Belt type continuously variable transmission and vehicle including the same

Abstract

A hydraulic circuit includes a first control valve that controls a hydraulic pressure of a first oil chamber of a CVT; a lubrication circuit whose hydraulic pressure changes in accordance with an engine rotational speed so that the higher the engine rotational speed, the higher the hydraulic pressure; and a fail-safe valve including an electromagnetic four-way valve. During normal operation, the fail-safe valve is set to a first state in which the first control valve and the first oil chamber communicate with each other. At a time of failure, the fail-safe valve is switched to a second state in which at least the first oil chamber and the lubrication circuit communicate with each other.

1 - 10 . (canceled) 
     
     
         11 . A belt type continuously variable transmission to be installed on a vehicle including an engine, the belt type continuously variable transmission comprising:
 a first pulley which includes a pair of first sheaves facing each other and a first oil chamber that contains oil and in which a distance between the pair of first sheaves is adjusted by a hydraulic pressure of the first oil chamber so that the distance between the pair of first sheaves decreases as the hydraulic pressure of the first oil chamber increases;   a second pulley including a pair of second sheaves facing each other;   a belt wound around the first pulley and the second pulley; and   a hydraulic circuit connected to the first oil chamber; wherein   the hydraulic circuit includes:
 a control valve that controls the hydraulic pressure of the first oil chamber; 
 a pressure change circuit having a hydraulic pressure that changes in accordance with a rotational speed of the engine so that a higher rotational speed of the engine results in a higher hydraulic pressure in the pressure change circuit; and 
 a switching valve that is switched between a first state in which the control valve and the first oil chamber communicate with each other and a second state in which at least the first oil chamber and the pressure change circuit communicate with each other. 
   
     
     
         12 . The belt type continuously variable transmission according to  claim 11 , wherein the hydraulic circuit further includes an oil pump that operates in accordance with the rotational speed of the engine, and the pressure change circuit communicates with a discharge-side portion of the oil pump via a pressure reducing mechanism. 
     
     
         13 . The belt type continuously variable transmission according to  claim 12 , wherein the pressure change circuit opens to a sliding portion of the engine or a sliding portion of the belt type continuously variable transmission. 
     
     
         14 . The belt type continuously variable transmission according to  claim 13 , wherein the hydraulic circuit further includes:
 another circuit through which the pressure change circuit and a suction-side portion of the oil pump communicate with each other; and   a relief valve provided in the another circuit and that opens when the hydraulic pressure of the pressure change circuit exceeds an upper limit.   
     
     
         15 . The belt type continuously variable transmission according to  claim 11 , wherein the hydraulic circuit further includes an orifice that reduces a flow of oil from the first oil chamber toward the pressure change circuit when the switching valve is set to the second state. 
     
     
         16 . The belt type continuously variable transmission according to  claim 11 , further comprising a controller programmed to transmit a control signal to each of the control valve and the switching valve; wherein
 the control valve is arranged so as to control the hydraulic pressure of the first oil chamber within a pressure range between minimum and maximum pressures upon receipt of the control signal from the controller, and so as to control the hydraulic pressure of the first oil chamber to the maximum pressure when the control valve receives no control signal from the controller;   the first state is a state in which the control valve and the first oil chamber communicate with each other and the first oil chamber and the pressure change circuit do not communicate with each other;   the second state is a state in which the control valve and the first oil chamber communicate with each other and the first oil chamber and the pressure change circuit communicate with each other; and   the switching valve is arranged so that the switching valve is set to the first state upon receipt of the control signal from the controller, and is set to the second state when the switching valve receives no control signal from the controller.   
     
     
         17 . The belt type continuously variable transmission according to  claim 16 , wherein the hydraulic circuit further includes an orifice that reduces a flow of oil from the control valve toward the first oil chamber when the switching valve is set to the second state. 
     
     
         18 . The belt type continuously variable transmission according to  claim 11 , wherein an area of a flow passage of the switching valve changes in accordance with a magnitude of the hydraulic pressure of the pressure change circuit so that a higher hydraulic pressure of the pressure change circuit results in a smaller area of the flow passage from the first oil chamber toward the pressure change circuit. 
     
     
         19 . The belt type continuously variable transmission according to  claim 11 , wherein
 the second pulley includes a second oil chamber that contains oil;   the pressure change circuit opens to a sliding portion of the engine or a sliding portion of the belt type continuously variable transmission;   the switching valve is an electromagnetic four-way valve including first, second, third and fourth ports;   the hydraulic circuit further includes:
 an oil pump that operates in accordance with the rotational speed of the engine; 
 a first circuit through which a discharge-side portion of the oil pump and the second oil chamber communicate with each other; 
 a second circuit through which the first circuit and the first port of the four-way valve communicate with each other, the second circuit including with the control valve; 
 a third circuit through which the second port of the four-way valve and the first oil chamber communicate with each other, the third circuit including an orifice; 
 a fourth circuit through which the first circuit and the pressure change circuit communicate with each other, the fourth circuit including another control valve that controls a hydraulic pressure of the second oil chamber; 
 a fifth circuit through which a portion of the third circuit, located closer to the first oil chamber than the orifice, and the third port of the four-way valve communicate with each other; and 
 a sixth circuit through which the fourth port of the four-way valve and the pressure change circuit communicate with each other, the sixth circuit including an orifice; and 
   the four-way valve is arranged so that the first port and the third port communicate with each other and the second port and the fourth port do not communicate with each other when the four-way valve is energized, and so that the first port and the second port communicate with each other and the third port and the fourth port communicate with each other when the four-way valve is not energized.   
     
     
         20 . A vehicle comprising the belt type continuously variable transmission according to  claim 11 .