JPH02102960A - Line pressure control device of continuously variable transmission - Google Patents

Abstract

PURPOSE:To prevent a belt from slipping by changing over the line pressure into high with a solenoid valve at the time of abrupt braking involving tire lock, and keeping the line pressure high for a certain while after disengagement of the brake. CONSTITUTION:A brake signal is given from a brake switch 156 to an abrupt brake sensor part 165, and at the same time, deceleration is calculated on the basis of a signal from a car speed sensor 153 to result in a judgement about abrupt braking if the wheel speed sinks unproportionally for corresponding car body speed. An operating mode judging part 162 puts off a solenoid valve 97 by a high pressure setting part 168 and controls the line pressure high by a line pressure adjusting valve even in the event of quick braking, and thus the belt is prevented from slippage. If thereafter the brake is disengaged at the time of tire lock, the wheel speed will quickly become identical to the corresponding car body speed, and tire lock be disengaged. At this time, the line pressure is held high for a period of time specified by a timer 170 from the point of time when a brake disengage signal from the brake switch 156 is fed into a high pressure holding part 169. This prevents belt slip certainly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a line pressure control device in a hydraulic control system of a belt-type continuously variable transmission for a vehicle, and more specifically, the present invention relates to a line pressure control device in a hydraulic control system of a belt-type continuously variable transmission for a vehicle. This article relates to line pressure control as a slip prevention measure.

[Conventional technology]

Generally, this type of continuously variable transmission uses a hydraulic control system to generate line pressure using a line pressure regulating valve, and applies this line pressure to the secondary pulley side to always perform a boolean pressing action that prevents belt slip. .

In addition, the line pressure in this case is used to generate primary pressure on the primary pulley side by the gear ratio control valve to shift the belt, thereby performing stepless speed change control. Therefore, it is necessary to adjust the line pressure depending on the power transmitted from the engine, the speed change state, etc., so as to always apply an appropriate pulley pressing force.

On the other hand, when the vehicle actually runs, the rotation of the drive system is limited by brake operation, or the engine brake is applied by driving the wheels by rapidly downshifting by shifting to the sport drive (Ds) range. In this case, if the line pressure is lowered as the engine output decreases, there is a risk that belt slip may occur due to insufficient force for pressing the brake against the gear shifting and wheel drive force after the brake is released. It is also necessary to perform optimal control individually for each condition.

Here, we will discuss the case of sudden braking accompanied by tire lock on a low friction road (low μ road). If the tires lock during such sudden braking, the rotation of the drive system from the continuously variable transmission to the wheels is locked, and the belt and pulleys are also stopped and held midway through gear shifting.

At this time, in the hydraulic control system of the continuously variable transmission, the pitot pressure becomes zero and the primary cylinder is drained, and then when the brake is released, the drive system rapidly accelerates and recovers by driving the wheels. When this brake is released, the belt and pulley are also turned rapidly, but the large inertial mass of the drive system after the clutch drive acts on the brake lever side in particular, which may cause belt slip. During braking, it is necessary to control the line pressure to high pressure.

By the way, when the high-pressure control of the line pressure during sudden braking is released by a signal from a brake switch or the like when the brake is released, the belt and pulley rotate while rapidly changing speed, prompting an increase in the primary pressure. For this reason, if the line pressure is low and the increase in primary pressure cannot follow the shifting state of the belt and boob, belt slip may still occur.For this reason, it is recommended to take measures to prevent belt slip even after the brake is released. desired.

Conventionally, regarding the above-mentioned control during sudden braking, there is a prior art, for example, disclosed in Japanese Patent Application Laid-Open No. 61-290269. Here, an auxiliary transmission is provided on the output side of the continuously variable transmission to connect/disconnect the power.
It is based on a drive system that changes speed and reverses, and it is shown that when sudden braking occurs, the continuously variable transmission is separated from the wheel side by an auxiliary transmission and downshifts.

[Problem to be solved by the invention]

By the way, the above-mentioned prior art is limited to those in which the switching section of the auxiliary transmission is provided on the output side of the continuously variable transmission, and cannot be applied to a drive system arranged on the input side of the continuously variable transmission. In addition, when braking suddenly, the continuously variable transmission is separated from the wheel side and shifts to the maximum speed all at once, so if it is reconnected to transmit power when the brake is released, engine braking will be applied suddenly and the driving feeling will be affected. This is undesirable because it causes a large impact force to act on the belt and the like.

The present invention has been made in view of the above, and the object thereof is to provide a system that can prevent belt slip by controlling the line pressure during sudden braking accompanied by tire lock even after the brake is released. An object of the present invention is to provide a line pressure control device for a step-change transmission.

[Means to solve the problem]

In order to achieve the above object, the line pressure control device of the present invention includes a line pressure regulating valve in a hydraulic control system of a continuously variable transmission, and increases line pressure by a signal from a control unit.

In a device having a solenoid valve that switches the pressure to low, the control unit is configured to switch the line pressure to high pressure by the solenoid valve during sudden braking that causes tires to lock, and maintain the line pressure at high pressure for a predetermined period of time even after the brake is released. be.

[For production]

Based on the above configuration, when a drive system including a continuously variable transmission brakes suddenly with tire lock, high line pressure control prevents the belt from slipping and moving arbitrarily, and even after the brake is released, the line pressure remains high. By being held at this position, belt slip is also prevented when the continuously variable transmission and its primary side suddenly return to rotation.

〔Example〕

Embodiments of the present invention will be specifically described below based on the drawings.

Referring to FIG. 1, a belt-type continuously variable transmission based on a front engine/front drive (FF) with a transverse transaxle and an electromagnetic powder clutch will be described.

Reference numeral 1 is an electromagnetic powder clutch, 2 is a forward/reverse switching device, 3 is a continuously variable transmission, and 4 is a front differential device. The electromagnetic powder clutch 1 is housed in one side of the clutch housing 6, and the other side of the clutch housing 6 includes a main case 7 joined thereto, and a side case joined to the opposite side of the main case 7 from the clutch housing 6. 8 has a forward/reverse switching device 2. Continuously variable transmission 3. A front differential device 4 is housed therein.

The electromagnetic powder clutch 1 includes a ring-shaped drive member 12. which is integrally connected to the crankshaft lO of the engine via a drive plate 11. A disk-shaped driven member 1 that is integrally spline-coupled to the transmission manual shaft 13 in the rotational direction.
It has 4. A coil 15 is built into the outer peripheral side of the driven member 14, and a gap 16 is formed along the circumference between both members 12, 14, and the electromagnetic powder is contained in this gap 16. In addition, a power supply brush 19 is in sliding contact with a slip ring 18 of the hub portion of the driven member 14 that includes a coil 15, and is further connected to the coil 15 through the inside of the driven member 14 from the slip ring 18 to form a clutch current circuit. ing.

In this way, when the clutch current is passed through the coil 15, the drive and driven men/<12.
14, electromagnetic powder is combined and accumulated in the gap 16 in a chain shape, and the resulting binding force causes the driven member [4] to slide and connect integrally to the drive member 12, and the clutch is connected. Become. On the other hand, when the clutch current is cut, the drive due to the electromagnetic powder and the coupling force between the driven member 12'4 disappear, resulting in a clutch disengaged state.

If the clutch current in this case is controlled in conjunction with the operation of the forward/reverse switching device 2, it is possible to switch from the P (parking) or neutral to N range to the forward D (drive) or Ds (sporty drive) range. or R of retreat (
Clutch 1 is automatically connected and disconnected when switching to the reverse (reverse) range, eliminating the need for clutch pedal operation.

Next, the forward/reverse switching device 2 includes a human power shaft 13 from the clutch 1 and a primary shaft 20 disposed coaxially therewith.
established between. That is, a reverse drive gear 21 that also serves as a forward engagement side is formed on the human power shaft 13, and a gear 22 on a reverse river wave engagement side is rotatably fitted to the primary shaft 20. , 22 are a counter gear 24 . supported by a shaft 23 . The meshes 1, 1 . i will be done. A switching mechanism 27 is provided between the primary shaft 20 and the gears 21 and 22. The gears 21, 24, 26, 22, which are always in mesh here, are connected to the driven member 14 having the coil 15 of the clutch 1, and this corresponds to the fact that the inertia mass of this part is relatively large when the clutch is disengaged. In the switching mechanism 27, the sleeve 29 spline-fitted to the hub 28 of the primary shaft 20 is connected to the synchronizing mechanism 30.31.
It is configured to be meshed and connected to each gear 21 and 22 through.

As a result, in 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 L3. Next, when the sleeve 29 is meshed with the gear 21 side via the synchronizing mechanism 30, the primary shaft 20 is directly connected to the human power shaft 13, resulting in a forward movement state in the D or Ds range.

On the other hand, when the sleeve 29 is meshed with the gear 22 side via the synchronizing mechanism 31, the input shaft 13 is connected to the gear 21°2.
4, connected to the primary shaft 20 via 26.22,
The engine power is reversed and the R range is in reverse mode.

In the continuously variable transmission 3, a secondary shaft 35 is arranged parallel to the primary shaft 20, and primary pulleys 36. A secondary pulley 37 is provided, and an endless drive belt 34 runs between both pulleys 36,37. Primary pulley 3
6. The secondary pulleys 37 are each divided into two parts, and one of the fixed pulleys 38a and 37a is movable to make the other movable pulleys 36b and 37b variable in the interval between the bobbins. , a hydraulic servo device 38, 39 which also serves as a piston is attached to the movable pulley 37b of the secondary pulley 37.
A spring 40 is biased in a direction to narrow the pulley interval.

Further, as a hydraulic control system, an oil pump 41 as an operating source is installed next to the primary pulley 36. This oil pump 41 is a high-pressure gear pump, and a pump drive shaft 42 passes through the primary pulley 3B, the primary shaft 20, and the human power shaft 13, and is directly connected to the crankshaft lO, so that oil pressure is constantly maintained during engine operation. It's starting to happen. Then, the oil pressure of the oil pump 41 is controlled to supply and drain oil to each hydraulic servo device 31i, 39, and the distance between the primary pulley 36 and the secondary pulley 37 is reversed, so that the pulley of the drive belt 34 The pulley ratios in 3B and 37 are converted steplessly, and the steplessly variable power is output to the secondary gate 35.

In view of the fact that the minimum pulley ratio on the high speed side of the continuously variable transmission 3 is very small, for example 0.5, and therefore the rotational speed of the secondary foot 35 is large, the front differential device 4 has a ratio of 1 to 1 for the secondary foot 35. An output shaft 44 is connected via a pair of intermediate reduction gears 43a and 43b. A final gear 4B meshes with the drive gear 45 of this output shaft 44, and transmission is configured from the final gear 46 to the left and right front wheel axles 48a, 48b via a differential mechanism 47.

In FIG. 2, the hydraulic control system of the continuously variable transmission 3 will be explained. In the primary hydraulic servo device 38, a movable pulley 36b is fitted into a cylinder 38a that is integrated with the primary shaft 20, and supply and discharge are supplied and discharged into the cylinder 38a. Primary pressure is generated by oil.

Also, in the secondary hydraulic servo device 89, a movable pulley 37 is attached to a cylinder 39a that is integrated with the secondary support 35.
b is fitted, and line pressure is introduced into the cylinder 39a. Here, the movable pulley 36b has a larger pressure receiving area than the movable pulley 37b, making it possible to perform speed change control using only the primary pressure.

The oil pumped up from the oil reservoir 70 by the oil pump 41 is passed through the oil passage 71a to the line pressure regulating valve 90.
A line pressure oil passage 71 that is guided by the oil passage 71a and branches from the oil passage 71a.
b communicates with the secondary cylinder 39a to always introduce line pressure. An oil passage 71c branching from the oil passage 71a communicates with a gear ratio control valve 100.
An oil passage 72 communicates between the primer cylinder 38a and the primer cylinder 38a. Further, a pitot pressure sensor 73 is installed at the primary cylinder 38a to take out a pitot pressure as a control pressure according to the engine speed during shift control after clutch engagement. is connected to the line pressure regulating valve 90 through the oil passage 74. Gear ratio control valve 10
It leads to 0.

Furthermore, the gears can be changed over a wide range, including at low engine speeds! For the D range, which performs fiq & IIl, a drain oil passage from the line pressure regulating valve 90 is used as a hydraulic system to obtain the Ds range, which performs shift control limited to the high engine speed range and acts as an engine brake when the accelerator is released. 7
5a is provided with a relief valve 7B, and this relief valve 76
An oil passage 75b of the lubrication hydraulic circuit that branches from the upstream side of the lubrication hydraulic circuit communicates with the select position detection valve 1110, and an oil passage 75c that further branches from the oil passage 75b communicates with the engine brake actuator 140 of the gear ratio control valve 100. ing.

Oil passage 75d branching from oil passage 75a of the lubrication hydraulic circuit
is a belt lubricating nozzle 7 arranged on the inner circumference of the belt 34
7, the oil passage 75e communicates with the oil supply lower a of the pitot pressure sensor 78, and the oil passage 75e communicates with the oil supply lower a of the pitot pressure sensor 78. 5c communicates with the oil reservoir 70 via the check valve 7g and the oil cooler 80. A balancer chamber 39 is located on the opposite side of the hydraulic chamber 39b of the secondary cylinder 39a.
c is provided, and the outlet oil passage 81 of the oil cooler 80 communicates with the balancer chamber 39c and fills it with oil.
The centrifugal oil pressure of b is offset by the balancer chamber 39c. Further, a shift lock valve 84 is provided with a check valve 83 in the middle of the drain oil passage 82 of the gear ratio control valve 100.
A brief feeling oil passage 85 communicates between the oil passage 82 upstream of the check valve 83 and the oil passage 75b. It should be noted that an orifice 86 is provided in the middle of each oil passage and at an opening to the atmosphere.

The line pressure regulating valve 90 has a valve body 91. A sensor shoe 95 has a spring 94 biased between the spool 92 and one bush 93 of the spool 92, and engages with the primary movable pulley 36b to detect the actual gear ratio. It is movably supported by a tube 96 and connected to a bushing 93. In the valve body 91, the pitot pressure of the oil passage 74 acts on the boat 91a on the opposite side of the spring 94 of the spool 92, and the drain boat 9
The line pressure of the oil passage 71a acts on the adjacent boat 91c via 1b. In addition, there is a boat 91d and a drain boat 91c adjacent to the boat 91C to which line pressure is introduced, and the land chamfer portion 92a of the spool 92 changes the amount of drain to regulate the pressure. A two-stage line pressure switching boat 91r is provided on the spring 94 side.

On the other hand, a line pressure two-stage switching solenoid valve 97 is provided in the line pressure oil passage 71c. This two-stage line pressure switching solenoid valve 97 is a three-way valve that selectively communicates the oil passage 98 connected to the two-stage line pressure switching boat 911' with the oil passage 71c side and the drain side, and is energized. connects the oil passages 71c and 98 to connect the line pressure two-stage switching port 9.
1", and the oil passage 98 is drained by de-energizing.

In this way, 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. In addition, the line pressure of the boat 91c and the line pressure two-stage switching boat 91'' acts on the line pressure decreasing side, and the line pressure is controlled by the balance between these two.The pitot pressure at the end of the spool 92 is determined by the engine rotational speed. It also acts to adjust the balance point of the spool 92 when the pump discharge amount changes.

Therefore, the spring force F at the balance point of the spring 94 is
, the line pressure PL, the pressure receiving area of the left and right land portions at the port 91c are AL, and the line pressure two-stage switching boat 91.
If the pressure receiving area difference between the left and right land portions is Ae, then
When the line pressure two-stage switching solenoid valve 97 is de-energized, A I, φP1, -F are established, and the line pressure is set to high pressure 1.0 by PL-F/AL.
be controlled.

Also, when the solenoid valve 97 is energized, (AI, +Ac
)φPL-F is established, and the line pressure is PL -F/(AL +Ac)
Controlled by low pressure. In this way, the line pressure is controlled steplessly by a spring force that changes according to the gear ratio, and the line pressure level is controlled in two stages, low and high, by the two-stage line pressure switching solenoid valve 97, resulting in a pulley pressing force. begins to occur.

The gear ratio control valve lOO has a spool 102 on one side of a valve body 101, and a boat 10[a] at one end of the spool 102.
The pitot pressure is checked by check valve 103 or orifice 10.
4, and a low speed spring 105.4 at the other end. High speed spring 106 is biased.

In addition, the boat 10tb in the center of the spool 102 has an oil passage 72.
The left and right boats 101c and 1Qld are drain oil passages 82. The spool 102 communicates with the line pressure oil path 71c.
is supplied to the primary cylinder 38a through the groove portion 102a,
It is designed to drain oil and generate primary pressure.

The other side of the valve body 101 has a plunger 107, and one end of a rod 108 is connected to the plunger 107 with a spring 1.
09, and roller 1 at the other end of the rod 10g.
Shift cam 11 rotates according to the accelerator opening at 08a.
0 comes into sliding contact. A guide 111 is attached to the plunger 107 and receives the spring 05, thus changing the force of the spring 105 in accordance with the rotation of the shift cam 110. Here, the plunger 107 has an oil passage 74.
The pitot pressure is guided, and the spring reaction force acting on the plunger 107 is received by the pitot pressure, and the shift cam 11
It is designed to reduce the operating force of 1.

Furthermore, a mechanical modulator tM120 is provided between the plunger 107 and the spring 106.

This modulator machine +fl120 has a plunger 107
A variable mechanism 121 is provided between the spring receiver 112 inside the guide 111, and this variable mechanism 121 is connected to the link 12.
It is connected to the sensor shoe 95 via 2. And a variable gear as you move to a high speed gear with a small gear ratio? M12
1 acts as a modulator to gradually increase the force of the spring 106.

In this way, the spool 102 has the pitot pressure and the shift cam 1
The force of the spring 105 is applied according to the accelerator opening degree. A predetermined primary pressure is generated by the balance between the two to determine the gear ratio, and the gear ratio is controlled to upshift to a high speed gear as the pitot pressure increases with the increase in vehicle speed. At this time, the force of the spring 10B corresponding to the gear ratio is further applied to the spool 102 by the modulator mechanism 120, so that the engine speed is sequentially increased in accordance with the upshift to the high gear.

In the select position detection valve 130, a valve body 133 having a drain hole 132 is inserted into a valve body 131, and a cam 13 that rotates in accordance with the operation of a select lever 13B is inserted into the valve body 133.
5 is the contact. Here, in the cam 135, D, N
, H range position is the convex portion 135a, and P and D at both ends
The range position of s is in the recess 135b, and as described above,
The drain hole 132 is closed in each of the N and R ranges to generate operating oil pressure. Furthermore, when the drain hole 132 is opened in the P and Ds ranges, the orifice 86 prevents the oil pressure in the upstream oil path 75a from decreasing.

The engine brake actuator 140 has a piston 142 inserted into a cylinder 141.
A return spring [43 is biased to one side of the piston chamber 2, and the operating hydraulic pressure of the oil passage 75b is guided to the other piston chamber 144 via the oil passage 75e. Also, the hook 142a at the tip of the piston 142, the rod 108 of the gear ratio control valve 100,
between the roller pin 108b and the sensor shoe 95,
The Ds range characteristic correction modifying device ti145, which also serves as a push lever, is provided so as to be engageable with the lever t<-t4e.

In this way, when there is no operating oil pressure in the P and Ds ranges, the hook 142a of the piston 142 swings the reno < -146 to forcibly push the rod 108 through a predetermined stroke, thereby limiting the shift range to the high engine speed side. As a result, engine braking is applied in the Ds range. When a predetermined gear ratio is reached in this state, the sensor shoe 95 engages with the lever 14B, and from this point on, the sensor shoe 95 swings the lever 146 in the opposite direction as the gear ratio increases, and the piston I42, The rod 10g is pulled back to the forward dimension position.

In FIG. 3, the electronic control system of the solenoid valve 97 for line pressure control will be described.

First, the signals from the negative pressure sensor 150 and engine speed sensor 151 on the engine side are input to the engine torque calculation section 161 of the control unit 160 to calculate the engine torque from the map, and this engine torque signal is sent to the operation mode determination section [ 62 manpower. Also, ignition switch 1
52. Vehicle speed sensor 153. The vehicle has a starting running detecting section 183 in which the signal from the accelerator switch 54 is manually input, and detects running after starting the engine until a predetermined vehicle speed is reached. It has an inhibitor switch 155 and an accelerator switch [54 signal] which is manually operated by a Ds and R range travel detection section 164,
Detect the running of s and H. Furthermore, the brake switch 15
The vehicle has a sudden brake detection section 165 to which signals from the vehicle speed sensor 153 and the vehicle speed sensor 153 are input, and detects sudden braking that exceeds a predetermined deceleration. These starting running detecting section 163, Ds, R range running detecting section 164. The signal from the sudden brake detection section 165 is also input to the operation mode determination section 162, and the operation mode determination section 1
62 energizes the solenoid valve 97 via the output section 167 during steady running. On the other hand, Ds, H
Under each condition of traveling and sudden braking, the solenoid valve 97 is de-energized.

In addition, in order to ensure prevention of belt slip during sudden braking, a sudden brake detection section 165 and a brake switch 1 are provided.
It has a high pressure holding section 169 into which the signal 5B is input, and is configured to instruct the operation mode determining section 162 to maintain high pressure for a certain period of time set by a timer 70 when the brake is released.

Next, the operation of the continuously variable transmission control system configured as described above will be explained.

First, before the vehicle stops or starts shifting when it 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 gear ratio control valve [ 00 communicates with the drain oil passage 82. Therefore, in the continuously variable transmission 8, the diameter of the winding of the secondary pulley 37 with respect to the primary pulley 3B of the drive belt 34 is the largest, and the maximum gear ratio I
It becomes L low gear.

Next, after driving, the pitot pressure of the pitot pressure sensor 73 increases and moves the spool 102 of the gear ratio control valve 100, and when the line pressure of the oil passage 71c is supplied to the primary cylinder Ha via the oil passage 72, the prefill The action immediately generates primary pressure and starts upshifting. As the primary pressure increases, the diameter of the winding of the drive belt 34 around the primary pulley 36 increases, and finally the speed is continuously variable to a high speed stage with a minimum gear ratio '11.

Therefore, the effect of line pressure in the above-mentioned continuously variable transmission will be described.

First, during steady running in the D range, the control unit lB
The solenoid valve 97 is energized by the operation mode determination unit 162 of the O, and the line pressure of the oil passage 71c is introduced into the switching boat 91r of the line pressure regulating valve 90 via the oil passage 98.

Therefore, the line pressure regulating valve 90 has two ports 91c and 9.
The pressure is regulated based on the relationship between the line pressure 11' and the spring force generated by the sensor shoe 95 according to the gear ratio, and the line pressure level is lowered overall. Here, in the low speed gear where the gear ratio is large, the spring force becomes large and the amount of drain by the chamfer portion 92a of the spool 92 is reduced, so the line pressure increases, and as the gear shifts to the high speed gear, the spring force decreases. The line pressure is gradually reduced, resulting in a characteristic like the curve PLI2 in FIG. 4.

Next, when the load is high above a predetermined engine torque.

When running in the power mode using the Ds range, the solenoid valve 97 is de-energized by the operation mode determination unit 162 of the control unit 160, and the line pressure two-stage switching boat 91 of the line pressure regulating valve 90 is switched to drain. .For this reason, the spool 92 of the line pressure regulating valve 90 will shift to the high line pressure side, and the line pressure level will become high, resulting in a characteristic as shown by curve P1.11 in Fig. 4.Here, the characteristic The ratio of Pμ to Pl and h is constant at all speed ratios.

In this way, during steady running at low to medium loads, a pulley pressing force approximately commensurate with the transmitted torque is generated at a low level line pressure,
Excessive pulley pressing force is avoided.

And when driving in high load, Ds range power mode, etc.
The line pressure at a high pressure level provides a pulley pressing force approximately commensurate with the transmitted torque in this case, and belt slip during such running is reliably prevented. In addition, after the engine starts, the belt 34, primary pulley 3B, secondary pulley 3
When the belt 7 starts to rotate, the relationship between the two is not always normal, but in this case, the normal positional relationship between the belt and the pulley is temporarily ensured with the belt tension at a high level of line pressure.

Note that if the solenoid valve 97 is de-energized due to a failure in the electrical system, the line pressure will be maintained at a high pressure level, thereby providing a failsafe to always prevent belt slip.

Furthermore, the operation at the time of sudden braking will be described using the flowchart in FIG. 5 and the time chart in FIG.

First, when the brake is operated, a brake signal is input from the brake switch 15B to the sudden brake detection section 165, and at the same time, the deceleration is calculated using the wheel speed Vv of the vehicle speed sensor 153, and the vehicle body speed Vm is determined as shown in FIG. 6(b). On the other hand, if the wheel speed Vv suddenly decreases, it is determined that the brake is suddenly applied. When this sudden brake signal is input to the operation mode determining section 182, the high pressure setting section 168 switches the solenoid valve 97 to de-energize and drain the boat 91f of the line pressure regulating valve 90. Therefore, the line pressure regulating valve 90 controls the line pressure PLh to be high even during sudden braking as shown in FIG. 6(C), thereby preventing the belt 34 from arbitrarily moving and slipping during braking.

Thereafter, as shown in FIG. 6(b), when the brake is released when the wheel speed Vw is zero and the tires are locked, the wheel speed ■ν rapidly recovers and becomes equal to the vehicle speed Vm, thereby releasing the tire lock. At this time, a high pressure holding signal is output for a predetermined time by the timer 170 from the time when the brake release signal of the brake switch 15B is manually applied to the high pressure holding part 169, and the line pressure is held at high pressure as shown in FIG. 6(c). .

Therefore, immediately after the brake is released, the belt 34 of the continuously variable transmission 3 and the primary pulley 36
Secondary pulley 37. Further, a forward/reverse switching device 2 integrated with the primary pulley 36. When the driven side of the clutch l is turned rapidly, the load of the inertial mass and the like can be sufficiently received by the pulley pressing force generated by the high line pressure pth of the secondary pulley 37. Therefore, after the brake is released, the portion of the continuously variable transmission 3 including the clutch driven side returns to rotation so as not to cause belt slip.

On the other hand, tire lock during such sudden braking is detected mechanically due to zero pitot pressure at high speed, for example, and ttS
It operates to close the shift lock valve 84 on the drain side of the gear ratio control valve [00] of the hydraulic control system shown in FIG. Then, the primary pressure of the primary cylinder 38a is as shown in FIG. 6(d).
Because the pressure is maintained at high pressure without being drained while the tire is locked, the primary pulley 3 is released when the brake is released.
6 also produces a large boob pressing force, and the belt slip prevention effect increases.

Although one embodiment of the present invention has been described above, it is not limited thereto.

〔Effect of the invention〕

As described above, according to the present invention, in a method of preventing belt slip during sudden braking accompanied by tire lock in a drive system including a continuously variable transmission by controlling the line pressure, the line pressure is maintained at high pressure even after the brake is released. Therefore, it is possible to reliably prevent belt slip when the continuously variable transmission portion suddenly returns to rotation after the brake is released.

Furthermore, since the control system is based on a control system that controls the line pressure to high pressure during sudden braking, and continues high pressure control even after the brake is released, control is also facilitated.

[Brief explanation of the drawing]

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 the line pressure control device of the present invention, and Fig. 3 is an electronic control of a solenoid valve. A block diagram showing the system, FIG. 4 is a diagram of line pressure characteristics, FIG. 5 is a flowchart showing the action during sudden braking, and FIGS. 6(a) to 6d) are the same time charts. 3...Continuously variable transmission, 90...Line pressure regulating valve, 97
... Solenoid valve, 180 ... Control unit, 16
2...Operating mode determination section, 185...Sudden brake detection section, IH...High pressure setting section, 169...High pressure holding section, 170...Timer patent applicant Fuji Heavy Industries Co., Ltd. agent Patent attorney Masaru Ko / N Jundo Patent Attorney Susumu Murai Figure 6

Claims (1)

[Scope of Claims] In a hydraulic control system of a continuously variable transmission having a line pressure regulating valve and a solenoid valve that switches the line pressure between high and low levels according to a signal from the control unit, the control unit is capable of causing sudden braking with tire lock. 1. A line pressure control device for a continuously variable transmission, characterized in that the line pressure is sometimes switched to a high pressure using a solenoid valve, and the line pressure is maintained at a high pressure for a predetermined period of time even after the brake is released.