JPH0128262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a hydraulic control device for an automatic transmission, and more particularly to measures to reduce shift shock during gear changes.

(Prior Art) Generally, in order to reduce the shift shock during gear shifting in an automatic transmission, the hydraulic pressure supplied to the friction element that switches the power transmission path in the transmission gear set to multiple stages is gradually increased. Attempts are being made to tighten the friction elements with less impact. For example, JP-A-57-
In the electronic automatic transmission disclosed in Publication No. 127148, a flow control valve with a check valve is interposed in the oil passage from the 1-2 shift valve to the friction element constituting the 2nd speed, and an accumulator is installed downstream of the flow control valve. In addition, the upstream side of the flow control valve with check valve is directly connected to the cutback valve, and when the 1-2 shift valve is switched from 1 to 2, the cutback valve is immediately operated to switch the regulator valve. The pressure regulation pressure (line pressure) is reduced by a predetermined value, and the pressure regulation pressure is gradually applied to the friction element to reduce the shift shock during the 1->2 shift.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional system, line pressure acts on the cutback valve and the friction element due to the switching operation of the 1-2 shift valve, so it is difficult to supply oil to the friction element. If the speed increases as the oil temperature increases, the friction element may be engaged before the line pressure is reduced by the cutback valve. In this case, although the accumulator suppresses the sudden increase in the working pressure on the friction element, engagement is performed even at the high line pressure before it is reduced by the cutback valve.
The gear shifting shock is correspondingly large.

The present invention has been made in view of the above, and an object of the present invention is to appropriately control the operating timing of the cutback valve and the switching timing of the shift valve in relation to each other, thereby improving the timing of upshifting and downshifting. The objective is to always effectively and reliably reduce the shift shock by engaging the friction elements with a low line pressure reduced by a cutback valve.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a speed change gear set, a friction element that switches a power transmission path in the speed change gear set to a plurality of stages, and a friction element that an automatic transmission comprising: a hydraulic circuit for controlling the operation of the friction element; The regulator valve is equipped with a regulator valve that regulates the hydraulic pressure to be adjusted, and a cutback valve that generates a pilot signal pressure that changes the regulation pressure in the regulator valve.The cutback valve generates a shift signal that operates a shift valve. The shift valve is controlled by the balance between the shift signal pressure and the pilot signal pressure of the cutback valve through an orifice, and when shifting up, the cutback valve is in line. After the shift valve operates in the direction of reducing line pressure, the shift valve operates to a high speed gear, and when downshifting, the shift valve operates to a low gear, and then the cutback valve operates in a direction to increase line pressure. It is characterized by being configured.

(Function) With the above configuration, in the present invention, when a shift is up, the cutback valve operates in the direction of reducing line pressure and then the shift valve is operated to the high gear side, while when a shift is down, the shift valve is conversely moved to the low gear side. After the cutback valve is activated, the cutback valve operates in the direction of increasing the line pressure, so that the friction elements are always engaged with less impact even with the lower line pressure reduced by the cutback valve. It is.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

The drawing shows a hydraulic circuit A when the present invention is applied to a hydraulic control device for an electronic automatic transmission. This electronic automatic transmission includes a speed change gear set (not shown) having a large number of speed change gears disposed between an engine drive shaft and a propulsion shaft, and a power transmission system in the speed change gear set that is connected to a first speed. It consists of a plurality of friction elements such as friction clutches that can be switched to four stages of 4th to 4th speeds, and the hydraulic circuit A that controls the operation (engagement and release) of each friction element in accordance with a shift signal.

In the hydraulic circuit A in the drawing, 1 is an oil pump driven by an engine, and 2 is 1 which receives hydraulic pressure P _L from the oil pump 1 via an oil passage 1a.
-2 shift valve, the 1-2 shift valve 2 communicates with a friction element that constitutes a first speed through an oil passage 3, and constitutes a second speed through another oil passage 4. When the spool 2a is positioned at the first speed position shown in the figure by a spring 2b that biases the spool 2a to the left in the figure, the oil passage 4 is opened to the tank and the oil pressure is At the same time, the hydraulic pressure P _L is supplied to the oil passage 3 to engage the friction element constituting the first speed, thereby shifting the power transmission path of the transmission gear set to the first speed, while the spool 2a is When the oil passage 3 is moved to the right in the figure against the biasing force of the spring 2b and is positioned at the second speed position, the oil passage 3 is opened to the tank to discharge the oil pressure, and the oil pressure P _L is transferred to the oil passage 4. The power transmission system is configured to shift the power transmission line to the second speed by supplying the friction element to the friction element constituting the second speed.

Reference numeral 5 denotes a regulator valve that regulates the hydraulic pressure P _L discharged from the oil pump 1 and acting on each friction element. The hydraulic pressure from the oil pump 1 acts against the biasing force of the spring 5b, and the spring 5b
Throttle pressure P _TH and line pressure P _L (R range only) act in the direction that increases the biasing force b, and therefore the oil pressure from oil pump 1 (hydraulic pressure P _L acting on each friction element) is applied to the throttle. It is configured to adjust the height according to the opening degree and vehicle speed, and further adjust the hydraulic pressure P _L to increase by a certain value when the vehicle is moving backward.

Further, numeral 6 is a cutback valve for changing the level of the regulating pressure in the regulator valve 5, and the cutback valve 6 has a throttle regulating pressure P _TH ′ (P _TH ′<P _L ). The pressure chamber 5 is activated and opposes the biasing force of the spring 5b of the regulator valve 5 via the oil passage 7.
c is in communication and the spool 6a is in the normal position shown in the figure, where it has moved to the right in the figure against the biasing force of the spring 6b that biases the spool 6a to the left in the figure, the oil passage 7 is On the other hand, when the spool 6a is moved to the left in the figure by the biasing force of the spring 6b and is positioned at the cutback position, the throttle adjustment pressure P _TH ' is used as a pilot signal pressure to be applied to the regulator valve via the oil passage 7. By acting on the pressure chamber 5c of No. 5,
It is configured to lower the regulated pressure at the regulator valve 5 accordingly.

In addition, 8 is a 1-2 shift solenoid for controlling the operation of the 1-2 shift valve 2, and the 1-2 shift solenoid 8 is used to control the operation of the 1-2 shift valve 2.
-2 The line pressure P _L (shift signal pressure) to the spring chamber 2c of the shift valve 2 is discharged to the tank 9 by turning ON. and the shift signal pressure
P _L acts through the oil passage 10 on the pressure chamber 6c that opposes the biasing force of the spring 6b of the cutback valve 6, and the shift signal pressure P _L causes the spool 6a of the cutback valve 6 to be moved to the steady state shown in the figure. The valve area B is
It is set to satisfy ×P _L >F _S1 (F _S1 : biasing force of spring 6b). Further, an oil passage 11 is provided in the spring chamber 6d of the cutback valve 6.
Acting pressure (line pressure) P _L is applied to the friction elements constituting the second speed through the. Therefore, the shift signal pressure (line pressure) P _L is applied to the cutback valve 6.
The spool 6a is positioned at a steady position when only the spool 6a acts, while the spool 6a is positioned at the cutback position due to the biasing force of the spring 6b when the acting pressure (line pressure) P _L on the friction element constituting the second gear also acts. It is configured such that its operation is controlled by the balance between the shift signal pressure P _L and the pressure P _L applied to the friction element constituting the second speed.

The pilot signal pressure P _{TH '} from the cutback valve 6 acts on the pressure chamber 2d opposing the biasing force of the spring 2c of the 1-2 shift valve 2 through the oil passage 12 and orifice 13. , the pilot signal pressure P _TH ' causes the spool 2 to
The valve area A is A
When the shift signal pressure P L acts on the spring chamber 2c so as to satisfy P _TH ′>F _S2 (F _S2 : biasing force of the spring 2b) and in the operating state of the pilot signal pressure P _{TH ′} , the shift signal The spool 2a is positioned at the first speed position based on the pressure P _L against the pilot signal pressure P _TH ', so that A×P _L +F _S2 >A×P _TH ' is satisfied. Therefore, when only the pilot signal pressure PTH _' is applied, the spool 2a is positioned at the second speed position, while the shift signal pressure is
The operation is controlled by the balance between the shift signal pressure P _L and the pilot signal pressure P _TH ' of the cutback valve 6 so that the spool 2a is positioned at the first speed position when P _L also acts. There is.

Next, the operation of the above embodiment will be explained. First, in the first gear, the 1-2 shift solenoid 8
In the OFF state, the tank 9 side is closed, the shift signal pressure P _L is acting on the spring chamber 2c of the 1-2 shift valve 2, and the 1-2 shift valve 2 is in the first speed position. Therefore, the oil pressure (line pressure) P _L from oil pump 1 passes through oil passage 3 to
It is supplied to the friction elements that make up the speed. At this time, in the cutback valve 6, the shift signal pressure P _L is acting on the pressure chamber 6c, and the oil passage 11 is opened to the tank in the spring chamber 6d. Since no operating pressure is applied, the spool 6a is positioned at the steady position shown in the figure against the biasing force of the spring 6b due to the shift signal pressure P _L , and the pilot signal pressure P _TH ' is not generated. Therefore, the pressure regulation at regulator valve 5 (line pressure P _L )
The pressure is regulated to a normal high pressure value depending on the vehicle speed and throttle opening.

Now, when the 1-2 shift solenoid 8 is activated to shift up the power transmission line to 2nd speed,
Shift signal pressure P _L is released to tank 9 and 1-2
Although the action of the shift signal pressure P _L is released on the shift valve 2, the spool 2a is still held at the first speed position shown in the figure by the biasing force of the spring 2b. On the other hand, in the cutback valve 6, when the action of the shift signal pressure P _L is released, the spool 6a is moved to the left by the biasing force of the spring 6b and positioned at the cutback position, and the pilot signal pressure P _TH ' is generated. . As a result, the regulated pressure P _L at the regulator valve 5 is suppressed and reduced by that amount, and the spool 2a of the 1-2 shift valve 2 acts on the pilot signal pressure P _TH ' to the pressure chamber 2d. It moves to the right for the first time and is positioned at the second speed position. At this time, due to the action of the orifice 13, the pilot signal pressure _PTH ' acts on the pressure chamber 2d of the 1-2 shift valve 2 later than the action on the pressure chamber 5c of the regulator valve 5. As a result, after the line pressure (acting pressure on the frictional element) P _L is reliably reduced, the frictional element constituting the second gear is engaged with less impact, and the shift to the second gear is completed. At this time, the working pressure on the friction element that constitutes the second speed is
P _L also flows into the spring chamber 6d of the cutback valve 6 through the oil passage 11, and assists in maintaining the cutback position.

Then, in this state, when the 1-2 shift solenoid 8 is turned OFF again to shift down the power transmission line to 1st speed, the cutback valve 6 operates as follows.
A shift signal pressure P _L acts on the pressure chamber 6c, but this pressure P _L is balanced with the working pressure P _L on the friction element acting on the spring chamber 6d, and the spool 6a is moved to the cutback position by the biasing force of the spring 6b. still held. On the other hand, in the 1-2 shift valve 2, the pilot signal pressure is applied to the pressure chamber 2d.
Although P _TH ′ is acting, the spool _2a is
is moved to the left and positioned at the first speed position.
As a result, the friction elements constituting the first speed are engaged with less impact even at the line pressure P _L on the low pressure side as the cutback valve 6 continues to operate. Thereafter, as the 1-2 shift valve 2 shifts to the first speed position, the spring chamber 6d of the cutback valve 6 is opened to the tank via the oil passage 11, so that the spool 6a is moved to the pressure chamber 6c. The shift signal pressure P _L returns to the normal position and the generation of the pilot signal pressure P _TH ' stops.
As a result, the regulated pressure at the regulator valve 5 rises again to a high pressure value corresponding to the vehicle speed and throttle opening, and the engagement force of the friction element is increased. In addition, at this time, the first shift valve 2 of 1-2
The speed position state is maintained by the biasing force of the spring 2b and the shift signal pressure P _L. By the way, 1
To ensure that friction elements are engaged with less impact even when the line pressure P _L on the low pressure side is reduced by a cutback valve 6, both when shifting up from speed to second speed and when downshifting from second speed to first speed. Therefore, it is possible to effectively and reliably reduce the shift shock and improve riding comfort.

In the above embodiment, the case where the present invention is applied to shifting between 1st and 2nd gears has been described, but the present invention can be similarly applied to shifting between other adjacent gears such as 2nd and 3rd gears. Needless to say, the speed change control method is not limited to electronic type, but may be a normal hydraulic type.

(Effects of the Invention) As explained above, according to the hydraulic control device for an automatic transmission of the present invention, the operations of the cutback valve and the shift valve are correlated with each other, and the shift timing and friction between adjacent gears are controlled. Since the timing of reducing the working pressure on the element was appropriately controlled,
Frictional elements can always be engaged with low working pressure, which is reduced by the cut-off valve.
Therefore, shifting can be performed reliably with fewer shocks, contributing to improved riding comfort.

[Brief explanation of drawings]

The drawing is a hydraulic circuit diagram showing an embodiment applied to a hydraulic control device for an electronic automatic transmission. A...Hydraulic circuit, 2...1-2 shift valve,
5...regulator valve, 6...cutback valve, 13...orifice.

Claims (1)

[Claims] 1. In an automatic transmission consisting of a speed change gear set, a friction element that switches a power transmission path in the speed change gear set to a plurality of stages, and a hydraulic circuit that controls the operation of the friction element, the high speed speed is changed between adjacent speeds. a shift valve for supplying and discharging hydraulic pressure acting on the friction element to shift the gear to a low gear; a regulator valve regulating the pressure pressure acting on the friction element; and a regulator valve regulating pressure at the regulator valve. and a cutback valve that generates a pilot signal pressure that changes in height, the cutback valve is controlled by the balance between the shift signal pressure that operates the shift valve and the pressure applied to the friction element, and the shift valve is controlled by the shift signal pressure. It is controlled by the balance between the cutback valve and the pilot signal pressure of the cutback valve through the orifice, and during upshifting, the cutback valve operates in the direction of reducing line pressure, and then the shift valve operates to the high speed side and shifts down. A hydraulic control device for an automatic transmission, characterized in that, at times, the shift valve operates toward a lower gear, and then the cutback valve operates in a direction to increase line pressure.