JP2950872B2 - Control device for continuously variable transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for electronically controlling a secondary pressure and a shift in a belt type continuously variable transmission for a vehicle, and more particularly to a control device for controlling a proportional electromagnetic relief valve. The present invention relates to control of secondary pressure using a pilot-type secondary control valve provided.

[Conventional technology]

In this type of continuously variable transmission, a primary pressure is applied to a primary pulley on an input side and a secondary pressure is applied to a secondary pulley on an output side to apply a pressing force to a belt wound around both pulleys. The secondary pressure is controlled so as to apply a pressing force that does not cause belt slip to the transmission torque, and the primary pressure shifts the belt toward the primary pulley or the secondary pulley to obtain a predetermined gear ratio. It is controlled by the pressing force.

Here, regarding the control valve for the secondary pressure, since the transmission torque depends on the speed ratio, a method of mechanically controlling the secondary pressure so as to apply a spring force corresponding to the speed ratio and balance the spring force is used. is there. However, according to this method, it is necessary to always assume the maximum state of the input torque, which causes an increase in the secondary pressure, pump loss, and the like. Therefore, the input torque is estimated, and the fluctuation of the discharge pressure of the oil pump is also reduced. In addition, there is a tendency that the secondary pressure is more accurately controlled to correspond to the transmission torque.

An important problem in the electronic control of the secondary pressure is a structure of a valve or the like that is hydraulically controlled by an electric signal. In view of this, a pilot-type device that generates a control pressure having a duty ratio according to an electric signal using a duty solenoid valve and presupposes the structure of a mechanical control valve, and applies the control pressure to the control valve is the applicant of the present application. Has been proposed.
However, according to this method, a circuit for the control pressure is required, and measures such as correcting fluctuations in the control pressure due to the oil temperature and the like are also required, and the hydraulic circuit becomes complicated. For this reason, a control valve that directly variably controls the secondary pressure by an electronic signal and an electronic control system related thereto have been developed.

Therefore, conventionally, there is a prior art in Japanese Patent Application Laid-Open No. Sho 62-31533, for example, with regard to electronic control of the above-described continuously variable transmission, particularly, secondary pressure. Here, it is shown that an output hydraulic pressure feedback type main hydraulic control solenoid valve is provided, and the secondary pressure is controlled by stroke of the spool with the balance between the electromagnetic force of the coil and the output hydraulic pressure.

[Problems to be solved by the invention]

By the way, in the above-mentioned prior art, a three-way valve may be used, and the spool may close the input port on the pump discharge port side.In this case, the pump may be damaged by an excessive load. Therefore, such a structure is not preferable.

Further, the structure in which the output hydraulic pressure acts on the end of the spool complicates the structure, increases the hydraulic pressure, and increases the electromagnetic force and power consumption of the coil.

Further, when the electric signal of the coil is interrupted due to disconnection or the like, the spool is located on the drain side, and the secondary pressure is not generated.

Here, as a method of preventing the pump discharge side from being shut off, it is conceivable to configure the secondary control valve to be a relief valve type. It is preferable that the relief valve is a direct acting type in which the spool is directly operated by the electromagnetic force of the solenoid because the structure is simplified. However, in actuality, when the hydraulic pressure is drained, the fluid force is increased, for example, in the direction of increasing the secondary pressure. Act on.
This fluid force becomes a factor that makes the balance of the force in the spool unstable, and particularly has a large effect when the engine speed is high and a large amount of hydraulic pressure is drained.

Therefore, as a method of reducing the influence of the fluid force, it is conceivable to increase the control force of the spool to relatively reduce the influence of the fluid force. In this case, if the electromagnetic force of the solenoid is increased, the size of the solenoid is increased and the power consumption is increased. Therefore, it is necessary to devise another method.

The present invention has been made in view of the above, and it is an object of the present invention to provide a control valve that is electronically controlled by a secondary pressure, is small, has high safety, has little influence of fluid force, and has a fail-safe function. It is another object of the present invention to provide a continuously variable control device which is capable of stabilizing a secondary pressure introduced into a control chamber of a secondary control valve.

[Means for solving the problem]

In order to achieve the above object, a control device for a continuously variable transmission according to the present invention includes a control system for controlling a secondary pressure of a secondary cylinder by regulating a pump discharge pressure by a secondary control valve to which an electric signal is input. The control pressure according to the solenoid current by the proportional electromagnetic relief valve is applied to one of the control valve spools to make the set pressure variable,
A secondary pressure is linearly controlled with respect to the solenoid current, and an oil passage communicating the hydraulic chamber of the secondary control valve and the proportional electromagnetic relief valve is provided inside the spool. .

[Action]

Based on the above configuration, the secondary control valve provided in the hydraulic control system of the continuously variable transmission linearly controls the secondary pressure with respect to the solenoid current by the control pressure of the proportional electromagnetic relief valve. Therefore, when the target secondary pressure is calculated by the electronic control system and the solenoid current is output according to the target secondary pressure, the secondary control valve controls the secondary pressure to be exactly and optimally equal to the target value.

At this time, an orifice action is generated by the choke throttle provided in the oil passage for the secondary pressure introduced into the control chamber by the oil passage bored inside the spool.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, an outline of a drive system of a continuously variable transmission with a lock-up torque converter will be described. Reference numeral 1 denotes an engine, and a crankshaft 2 is configured to be sequentially transmitted to a torque converter device 3, a forward / reverse switching device 4, a continuously variable transmission 5, and a differential device 6.

In the torque converter device 3, the crankshaft 2 is connected to the converter cover 11 and the pump impeller 12 a of the torque converter 12 via the drive plate 10. A turbine runner 12b of the torque converter 12 is connected to a turbine shaft 13, and a stator 12c is guided by a one-way clutch 14. A lock-up clutch 15 integrated with the turbine runner 12b is provided so as to be engaged with or released from the drive plate 10, and transmits engine power via the torque converter 12 or the lock-up clutch 15.

The forward / reverse switching device 4 includes a double pinion type planetary gear 16. The turbine shaft 13 is input to the sun gear 16 a and output from the carrier 16 b to the primary shaft 20. A forward clutch 17 is provided between the sun gear 16a and the carrier 16b.
The reverse brake 1 between the ring gear 16c and the case.
The planetary gear 16 is integrated with the forward shaft 17 to directly connect the turbine shaft 13 and the primary shaft 20. Also, the reverse power is output to the primary shaft 20 by the engagement of the reverse brake 18 and the forward clutch 17 is output.
And the release of the reverse brake 18 makes the planetary gear 16 free.

The continuously variable transmission 5 includes a primary pulley 22 having a primary shaft 20 and a primary cylinder 21 and a variable pulley spacing type.
However, a secondary pulley 25 having a secondary cylinder 24 is also provided on the secondary shaft 23, and a drive belt 26 is wound between the primary pulley 22 and the secondary pulley 25. Here, the pressure receiving area of the primary cylinder 21 is set larger, and the ratio of the winding diameter of the drive belt 26 to the primary pulley 22 and the secondary pulley 25 is changed according to the primary pressure to perform stepless transmission. In the differential device 6, an output shaft 28 is connected to the secondary shaft 23 via a pair of reduction gears 27, and a drive gear 29 of the output shaft 28 meshes with the final gear 30. A differential gear 31 of the final gear 30 is connected to left and right wheels 33 via an axle 32.

On the other hand, in order to obtain a hydraulic source for controlling the continuously variable transmission, a main oil pump 34 is disposed adjacent to the torque converter 12, and the main oil pump 34 is connected to the converter cover 11 by a pump drive shaft 35, and is always The main oil pump 34 is driven by engine power to generate hydraulic pressure. Here, in the continuously variable transmission 4, since the hydraulic pressure is controlled in a wide range of high and low, the oil pump 34 is, for example, of a roller vane type and has a plurality of sets of suction and discharge ports and is configured as a variable displacement type.

Next, a continuously variable transmission control system will be described as a hydraulic control system.

First, an oil passage 41 from an oil pump 34 communicating with an oil pan 40 communicates with a secondary control valve 50 to generate a predetermined secondary pressure Ps. This secondary pressure Ps is always supplied to the secondary cylinder 24 through an oil passage 42. Is done. The secondary pressure Ps is guided to the primary control valve 60 via the oil passage 43, and is supplied to and discharged from the primary cylinder 21 via the oil passage 44, so that the primary pressure Pp is generated.

The primary control valve 60 is of a flow rate control type based on a duty signal. A spool 62 is inserted into a valve body 61, and an initial setting spring 63 is biased on one of the spools 62.
Further, a duty solenoid valve 64 for guiding the secondary pressure Ps of the oil passage 43 is provided, and a pulse-like control pressure Pc is generated using the secondary pressure Ps as an original pressure in accordance with a duty signal from the control unit 70. Control pressure Pc is in oil passage 45
Thereby, it is guided to the port 61d at one end of the spool 62. Further, the secondary pressure Ps of the oil passage 43 is guided to a port 61e at the other end of the spool 62. Thus, the spool 62 is controlled by the relationship between the pulse-shaped control pressure Pc and the constant high secondary pressure Ps.
Operates at a refueling position at which the port 61a of the oil passage 43 communicates with the port 61b of the oil passage 44, and at an oil discharge position at which the port 61b communicates with the drain port 61c. The primary pressure Pp together with the ratio of oil supply / drainage time, that is, the inflow and outflow flow rates, is determined by the duty ratio
Is changed to control the shift.

The secondary control valve 50 is a pilot type equipped with a proportional electromagnetic relief valve. A stepped spool 52 is inserted into a valve body 51, and a spring 53 is biased on one of the spools 52. Further, a control chamber 54 is formed in a portion of the spring 53, and a proportional electromagnetic relief valve 55 is provided adjacently and integrally therewith.

The spool 52 has a large diameter land 52a from the spring 53 side.
And a small-diameter land 52b, and a hydraulic chamber 5 communicating with the oil passage 41.
At 1a, a reaction force of the secondary pressure Ps acts on both lands 52a and 52b in opposition to the spring 53. Further, the hydraulic pressure is drained to the drain port 51b by the land 52b to regulate the pressure, thereby enabling a self-feedback operation.

Further, an oil passage 52c with a choke throttle is provided inside the spool 52 for communicating the hydraulic part 51a with the control chamber 54 (see FIG. 5).

The oil passage 52c is given a function as an orifice by a shape with a choke throttle. Then, the secondary pressure Ps is always guided from the hydraulic chamber 51a to the control chamber 54 by the oil passage 52c.

The proportional solenoid relief valve 55 is provided in such a manner that a plunger 58 provided with a spring 57 in a proportional solenoid 56 is attracted by an electromagnetic force.
Is installed in the drain port 54a of the control room 54.

Then, in accordance with the electromagnetic force of the proportional solenoid 56, a control pressure Pc is generated in the control chamber 54 using the secondary pressure Ps as an original pressure, and the set pressure of the spool 52 is made variable. As a result, in the spool 52, the pressure receiving area difference ΔS between the lands 52a and 52b
Against the reaction force of the secondary pressure Ps acting on the spring 53
Force Fs and to force the opposing control pressure Pc acting on the area S ₁ of the land 52a, pressure adjustment so both are balanced. The balance equation in this case is as follows.

Pc · S ₁ + Fs = Ps · ΔS Also, in the proportional solenoid relief valve 55, the force of the spring 57
A pressing force (F ₀ −K · Is) corresponding to the electromagnetic force due to F ₀ , the solenoid current Is, and the constant K is generated, whereby the opening area Sc of the port 54 a is changed by the valve body 59 to generate the control pressure Pc. , The following equation holds.

Pc · Sc = F ₀ −K · Is Accordingly, the secondary pressure Ps is expressed by the following equation with respect to the solenoid current Is.

Ps = S ₁ · F ₀ / Sc · ΔS + Fs / ΔS- (K · S ₁ / Sc · ΔS)
That is, the control pressure Pc has an inverse proportional relationship with the solenoid current Is as shown in FIG. 3A, and the secondary pressure Ps has a proportional relationship with the control pressure Pc as shown in FIG. 3B. ,
As a result, as shown in FIG. 3 (c), the secondary pressure Ps linearly decreases in a one-to-one relationship with the increase of the solenoid current Is. When the solenoid current Is is zero, the secondary pressure Ps is maximized and has a fail-safe function for preventing belt slippage due to disconnection or the like. With such a proportional pilot type characteristic, it is sufficient that the control unit 70 determines the manipulated variable of the solenoid current with respect to the target secondary pressure by using this map and outputs the manipulated variable to the proportional solenoid 56.

The oil pump 34 is of a variable displacement type, and a relatively high lubricating pressure is always generated in the oil passage 46 on the drain side of the secondary control valve 50. Therefore, this lubrication pressure is
2, the circuit is configured to be supplied to the forward / reverse switching device 4, the lubricating portion of the belt 26, and the like.

 In FIG. 2, the electronic control system will be described.

First, the transmission control system includes a primary pulley rotation speed sensor 71, a secondary pulley rotation speed sensor 72, an engine rotation speed sensor 73, and a slot opening sensor 74. Then, in the control unit 70, the primary pulley rotation speed Np and the secondary pulley rotation speed Ns of the primary pulley rotation speed sensor 71 and the secondary pulley rotation speed sensor 72
Is input to the actual speed ratio calculating unit 75, and the actual speed ratio i is calculated as i = Np / N
Calculated by s. The actual gear ratio i and the slot opening θ of the throttle opening sensor 74 are input to the target primary pulley rotation speed search unit 76, and the target primary pulley rotation speed NPD is determined based on the relationship of i−θ. Target primary pulley rotation speed N
The PD and the secondary pulley rotation speed Ns are used to calculate a target gear ratio calculation unit 77.
And the target gear ratio is is calculated from is = NPD / Ns. In this way, based on the speed change pattern, the target speed ratio is obtained from the secondary pulley rotation speed Ns, the actual speed ratio i, and the throttle opening θ in accordance with each driving and running condition.

Here, the flow rate that determines the required oil amount of the primary cylinder 21 corresponds one-to-one with the change speed de / dt of the actual pulley position e, and the actual pulley position change speed de / dt is equal to the target pulley position es.
And the actual pulley position e (e−e). The flow rate when the valve operates at the duty ratio D is a function of the duty ratio D and the actual pulley position e. Therefore, the duty ratio D is determined by the actual pulley position change speed de / dt and the actual pulley position e. Will be able to decide.

Therefore, the actual gear ratio i and the target gear ratio is input to the actual pulley position converter 78 and the target pulley position converter 79,
e, the target pulley position es is input-converted, and the actual pulley position e and the target pulley position es are converted to the actual pulley position change speed calculating unit 80.
And the actual pulley position change speed de / dt is calculated as follows.

In _{de / dt = K 1 · (} es-e) + K 2 · des / dt above equation, K _1, K ₂ are constants, des / dt is a phase lead element.

And the actual pulley position change speed de / dt, the actual pulley position e
Is input to the duty ratio search unit 81, and D = f (de / dt,
The duty ratio D is searched according to the relationship e), and the duty ratio D corresponding to the upshift or downshift and the deviation (es−e) is obtained. This duty signal is output to the duty solenoid valve 64 via the drive unit 82.

 Next, the secondary pressure control system will be described.

First, an engine torque calculation unit 83 to which the throttle opening θ and the engine speed Ne are input is provided, and the engine torque Te is estimated from the torque characteristics of θ−Ne. The engine speed Ne and the primary pulley speed Np on the input and output sides of the torque converter are input to a torque amplification factor calculator 84, and the speed ratio n
(Np / Ne) is determined, and the engine torque Te and the torque gain t are input to the input torque calculation unit 85 to calculate the input torque Ti according to Ti = Te · t.

On the other hand, the actual pulley position e is input to the required secondary pressure setting section 86 to determine the slip limit secondary pressure Psu required for unit torque transmission, and the slip limit secondary pressure Psu required for unit torque transmission and the input torque Ti The target secondary pressure Pss is input to the secondary pressure calculation section 87, and Pss = Ti ·
Calculated by Psu. Also, the target secondary pressure calculating section 87
Is input with the secondary pulley rotational speed Ns, and the centrifugal oil pressure and the like corresponding to the secondary pulley rotational speed Ns are reduced and corrected.

Here, in order to perform feedback control of the secondary pressure control, a pressure sensor 88 is provided, and the actual secondary pressure Ps and the target secondary pressure Pss detected by the pressure sensor 88 are input to the solenoid current calculation unit 89. And target secondary pressure
The difference ΔP (= Pss−Ps) between Pss and the actual secondary pressure Ps is obtained, and the solenoid current Is is corrected in accordance with the difference ΔP.
Output is made to the proportional solenoid 56 via 90.

Next, the operation of the control device for a continuously variable transmission having such a configuration will be described.

First, the operation of the engine 1 causes the torque converter 12
The oil pressure is generated by driving the oil pump 34 by the converter cover 11 and the rear drive shaft 35, and the oil pressure is
Through the control chamber 54 of the secondary control valve 50.

Therefore, when the vehicle is stopped, the target speed is of the transmission control system is set to a value greater than, for example, 2.5 as the maximum speed ratio on the mechanism of the continuously variable transmission 5, and a duty signal corresponding to this is input to the duty solenoid valve 64 and By operating the control valve 60 to the drain side, the primary pressure Pp does not occur. Therefore, all of the secondary pressure Ps from the secondary control valve 50 is supplied only to the secondary cylinder 24, and the continuously variable transmission 5 is in the low speed stage with the maximum gear ratio at which the belt 26 is shifted to the secondary pulley 25 most.

At this time, the lock-up clutch 15 is released by a hydraulic control system (not shown) and the torque converter 12 is supplied with oil. Therefore, for example, when shifting to the drive range, the forward clutch 17 of the forward / reverse switching device 4 is engaged by refueling to be in the forward position. For this reason, the power of the engine 1 is input to the primary shaft 20 of the continuously variable transmission 5 via the torque converter 12 and the forward / reverse switching device 4, and the primary pulley 2
2. The power of the maximum speed ratio is output to the secondary shaft 23 by the secondary pulley 25 and the belt 26, and the power is transmitted to the wheels 33 via the differential device 6 to be able to start.

On the other hand, in the secondary pressure control system, the engine torque is always
At the time of idling before starting, the input torque Ti is small together with the engine torque Te, and the target secondary pressure Pss is set relatively low. Therefore, a relatively large solenoid current Is flows in the proportional solenoid 56 in the proportional electromagnetic relief valve 55 of the secondary control valve 50 according to the target secondary pressure Pss in the map of FIG. 3C, and the plunger 58 is retracted by the electromagnetic force. Then, the pressing force of the valve body 59 is reduced. For this reason, the control pressure Pc decreases to set the set pressure of the spool 52 low, and the spool 52 strokes to the left, a large amount of oil is drained by the land 52b, and is controlled to a low secondary pressure Ps.

Next, when the accelerator is started, the engine torque
Te, torque amplification factor t, secondary pressure Psu at the slip limit required for unit torque transmission is large, so target secondary pressure Pss is also calculated to increase rapidly.Solenoid current Is is calculated by the difference from secondary pressure Ps of pressure sensor 88. Dramatically reduced. Therefore, in the secondary control valve 50, the pressing force of the valve body 59 increases in accordance with the decrease in the electromagnetic force of the proportional solenoid 56 of the proportional electromagnetic relief valve 55, and a high control pressure Pc is generated, and the set pressure of the spool 52 increases. Therefore, the spool 52 operates so as to stroke rightward to reduce the drain amount, and the secondary pressure Ps is controlled to be high. When the shift control is performed after the start, the lock-up clutch 15 is engaged and the calculated value of the target secondary pressure Pss is reduced, and the set pressure sequentially decreases along with the control pressure Pc by the proportional electromagnetic relief valve 55 in the secondary control valve 50,
The secondary pressure Ps is controlled to decrease. In this way, the characteristics of the secondary pressure Ps are summarized as shown in FIG. 4, and the optimal control is performed so as to always secure the minimum pulley pressing force that does not cause belt slip with respect to the transmission torque.

Here, the primary pressure Ps
Fluctuates, the stroke of the spool 52 changes and is corrected by the hydraulic pressure of the hydraulic chamber 51a of the secondary control valve 50,
In this way, a self-feedback effect occurs. Further, if the solenoid current Is is interrupted during running due to disconnection or the like, the set pressure becomes maximum together with the control pressure Pc by the spring 57 in the secondary control valve 50, and the secondary pressure Ps is controlled to be the highest, thus Fail-safe to prevent belt slip.

Also, after the start, if the shift start condition of is> 2.5 is satisfied due to the driving and running conditions, the actual speed ratio i and the target speed ratio is converted into the actual pulley position e and the target pulley position es by the shift control system, The position change speed de / dt is calculated. Then, a duty signal corresponding to the actual pulley position changing speed de / dt and the actual pulley position e is output to the duty solenoid valve 64, and the control pressure Pc and the secondary pressure Ps of the original pressure oppose the primary control valve 60. To control the amount of oil supplied to the primary cylinder 21 to increase the primary pressure Pp. Then, the belt 26 is sequentially shifted toward the primary pulley 22 by the pressing force of the primary pulley 22, and the upshift control is performed to a high-speed gear having a small speed ratio. In addition, during deceleration, the primary cylinder 60
The amount of oil drainage 21 is controlled to reduce the primary pressure Pp, and the downshift control is performed to the low speed stage.

Although the embodiments of the present invention have been described above, the electronic control system is not limited to the embodiments.

〔The invention's effect〕

As described above, according to the present invention, in the control system for controlling the secondary pressure of the secondary cylinder by adjusting the pump discharge pressure by the secondary control valve to which the electric signal is input, one of the spools of the secondary control valve is used. The control pressure according to the solenoid current by the proportional electromagnetic relief valve is applied to vary the set pressure, the secondary pressure is linearly controlled with respect to the solenoid current, and the secondary control valve is provided inside the spool. Since the oil passage which connects the hydraulic chamber of the above and the proportional electromagnetic relief valve is provided, the secondary pressure can be linearly controlled with respect to the solenoid current by the control pressure of the proportional electromagnetic relief valve. Therefore, when the target secondary pressure is calculated by the electronic control system and the solenoid current is output according to the target secondary pressure, the secondary pressure is controlled by the secondary control valve to be exactly and optimally equal to the target value.

Further, an orifice action is generated by the choke throttle provided in the oil passage on the secondary pressure introduced into the control chamber of the secondary control valve by the oil passage bored inside the spool. As a result, the secondary pressure can be stably supplied to the control chamber, and the same effect as that of the orifice can be obtained with a throttle diameter larger than the orifice.

[Brief description of the drawings]

1 is an overall configuration diagram showing an embodiment of a control device for a continuously variable transmission according to the present invention, FIG. 2 is a block diagram of an electronic control system, and FIGS. 3 (a), (b) and (c) are secondary. FIG. 4 is a characteristic diagram of the control valve, FIG. 4 is a characteristic diagram of the secondary pressure, and FIG. 5 is a sectional view showing the inside of the spool of the secondary control valve in FIG. 5 ... continuously variable transmission, 21 ... primary cylinder, 24 ...
Secondary cylinder, 41, 42, 43 …… Secondary pressure oil passage,
44 …… Primary oil pressure passage, 50 …… Secondary control valve, 52
…… Spool, 53 …… Spring, 54 …… Control room, 55…
… Proportional solenoid relief valve, 56… Proportional solenoid, 59 ……
Valve element, 60 …… Primary control valve, 70 …… Control unit

Claims (3)

(57) [Claims] In a control system for controlling a secondary pressure of a secondary cylinder by regulating a pump discharge pressure by a secondary control valve to which an electric signal is inputted, a solenoid current is supplied to one of spools of the secondary control valve by a proportional electromagnetic relief valve. The control pressure according to the above is applied to vary the set pressure, the secondary pressure is linearly controlled with respect to the solenoid current, and the hydraulic chamber of the secondary control valve and the proportional electromagnetic relief are provided inside the spool. A control device for a continuously variable transmission, wherein an oil passage communicating with a valve is provided. 2. The control of a continuously variable transmission according to claim 1, wherein a choke throttle is provided in an oil passage provided to the proportional electromagnetic relief valve provided inside the spool. apparatus. 3. The control device for a continuously variable transmission according to claim 1, wherein said proportional electromagnetic relief valve is arranged coaxially with said spool.