JPH0554579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a line pressure control device for an automatic transmission.

(Prior Art) An automatic transmission determines a power transmission path by selectively operating various friction elements using line pressure obtained by regulating oil from an oil pump with a pressure regulator valve. It is configured to obtain a predetermined gear position.

By the way, if the line pressure is too high, the engagement capacity of the friction elements that are activated by the line pressure is too high, causing problems such as gear shifting shocks, and conversely, if the line pressure is too low, the engagement capacity of the friction elements that are activated by the line pressure is insufficient, causing this friction. Elements may slip, causing problems such as seizure and transmission loss. On the other hand, the required engagement capacity of the friction element to be operated is proportional to the engine load. Therefore, the line pressure must be increased in proportion to the engine load.

Therefore, in Japanese Patent Application No. 60-199316, the applicant of the present application previously proposed a pressure regulator valve that responds to the engine load signal pressure and regulates the oil from the oil pump to a line pressure corresponding to the engine load signal pressure. ,
We have already proposed an automatic transmission equipped with a line pressure control device comprising a pressure modifier valve that uses this line pressure as a source pressure to generate the engine load signal pressure mentioned above.

(Problem to be solved by the invention) However, in such a configuration, since the source pressure of the engine load signal pressure is a closed loop using the line pressure as the line pressure, when the line pressure fluctuates, this is amplified by the pressure relief valve and the engine load signal pressure is amplified by the pressure relief valve. When the load signal pressure is varied, this engine load signal pressure amplifies and fluctuates the line pressure regulated by the pressure regulator valve, resulting in inaccurate line pressure control due to the unstable vibration system. I confirmed that it would happen.

(Means for Solving the Problems) The present invention aims to prevent the engine load signal pressure from fluctuating even with fluctuations in line pressure, thereby solving the above-mentioned problem in which the line pressure is amplified and fluctuated. The line pressure control device of the above type is characterized in that an accumulator is connected to a circuit that leads the engine load signal pressure to the pressure regulator valve.

(Function) The pressure regulator valve responds to the engine load signal pressure from the pressure modifier valve.
Regulates the oil from the oil pump to line pressure according to the engine load signal pressure. The pressure modifier valve uses this line pressure as a source pressure to generate the engine load signal pressure, and enables the pressure regulator valve to adjust the line pressure.

Here, when the line pressure fluctuates, the engine load signal pressure that uses this as the source pressure also tends to fluctuate. Since the accumulator acts to absorb such fluctuations in the engine load signal pressure, the engine load signal pressure does not fluctuate with fluctuations in line pressure and maintains a value corresponding to the engine load. Therefore, the engine load signal pressure does not amplify line pressure fluctuations, and line pressure control can be performed accurately.

(Example) Hereinafter, the present invention will be described in detail based on the illustrated example.

The drawing shows an embodiment of the line pressure control device of the present invention.
In the figure, 1 is an oil pump, 2 is a pressure regulator valve, 3 is a pressure modifier valve, 4 is a duty solenoid, and 5 is an accumulator provided in the present invention.

The oil pump 1 is a variable displacement vane pump driven by an engine, and the eccentricity between the housing and the rotor is reduced when the pressure toward the displacement control actuator 6 exceeds a certain value, so that the displacement becomes smaller.

The pressure regulator valve 2 includes a spool 2b elastically supported at the left half position in the figure by a spring 2a, and a plug 2c opposed to the lower end surface of the spool in the figure.
Basically, the oil discharged from the oil pump 1 to the circuit 7 is regulated to a certain pressure determined by the spring force of the spring 2a.
When a force is applied upward in the figure, the above pressure is increased by that amount to reach a predetermined line pressure. For this purpose the pressure regulator valve 2
The pressure in the circuit 7 is received by the pressure receiving surface 2d of the spool 2b through the damping orifice 8, and the spool 2b is biased downward by this, and the ports 2e to 2 are opened and closed depending on the stroke position of the spool 2b. 2 hours will be provided. The port 2e is connected to the circuit 7, and is arranged so that the spool 2b communicates with the tangle ports 2h and 2f that descend from the left half position in the figure. The port 2f is arranged so that as the spool 2b descends from the left half position in the figure, communication with the port 2g serving as a drain port is reduced, and at the point when communication with this is cut off, communication with the port 2e begins. The port 2f is then connected to the capacity control actuator 6 of the oil pump 1 via a circuit 10 having a bleed 9 in the middle. The plug 2c of the pressure regulator valve 2 has a circuit 1 on its lower end surface in the figure.
It is assumed that the engine load _signal pressure from the circuit 12 is received on the pressure receiving surface 2i, and an upward force in the figure corresponding to these pressures is applied to the spool 2b.

The pressure modifier valve 3 generates engine load signal pressure to the circuit 12, and the spring 3a
and a spool 3b which is biased downward in the figure by control pressure from the circuit 13, and this spool faces the chamber 3c at the end opposite to the spring 3a. The pressure modifier valve 3 further includes an input port 3d to which the circuit 7 is connected, and a drain port 3e.
An output port 3f is provided between these ports, and the port 3f passes through the orifice 14 to the circuit 1.
2 and connect chamber 3c to this circuit. These three ports are arranged so that the port 3f is exactly blocked from the ports 3d and 3e at the left half position in the figure of the spool 3b.

The pressure modifier valve 3 receives the spring force from the spring 3a and the force from the control pressure from the circuit 13 downward in the figure on the spool 3b, and
The spool 3b receives the force due to the output pressure (engine load signal pressure) from the port 3f that has reached upward in the figure, and moves the spool 3 to a position where these forces are balanced.
Stroke b. If the output pressure from the port 3f is insufficient to compensate for the downward force, the spool 3b descends beyond the pressure regulating position shown in the left half. At this time, the port 3f communicates with the port 3d, and receives supplementary line pressure from the circuit 7 to increase the output pressure. Conversely, if this output pressure is too high to match the downward force, the spool 3b will rise toward the right half position in the figure. At this time port 3f
is connected to the drain port 3e, and the output pressure is reduced. By repeating this action, the pressure modifier valve 3 regulates the output pressure from the port 3f to a value corresponding to the sum of the spring force of the spring 3a and the force due to the control pressure from the circuit 13, and adjusts this pressure to a value corresponding to the sum of the force due to the spring force of the spring 3a and the control pressure from the circuit 13. The signal pressure is supplied from the circuit 12 to the plug 2c of the pressure regulator valve 2.

The duty solenoid 4 is for duty-controlling the control pressure in the circuit 13, and is made up of a coil 4a, a spring 4b, and a plunger 4c. It is assumed that the electromagnetic attraction of the plunger 4c leads to the drain port 4d. This duty solenoid 4 is controlled by a computer (not shown) to turn the coil 4a ON and OFF at a constant cycle, and to control the ratio of ON time to this constant cycle (data ratio) according to the duty ratio in the circuit 13. Generate pressure. By the way, when selecting reverse of automatic transmission, the duty ratio is set to 100.
%, the control pressure in the circuit 13 is set to 0, and otherwise the duty ratio is decreased as the engine load (for example, engine throttle opening) increases, thereby increasing the control pressure in the circuit 13 as the engine load increases. do.

The accumulator 5 provided in the present invention is constructed by elastically supporting an accumulator piston 5a at the left half position in the figure by a spring 5b. The chamber 5c on one side of the piston 5a is opened to the atmosphere, and the chamber 5d on the other side is connected to the circuit 12 by a circuit 16.

The operation of the above embodiment will be explained next.

The pressure regulator valve 2 is normally in the left half state in the figure, and when oil is discharged from the oil pump 1, this oil flows into the circuit 7. At the left half position of the spool 2b, the oil in the circuit 7 is not drained at all, and the pressure increases. This pressure acts on the pressure receiving surface 2d via the orifice 8, pushes down the spool 2b against the spring 2a, and connects the port 2e to the port 2h. As a result, the above pressure is partially drained from the port 2h and lowered, and the spool 2b is pushed back by the spring 2a. By repeating this action, the pressure regulator valve 2 basically reduces the pressure (line pressure) P _L in the circuit 7 to the spring 2.
The value corresponds to the spring force of a.

Incidentally, surplus oil from the port 2h is directed to the torque converter of the automatic transmission through the circuit 17 and is used as hydraulic oil.

By the way, the reverse selection pressure P _R from the circuit 11 and the engine load signal pressure from the circuit 12 act on the plug 2c, causing the plug 2c to come into contact with the spool 2b as shown in the right half of the figure, and the force due to the above pressure is applied. extends to the spool 2b to assist the spring 2a. Therefore, the pressure regulator valve 2 increases the line pressure P _L by an amount corresponding to this force.

First, let me explain when automatic transmission selects reverse.
At this time, the reverse selection pressure _PR is supplied from the circuit 11.
However, at this time, the duty of the duty solenoid 4 is set to 100% as described above, and the control pressure in the circuit 13 is set to 0. Because of this, spool 3b
The force that urges the engine downward in the figure is only the spring force of the spring 3a, and the pressure modifier valve 3 maintains the engine load signal pressure to the circuit 12 at a small constant value corresponding to the spring force. On the other hand, the reverse selection pressure
P _R is the same value as the line pressure P _L , and the pressure regulator valve 2 then maintains the line pressure P _L at the desired constant value for the reverse selection.

Next, when the reverse is not selected, there is no reverse selection pressure P _R from the circuit 11, and the plug 2c is urged upward in the figure only by the engine load signal pressure from the circuit 12. At this time, the duty ratio of the duty solenoid 4 is decreased as the engine load increases, increasing the control pressure within the circuit 13. Therefore, the downward force of the spool 3b in the figure increases as the engine load increases, and the pressure modifier valve 3 increases the engine load signal pressure to the circuit 12 as the engine load increases. In other words, this engine load signal pressure is a value obtained by amplifying the control pressure (proportional to the engine load) in the circuit 13 by the spring force of the spring 3a. Therefore, at this time, pressure regulator valve 2
can control the line pressure P _L to increase as the engine load increases to match the demand.

During line pressure control as described above, when the oil pump 1 reaches a certain rotation speed due to an increase in engine speed, the oil discharge amount that increases accordingly becomes excessive, and the pressure in the circuit 7 exceeds the pressure regulation value. . This pressure lowers the spool 2b further from the pressure regulating position in the right half of the figure, and changes the port 2f to the port 2e.
, and shut off from drain port 2g. As a result, some of the oil in port 2e is removed from port 2f and bleed 9, but feedback pressure is generated within circuit 10. This feedback pressure increases as the rotational speed of the oil pump 1 increases, and reduces the eccentricity (capacity) of the oil pump 1 via the actuator 6. Thus, the capacity of the oil pump 1 is controlled so that the discharge amount remains constant while the rotational speed is above a certain value, thereby preventing an increase in power loss of the engine due to discharge of more oil than necessary.

Next, when the line pressure P _L in the circuit 7 fluctuates,
Using this as the source pressure, the pressure modifier valve 3
Naturally, the engine load signal pressure within the circuit 12 produced by the engine load signal pressure will also be varied. Therefore, this fluctuation is absorbed by the accumulator piston 5a stroke between the left half position in the figure and the right half position in the figure in cooperation with the orifice 14, and the circuit 1
The engine load signal pressure within 2 does not change. Therefore, fluctuations in the line pressure P _L controlled by the engine load signal pressure are not amplified, and the line pressure control described above can be performed accurately.

It goes without saying that the invention can also be applied to a system in which a pilot valve is provided using the line pressure as the source pressure, and its output circuit is connected to the duty solenoid 4 and the port 3d.

(Effects of the Invention) As described above, the line pressure control device of the present invention is provided by connecting the accumulator 5 to the circuit 12 that guides the engine load signal pressure to the pressure regulator valve 2, so that the line pressure P _L can be controlled. Accumulator 5 detects fluctuations in engine load signal pressure due to fluctuations.
This can prevent fluctuations in line pressure P _L from being amplified, and it is possible to accurately execute the requested line pressure control.

[Brief explanation of the drawing]

The drawing is a hydraulic circuit diagram showing an embodiment of the line pressure control device of the present invention. 1... Oil pump, 2... Pressure regulator valve, 3... Pressure modifier valve,
4... Duty solenoid, 5... Accumulator, 7... Line pressure, 12... Engine load signal pressure circuit.

Claims (1)

[Scope of Claims] 1. A pressure regulator valve that adjusts the pressure of oil from the oil pump to a line pressure corresponding to the engine load signal pressure in response to the engine load signal pressure; In a line pressure control device for an automatic transmission comprising a pressure modifier valve that produces an engine load signal pressure, an accumulator is provided connected to a circuit that leads the engine load signal pressure to the pressure regulator valve. A line pressure control device for an automatic transmission characterized by: