Steering device

Abstract

To provide a steering device with a foreign matter infiltration preventing device formed of a rubber composition containing an environmentally friendly biomass ethylene propylene rubber, for which at least a part of ethanol being a main raw material of an ethylene propylene rubber is replaced with bioethanol derived from a plant to obtain bioethylene / biopropylene obtained therefrom.SOLUTION: A steering device 1 includes a boot 15 for a ball joint serving as a foreign matter intrusion prevention device. The boot 15 for the ball joint is composed of a rubber composition containing a biomass ethylene propylene rubber in which at least a part of ethylene / propylene of a raw material is bioethylene / biopropylene obtained using bioethanol derived from a plant.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an improvement in a steering device, and more particularly to an improvement in a rubber material constituting a foreign matter infiltration device of a steering device for a vehicle. [Background technology]

[0002] 2. Description of the Related Art Rack-and-pinion steering devices, for example, are widely used as steering devices for vehicles.

[0003] An example of a rack-and-pinion steering device is disclosed in Patent Document 1. As disclosed in Patent Document 1, the ball joint provided at the end of the rack (rack end) has grease sealed inside to make it move smoothly, and is covered with a ball joint boot that acts as a foreign matter intrusion prevention device to prevent the grease from leaking out and to prevent the intrusion of water, dust, etc. from the outside.

[0004] For example, as disclosed in Patent Document 1, in ball joint boots, taking into consideration weather resistance and chemical resistance to water and brake oil, a rubber composition using ethylene propylene rubber as the raw rubber has been used as the rubber material. However, the ethylene propylene rubber used in conventional ball joint boots is entirely derived from petroleum, including the main raw material, ethylene propylene, and is not environmentally friendly. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-6843 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve such problems associated with the prior art, and its objective is to provide a steering device in which at least a portion of the ethanol, the main raw material of ethylene propylene rubber, is replaced with plant-derived bioethanol, resulting in bioethylene / biopropylene, and in which a foreign matter intrusion prevention device is formed from a rubber composition made of environmentally friendly biomass ethylene propylene rubber. [Means for solving the problem]

[0007] In order to achieve this object, the first invention is a steering device equipped with a foreign matter intrusion prevention device, characterized in that the foreign matter intrusion prevention device is made of a rubber composition containing biomass ethylene propylene rubber, in which at least a portion of the raw material ethylene and propylene is bioethylene and biopropylene derived from plant-derived bioethanol.

[0008] A second aspect of the present invention is a steering device according to the first aspect of the present invention, characterized in that the foreign matter intrusion prevention device is at least one of a boot and a gasket.

[0009] A third aspect of the present invention is a steering device according to the first or second aspect of the present invention, characterized in that the bio-content of the biomass ethylene propylene rubber is 20% or more. Effect of the Invention

[0010] According to the present invention, at least a portion of the ethanol, which is the main raw material of ethylene propylene rubber, is replaced with plant-derived bioethanol, resulting in bioethylene / biopropylene, and a steering device can be provided in which a foreign matter intrusion prevention device is formed using a rubber composition made of environmentally friendly biomass ethylene propylene rubber. [Brief description of the drawings]

[0011] [Figure 1]1 is a schematic perspective view showing a first embodiment of a steering device of the present invention; [Diagram 2] FIG. 11 is a schematic perspective view showing an enlarged pinion area in a steering device according to a second embodiment of the present invention. [Diagram 3] FIG. 3 is an exploded perspective view of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a steering device according to the present invention will be described. Note that this embodiment is merely one embodiment of the present invention and should not be construed as being limited in any way, and appropriate design modifications are possible within the scope of the present invention. (First embodiment)

[0013] 1, a rack-and-pinion steering device 1 for a vehicle rotates a steering shaft 3 and an intermediate shaft 5 by rotating a steering wheel (not shown). Rotating a pinion shaft 9 of a pinion 7 connected to the intermediate shaft 5 reciprocates a rack shaft (not shown) of a rack 11 that meshes with the pinion shaft 9. Ends of the left and right rack shafts are connected to left and right tie rods 13 via ball joints (not shown) to steer the wheels. Here, the ball joint is covered with a rubber ball joint boot 15 as a foreign matter intrusion prevention device.

[0014] Since the present invention has technical means characteristic of the foreign matter intrusion prevention device, the foreign matter intrusion prevention device will be described in detail below, and explanations of the other configurations will be omitted as well-known technical means can be adopted as appropriate. In the first embodiment, a ball joint boot 15 is assumed as an example of a foreign matter intrusion prevention device.

[0015] The ball joint boot 15 is composed of an annular (large diameter annular) one end connection portion 15a connected to the outer periphery of the rack housing 17, an annular (small diameter annular) other end connection portion 15b connected to the outer periphery of the tie rod 13, and a hollow cylindrical bellows portion 15c which is integrally formed and communicates between the one end connection portion 15a and the other end connection portion 15b and covers the ball joint portion provided between the end of the rack 11 and the end of the tie rod 13.

[0016] The ball joint boot 15 of this embodiment is made of ethylene propylene rubber (EPDM), and the ethylene propylene rubber (EPDM) used in this embodiment is characterized in that it has the following rubber composition.

[0017] Ethylene propylene rubber (ethylene propylene non-conjugated diene rubber (terpolymer) EPDM: Ethylene-Propylene-Diene Methylene linkage) is a non-conjugated diene that can be vulcanized with ethylene, propylene, and sulfur as monomer components. The proportions of each monomer are 40 to 80% by weight of ethylene, 15 to 60% by weight of propylene, and 3 to 15% by weight of non-conjugated diene. As the non-conjugated diene, ethylidene norbornene (5-ethylidene-2-norbornene), dicyclopentadiene, and 1,4-hexadiene can be used, with ethylidene norbornene being the most suitable due to its high reactivity. Among the above-mentioned components, at least a portion of the ethylene and propylene are bioethylene and biopropylene, which are made from plant-derived bioethanol as the starting material. By using bioethylene and biopropylene as starting materials, the bio content (biomass content) of the ethylene propylene rubber is improved. Considering the contribution to the environment, a bio content of 20% or more is preferable, and if cost is disregarded, it can be increased to 85-97%. As the use of bioethanol increases and costs fall in the future, the bio-content can be increased. Biomass ethanol refers to ethanol produced by fermenting and distilling biomass such as sugar cane and corn. If the bio-content is 30%, it is possible to reduce carbon dioxide emissions by approximately 40% during the raw polymer manufacturing process. The ethylene propylene rubber of the present embodiment is obtained by heating an unvulcanized rubber, in which the raw material polymer having a certain level of bio-content described above is mixed with various compounding ingredients shown below, in a mold and vulcanizing the rubber to form a molded product.

[0018] The various compounding agents for EPDM are as follows: [Crosslinking agent] (1) Sulfur (2) Peroxides (dicumyl peroxide, etc.) [Reinforcement material] (1) Carbon black (FEF, SRF, etc.) (2) Silica (3) Clay [Anti-aging agent] (1) Substituted diphenylamines (2) N,N'-diphenyl-p-phenylenediamine (3) Polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (4) 4,4'-methylene-bis-(2,6-di-tert-butylphenol) [Vulcanization accelerator] (1) 2-Mercaptobenzothiazole (2) Dibenzothiazyl disulfide (3) Zinc salt of 2-mercaptobenzothiazole (4) Cyclohexylamine salt of 2-mercaptobenzothiazole (5) 2-(N,N'-Diethylthiocarbamoylthio)benzothiazole (6) 2-(4'-morpholinodithio)benzothiazole (7)N-Cyclohexyl-2-benzothiazyl sulfenamide (8) N,N-Dicyclohexyl-2-benzothiazyl sulfenamide (9) N-oxydiethylene-2-benzothiazyl sulfenamide (10)N-tert-butyl-2-benzothiazyl sulfenamide (11) Diethyl thiourea (12) Dibutyl thiourea (13) Tetramethylthiuram monosulfide (14) Tetramethylthiuram disulfide (15) Tetraethylthiuram disulfide (16) Dipentamethylenethiuram tetra or hexasulfide (17) Tetrakis(2-ethylhexyl)thiuram disulfide (18) Zinc dimethyldithiocarbamate (19) Zinc diethyl dithiocarbamate (20) Zinc di-n-butyl dithiocarbamate (21) Zinc ethylphenyl dithiocarbamate (22)Diethyl tellurium dithiocarbamate (23) Copper dimethyl dithiocarbamate (24)Iron dimethyl dithiocarbamate (25)Pentamethylenedithiocarbamic acid piperidine [Vulcanization accelerator] (1) Complex activated zinc oxide (2) Stearic acid [Rubber softener] Paraffin-based process oil Second embodiment

[0019] 2 and 3 show another embodiment of a foreign object intrusion prevention device used in the rack-and-pinion steering device 1. In FIG.

[0020] In the rack-and-pinion steering device 1, a gasket 21 is installed between the pinion shaft 9 and the pinion housing 19 as a device for preventing the intrusion of foreign matter. Grease is placed inside the pinion housing 19 to smooth the movement of the pinion shaft 9. This gasket 21 is provided to prevent the outflow of grease and to prevent the intrusion of water and dust, and one type of gasket 21 that is known is one that is made up of a metal reinforcing member (core) 21a and a rubber composition 21b.

[0021] The rubber composition 21b used in the gasket 21 of this embodiment is the same as the ethylene propylene rubber (EPDM) of the first embodiment described above, and therefore the detailed description thereof is hereby incorporated by reference. The gasket 21 of this embodiment is formed by vulcanizing and bonding a reinforcing member (core) 21a, to which a vulcanizing adhesive is applied in a semi-cured state in a mold having an internal space, to unvulcanized rubber, which is a mixture of a raw material polymer having a certain level of bio-content and various compounding ingredients, as described in the first embodiment above, by applying pressure and heating, thereby integrating the reinforcing member 21a and the rubber composition 21b. For the reinforcing member 21a, for example, a galvanized steel sheet whose surface has been further subjected to a chemical conversion treatment such as zinc phosphate treatment, is suitably used in order to improve adhesion.

[0022] Other than the fact that the gasket 21 is made using the ethylene propylene rubber of the present embodiment described above, any known configuration may be appropriately adopted, and other configurations are not to be construed in any particular limiting manner. In the figure, reference numeral 23 denotes a cover member, and since this cover member 23 is also one of the foreign matter intrusion prevention members, it is also possible to apply the present invention to this cover member 23, and therefore the cover member 23 can be made using the ethylene propylene rubber (EPDM) of the first embodiment, as in this embodiment.

[0023] The present invention is applicable to all devices other than the ball joint boot 15 and the gasket 21 that are used as foreign matter intrusion prevention devices for the steering device 1. (Example of embodiment)

[0024] Hereinafter, an embodiment of the present invention will be described. Base rubber of the rubber composition constituting the steering boot: Table 1 ·Boot structure: Figure 1 [Boots manufacturing] An unvulcanized rubber composition made of the base rubber shown in Table 1 is heated in a mold and vulcanized to form a molded product.

[0025] [Table 1]

[0026] The biomass EPDM of this embodiment, which constitutes the ball joint boot of a rack-and-pinion steering device, uses bio-polyethylene and bio-polypropylene as its raw materials, making it more environmentally friendly than conventional EPDM that is made only from petroleum-derived components and has a bio-content of 0%, and can be used to create a steering device that contributes to carbon neutrality. Since the chemical composition of biomass EPDM with a high bio content remains unchanged, there is no difference in its properties, such as chemical resistance to water and brake oil, mechanical properties, and heat resistance, compared to EPDM made only from conventional petroleum-derived raw materials.

[0027] In the embodiment of the present invention, a rack-and-pinion steering device has been described, but the present invention is not limited to this and can be applied to electric power steering devices and manual steering devices. As for electric power steering devices, the present invention can be used in power steering devices with various assist mechanisms, such as a single-pinion electric power steering device, a dual-pinion electric power steering device, and a rack-and-pinion electric power steering device. [Industrial Applicability]

[0028] The present invention can be applied to any steering device having a foreign object intrusion prevention device. [Explanation of symbols]

[0029] 1 Steering device 3 Steering shaft 5 Intermediate shaft 7 Pinion 9 Pinion shaft 11 Rack 15 Ball joint boots 17 Rack Housing 19 Pinion housing 21 Gasket 23 Cover member

Claims

1. In a steering device equipped with a foreign object intrusion prevention device, A steering device characterized in that the foreign matter intrusion prevention device is made of a rubber composition containing biomass ethylene propylene rubber, in which at least a portion of the raw material ethylene and propylene is bioethylene and biopropylene derived from plant-derived bioethanol.

2. 2. The steering device according to claim 1, wherein the foreign object intrusion prevention device is at least one of a boot and a gasket.

3. 3. The steering device according to claim 1, wherein the biomass ethylene propylene rubber has a bio content of 20% or more.

Images