US 5,687,808 AGranted

Four wheel drive mechanism

AssigneeNissan Motor Co., Ltd.

InventorsJun Watanabe, Kenro Takahashi, Yorihito Nakao, Shigeru Kamegaya, Naohiko Inoue

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Abstract

A torque is transmitted between a fluid pressure pump driven together with drive of a vehicle, and a fluid pressure motor that rotates together with driven wheels. The fluid pressure motor has two ports, and rotates in accordance with the direction of fluid supply to the ports. Fluid is circulated from one port to the other according to the input of rotation torque from the driven wheels. A high pressure flowpath connected to the pump outlet, and a low pressure flowpath connected to the pump inlet, are connected to these ports, and the connection direction is reversed when the rotation direction of the drive wheels is reversed. The low pressure flowpath is therefore always at low pressure regardless of the rotation direction of the drive wheels, and by controlling the pump supply flowrate so as not to exceed a predetermined value, torque is not transmitted when the vehicle is running at high speed.

Claims34

Dependent claims

A four wheel drive mechanism, comprising:

drive wheels driven by an engine;
driven wheels that rotate due to contact with a road surface;
fluid pressure pump means driven together with said drive wheels, said pump means being provided with a fluid inlet and outlet, and pressurizing a fluid aspirated from said inlet so as to discharge it from said outlet;
fluid pressure motor means rotating together with said driven wheels and having two ports for aspirating and discharging said fluid, said motor means driving said driven wheels by supplying a pressurized fluid to one of said ports while on the other hand circulating said fluid from one port to the other port according to an input of rotation torque from said driven wheels and having a larger flow rate than said pump means when a rotation speed of said drive wheels is equal to a rotation speed of said driven wheels;
a high pressure flowpath connected to said outlet of said pump means;
a low pressure flowpath connected to said inlet of said pump means;
means for connecting said high pressure flowpath and low pressure flowpath to said two ports of said motor means, said connecting means reversing a direction of connection when a rotation direction of said drive wheels is reversed;
means for limiting a torque transmitted from said pump means to said motor means so as not to exceed a predetermined value;
means for decreasing a fluid discharge volume of said pump means per unit rotation of said pump means according to an increase of the rotation speed of said drive wheels when said rotation speed is higher than a predetermined speed;
and
capacity control means for varying a fluid circulation volume of said motor means per unit rotation of said motor means according to a flowrate of said low pressure flowpath.

8 more elements

A four wheel drive mechanism, comprising:

drive wheels driven by an engine;
driven wheels that rotate due to contact with a road surface;
fluid pressure pump means driven together with said drive wheels, said pump means being provided with a fluid inlet and outlet, and pressurizing a fluid aspirated from said inlet so as to discharge it from said outlet;
fluid pressure motor means rotating together with said driven wheels and having two ports for aspirating and discharging said fluid, said motor means driving said driven wheels by supplying a pressurized fluid to one of said ports while on the other hand circulating said fluid from one port to the other port according to an input of rotation torque from said driven wheels;
a high pressure flowpath connected to said outlet of said pump means;
a low pressure flowpath connected to said inlet of said pump means;
means for connecting said high pressure flowpath and low pressure flowpath to said two ports of said motor means, said connecting means reversing a direction of connection when a rotation direction of said drive wheels is reversed;
means for limiting a torque transmitted from said pump means to said motor means so as not to exceed a predetermined value,
wherein said motor means has a larger flowrate than said pump means when a rotation speed of said drive wheels is equal to a rotation speed of said driven wheels, and said mechanism further comprises a flowpath provided with a check valve for supplying said fluid from said low pressure flowpath to said high pressure flowpath.

6 more elements

Dependencies are inferred from the claim text.