CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-109767 filed Jun. 25, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a work vehicle.

2. Description of the Related Art

A work vehicle is available that includes a wheel support member that supports a pair of left and right travel wheels, a link mechanism that is provided spanning between a vehicle body and the wheel support member, and that supports the wheel support member such that the wheel support member can be raised and lowered, a suspension mechanism that is provided spanning between a suspension support section formed on the vehicle body and the wheel support member, and that elastically supports the wheel support member, and a lateral link that is coupled to a vehicle body-side support section formed on the vehicle body and a wheel-side support section formed on the wheel support member, and that restricts lateral movement of the wheel support member.

An example of a work vehicle of this kind is the work vehicle described in JP 2012-51506A (Patent Document 1). In this work vehicle, a pair of left and right auxiliary frames and a pair of rear axle cases are provided as the wheel support member, an upper arm and a lower arm are provided as the link mechanism, a suspension unit is provided as the suspension mechanism, and a lateral rod is provided as the lateral link.

SUMMARY OF THE INVENTION

In the above-described work vehicle, the link mechanism includes an upper link having a front end portion supported by a link support section formed on the vehicle body so as to be swingable up and down about an upper pivotal support axis, and a rear end portion coupled to the wheel support member so as to be swingable about an upper coupling axis relative to the wheel support member, and a lower link having a front end portion supported by the link support section so as to be swingable up and down about a lower pivotal support axis, and a rear end portion coupled to the wheel support member so as to be swingable about a lower coupling axis relative to the wheel support member. In such a work vehicle, a moment due to the weight of the wheel support member and the wheels is generated in the link support section and so forth. Accordingly, a large load may be imposed on the link mechanism and a member that supports the link mechanism.

Therefore, there is a need for a work vehicle in which a moment due to the weight of the wheel support member and the wheels is less likely to be generated.

A work vehicle according to the present invention includes a wheel support member including an axle that supports a pair of left and right travel wheels; a link mechanism that is provided spanning between a vehicle body and the wheel support member, and that supports the wheel support member such that the wheel support member can be raised and lowered; and a suspension mechanism that is provided spanning between a suspension support section formed on the vehicle body and the wheel support member, and that elastically supports the wheel support member, wherein Expression (1) is satisfied:
Sin(θ+α)·cos θ>0  (1)

where θ is an angle formed by the suspension mechanism and a vertical line, and α is an angle formed by a straight line passing through a supporting location of the suspension mechanism for the wheel support member and the axle and a vertical line.

A moment due to the weight of the wheels and the wheel support section is generated around the axle. By satisfying Expression (1) above, a moment in a direction opposite to that of the moment due to the weight of the wheels and the wheel support section can be generated by a reaction force due to the suspension mechanism. Accordingly, the generated moment can be reduced. As a result, the load imposed on members that support the wheels such as a link mechanism can be reduced.

In the above-described configuration, it is preferable that one end of the suspension mechanism is supported by the suspension support section so as to be swingable about a first axis, and another end of the suspension mechanism is supported by the wheel support section so as to be swingable about a second axis.

With the above-described configuration, a reaction force due to the suspension mechanism can be suitably generated.

In the above-described configuration, it is preferable that the suspension mechanism includes a suspension spring, and a damper that is passed through the suspension spring, and one end of the damper is supported by the suspension support section so as to be swingable about a lateral axis, and another end of the damper is supported by the wheel support section so as to be swingable about a lateral axis.

With the above-described configuration, the suspension spring can suitably generate a reaction force.

In the above-described configuration, it is preferable that Expression (4) below is satisfied:
α=tan−1{(Ws2·tan θ2−Ws1·tan θ1)/(Ws1−Ws2)}  (4)

where Ws1 is a reaction force of the suspension spring under a first loading condition, θ1 is a value of θ under the first loading condition, Ws2 is a reaction force of the suspension spring under a second loading condition in which a load weight is larger than the first loading condition, and θ2 is a value of θ under the second loading condition.

By satisfying the above-described configuration, the generated moment can be suitably reduced, in particular, between the first loading condition and the second loading condition.

In the above-described configuration, it is preferable that Expression (5) below is satisfied:
L=lw·Wu/Ws1×(Ws1−Ws2)/{Ws2·tan θ2−Ws1·tan θ1+(Ws1−Ws2)·sin α}  (5)

where L is a distance between the first axis and an axis of the axle, and lw is a horizontal distance between the axis of the axle and a center of gravity of a spring lower portion that is a portion suspended from the suspension mechanism.

With the above-described configuration, the moment generated under the first loading condition and the second loading condition can be 0. In addition, the moment generated between the first loading condition and the second loading condition can be suitably reduced.

