JP2001330118A - Hydraulic control device for continuously variable transmission for vehicles - Google Patents

Abstract

(57) [Problem] To provide a hydraulic control device for a continuously variable transmission for a vehicle in which slippage of a power transmission member does not occur even when a hydraulic oil temperature is low. SOLUTION: A shift speed limiting means 96 limits the maximum shift speed of the belt-type continuously variable transmission 18 based on a hydraulic oil temperature T _OIL detected by an oil temperature sensor 78. Accordingly, the maximum value of the rate of change of the volume in the input side hydraulic cylinder 42c is limited, and the pressure drop due to the rate of change is suppressed.
The shortage of hydraulic oil in the inside is eliminated, and the slip of the power transmission belt (power transmission member) 48 is prevented. Further, there is no hindrance to the shift control operation within the range until the shift speed reaches the maximum value of the shift speed, and the shift control characteristics are suitably maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hydraulic control device for a continuously variable transmission for a vehicle, and more particularly, to preventing a power transmission member from slipping due to leakage of hydraulic oil in a hydraulic actuator for changing a gear ratio. It is about technology.

[0002]

2. Description of the Related Art A continuously variable transmission for a vehicle in which power is transmitted through a power transmission member pressed by a hydraulic actuator, and a stepless transmission is performed by controlling the supply and discharge of hydraulic oil to and from the hydraulic actuator. Machines are known. For example, a pair of input-side variable pulleys and output-side variable pulleys whose effective diameters are variable, a transmission belt wound around the input-side variable pulleys and the output-side variable pulleys to transmit power, This is a belt-type continuously variable transmission including an input-side hydraulic cylinder and an output-side hydraulic cylinder that change the V-groove width of the output-side variable pulley. Normally, a hydraulic control circuit is provided that uses hydraulic oil from a hydraulic pump rotationally driven by an engine as a base pressure, and the hydraulic oil in one of the input-side hydraulic cylinder and the output-side hydraulic cylinder is controlled by a shift control valve device. The transmission ratio is controlled by being supplied or discharged by the motor, and the working hydraulic pressure in the other is regulated by the belt tension control valve, so that the tension of the transmission belt is controlled as necessary and sufficiently according to the input torque and the transmission ratio. As a result, the transmission belt is prevented from slipping.

When hydraulic oil leaks from the hydraulic cylinder and the amount of the hydraulic oil increases as the temperature of the hydraulic oil increases, the pressing force of the power transmission member must be sufficient and sufficient, especially in the case of sudden shifting. In some cases, the pressing force becomes insufficient despite the execution of the control to be performed.
For example, in the case of a belt-type continuously variable transmission, despite the execution of control to make the tension of the transmission belt necessary and sufficient in accordance with the input torque and the gear ratio, the volume change in the hydraulic cylinder especially in the case of a sudden gear change. As a result, there is a possibility that the hydraulic oil runs short and the transmission belt slips.

[0004]

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. H11-141670, for example, when the feedback control is performed so that the gear ratio matches the target gear ratio, the operating oil temperature becomes lower. A technique for increasing the feedback gain as much as possible has been disclosed. However, such a technique is intended to solve the problem that the control operation for matching the gear ratio to the target gear ratio is made faster as the oil temperature becomes lower and the control operation becomes slower as the viscosity of the hydraulic oil increases. It is not possible to cope with insufficient pressing force of the power transmission member due to insufficient hydraulic oil in the hydraulic cylinder.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic control for a continuously variable transmission for a vehicle in which the power transmission member does not slip even when the operating oil temperature is high. It is to provide a device.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is to supply hydraulic oil pumped from a hydraulic pump to a hydraulic actuator or to supply hydraulic oil in the hydraulic actuator to the hydraulic oil. A hydraulic control device for a vehicle continuously variable transmission that performs a stepless shift by discharging, comprising: (a) an oil temperature sensor that detects a temperature of the hydraulic oil; and (b) an oil temperature sensor that detects the oil temperature. Shift speed limiting means for limiting the maximum shift speed of the continuously variable transmission based on the temperature of the operating oil.

[0007]

According to the above configuration, the maximum value of the shift speed of the continuously variable transmission is limited by the shift speed limiting means based on the temperature of the hydraulic oil detected by the oil temperature sensor. The maximum value of the rate of change of the hydraulic cylinder volume due to the above is limited, and the pressure drop caused by the rate of change is suppressed, so that the hydraulic oil shortage in the hydraulic cylinder is eliminated and the power transmission member is prevented from slipping. . Further, there is no hindrance to the shift control operation within the range until the shift speed reaches the maximum value of the shift speed, and the shift control characteristics are suitably maintained.

[0008]

In another preferred embodiment of the present invention, a predetermined relationship between at least one of the speed ratio of the continuously variable transmission and the temperature of the hydraulic oil and the maximum value of the shift speed is preferably determined based on a predetermined relationship. A shift speed maximum value determining means for determining a shift speed maximum value based on at least one of a gear ratio of a stepped transmission and a temperature of hydraulic oil detected by the oil temperature sensor. With this configuration, it is possible to obtain an appropriate maximum value of the shift speed that reflects at least one of the speed ratio of the continuously variable transmission and the temperature of the hydraulic oil. For example, in a belt-type continuously variable transmission, since the belt hook diameter of the variable pulley changes due to the change in the gear ratio, it is possible to cope with the fact that the torque capacity that can be held even when the clamping pressure on the transmission belt is the same is different. As a result, slippage of the transmission belt can be prevented, and deterioration of the shift speed can be appropriately reduced. The above relationship is set in advance so that the maximum value of the shift speed decreases as the temperature of the hydraulic oil increases, or the maximum value of the shift speed decreases as the gear ratio of the continuously variable transmission increases.

Preferably, the hydraulic pump is rotationally driven by an engine, and the shift speed limiting means is provided when the rotational speed of the hydraulic pump is within a predetermined low-speed rotation range. This is to limit the maximum value of the shift speed of the continuously variable transmission. With this configuration, the shift speed limiting means limits the maximum shift speed of the continuously variable transmission within a preset low-speed rotation range where the discharge capacity (discharge pressure) of the hydraulic pump is low. In the rotation range where the discharge capacity of the hydraulic cylinder is high and the amount of leakage from the hydraulic cylinder can be sufficiently compensated for, the maximum value of the transmission speed is not limited, and suitable transmission control can be obtained. Further, when the maximum value of the shift speed of the continuously variable transmission is limited within the low-speed rotation range of the hydraulic pump, it is in a low-speed running state in coasting or a high-speed gear stage where the engine rotation speed is relatively low,
Since a high shift speed is not so required, the shift control is not so hindered.

Preferably, the low-speed rotation range is a rotation range lower than a minimum discharge pressure holding rotation range of the hydraulic pump. With this configuration, in the minimum discharge pressure holding rotation range of the hydraulic pump, the discharge capacity of the hydraulic pump is high, and the maximum value of the shift speed is not limited, so that suitable shift control can be obtained.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a skeleton view of a power transmission device 10 including a vehicle belt type continuously variable transmission 18 to which a control device according to one embodiment of the present invention is applied. The power transmission device 10 is suitably employed, for example, in a laterally mounted FF (front engine / front drive) driven vehicle, and includes an engine 12 which is an internal combustion engine used as a power source for traveling. The output of the engine 12 is supplied from a torque converter 14 to a forward / reverse switching device 16 and a belt-type continuously variable transmission (C).
VT) 18, and transmitted to the differential gear device 22 via the reduction gear 20, and distributed to the left and right drive wheels 24 </ b> L and 24 </ b> R. The belt-type continuously variable transmission 18 is provided with left and right driving wheels (for example, front wheels) 24L,
It is provided in a power transmission path leading to 4R.

The above-mentioned torque converter 14 is used for the engine 1
The pump impeller 14p connected to the second crankshaft, the turbine impeller 14t connected to the forward / reverse switching device 16 via the turbine shaft 34, and a non-rotating member rotatably supported via a one-way clutch. And a fixed-wing wheel 14s for transmitting power via fluid. A lock-up clutch (direct coupling clutch) 26 for integrally connecting the pump impeller 14p and the turbine impeller 14t so as to be able to rotate integrally with each other is provided between the pump impeller 14p and the turbine impeller 14t. Is provided.

The forward / reverse switching device 16 is constituted by a double pinion type planetary gear device. The turbine shaft 34 of the torque converter 14 is connected to the sun gear 16 s, and the input shaft 36 of the belt type continuously variable transmission 18. Is carrier 1
6c. When the forward clutch 38 disposed between the carrier 16c and the sun gear 16s is engaged, the forward / reverse switching device 16 is integrally rotated, and the turbine shaft 34 is directly connected to the input shaft 36, and the forward / backward switching device 16 is moved in the forward direction. The driving force is transmitted to the driving wheels 24R and 24L. When the reverse brake 40 disposed between the ring gear 16r and the housing is engaged and the forward clutch 38 is released, the input shaft 36 is rotated in the reverse direction with respect to the turbine shaft 34, and is moved in the reverse direction. Drive force of the drive wheel 24
R, 24L.

The belt-type continuously variable transmission 18 includes an input-side variable pulley 4 provided on the input shaft 36 and having a variable effective diameter.
2, an output variable pulley 46 provided on the output shaft 44 and having a variable effective diameter, and a transmission belt 48 wound around the V groove of the variable pulleys 42 and 46. Transmission belt 48 and variable pulley 4 functioning as
Power transmission is performed via frictional force between the inner wall surfaces of the V-grooves 2 and 46. Variable pulleys 42, 46
Is provided with an input-side hydraulic cylinder 42c and an output-side hydraulic cylinder 46c for changing the width of each V-groove, that is, the hanging diameter of the transmission belt 48, and is supplied to or from the hydraulic cylinder 42c of the input-side variable pulley 42. The flow rate of the discharged hydraulic oil is controlled by the shift control valve device 50 (see FIG. 4) in the hydraulic control circuit 52, so that the V-groove widths of the two variable pulleys 42 and 46 change, and the transmission belt 48 is engaged. The diameter (effective diameter) is changed, and the speed ratio γ (= input-side rotation speed N _IN / output-side rotation speed N _OUT ) is continuously changed.

The hydraulic pressure P _B in the hydraulic cylinder 46c of the output-side variable pulley 46 corresponds to the squeezing pressure of the variable pulley 46 on the transmission belt 48 and the tension of the transmission belt 48, respectively. Since it is closely related to the tension, that is, the pressing force of the transmission belt 48 against the inner wall surfaces of the V-grooves of both the variable pulleys 42 and 46, it can also be called a belt tension control pressure, a belt clamping pressure control pressure, and a belt pressing force control pressure. In order to prevent the transmission belt 48 from slipping, the clamping pressure control valve 60 in the hydraulic control circuit 52 is
The pressure is regulated.

FIG. 2 is a partially cutaway view of the belt type continuously variable transmission 18 in order to explain the configuration thereof. The input-side variable pulley 42 is movable in the axial direction with respect to the input shaft 36 in a state where a V-groove is formed between the fixed rotary member 42f fixed to the input shaft 36 and the fixed rotary member 42f. A rotating body 42v non-rotatably mounted, and a cylinder body 42b fixed to the input shaft 36 and slidably fitted to the movable rotating body 42v,
The hydraulic cylinder 42c is constituted by a movable rotating body 42v functioning as a piston and a cylinder body 42b. The output side variable pulley 46 is connected to the output shaft 44.
Fixed rotating body 46f fixed to the fixed rotating body 46f
f, a movable rotator 46v attached to the output shaft 44 so as to be movable in the axial direction and not to rotate relative to the axis in a state where a V-groove is formed, and a movable rotator 46v fixed to the output shaft 44 and fixed to the output shaft 44. And a cylinder body 46b slidably fitted thereto, and the hydraulic cylinder 46c is constituted by the movable rotating body 46v functioning as a piston and the cylinder body 46b. These hydraulic cylinders 4
2c and 46c are designed to cause some leakage of hydraulic oil even though a seal member 47 for preventing leakage of hydraulic oil is provided at the sliding portion.

FIGS. 3 and 4 show examples of the hydraulic control circuit 52. FIG. 3 shows a circuit relating to the operation of adjusting the belt tension control pressure, and FIG. 4 shows a circuit relating to the speed ratio control. Each is shown. In FIG. 3, the oil tank 5
Hydraulic oil refluxed 6 is pumped by a hydraulic pump 54 driven by the engine 12, after the pressure is regulated to a line pressure P _L by a not-shown line pressure regulating valve, a linear solenoid valve 58 and clamping pressure control valve 60 Supplied as source pressure. The linear solenoid valve 58 includes an electronic control device 66
By excitation current (see FIG. 5) are continuously controlled by the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump 54 to generate a control pressure P _S of a size corresponding to the exciting current pinching It is supplied to the pressure control valve 60. Nipping pressure control valve 60
Generates a hydraulic pressure P _B that is increased as the control pressure P _S increases, and supplies the hydraulic pressure P _B to the hydraulic cylinder 46 c of the output-side variable pulley 46 so that the transmission belt 48 does not slip as much as possible. The clamping pressure on the transmission belt 48, that is, the tension of the transmission belt 48 is reduced. Its oil pressure P _B increases the frictional force between the accompanied in its raised and the belt clamping pressure or variable pulleys 42, 46 and the transmission belt 48.

[0019] The linear solenoid valve 58, while the oil chamber 58a of the control pressure P _S which is output therefrom at ON cutback valve 62 is supplied is provided, the cut-back valve 62 OFF times, to the oil chamber 58a are adapted to control pressure P _S supply is cut off by the oil chamber 58a of are opened to the atmosphere of, so that the time on the cut-back valve 62 characteristic of the control pressure P _S than when off is switched to the low-pressure side It has become. When the lock-up clutch 26 of the torque converter 14 is turned on (engaged), the cutback valve 62 is turned on by supplying a signal pressure P _ON from a solenoid valve (not shown).

In FIG. 4, the transmission control valve device 50
Is an upshift control valve 50 _U that exclusively supplies the hydraulic oil of the line pressure P _L to the hydraulic cylinder 42 c of the input-side variable pulley 42 and controls the upshift speed by controlling the hydraulic oil flow rate; and The hydraulic cylinder 42
The downshift control valve 50D controls the downshift speed by controlling the flow rate of the hydraulic oil discharged from the control valve _50D.
It is composed of This up-shift control valve 50 _U
A spool valve 50 _Uv that opens and closes between a line oil passage _L that guides the line pressure P _L and the input side hydraulic cylinder 42 c, and a spring 50 that urges the spool valve 50 _Uv in the valve closing direction.
_Us and a control oil chamber 50 _Uc for guiding the control pressure output from the up-side solenoid valve 64 _U. Further, downshift control valve 50 _D is input hydraulic cylinder and drain oil passage D 42
a spool valve element 50 _Dv that opens and closes between is c, a spring 50 for biasing the spool valve element 50 _Dv in the closing direction
And _ds, and a control hydraulic chamber 50 _Dc for guiding a control pressure that is output from the down side the solenoid valve 64 _D. The up-side electromagnetic valve 64 _U and the down-side electromagnetic valve 64 _D, the electronic control unit 6
The control pressure continuously changed by the duty drive by the control unit 6 is supplied to the control oil chamber 50 _Uc and the control oil chamber 50 _Dc, and the speed ratio γ of the belt-type continuously variable transmission 18 is continuously increased to the up side and the down side. Change. Note that the shift-down control valve 50 _D, the line oil passage L and the input-side hydraulic cylinder 42c in the closed position of the spool valve element 50 _Dv
And a flow passage 61 having a small flow cross-sectional area is formed between the transmission gear 61 and the speed change ratio γ when the upshift control valve _50U and the downshift control valve _50D are both closed. In order to prevent this, restrict from line oil passage L
3. The working oil is slightly supplied through the one-way valve 65 and the flow passage 61. The input-side hydraulic cylinder 42c and the output-side hydraulic cylinder 46c apply a biased load to the rotation axis thereof. This is because there is a slight leak.

The electronic control unit 66 shown in FIG.
The operation position detection sensor 68 for detecting the operation position of the
Operating position P_SHSignal indicating the ignition key
Ignition from the operated ignition switch 69
Signal indicating the on-key operation, the opening of the throttle valve 70
Of the accelerator pedal 71 that changes the_ACCDetect
Accelerator opening θ from the accelerator operation amount sensor 72_ACC
, The rotation speed N of the engine 12_ETo detect
The rotation speed N from the engine rotation speed sensor 73_EA sign of
No., vehicle speed V (specifically, rotation speed N of output shaft 44)_OUT)
Speed sensor (output side rotation speed sensor) 74
Signal representing the vehicle speed V, the input shaft rotation speed N of the input shaft 36.
_INInput shaft rotation from the input side rotational speed sensor 76 that detects
Rolling speed N _IN, The power transmission 10 or bell
Oil temperature T in the automatic transmission 18_OILDetect the oil
Hydraulic oil temperature T from temperature sensor 78_OILSignal representing the output
Pressure P of the hydraulic cylinder 46c of the side variable pulley 46_Bsand
That is, the actual belt clamping pressure control pressure P_BDetecting the pressure sensor
Its hydraulic pressure P from the_BSignals representing the
It is supposed to be.

The electronic control unit 66 includes a CPU, an RO,
M, a RAM, a so-called microcomputer including an input / output interface, and the like.
By performing signal processing in accordance with a program stored in the ROM in advance while utilizing the temporary storage function, the shift control and the clamping pressure control of the continuously variable transmission 18 are performed.
Specifically, in the shift control, for example, an accelerator operation amount, that is, an accelerator opening degree θ representing an actual driver's required output amount is obtained from a relationship (map) stored in advance shown in FIG.
Calculates a target rotational speed N _IN ^T based on _{AC C} (%) and the vehicle speed V (corresponding to the output rotational speed N _OUT), the actual input rotational speed N _IN coincides with the target rotational speed N _IN ^T By operating the transmission control valve device 50 as described above, the flow rate of the hydraulic oil supplied into the hydraulic cylinder 42c of the input-side variable pulley 42 or the hydraulic oil discharged from the hydraulic cylinder 42c is controlled. FIG.
Is a relationship determined in advance for operating the output and the fuel economy along an optimal curve at which the fuel efficiency is optimal, and the γ
_max is the maximum speed ratio, and γ _min is the minimum speed ratio.

In the belt squeezing pressure control, the electronic control unit 66 uses a predetermined relationship (map) to obtain a necessary and sufficient necessary oil pressure (a target oil pressure corresponding to an ideal belt squeezing pressure). A belt clamping pressure control pressure (target value) is calculated based on the accelerator operation amount θ _ACC corresponding to the actual input torque T _IN or the transmission torque of the belt type continuously variable transmission 18 and the actual gear ratio γ, and the belt clamping is performed. The squeezing pressure control valve 60 in the hydraulic control circuit 52 is adjusted to obtain a pressure control pressure.

FIG. 7 is a functional block diagram for explaining a main part of the control function of the electronic control unit 66, that is, belt clamping pressure control. In FIG. 7, the shift control unit 88 determines the actual accelerator opening θ _ACC (%) during traveling of the vehicle from, for example, a relationship (map) stored in advance shown in FIG.
And the vehicle speed V to calculate the target rotational speed N _IN ^T based on (corresponding to the output rotational speed N _OUT), the actual input rotational speed N _IN is the shift control valve so as to match the target rotational speed N _IN ^T by executing the determined feedback control to operate in its drive duty ratio D of the up-shift control valve 50 _U or down shift control valve 50 _D of the drive duty ratio D (%) of the apparatus 50, the input side variably pulley 42 It controls the flow rate of hydraulic oil supplied into the hydraulic cylinder 42c or hydraulic oil discharged from the input side hydraulic cylinder 42c. The drive duty ratio D and the shift speed of the belt-type continuously variable transmission 18 have, for example, a relationship shown in FIG.

The gear ratio detecting means 90 divides the input shaft rotation speed N _IN from the input side rotation speed sensor 76 by the output shaft rotation speed N _OUT detected by the vehicle speed sensor 74, or by a sensor (not shown). The speed ratio γ of the belt-type continuously variable transmission 18 is detected based on the detected V-groove width of the input-side variable pulley 42. The pump discharge capacity determination means 92 determines whether the rotational speed of the hydraulic pump 54, which is rotationally driven by the engine 12, has fallen below a preset minimum discharge pressure holding rotational range, that is, whether the rotational speed is within the low speed rotational range. determining based on the rotational speed N _E. The hydraulic pump 54 is, for example, a gear type pump. As shown in FIG. 9, for example, in the minimum discharge pressure holding rotation range where the drive rotation speed exceeds a boundary rotation speed of, for example, about 1000 rpm, the discharge pressure P _OIL is stable. It becomes substantially constant to a value greater than a minimum discharge pressure P _min, and a characteristic to decrease more quickly than the minimum discharge pressure holding the discharge pressure of the rotation range becomes the low speed rotation region to fall below the minimum discharge pressure P _min. Therefore, the pump discharge capability determination unit 92 determines whether the rotational speed of the hydraulic pump 54 corresponding to the engine rotational speed N _E falls below the boundary speed.

The shift speed maximum value determining means 94 determines the speed ratio γ of the belt-type continuously variable transmission 18 and the operating oil temperature T _OIL
The hydraulic fluid detected by the speed ratio γ of the belt-type continuously variable transmission 18 and the oil temperature sensor 78 from a preset relationship between the speed ratio γ and the maximum duty ratio A corresponding to the maximum value. The maximum duty ratio A corresponding to the maximum value of the shift speed is determined based on the temperature of T _OIL . The above relationship is such that the maximum duty ratio A corresponding to the maximum value of the shift speed is limited (decreased) as the temperature T _OIL of the hydraulic oil increases, and the belt-type continuously variable transmission 18
Is set in advance so that the maximum duty ratio A corresponding to the maximum value of the shift speed decreases as the speed change ratio γ of the shift speed increases. FIG. 10 shows a map that is an example of the above relationship.

The shift speed limiting means 96 includes an oil temperature sensor 78
The maximum value of the shift speed of the belt type CVT 18 is limited to a low level on the basis of the temperature T _{OI L} of hydraulic oil detected by.
That is, the maximum duty ratio A corresponding to the maximum value of the shift speed determined according to the shift ratio γ of the belt-type continuously variable transmission 18 and the hydraulic oil temperature T _OIL from the relationship of FIG. , The up-shift control valve 50 _U (up-side solenoid valve 64) controlled by the shift control means 88.
_U ) or down-shift control valve _50D (down-side solenoid valve 6)
The maximum value of the speed change speed of the belt-type continuously variable transmission 18 is limited by keeping the actual drive duty ratio D of 4 _D ) from exceeding. Further, the speed change speed limiting means 96 includes:
When the pump discharge capacity determining means 92 does not determine that the rotation speed of the hydraulic pump 54 rotationally driven by the engine 12 has fallen below a preset minimum discharge pressure holding rotation range, that is, when the rotation speed is within the minimum discharge pressure holding rotation range, the belt type is used. The maximum value of the shift speed of the continuously variable transmission 18 is not limited, but if it is determined that the speed has fallen below, the above-described control for limiting the maximum value of the shift speed is executed.

FIG. 11 is a flowchart for explaining a main part of the control operation of the electronic control unit 66, which is repeatedly executed at a predetermined cycle time, for example, at a cycle of several tens of milliseconds. 11, steps corresponding to the pump discharge capability determination unit 92 (hereinafter, omitted step) in SA1, the lowest discharge pressure holding and rotating the engine rotational speed N _E corresponding to the rotational speed of the hydraulic pump 54 is set in advance The rotation speed N _L corresponding to the lower limit of the range, that is, the boundary value
Is determined. If the determination at SA1 is denied, this routine is terminated. If the determination is affirmed, the operating oil temperature T _OIL detected by the oil temperature sensor 78 at SA2 is read. Next, in SA3 corresponding to the speed ratio detecting means 90, the actual speed ratio γ of the belt type continuously variable transmission 18 is calculated.

Subsequently, the shift speed maximum value determining means 94
In SA4 corresponding to the maximum duty ratio corresponding to the limit value of the shift speed, that is, the maximum value, based on the actual gear ratio γ of the belt-type continuously variable transmission 18 and the operating oil temperature T _OIL from the relationship shown in FIG. The ratio A is determined. Next, at SA5, whether actual drive duty ratio D of the shift control unit upshift control valve 50 is controlled by a 88 _U or down shift control valve 50 _D has exceeded the maximum duty ratio A is determined. If the determination at SA5 is negative, this routine is terminated, so that the maximum value of the shift speed is not limited at all in the shift control by the shift control means 88. However, if the determination at SA5 is affirmative, the actual driving duty ratio D is the maximum duty ratio A of the shift control means upshift control valve 50 is controlled by a 88 _U or down shift control valve 50 _D in SA6 By the replacement, the maximum value of the drive duty ratio D is limited to the maximum duty ratio A, and the maximum value of the shift speed is set to a value corresponding to the maximum duty ratio A. In the present embodiment, SA5 and SA6 correspond to the shift speed limiting means 96.

As described above, according to the hydraulic control apparatus of this embodiment, the temperature T of the operating oil detected by the oil temperature sensor 78 by the shift speed limiting means 96 (SA5, SA6).
_Since the maximum value of the shift speed of the belt-type continuously variable transmission 18 is limited based on the _OIL , the maximum value of the change rate of the volume in the input side hydraulic cylinder 42c due to the shift is limited, and the maximum value is caused by the change rate. As a result, the shortage of hydraulic oil in the input side hydraulic cylinder 42c is eliminated, and slippage of the transmission belt (power transmission member) 48 is prevented. Further, there is no hindrance to the shift control operation within the range until the shift speed reaches the maximum value of the shift speed, and the shift control characteristics are suitably maintained.

The hydraulic control device according to the present embodiment includes a gear ratio γ of the belt-type continuously variable transmission 18 and a temperature T of the hydraulic oil.
Maximum duty ratio A corresponding to the maximum value of _OIL and shift speed
From the preset relationship (FIG. 10) between the maximum value of the shift speed based on the gear ratio γ of the belt-type continuously variable transmission 18 and the temperature T _OIL of the hydraulic oil detected by the oil temperature sensor 78. Speed maximum value determining means 94 (SA
4), the belt-type continuously variable transmission 1
8 and the maximum value of the appropriate shift speed reflected by the operating oil temperature T _OIL detected by the oil temperature sensor 78. For example, in the belt type continuously variable transmission 18, the input side variable pulley 42
Also, since the belt hanging diameter of the output-side variable pulley 46 changes, it is possible to cope with the fact that the torque capacity that can be received is different even if the clamping pressure on the transmission belt 48 is the same, thereby preventing the transmission belt 48 from slipping. In addition, the deterioration of the shift speed can be appropriately reduced.

Further, in this embodiment, the shift speed limiting means 9
6 (SA5, SA6) limits the maximum value of the shift speed of the belt-type continuously variable transmission 18 when the rotation speed of the hydraulic pump 54 that is driven to rotate by the engine 12 is within a preset low-speed rotation range. Therefore, the maximum value of the shift speed of the belt-type continuously variable transmission 18 is limited within a predetermined low-speed rotation range where the discharge capacity (discharge pressure) of the hydraulic pump 54 is low. Is high, and the maximum value of the shift speed is not limited in a rotation range in which the amount of leakage from the hydraulic cylinders 42c and 46c can be sufficiently compensated, so that suitable shift control can be obtained. Further, the belt-type continuously variable transmission 18
If the maximum value of the shift speed of is limited to a low speed state at a relatively low coasting and high-speed gear position the engine rotational speed N _E, since the high shift speed is not necessary so, the shift control There is not much trouble.

In this embodiment, the low-speed rotation range is:
For example, in the characteristic of the hydraulic pump 54 shown in FIG. 9, since the rotation range is lower than the minimum discharge pressure holding rotation region in which the minimum discharge pressure P _min is held, the hydraulic pump 54 Discharge capacity is high,
Since the maximum value of the shift speed is not limited, a suitable shift control can be obtained.

While one embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, in the above embodiment, a pair of variable pulleys 42, 4 around which a transmission belt 48 is wound
Although the so-called belt-type continuously variable transmission 18 having the gear 6 is used, the present invention can be applied to other continuously variable transmissions such as a toroidal-type continuously variable transmission. In short, the gear ratio is changed by changing the contact position of the roller-type power transmission member interposed between the input-side rotator and the output-side rotator in a pressed state with respect to the input-side rotator and the output-side rotator. What is necessary is just a continuously variable transmission that can be changed steplessly.

Further, in the above-described embodiment, the limitation of the maximum value of the shift speed by the shift speed limiting means 96 has been performed for the upshift and the downshift. The maximum value of the shift speed may be limited by the shift speed limiting means 96 only for a downshift that is likely to cause a shortage of hydraulic oil when the shift speed increases due to discharge of the hydraulic oil.

The relationship shown in FIG. 10 is that the speed ratio γ of the belt type continuously variable transmission 18 and the hydraulic oil temperature T
The relationship between _OIL and the limit value of the speed change speed, that is, the maximum duty ratio A corresponding to the maximum value, has been described.
And the relationship between at least one of the hydraulic oil temperature T _OIL and the shift speed limit value. By using such a relationship, an appropriate maximum value of the shift speed reflecting at least one of the speed ratio γ of the belt-type continuously variable transmission 18 and the temperature T _OIL of the hydraulic oil is obtained.

Although the embodiment of the present invention has been described in detail with reference to the drawings, this is merely an embodiment,
The present invention can be implemented in various modified and improved aspects based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram of a vehicle power transmission device to which a control device according to an embodiment of the present invention is applied.

FIG. 2 is a partially cutaway view for explaining in detail the configuration of the belt-type continuously variable transmission shown in FIG.

3 is a diagram showing a main part of a hydraulic control circuit for controlling a belt-type continuously variable transmission in the vehicle power transmission device shown in FIG. 1, and is a diagram showing a portion related to belt tension control.

FIG. 4 is a diagram showing a main part of a hydraulic control circuit for controlling a belt-type continuously variable transmission in the vehicle power transmission device of FIG. 1, and is a diagram showing a portion related to speed ratio control.

FIG. 5 is a diagram briefly explaining an electrical configuration of the control device of the embodiment of FIG. 1;

6 is a diagram showing a relationship stored in advance used for determining a target rotation speed in a gear ratio control executed by the electronic control device of FIG. 5;

FIG. 7 is a functional block diagram illustrating a main part of a control function of the electronic control device of FIG. 5;

8 is a diagram showing a drive duty ratio D of an up-shift control valve or a down-shift control valve in the belt-type continuously variable transmission shown in FIG. 1;
FIG. 4 is a diagram showing a relationship between the speed and a shift speed.

FIG. 9 is a view showing a discharge pressure characteristic of a hydraulic pump rotated and driven by the engine of FIG. 1;

FIG. 10 is a table showing a relationship used for determining the maximum duty ratio corresponding to the maximum value of the shift speed in the shift speed maximum value determining means of FIG. 7;

11 is a time chart for explaining a main part of a control operation of the electronic control device of FIG. 5, that is, a shift speed limiting routine.

[Explanation of symbols]

18: Belt-type continuously variable transmission (continuously variable transmission) 42c: Input side hydraulic actuator (hydraulic actuator) 48: Transmission belt (power transmission member) 54: Hydraulic pump 78: Oil temperature sensor 96: Shift speed limiting means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daisuke Inoue 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Katsumi Kawano 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation ( 72) Inventor Koji Taniguchi 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (reference) 3J552 MA07 MA12 MA26 NA01 NB01 PA12 QA24C QB04 RA29 RC03 SA32 SA36 SB21 TA01 TB11 TB13 VA32Y VA37Z VA48W VA53W VA62Z VA74W VB01Z VC01 VD02Z VD18Z

Claims (4)

[Claims] 1. A hydraulic control device for a continuously variable transmission for a vehicle that performs a stepless speed change by supplying hydraulic oil pressure-fed from a hydraulic pump to a hydraulic actuator or discharging hydraulic oil from the hydraulic actuator. An oil temperature sensor for detecting a temperature of the hydraulic oil, and a shift speed limiting means for limiting a maximum shift speed of the continuously variable transmission based on a temperature of the hydraulic oil detected by the oil temperature sensor And a hydraulic control device for a continuously variable transmission for a vehicle. 2. The speed ratio of the continuously variable transmission and the oil based on a predetermined relationship between at least one of the speed ratio of the continuously variable transmission and the temperature of the hydraulic oil and the maximum value of the speed. 2. The hydraulic control apparatus for a continuously variable transmission for a vehicle according to claim 1, further comprising a shift speed maximum value determining means for determining a maximum value of the shift speed based on at least one of the temperatures of the hydraulic oil detected by a temperature sensor. . 3. The continuously variable transmission according to claim 1, wherein the hydraulic pump is rotationally driven by an engine, and the shift speed limiting means is provided when the rotational speed of the hydraulic pump is within a predetermined low-speed rotation range. 3. The hydraulic control device for a continuously variable transmission for a vehicle according to claim 1, wherein the maximum value of the shift speed of the vehicle is limited. 4. The hydraulic control apparatus for a continuously variable transmission for a vehicle according to claim 3, wherein the low speed rotation range is a rotation range lower than a minimum discharge pressure holding rotation range of the hydraulic pump.