JPS6241462A - Hydraulic control device in belt type stepless speed change gear - Google Patents

Abstract

PURPOSE:To obtain a large thrust differential, by controlling the hydraulic pressures of hydraulic actuators provided to input and output shafts, independently from each other, with the use of a pair of pressure adjusting valves. CONSTITUTION:There are provided a pair of pressure adjusting valves 44, 52 for adjusting the hydraulic pressures in hydraulic actuators 26, 28. Further, the pressures in the hydraulic actuators 26, 28 are determined in order to obtain a desired speed and desired input shaft torque of a stepless speed change gear, in accordance with a given relationship. Further, control means 46, 48, 72 control the pressure adjusting valves 44, 45 to set the hydraulic pressures in the hydraulic actuators 26, 28 to the required pressures. With this arrangement, a large thrust differential may be obtained in comparison with conventional technique which uses a single pressure adjusting valve.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a hydraulic control device for a belt-type continuously variable transmission, and more particularly to a technique that allows a high speed ratio change rate and high control accuracy for the tension of a transmission belt.

Conventional technology An input shaft and an output shaft, a pair of variable pulleys with variable effective diameters provided on the input shaft and the output shaft, respectively;
A belt comprising: a transmission belt wound between the variable pulleys; and a pair of hydraulic actuators provided on the input shaft and the output shaft, respectively, for applying thrust to the variable pulley in a direction to reduce the groove width. In the continuously variable transmission, there is a hydraulic control device that changes the tension of the transmission belt and the speed ratio of the input shaft and output shaft by changing the thrust of the hydraulic actuator. For example, there is a device described in Japanese Patent Application Laid-Open No. 52-98861. In such conventional devices, one line hydraulic pressure regulated by a single pressure regulating valve is supplied exclusively to the hydraulic actuator on the output shaft side that controls the tension of the transmission belt, while the flow control valve controls the line hydraulic pressure. The speed ratio is changed by supplying the hydraulic oil to the hydraulic actuator on the input shaft side or discharging the hydraulic oil in the hydraulic actuator. Normally, in order to obtain a wide speed ratio change range, a predetermined difference in thrust between the two hydraulic actuators is required, and in conventional devices, the thrust can be increased by increasing the pressure receiving area of the hydraulic actuator on the input shaft side. It secured the difference.

Problems to be Solved by the Invention However, increasing the pressure receiving area of one hydraulic actuator is limited by the space allowed for the belt-type continuously variable transmission, so it is difficult to create a sufficient thrust difference. Even if it is possible to increase the pressure receiving area of one hydraulic actuator, the amount of hydraulic oil flowing into or flowing out of that hydraulic actuator will increase, so the speed ratio will increase. A sufficient rate of change could not be obtained.

In addition, in such conventional devices, the hydraulic actuator on the output shaft side exclusively adjusts the tension of the transmission belt regardless of the operating state of the belt type continuously variable transmission. This is a region where the pressure in the hydraulic actuator on the output shaft side to maintain the tension of the transmission belt decreases below the required value when changing the speed ratio by discharging the belt, resulting in a decrease in the accuracy of controlling the tension of the transmission belt. It is inevitable that this will occur. For this reason, in order to prevent the transmission belt from slipping in such areas, it is necessary to set the line oil pressure, which controls the tension of the transmission belt, to a high value in advance, allowing for a margin, so that the power of the belt-type continuously variable transmission is reduced. There was a disadvantage that the transmission efficiency decreased.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
Its gist is an input shaft, an output shaft, and a pair of variable pulleys with variable effective diameters provided on the input shaft and output shaft, respectively.

A transmission belt wound between the variable pulleys, and a pair of hydraulic actuators provided on the input shaft and the output shaft, respectively, for applying a thrust to the variable pulley in a direction to reduce the groove width, A hydraulic control device for a belt type continuously variable transmission that changes the tension of the transmission belt and the speed ratio of the input shaft and the output shaft by changing the thrust of the hydraulic actuator, the device comprising: (2) required hydraulic pressure in the pair of hydraulic actuators to obtain the target speed ratio and target input shaft torque of the continuously variable transmission from predetermined relationships; and control means for controlling the pressure regulating valves so that the hydraulic pressure in the hydraulic actuator becomes the required hydraulic pressure.

In this manner, the working oil pressure in the hydraulic actuators provided on the input shaft and the output shaft are independently controlled by the pair of pressure regulating valves, and the target of the continuously variable transmission is controlled by the control means. A required oil pressure in the hydraulic actuator to obtain the i degree ratio and target input shaft torque is determined, and each of the pressure regulating valves is controlled so that the oil pressure in the hydraulic actuator becomes the required oil pressure.

Effects of the Invention As a result, the hydraulic pressure in both hydraulic actuators is changed independently, and as a result, the pressure receiving area of both hydraulic actuators is increased compared to a conventional device that uses hydraulic pressure regulated by a single pressure regulating valve. A large ffI force difference can be generated without creating a difference, and the speed ratio can be changed quickly.

In addition, since the hydraulic pressure in both hydraulic actuators can be controlled independently, the hydraulic pressure in the input shaft side or output shaft side hydraulic actuator can be changed to control the transmission belt tension depending on the operating status of the belt type continuously variable transmission. can be done.

For this reason, it is possible to increase the power transmission efficiency of a belt-type continuously variable transmission compared to the conventional case in which hydraulic pressure with a margin value set in advance is applied exclusively to the output shaft side hydraulic actuator for controlling the tension of the transmission belt. I can do it.

The pressure regulating valve is preferably provided in series between a hydraulic pressure source and a drain, and the control means controls the respective hydraulic pressures regulated by the pressure regulating valves to one or the other of the hydraulic actuators. Includes a switching valve that supplies the In such a case, a common oil pump can be used to output two types of hydraulic pressure through pressure regulating valves.

Further, the switching valve preferably has a neutral position, and in the neutral position, oil passages that respectively guide the oil pressure regulated by the pressure regulating valve to the hydraulic pressure actuator are connected to each other, and one of the oil passages is connected to the other oil passages. and a hydraulic actuator connected to one of the oil passages.

Preferably, the control means is configured to control the speed ratio change speed by changing the oil pressure in the hydraulic actuator from the required oil pressure in the process of changing the speed ratio of the continuously variable transmission. Ru. In such a case, since the speed ratio change rate is controlled as necessary, there is an advantage that the speed ratio can be changed quickly and natural acceleration can be obtained.

In addition, in the process of changing the speed ratio of the continuously variable transmission, the control means determines that the thrust difference of the variable pulley is greater than the thrust difference at the target speed ratio, based on the difference between the actual speed ratio and the target speed ratio. The speed ratio change speed is controlled by controlling at least one of the pressure regulating valves so that the speed ratio increases.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, the rotation of the engine 10 is controlled by the clutch 12.
It is transmitted to the belt-type continuously variable transmission 14 via the belt-type continuously variable transmission 14, and after being continuously changed in speed in the belt-type continuously variable transmission 14, it is transmitted to the drive wheels via a differential device (not shown) or the like. There is. The belt-type continuously variable transmission 14 includes a pair of input shafts 16 and an output shaft 18 that are parallel to each other, and the input shaft 1
A pair of variable pulleys 20 and 22 with variable effective diameters are provided on the input shaft 16 and the output shaft 18, respectively, a transmission belt 24 is wound between the variable pulleys 20 and 22, and A pair of hydraulic cylinders 26 and 28 are provided, respectively, to apply thrust to the variable pulleys 20 and 22 in a direction to reduce the V-groove width. The variable pulleys 20 and 22 are fixed to fixed rotating bodies 30 and 32 fixed to the input shaft 16 and the output shaft 18, respectively, and fixed to the input shaft 16 and the output shaft 18 so as to be non-rotatable and movable in the axial direction. It consists of movable rotating bodies 34 and 36 which form grooves between them and rotating bodies 30 and 32. The hydraulic cylinders 26 and 28 function as hydraulic actuators that drive the movable rotating bodies 34 and 36.

The oil pump 38 is driven by the engine 10 or an electric motor (not shown), and is driven by the oil tank 40.
The hydraulic oil returned to the inside is passed through the first line oil passage 42 to the first
It is force-fed to the pressure control servo valve 44 and the electromagnetic switching valve 46. The first pressure control servo valve 44 normally controls the first line oil by causing the hydraulic oil in the first line oil passage 42 to flow out to the second line oil passage 50 in accordance with a signal from a controller 48 configured by a microcomputer. road 42
The first line oil pressure P7!1 within the line is regulated. The second pressure control servo valve 52 is provided between the second line oil passage 50 and the return oil passage 54, and supplies the hydraulic oil in the second line oil passage 50 to the return oil passage 54 according to a signal from the controller 48. The second line oil pressure PI! in the second line oil passage 50 is caused to flow out to the second line oil pressure PI! Adjust the pressure of 2. The electromagnetic switching valve 46 has a position where the first line oil passage communicates with the input side hydraulic cylinder 26 and a second line oil passage 50 with the output side hydraulic cylinder 28, and a position where the first line oil passage 42 communicates with the output side hydraulic cylinder 26. The first line oil passage 50 can be selectively switched to a position in which the first line oil passage 50 is communicated with the side hydraulic cylinder 28 and the second line oil passage 50 is communicated with the input side hydraulic cylinder 26 according to a signal from the controller 48. The hydraulic pressure P7!1 and the second line hydraulic pressure P12 are supplied to the input side hydraulic cylinder 26 and the output side hydraulic cylinder 28, and are also supplied to the output side hydraulic cylinder 28 and the input side hydraulic cylinder 26.

The controller 48 receives a signal from a sensor (not shown) representing the required load of the vehicle, such as a signal θT14 representing the throttle valve opening or a signal representing the accelerator operation amount, a signal representing the vehicle speed, and a rotational speed N of the engine 10. signal, and the actual rotational speed N i of the input shaft 16 and the rotational speed N of the output shaft 18 of the belt-type continuously variable transmission 14 . The controller 48 processes the input signals according to a program stored in advance in its storage device, and controls the first pressure control servo valve 44, the second pressure control servo valve 52, and the electromagnetic control servo valve 52. A drive signal is output to the switching valve 46.

Next, the operation of the hydraulic control device configured as described above will be explained according to the flowchart shown in FIG.

First, step S81 is executed, and the throttle valve opening θTl, the input shaft rotational speed N in, and the output shaft rotational speed N
. ut is read, and step S82 is executed to calculate the speed ratio e (=N, t/Ni, .). Next, step SS3 is executed, and the target speed ratio e1 is determined based on the throttle valve opening θTll or it and the vehicle speed V from a pre-stored relationship, and the throttle valve opening is determined from other pre-stored relationships. θ
TH and the rotational speed N of the engine 10. That is, the target input shaft torque T8 is determined from the input shaft rotational speed N=n. The relationship for determining the target speed ratio e11 is determined in advance so that the engine 10 operates along its minimum fuel efficiency curve, and is stored in advance in the form of a data map or a functional equation. Such a relationship can be seen, for example, in Japanese Patent Application Laid-Open No. 57-67362, which the present applicant previously filed.
It is similar to that shown in FIG. 3 of the publication. In addition, the relationship for determining the target input shaft torque T'' is the engine 1
In order to transmit the actual output shaft torque of 0 (the input shaft torque transmitted to the input shaft 16) to the output shaft 18, the tension of the transmission belt 24, that is, the narrowing pressure applied to the transmission belt 24, is set within a range where no slipping occurs. This is necessary and sufficient to increase the power transmission efficiency of the belt type continuously variable transmission 14 as much as possible, and the target input shaft torque T1 is the actual output torque of the engine 10, in other words, the belt type continuously variable transmission 14. This indicates the maximum value (transmission capacity) of torque that the gear transmission 14 should transmit. Such a relationship is, for example, similar to that described in FIG. 2 of Japanese Patent Application Laid-Open No. 57-67362, which the present applicant previously filed, and is stored in the ROM in advance in the form of a data map or a functional formula. ing.

In step SS4, the target speed ratio e8 and the target input shaft torque T
1, the pressure P in the hydraulic cylinder 26 on the input side,
7 and the oil pressure P in the output side hydraulic cylinder 28. ut is determined. That is, in step SS4, the first line oil pressure PAL to be regulated by the first pressure control servo valve 44,
The second line oil pressure P12 to be regulated by the second pressure control servo valve 52 is determined, and these oil pressures are the necessary oil pressures necessary to obtain the target speed ratio e''' and the target input shaft torque T8. In step SS5, the oil pressure P,7 in the input side hydraulic cylinder 26 obtained in step SS4 and the oil pressure P in the output side hydraulic cylinder 28 are calculated.
If p is larger than Pout, step SS6 is executed and the electromagnetic switching valve 46 is brought into the non-operating state as shown in FIG. That is, in this state, the solenoid of the electromagnetic switching valve 46 is de-energized.

Then, step SS7 is executed to determine the basic control voltage (2) to be supplied to the first pressure control servo valve 44 and the second pressure control servo valve 52 for obtaining the required oil pressure. 1 and V. 2 is determined according to the following equations (1) and (2), and in step SS8, the basic control voltage is corrected to improve the speed ratio change speed, and the control voltage 1 and Vz are determined according to the following equation ( Calculated according to 3) and (4).

■. I"kI ' Pi, 1 ... (1) VO2
= kz ・Po-t'...(21However, k
, 2 is a constant.

V, -V. , +K (e” −e) −−−(
3) Vz =Voz K'(e" e)
...(4) However, K and ni' are constants.

On the other hand, if it is determined in step SS5 that the oil pressure P, 7 in the input side hydraulic cylinder 26 is smaller than the oil pressure P 6uL in the output side hydraulic cylinder 28, step 5SIO is executed and the electromagnetic switching valve 46 is The solenoid is energized, and the first line oil passage 42 is connected to the output side hydraulic cylinder 2.
8, and the second line oil passage 50 is also communicated with the input hydraulic cylinder 26. Then, step 5Sll is executed, and the basic control voltage v0. and V. 2 is determined according to the following equations (5) and (6), and step 5S12 is executed to determine the control voltage v
I and Vz are determined according to the following equations (7) and (8).

V01=1 ・PouL ・ ・ ・ ・ ・
(5) Voz=kz ・Pin +
HH+ 16) V+ = Vo+ K' (e”
e) ・・(7)Vz −VO2+K
(e'' e) '' (8) The above step 5SII and step 5S12 are performed when the electromagnetic switching valve 46
Since the pressure regulating valves for regulating the working pressure in the hydraulic cylinders 26 and 28 are connected in reverse, the control formula is reversed compared to the cases of steps S, S7 and SS8.

The control voltages V1 and (2) determined as above are outputted when step SS9 is executed, and the oil pressures in the hydraulic cylinders 26 and 28 are controlled to the required oil pressure.

As described above, according to the present embodiment, the controller 48 and the electromagnetic switching valve 46 constitute the control means, and the hydraulic pressure in both the hydraulic cylinders 26 and 28 is controlled by the first pressure control servo, each functioning as a pressure regulating valve. Because the pressure is regulated independently by the valve 44 and the second pressure control servo valve 52, both hydraulic cylinders 26 and 28 have a pressure receiving area compared to conventional systems that use line hydraulic pressure regulated by a single pressure regulating valve. A large thrust difference can be generated without creating a difference, and the speed ratio can be changed quickly.

Further, since the oil pressure in both hydraulic cylinders 26 and 28 is individually controlled by the first pressure control servo valve 44 and the second pressure control servo valve 52, the belt type continuously variable transmission 14
The oil pressure in the input side hydraulic cylinder 26 and the output side hydraulic cylinder 28 can be changed in order to control the tension of the transmission belt 24 according to the operating state of the transmission belt 24 . For this reason, compared to the conventional case in which hydraulic pressure with a margin in advance is applied exclusively to the output shaft side hydraulic actuator for controlling the tension of the transmission belt, it is no longer necessary to apply hydraulic pressure with a margin in mind. Therefore, the power transmission efficiency of the belt type continuously variable transmission 14 can be improved.

Further, according to the present embodiment, the basic control voltage V for obtaining the required oil pressure. I and v02 have a deviation from the target value (e”-e
), both sleeve pressure cylinders 26.
Since the thrust difference of 28 is increased transiently, the target value e"%T" can be obtained more quickly.

Next, another embodiment of the present invention will be described. In the following description, parts common to the above-described embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4, an oil pump 6 pumps hydraulic oil to an input line oil passage 58 that communicates with the input hydraulic cylinder 26.
0 and an input side pressure control servo valve 62 that regulates the input line oil pressure, an oil pump 66 that pumps hydraulic oil to an output line oil passage 64 that communicates with the output side hydraulic cylinder 28, and an oil pump 66 that controls the output side line oil pressure. An output side pressure control servo valve 68 may be provided to regulate the pressure. In this way, the working oil pressure in the hydraulic cylinders 26 and 28 is independently controlled by the input side pressure control servo valve 62 and the output side pressure control servo valve 68, which each function as a pressure regulating valve, so that it is different from the above embodiment. In addition to obtaining similar effects, there is an advantage that the electromagnetic switching valve 46 and steps SS5.5sto to 5S12 in FIG. 2 are not required.

Further, as shown in FIG. 5, an electromagnetic switching valve 72 having a neutral position may be provided. In the neutral position of the solenoid valve 72, the first line oil passage 42 and the second line oil passage 50 are communicated with each other and with the output side hydraulic cylinder 28, and at the same time, each line of the input side hydraulic cylinder 26 Communication with oil passages 42 and 50 is cut off. Also in this embodiment, the working oil pressure in the hydraulic cylinders 26 and 28 is regulated independently by the first pressure control servo valve 44 and the second pressure control servo valve 52, so that the same effects as in the previous embodiment can be obtained. It will be done. Moreover, in the neutral position of the electromagnetic switching valve 72, the belt tension is applied to the first pressure control servo valve 44.
The first line hydraulic pressure Pfil and the second line hydraulic pressure P/2 are adjusted from the output side hydraulic cylinder 28 by the exclusive pressure regulating operation of the second pressure control servo valve 52 provided on the downstream side of the first line hydraulic pressure Pfil and the second line hydraulic pressure P/2.
Since the hydraulic pressure is common to both, the workload of the oil pump 38 is reduced, and the power loss for driving the oil pump 38 is advantageously reduced.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other aspects.

For example, in the above-mentioned embodiment, as shown in step SS8 or 5S12 in FIG. ' is the speed ratio e, the oil pressure P in the hydraulic cylinder 26, 7, the oil pressure P in the hydraulic cylinder 28
It may be determined from a functional formula or data map obtained in advance based on out, etc. In such a case, it is effective especially when changing the speed ratio quickly, and has the advantage of providing suitable drivability.

Also, the deviation (e”-e
), in order to obtain a transiently large thrust by making a correction of a magnitude corresponding to the above, it is sufficient that the oil pressure of at least one of the hydraulic cylinders 26 and 28 is changed by the correction.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a flowchart showing the operation of the apparatus of FIG. FIG. 3 is a diagram showing relationships used in explaining the flowchart in FIG. 2. 4 and 5 are diagrams corresponding to FIG. 1 showing other embodiments of the present invention, respectively. 16: Input shaft 18: Output shaft 20.22: Variable pulley 24: Transmission belt 26.28: Hydraulic cylinder (hydraulic actuator) Applicant: Toyota Motor Corporation Figure 3 pin->

Claims (5)

[Claims] (1) an input shaft and an output shaft, a pair of variable pulleys with variable effective diameters provided on the input shaft and the output shaft, respectively, and a transmission belt wound between the variable pulleys;
A pair of hydraulic actuators are provided on the input shaft and the output shaft, respectively, and apply a thrust force to the variable pulley in the direction of reducing the V-groove width, and by changing the thrust force of the hydraulic actuator, the transmission belt A hydraulic control device for a belt type continuously variable transmission that changes the tension and the speed ratio of the input shaft and the output shaft, the device comprising: a pair of pressure regulating valves that respectively adjust the hydraulic pressure in the hydraulic actuator; The required oil pressure in the pair of hydraulic actuators is determined from the relationship to obtain the target speed ratio and target input shaft torque of the continuously variable transmission, and the adjustment is performed so that the oil pressure in the hydraulic actuators becomes the required oil pressure. 1. A hydraulic control device for a belt type continuously variable transmission, comprising control means for controlling respective pressure valves. (2) The pressure regulating valves are provided in series between the hydraulic pressure source and the drain, and the control means controls the hydraulic pressure regulated by the pressure regulating valves to one or the other of the hydraulic actuators as necessary. A hydraulic control device for a belt-type continuously variable transmission according to claim 1, which includes a switching valve for supplying the power. (3) The switching valve has a neutral position, and in the neutral position, the oil passages each guiding the hydraulic pressure regulated by the pressure regulating valve to the hydraulic actuator are connected to each other, and
The hydraulic control device for a belt type continuously variable transmission according to claim 2, which closes between one of the oil passages and a hydraulic actuator connected to this one oil passage. (4) In the process of changing the speed ratio of the continuously variable transmission, the control means controls the speed ratio change speed by changing the oil pressure in the hydraulic actuator from the required oil pressure. A hydraulic control device for a belt type continuously variable transmission according to any one of items 1 to 3. (5) In the process of changing the speed ratio of the continuously variable transmission, the control means determines that the thrust difference of the variable pulley is the thrust difference at the target speed ratio based on the difference between the actual speed ratio and the target speed ratio. The belt type continuously variable transmission according to any one of claims 1 to 4, wherein the speed ratio change speed is controlled by controlling at least one of the pressure regulating valves so that the speed ratio change speed becomes greater than Hydraulic control device.