Method for manufacturing a stabilizer with a rubber bushing

Abstract

A method for manufacturing a stabilizer (1) with a rubber bushing (3), wherein the stabilizer (1) is inserted into and held in the rubber bushing (3), comprising: a first step of manufacturing a rubber bushing (3) without an intermediate plate by vulcanizing a rubber composition containing butadiene rubber and natural rubber as polymers; a second step of applying a heat-curing adhesive to at least one inner circumferential surface of the rubber bushing (3) and one outer circumferential surface of the stabilizer (1), such that a heat-curing adhesive layer is formed; a third step of inserting and fitting the stabilizer (1) into the rubber bushing (3); a fourth step of holding the rubber bushing (3) with a fixing device, such that the rubber bushing (3) is held in a direction of the stabilizer (1) being fitted into the rubber bushing (3).a fifth step of heating the rubber bushing (3) to cure the heat-curing adhesive while the rubber bushing (3) is held with the fixing device such that the rubber bushing (3) is compressed in the direction of the stabilizer (1) fitted into the rubber bushing (3) at a rate of 0% to 4%, thereby connecting and fixing the rubber bushing (3) to the stabilizer (1).

Description

TECHNICAL FIELDThe present disclosure relates to a method for producing a stabilizer having a rubber bushing.PRIOR ARTA stabilizer bar that is a part of a suspension device for vehicles such as an automobile has an anti-vibration capability in combination with a rubber bush. As shown in FIG. 1, a rubber bush 3 has a tubular shape, and a stabilizer 1 is inserted into and held in the tube. As such a stabilizer having a rubber bush, a non-bonded type in which the stabilizer 1 and the rubber bush 3 are not bonded to each other has heretofore been conventionally used. However, in recent years, a bonded type in which the stabilizer 1 and the rubber bush 3 are bonded to each other is more and more commonly used although the product price is higher. The reason for this is as follows. By bonding the stabilizer 1 and the rubber bush 3, no gap is formed between the stabilizer 1 and the rubber bush 3. Therefore, the anti-vibration performance is improved, and further, the problem of occurrence of a quiet sound due to the penetration of water or dust into the gap can also be solved. Particularly, in expensive cars in which the quiet sound is transmitted to a driver to give the driver an unpleasant feeling, the product value can be significantly influenced. Consequently, the elimination of the quiet sound is an important point.As a method for bonding the rubber bush 3 to the stabilizer 1, there are, for example, a vulcanization bonding method including simultaneously performing vulcanization molding of the rubber bush 3 and bonding of the rubber bush 3 to the stabilizer 1, and a subsequent bonding method including bonding the rubber bush 3 obtained by vulcanization molding to the stabilizer 1. The vulcanization bonding method is more suitable for enhancing the adhesion strength as compared with the bonding method performed after. However, when considering the bonding of a mass-produced rubber bush 3 to the stabilizer 1, the bonding method performed after has been improved in productivity. The joining method performed after that generally includes applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush 3 and an outer circumferential surface of the stabilizer 1, inserting and fitting the stabilizer 1 into the rubber bush 3, heating the resultant combination while applying a high pressure to the rubber bush 3 at a compression rate of 5% or more, so that the thermosetting adhesive is cured, thereby joining the rubber bush 3 to the stabilizer 1 (see JP 2001-270 315 A and JP 2006-8 082 A).PRIOR ART DOCUMENTSPATENT DOCUMENTSPTL 1: JP 2001-270 315 APTL 2: JP 2006-8 082 ASUMMARY OF THE INVENTIONAs the above-mentioned rubber bush, a rubber bush containing only natural rubber as a polymer is generally used. The heating conditions in the use environment are severe, and thus the change to a rubber bushing using a copolymer of butadiene rubber and natural rubber has been studied to suppress heat-caused setting.However, when a butadiene rubber is used as the polymer of the rubber bush, there is a problem in that after the rubber bush is bonded to the stabilizer in succession, bonding anomalies such as interfacial peeling between the rubber bush and the thermosetting adhesive layer and cohesive failure of the thermosetting adhesive layer occur, and thus the bond is not stabilized. The reason for this is assumed to be as follows. The rubber bush using a copolymer of butadiene rubber and natural rubber has a larger thermal expansion coefficient compared with that of the rubber bush containing only natural rubber as the polymer. Due to this, compared with the case where the rubber bush containing only natural rubber as the polymer is used, a stress is likely to be applied to a bonding interface between the rubber bush and the stabilizer, and the stress is likely to cause the above-mentioned problem of adhesiveness.Further, as disclosed in, for example, JP 2006-8 082 A, the problem of adhesiveness has also been studied by inserting a feedstock such as an intermediate plate made of a metal or the like into the rubber bush so that rubber deformation at the joint interface between the stabilizer and the rubber bush is structurally suppressed. However, the intermediate plate is not desirable for increasing the degree of freedom of design and for lowering cost, and thus there is a need for a solution to the problem of adhesion without using such an intermediate plate.The present disclosure has been made in view of the above circumstances, and discloses a method for producing a stabilizer having a rubber bush that can realize stable adhesion when a rubber bush using a copolymer of butadiene rubber and natural rubber is subsequently bonded with a stabilizer.According to one aspect of the present disclosure, there is provided a method of making a stabilizer having a rubber bushing, wherein the stabilizer is inserted into and retained in the rubber bushing, the method comprising:a first step of manufacturing a rubber bush without an intermediate plate by vulcanization molding a rubber composition containing butadiene rubber and natural rubber as a polymer,a second step of applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush and an outer circumferential surface of the stabilizer so as to form a thermosetting adhesive layer,a third step of inserting and fitting the stabilizer into the rubber bush,a fourth step of holding the rubber bush with a fixing device so that the rubber bush is compressed in a direction of the stabilizer fitted into the rubber bush at a rate of 0% to 5% at 25° C., anda fifth step of heating the rubber bush to cure the thermosetting adhesive while holding the rubber bush with the fixing device such that the rubber bush is compressed in the direction of the stabilizer fitted in the rubber bush at the rate of 0% to 5%, thereby connecting and fixing the rubber bush to the stabilizer.That is, in a stabilizer including a rubber bush obtained by subsequently bonding a rubber bush using a copolymer of butadiene rubber and natural rubber with a stabilizer, a bond release occurs in a portion where deformation of the rubber bush is large in a bonding step with a thermosetting adhesive during a heating reaction of an adhesive. As described above, in the rubber bush containing only natural rubber as the polymer, the following has been conducted so far. A thermosetting adhesive is applied to at least one of an inner circumferential surface of the rubber bush and an outer circumferential surface of the stabilizer. The stabilizer is inserted and fitted into the rubber bush, and the resulting combination is heated while applying a high pressure at a compression rate of 5% or more to the rubber bush to cure the thermosetting adhesive, thereby bonding the rubber bush to the stabilizer. This is because, when a high pressure is applied to the rubber bush, the stabilizer can be fixed with the counter-compression force of the rubber bush. It has been common common common technical knowledge to increase the adhesion between the rubber bush and the stabilizer by applying a high pressure. However, when this joining method was applied to the subsequent joining of the rubber bush using a copolymer of butadiene rubber and natural rubber, the rubber bush was significantly deformed due to the high pressure, and in this portion, joint peeling occurred. Further, when the rubber bush using a copolymer of butadiene rubber and natural rubber and the stabilizer were bonded to each other only with a thermosetting adhesive in succession without performing the above pressurization, a stable bond was not realized. It is important to suppress rubber deformation occurring at a bonding interface according to a rubber material in order to realize the aforementioned stable after bonding of the rubber bush to the stabilizer. The large thermal expansion coefficient of the rubber bush using a copolymer of butadiene rubber and natural rubber is used for stabilizing the bonding of the rubber bush with the stabilizer. Specifically, in a state where the stabilizer to which the thermosetting adhesive was applied was inserted into and fitted into the rubber bush, the rubber bush was held with a fixing device so that the rubber bush was compressed in the direction of the stabilizer fitted into the rubber bush at a rate of 0% to 5% at 25° C. so that the periphery of a joint portion was fixed without deformation or enlargement, and the resultant combination was heated in the fixed state so that the thermosetting adhesive was cured and the thermal expansion of the rubber bush was accelerated. With the pressure resulting from the thermal expansion of the rubber bush, a surface pressure with a low load is ensured, and thus stable adhesion can be realized while suppressing rubber deformation, with the result that the common general technical knowledge that has been accepted so far is out of the way.As described above, the method for manufacturing a stabilizer with a rubber bush of the present disclosure includes: a first step of manufacturing a rubber bush without an intermediate plate by vulcanization molding a rubber composition containing butadiene rubber and natural rubber as a polymer; a second step of applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush and an outer circumferential surface of the stabilizer so as to form a thermosetting adhesive layer; a third step of inserting and fitting the stabilizer into the rubber bush; a fourth step of holding the rubber bush with a fixing device so that the rubber bush is compressed in a direction of the stabilizer fitted into the rubber bush at a rate of 0% to 5% at 25° C., and a fifth step of heating the rubber bush to cure the thermosetting adhesive while holding the rubber bush with the fixing device such that the rubber bush is compressed in the direction of the stabilizer fitted in the rubber bush at the rate of 0% to 5%, thereby connecting and fixing the rubber bush to the stabilizer. Therefore, when the rubber bush using a copolymer of butadiene rubber and natural rubber is subsequently bonded to the stabilizer as described above, stable adhesion can be realized. Further, the rubber bush containing butadiene rubber having less setting caused by heat can be subjected to joining after that, and thus the degree of freedom in design of the rubber bush can be increased. Further, stable adhesion can be realized even when the intermediate plate of the rubber bush is omitted, and thus the effects of reducing the manufacturing cost and reducing the weight based on the omission of the intermediate plate and improving the fuel consumption of an automobile based on the reduction of the weight are achieved.Particularly, when the rubber bush is formed of a rubber composition containing butadiene rubber (BR) and natural rubber (NR) in a weight ratio BR / NR of 4 / 6 to 1 / 9, preferably in a weight ratio BR / NR of 3 / 7 to 2 / 8, the balance between the resistance to seating caused by heat and the anti-vibration properties is improved.Further, when the second step comprises applying a thermosetting basecoat adhesive to the outer circumferential surface of the stabilizer and applying a thermosetting topcoat adhesive to the thermosetting basecoat adhesive, the bond stability between the stabilizer and the rubber bushing is improved.Further, when the fixing device has a structure in which the fixing device covers the entire outer circumferential surface of the rubber bush, the pressure resulting from the thermal expansion of the rubber bush is more easily transmitted to the stabilizer, so that more stable adhesion can be obtained.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a perspective view of a stabilizer including a rubber bushing and a collar. FIG. 2 is a front view of a first pressing tool and a second pressing tool. FIG. 3 is a side view of the first pressing tool and the second pressing tool. FIG. 4 is an explanatory view for illustrating a state in which the rubber bush is fitted into the first die and the second die.DESCRIPTION OF EMBODIMENTSHereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to these embodiments.FIG. 1 is an example of a stabilizer including a rubber bush obtained by a manufacturing method of the present disclosure and a clamp configured to press and fix the rubber bush to a vehicle body side of an automobile. In FIG. 1, a stabilizer 1 and a rubber bushing 3 are shown, which are attached and fixed externally to a portion 2 to be attached of the stabilizer 1. The stabilizer 1 has a round rod shape made of metal, and the surface thereof is generally subjected to powder coating or cationic electrodeposition coating for the purpose of corrosion protection. Further, in FIG. 1, the rubber bush 3 is formed into a tubular shape including a U-shaped outer circumferential surface 4 and a straight flat surface 5 connected to both ends of the U-shaped outer circumferential surface 4, and collars 6 are respectively formed in both end portions of the rubber bush 3 in an axial direction. A cut portion 7 for mounting is formed in a radial direction and the axial direction.A clamp 8 shown in FIG. 1 is externally attached to the rubber bush 3 and is used to bring the flat surface 5 of the rubber bush 3 into pressure contact with a mounting surface of a vehicle body to fix the flat surface 5 to the mounting surface. The clamp 8 includes a U-shaped rubber bush receiver 9 on which the U-shaped outer circumferential surface 4 is fitted inside between the collars 6 of the rubber bush 3, and mounting parts 10 located respectively on the lateral outside of both opened ends of the rubber bush receiver 9. A screw insertion hole 11 is formed in each mounting part 10.As described above, the method for manufacturing a stabilizer with a rubber bush of the present disclosure includes: a first step of manufacturing a rubber bush without an intermediate plate by vulcanization molding a rubber composition containing butadiene rubber and natural rubber as a polymer; a second step of applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush and an outer circumferential surface of the stabilizer so as to form a thermosetting adhesive layer; a third step of inserting and fitting the stabilizer into the rubber bush; a fourth step of holding the rubber bush with a fixing device so that the rubber bush is compressed in a direction of the stabilizer fitted into the rubber bush at a rate of 0% to 5% at 25° C., and a fifth step of heating the rubber bush to cure the thermosetting adhesive while holding the rubber bush with the fixing device such that the rubber bush is compressed in the direction of the stabilizer fitted in the rubber bush at the rate of 0% to 5%, thereby connecting and fixing the rubber bush to the stabilizer.In the first step, a rubber bush without an intermediate plate is produced by vulcanization molding a rubber composition containing butadiene rubber and natural rubber as a polymer. There is no particular limitation on the shape of the rubber bush as long as a hole for holding the stabilizer is formed as shown in FIG. 1. Further, when the rubber composition contains butadiene rubber (BR) and natural rubber (NR) in a weight ratio BR / NR of 4 / 6 to 1 / 9, preferably in a weight ratio BR / NR of 3 / 7 to 2 / 8, the balance between the resistance to seating caused by heat and the anti-vibration properties are improved. If the amount of the butadiene rubber is too large, i.e., the amount of the natural rubber is too small, the desired anti-vibration properties are not easily obtained. If the amount of the butadiene rubber is too small, i.e., the amount of the natural rubber is too large, the desired resistance to set is not easily obtained.Further, besides the polymer such as the butadiene rubber and the natural rubber, a vulcanizing agent, a vulcanization accelerator, a vulcanization auxiliary agent, an antioxidant, a filler such as carbon black, a process oil and the like may be blended into the rubber composition as needed.The intermediate plate-less rubber bush is manufactured by vulcanization molding a rubber composition obtained by kneading each of the above materials. The molding is performed by heating the rubber composition from 150° C. to 190° C. for 5 minutes to 30 minutes.The second step includes applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush thus obtained and an outer circumferential surface of the stabilizer so as to form a thermosetting adhesive layer. In particular, it is preferable that this step comprises applying a thermosetting basecoat adhesive to the outer circumferential surface of the stabilizer and applying a thermosetting topcoat adhesive to the thermosetting basecoat adhesive, since then the bonding stability of the stabilizer and the rubber bushing is improved. The thermosetting adhesive is applied by spraying or the like and then naturally dried to form a thermosetting adhesive layer. When both the thermosetting topcoat adhesive and the thermosetting basecoat adhesive are used, the thermosetting basecoat adhesive is applied and dried naturally, and then the thermosetting topcoat adhesive is applied to the thermosetting basecoat adhesive. The resulting material is again naturally dried to form a thermosetting topcoat adhesive layer and a thermosetting basecoat adhesive layer.Examples of the thermosetting adhesive include an epoxy-based adhesive, an acrylic adhesive, a urethane-based adhesive, a chlorinated rubber-based adhesive, a resin-based adhesive, and a polyolefin-based adhesive. Further, when both the thermosetting topcoat adhesive and the thermosetting basecoat adhesive are used as described above, for example, a polyolefin-based adhesive is preferably used as the thermosetting topcoat adhesive, and as the thermosetting basecoat adhesive, for example, a chlorinated rubber-based adhesive is used.It is preferable that the thickness of the thermosetting adhesive layer is preferably in a range of 20 μm to 30 μm when the thermosetting adhesive layer is a single layer. When both the thermosetting topcoat adhesive and the thermosetting basecoat adhesive are used, it is preferable that the thickness of the thermosetting topcoat adhesive layer is in a range of 15 μm to 20 μm and the thickness of the thermosetting basecoat adhesive layer is in a range of 5 μm to 10 μmAfter the second step, the third step includes inserting and fitting the stabilizer 1 into the rubber bush 3. as shown in FIG. 1, the cut portion 7 of the rubber bush 3 obtained by vulcanization molding may be opened to apply the rubber bush 3 to the outside of the portion 2 to be fitted and to insert and fit the stabilizer 1 into the rubber bush 3. Further, the thermosetting adhesive layer formed in the second step is naturally disposed at the interface between the rubber bush 3 and the stabilizer 1.The fourth step includes holding the rubber bush 3 with a fixing device so that the rubber bush is compressed in a direction of the stabilizer 1 fitted into the rubber bush 3 at a rate of 0% to 5% at 25° C. The fifth step performed after the fourth step includes heating the rubber bush 3 to cure the thermosetting adhesive while holding the rubber bush such that the rubber bush is compressed in the direction of the stabilizer fitted into the rubber bush at the rate of 0% to 5% at 25° C., thereby connecting and fixing the rubber bush 3 to the stabilizer 1. The compression rate refers to the ratio of the thickness of the rubber bush 3 compressed with the fixing device to the 100% thickness of the rubber bush 3 in a non-compressed state. That is, the compression rate is set based on the dimensions of the rubber bush 3 before heating and the dimensions set with the fixing device.The fourth and fifth steps are performed, in particular, as follows. That is, as shown in FIG. 4, a first fitting recessed portion 14 of a first pressing die 13 is externally applied to a protruding curved surface 12 of the U-shaped outer circumferential surface 4, and a second fitting recessed portion 17 of a second pressing die 16 is externally applied to the flat surface 5 and a straight surface 15 of the U-shaped outer circumferential surface 4. Then, the rubber bush 3 is held by being sandwiched between the first die 13 and the second die 16 such that the rubber bush 3 is brought into a state of being compressed at a rate of 0% to 5% at 25° C., and is heated in this state. Thereafter, the first die 13 and the second die 16 are removed, so that a stabilizer including a rubber bush is provided. It is preferable that the heating temperature is 150° C. to 180° C. and the heating time is 1 hour to 2 hours. This is because when the rubber bush 3 is heated under the above-mentioned condition, curing of the thermosetting adhesive and thermal expansion of the rubber bush 3 are accelerated, and a surface pressure with a low load is ensured with the pressure resulting from thermal expansion of the rubber bush 3, with the result that stable adhesion can be realized while suppressing rubber deformation. From the viewpoint of stable adhesion, the thermal expansion coefficient of the rubber bush 3 at the above-mentioned heating temperature is within a range of preferably 1.9×10 -4 K -1 to 2.4×10 -4 K -1, more preferably 2.0×10 -4 K -1 to 2.2×10 -4 K -1. Further, the first pressing die 13 and the second pressing die 16 serve as the fixing device in the fourth and fifth steps.The first pressing die 13 and the second pressing die 16 may be used as brackets configured to fix the rubber bush 3 on a vehicle body side of an automobile without being removed from the stabilizer with a rubber bush. When the first die 13 and the second die 16 are not removed from the rubber bush 3, it is preferable in view of anti-vibration properties and the like that the fourth and fifth steps are performed after the thermosetting adhesive layer is also formed at an interface between the rubber bush 3 and the first die 13 and the second die 16. In this case, the step of forming the thermosetting adhesive layer is performed at the interface between the rubber bush 3 and the first die 13 and the second die 16 according to the second step.Further, although the first die 13 and the second die 16 are used as the fixing device in the fourth and fifth steps of FIG. 4, a general die may be used as the fixing device. Further, the clamp 8 as shown in FIG. 1 can also be used as a fixing device.As shown in FIGS. 2 and 3, the first pressing die 13 includes a first receiving portion 18 having a U-shaped cross section and configured to receive a protruding curved portion 37 (see FIG. 4 ) of the rubber bush 3, and a pair of first mounting plates 19 extending on the lateral outside from both open ends of the first receiving portion 18. The first fitting recessed portion 14 is formed in the first receiving portion 18. The first fitting recessed portion 14 is externally fitted to the protruding curved surface 12. A pair of collar receivers 20 configured to receive the pair of collars 6 of the rubber bush 3 are respectively formed in the first fitting recessed portion 14. A pair of through holes 21 are formed in the first mounting plates 19, and a pair of first side walls 23 covering both end surfaces 22 of the protruding curved portion 37 in the axial direction are formed in both end portions of the first pressing die 13 in the axial direction, respectively. A semicircular recessed portion 25 formed to receive the stabilizer 1 is formed in the first side wall 23.Further, as shown in FIGS. 2 and 3, the second die 16 includes a second receiving portion 28 having a quadrangular U-shaped cross section configured to receive a quadrangular block portion 26 of the rubber bush 3 (see FIG. 4, a rubber bush portion having an outer circumferential surface including the flat surface 5 and the straight surface 15 of the U-shaped outer circumferential surface 4), and a pair of second mounting plates 29 extending on the lateral outside from both open ends of the second receiving portion 28. The second fitting recessed portion 17 is formed in the second accommodating portion 28. The second fitting recessed portion 17 is externally fitted on the flat surface 5 and the straight surface 15 of the U-shaped outer peripheral surface 4. A pair of pins 30 respectively entering the pair of through holes 21 of the first mounting plate 19 are formed on the second mounting plate 29 so as to protrude therefrom. A pair of second side walls 32 covering both end surfaces 31 of the square block portion 26 in the axial direction are respectively formed in both end portions of the second die 16 in the axial direction, and a semicircular recessed portion 33 formed to receive the stabilizer 1 is formed in the second side wall 32. The end surface 31 of the square block portion 26 is joined to the end surface 22 of the protruding curved portion 37 without any step.The pair of pins 30 of the second die 16 enter the pair of through holes 21 of the first die 13, respectively, in a state where the rubber bush 3 is compressed by being sandwiched between the first die 13 and the second die 16. Further, substantially the entire surface of the rubber bush 3 is covered with the first fitting recessed portion 14 and the second fitting recessed portion 17. When the fixing device has a structure in which the fixing device covers the entire outer circumferential surface of the rubber bush 3 in the fourth and fifth steps, as in the first die 13 and the second die 16, the pressure resulting from the thermal expansion of the rubber bush 3 is more easily transmitted to the stabilizer 1, and more stable adhesion can be obtained.The stabilizer having a rubber bush thus produced can be suitably used as an anti-vibration device in automobiles and transportation vehicles, such as industrial transportation vehicles such as an airplane, a forklift, a wheel loader, and a crane, and can also be used as an anti-vibration device used in other industrial machines.EXAMPLESNext, examples will be described together with comparative examples and reference examples. However, the present invention is not limited to these examples.[Example 1]First, 100 parts by mass (hereinafter abbreviated as "parts") of a polymer obtained by mixing butadiene rubber (BR) and natural rubber (NR) in a weight ratio BR / NR of 20 / 80, 5 parts of a vulcanization aid, 5 parts of an antioxidant, 80 parts of carbon black, 3 parts of a vulcanization accelerator, and 1 part of a vulcanizing agent were kneaded to prepare a rubber composition. Then, the rubber composition thus prepared was charged into a mold and subjected to vulcanization molding by heating at 150° C. for 30 minutes, whereby a rubber bush having an inner diameter of 25 mm without an intermediate plate was prepared.Next, a chlorinated rubber-based adhesive as a thermosetting basecoat adhesive was applied to an outer circumferential surface of a stabilizer subjected to powder coating, having an outer diameter of 25 mm, and being naturally dried. Then, a polyolefin-based adhesive as a thermosetting topcoat adhesive was applied to the thermosetting basecoat adhesive, and the resulting material was dried again naturally, thereby forming a thermosetting basecoat adhesive layer having a thickness of 10 μm and a thermosetting topcoat adhesive layer having a thickness of 20 μm.Then, the stabilizer was inserted and fitted into the rubber bush. Thereafter, the chewing bush was compressed by sandwiching between a first die and a second die as shown in FIG. 4. The rubber bush was heated at 170° C. for 2 hours in a state where the rubber bush was compressed at a compression rate of 0° C. at 25° C., so that the thermosetting adhesive was cured. Then, the first die and the second die were removed to provide a stabilizer having a rubber bush.The "compression rate of 0%" refers to the situation where an outer circumferential surface of the rubber bush is held in contact with the inner surfaces (fitting recessed portions) of the first die and the second die in a non-compressed state at 25° C. before heating.[Examples 2 to 4, Comparative Examples 1 to 4, and Reference Examples 1 to 4]A stabilizer having a rubber bush was prepared in the same manner as in Example 1, except that the weight ratio between butadiene rubber (BR) and natural rubber (NR) in a polymer of the rubber composition serving as a material of the rubber bush was set to values shown in Tables 1 to 3 given later, and the compression rate at 25° C. when the rubber bush was compressed before heating by sandwiching between the first die and the second die was set to values shown in Tables 1 to 3 given later.The compression rate refers to the ratio of the thickness of the rubber bush compressed with the first die and the second die with respect to the 100% thickness of the rubber bush in a non-compressed state, and is set on the basis of the dimensions of the rubber bush before heating and the dimensions of the inner circumferential surfaces, i.e., the recessed fitting portions, the first die and the second die. Further, the "compression rate of 0%" shown in the tables refers to the situation where the outer circumferential surface of the rubber bush is held in contact with the inner circumferential surfaces, i.e., the fitting recessed portions, of the first die and the second die in a non-compressed state before heating.The rubber bush stabilizers of the examples and the like thus obtained were evaluated for the bonding properties of the rubber bush and the stabilizer according to the following criteria. The results are shown in Tables 1 to 3 given later.<Connection Properties>First, a rubber sheet having a thickness of 10 mm was produced using the same materials as those of the rubber bush of Examples under the same heating conditions as those of Examples. Next, the same thermosetting basecoat adhesive as that of Examples was applied by spraying onto an iron plate and naturally dried, thereby forming a thermosetting basecoat adhesive layer having a thickness of 10 μm. Thereafter, the same thermosetting topcoat adhesive as that of Examples and the like was applied by spraying onto the thermosetting basecoat adhesive, and the resultant material was naturally dried, thereby forming a thermosetting topcoat adhesive layer having a thickness of 20 μm. Then, the rubber sheet prepared in the above-described manner was laminated on the thermosetting topcoat adhesive layer. The rubber sheet was fixed in a state of being compressed on the iron plate side at a compression rate at 25° C. shown in Tables 1 to 3 given later, and heated at 170° C. in the compressed state for 2 hours, thereby curing the thermosetting adhesive. Thereafter, the compressed state was released and the rubber sheet was bonded to the iron plate, thereby providing a sample for evaluating the bonding properties of Examples.Then, an end portion of the rubber sheet in the sample for evaluation of bonding properties was peeled off and pulled in the direction of an opposite side to the iron plate at a speed of 50 mm / minute using a strograph (manufactured by Toyoseiki Co., Ltd.), and thus, peeling of the rubber sheet from the iron plate was performed. The state of the peeled surface in this case was visually evaluated, and the entire peeled surface was determined for a proportion (%) of a range falling under the following criteria (R, RC, CC). A peeled surface that was R 100% was evaluated as "OK", and the peeled surface that was not R 100% was evaluated as abnormal peeling and evaluated as "NG". As for the peeled surface evaluated as "OK", the bonding strength (N / mm) during the above peeling was measured with a Strograph (manufactured by Toyoseiki Co., Ltd.).R: Breakage of the rubber sheet (broken material)RC: Interfacial Detachment Between the Rubber Ply and the Thermosetting Topcoat Adhesive LayerCC: Cracking of the thermosetting topcoat adhesive layerTable 1 Table 1Example 120 / 800%6,0 N / mmR100%OKExample 220 / 804%5,4 N / mmR100%OKComparative Example 120 / 807%-R30 %, RC55 %, CC15 %NGComparative Example 220 / 8010 %R20 %, RC80 %NGTable 2Table 2Example 330 / 700 %5,3 N / mmR100%OKExample 430 / 704%5,2 N / mmR100%OKComparative Example 330 / 707%-R10 %, RC30 %, CC60 %NGComparative Example 430 / 7010 %-R10 %, RC30 %, CC60 %NGTable 3Table 3Reference Example 10 / 1000%-R80 %, RC20 %NGReference Example 20 / 1004%6,6 N / mmR100%OKReference Example 30 / 1007%7,3 N / mmR100%OKReference Example 40 / 10010 %7,4 N / mmR100%OKAs is apparent from the evaluation results of the examples and the comparative examples in Tables 1 and 2, the following is obtained. In order to realize stable adhesion when the rubber bush using a copolymer of butadiene rubber and natural rubber is bonded to the stabilizer in succession, it is preferable that the rubber bush is heated to cure the thermosetting adhesive while the rubber bush is held with the fixing device such that the rubber bush is compressed in the direction of the stabilizer which is an iron plate at a rate of 0% to 5% at 25° C., thereby bonding and fixing the rubber bush to the stabilizer.It should be noted that when the rubber bush comprising natural rubber only as a polymer is subsequently bonded to the stabilizer as in the prior art, stable adhesion can be realized at a higher compression rate as shown in Reference Examples 1 to 4 of Table 3.Although specific forms of embodiments of the present invention have been described above in order to make them more comprehensible, the above description is given by way of example only and should not be construed as limiting the scope of the present invention. It is contemplated that various modifications will be made which will be apparent to those skilled in the art without departing from the scope of the invention.The method for manufacturing a stabilizer having a rubber bush of the present disclosure may be preferably performed as a method for manufacturing a stabilizer having a rubber bush used as an anti-vibration device in automobiles and transportation vehicles, such as industrial transportation vehicles such as an aircraft, a forklift, a wheel loader, and a crane. The method for producing a stabilizer with a rubber bush of the present disclosure can also be applied as a method for producing a stabilizer with a rubber bush that can be used as an anti-vibration device used in other industrial machines.LIST OF REFERENCE CHARACTERS1 Stabilizer 2 Fitting portion 3 Rubber bush 4 U-shaped outer peripheral surface 5 Flat surface 13 First pressing tool 14 First fitting recessed portion 16 Second pressing tool 17 Second fitting recessed portion

Claims

A method for producing a stabilizer (1) having a rubber bush (3) in which the stabilizer (1) is inserted into and held in the rubber bush (3), the method comprising: a first step of producing a rubber bush (3) without an intermediate plate by vulcanization molding a rubber composition containing butadiene rubber and natural rubber as a polymer; a second step of applying a thermosetting adhesive to at least one of an inner circumferential surface of the rubber bush (3) and an outer circumferential surface of the stabilizer (1) so as to form a thermosetting adhesive layer; a third step of inserting and fitting the stabilizer (1) into the rubber bush (3); a fourth step of holding the rubber bush (3) with a fixing device so as to fix the rubber bush (3) in a direction of the stabilizer (1), A rubber bush (3) is fitted at a rate of 0% to 4% compressed at 25°C, and a fifth step of heating the rubber bush (3) to cure the thermosetting adhesive while holding the rubber bush (3) with the fixing device such that the rubber bush (3) is compressed in the direction of the stabilizer (1) fitted in the rubber bush (3) at the rate of 0% to 4%, thereby bonding and fixing the rubber bush (3) to the stabilizer (1).The method for producing a stabilizer (1) having a rubber bush (3) according to claim 1, wherein the rubber bush (3) comprises a rubber composition containing butadiene rubber (BR) and natural rubber (NR) in a weight ratio BR / NR of 4 / 6 to 1 / 9.The method for producing a stabilizer (1) having a rubber bush (3) according to claim 1, wherein the rubber bush (3) comprises a rubber composition containing butadiene rubber (BR) and natural rubber (NR) in a weight ratio BR / NR of 3 / 7 to 2 / 8.The method for producing a stabilizer (1) having a rubber bush (3) according to any one of claims 1 to 3, wherein a thermal expansion coefficient of the rubber bush (3) is within a range of 1.9×10 -4 K -1 to 2.4×10 -4 K -1.The method for producing a stabilizer (1) having a rubber bush (3) according to any one of claims 1 to 4, wherein the second step comprises applying a thermosetting basecoat adhesive to the outer circumferential surface of the stabilizer (1) and applying a thermosetting topcoat adhesive to the thermosetting basecoat adhesive.The method for producing a stabilizer (1) having a rubber bush (3) according to any one of claims 1 to 5, wherein the fixing device covers the entire outer circumferential surface of the rubber bush (3).The method for producing a stabilizer (1) having a rubber bush (3) according to any one of claims 1 to 6, wherein in the fifth step, the rubber bush (3) is heated at 150°C to 180°C for 1 to 2 hours.

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