CN112628391B

CN112628391B - Hydraulic control device and hydraulic control method for continuously variable transmission

Info

Publication number: CN112628391B
Application number: CN202011073537.2A
Authority: CN
Inventors: 矢崎徹
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2019-10-07
Filing date: 2020-10-09
Publication date: 2022-04-19
Anticipated expiration: 2040-10-09
Also published as: JP2021060073A; JP6933698B2; CN112628391A

Abstract

The present invention relates to a hydraulic control apparatus and a hydraulic control method for a continuously variable transmission. A CVT control unit (48) of the control device (10) detects the speed ratio from the rotational speeds (Ndr, Ndn) of the drive pulley (36) and the driven pulley (38), determines a command value (Pcc) for the detected shift pressure, and controls the hydraulic control valve (46) according to the determined command value (Pcc). When the predicted lubrication pressure (Plub) is less than a threshold value (Plubth), the CVT control unit (48) changes the command value (Pcc) so that the lubrication pressure (Plub) becomes equal to or greater than the threshold value (Plubth). Accordingly, hydraulic control of an appropriate gear ratio can be achieved only by the pump driven by the drive source of the vehicle.

Description

Hydraulic control device and hydraulic control method for continuously variable transmission

Technical Field

The present invention relates to a hydraulic control apparatus and a hydraulic control method that vary groove widths of a drive pulley (drive pulley) and a driven pulley (drive pulley) by supplying hydraulic pressure to a continuously variable transmission having an endless transmission belt (end transmission belt) wound around the drive pulley and the driven pulley, and thereby vary a gear ratio.

Background

Japanese patent application publication No. 5316692 (hereinafter, referred to as "document 1"), japanese patent application publication No. 3938897 (hereinafter, referred to as "document 2"), and japanese patent application publication No. 6130860 (hereinafter, referred to as "document 3") disclose a hydraulic control apparatus and a hydraulic control method for changing a gear ratio by supplying hydraulic pressure to a continuously variable transmission in which an endless belt is wound around a drive pulley and a driven pulley, and changing groove widths of both pulleys.

Among them, document 1 discloses that, in order to suppress an excessive increase in the integral term of the feedback control due to a rapid change in the target speed ratio, a variable amount of the thrust force of each pulley is calculated from a lower limit thrust force required to maintain the speed ratio without slipping a belt member (endless transmission belt) from each pulley and an upper limit thrust force in consideration of durability of the belt member, a limit speed (limit value of the speed of change of the speed ratio) is calculated from the calculated variable amount, and the target speed ratio is limited based on the calculated limit speed.

Document 2 discloses that when the oil temperature is equal to or higher than a set temperature, an input torque is calculated from a throttle opening, a pulley ratio (pulley ratio) is calculated from the rotational speeds of a primary pulley (drive pulley) and a secondary pulley (driven pulley), a required flow rate of lubricating oil to be supplied to a belt member is calculated from the input torque, the rotational speed of the primary pulley, and the pulley ratio, and a discharge flow rate of a pump is set from the calculated required flow rate.

Document 3 discloses that, when a hydraulic fluid is supplied to an automatic transmission mechanism and a hydraulic control valve from a pump driven by an engine, and a part of the hydraulic fluid discharged from a main pump is pressurized by a sub-pump (sub-pump) driven by an electric motor and then supplied to the hydraulic control valve, if the pressure of the hydraulic fluid supplied to the automatic transmission mechanism is lower than a predetermined pressure, the hydraulic fluid pressurized by the sub-pump is supplied to the hydraulic control valve, and if the pressure of the hydraulic fluid supplied to the automatic transmission mechanism is equal to or higher than the predetermined pressure, the driving of the sub-pump is stopped.

Disclosure of Invention

In the hydraulic control of document 1, since the contact state of the belt member with the pulley is more severe than usual at the limit shift speed, it is necessary to consider the lubrication state of the belt member. Since the belt member lubrication apparatus has various types, a hydraulic control method for lubricating the belt member without depending on the type is required.

In contrast, in document 2, when the discharge flow rate of the pump cannot be changed, the hydraulic pressure control cannot be appropriately performed. In addition, in document 3, when the sub-pump is driven when the pressure of the hydraulic fluid is lower than a predetermined pressure, the flow rate of the hydraulic fluid supplied from the main pump is further reduced. Accordingly, the oil cannot be supplied to the lubricating portion such as the belt member of the continuously variable transmission at a required flow rate.

As described above, in the continuously variable transmission, in addition to the flow rate required for shifting, there is a flow rate (required flow rate) required for lubrication of the belt member and the like. Therefore, a large capacity pump is required for hydraulic control of the continuously variable transmission. Therefore, a hydraulic control method is required for a continuously variable transmission mounted on a vehicle, in which a transmission ratio and a shift speed (a speed of change in the transmission ratio) can be controlled without depending on a lubricating device only by a pump driven by a drive source (for example, an engine) of the vehicle.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a hydraulic control device and a hydraulic control method for a continuously variable transmission capable of controlling a speed ratio (shift speed) while securing a flow rate necessary for lubrication of an endless transmission belt or the like, only by a pump driven by a drive source of a vehicle.

An aspect of the present invention relates to a hydraulic control device and a hydraulic control method for a continuously variable transmission having a drive pulley, a driven pulley, and an endless belt wound around the drive pulley and the driven pulley, which change groove widths of the drive pulley and the driven pulley by supplying hydraulic pressure to the continuously variable transmission, and change a transmission ratio.

In this case, the hydraulic control apparatus has a pump that supplies the hydraulic pressure, a valve portion, a gear ratio detection portion, a command value determination portion, a valve control portion, and a command value change portion; the valve unit controls the supply of the hydraulic pressure from the pump to each unit in the continuously variable transmission; the speed ratio detection unit detects the speed ratio based on the respective rotation speeds of the drive pulley and the driven pulley; the command value determination unit determines a command value of a shift pressure, which is a hydraulic pressure supplied to the drive pulley and the driven pulley; the valve control portion controls the supply of the hydraulic pressure by controlling the valve portion according to the command value; the command value changing unit changes the command value so that the lubrication pressure becomes equal to or higher than a threshold value when the valve control unit is expected to control the supply of the hydraulic pressure based on the command value so that the lubrication pressure, which is the hydraulic pressure supplied to the endless transmission belt, becomes smaller than the threshold value.

Further, the hydraulic control method includes: detecting the speed ratio by a speed ratio detection unit based on the respective rotation speeds of the drive pulley and the driven pulley while the hydraulic pressure is being supplied from a pump to each unit in the continuously variable transmission through a valve unit; a command value determination unit that determines a command value of a shift pressure, which is a hydraulic pressure supplied to the drive pulley and the driven pulley; controlling the supply of the hydraulic pressure by controlling the valve portion by a valve control portion in accordance with the command value; when it is expected that the supply of the hydraulic pressure is controlled by the valve control unit based on the command value so that the lubrication pressure, which is the hydraulic pressure supplied to the endless transmission belt, is less than a threshold value, the command value changing unit changes the command value so that the lubrication pressure becomes equal to or greater than the threshold value.

According to the present invention, since the hydraulic control for feeding back the lubrication pressure is performed, the lubrication pressure can be secured regardless of the state of the hydraulic control for the continuously variable transmission. Accordingly, the hydraulic pressure can be controlled at a speed ratio (speed change speed) corresponding to the lubrication pressure. As a result, hydraulic control of an appropriate speed ratio (shift speed) can be achieved by only the pump driven by the drive source of the vehicle without depending on the lubrication device.

The above objects, features and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings.

Drawings

Fig. 1 is a configuration diagram of a control device according to the present embodiment.

Fig. 2 is a structural view of the hydraulic control valve.

Fig. 3 is a partial configuration diagram of a control device showing the arrangement of the lubrication pressure sensor.

Fig. 4 is a flowchart showing a process of the control device of fig. 1.

Fig. 5 is a flowchart showing details of the processing of step S8 in fig. 4.

Fig. 6 is an explanatory diagram showing a relationship between the lubrication pressure and the lubrication flow rate.

Fig. 7 is an explanatory diagram showing a relationship between an operation state of the lock-up clutch and the lubrication pressure.

Fig. 8 is an explanatory diagram showing a relationship between the rotation speed of the drive pulley and the lubrication pressure.

Fig. 9 is an explanatory diagram showing a relationship between the rotation speed of the driven pulley and the lubrication pressure.

Fig. 10 is an explanatory diagram showing a relationship between the speed ratio (gear ratio) and the lubricating pressure.

Fig. 11 is an explanatory diagram showing a relationship between the shift pressure and the lubrication pressure.

Detailed Description

The hydraulic control device and the hydraulic control method for a continuously variable transmission according to the present invention will be described below with reference to the drawings by way of examples of preferred embodiments.

[1. Structure of the present embodiment ]

As shown in fig. 1, a hydraulic control device 10 of a continuously variable transmission according to the present embodiment (hereinafter, also referred to as a control device 10 according to the present embodiment) is mounted on a vehicle 14 that uses an engine 12 as a drive source, for example. Fig. 1 is a schematic configuration diagram of a control device 10 that performs hydraulic control of a metal belt type continuously variable transmission 16 (CVT).

A torque converter (torque converter)18 as a rotation transmission mechanism is connected to an output shaft 23 of the engine 12. The torque converter 18 has a lock-up clutch 20 that directly connects the engine 12 and the continuously variable transmission 16. A ring gear 24 of the forward/reverse switching mechanism 22 is connected to the output side of the torque converter 18. The forward-reverse switching mechanism 22 is constituted by a planetary gear mechanism including: a ring gear 24 connected to the output shaft 23 of the engine 12; a pinion carrier (pinion carrier) 26; and a sun gear 30 connected to the input shaft 28 of the continuously variable transmission 16. A reverse brake 32 and a forward clutch 34 are provided on the pinion carrier 26, wherein the reverse brake 32 fixes the pinion carrier 26 to a housing of the continuously variable transmission 16; the forward clutch 34 integrally connects the input shaft 28 of the continuously variable transmission 16 and the pinion carrier 26.

The continuously variable transmission 16 has: a drive pulley 36 provided on the input shaft 28; a driven pulley 38; and a belt member 40 (endless transmission belt) that is wound around the drive pulley 36 and the driven pulley 38.

The drive pulley 36 includes: a fixed pulley half 36a that is rotatable with respect to the input shaft 28; and a movable pulley half 36b that is slidable in the axial direction of the input shaft 28 with respect to the fixed pulley half 36 a. The movable pulley half 36b has a V-shaped groove width (groove width of the drive pulley 36) variable with respect to the fixed pulley half 36a by a hydraulic pressure acting on the hydraulic oil chamber 36 c.

The driven pulley 38 is supported by a driven shaft 42. The driven pulley 38 has: a fixed-side pulley half 38a fixed to the driven shaft 42; and a movable pulley half 38b that is slidable in the axial direction of the driven shaft 42 relative to the fixed pulley half 38 a. The V-shaped groove width (groove width of the driven pulley 38) between the movable pulley half 38b and the fixed pulley half 38a is variable by the hydraulic pressure acting on the hydraulic oil chamber 38 c.

A drive gear, not shown, is fixed to the driven shaft 42. The drive gear is connected to the wheels through a pinion gear provided on an idler shaft (idler axis), an end drive gear, and a differential. Therefore, the rotational force from the output shaft 23 of the engine 12 is transmitted to the input shaft 28 of the continuously variable transmission 16 through the torque converter 18 and the forward/reverse switching mechanism 22. In the continuously variable transmission 16, the rotational force of the input shaft 28 is transmitted to the differential device through the drive pulley 36, the belt member 40, the driven pulley 38, the driven shaft 42, the drive gear, the idler shaft, the pinion gear, and the final drive gear.

A nozzle pipe 44 is disposed between the drive pulley 36 and the driven pulley 38 along the axial direction of the input shaft 28 and the driven shaft 42. One end of the nozzle pipe 44 is connected to a hydraulic control valve 46, and the other end is closed. An oil jet hole 44a opening on the drive pulley 36 side and an oil jet hole 44b opening on the driven pulley 38 side are formed in the peripheral wall of the nozzle pipe 44. One oil jet hole 44a opens to a portion of the belt member 40 wound around the drive pulley 36, and the other oil jet hole 44b opens to a portion of the belt member 40 wound around the driven pulley 38.

By moving the movable-side

pulley half bodies

36b and 38b of the drive pulley 36 and the driven pulley 38 in the axial direction, the groove widths of the drive pulley 36 and the driven pulley 38 can be changed, thereby changing the rotation ratio, that is, the speed ratio of the drive pulley 36 and the driven pulley 38. When the oil is supplied to the nozzle pipe 44, the oil is injected from one oil jet hole 44a to the portion of the belt member 40 wound around the drive pulley 36, and the oil is injected from the other oil jet hole 44b to the portion of the belt member 40 wound around the driven pulley 38. Accordingly, the belt member 40 can be lubricated and cooled efficiently.

The change of the V-shaped groove width and the supply of the hydraulic fluid to the belt member 40 through the nozzle pipe 44 are performed by controlling a hydraulic control valve 46 (valve unit) by a CVT control unit 48 (gear ratio detection unit, command value determination unit, valve control unit, command value change unit). The CVT control unit 48 is an electronic control device including a microprocessor or the like, and functions as a gear ratio detection unit, a command value determination unit, a valve control unit, and a command value change unit by reading and executing programs stored in a memory, not shown.

The control device 10 has, in addition to the CVT control unit 48 and the hydraulic control valve 46, a pump 50, a shift mode sensor 52, a throttle opening degree sensor 54, a line pressure sensor 56, a pump rotation speed sensor 58, an engine rotation speed sensor 60, a drive pulley rotation speed sensor 62, a driven pulley rotation speed sensor 64, a pulley clamping pressure sensor 66, and a lubrication pressure sensor 68.

The pump 50 is a mechanical pump driven in accordance with the rotation of the engine 12, and supplies the hydraulic fluid from a tank, not shown, to the continuously variable transmission 16. The hydraulic control valve 46 is a valve unit that controls supply of the hydraulic fluid sent from the pump 50 to each unit in the continuously variable transmission 16, and includes various hydraulic control valves. The structure of the hydraulic control valve 46 will be described later.

The shift mode sensor 52 detects whether the driving mode is the automatic shift mode or the manual shift mode, based on a state of a shift mode change switch (external request) provided in a shift lever (not shown) of the vehicle 14.

The throttle opening sensor 54 detects the opening of a throttle valve (throttle opening, external request), not shown. The pump rotation speed sensor 58 detects the rotation speed Np of the pump 50. The engine rotation speed sensor 60 detects the rotation speed Ne of the engine 12. The drive pulley rotation speed sensor 62 detects the rotation speed Ndr of the drive pulley 36. The driven pulley rotation speed sensor 64 detects the rotation speed Ndn of the driven pulley 38.

The line pressure sensor 56 detects a line pressure PH, which is a pressure (hydraulic pressure) of the oil liquid regulated by the hydraulic control valve 46, with respect to the oil liquid supplied from the pump 50. The pulley clamping pressure sensor 66 detects the pressure (hydraulic pressure) of the hydraulic fluid supplied from the hydraulic control valve 46 to the hydraulic fluid chamber 36c of the drive pulley 36, that is, the hydraulic pressure when the drive pulley 36 clamps the belt member 40, as the clamping pressure Pc. The lubrication pressure sensor 68 detects the pressure (hydraulic pressure) of the oil supplied from the hydraulic control valve 46 to the lubrication portion of the belt member 40 or the like as a lubrication pressure Plub.

The line pressure PH is the original pressure of the hydraulic fluid supplied from the hydraulic control valve 46 to each part of the continuously variable transmission 16. In addition, the clamping pressure Pc of the drive pulley 36 is lower than the line pressure PH. On the other hand, the pressure of the hydraulic fluid supplied to the hydraulic fluid chamber 38c of the driven pulley 38, that is, the clamping pressure Pc when the driven pulley 38 clamps the belt member 40, is substantially the same pressure as the line pressure PH. The lubrication pressure Plub is a hydraulic pressure lower than the line pressure PH and the respective clamp pressures Pc.

The detection results of these various sensors are sequentially input to the CVT control unit 48.

The CVT control unit 48 determines a gear ratio based on the detection results input from the sensors, and detects a command value Pcc of a shift pressure (clamping pressure Pc) that is the pressure of the hydraulic fluid supplied to the drive pulley 36 and the driven pulley 38 based on an external request such as a throttle opening. The CVT control unit 48 controls the hydraulic control valve 46 based on the command value Pcc, thereby controlling the pressure (hydraulic pressure) of the hydraulic fluid supplied to each part of the continuously variable transmission 16. When the lubrication pressure Plub expected to be supplied to the belt member 40 is smaller than a predetermined threshold value Plubth, the CVT control unit 48 changes the command value Pcc such that the lubrication pressure Plub becomes equal to or greater than the threshold value Plubth. The CVT control unit 48 has a map (map)70 indicating a relationship with the threshold value Plubth, and executes the process of changing the command value Pcc with reference to the map 70. The details of the operation of the CVT control unit 48 will be described later.

As shown in fig. 2, the hydraulic control valve 46 includes a regulator valve 46a connected to the pump 50, an LC shift valve (shift valve)46b connected to the downstream side of the regulator valve 46a, and the like. Fig. 2 shows only the valves necessary for the description of the present embodiment, out of the hydraulic control valve 46. Therefore, in practice, since the hydraulic fluid is supplied to each part of the continuously variable transmission 16, it is noted that a plurality of valves are arranged in the hydraulic control valve 46.

The regulator valve 46a generates the line pressure PH by regulating the hydraulic pressure of the oil supplied from the pump 50. The oil of the line pressure PH is supplied to the

hydraulic oil chambers

36c and 38c of the drive pulley 36 and the driven pulley 38. The oil liquid at the line pressure PH is regulated by the LC shift valve 46b, and distributed and supplied to the torque converter 18 and the belt member 40. Note that the pressure of the oil supplied to the belt member 40 (lubrication pressure Plub) is lower than the pressure of the oil supplied to the torque converter 18 (lock-up clutch 20). Further, since the LC shift valve 46b distributes the supply oil to the torque converter 18 and the belt member 40, the lubricating pressure Plub of the belt member 40 is affected by the lock-up clutch 20.

As shown in fig. 2 and 3, the LC shift valve 46b is a valve for controlling the lock-up clutch 20 of the torque converter 18, and changes the lubrication pressure Plub by changing the position of the valve. The LC shift valve 46b supplies the distributed oil to the belt member 40, the driven shaft 42 of the driven pulley 38, and the like. In this case, an oil supply passage 42a is formed in the axial center of the driven shaft 42. The driven shaft 42 is provided with a communication hole 42b that communicates the oil supply passage 42a with the outer peripheral surface. Accordingly, the hydraulic fluid supplied from the LC shift valve 46b to the hydraulic fluid supply passage 42a passes through the communication hole 42b, and lubricates the gear 72 and the bearing 74 disposed on the driven shaft 42. Further, the lubrication pressure sensor 68 detects the pressure of the oil supplied from the LC shift valve 46b to the belt member 40, the driven shaft 42, and the like as the lubrication pressure Plub. In addition, when the oil supplied to the belt member 40 is insufficient, the negative pressure is generated by the rotation of the driven shaft 42, and therefore the lubrication pressure sensor 68 can detect the negative lubrication pressure Plub.

[2. operation of the present embodiment ]

The operation of the control device 10 according to the present embodiment (the hydraulic pressure control method of the continuously variable transmission according to the present embodiment) configured as described above will be described with reference to fig. 4 to 11. Here, a case will be described in which the CVT control unit 48 determines or changes the command value Pcc of the shift pressure, and controls the hydraulic control valve 46 based on the determined or changed command value Pcc to control the pressure (hydraulic pressure) supply of the hydraulic fluid to each part of the continuously variable transmission 16. In this operation description, a description will be given with reference to fig. 1 to 3 as necessary.

As described above, the lubricating pressure Plub of the oil supplied to the lubricating system of the belt member 40 and the like is lower than the pressure of the oil supplied to the other parts of the continuously variable transmission 16. Therefore, it is susceptible to clutch pressure and the like that require high pressure. For example, the lubrication pressure Plub may be 0 when the clamping pressure Pc (hereinafter also referred to as a pulley pressure) needs to be high to increase the speed change (the speed of change of the transmission ratio) and a large amount of oil needs to be supplied through the drive pulley 36 and the driven pulley 38, or when the rotation speed Np of the pump 50 is low. Therefore, in the present embodiment, by feeding back the lubrication pressure Plub to the CVT control unit 48, the continuously variable transmission 16 can be hydraulically controlled at the shift speed at which the lubrication pressure Plub is ensured. In the present embodiment, the hydraulic pressure control is performed based on the feedback control using the lubrication pressure Plub without a special sensor.

In step S1 of fig. 4, the CVT control unit 48 (see fig. 1) determines whether or not the engine 12 and the continuously variable transmission 16 are connected by the operation of the lock-up clutch 20. In this case, the CVT control unit 48 determines whether the lockup clutch 20 is operating, based on the lubrication pressure Plub detected by the lubrication pressure sensor 68 (see fig. 1 and 3) and the map 70.

The map 70 stores various maps shown in fig. 6 to 11. In step S1, the maps of fig. 6 and 7 are referred to.

Fig. 6 shows a relationship between the lubrication pressure Plub of the belt member 40 (see fig. 1 to 3) and the flow rate of the oil supplied to the belt member 40 (lubrication flow rate). The map of fig. 6 is a map in which the lubrication pressure Plub and the lubrication flow rate measured in advance are plotted. The lubrication flow rate of the belt member 40 depends on the lubrication pressure Plub. Therefore, if the lubrication pressure Plub is ensured, the lubrication flow rate can be ensured. Therefore, in the present embodiment, the lubrication pressure Plub corresponding to the minimum lubrication flow rate required for lubrication of the belt member 40 is set as the threshold value Plubth.

In addition, in the following description, it is noted that the threshold values Plubth shown in fig. 7 to 11 are set to the same values. The maps in fig. 7 to 11 are maps obtained by plotting the previously measured lubrication pressure Plub and the like.

Fig. 7 is a map illustrating changes in the lubrication pressure Plub in the operating state (LC ON) and the non-operating state (LC OFF) of the lockup clutch 20 (see fig. 1). As described above, the lubrication pressure Plub of the belt member 40 (see fig. 1 to 3) is affected by the pressure and flow rate of the oil supplied to the lockup clutch 20, that is, the operating state and the non-operating state of the lockup clutch 20. As shown in fig. 7, in the operating state (LC ON) of the lock-up clutch 20, the lubrication pressure Plub is in a relatively low state, and ON the other hand, in the non-operating state (LC OFF), the lubrication pressure Plub is in a relatively high state.

In the map of fig. 7, the lower limit value of the lubrication pressure Plub corresponding to the operation state is set in advance as the threshold value Plubth. In step S1, the CVT control unit 48 determines that the lock-up clutch 20 is in the operating state when the lubrication pressure Plub detected by the lubrication pressure sensor 68 is less than the threshold value Plubth (step S1: yes). On the other hand, in step S1, when the lubrication pressure Psub detected by the lubrication pressure sensor 68 is equal to or greater than the threshold value Psub, the CVT control unit 48 determines that the lock-up clutch 20 is in the non-operating state (step S1: NO). In addition, in the operating state (LC ON), when the lubrication pressure Plub is in a relatively low state and the lower limit value of the lubrication pressure Plub is smaller than the threshold value Plubth, the process of step S2 can be executed with step S1 skipped. In this case, the case where the lubrication flow rate is insufficient is also basically included.

If the determination result in step S1 is positive (yes in step S1), the CVT control unit 48 proceeds to next step S2 to acquire the rotation speed Np of the pump 50 detected by the pump rotation speed sensor 58. Further, as described above, the pump 50 is rotated by the driving of the engine 12, and the drive pulley 36 is rotated by the rotational force transmitted from the engine 12 via the torque converter 18. Therefore, in step S2, the CVT control unit 48 may acquire at least 1 rotation speed Np, Ndr, Ne among the rotation speed Np of the pump 50, the rotation speed Ndr of the drive pulley 36 detected by the drive pulley rotation speed sensor 62, and the rotation speed Ne of the engine 12 detected by the engine rotation speed sensor 60.

In step S3, the CVT control unit 48 determines whether or not it is a rotational speed at which the lubrication pressure Plub is less than the threshold value Plubth, based on any of the acquired rotational speeds Np, Ndr, Ne and the map of fig. 8. As an example, the map of fig. 8 is a map showing the relationship between the rotation speed Ndr of the drive pulley 36 and the lubrication pressure Plub. In fig. 8, the lubrication pressure Plub is smaller than the threshold value Plubth within the range of the prescribed rotational speed Ndr. That is, in this range of the rotation speed Ndr, it is expected that the lubrication pressure Plub required for the lubrication of the belt member 40 cannot be secured (step S3: YES).

If the determination result in step S3 is positive (yes in step S3), the CVT control unit 48 proceeds to the next step S4 to calculate (detect) the speed ratio from the rotational speeds Ndr, Ndn of the drive pulley 36 and the driven pulley 38.

In step S5, the CVT control unit 48 determines whether or not the speed ratio is one in which the lubrication pressure Plub is smaller than the threshold value Plubth, based on the speed ratio and the map of fig. 9. As an example, the map of fig. 9 is a map showing the relationship between the rotation speed Ndn of the driven pulley 38 and the lubrication pressure Plub according to the gear ratio. In fig. 9, in the range of the prescribed rotation speed Ndn, the lubrication pressure Plub is smaller than the threshold value Plubth, and the lubrication pressure Plub required for lubrication of the belt member 40 is not expected to be ensured (step S5: yes).

In the case of an affirmative determination in step S5 (step S5: yes), the CVT control unit 48 proceeds to the next step S6 to determine a command value Pcc of the shift pressure in accordance with the external request.

In step S7, the CVT control unit 48 determines whether the lubrication pressure Plub is a command value Pcc smaller than a threshold value Plubth, based on the command value Pcc of the shift pressure and the map of fig. 10. The map of fig. 10 is a map showing the change in each shift pressure when the horizontal axis represents the speed ratio (speed ratio) and the vertical axis represents the lubrication pressure Plub. In fig. 10, the change in the command value Pcc of the shift pressure is illustrated by a solid line, a one-dot chain line, and a two-dot chain line for each shift pressure.

In this case, even with the same shift pressure, depending on the magnitude of the speed ratio (gear ratio), there is a range in which the lubrication pressure Plub is smaller than the threshold value Plubth, and the lubrication pressure Plub necessary for the lubrication of the belt member 40 cannot be secured (step S7: yes). Further, as indicated by the one-dot chain line and the two-dot chain line, it is clear that the lubrication flow rate is insufficient when the lubrication pressure becomes negative.

In this way, if the determination result is affirmative in step S7 (yes in step S7), the CVT control unit 48 proceeds to next step S8 to change the command value Pcc of the shift pressure so that the lubrication pressure Plub becomes equal to or higher than the threshold value Plubth. After changing the command value Pcc, the CVT control unit 48 returns to step S6 and executes the processing of steps S6 and S7 again.

In the case of a negative determination result in step S7, i.e., in the case where the lubrication pressure Plub reaches the command value Pcc that is equal to or greater than the threshold value Plubth (step S7: no), the CVT control unit 48 proceeds to step S9, and acquires the current lubrication pressure Plub from the lubrication pressure sensor 68.

In the next step S10, the CVT control unit 48 determines whether the acquired lubrication pressure Plub is equal to or greater than the threshold value Plubth, based on the acquired lubrication pressure Plub and the map of fig. 11. Fig. 11 is a map showing the change in each speed ratio (speed ratio) when the horizontal axis is the shift pressure and the vertical axis is the lubrication pressure Plub. In fig. 11, the change in the lubrication pressure Plub is illustrated with a solid line, a one-dot chain line, and a two-dot chain line for each speed ratio (gear ratio).

In this case, even if the speed ratio (speed change ratio) is the same, depending on the magnitude of the shift pressure, the lubrication pressure Plub may be smaller than the threshold value Plubth and the lubrication pressure Plub necessary for lubrication of the belt member 40 may not be ensured (step S10: no). Further, as indicated by the one-dot chain line and the two-dot chain line, it is clear that the lubrication flow rate is insufficient when the lubrication pressure becomes negative.

In this way, if the determination result in step S10 is negative (no in step S10), the CVT control unit 48 proceeds to step S8 to change the command value Pcc of the shift pressure so that the lubrication pressure Plub becomes equal to or greater than the threshold value Plubth.

On the other hand, if the result of the affirmative determination in step S10 (step S10: yes), if it is the determined command value Pcc or the changed command value Pcc, the CVT control unit 48 determines that the lubrication pressure Plub has reached the threshold value Plubth or more, and proceeds to the next step S11.

In step S11, the CVT control unit 48 controls the hydraulic pressure control valve 46 based on the determined command value Pcc or the changed command value Pcc, thereby controlling the supply of the hydraulic pressure to the continuously variable transmission 16.

On the other hand, if the determination results in the negative in steps S3, S5 (steps S3, S5: NO), the CVT control unit 48 controls the hydraulic pressure control valve 46 in accordance with the currently set command value Pcc. If the determination result in step S1 is negative (no in step S1), the CVT control unit 48 skips the process of the hydraulic pressure control this time.

Fig. 5 is a flowchart showing details of the processing of step S8. As described above, if the lubrication pressure Plub is smaller than the command value Pcc of the threshold value Plubth, there is a possibility that the gear shift cannot be performed when the hydraulic control is performed based on the command value Pcc. Step S8 is a process for changing to the variable speed command value Pcc.

First, in step S81, it is determined whether or not the shift pressure is smaller than a pressure capable of holding the gear ratio (gear ratio holding pressure).

If the determination result in step S81 is affirmative (step S81: yes), the CVT control unit 48 determines that the shift may not be possible when the command value Pcc of the shift pressure determined in step S6 is changed, and proceeds to the next step S82.

In step S82, the CVT control unit 48 changes (limits) the input torque to the continuously variable transmission 16 so that the shifting operation is possible. In step S83, the CVT control unit 48 changes (reduces) the pulley holding pressure so as to enable the shifting operation. Accordingly, in step S84, the CVT control unit 48 determines the changed command value Pcc as the command value Pcc for controlling the hydraulic pressure control valve 46.

On the other hand, if the determination result in step S81 is negative (no in step S81), the CVT control unit 48 determines that the shift operation is possible, and in step S84, determines the command value Pcc determined in step S6 as the command value Pcc for controlling the hydraulic pressure control valve 46 without changing the command value Pcc.

[3. modification ]

In the present embodiment, the continuously variable transmission 16 in which the belt member 40 is a metal belt is explained. In the present embodiment, the present invention can be applied to a continuously variable transmission 16 of a chain type. In the present embodiment, a case where the present embodiment is applied to the vehicle 14 having the engine 12 as a drive source is described. The present invention can also be applied to a vehicle (for example, an electric vehicle driven by a battery and a motor) that uses a drive source other than the engine 12.

In steps S9 and S10 in fig. 4, a case where the detected value of the lubrication pressure Plub is compared with the threshold value Plubth is described. When the lubrication pressure Plub cannot be measured, or when the determination processing in step S10 is difficult to perform due to variation in the lubrication pressure Plub, the determination processing may be performed using a map prepared by using a database of previously measured lubrication pressures Plub and the like.

[4. effect of the present embodiment ]

As described above, the present embodiment is a control device 10 (hydraulic control device of a continuously variable transmission) and a hydraulic control method for changing a transmission ratio by changing groove widths of a drive pulley 36 and a driven pulley 38 by supplying a hydraulic pressure to the continuously variable transmission 16, the continuously variable transmission 16 having the drive pulley 36, the driven pulley 38, and a belt member 40 (endless belt) wound around the drive pulley 36 and the driven pulley 38.

In this case, the control device 10 has a pump 50, the pump 50 supplying hydraulic pressure, a hydraulic pressure control valve 46 (valve portion), and a CVT control unit 48 (gear ratio detection portion, command value determination portion, valve control portion, command value change portion); the hydraulic control valve 46 controls supply of hydraulic pressure from a pump 50 to each part in the continuously variable transmission 16.

The CVT control unit 48 detects the transmission ratio from the respective rotation speeds Ndr, Ndn of the drive pulley 36 and the driven pulley 38. The CVT control unit 48 determines a command value Pcc of the hydraulic pressure, i.e., the shift pressure, to be supplied to the drive pulley 36 and the driven pulley 38. The CVT control unit 48 controls the supply of hydraulic pressure by controlling the hydraulic pressure control valve 46 in accordance with the command value Pcc. When the lubrication pressure Plub, which is the hydraulic pressure supplied to the belt member 40, is expected to be less than the threshold value Plubth by controlling the supply of the hydraulic pressure in accordance with the command value Pcc, the CVT control unit 48 changes the command value Pcc such that the lubrication pressure Plub becomes equal to or greater than the threshold value Plubth.

On the other hand, the hydraulic control method has the following steps. That is, when the hydraulic pressure is being supplied from the pump 50 to each part in the continuously variable transmission 16 through the hydraulic control valve 46, the CVT control unit 48 detects the speed ratio from the rotational speeds Ndn, Ndr of the drive pulley 36 and the driven pulley 38 (step S4); a step in which the CVT control unit 48 determines a command value Pcc of the hydraulic pressure, i.e., the shift pressure, to be supplied to the drive pulley 36 and the driven pulley 38 (step S6); a step (step S11) in which the CVT control unit 48 controls the hydraulic pressure control valve 46 in accordance with the command value Pcc to control the supply of hydraulic pressure; and a step (S7, S8) in which, when the supply of the control hydraulic pressure is predicted to make the lubrication pressure Plub, which is the hydraulic pressure supplied to the belt member 40, smaller than the threshold value Plubth, the CVT control unit 48 changes the command value Pcc so that the lubrication pressure Plub becomes equal to or greater than the threshold value Plubth.

Thus, the hydraulic control for feeding back the lubrication pressure Plub is performed, and therefore, the lubrication pressure Plub can be ensured regardless of the state of the hydraulic control for the continuously variable transmission 16. Accordingly, the hydraulic pressure control can be performed at the speed ratio (shift speed) corresponding to the lubrication pressure Plub. As a result, hydraulic control of an appropriate speed ratio (shift speed) can be achieved only by the pump driven by the drive source (engine 12) of the vehicle 14 without depending on the lubrication device.

In this case, the control device 10 further includes a pump rotation speed sensor 58 (pump rotation speed detecting unit), and the pump rotation speed sensor 58 detects the rotation speed Np of the pump 50. In the case where the rotation speed Np, the gear ratio, and the command value Pcc for which the lubrication pressure Plub is expected to be smaller than the threshold value Plubth, the CVT control unit 48 changes the command value Pcc such that the lubrication pressure Plub becomes equal to or greater than the threshold value Plubth. Accordingly, the hydraulic control at the speed change ratio at which the lubrication pressure Plub can be ensured can be performed more accurately.

The control device 10 further includes a lubrication pressure sensor 68 (lubrication pressure detecting unit), and the lubrication pressure sensor 68 detects the lubrication pressure Plub. In the case where the lubrication pressure Plub is made smaller than the rotation speed and the gear ratio of the threshold Plubth on the one hand, and the lubrication pressure Plub is made to reach the command value Pcc of the threshold Plubth or more on the other hand, the CVT control unit 48 compares the lubrication pressure Plub detected by the lubrication pressure sensor 68 with the threshold Plubth, and changes the command value Pcc such that the lubrication pressure Plub becomes the threshold Plubth or more in the case where the lubrication pressure Plub detected by the lubrication pressure sensor 68 is smaller than the threshold Plubth. On the other hand, in the case where the lubrication pressure Plub detected by the lubrication pressure sensor 68 is equal to or greater than the threshold value Plubth, the CVT control unit 48 holds the determined command value Pcc. The gear ratio can be appropriately set in accordance with the detected lubrication pressure Plub, and the hydraulic pressure control can be performed with high accuracy.

The CVT control unit 48 determines whether or not the lubrication pressure Plub is smaller than a threshold value Plubth based on a map 70, which map 70 shows the relationship between the lubrication pressure Plub measured in advance and the rotation speed Np, the shift ratio, and the command value Pcc. This allows determination or change of command value Pcc without requiring a special sensor or the like.

The hydraulic pressure control valve 46 also supplies hydraulic pressure to the lock-up clutch 20, wherein the lock-up clutch 20 connects the engine 12 and the continuously variable transmission 16. The pump 50 is driven by rotation of the engine 12. In this case, when the hydraulic pressure is being supplied from the hydraulic pressure control valve 46 to the lock-up clutch 20, the CVT control unit 48 controls the hydraulic pressure control valve 46 in accordance with the command value Pcc. Since the lubrication pressure may change depending on the operating state of the lock-up clutch 20, the hydraulic control described above can be performed more efficiently by taking the operating state into consideration.

The present invention is not limited to the above-described embodiments, and it is needless to say that various configurations can be adopted according to the contents described in the present specification.

Claims

1. A hydraulic control device (10) for a continuously variable transmission, the hydraulic control device (10) changing groove widths of a drive pulley (36) and a driven pulley (38) and changing a gear ratio by supplying hydraulic pressure to the continuously variable transmission (16), wherein the continuously variable transmission (16) has the drive pulley (36), the driven pulley (38), and an endless belt (40) wound around the drive pulley and the driven pulley,

it is characterized in that the preparation method is characterized in that,

comprises a pump (50), a valve unit (46), a gear ratio detection unit, a command value determination unit, a valve control unit, and a command value change unit,

the pump (50) supplies the hydraulic pressure;

the valve unit (46) controls the supply of the hydraulic pressure from the pump to each unit in the continuously variable transmission;

the speed ratio detection unit detects the speed ratio based on the respective rotation speeds of the drive pulley and the driven pulley;

the command value determination unit determines a command value of a shift pressure, which is a hydraulic pressure supplied to the drive pulley and the driven pulley;

the valve control portion controls the supply of the hydraulic pressure by controlling the valve portion according to the command value;

the command value changing unit changes the command value so that the lubrication pressure becomes equal to or higher than a threshold value when the valve control unit is expected to control the supply of the hydraulic pressure based on the command value so that the lubrication pressure, which is the hydraulic pressure supplied to the endless transmission belt, becomes smaller than the threshold value.

2. The hydraulic control apparatus of a continuously variable transmission according to claim 1,

further comprises a pump rotational speed detection unit (58), the pump rotational speed detection unit (58) detecting the rotational speed of the pump,

when the rotation speed of the pump, the gear ratio, and the command value are expected to make the lubrication pressure smaller than the threshold value, the command value changing unit changes the command value so that the lubrication pressure becomes equal to or larger than the threshold value.

3. The hydraulic control apparatus of a continuously variable transmission according to claim 2,

further comprising a lubrication pressure detection unit (68), the lubrication pressure detection unit (68) detecting the lubrication pressure,

the command value changing unit compares the lubrication pressure detected by the lubrication pressure detecting unit with the threshold value when the rotation speed and the gear ratio of the pump are set such that the lubrication pressure is smaller than the threshold value and the lubrication pressure is set to the command value equal to or larger than the threshold value,

on the one hand, when the lubrication pressure detected by the lubrication pressure detection unit is smaller than the threshold value, the command value changing unit changes the command value so that the lubrication pressure becomes equal to or greater than the threshold value, and on the other hand, when the lubrication pressure detected by the lubrication pressure detection unit is equal to or greater than the threshold value, the command value changing unit holds the command value specified by the command value specifying unit.

4. The hydraulic control apparatus of a continuously variable transmission according to claim 2 or 3,

the command value changing unit determines whether or not the lubrication pressure is less than the threshold value on the basis of a map (70), wherein the map (70) represents a relationship between the lubrication pressure, the rotation speed of the pump, the gear ratio, and the command value, which are measured in advance.

5. A hydraulic control method for a continuously variable transmission having a drive pulley, a driven pulley, and an endless belt wound around the drive pulley and the driven pulley, wherein a groove width of the drive pulley and the driven pulley is changed by supplying hydraulic pressure to the continuously variable transmission, and a transmission ratio is changed,

the hydraulic control method is characterized in that,

comprises the following steps:

detecting the speed ratio by a speed ratio detection unit based on the respective rotation speeds of the drive pulley and the driven pulley while the hydraulic pressure is being supplied from a pump to each unit in the continuously variable transmission through a valve unit;

a command value determining unit that determines a command value of a shift pressure that is a hydraulic pressure supplied to the drive pulley and the driven pulley;

controlling the supply of the hydraulic pressure by controlling the valve portion by a valve control portion according to the command value; and

when it is expected that the supply of the hydraulic pressure is controlled by the valve control unit in accordance with the command value so that the lubrication pressure, which is the hydraulic pressure supplied to the endless transmission belt, is less than a threshold value, the command value changing unit changes the command value so that the lubrication pressure becomes equal to or greater than the threshold value.