Layout structure for motor-driven power steering unit controller

To provide a layout structure for a motor-driven power steering unit controller configured to take into account the water level at which submergence of the vehicle is expected to occur. In a vehicle including a steering shaft rotatably supported on a vehicle body frame, a steering bar handle attached to the upper end of the steering shaft, a motor-driven power steering unit mounted onto the lower end of the steering shaft, and at least two front wheels, a controller for controlling the motor-driven power steering unit is laid out on the front side relative to the steering shaft and above a horizontal line indicative of the submergence limit of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-288492, filed in Japan on Sep. 30, 2005, the entirety of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a layout structure for a motor-driven power steering unit controller.

2. Description of Background Art

A motor-driven power steering unit controller according to the background art includes a controller for controlling a drive motor (see, for example, Japanese Patent No. 2663454).

FIG. 6 of Japanese Patent No. 2663454 shows a controller26for controlling a drive motor23provided in a motor-driven power steering device. A saddle-ride type all-terrain vehicle shown in FIG. 1 of Japanese Patent No. 2663454 does not illustrate the above-mentioned controller26, so that the specific layout of the controller26is not clear.

The saddle-ride type vehicle, for running on bad-conditioned grounds, may run across or longitudinally through a river, for example. Therefore, various component parts with which the vehicle is equipped, particularly electrical equipments, must be laid out taking into account the water surface on the assumption that the vehicle may run across or longitudinally through rivers and the like.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a layout structure for a component part (a motor-driven power steering unit controller) taking into account the water surface on the assumption that the vehicle may run across or longitudinally through rivers and the like.

According to a first aspect of the present invention, in a vehicle comprising a steering shaft rotatably supported on a vehicle body frame, a steering bar handle attached to the upper end of the steering shaft, a motor-driven power steering unit mounted onto the lower end of the steering shaft, and at least two front wheels, a controller for controlling the motor-driven power steering unit is disposed on the front side relative to the steering shaft and above a submergence limit of the vehicle.

In operation of the layout of the controller, the controller is disposed on the front side relative to the steering shaft and on the upper limit of the submergence limit of the vehicle. Therefore, it is ensured that where the submergence of the controller is expected, the driver can drive the vehicle while checking the positional relationship between the controller provided on the front side relative to the steering shaft and the water surface. Furthermore, since the controller is located at a high position above the submergence limit, the controller can be prevented from being submerged.

According to a second aspect of the present invention, the controller is disposed on the front side relative to an oil cooler for cooling engine oil.

In operation of the layout of the controller, when warmed engine oil is circulated through the oil cooler, the heat of the oil cooler is carried rearwards from the oil cooler by the running airflow, so that the controller laid out on the front side relative to the oil cooler is not influenced by the heat.

According to a third aspect of the present invention, the lower end of the steering shaft is rotatably supported on a housing added, in a turret-like form, to the motor-driven power steering unit. A rear wall of the housing is provided with an opening, and a wire for connecting the motor-driven power steering unit and the controller is passed through the opening.

In operation of the opening, with the opening provided in the rear wall of the housing, flying stones, rainwater, dust and the like coming from the front side of the vehicle will not easily enter into the housing. In addition, since the wire for connecting the motor-driven power steering unit and the controller is passed through the opening, the laying of the wire can be conducted easily.

According to a fourth aspect of the present invention, the submergence limit is at an atmosphere opening end of an air vent tube provided for a carburetor, or at a tail pipe opening of a muffler.

In operation of the submergence limit, the configuration in which the submergence limit is at the atmosphere opening end of the air vent tube or at the tail pipe opening ensures that the submergence of the inside of the carburetor or the inside of the muffler can be obviated by paying attention to the submergence limit at the time of running through rivers, damp grounds and the like.

According to the first aspect of the present invention, the controller for controlling the motor-driven power steering unit is laid out on the front side relative to the steering shaft and above the submergence limit of the vehicle, so that the vehicle can be driven while observing the controller and the water surface. In addition, with the controller disposed above the submergence limit, the controller can be prevented from being submerged.

According to the second aspect of the present invention, the controller is laid out on the front side relative to the oil cooler for cooling the engine oil, so that it is ensured that the controller is less liable to receive the heat of the oil cooler.

According to the third aspect of the present invention, the lower end of the steering shaft is rotatably supported on the housing added, in a turret-like form, to the motor-driven power steering unit, the rear wall of the housing is provided with the opening, and the wire for connecting the motordriven power steering unit and the controller is passed through the opening, so that it is ensured that flying stones, rainwater, dust and the like would not easily enter into the housing. In addition, the opening provided in the housing permits easy laying of the wire.

According to the fourth aspect of the present invention, the submergence limit is at the atmosphere opening end of the air vent tube provided for the carburetor, or at the tail pipe opening of the muffler, so that submergence of the inside of the carburetor or the inside of the muffler can be prevented by paying attention to the submergence limit during running.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will now be described with reference to the accompanying drawings. The same reference numerals will be used to identify the same or similar elements throughout the several views. It should be noted that each of the drawings should be viewed in the direction of orientation of the reference numerals.

FIG. 1is a side view of a vehicle configured by adopting a layout structure for a motor-driven power steering unit controller according to the present invention. An all-terrain vehicle10as the vehicle is a four-wheel-drive vehicle in which a power unit14composed of an engine12and a transmission13is mounted on a central portion of a vehicle body frame11. A front final speed reduction gear17is connected to a front portion of the transmission13through a front propeller shaft16. Left and right front wheels18,18are connected to the front final speed reduction gear17through a drive shaft (not shown). A rear final speed reduction gear22is connected to a rear portion of the transmission13through a rear propeller shaft21. Left and right rear wheels23,23are connected to the rear final speed reduction gear22through a drive shaft (not shown). A motor-driven power steering unit24is provided for alleviating a steering force for steering the front wheels18,18. In the figure, reference numeral25identifies a controller for controlling the motor-driven power steering unit24, and is laid out on the front side relative to an oil cooler26and above a horizontal line27indicating the submergence limit.

The horizontal line27is a line passing through the submergence limit set at the position of an opening (more specifically, the lower end of the opening) of a tail pipe69aof a muffler69which will be described later.

The vehicle body frame11includes a left-right pair of upper main frames31,32(only reference numeral31on the viewer's side is shown) that extend in the front-rear direction. A front frame33that has an inverted U-shape in front view is connected to the front ends of the upper main frames31,32. A left-right pair of lower main frames34,36(only reference numeral34on the viewer's side is shown) is connected respectively to the lower ends of the front frame33and intermediate portions of the upper main frames31,32. A left-right pair of V-shaped front upper frames41,42(only reference numeral41on the viewer's side is shown) that are laid sideways are connected respectively to the upper end of the front frame33and the upper main frames31,32for rotatably supporting an upper portion of a steering shaft38fitted with a steering bar handle (handle bar)37at the upper end thereof A left-right pair of inclined frames43,44(only reference numeral43on the viewer's side is shown) extend rearwardly downwards from the front ends of the upper main frames31,32to be connected to the lower main frames34,36. A left-right pair of sub inclined frames46,47(only reference numeral46on the viewer's side is shown) is bridgingly connected respectively to intermediate portions of the inclined frames43,44and the front frame33to thereby support a lower portion of the motor-driven power steering unit24.

Reference numeral55identifies a front carrier. Reference numeral56identifies a front fender covering the upper and rear sides of the front wheels18. Reference numeral57identifies a fuel tank. Reference numeral58identifies a seat. Reference numeral61identifies a rear carrier. Reference numeral62identifies a carburetor connected to the rear portion side of a cylinder head63of the engine12. Reference numeral64identifies a cylinder portion projecting to the upper side of the power unit24and including the cylinder head63. Reference numeral66identifies an air cleaner connected to the carburetor62through a connecting tube67. Reference numeral68identifies an exhaust pipe that extends toward the vehicle rear side from a front portion of the cylinder head63. Reference numeral69identifies the muffler connected to the rear end of the exhaust pipe68. Reference numeral69aidentifies a tail pipe provided at the rear end of the muffler69. Reference numeral71identifies a swing arm for supporting the rear wheels23,23swingably relative to the lower main frames34,36. Reference numerals72,72(only reference numeral72on the viewer's side is shown) identify a left-right pair of rear cushion units bridgingly attached to the swing arm71and the upper main frames31,32. Reference numeral73identifies a body side cover disposed on lateral sides of the power unit14. Reference numeral74identifies a rear fender covering the upper and front sides of the rear wheels23. Reference numeral75identifies a step floor. Reference numeral76identifies a skid plate covering front lower portions of the left and right lower main frames34,36and the front side of the lower main frames34,36.

FIG. 2is a side view of an essential part of the vehicle according to the present invention, and shows that an upper portion of the vehicle body frame11rotatably supports an intermediate portion of the steering shaft38. An input shaft81provided at an upper portion of the motor-driven power steering unit24is connected to the lower end of the steering shaft38. A lower portion of the motor-driven power steering unit24is mounted onto a lower portion of the vehicle body frame11. A lower portion of the vehicle body frame11rotatably supports an output shaft82provided at a lower portion of the motor-driven power steering unit24.

The steering shaft38is composed of an upper shaft85fitted with the steering bar handle37(seeFIG. 1) at the upper end thereof. A lower shaft86has an upper end that is serration connected to the lower end of the upper shaft85and a lower end that is serration connected to the input shaft81.

The upper shaft85is a member rotatably attached, through an upper bearing portion91, to a steering support bracket88bridgingly attached to the left and right front upper frames41,42. The upper shaft85is provided at its upper end with a female serration85afor connection with a male serration86aprovided at the upper end of the lower shaft86. The upper shaft85is also provided with an expanding slot85bextending in the axial direction and communicating with both the female serration85aside and the outer peripheral surface side. Projected portions85c,85d(only reference numeral85don the depth side is shown) are integrally formed respectively at both edge portions of the expanding slot85b. Bolt insertion holes85eare bored in the projected portions85c,85d. Bolts92are passed through the bolt insertion holes85e. Nuts (not shown) are screw engaged with the tip ends of the bolts92, whereby the lower end of the upper shaft85fastens the upper end of the input shaft81. Incidentally, reference numeral86A identifies a positioning portion provided in the lower shaft86for positioning by putting the tip end of the upper shaft85into abutment thereon.

The steering support bracket88is composed of a cross member93bridgingly connected to the front upper flames41,42. Left and right boss portions94,94(only reference numeral94on the viewer's side is shown) are attached to the cross member93. Bolts95are screw engaged with the boss portions94,94, whereby the upper bearing portion91is fixed.

The upper bearing portion91is composed of a bush (not shown) slidably fitted over the upper shaft85, and a pair of metallic holders97,97for holding the bush.

The lower shaft86is provided at a lower portion with a shaft portion86b, and at an intermediate portion with an L-shaped projected portion86cthat projects rearwards and is L-shaped in section. The shaft portion86bis provided with a female serration86dfor connection with a male serration81aformed at the tip end of the input shaft81.

The motor-driven power steering unit24has, annexed thereto, a housing101covering an upper portion thereof. The housing101is a member having a lower portion that is attached to a gear case102of the motor-driven power steering unit24by a plurality of bolts103and an upper portion that rotatably supports the shaft portion86bof the lower shaft86through an intermediate bearing portion104.

The intermediate bearing portion104is composed of a multi-row type upper bearing107fitted in a hole101aopened in an upper portion of the housing101and fitted over the shaft portion86b. A stop ring108positions one end of the upper bearing107. A seal member111is fitted in one end portion of the hole101aadjacently to the stop ring108. A collar112is fitted over the shaft portion86band abuts on the other end of the upper bearing107. A nut113is screw engaged with a male screw86fat the tip end of the shaft portion86bto thereby press and fix the other end of the upper bearing107through the collar112. Incidentally, reference numeral86B is a positioning portion formed in the shaft portion86bfor positioning by putting one end of the upper bearing107into abutment thereon.

The motor-driven power steering unit24is composed of the above-mentioned input shaft81and output shaft82. A torque sensor portion121detects a steering torque. A power assist portion122generates power for assisting a steering force. The power assist portion122is controlled by a controller (not shown), based on the steering torque detected by the torque sensor portion121and the like. The torque sensor portion121has a torsion bar126for connecting the input shaft81and the output shaft82.

When the input shaft81is rotated by an operation on the steering bar handle37(seeFIG. 1), a relative rotational angle is generated between the input shaft81and the output shaft82, and the torsion bar126is twisted. The twisting amount (torsion) is converted into a torque, whereby the steering torque is determined.

The power assist portion122is composed of an electric motor128. A clutch (not shown) and a speed reduction gear (not shown; composed of a worm gear and a worm wheel) are interposed between an output shaft of the electric motor128and the output shaft82.

The motor-driven power steering unit24has a configuration in which the gear case102on the front side relative to the output shaft82is attached to a plate-like lower bracket131provided at the sub inclined frames46,47, through a front support member132by a bolt133. The gear case102on the rear side relative to the output shaft82is attached by a bolt136to a rear support member134provided at the sub inclined frames46,47. The motor-driven power steering unit24is a member in which a lower portion of the gear case102is supported by the front support member132and the rear support portion134at two front and rear positions, with the output shaft82therebetween.

The controller controls the power assist portion122, based on the steering torque detected by the torque sensor portion121, a steering angle detected by a steering angle sensor (not shown), the vehicle velocity of the all-terrain vehicle10(seeFIG. 1), and the like.

A lower bearing portion140for rotatably supporting the output shaft82includes a shaft support member141attached to a central portion of the lower bracket131. An automatic center adjusting type lower bearing142is attached to the shaft support member141so as to rotatably support the output shaft82. A seal member143protects the lower bearing142from dust and the like. Incidentally, reference numeral145identifies a collar. The shaft support member141is provided on the vehicle front side with a lower projected portion141athat projects to the lower side substantially along the output shaft82.

Reference numeral147identifies a center arm, which is provided with a female spline147afor spline connection with a male spline82aformed at a lower end portion of the output shaft82. Reference numeral151identifies a ball joint provided at its end portion with a bolt portion151a, which is attached to a rear portion of the center arm147by a nut152. Reference numeral154identifies a nut, which is screw engaged with a male screw provided at the tip end of the output shaft82, whereby the center arm147is fixed to the output shaft82.

The lower projected portion141of the shaft support member141and the center arm147constitute a lower steering handle stopper156. Incidentally, reference numeral158identifies a wire for connection between the motor-driven power steering unit24and the controller25(seeFIG. 1).

FIG. 3is a side view of a second essential part of the vehicle according to the present invention, and shows that an upper bracket171is attached to an upper portion of the front frame33. An oil cooler26that cools lubricating oil in the power unit14(seeFIG. 1) and an electrical equipment storage box174are attached to the upper bracket171through an upper stay172. The controller25for the motor-driven power steering unit24is contained in the electrical equipment storage box174. Incidentally, reference numerals176and177identify pipes for circulating the engine oil in the engine12into the oil cooler26.

The electrical equipment storage box174, particularly the controller25therein, is disposed on the vehicle front side relative to the oil cooler26and above the horizontal line27indicative of the limit in regard of submergence of the vehicle, i.e., the submergence limit.

A horizontal line180passing through the lower ends31b,32b(only reference numeral31bon the viewer's side is shown) of upper straight portions31a,32a(only reference numeral31aon the viewer's side is shown) of the upper main frames31,32(only reference numeral31on the viewer's side is shown) is located above the horizontal line27passing through the submergence limit. The controller25is located above the horizontal line180.

The submergence limit is at opening ends (namely, openings178a,179a(reference numeral179ais not shown)) of air vent tubes178,179for opening the inside of a float chamber (not shown) inside the carburetor62to the atmosphere, or at the tail pipe69a(seeFIG. 1) of the muffler69(seeFIG. 1). Between a horizontal line185and the horizontal line27passing through the lower ends of the openings178a,179a, the horizontal line27located at the lowermost position serves as the submergence limit of the vehicle.

The air vent tube178has one end portion connected to the right side surface of the carburetor62, and has the opening178aat the other end portion opened on the left side surface side of the carburetor62. Similarly, the air vent tube179has one end portion179bconnected to the left side surface of the carburetor62, and has the opening179aat the other end portion opened on the right side surface side of the carburetor62. The lower ends of the openings178a,179aare at the same height.

InFIG. 3, part of the vehicle component parts is omitted, for easy comparison between the height of the openings178a,179aof the air vent tubes178,179of the carburetor62and the height of the controller25.

FIG. 4is a front view of an essential part of the vehicle according to the present invention, and shows that the housing101is attached to the motor-driven power steering unit24by a plurality of bolts103. An upper portion of the motor-driven power steering unit24is covered with the housing101. With the upper portion of the motor-diven power steering unit24thus covered with the housing101, the motor-driven power steering unit24can be protected from flying stones, rainwater, dust and the like.

FIG. 5is a plan view of an essential part of the vehicle according to the present invention, and shows that an upper portion of the housing101and the L-shaped projected portion86cof the lower shaft86constitute an upper steering handle stopper161for restricting the rotating range of the steering bar handle37.

The operation of the layout structure for the controller25as above-described will be described below.FIGS. 6(a) and6(b) are operation diagrams showing the layout structure for the controller according to the present invention.

InFIG. 6(a), during running of the vehicle, the temperature of the engine oil in the engine is raised due to the operation of the engine. In view of this, the oil is circulated in the oil cooler26to release heat, whereby the engine oil is cooled. The heat of the oil cooler26is carried toward the rear side of the oil cooler26as indicated by arrows A and B by the running airflow coming from the vehicle front side as indicated by the void arrow. Therefore, there is no fear that the heat of the oil cooler26might influence the controller25in the electrical equipment storage box174.

InFIG. 6(b), the rear wall101hof the housing101covering an upper portion of the motor-driven power steering unit24is provided with an opening101j. A wire158for connection between the motor-driven power steering unit24and the controller25is passed through the opening101j. Therefore, it can be made difficult for flying stones, rainwater, dust and the like to enter into the housing101. In addition, with the housing101provided with the opening101j, the laying of the wire158can be carried out readily.

In addition, even if the water surface181in the case where the vehicle is submerged has reached the horizontal line27indicating the submergence limit of the vehicle, immersion of the controller25in water can be obviated, since the controller25is located above the horizontal line27and the controller25is contained in the electrical equipment storage box174which is sealed.

As shown inFIGS. 1 and 6above, according to the present invention, in the all-terrain vehicle10as the vehicle including the steering shaft38rotatably supported on the vehicle body frame11, the steering bar handle37attached to the upper end of the steering shaft38, the motordriven power steering unit24mounted onto the lower end of the steering shaft38, and at least two front wheels18, the controller25for controlling the motor-driven power steering unit24is laid out on the front side relative to the steering shaft38and above the horizontal line27serving as the submergence limit of the all-terrain vehicle10.

With this configuration, the controller25is disposed on the front side relative to the steering shaft38, whereby the all-terrain vehicle10can be made to run while observing the controller25and the water surface181. Furthermore, with the controller25disposed above the horizontal line27of the all-terrain vehicle10, submergence of the controller25can be prevented from occurring.

According to the present invention, the controller25is laid out on the front side relative to the oil cooler26for cooling the oil for the engine12. This can ensure that the controller25is less liable to receive the heat of the oil cooler26.

According to the present invention, as shown inFIGS. 2 and 6, the lower end of the steering shaft38is rotatably supported by the housing101annexed, in a turret-like form, to the motor-driven power steering unit24, the rear wall101hof the housing101is provided with the opening101j, and the wire158for connection between the motor-driven power steering unit24and the controller25is passed through the opening101j. This ensures that flying stones, rainwater, dust and the like would not easily enter into the housing101, and the laying of the wire158is facilitated by the presence of the opening101jin the housing101.

According to the present invention, as shown inFIGS. 1 and 3, the horizontal line27as the submergence limit is at the atmosphere opening ends of the air vent tubes178,179provided for the carburetor62, or at the opening of the tail pipe69aof the muffler69. This ensures that submergence of the inside of the carburetor62or the inside of the muffler69can be obviated by paying attention to the horizontal line27as the submergence limit during running through a river, marshland, damp ground or the like.

The controller layout structure according to the present invention is preferable for use in a vehicle having a motor-driven power steering unit.