As a result, according to the invention described in claim 2, in addition to the effect described in claim 1, the following effect is exhibited. That is, the rack is a variable gear ratio type rack used in a rack and pinion type vehicle steering device, and the low gain region of the tooth portion of the variable gear ratio type rack is also configured with teeth having a high accuracy tooth profile. Therefore, the generation of the meshing sound due to the meshing with the pinion in the low gain region is suppressed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
The rack manufactured by applying the manufacturing method according to the present invention is a rack used in a rack and pinion type vehicle power steering apparatus. Referring to FIGS. 1 and 2, the rack 1 is a variable gear ratio type rack in which the translational movement amount of the rack 1 with respect to the rotation angle of the pinion 2, that is, the rack gain, varies depending on the meshing position with the pinion 2. .
[0012]
In the rack 1, a low gain region 3 </ b> L, a variable gain region 3 </ b> V, and a high gain region 3 </ b> H are formed in the tooth portion 3, which is a portion where a row of teeth 3 a (hereinafter referred to as “dental row”) is formed. The The low gain region 3L is formed in a predetermined range around the neutral position P1, which is the center point of the tooth portion 3 in the translation direction A1 of the rack 1, and the rack gain is set by a low-pitch tooth row having a constant value. Low gain. The variable gain area 3V is connected to the low gain area 3L and is formed in a predetermined range on both sides of the low gain area 3L, and its rack gain is set by a tooth row with a pitch that becomes larger than the low gain as it moves away from the neutral position P1. Variable gain. The high gain region 3H is connected to each variable gain region 3V at a position farther from the neutral position P1 than the low gain region 3L, and is formed in a predetermined range on both sides of the low gain region 3L. It is a high gain set by a large pitch tooth row having a constant value equal to the maximum gain at 3V.
[0013]
This rack 1 is a processing device that operates based on the three-dimensional data of a rack model 50 (see FIG. 13) created using a three-dimensional CAD system composed of a computer 10 having the device shown in FIG. Molded using. Note that each model described later, including the rack model 50 created by the computer 10 of the CAD system, is a three-dimensional solid model.
[0014]
The computer 10 is composed of a keyboard, a mouse, and the like, and based on the input information 11 for inputting input information including specifications and operation commands for specifying the shape of the pinion 2 and the shape of the rack material. A central processing unit (CPU) 12 for instructing various types of processing, an image processing unit 13 for creating images including various three-dimensional models in accordance with instructions from the central processing unit 12, and various types 3 in accordance with instructions from the central processing unit 12 A storage unit 14 capable of storing and updating data such as three-dimensional data of a three-dimensional model, and a display unit 15 for displaying various three-dimensional models created according to instructions from the central processing unit 12, All these devices are connected by a bus 16 that carries signals and data.
[0015]
In this computer 10, when specifications and operation commands that define the shape of the pinion 2 and the shape of the rack material are input from the input unit 11, the image processing unit 13 is in accordance with instructions from the central processing unit 12 based on the input information. As a result, a pinio cutter model 20 and a rack material model 30 described later are created, and a pinion cutter motion trajectory model 40 is created using the data of the models 20 and 30 stored in the storage unit 14, and then the pinion cutter A rack model 50 is created using the motion trajectory model 40.
[0016]
First, the process of creating the pinion cutter model 20 (see FIG. 8) will be described with reference to FIGS. As shown in FIG. 4, the pinion cutter model 20 is based on specifications of a tooth profile (hereinafter simply referred to as “tooth profile”) in a cross section perpendicular to the rotation axis L <b> 1 of the pinion 2. Created.
[0017]
The specifications of the tooth profile of the pinion 2 obtained from the design drawing and the like are: a tooth right angle module m _n , a tooth right angle pressure angle α _n , a twist angle β, and the number of teeth Z (in this embodiment, the number of teeth is 5), shift coefficient X, the standard specifications including an addendum circle diameter d _a and Hasokoen径d _b, specifications derived from the following equation using the standard specifications (1) to (7), i.e. perpendicular to the axis module It is composed of calculation parameters comprising m _s , axial right angle pressure angle α _s , reference pitch circle diameter d _c , basic circle diameter d _e , lead L, reference arc tooth thickness S, and reference arc center angle ψ. Here, the twist angle β is a twist angle on the reference pitch circle.
m _s = m _n / cos β (1)
α _s = tan ⁻¹ (tan α _n / cos β) (2)
d _c = Z · m _n / cos β (3)
d _e = d _c · cos α _s (4)
_{L = d c · π / tanβ} (5)
S = (π · m _s / 2) + 2 · X · m _s · tan α _n (6)
ψ = 360 · S / (π · d _c ) (7)
[0018]
First, based on the tooth profile specifications and operation commands input from the input unit 11, the image processing unit 13 creates one tooth profile model 21 on the coordinates as shown in FIG.
[0019]
Thereafter, as shown in FIG. 6, the image processing unit 13 causes the tooth profile model 21 to be parallel to the rotational axis L1 at the twist angle β set at the intersection P2 between the curved portion 21a corresponding to the tooth surface and the reference pitch circle 22. A base line 23 made of a spiral curve for one lead is created by rotating it 360 degrees counterclockwise while translating in the correct direction A2. The base line 23 composed of the wire frame model is used as a reference line when the tooth profile model 21 is swept.
[0020]
Next, by sweeping the tooth profile model 21 along the base line 23 by the image processing unit 13, a single tooth model 24 that is a locus of the tooth profile model 21 is created as shown in FIG. Then, by the required number of copies at equal intervals teeth model 24 in the circumferential direction on the reference pitch circle 22, is created five teeth model 24, an outer diameter equal to this Hasokoen径d _b by columnar model 25 having a coupled, Piniokatta chromatography model 20 shown in FIG. 8 is created.
[0021]
On the other hand, FIG. 9, referring to FIG. 10, specifications and operation commands, such as the height h _a of the rack diameter d _r and the addendum of the cylindrical rack 1 is inputted from the input unit 11, based on these input information The rack material model 30 having the tooth forming part 31 provided at the height position of the tooth tip and constituted by a plane parallel to the rotation axis L1 and the central axis L2 is created by the image processing unit 13.
The three-dimensional data of the pinion cutter model 20 and the rack material model 30 are stored in the storage unit 14 in accordance with instructions from the central processing unit 12.
[0022]
Next, as shown in FIG. 9 and FIG. 10, the image processing unit 13 uses the data of the pinion cutter model 20 and the rack material model 30 acquired from the storage unit 14 by the operation command from the input unit 11, as shown in FIGS. The pinion cutter model 20 is positioned with respect to the rack material model 30 so as to have a designed position relationship that defines the reference meshing position at the neutral position P1 (see FIG. 1) between the actual pinion 2 and the rack 1. Is done.
[0023]
That is, the image processing unit 13 causes the inter-axis distance d _x between the pinion cutter model 20 and the rack material model 30 to coincide with the design value and is orthogonal to the plane constituting the tooth forming unit 31, as shown in FIG. Viewed from the direction (hereinafter referred to as “plan view”), the crossing angle θ formed by the central axis L2 of the rack 1 and the rotation axis L1 of the pinion 2 coincides with the design value, and further, the rotation axis L1 in the plan view The pinion cutter model 20 and the rack material model 30 are positioned relative to each other so that the top of the tooth tip of the pinion cutter model 20 is located in a plan view at a position P3 where the center axis L2 intersects. Then, the three-dimensional data of the positioned pinion cutter model 20 is stored in the storage unit 14.
[0024]
Next, using the data of the positioned pinion cutter model 20 acquired from the storage unit 14, the image processing unit 13 matches the actual rotational motion of the pinion 2 and the translational motion of the rack 1 that are meshed with each other. By rotating and translating only the pinion cutter model 20 in accordance with the rack gain and creating the locus of the pinion cutter model 20, the pinion cutter motion locus model 40 shown in FIGS. 11A and 11B is obtained. Created. This pinion cutter motion trajectory model 40 has teeth 41 created from the trajectory of the tooth model 27 of the pinion cutter model 20. (To avoid the complexity of the drawing, the number of teeth 41 does not match the number of tooth spaces in FIG. 1.) Further, the pinion cutter motion trajectory model 40 is a translation direction A1 of the rack 1 in design. It has a width equal to the maximum movement width in (see FIG. 9), and is larger than the width in the orthogonal direction A3 of the tooth forming surface in a direction A3 (see FIG. 9) orthogonal to the translation direction A1 in plan view. Have a width.
[0025]
Specifically, the pinion cutter model 20 positioned by the image processing unit 13 is copied every predetermined rotation and every predetermined translation according to the rack gain value, and the pinion cutter motion trajectory model 40 is created. The three-dimensional data of the pinion cutter motion trajectory model 40 is stored in the storage unit 14.
[0026]
Next, the pinion cutter motion trajectory model 40 cuts the rack material model 30 by the image processing unit 13 using the data of the pinion cutter motion trajectory model 40 and the rack material model 30 acquired from the storage unit 14, so that FIG. As shown in FIG. 13, a rack model 50 having a tooth portion 52 constituted by a row of teeth 51 is created.
[0027]
Specifically, the pinion cutter motion trajectory model 40 and the rack material model 30 shown in FIG. 12 are superimposed in the positioning state by the image processing unit 13, and the teeth 41 and the rack material model 30 in the rack material model 30 are overlapped. By cutting the portion where the two overlap, a tooth gap 53 is created in the rack material model 30 and a rack model 50 is created. The three-dimensional data of the rack model 50 is stored in the storage unit 14.
[0028]
Thereby, the three-dimensional data of the rack model 50 is obtained. In order to create a mold that is a mold by an NC processing machine that is controlled by a control device to which processing control data created based on the obtained three-dimensional data is input and operated. A die for forging for making the rack 1 by forging is directly carved.
[0029]
Thereafter, the rack 1 is manufactured by forging the rack material using the mold. For this reason, the manufacturing process of the rack 1 is
Design drawing → Creation of 3D rack model → Die molding → Forging → Rack (product) Compared to the above prior art, after creating the design drawing, the pinion tool forming process and the electrode rack forming process are not required. The manufacturing man-hours are reduced and the manufacturing time is shortened.
[0030]
Next, operations and effects of the embodiment configured as described above will be described.
A pinion cutter model 20 and a rack material model 30 are created based on the pinion shape and the rack material shape input to the computer 10 constituting the CAD system, and the pinion cutter model 20 and the rack material model 30 are related to the set positional relationship. The pinion cutter motion trajectory model 40 is created from the trajectory obtained by rotating and translating the positioned pinion cutter model 20 in accordance with the rack gain, and the rack material model is created by the pinion cutter motion trajectory model 40. The rack model 50 is created by cutting 30 and the processing machine used to form a mold for manufacturing the rack 1 by forging is operated on the basis of the three-dimensional data of the rack model 50. The actual pinion 2 and rack 1 meshing with each other according to the gain The pinion cutter motion trajectory model 40 is created by simulating the movement of the rack, the rack material model 30 is cut by the pinion cutter motion trajectory model 40, the tooth gap 53 is created, and the rack model 50 is created. And a metal mold | die is shape | molded directly by the processing machine which operate | moves based on the three-dimensional data obtained from the created rack model 50, and the rack 1 is shape | molded by forging which uses this metal mold | die.
[0031]
As a result, a processing machine that operates based on the three-dimensional data of the rack model 50 created by simulating the actual meshing state of the pinion 2 and the rack 1 directly creates a mold for molding the rack 1. Therefore, the number of times of transfer is reduced as compared with the conventional technique, and the processing data for controlling the operation of the processing machine reflects the actual meshing state with the pinion 2, and thus has a highly accurate tooth profile. Rack 1 is obtained. In addition, unlike the prior art, since it is not necessary to form a pinion tool or an electrode rack, the number of manufacturing steps is reduced, the manufacturing cost of the rack 1 is reduced, and the manufacturing time is reduced. In addition, since the rack model 50 is created by superimposing the pinion cutter motion trajectory model 40 and the rack material model 30 without rotating the pinion cutter motion trajectory model 40 , the performance requirements for the computer 10 are reduced. And the processing on the computer 10 becomes easy.
[0032]
Further, when the rack model 50 has been created, it is possible to evaluate the meshing state by utilizing the pinion solid model created separately by the CAD system, obtained based only on the teeth to satisfy the design shape processing With this data, it is possible to manufacture a high-precision forging die without waste, and in this respect, it is possible to reduce the manufacturing cost and the manufacturing time of the rack.
[0033]
In the rack 1 constituting the variable gear ratio type rack used in the rack and pinion type vehicle steering apparatus, the entire tooth portion 3 including the low gain region 3L is constituted by the teeth 3a having a highly accurate tooth profile. Therefore, the generation of the meshing sound due to the meshing with the pinion 2 in the low gain region 3L is suppressed.
[0034]
Hereinafter, an example in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
Instead of creating a die by a processing machine based on the three-dimensional data of the rack model 50, the rack 1 can be manufactured by directly processing a rack material by a processing machine. Also in this case, the manufacturing cost is reduced and the manufacturing time is shortened.
[0035]
The pinion cutter motion trajectory model 40 is created by the motion trajectory of the entire pinion cutter model 20, but the pinion cutter model 20 having at least a width corresponding to the width in the orthogonal direction A3 of the tooth forming portion 31 of the rack material model 30. The pinion cutter motion trajectory model 40 can also be created by a part, thereby shortening the creation time.
[Brief description of the drawings]
FIG. 1 is a plan view showing a state in which a rack and a pinion manufactured by the manufacturing method of the present invention are engaged with each other.
2 is a graph for explaining a relationship between a pinion rotation angle and a rack gain in the rack and pinion of FIG. 1; FIG.
FIG. 3 is a block diagram of a computer of a CAD system used when manufacturing the rack of FIG. 1;
4 is a diagram for explaining the specifications of the shape of the pinion of FIG. 1; FIG.
FIG. 5 is a diagram illustrating a process for creating a pinion cutter model by a computer when the rack of FIG. 1 is manufactured.
FIG. 6 is a diagram for explaining a step subsequent to the step of FIG. 5 when creating a pinion cutter model.
FIG. 7 is a diagram illustrating a step subsequent to the step of FIG. 6 when creating a pinion cutter model.
FIG. 8 is a perspective view of a pinion cutter model.
9 is a view for explaining positioning of the pinion cutter model and the rack material model of FIG. 8 when the rack of FIG. 1 is manufactured.
10 is an enlarged view taken along arrow X in FIG. 9 and shows a rack material model indicated by a two-dot chain line.
11A is a perspective view of a pinion cutter motion trajectory model created based on the pinion cutter model of FIG. 9, and FIG. 11B is a perspective view of the pinion cutter viewed from the B direction obliquely below FIG. FIG.
12 is a perspective view showing a state before the positioning of the pinion cutter motion trajectory model and the rack material model of FIG. 11; FIG.
13 is a perspective view of a main part of a rack model created by cutting the rack material model by the pinion cutter motion trajectory model of FIG. 11. FIG.
[Explanation of symbols]
1 ... rack, 2 ... pinion, 3 ... tooth, 3a ... tooth,
10 ... Computer, 11 ... Input unit, 12 ... Central processing unit, 13 ... Image processing unit, 14 ... Storage unit, 15 ... Display unit, 16 ... Bus,
20 ... pinion cutter model, 21 ... tooth profile model, 22 ... reference pitch circle, 23 ... baseline, 24 ... tooth model, 25 ... cylindrical model,
30 ... Rack material model, 31 ... Tooth formation part,
40 ... Pinion cutter motion trajectory model, 41 ... Teeth,
50 ... Rack model, 51 ... Teeth, 52 ... Teeth, 53 ... Tooth gap,
A1 ... translation direction, A2 ... direction, A3 ... orthogonal direction, P1, P3 ... position, P2 ... intersection, L1 ... rotation axis, L2 ... center axis.

Claims (2)

A rack manufacturing method comprising the following steps (A) to (D) for creating a rack model by a computer constituting a CAD system and the following step (E) for forming a rack: .
(A) A step of creating a pinion cutter model and a rack material model based on the pinion shape and the rack material shape input to the computer.
(B) A step of positioning the pinion cutter model with respect to the rack material model so that the pinion and the rack meshing with the pinion have a set positional relationship.
(C) creating a pinion cutter motion trajectory model from a trajectory obtained by rotating and translating the positioned pinion cutter model in accordance with a rack gain that is a translational movement amount of the rack with respect to the rotation angle of the pinion. .
(D) A step of creating a rack model by cutting the rack material model by the pinion cutter motion trajectory model.
(E) A step of forming a rack by processing a rack material by a processing device that operates based on the three-dimensional data of the rack model, or by forming a forming die using the processing device and using the forming die Forming the rack; 2. The rack according to claim 1, wherein the rack is a variable gear ratio type rack that is used in the rack and pinion type vehicle steering device, and the rack gain varies depending on a meshing position with the pinion. The manufacturing method of the rack of description.

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