JP2732265B2 - Transmission control device for continuously variable transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a shift control device in a hydraulic control system of a belt-type continuously variable transmission for a vehicle, and more particularly, to a belt slip caused by a tire lock and a subsequent brake release when braking on a low friction road (low μ road). Regarding preventive measures.

[Prior art]

2. Description of the Related Art Conventionally, in such a type of continuously variable transmission, for example, as disclosed in Japanese Patent Application Laid-Open No. 54-157930, a hydraulic control system has a speed ratio control valve. A spring force according to the accelerator opening is applied to one of the gear ratio control valves, and a pitot pressure according to the engine speed is applied to the other, and the primary pressure of the primary pulley is changed so that both are balanced. It is a configuration for controlling. In this case, a sensor for detecting the pitot pressure is provided on the primary pulley on the engine side. In addition, as a drive system including a continuously variable transmission, the applicant has already configured the engine to transmit power to the primary pulley via an electromagnetic clutch and a forward / reverse switching device, while connecting the primary pulley with a secondary pulley by a belt. There has been proposed a configuration in which a pulley side is configured to transmit power to a wheel side, and an electromagnetic clutch is automatically connected and disconnected according to engine speed and vehicle speed to prevent engine stall and the like. With such a drive system, when the clutch is connected, the primary pulley is directly connected to the engine to generate a pitot pressure, so that the shift control can be performed normally.

[Problems to be solved by the invention]

As described above, the pitot pressure is an important factor in the shift control, and there is no problem when the pitot pressure is output normally in normal traveling, but depending on the traveling conditions, the generation of the pitot pressure may be disturbed and cause inconvenience. . As one of them, there is a driving condition in which the tire is locked due to insufficient gripping force at the time of sudden braking on a low μ road such as a snowy road, and the behavior in this case will be described with reference to FIG. First, when the tire is locked, the vehicle speed Vm gradually decreases, whereas the wheel speed Vw sharply decreases to zero, and accordingly, the pitot pressure Pt and the primary pressure Pp also rapidly decrease.
On the other hand, the actual pulley and belt are separated from the engine side by the clutch disengagement, and the belt is stopped and held at the high speed stage in which the belt has shifted to the primary pulley side, and the line pressure PL is also low based on the speed ratio i. Thus, while the gear ratio control valve of the hydraulic control system is shifted to the lower gear stage due to the lowering of the pitot pressure, the actual pulley and belt are at a low line pressure and are in a stopped state, so that the gear cannot be shifted to the lower gear stage. Or it is a state in which a slow shift is in progress. Therefore, when the brake is released, the tire lock is released and the wheel rotates, and when the wheel speed Vw recovers rapidly, the pulley and belt are also rotated by the wheel. At this time, the inertia mass after the driven side of the clutch is added to the primary pulley side, and the large inertia mass including the primary pulley is rapidly turned by the secondary pulley via the belt. Also, when the tire is locked, the primary pulley is in a stopped state, the primary pressure is very low, and when the brake is released from this state, the primary pressure is low, so that the gear quickly shifts to the lower gear and downshifts. The supply of the line pressure cannot catch up, the line pressure drops momentarily, and the rise of the primary pressure is delayed, so that the belt pulling force of the primary pulley becomes insufficient. Thus, such an abrupt behavior causes the primary pulley to not be able to immediately follow the belt, causing the belt to slip with respect to the pulley, thereby impairing the durability of the belt. In addition, the rotation of the primary pulley is delayed, and the rise of the pitot pressure is also delayed. For this reason, it is necessary to take measures to prevent belt slip at the time of tire locking, and various methods can be considered to implement such measures. Here, since the continuously variable transmission includes the valve block of the hydraulic control system, it is desired that the determination of the tire lock and the prevention thereof are performed mechanically using the hydraulic pressure. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to mechanically perform determination of tire lock during braking on a low μ road and measures to prevent belt slip by using a hydraulic control system. It is another object of the present invention to provide a shift control device for a continuously variable transmission that is capable of performing the following.

[Means for Solving the Problems]

To achieve the above object, a shift control device according to the present invention includes:
A shift lock valve is provided so as to cover the outside of a check valve of a drain oil passage of the above-mentioned speed ratio control valve in a system having a speed ratio control valve in a hydraulic control system of a continuously variable transmission and supplying and discharging oil to and from a primary cylinder. , The shift lock valve is a cylinder,
A spool fitted in the cylinder to open and close the drain port, and a port shaft operably inserted into the cylinder so that the spool is operable, and the port shaft is used when the tire is locked during braking on a low friction road. A shift lock mechanism for moving is provided.

[Action]

Based on the above configuration, when the tire is locked during braking on a low friction road, the shift lock mechanism moves the spool of the shift lock valve through the port shaft to close the drain port, and the transmission ratio control valve causes the primary cylinder to close. Even if drained, the primary pressure is maintained at a high level. At this time, when the port shaft is closed, a high primary pressure acts behind the shift lock valve, and the port shaft is self-locked to the above-described closed position. Thus, when the pulley and the belt are suddenly fixed when the brake is released, the primary pulley and the belt are rotated by the pressing force due to the high primary pressure without causing the belt slip. Then, by opening the port shaft by the shift lock mechanism after the brake is released, the self-lock of the check valve inside the shift lock valve is released, and the drainage of the primary pressure is resumed.
As a result, the vehicle is gradually downshifted from the high-speed gear and returned.

【Example】

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 illustrates a belt-type continuously variable transmission in which a front engine / front drive (FF) -based transverse transaxle-type electromagnetic powder clutch is combined. 1 is an electromagnetic powder type clutch, 2 is a forward / reverse switching device, 3
Denotes a continuously variable transmission, and 4 denotes a front differential device. The electromagnetic powder type clutch 1 is housed in one of the clutch housings 6, and the other of the clutch housing 6 and a main case 7 joined thereto, and a side case joined to the main case 7 on the side opposite to the clutch housing 6. 8, a forward / reverse switching device 2, a continuously variable transmission 3, a front differential device 4
Is accommodated. The electromagnetic powder type clutch 1 includes a ring-shaped drive member 12 integrally connected to a crankshaft 10 of an engine via a drive plate 11, and a disk-shaped driven member 14 integrally spline-connected to a transmission input shaft 13 in a rotational direction. Having. A coil 15 is built in the outer peripheral portion of the driven member 14, and a gap 16 is formed along the circumference of both members 12, 14, and the gap 16 has electromagnetic powder. Also coil
The power supply brush 19 slides on the slip ring 18 at the hub of the driven member 14 having the
To the coil 15 through the interior of the driven member 14 to form a clutch current circuit. In this way, when a clutch current is applied to the coil 15, magnetic powder is generated between the drive and the driven members 12 and 14 via the gap 16, and the electromagnetic powder is coupled in a chain to the gap 16 and accumulated. With drive member
The driven member 14 slides against 12 and joins together,
The clutch is connected. On the other hand, when the clutch current is cut, the drive and driven member 1
The coupling force of 2,14 is lost, and the clutch is disconnected. The control of the clutch current in this case is performed by the forward / reverse switching device 2.
P (parking)
Alternatively, when switching from the N (neutral) range to the forward D (drive), Ds (sporty drive) or reverse R (reverse) range, the clutch 1 is automatically disconnected and the clutch pedal operation becomes unnecessary. Next, the forward / reverse switching device 2 is provided between the input shaft 13 from the clutch 1 and the primary shaft 20 arranged coaxially with the input shaft 13. That is, a reverse drive gear 21 also serving as the forward engaged side is formed on the input shaft 13, and the primary shaft 20
The reversely engaged gear 22 is rotatably fitted to the gears 21 and 22, and these gears 21 and 22 are connected via a counter gear 24 supported by a shaft 23 and an idler gear 26 supported by a shaft 25. Meshing is configured. And the primary shaft 20 and gears 21 and 22
, A switching mechanism 27 is provided. Here, the gears 21, 24, 26, 22 which are always meshed with each other are
In response to the fact that the inertia mass of this portion when the clutch is disconnected is relatively large, the switching mechanism 27 has a sleeve 29 that is spline-fitted to the hub 28 of the primary shaft 20. The gears 21 and 22 are configured to mesh with each other via mechanisms 30 and 31. Thus, at the neutral position of the P or N range, the sleeve 29 of the switching mechanism 27 is fitted only with the hub 28, and the primary shaft 20 is separated from the input shaft 13. Then the sleeve 29,
When the gear 21 meshes with the gear 21 via the synchronization mechanism 30, the input shaft
The primary shaft 20 is directly connected to the motor 13 so as to move forward in the D or Ds range. On the other hand, when the sleeve 29 is engaged with the gear 22 via the synchronization mechanism 31, the input shaft 13
It is connected to the primary shaft 20 via 21, 24, 26, and 22, and the engine power is reversed to enter the reverse range of the R range. In the continuously variable transmission 3, a secondary shaft 35 is disposed in parallel with the primary shaft 20, and a primary pulley 36 and a secondary pulley 37 are provided on both of the shafts 20 and 35, respectively.
An endless drive belt 34 extends between the pulleys 36 and 37. The primary pulley 36 and the secondary pulley 37 are both divided into two parts, and one of the fixed pulleys 36
a, 37a, the other movable pulley 36b, 37b is made movable to make the pulley interval variable, and the movable pulleys 36b, 37b are provided with hydraulic servo devices 38, 39 which also serve as pistons themselves, Further, a spring 40 is biased on the movable pulley 37b of the secondary pulley 37 in a direction to reduce the pulley interval. As a hydraulic control system, an oil pump 41 as an operation source is installed next to the primary pulley 36. The oil pump 41 is a high-pressure gear pump, and has a pump driving source 42
But the primary pulley 36, primary shaft 20 and input shaft 1
3, and is directly connected to the crankshaft 10, so that oil pressure is constantly generated during engine operation. By controlling the oil pressure of the oil pump 41, each hydraulic servo device 3 is controlled.
8, 39, and the pulley interval between the primary pulley 36 and the secondary pulley 37 is changed to the opposite
The pulley ratio of the pulleys 36 and 37 is continuously changed, and the power having the continuously variable speed is output to the secondary shaft 35. In view of the fact that the high-speed-stage-side minimum pulley ratio of the continuously variable transmission 3 is very small, for example, 0.5, and thus the rotational speed of the secondary shaft 35 is large, the front differential device 4 Output shaft 4 via intermediate reduction gears 43a and 43b
4 is linked. And the drive gear 45 of this output shaft 44
The final gear 46 meshes with the gears, and is transmitted from the final gear 46 to the left and right axles 48a and 49b via the differential mechanism 47. Referring to FIG. 2, the hydraulic control system of the continuously variable transmission 3 will be described. In the primary hydraulic servo device 38, a movable pulley 36b is fitted to a cylinder 38a integral with the primary shaft 20 to supply and discharge the cylinder 38a. A primary pressure is created by oiling. Also in the secondary hydraulic servo device 39, the movable pulley 37b is fitted to a cylinder 39a integral with the secondary shaft 35, and a line pressure is introduced into the cylinder 39a. Here, the movable pulley 36b has a larger pressure receiving area than the movable pulley 37b, and enables the speed change control using only the primary pressure. The oil pumped from the oil reservoir 70 by the oil pump 41 is guided to the line pressure regulating valve 90 via the oil passage 71a, and the oil passage 71b of the line pressure branched from the oil passage 71a is always connected to the secondary cylinder 39a. Communicate to introduce pressure. The oil passage 71c branched from the oil passage 71a communicates with the speed ratio control valve 100, and the speed ratio control valve 100 and the primary cylinder 38a
And an oil passage 72 communicates with the oil passage. Also the primary cylinder 38
At a position a, a pitot pressure sensor 73 for taking out a pitot pressure as a control pressure according to the engine speed in the shift control after the clutch is engaged is provided, and the pitot pressure from the pitot pressure sensor 73 is supplied to an oil passage. It is guided to a line pressure adjusting valve 90 and a speed ratio control valve 100 via 74. Further, in contrast to the D range in which shift control is performed in a wide range including a state in which the engine speed is low, the shift control is performed only in a high engine speed range to obtain a Ds range in which engine braking works when the accelerator is released. As a system, a relief valve 76 is provided in the drain oil 75a from the line pressure adjusting valve 90, and an oil passage 75b of a lubricating hydraulic circuit branched from the upstream side of the relief valve 76 communicates with the select position detection valve 130,
An oil passage 75c further branched from the oil passage 75b is provided with a shift control valve 100.
Of the engine brake 140. An oil passage 75d for scooping from the oil passage 75a of the lubricating hydraulic circuit is connected to a belt lubricating oil nozzle 77 disposed on the inner circumference of the belt 34,
The oil passage 75e is connected to the oil nozzle 77 of the pitot pressure sensor 73 by the oil passage 7
5e communicates with the oil supply port 78 of the pitot pressure sensor 73,
75e communicates with the oil sump 70 via a check valve 79 and an oil cooler 80. A balancer chamber 39c is provided on the side of the secondary cylinder 39a opposite to the hydraulic chamber 39b, and an outlet-side oil passage 81 of the oil cooler 80 communicates with the balancer chamber 39c to fill the oil,
The centrifugal oil pressure in the hydraulic chamber 39b is offset by the balancer chamber 39c. A shift lock valve 84 provided with a check valve 83 is provided in the middle of the drain oil passage 82 of the speed ratio control valve 100, and a pre-feeling is provided between the oil passages 82 and 75b upstream of the check valve 83. The oil passage 85 communicates. An orifice 86 is provided in the middle of each oil passage at the air opening. The line pressure adjusting valve 90 includes a valve body 91, a spool 92, and a spool.
Spring 94 biased between one bush 93 of 92
A sensor shoe 95 that engages with the primary movable pulley 36b and detects the actual gear ratio is movably supported by a shaft tube 96 also serving as a lubrication passage, and is connected to the bush 93. In the valve body 91, the pitot pressure of the oil passage 74 acts on the port 91a of the spool 92 on the side opposite to the spring 94, and this port 9
1a through drain port 91b, oil passage to adjacent port 91c
71a line pressure acts. The port 91c has a port 91d through which line pressure is guided and a drain port 91e, and the land chamfer portion 92a of the spool 92 changes the drain amount to regulate the pressure.
A two-stage line pressure switching port 91f is provided on the spring 94 side adjacent to the spring 91e. On the other hand, a line pressure two-stage switching solenoid valve 97 is provided in the line pressure oil passage 71c. The line pressure two-stage switching solenoid valve 97 is a three-way valve, and selectively connects the oil passage 98 connected to the line pressure two-stage switching port 91f to the oil passage 71c and the drain side. The configuration is such that the oil passages 71c and 98 are connected to each other to guide the line pressure to the line pressure two-stage switching port 91f, and the oil passage 98 is drained by non-energization. Thus, the spring force of the spring 94 of the spool 92 increases as the gear ratio increases, and this spring force acts on the line pressure increasing side. Further, the line pressure at the port 91c and the line pressure two-stage switching port 91f acts on the line pressure lowering side, and the line pressure is controlled by a balance between these two. The pitot pressure at the end of the spool 92 acts to adjust the balance point of the spool 92 when the pump discharge amount changes with the engine speed. Therefore, the spring force F, at the balance point of the spring 94,
Line pressure PL, port 91c and line pressure two-stage switching port 91
Assuming that the pressure receiving area difference of f is AL, Ac, when the line pressure two-stage switching solenoid valve 97 is not energized, AL · PL = F is established, and the line pressure is controlled to be high by PL = F / AL. You. When the solenoid valve 97 is energized, (AL + Ac) · PL = F is established, and the line pressure is controlled to be low by PL = F / (AL + Ac). In this way, the line pressure is steplessly controlled by the spring force that changes according to the gear ratio.
The line pressure level is low due to the stage switching solenoid valve 97,
The pulley pressing force is generated by being controlled in two stages. The speed ratio control valve 100 includes a spool 102 on one side of a valve body 101.
Pitot pressure acts on the port 101a at one end of the spool 102 via the check valve 103 or the orifice 104,
At the other end, a low speed spring 105 and a high speed spring 106 are urged. The center port 101b of the spool 102 communicates with the oil passage 72, and its left and right ports 101c and 101d communicate with the drain oil passage 82 and the line pressure oil passage 71c. The groove 102a of the spool 102 supplies and discharges oil to the primary cylinder 38a. To generate a primary pressure. The other end of the valve body 101 has a plunger 107, and one end of a rod 108 is inserted into the plunger 107 via a spring 109, and a shift cam 110 which rotates on a roller 108a at the other end of the rod 108 according to the accelerator opening. Comes into sliding contact. The guide 111 is attached to the plunger 107 and receives the spring 105. Thus, the force of the spring 105 is changed according to the rotation of the shift cam 110. Where plunger 1
The pitot pressure of oil passage 74 is led to 07, and plunger 10
The spring reaction force acting on the shift cam 111 is received by the pitot pressure to reduce the operation force of the shift cam 111. Further, a mechanical modulator mechanism 120 is provided between the plunger 107 and the spring 106. The modulator mechanism 120 has a variable mechanism 121 between the plunger 107 and the receiver 112 of the spring 106 inside the guide 111, and the variable mechanism 121 is connected to the sensor shoe 95 via a link 122. The variable mechanism 121 acts as a modulator so as to gradually increase the force of the spring 106 as the gear ratio shifts to a high speed stage with a small gear ratio. Thus, the pitot pressure and the shift cam 110 are
The force of the spring 105 acts according to the accelerator opening. Then, a gear ratio is determined by generating a predetermined primary pressure in a balance between the two, and gear ratio control is performed so as to upshift to a higher gear as the pitot pressure increases with an increase in vehicle speed.
At this time, the force of the spring 106 according to the gear ratio is further applied to the spool 102 by the modulator mechanism 120, and the engine speed is sequentially increased in accordance with the upshift to the high speed stage. The select position detection valve 130 is provided with a drain hole 132 in the valve body 131.
Is inserted, and a cam 135 that rotates in response to the operation of the select lever 136 is in contact with the valve body 133.
Here, in the cam 135, the range position of D, N, R is the convex portion 135a.
The P and Ds range positions at both ends are concave portions 135b, and the drain hole 132 is closed in each of the D, N, and R ranges to generate operating hydraulic pressure. Also, when the drain hole 132 is opened in the P, Ds range, the orifice 86 prevents a decrease in the hydraulic pressure of the upstream oil passage 75a. The engine brake actuator 140 is
The piston 142 is inserted into the piston 41, a return spring 143 is urged to one of the pistons 142, and the operating oil pressure of the oil passage 75b is guided to the other piston chamber 144 via the oil passage 75c. The hook 142a at the tip of the piston 142, the roller pin 108b of the rod 108 of the speed ratio control valve 100, and the sensor shoe
Between 95, a lever 146 of the modifying mechanism 145 for Ds range characteristic correction which doubles as a pushing lever is provided so as to be engageable. Thus, when there is no operating oil pressure in the P, Ds range, the lever 146 is swung by the hook 142a of the piston 142 to move the rod
108 is forcibly depressed by a predetermined stroke, and the shift range is limited to the side where the engine speed is high, whereby the engine brake works in the Ds range. When a predetermined gear ratio is reached in this state, the sensor shoe 95 engages with the lever 146, and thereafter, the lever 146 swings in the opposite direction by the sensor shoe 95 in accordance with the increase of the gear ratio, and the piston 142, Rod 1
08 will be returned to the position of the forward dimension. 2 and 3 (a) and (b), measures for preventing a belt slip when the tire is locked will be described. In the drawing, reference numeral 150 denotes a valve block, and second and inner portions of a body 151 and a plate 152 of the valve block 150 are provided.
A line pressure adjusting valve 90, a speed ratio control valve 100, a modulator mechanism 120, a modifying mechanism 145, and the like are installed in the figure, and a shift lock mechanism 160 is provided as a measure for preventing a belt slip when a tire is locked. As described above, the shift lock mechanism 160 has a shift lock valve 84 attached to a portion of the check valve 83 of the drain oil passage 82 from the speed ratio control valve 100, and a shift lock valve opposite to the shift cam 110 of the valve block 150. A plunger 161 is installed on the same side as the valve 84. A shift lock arm 165 is mounted between the shift lock valve 84, the plunger 161 and the sensor shoe 95. The check valve 83 has a ball 83c that urges a spring 83b inside a spool 84b of the shift lock valve 84 to regulate the amount of drain from the drain oil passage 82. In the case of the above, oil is filled therein to perform a prefilling operation. The spool 84b of the shift lock valve 84 is movably inserted into the cylinder 84a of the shift lock valve 84 so as to open and close the drain port 83d. Further, the port shaft 84g is provided so as to contact the spring receiver 84f integral with the spool 84b of the shift lock valve 84 from the cylinder 84a. Here, the spring receiver 84f is provided with a communication hole 84h that communicates the inside of the spool 84b with the side where the port shaft 84g contacts,
Further, since oil flows into the inside of the spool 84b of the shift lock valve 84, the ports 84d,
84e is the cylinder 84a and the spool 84 of the shift lock valve body 84.
b, these ports 84d and 84e have check valves
In the cylinder 84a formed so as to face the ball 83e of the 83, they match at the open position of the drain port 84c, but do not match at the closed position of the drain port 84c. In the closed position of the drain port 84c, the shift lock valve 84 is configured to self-lock by applying a high primary pressure behind the spool 84b, and to release the self-lock by draining from the port shaft 84g. The plunger 161 is inserted into a cylinder 162 communicating with the pitot pressure oil passage 74, moves according to the pitot pressure, and detects its size. At a relatively large normal pitot pressure at the high speed stage, the tip 161a of the plunger 161 is moved to the body 151.
Protruding higher. The shift lock arm 165 has a substantially rectangular shape when viewed from the back, and has a shift lock valve 84, an engagement piece 165b with the plunger 161 on one of the parallel connecting portions 165a, and a spring receiver 165c and the sensor shoe 95 on the other side. Has an engagement piece 165d. Then, the connecting portion 165a is swingably attached using, for example, the shaft 123 of the modulator mechanism 120, and the spring 166 is biased by the spring receiver 165c. The engagement piece 165d extends directly below the sensor shoe 95 and has a predetermined gear ratio is (for example, 1.
0) At lower speeds, the pin 95a on the sensor shoe 95 side has a straight section
165e engages to limit swing of arm 165. On the higher gear side than the gear ratio is, the restriction by the sensor shoe 95 is released, and if the pitot pressure drops abnormally under this condition, it is determined that the tire is locked when braking on a low μ road, and the arm 16 is locked.
5 is to work. Further, the tip of the engagement piece 165d is provided with a pin 95a and an arm 165 due to the movement of the sensor shoe 95.
A taper 165f is provided so as to be able to return to the engagement with. The arm 165 is normally set to be tilted by the action of the plunger 161 or the sensor shoe 95, and to be horizontal by the spring 166 when the tire is locked. And arm 16
When the adjusting screw 167 is tilted together with 5, the spool 84b of the shift lock valve 84 moves together with the spring receiver 84f by the urging force of the spring 83b of the check valve 83, and the drain port 84c opens,
The spring receiver 84f contacts the port shaft 84g. On the other hand, when the arm 165 is horizontal, the port shaft is
84g and the spring receiver 84f are pushed in, the spool 84b moves and the drain port 84c closes, and in this state, the oil inside the spool 84b flows into the port shaft 84g through the communication hole 84h formed in the spring receiver 84f. When the pressure of the oil increases, the contact portion between the spring receiver 84f and the port shaft 84g opens against the spring 83b, and the oil is drained through the inside of the port shaft 84g. Next, the operation of the thus-configured continuously variable transmission control system will be described. First, before the shift is started when the vehicle stops or starts running, the line pressure regulated by the line pressure regulating valve 90 is introduced only to the secondary cylinder 39a through the oil passage 71b, and the primary cylinder 38a is connected to the speed ratio control valve 100. To communicate with the drain oil passage 82. Therefore, in the continuously variable transmission 3, the drive belt
The largest winding diameter of the secondary pulley 37 to the primary pulley 36 of 34, a low speed stage of maximum speed ratio i _L. Next, after traveling, the pitot pressure of the pitot pressure sensor 73 rises and moves the spool 102 of the speed ratio control valve 100, and the oil passage 71c
Is supplied to the primary cylinder 38a via the oil passage 72, the primary pressure is immediately generated by the prefilling operation, and the upshift is started. And by increasing the primary pressure, winding diameter increases relative to the primary pulley 36 of the drive belt 34 is continuously variable speed stage of the minimum speed ratio i _H eventually. Therefore, at the low speed stage in the shift control, the engagement piece 165d of the shift lock arm 165 in the shift lock mechanism 160 is connected to the pin 9 of the sensor shoe 95 as shown in FIG.
The swing is restricted by engaging with 5a, so that when the pitot pressure is zero when the vehicle is stopped, or when the pitot pressure is small at low speed traveling, the arm 165 is tilted and held. Therefore, the port shaft 84g of the shift lock valve 84 protrudes outward, and the tip spool 84b moves backward so as to open the drain port 84c so that the drain can be drained. Therefore, the gear ratio control valve 100
When the primary cylinder 38a is communicated with the drain oil passage 82 by b and 101c, the primary cylinder 38a is freely drained from the drain port 84c of the shift lock valve 84 via the check valve 83 to reach the maximum speed ratio, and the primary cylinder 38 Upshifting from the maximum gear ratio occurs as the primary pressure is increased by refueling 38a. Thus, the shift control at the low speed stage
It is ensured that it is always performed normally. When the pitot pressure according to the engine speed increases with the vehicle speed, the plunger 161 is strongly pushed out by the pitot pressure to keep the arm 165 in the above-mentioned inclined state. Therefore, the oil in the drain oil passage 82 remains in the check valve even after the pin 95a of the sensor shoe 95 is disengaged from the arm 165 by moving to the left side in FIG. The drain can be drained from the drain port 84c through the 83, so that a gear change such as kick down can be freely performed. When a downshift is performed during deceleration, the sensor shoe 95 moves to the right in FIG. 3B, and the pin 95a engages with the arm 165 again to return to the above-described state. Here, tire lock during braking on a low μ road may occur even at low speeds at low speeds, but in this case, the change in the gear ratio is small, and the input rotation speed from the wheel side when the brake is released is also low. Therefore, belt slip or the like when the brake is released does not cause much problem. For this reason, even if the pitot pressure is reduced due to the tire lock at the above-mentioned low speed, the pitot pressure is ignored. On the other hand, in a high-speed gear such as a minimum gear ratio, the arm 165 is disengaged from the sensor shoe 95 and can swing, and under this condition, a low μ
When the pitot pressure suddenly decreases along with the wheel speed and a tire lock occurs as shown in FIGS. 5 (a) and 5 (b) during braking on a road, the pushing amount of the plunger 161 is reduced, and the arm 165 is moved by the spring 161. As shown in FIG. 4, it swings in a substantially horizontal state. For this reason, the shift lock valve 84 pushes down the spool 84b via the port shaft 84g to close the donren port 84c, and the contact portion between the port shaft 84g and the spring receiver 84f is also closed by the movement of the adjusting screw 167. Therefore, even if the gear ratio control valve 100 causes the primary cylinder 38a to communicate with the drain oil passage 82 due to a decrease in the pitot pressure, the high primary pressure P'p as shown by the broken line in FIG. Contained upstream. In this way, the primary pulley 36, the secondary pulley 37, and the belt 34 are stopped and held on the high speed side by the tire lock, and the shift is locked, and the hydraulic control system is also in the state of being locked with the high primary pressure P'p. . At this time, in the shift lock valve 84, the port
84d and 84e are misaligned, port shaft 84g and spring receiver
The contact portion of 84f is also closed, and the inside of the cylinder 84a is sealed.
For this reason, a high primary pressure acts behind the spool 84b inside the cylinder 84a, and thus the check valve body 83a is self-locked to the closed position to ensure that the primary pressure is maintained at a high pressure. When described in detail with reference symbols a self-locking action FIG. 4, the first inner diameter of the spool 84b of the shift lock valve 84 which covers the ball 83c of the check valve 83 d _1, the spool 84b outside diameter d _2, the port axis 84g outside The diameter is d ₃ , and the primary pressure in the drain oil passage 82 is Pp
Force applied to the shift lock valve 84 when a is a (downward ^{_{force) = π · d 1 2 ·}} Pp / 4 ( upward ^{_{force) = π · (d 2 2}} -d 3 2) · P / 4 There, where the idea to set a ^{_{π · d 1 2/4 <}} π · (d 2 2 -d 3 2) / 4, ( downward force) <(upward force), and the shift lock valve 84 Will self-lock. When the brake is released, the wheel speed Vw recovers as shown in FIG. 5, and the secondary pulley 37 and the belt 34 are rapidly turned, but a high primary pressure P′p exists in the primary cylinder 38a. In order to apply a sufficient pulley pressing force to the inertial mass on the side of the primary pulley 36, the primary pulley 36 is rotated by the belt 34 without causing slip, and a speed ratio according to the primary pressure P'p is maintained. After that, when the pitot pressure recovers and rises and the tire lock is released, the arm 165 is inclined by pushing the plunger 161 to open the contact portion between the port shaft 84g and the spring receiver 84f, and the pressure inside the shift lock valve 84 is released. Then, the self-lock of the closed position of the drain port 84c of the shift lock valve 84 is released, and the spool 84b of the shift lock valve 84 is retracted by the spring 83b to open the drain port 84c again. 'P also drains
The downshift starts slowly and returns as indicated by the broken line in FIG. Also, when the drain port 84c of the shift lock valve 84 is closed with the tire closed, the ports 84d and 84e may be provided with a slight opening or the fifth primary pressure P'p may be leaked from the seal portion using a high primary pressure P'p. When the temperature is gradually lowered as shown by the dashed line in FIG. 5C, the downshift starts as shown by the dashed line in FIG. 5D. At this time, the sensor shoe 95 moves and engages with the arm 165 via the taper 165f to return to the original position. Thus, even when stopping in the tire locked state, the gear ratio returns to the maximum gear ratio. The shift lock mechanism is not limited to the above embodiment.

【The invention's effect】

As described above, according to the present invention, in the speed change control of the continuously variable transmission, the tire lock during braking on the low friction road is determined, and the hydraulic pressure control system is shift-locked to maintain the primary pressure high. Thus, belt slip at the time of brake release can be reliably prevented. Further, since the shift lock valve is installed integrally with the check valve in the drain oil passage of the speed ratio control valve, the space and structure are simplified. Furthermore, since the shift lock valve is configured to self-lock the spool to the closed position with a high primary pressure when the tire is locked, it is possible to reliably maintain the primary pressure at a high pressure. In addition, since the port shaft of the shift lock valve doubles as a mechanical operating shaft and a hydraulic port, and the check valve operates mechanically and hydraulically, self-locking and release thereof can be performed quickly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a continuously variable transmission to which the present invention is applied, FIG. 2 is a hydraulic circuit diagram showing an embodiment of a shift control device of the present invention, and FIG. FIG. 3 (a) is a cross-sectional view showing the operation state of the shift lock mechanism when the tire is locked, and FIGS. It is a characteristic view of each part at the time of a tire lock. 3 ... continuously variable transmission, 38a ... primary cylinder, 82 ...
… Drain oil passage, 83 …… Check valve, 84a …… Valve body, 83d
…… Drain port, 84 …… Shift lock valve, 84a …… Valve body, 84b …… Port shaft, 100 …… Gear ratio control valve, 160
… Shift lock mechanism

Claims (1)

(57) [Claims] An oil pressure control system for a continuously variable transmission having a speed ratio control valve for supplying and discharging oil to and from a primary cylinder, wherein the outside of a check valve of a drain oil passage of the speed ratio control valve is covered. A shift lock valve, wherein the shift lock valve includes a cylinder, a spool fitted into the cylinder to open and close a drain port, and a port shaft through which the spool is operably inserted. A shift control device for a continuously variable transmission, comprising: a shift lock mechanism for moving the port shaft when a tire is locked during braking.