CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2019-140194, filed on Jul. 30, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a saddled vehicle including an inertial measurement unit.

Description of Related Art

An ABS (Antilock Brake System) may be provided in a motorcycle. An IMU (Inertial Measurement Unit) is used to control the ABS, for example. In the following description, the IMU is suitably referred to as an inertial sensor.

The inertial sensor includes an acceleration sensor, and detects acceleration exerted on the vehicle provided with the inertial sensor in the directions of three axes orthogonal to one another. Further, the inertial sensor includes a gyro sensor, and detects an angular velocity generated around each of the above-mentioned three axes in regard to the vehicle provided with the inertial sensor. The ABS is controlled based on at least part of a plurality of accelerations and a plurality of angular velocities detected by the inertial sensor. Thus, the braking force exerted on a front wheel or a rear wheel is adjusted according to a traveling state of the vehicle.

In a case where the inertial sensor is provided in the motorcycle, vibration generated from an engine may be transmitted to the inertial sensor depending on the attachment state of the inertial sensor. Further, vibration caused by the vertical movement of the front wheel or the rear wheel may be transmitted to the inertial sensor depending on the state of the road surface on which the motorcycle travels. The vibration reduces the detection accuracy of acceleration and an angular velocity by the inertial sensor.

As such, the configuration for reducing various types of vibration transmitted to the inertial sensor in the motorcycle has been proposed. For example, in the attachment structure of an inertial sensor described in JP 2017-13731 A, a floating bracket is fixed to a body frame via a vibration absorbing member. In this state, the inertial sensor is attached to a first attachment surface of the floating bracket, and an ABS unit is attached to a second attachment surface of the floating bracket.

BRIEF SUMMARY OF THE INVENTION

However, even in a case where the structure described in JP 2017-13731 A is applied, the detection accuracy of acceleration and an angular velocity by the inertial sensor may be reduced. Specifically, in the motorcycle described in JP 2017-13731 A, the inertial sensor is provided while being exposed to the outside of the motorcycle. Therefore, rainwater and dust are likely to adhere to the inertial sensor during traveling of the vehicle. The adherence of rainwater and dust to the inertial sensor may reduce the detection accuracy of inertia by the inertial sensor.

Further, in a case where the inertial sensor is located at a position where the inertial sensor is easily accessed from outside of the motorcycle, the position or orientation of the inertial sensor may be erroneously changed by a user of the motorcycle. With the structure described in JP 2017-13731 A, the inertial sensor is attached to a plate-shaped floating bracket and fixed to the body frame while being exposed. Therefore, in the motorcycle described in JP 2017-13731 A, it can be said that the inertial sensor is relatively easily accessible from outside of the motorcycle. The position and orientation of the inertial sensor in the motorcycle are defined so as to comply with the conditions designed in advance. Therefore, in a case where the position and orientation of the inertial sensor provided in the motorcycle are changed after the motorcycle is shipped from the factory, the acceleration and angular velocity to be detected are not detected.

Further, it is generally desirable to miniaturize a motorcycle. Therefore, no wasteful space is essentially provided in the motorcycle. Therefore, in a case where an electric appliance such as an inertial sensor is added to the motorcycle, it is necessary to secure a new installation space for installing the additional electric appliance. In this case, the size of the motorcycle is increased.

An object of the present invention is to provide a straddled vehicle enlargement of which to be caused by provision of an inertial measurement unit can be suppressed while high detection accuracy of inertia by the inertial measurement unit can be maintained.

Generally, a motorcycle is provided with a battery case that stores a battery. As such, in regard to the above-mentioned problem, the inventor of the present invention considered that it was possible to prevent the inertial measurement unit from being exposed to outside and increase difficulty in accessing the inertial measurement unit from outside of the motorcycle in a case where the inertial measurement unit was arranged in the battery case together with the battery. However, if the size of the battery case is increased for arranging the inertial measurement unit in the battery case, the height of a seat increases due to an increase in size of the battery case.

Further, the battery case is fixed to the body frame. The inertial measurement unit is smaller in weight than a battery, a hydraulic unit used for an ABS, and the like. Therefore, in a case where being fixed to the battery case, the inertial measurement unit is likely to vibrate together with an attachment portion of the battery case due to vibration transmitted from an engine, a front wheel or a rear wheel through the body frame.

As described above, in regard to the configuration for arranging the inertial measurement unit in the battery case together with the battery, the inventor of the present invention has encountered a new problem of an increase in height of the seat and vibration of the inertial measurement unit.

In regard to these points, the inventor of the present invention has noticed that there was a dead space between a rear suspension and a rear wheel in a vehicle front-and-rear direction and in a region in the vicinity thereof as a result of repeated examination. Thus, the inventor of the present invention has discovered that it was possible to arrange the inertial measurement unit in the battery case without an increase in height of the seat if this dead space could be effectively utilized as a space for installing the inertial measurement unit.

Further, the inventor of the present invention has noticed that vibration was unlikely to be transmitted from outside to the portion of the battery case to which the battery was fixed and the vicinity thereof due to the weight of the battery. As such, the inventor of the present invention has discovered that vibration generated in the inertial measurement unit could be reduced by the weight of the battery if the inertial measurement unit was fixed in the vicinity of the portion to which the battery was fixed in the battery case.

The inventor of the present invention has arrived at the present invention described below as a result of the series of above-mentioned examination.

(1) A straddled vehicle according to one aspect of the present invention includes a body frame, a seat that is arranged above the body frame and supported at the body frame, a battery, an inertial measurement unit, a resin battery case that stores the battery and the inertial measurement unit, and is fixed to the body frame to be located below the seat, a rear arm provided to extend rearwardly from the body frame, a drive wheel rotatably supported by the rear arm, and a rear suspension that is provided at a position farther forward than the drive wheel to extend obliquely downwardly from a position forward of the vehicle to a position rearward of the vehicle, and supports the rear arm at the body frame to be swingable in a vehicle up-and-down direction, wherein the battery case has a bottom portion that protrudes toward a position between the rear suspension and the drive wheel in a vehicle front-and-rear direction so as not to overlap with the rear suspension and the drive wheel in a side view of the vehicle while being most contracted due to absorbance of shock by the rear suspension, the inertial measurement unit is fixed to the bottom portion of the battery case, and the battery is fixed to the battery case at a position above the inertial measurement unit to overlap with at least part of the inertial measurement unit in a plan view of the vehicle.

In the straddled vehicle, the battery case is fixed to the body frame below the seat. The battery and the inertial measurement unit are stored in the battery case. The bottom portion of the battery case protrudes toward a position between the rear suspension and the drive wheel in the vehicle front-and-rear direction. With such a configuration, the battery case has high rigidity despite being formed of resin.

The inertial measurement unit is fixed to the bottom portion of the battery case, whereby the dead space that is outside of the range of motion of the rear suspension and the range of motion of the drive wheel is effectively utilized as a space for installing the inertial measurement unit. Therefore, the inertial measurement unit can be arranged in the battery case without an increase in height of the seat.

Further, with the above-mentioned configuration, the battery is fixed to the battery case at a position above the inertial measurement unit so as to overlap with at least part of the inertial measurement unit in the plan view of the vehicle. In this case, the portion to which the battery is attached is in close proximity to the other portion to which the inertial measurement unit is attached in the battery case. Thus, even in a case where vibration is transmitted from the body frame to the battery case during traveling of the vehicle, vibration of the portion to which the inertial measurement unit is attached in the battery case is suppressed due to the weight of the battery. Further, because being made of resin, the above-mentioned battery case absorbs part of vibration transmitted from the body frame. Therefore, vibration generated in the inertial measurement unit is reduced.

Further, with the above-mentioned configuration, the battery and the seat are present above the inertial measurement unit. This increases the difficulty of accessing the inertial measurement unit from outside of the straddled vehicle. Further, because the inertial measurement unit is provided inside of the battery case, rainwater or dust that is scattered outside of the straddled vehicle during traveling of the vehicle is prevented from adhering to the inertial measurement unit.

As a result, an increase in size of the vehicle due to provision of the inertial measurement unit can be suppressed while high detection accuracy of inertia by the inertial measurement unit is maintained.

(2) The battery may be fixed to overlap with the entire inertial measurement unit in the plan view of the vehicle. Thus, the difficulty in accessing the inertial measurement device from outside of the straddled vehicle is further increased.

(3) A distance between the battery and the inertial measurement unit may be smaller than a half of thickness of the battery in a vehicle up-and-down direction.

In this case, the portion to which the battery is attached becomes closer to the other portion to which the inertial measurement unit is attached in the battery case. Thus, the vibration of the other portion to which the inertial measurement unit is attached in the battery case is further suppressed due to the weight of the battery.

Further, it is not necessary to ensure the large installation space for the battery and the inertial measurement unit in a vehicle up-and-down direction. This can suppress an increase in size of the battery case in the vehicle up-and-down direction, whereby an increase in height of the seat can be suppressed.

(4) The straddled vehicle may further include a hydraulic unit that is stored in the battery case and is fixed to the battery case to be adjacent to the battery.

In this case, the hydraulic unit is fixed to the battery case to be adjacent to the battery. Thus, the vibration generated in the vicinity of the inertial measurement unit in the battery case is reduced by the weight of the battery and the hydraulic unit. Further, because the hydraulic unit is stored in the battery case, an increase in height of the seat due to provision of the hydraulic unit outside of the battery case is suppressed.

(5) The inertial measurement unit may be fixed to the bottom portion of the battery case via a first shock buffering member.

In this case, transmission of the vibration generated in the battery case due to traveling of the vehicle to the inertial measurement unit is suppressed. Thus, the inertia of the vehicle can be measured with high accuracy.

(6) The battery case may be fixed to the body frame via a second shock buffering member.

In this case, transmission of the vibration generated in the body frame due to traveling of the vehicle to the battery case is suppressed. Thus, the inertia of the vehicle can be measured with higher accuracy.

(7) The inertial measurement unit may be arranged to overlap with a vehicle central axis extending in the vehicle front-and-rear direction in the plan view of the vehicle. Thus, the inertia of the vehicle can be measured more accurately.

(8) The inertial measurement unit may be fixed in the battery case so as not to be inclined with respect to a horizontal plane by 15° or larger with the vehicle vertically standing up. Thus, the inertia of the vehicle can be measured more accurately.

(9) The straddled vehicle may further include a metallic fixing mechanism that is attached to the battery case, and is configured to be able to fix the battery to the battery case and detach the battery from the battery case.

In this case, the battery is firmly fixed to the battery case as compared to the case where the battery is fixed to the battery case by an elastic member such as rubber. Thus, generation of vibration in the bottom portion of the battery case due to movement of the battery with respect to the battery case during traveling of the vehicle is suppressed. As a result, the inertia of the vehicle can be measured more accurately.

(10) The battery may have a first surface and a second surface adjacent to each other, the fixing mechanism may include a first fixing member having a first end and a second end, and a second fixing member having a third end and a fourth end, the second end of the first fixing member may be connected to the third end of the second fixing member by a hinge, the first end of the first fixing member may be attached to the battery case such that the first fixing member extends along the first surface of the battery, the second fixing member may be provided to be able to be come close to and move away from the second surface of the battery by rotating with respect to the first fixing member with use of the hinge, and the fourth end of the second fixing member may be configured to be fixable to and detachable from the battery case with the second fixing member being in close proximity to the second surface of the battery.

In this case, the battery can be easily and firmly fixed to the battery case by the first fixing member and the second fixing member. Further, the battery fixed to the battery case can be easily removed.

(11) The straddled vehicle may further include an operation element that performs an operation in regard to the vehicle, and a controller that controls the operation element based on a result of inertial measurement of the vehicle by the inertial measurement unit. Thus, the operation relating to the vehicle is appropriately controlled according to the state of the vehicle.

Other features, elements, characteristics, and advantages of the present invention will become more apparent from the following description of preferred embodiments of the present invention with reference to the attached drawings.

