JP3602276B2 - Hydraulic control circuit for continuously variable transmission - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a continuously variable transmission in which the operating pressure supplied to a planetary gear type forward / reverse changeover device that switches between forward and reverse is forcibly made neutral when a rotation fluctuation exceeding an allowable speed change speed of the continuously variable transmission occurs. The present invention relates to a hydraulic control circuit of a device.
[0002]
[Prior art]
Conventionally, as this type of continuously variable transmission, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-357357, a transmission between a start clutch such as a torque converter, an electromagnetic clutch, a wet multi-plate clutch and a continuously variable transmission is disclosed. A forward brake for connecting / disconnecting a sun gear and a carrier of the forward / backward switching device to the starting clutch side, and a reverse brake for connecting / disconnecting between a ring gear and a transmission case. When the bearing for supporting the pulley shaft of the continuously variable transmission is disposed between the planetary gear and the pulley, the reverse brake is required to reduce the overall length of the transmission. It is necessary to arrange a cylinder around the bearing.
[0003]
The operating pressure required for the engagement between the ring gear and the transmission case to be supplied to the reverse brake requires a large pressure due to the structure of the planetary gear. In the structure arranged on the outer periphery, it is difficult to secure a large cylinder area due to space restrictions, and the operation required pressure is often set relatively large.
[0004]
In addition, the pressure required for clamping the belt of the continuously variable transmission must be set higher than the pressure required for engaging the forward clutch of the forward / reverse switching device. The operating pressure for the brake and the operating pressure for clamping the belt are derived from a common line pressure, and the operating pressure supplied to the forward clutch uses a lubricating pressure that is reduced from the line pressure.
[0005]
Incidentally, there is a case where a large amount of oil is required for the shift control of the continuously variable transmission, and the discharge flow rate of the oil pump is often set based on the maximum required flow rate for the shift control. However, the discharge flow rate of the oil pump when the continuously variable transmission is not performing a shift operation can be reduced because the required lubricating oil amount of the transmission itself at this time is also reduced, and when considering the mechanical efficiency, It is desirable to set the pump capacity as small as possible.
[0006]
However, if this pump capacity is set based on the maximum required shift speed of the continuously variable transmission under normal operating conditions, it is not sufficient to perform shift control of the continuously variable transmission under special running conditions such as sudden braking. It becomes difficult to secure a large amount of oil.
[0007]
That is, in a vehicle in which a start clutch and a forward / reverse switching device are arranged between an engine and a continuously variable transmission, and the continuously variable transmission has a drive system that rotates integrally with drive wheels directly connected to tires, for example, a sudden If the tires are locked due to braking or sudden braking, or forward or reverse is mistakenly switched during running, and a load exceeding the permissible shift speed is transmitted from the drive wheels to the continuously variable transmission, The rotation speed of the input shaft of the stepped transmission becomes lower than the normal rotation speed or stops, and as a result, the engine load becomes excessive, so that not only the transmission body that obtains power from the engine, but also the brake, Functions for operating the vehicle, such as steering, are stopped or significantly reduced.
[0008]
As a countermeasure against this, in the prior art described above, a safety lock valve operated by a solenoid valve is interposed in a hydraulic circuit on the upstream side of a manual valve linked to a select lever, so that a sudden speed exceeding an allowable shift speed for a continuously variable transmission is provided. When the load is transmitted, the safety lock valve is switched by the solenoid valve, and the operating pressure supplied to the forward clutch and the reverse brake is drained from the safety lock valve via the manual valve, and the forward clutch and the reverse brake are released. Thus, a technique is disclosed in which the drive system is forcibly brought into a neutral state and the transmission of load from the drive wheels to the engine is interrupted.
[0009]
[Problems to be solved by the invention]
By the way, the supply of the operating pressure to the forward clutch and the reverse brake of the forward / reverse switching device is interrupted by a manual valve interlocked with the select lever. That is, when the select lever is selected for forward running (D range), the operating pressure is supplied to the forward clutch via the manual valve, the reverse brake is released, and the sun gear and the carrier provided in the forward / reverse switching device are provided. Are engaged by the forward clutch to integrate the planetary gears and transmit rotation in the same direction as the engine output shaft to the continuously variable transmission. On the other hand, when the select lever is selected for reverse running (R range), the operating pressure is supplied to the reverse brake via the manual valve and the forward clutch is released. And transmits the reverse power to the continuously variable transmission.
[0010]
Therefore, the operating pressure supplied to the forward clutch and the reverse brake is constantly applied to the hydraulic pressure supply side of the manual valve. In particular, the hydraulic circuit on the reverse brake side is common to the pulley control pressure of the continuously variable transmission. , A relatively high operating pressure is applied.
[0011]
In the above prior art, since the safety lock valve is interposed upstream of the manual valve, the operating pressure to be supplied to the forward clutch and the reverse brake is constantly applied, so that oil leaks around the safety lock valve are likely to occur. In order to compensate for this oil leak flow rate, it is necessary to increase the control flow rate of the oil pump, which necessitates an oil pump having a large capacity, which increases the engine load, deteriorates fuel efficiency, and Not only does running performance deteriorate, but also the durability of the safety lock valve decreases. In order to sufficiently guarantee the durability of the safety lock valve, the quality must be excessively increased, resulting in an increase in component costs.
[0012]
In view of the above circumstances, the present invention can reduce the oil leak flow rate of the safety lock valve with a simple structure, can sufficiently guarantee the durability without increasing the cost of parts, and can further reduce the pump capacity. It is an object of the present invention to provide a hydraulic control circuit of a continuously variable transmission that can be reduced in size to improve fuel efficiency and traveling performance.
[0013]
[Means for Solving the Problems]
The hydraulic control circuit of the first continuously variable transmission according to the present invention has a planetary gear type forward / reverse switching device interposed in the drive system and communicates with the forward / reverse selection friction engagement element provided in the planetary gear type forward / reverse switching device. The hydraulic circuit is linked to a select lever and a manual valve that switches the operating pressure so that the planetary gear type forward / reverse switching device rotates forward when forward travel is selected, and reverses when the reverse travel is selected. In the connected continuously variable transmission, the hydraulic circuit that connects the manual valve and the forward / reverse selection friction engagement element has a rotational fluctuation exceeding an allowable shift speed of the continuously variable transmission. A safety lock valve for discharging the operating pressure supplied to the forward selection friction engagement element is interposed.
[0014]
The hydraulic control circuit of the second continuously variable transmission according to the present invention is the hydraulic control circuit of the continuously variable transmission according to the first invention, wherein the hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element is provided. The safety lock valve is interposed in a hydraulic circuit between the manual valve and the accumulator.
[0015]
The hydraulic control circuit of the third continuously variable transmission according to the present invention is the hydraulic control circuit of the continuously variable transmission according to the first invention, wherein the hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element is provided. The safety lock valve is interposed in a hydraulic circuit between the accumulator and the forward / reverse selection friction engagement element.
[0016]
In the hydraulic control circuit of the first continuously variable transmission, when a forward lever is selected by operating a select lever, a manual valve interlocking with the select lever is driven by a friction of a planetary gear type forward / reverse switching device interposed in a drive system. By supplying operating pressure to the engagement element and integrally rotating the planetary gear type forward / reverse switching device, the drive system can travel forward. On the other hand, when the reverse travel is selected by operating the select lever, the manual valve switches the operating pressure on the frictional engagement element of the planetary gear type forward / reverse switching device, and reverses the planetary gear type forward / reverse switching device to enable reverse travel. I do. If the select lever is erroneously selected for reverse travel (R range) during forward travel, a rotational fluctuation exceeding the allowable speed of the continuously variable transmission is applied to the continuously variable transmission from the drive wheel side. The operation supplied to the forward / reverse selection friction engagement element via a safety lock valve interposed in a hydraulic circuit communicating between the manual valve and the forward / reverse selection friction engagement element. The pressure is released, and the forward / reverse selection friction engagement element is released.
[0017]
In the hydraulic control circuit for the second continuously variable transmission, in the hydraulic control circuit for the continuously variable transmission according to the first aspect of the present invention, the operating pressure supplied to the forward / reverse selection friction engagement element includes a manual valve and a manual valve. The power is transmitted while being buffered by an accumulator interposed in a hydraulic circuit that communicates with the forward / reverse selection friction engagement element. Then, when a rotation fluctuation exceeding the permissible shift speed of the continuously variable transmission occurs, the operating pressure is discharged from a safety lock valve interposed in a hydraulic circuit between the accumulator and the manual valve.
[0018]
In a third hydraulic control circuit for the continuously variable transmission, in the hydraulic control circuit for the continuously variable transmission according to the first invention, the operating pressure supplied to the forward / reverse selection friction engagement element is a manual valve and a manual valve. The power is transmitted while being buffered by an accumulator interposed in a hydraulic circuit that communicates with the forward / reverse selection friction engagement element. When a rotation fluctuation exceeding the allowable speed change speed of the continuously variable transmission occurs, the safety lock valve interposed in the hydraulic circuit between the accumulator and the forward / reverse selection friction engagement element performs the operation. Relieve pressure.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a first embodiment of the present invention.
[0020]
Reference numeral 1 in FIG. 2 denotes an engine. An output shaft 2 of the engine 1 is connected to a drive shaft 6 that supports a drive wheel 5 via a continuously variable transmission 3 and a final reduction gear 4. The continuously variable transmission 3 includes a torque converter 7 as an example of a starting clutch, a planetary gear type forward / reverse switching device 8 and a continuously variable transmission 9 from the input side.
[0021]
The output shaft 2 of the engine 1 is connected to an impeller 7a of the torque converter 7, and a turbine 7b of the torque converter 7 is connected to an input shaft 8a of the forward / reverse switching device 8. The torque converter 7 is provided with a lock-up clutch 7c. When the lock-up clutch 7c is engaged, the output shaft 2 of the engine 1 and the turbine 7b are directly connected to each other without any fluid.
[0022]
The forward / reverse switching device 8 includes a double pinion type planetary gear 10, and the input shaft 8 a is connected to a sun gear 10 a of the planetary gear 10. The sun gear 10a and the carrier 10b can be freely engaged and disengaged via a forward clutch 11, and the ring gear 10c and the transmission case 3a can be freely engaged and disengaged via a reverse brake 12.
[0023]
When the forward clutch 11 is engaged, the planetary gear 10 rotates integrally. When the reverse brake 12 is engaged, the reverse power is transmitted to the input shaft 9a of the continuously variable transmission 9. In a state where both the forward clutch 11 and the reverse brake 12 are released, the planetary gear 10 is in a neutral state, and the transmission of power in the drive system is cut off.
[0024]
A primary pulley 9b is journalled on an input shaft 9a of the continuously variable transmission 9 connected to a carrier 10b of the forward / reverse switching device 8, and a secondary pulley 9c opposed to the primary pulley 9b is journaled on an output shaft 9d. The two pulleys 9b and 9c are connected to each other via a belt 9e. A primary hydraulic chamber 9f and a secondary hydraulic chamber 9g are provided on the movable sheave side of each of the pulleys 9b and 9c, and the working pressure supplied to each of the hydraulic chambers 9f and 9g causes the groove width of the pulleys 9b and 9c to be increased. Is set to the inverse proportional state to perform the shift control. An output shaft 9d of the continuously variable transmission 9 is connected to a differential gear 4b mounted on the drive shaft 6 via a reduction gear group 4a of the final reduction gear 4.
[0025]
Next, a hydraulic control circuit for supplying operating pressure to the lock-up clutch 7c, the forward clutch 11, the reverse brake 12, and the hydraulic chambers 9f and 9g of the continuously variable transmission 9 will be described.
[0026]
Reference numeral 21 in the figure denotes an engine-driven oil pump, which includes a main pump 21a and a sub-pump 21b, and the suction ports of both pumps 21a and 21b are connected to an oil pan 22. The discharge port of the main pump 21a is directly connected to the line pressure circuit 23, while the discharge port of the sub pump 21b is connected to the line pressure circuit 23 via the switching valve 24. The switching valve 24 performs a switching operation by a control pressure supplied from a first solenoid valve 25, and the first solenoid valve 25 is controlled based on a control signal from a control unit 26. For example, when the pump flow rate is relatively large, such as a high-speed steady operation, the switching valve 24 is closed via the first solenoid valve 25, and only the main pump 21a is connected to the line pressure circuit 23. Supply hydraulic pressure from. On the other hand, when the required flow rate is relatively large, such as during start-up acceleration, the switching valve 24 is opened, and hydraulic pressure is supplied to the line pressure circuit 23 from both the main pump 21a and the sub-pump 21b.
[0027]
The discharge pressure from the oil pump 21 supplied to the line pressure circuit 23 is regulated to a relatively high line pressure PL by a secondary pressure control valve 27 b provided in addition to a primary pressure control valve 27 a of a hydraulic control device 27. The regulated line pressure PL is supplied to the secondary hydraulic chamber 9g of the secondary pulley 9c of the continuously variable transmission 9, the primary pressure control valve 27a, and the like. The primary pressure control valve 27a reduces the line pressure PL and supplies a primary pressure Pp (Pp <PL) to a primary hydraulic chamber 9f provided on a primary pulley 9b of the continuously variable transmission 9.
[0028]
Each of the control valves 27a and 27b provided in the hydraulic control device 27 controls the primary pressure Pp and the line pressure PL in accordance with the operation amount of the second and third solenoid valves 27c and 27d that perform control operation according to a control signal from the control unit 26. Set. In the continuously variable transmission 9, the transmission control is performed by maintaining the tension of the belt 9e by the line pressure PL supplied to the secondary pulley 9c and variably setting the groove width of the primary pulley 9b by the primary pressure Pp. Do.
[0029]
A lubrication pressure circuit 28 is connected to a drain port of a secondary pressure control valve 27b of the hydraulic control device 27. The hydraulic pressure supplied from the secondary pressure control valve 27b to the lubricating pressure circuit 28 is regulated by the first relief valve 29 to a constant lubricating pressure PLUB.
[0030]
The lubricating pressure circuit 28 and the line pressure circuit 23 are connected to a forward clutch oil passage 31 that communicates with the forward clutch 11 and a reverse clutch oil passage that communicates with the reverse brake 12 via a manual valve 30 that works with a select lever (not shown). 32 can communicate freely.
[0031]
When the select lever is selected to the neutral (N) range or the parking (P) range, the manual valve 30 reduces both the line pressure PL and the lubrication pressure PLUB flowing into the forward clutch oil passage 31 and the reverse brake oil passage 32. When the drive (D) range is selected, the lubricating pressure circuit 28 communicates with the forward clutch oil passage 31 and the line pressure PL flowing into the reverse brake oil passage 32 is drained. On the other hand, when the reverse (R) range is selected, the line pressure circuit 23 communicates with the reverse brake oil passage 32 and the lubrication pressure PLUB flowing into the lubrication pressure circuit 28 is drained.
[0032]
Further, a safety lock valve 33 is interposed between the forward clutch oil passage 31 and the reverse brake oil passage 32. A bias chamber and a working chamber are provided at both ends of the safety lock valve 33, a bias spring is interposed in the bias chamber, and the lubricating pressure circuit 28 is provided in the working chamber via a fourth solenoid valve. Is connected to a control pressure circuit 34a.
[0033]
The fourth solenoid valve 34 is normally in a closed state. Therefore, a control pressure based on the lubrication pressure PLUB flowing through the lubrication pressure circuit 28 is supplied to the working chamber of the safety lock valve 33. Instead, the forward clutch oil passage 31 and the reverse brake oil passage 32 are held in a freely circulating state by receiving the biasing force of the bias spring interposed in the bias chamber. An ON signal to the fourth solenoid valve 34 is output from the control unit 26. When an ON signal is output to the fourth solenoid valve 34, the ON signal is output from the fourth solenoid valve 34 via the control pressure circuit 34a. An operating pressure based on the lubricating pressure PLUB is supplied to the operation chamber of the safety lock valve 33, and the safety lock valve 33 is slid against the biasing force of the bias spring, and the forward clutch 11 and the reverse brake 12 are slid. A forward clutch oil passage 31 and a reverse clutch oil passage 32 are respectively connected to a drain port 33a opened at the center of the safety lock valve 33, and are also connected to the manual valve 30 side. 31 and the reverse clutch oil passage 32 are shut off.
[0034]
Further, only the flow from the orifice 35, the forward clutch 11, and the reverse brake 12 to the safety lock valve 33 is allowed in the forward clutch oil passage 31 and the reverse brake oil passage 32 downstream of the safety lock valve 33. A check valve 36 is interposed in parallel.
[0035]
Further, an accumulator 37 for buffering fluctuations in the operating pressure supplied to the forward clutch 11 and the reverse brake 12 just upstream of the forward clutch 11 and the reverse brake 12 in the forward clutch oil passage 31 and the reverse brake oil passage 32. , 38 are connected. Reference numeral 39 denotes a nozzle which communicates with the lubrication pressure circuit 28 and supplies the lubrication pressure PLUB to the belt 9e of the continuously variable transmission 9.
[0036]
Reference numeral 40 denotes a lock-up control valve for controlling the operation and non-operation of the lock-up clutch 7c of the torque converter 7. The lubricating pressure circuit 28 and the first relief are provided on the inflow side of the lock-up control valve 40. A release-side lubrication pressure circuit 41 communicating with the drain port of the valve 29 is connected, and an application pressure circuit 42 communicating with the application side of the lock-up clutch 7c on the discharge side and a release pressure circuit 43 communicating with the release side. Is connected. Note that a second relief valve 44 is connected to the apply pressure circuit 42.
[0037]
Further, a control pressure circuit 46 communicating with the lubricating pressure circuit 28 via a fifth solenoid valve 45 is connected to the working chamber of the lock-up control valve 40, and a bias chamber provided to face the working chamber. And a lubricating pressure circuit 28 is connected thereto. The fifth solenoid valve 45 is controlled in accordance with a control signal output from the control unit 26, and performs a valve closing operation when lock-up is not operating and an valve opening operation when lock-up is operating.
[0038]
A working chamber of the first relief valve 29 is branched and communicated with the control pressure circuit 46. The first relief valve 29 is provided with a lubricating pressure flowing into the working chamber and a bias spring provided on the opposite side. And the relief flow rate is variably set. That is, when the fifth solenoid valve 45 is closed and the control pressure supplied to the control pressure circuit 46 is attenuated, the first relief valve 29 slides under the biasing force of the bias spring and slides to drain the lubricating oil. Increase flow rate. On the other hand, when the fifth solenoid valve 45 is opened to increase the lubricating pressure supplied to the control pressure circuit 46, the first relief valve 29 slides against the biasing force of the bias spring and slides in the amount of lubricating oil. Reduce the drain flow rate.
[0039]
As a result, when the fifth solenoid valve 45 is closed, the lubricating pressure PLUB flowing through the lubricating pressure circuit 28 decreases, and the control pressure supplied to the working chamber of the lock-up control valve 40 decreases. The lubricating pressure PLUB ′ flowing through the release-side lubricating pressure circuit 41 communicating with the relief valve 29 is increased. When the solenoid 45 is opened, the lubricating oil pressure PLUB is increased, and the control pressure supplied to the working chamber of the lock-up control valve 40 is increased. The pressure PLUB 'is reduced.
[0040]
In this embodiment, when the fifth solenoid valve 45 is closed, the lock-up is not activated, and when the fifth solenoid valve 45 is opened, the lock-up operation is activated. When the fifth solenoid valve 45 is closed, the control pressure supplied to the working chamber of the lock-up control valve 40 is attenuated, and the lubricating pressure PLUB and the bias spring flowing into the bias chamber disposed opposite to the working chamber. When the pressure is lower than the urging force of the lock-up clutch 7c, the flow path is switched by the differential pressure, and the release-side lubrication pressure circuit 41 is connected to the release pressure circuit 43 as shown in FIG. The lubricating pressure PLUB 'is supplied as the release pressure PR, and the apply pressure circuit 42 is connected to the drain oil passage 47 to discharge the apply pressure PAP supplied to the apply side, thereby releasing the lock-up clutch 7c.
[0041]
On the other hand, the fifth solenoid valve 45 is opened to increase the control pressure supplied to the working chamber of the lock-up control valve 40, and the lock-up control valve 40 is controlled by the lubrication pressure PLUB supplied to the bias chamber. When the biasing force becomes higher than the biasing force of the bias spring, the lubricating pressure circuit slides by the differential pressure, connects the lubricating pressure circuit to the apply pressure circuit, and supplies the lubricating pressure PLUB to the apply side of the lockup clutch 7c as the apply pressure PA. At the same time, the release pressure circuit 43 is communicated with the drain port to release the release pressure PR and engage the lock-up clutch 7c. The release-side lubrication pressure circuit 41 communicates with the drain oil passage 47 and is drained through an oil cooler 48.
[0042]
A lubricating oil passage 49 for guiding lubricating oil to each lubricating part such as the mechanism of the continuously variable transmission 3 is branched and connected to the drain port of the first relief valve 29.
[0043]
The lubricating pressure PLUB ′ flowing through the release-side lubricating pressure circuit 41 is regulated by a third relief valve 50 branched and connected to the release-side lubricating pressure circuit 41, and a drain port of the third relief valve 50. Is connected to the suction side of the oil pump 21.
[0044]
Next, the operation of the present embodiment will be described. The engine-driven oil pump 21 includes a main pump 21a and a sub-pump 22b. During operation of the engine, the main pump 21a constantly supplies the working oil stored in the oil pan 22 to the line pressure circuit 23. Supplies working oil to the line pressure circuit 23 via the switching valve 24 according to the operating state of the engine. The hydraulic oil supplied to the line pressure circuit 23 is regulated by the secondary pressure control valve 27b of the hydraulic control device 27 to have a predetermined line pressure PL.
[0045]
In the continuously variable transmission 9, the line pressure PL is supplied to the secondary hydraulic chamber 9g provided in the secondary pulley 9c, and the tension required for torque transmission is maintained. On the other hand, the primary pressure chamber 9f provided in the primary pulley 9b is supplied with the primary pressure Pp regulated by the primary pressure control valve 27a of the hydraulic control device 27, and the groove width of the pulley is varied by the primary pressure Pp. Thus, the shift control is performed.
[0046]
When a select lever (not shown) is selected to the D range for forward running, as shown in FIG. 1, the manual valve 30 interlocked with the select lever connects the lubrication pressure circuit 28 to the forward clutch 11 of the forward / reverse switching device 8. The reverse brake oil passage 32 communicating with the reverse brake 12 is communicated with the drain port while communicating with the forward clutch oil passage 31 that communicates.
[0047]
Then, the line pressure PL supplied to the reverse brake 12 is quickly discharged through the check valve 36, the reverse brake 12 is released, and the lubricating pressure circuit 28 flows to the forward clutch 11. The lubricating pressure PLUB is supplied as an operating pressure while being gradually increased through the orifice 35, and the forward clutch 11 engages the sun gear 10a of the planetary gear type forward / reverse switching device 8 with the carrier 10b. Are rotated together so that they can travel forward.
[0048]
Further, when the select lever is selected to the R range, the manual valve 30 performs a switching operation to connect the forward clutch oil passage 31 communicating with the forward clutch 11 to the drain port and the reverse brake oil communicating with the reverse brake 12. Line 32 is connected to line pressure circuit 23.
[0049]
Then, the operating pressure supplied to the forward clutch 11 is quickly discharged through the check valve 36, the forward clutch 11 is released, and the reverse brake 12 flows through the line pressure circuit 23. The line pressure PL is supplied as operating pressure while being gradually increased via the orifice 35, and the reverse brake 12 fixes the ring gear 10c of the forward / reverse switching device 8 to the transmission case 3a. As a result, the reverse power is transmitted to the input shaft 9a of the continuously variable transmission 9, and the vehicle can travel backward.
[0050]
As described above, when the select lever is selected to the D range, the manual valve 30 communicates the forward clutch oil passage 31 with the lubricating pressure circuit 28 to supply the lubricating pressure PLUB to the forward clutch 11 and the reverse brake. The oil passage 32 and the line pressure circuit 23 are shut off. When the select lever is selected to the R range, the manual valve 30 communicates the reverse brake oil passage 32 with the line pressure circuit 23 to supply the line pressure PL to the reverse brake 12 and the forward clutch The oil passage 31 and the lubrication pressure circuit 28 are shut off.
[0051]
Therefore, the hydraulic pressure acts on the safety lock valve 33 interposed in the forward clutch oil passage 31 and the reverse brake oil passage 32 except when the hydraulic pressure is supplied to the forward clutch 11 or the reverse brake 12. In particular, since the relatively high line pressure PL is not circulated to the reverse brake oil passage 32 except when the select lever is selected to the R range, the oil leak flow rate from the safety lock valve 33 is suppressed, As a result, not only the durability of the safety lock valve 33 is improved, but also the required flow rate of the oil pump 21 can be set relatively small, so that the transmission efficiency is improved, and the fuel efficiency, Driving performance can be improved.
[0052]
In addition, when the select lever is erroneously selected to the R range while the vehicle is traveling forward, or when the brakes are suddenly locked or the tires are locked, the continuously variable transmission 9 is allowed to move from the drive wheels 5 to the continuously variable transmission 9. When a rapid rotation fluctuation exceeding the speed is transmitted, a control signal (ON signal) is output to the fourth solenoid valve 34 by the judgment of the control unit 26. Then, the fourth solenoid valve 34 opens, and a control pressure based on the lubricating pressure PLUB flowing through the lubricating pressure circuit 28 is supplied to the working chamber of the safety lock valve 33, and the safety lock valve 33 is opened. Slides against the biasing force of the bias spring provided on the side facing the forward clutch oil passage 31 and the reverse clutch oil passage 32, which respectively communicate with the forward clutch 11 side and the reverse brake 12 side. A forward clutch oil passage 31 and a reverse clutch oil passage 32 which communicate with the drain port 33a of the safety lock valve 33 and are connected to the manual valve 30 are shut off.
[0053]
As a result, the operating pressure supplied to the forward clutch 11 or the reverse brake 12 is discharged from the drain port 33a of the safety lock valve 33, the forward clutch 11 and the reverse brake 12 are released, and the neutral state is forcibly released. Thus, the power transmission between the engine output shaft 2 and the continuously variable transmission 9 is cut off, and it is possible to effectively avoid a sudden decrease in the engine speed due to an overload or an engine stop.
[0054]
In the present embodiment, the safety lock valve 33 is interposed in the forward clutch oil passage 31 and the reverse clutch oil passage 32 between the manual valve 30 and the accumulators 37 and 38. The hydraulic valve can be disposed at a position close to the manual valve 30, and the mounting efficiency of the hydraulic circuit is improved.
[0055]
FIG. 3 shows a second embodiment of the present invention. In the above-described first embodiment, the orifice 35 and the check valve 36 are arranged in parallel in the forward clutch oil passage 31 and the reverse brake oil passage 32 between the safety lock valve 33 and the accumulators 37 and 38. 3, the orifice 35 is disposed upstream of the manual valve 30, and the orifice 35 on the accumulator 37 side and the check valve 36 are omitted.
[0056]
That is, the accumulators 37 and 38 are provided to gradually increase the pressure when supplying the operating pressure to the forward clutch 11 and the reverse brake 12, and the check valve 36 is provided for the forward clutch 11 and the reverse brake. In order to immediately discharge the operating pressure supplied to the bypass valve 12 through the accumulators 37 and 38, the orifice 35 is disposed upstream of the manual valve 30 via the orifice 35 as shown in the present embodiment. The working pressure on the forward clutch 11 or the reverse brake 12 can be gradually increased by mounting, and the forward clutch 11 or the reverse brake 12 is connected to the safety lock valve 33 by the forward clutch oil passage 31 or the reverse brake oil. Because they are directly connected via road 32 If a rotation fluctuation exceeding the allowable speed change speed of the continuously variable transmission 9 occurs, the operating pressure supplied to the forward clutch 11 or the reverse brake 12 via the safety lock valve 33 can be immediately discharged. it can.
[0057]
Therefore, in the present embodiment, the check valve 36 is not required by disposing the orifice 35 upstream of the manual valve 30, and the structure is simplified.
[0058]
FIG. 4 shows a third embodiment of the present invention. In this embodiment, the safety lock valve 33 is interposed between the forward clutch 11 and the accumulator 37 and between the forward clutch oil passage 31 and the reverse clutch oil passage 32 communicating between the reverse brake 12 and the accumulator 38. Things.
[0059]
When the capacity of the accumulators 37 and 38 is relatively small, the accumulator is placed between the safety lock valve 33 and the forward clutch 11 or the reverse brake 12 as described in the first embodiment or the second embodiment. Although the interposition of the 37 and 38 has almost no effect on the performance of discharging the operating pressure supplied to the safety lock valve 33 and the forward clutch 11 or the reverse brake 12, the capacity of the accumulators 37 and 38 is reduced. If the pressure is relatively large, the hydraulic pressure is buffered by the accumulators 37 and 38 when the operating pressure is discharged, and it may be difficult to immediately discharge the operating pressure.
[0060]
In such a case, as shown in FIG. 4, by disposing the safety lock valve 33 downstream of the accumulators 37 and 38, a rotation fluctuation exceeding the allowable speed change speed of the continuously variable transmission 9 occurs. In this case, the operating pressure supplied to the forward clutch 11 or the reverse brake 12 can be immediately discharged from the safety lock valve 33 without receiving the buffer of the accumulators 37 and 38.
[0061]
FIG. 5 shows a fourth embodiment of the present invention. In the present embodiment, the orifice 35 is disposed upstream of the manual valve 30 with respect to the third embodiment described above, and even if the accumulators 37 and 38 have relatively large capacities, the second embodiment is used. The same operation and effect as the embodiment can be obtained.
[0062]
【The invention's effect】
According to the first aspect of the present invention, the planetary gear type forward / reverse switching device includes a forward / reverse selection friction engagement element for setting forward / backward movement of the planetary gear type forward / backward switching device and a manual valve interlocked with the select lever. A safety lock valve is interposed in the hydraulic circuit that communicates between them to discharge the operating pressure supplied to the forward / reverse selection friction engagement element when a rotational fluctuation exceeding the allowable shift speed of the continuously variable transmission occurs. Accordingly, the hydraulic pressure is applied to the safety lock valve only when the operating pressure is supplied from the manual valve to the forward / reverse selection friction engagement element. The oil leak flow rate from the valve decreases, and not only the durability of the safety lock valve improves, but also the control flow rate of the oil pump can be relatively reduced. Min, it is possible to reduce the pump capacity, it is possible to improve the transmission efficiency in the entire operating range, it is possible to achieve fuel consumption, and to improve the running performance.
[0063]
According to a second aspect of the present invention, in the first aspect of the invention, an accumulator is interposed in a hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element, and the safety lock is provided. By interposing a valve in the hydraulic circuit between the manual valve and the accumulator, the safety lock valve can be disposed at a position close to the manual valve, and the mounting efficiency of the hydraulic circuit is improved. .
[0064]
According to a third aspect of the present invention, in the first aspect of the present invention, an accumulator is interposed in a hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element, and the safety lock is provided. By interposing a valve in the hydraulic circuit between the accumulator and the forward / reverse selection friction engagement element, even if the capacity of the accumulator is relatively large, rotation exceeding the permissible shift speed of the continuously variable transmission is performed. When the fluctuation occurs, the operating pressure supplied to the forward / reverse selection friction engagement element from the safety lock valve can be immediately discharged without being affected by the accumulator.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a drive system of the continuously variable transmission.
FIG. 3 is a hydraulic circuit diagram of a continuously variable transmission according to a second embodiment of the present invention.
FIG. 4 is a hydraulic circuit diagram of a continuously variable transmission according to a third embodiment of the present invention.
FIG. 5 is a hydraulic circuit diagram of a continuously variable transmission according to a fourth embodiment of the present invention.
[Explanation of symbols]
8 ... Planetary gear type forward / reverse switching device
9 ... continuously variable transmission
11: Forward / backward selection friction engagement element (forward clutch)
12: Forward / backward selection friction engagement element (reverse brake)
30 Manual valve
31 ... Hydraulic circuit (forward clutch oil passage)
32 ... Hydraulic circuit (reverse clutch oil passage)
33… Safety lock valve
37, 38 ... accumulator

Claims (3)

With a planetary gear type forward / reverse switching device interposed in the drive system,
A hydraulic circuit communicating with the forward / reverse selection friction engagement element provided in the planetary gear type forward / reverse switching device is interlocked with a select lever, and when forward traveling is selected, the planetary gear type forward / backward switching device is rotated forward to select reverse traveling. Sometimes in a continuously variable transmission connected to a manual valve that switches the working pressure to reverse the planetary gear type forward / reverse switching device,
The hydraulic circuit that communicates the manual valve and the forward / reverse selection friction engagement element, the rotation circuit that exceeds the permissible shift speed of the continuously variable transmission generates a forward / reverse selection friction engagement element. A hydraulic control circuit for a continuously variable transmission, comprising a safety lock valve for discharging a supplied operating pressure. An accumulator is interposed in a hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element,
The hydraulic control circuit for a continuously variable transmission according to claim 1, wherein the safety lock valve is interposed in a hydraulic circuit between the manual valve and the accumulator. An accumulator is interposed in a hydraulic circuit between the manual valve and the forward / reverse selection friction engagement element,
2. The hydraulic control circuit for a continuously variable transmission according to claim 1, wherein the safety lock valve is interposed in a hydraulic circuit between the accumulator and the forward / reverse selection friction engagement element.

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