JPH065098B2 - Automatic transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic transmission, and more particularly to an accumulator device for a hydraulic system thereof.

(Prior Art) Conventionally, an accumulator device for such an automatic transmission is, for example, as shown in FIG. 6 (“Automatic Transaxle RN3 FOIA Type Maintenance Manual” January 1982, Nissan Motor Co., Ltd.). Issue, page 73). This conventional accumulator device is shown in FIG.
A pressure receiving chamber 16 defined by the cylinder member 12 and the piston member 14 communicates with an oil passage 18 for sending a hydraulic pressure for engaging a friction engagement device (not shown), and the pressure receiving chamber with respect to the piston member 14 A return spring 22 is housed in the reaction force chamber 20 defined between the cylinder member 12 and the opposite side of the reaction chamber 16. The hydraulic pressure generated to engage the frictional engagement device is introduced into the pressure receiving chamber 16 of the accumulator device 10 and gradually rises while moving the piston member 14 against the spring force of the return spring 22. The compounding device is also gradually tightened. By this action, the driving part and the driven part gradually shift from the relative rotation to the connection integrated rotation before and after the friction engagement device is engaged. The torque fluctuation rate is reduced, and so-called select shock of a vehicle having a so-called automatic transmission can be reduced.

(Problems to be Solved by the Invention) However, in such a conventional automatic transmission, a load is generated which is substantially linear with respect to the deflection (a rate of change of the load is always positive). -A return spring with a flexure characteristic was used to control the rise of hydraulic pressure by utilizing the flexure to reduce shock. In this case, if the length of the spring is increased to sufficiently reduce the select shock of the vehicle, a large space for accommodating the spring is required, which not only limits the mountability but also the clutch connection time for the select operation. There was a problem that was too long.

On the other hand, it is conceivable to set a large piston pressure receiving area of the accumulator in addition to the spring for quick selection operation, but this also requires a large space for accommodating the piston as in the above case, which limits the mountability. It has a problem that it occurs.

That is, the spring constant, spring length, spring length,
Only by selecting the pressure receiving area of the accumulator, it was not possible to satisfy both the reduction of select shock and the quick select operation.

(Means for Solving the Problems) Therefore, the inventors of the present invention have made extensive studies, and as a result, by providing the accumulator spring with a specific non-linear spring characteristic that is practically used in a diaphragm spring or the like, I got the idea that I could solve the problem. That is, the present invention is a gear transmission mechanism having a plurality of gear stages,
A plurality of friction engagement devices; and a hydraulic system that selectively operates the friction engagement devices to selectively shift the gear transmission mechanism, the hydraulic system including the friction engagement devices and the hydraulic system. In an automatic transmission having an accumulator device interposed between a power source and an orifice recollected between the accumulator device and the hydraulic pressure source, the accumulator device includes a cylinder member and a cylinder member. A piston member that is fitted to define the pressure receiving chamber and the reaction force chamber in the cylinder, and the load-deflection characteristic until the pressure in the pressure receiving chamber increases from zero and reaches a completely constant value, The spring member housed in the reaction force chamber is configured to have a non-linearity in which the rate of change of the load with respect to the deflection is reduced from positive to negative at least once and then becomes positive again.

(Operation) The driver can selectively operate the plurality of friction engagement devices by switching the valve of the oil system, and thus the gear transmission mechanism having the plurality of gear stages can be selectively operated. Specifically, the flow rate of the high-pressure hydraulic oil supplied from the oil passage on the hydraulic pressure source side upstream of the orifice is regulated by the orifice and then sent to the pressure receiving chamber of the accumulator device and the friction engagement device. Next, the hydraulic pressure of the hydraulic oil continuously rises and increases by deforming the spring member as the piston member of the accumulator device moves, and the relative rotational speed between the drive part and the driven part of the friction engagement device increases. Becomes smaller continuously, which can reduce the select shock of the vehicle as described above.

On the other hand, as the relative rotational speed between the driving friction material and the driven friction material of the friction engagement device decreases, the torque of the transmission output shaft increases, but as shown in FIG. Since the dynamic friction coefficient μ increases as the relative rotation speed approaches zero, the output shaft torque becomes excessive and an attempt is made to cause a large select shock.

On the other hand, the load-deflection characteristic of the spring member is such that the rate of change of the load with respect to the deflection decreases at least once from positive to negative until the pressure in the pressure receiving chamber increases from zero and reaches a completely constant value. Because of the non-linearity that becomes positive, the engagement hydraulic pressure of the friction engagement device temporarily decreases corresponding to the temporary decrease of the reaction force applied to the piston member. Therefore, even if the dynamic friction coefficient μ increases as described above, it can be canceled by reducing the engaging hydraulic pressure in this way, and the output shaft torque as a whole can be prevented from becoming excessive. As a result, the select shock can be effectively reduced even if the rising speed of the hydraulic pressure is increased, and a quick select operation can be realized and the operability of the vehicle can be improved.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 is a diagram showing an automatic transmission according to an embodiment of the present invention. The same parts as in the conventional case are designated by the same reference numerals.

First, the structure will be described. In FIG. 1, reference numeral 10 indicates an oil passage between an upper friction engagement device and an oil pressure source lower than the drawing.
An accumulator device is provided in the middle of 18, and a one-way orifice 23 is provided in an oil passage 18 between the accumulator device 10 and a hydraulic pressure source. The accumulator device 10 has a cylinder member 12, in which a piston member 14 which is slidable and whose circumference is sealed by a seal member 13 is fitted.
Defines a pressure receiving chamber 16 communicating with the oil passage 18 between the cylinder member 12 and the upper portion in the figure. The piston member 14 defines a reaction force chamber 20 having a drain port 21 between the piston member 14 and the lower portion of the cylinder member 12 in the drawing, and a snap ring 24 is fitted to the cylinder member 12 on the side of the reaction force chamber 20. I'm wearing it. The boss portion 14a formed on the axial portion of the piston member 14 and the snap ring 2
A disc spring (spring member) 32 is interposed between the disc springs 4 and 4.
As shown in FIG. 2, the disc spring 32 has a load-deflection characteristic such that the temporary load decreases while the deformation amount increases. Specifically, the disc spring 32 has a rate of change in load with respect to deflection (a load with respect to an increase in deflection of a unit amount) until a high hydraulic pressure is introduced into the pressure receiving chamber 16 and the hydraulic pressure increases from zero until it reaches a completely constant value. Has a non-linear load-deflection characteristic in which the amount of change of () changes from positive to negative at least once and then becomes positive again. One way orifice
As shown in FIG. 1, 23 has an orifice 26 provided in the oil passage 18 and a check valve 28 provided in the bypass oil passage 19 of the oil passage 18. The drive source, accumulator device
10, the oil passage 18, and the one-way orifice 23 constitute a hydraulic system together with various valves and oil tanks (not shown).

Next, the operation will be described.

A driver selects a plurality of friction engagement devices by operating the shift position of a shift lever (not shown) from the neutral (N) or parking (P) position to, for example, the drive (D) position and switching a manual valve (not shown). The gear shift mechanism having a plurality of shift speeds can be selectively shifted. More specifically, in order to newly engage the friction engagement device, high-pressure hydraulic oil is supplied from the upstream (downward in FIG. 1) of the one-way orifice 23 of the oil passage 18 to the downstream (upward in FIG. 1). At this time, the check valve 28 is closed and the flow rate of the working oil is determined only through the orifice 26, and is sent to the pressure receiving chamber 16 of the accumulator device 10 and the friction engagement device downstream of the accumulator device 10. Next, the hydraulic pressure of the hydraulic oil rises continuously by deforming the disc spring 32 as the piston member 14 of the accumulator device 10 moves, and
The output shaft torque of the gear shift mechanism increases as indicated by the solid diagonal lines in the figure. At this time, the relative engagement speed of the driving friction material and the driven friction material of the friction engagement device is continuously reduced, so that the friction engagement device is actuated, and the gear shift mechanism is actuated to shift the output shaft thereof. The variable speed rotation can be taken out from.

On the other hand, the friction transmission torque T of the friction engagement device is generally expressed by the following equation.

T = p × A × μ × D where p is the engagement hydraulic pressure, A is the friction material pressure receiving area, μ is the dynamic friction coefficient of the friction material, and D is the average diameter of the friction material.

Further, as shown in FIG. 5, the dynamic friction coefficient μ tends to increase as the relative rotational speed v between the driving friction material and the driven friction material approaches zero. Therefore, when the relative rotation speed v becomes small, the friction transmission torque T also exceeds a predetermined value and becomes excessive, so that the select shock is to be increased. In order to prevent such an increase in select shock, it is necessary to reduce the engaging hydraulic pressure p and suppress the friction transmission torque T from the above equation.

On the other hand, as shown in FIG. 2, the disc spring 32 increases the pressure of the pressure receiving chamber 16 from zero until it reaches a completely constant value.
Since the change of the load with respect to the flexure decreases from positive to negative once, and then becomes positive again, since it has a non-linear load-deflection characteristic, the pressure of the pressure receiving chamber 16 in the region where the output shaft torque becomes excessive. By making the region in which the torque decreases once correspond, as shown by the dotted line in FIG. 3, even if the dynamic friction coefficient μ increases as described above, it can be offset by reducing the engaging hydraulic pressure p in this way. It is possible to prevent the output shaft torque T from becoming excessive as a whole. Then, as indicated by the broken line in FIG. 4, the relative rotational speed v is set to zero before the region where the output shaft torque T increases again, and the driving friction material and the driven friction material of the friction engagement device are separated from each other. Directly connect and finish the select operation. By doing so, even if the rising speed of the hydraulic pressure is increased, the select shock can be effectively reduced, a quick select operation can be realized, and the operability of the vehicle can be improved.

(Effects of the Invention) As described above, according to the present invention, the deflection force in the reaction chamber of the accumulator is increased until the pressure in the pressure receiving chamber of the accumulator increases from zero and reaches a completely constant value. By accommodating a spring member having a non-linear load-deflection characteristic in which the rate of change of load decreases from positive to negative at least once and then becomes positive again, it is possible to effectively select shock even if the rising speed of hydraulic pressure is increased. Can be reduced, a quick select operation can be realized, and the operability of the vehicle can be improved.

[Brief description of drawings]

1 is a sectional view showing an accumulator portion of a hydraulic system of an automatic transmission according to an embodiment of the present invention, FIG. 2 is a load-deformation characteristic diagram of a disc spring 32 shown in FIG. 1, and FIG. 3 is an output. FIG. 4 is a graph showing the relationship between the axial torque and time, FIG. 4 is a graph showing the relationship between the relative rotational speed of the friction material of the friction engagement device and time, and FIG. 5 is the dynamic friction coefficient μ of the friction member of the friction engagement device. And a relative rotational speed v of the friction member thereof, and FIG. 6 is a sectional view showing an accumulator portion of a hydraulic system of a conventional automatic transmission. 10 …… Accumulator device, 12 …… Cylinder member, 13 …… Seal member, 14 …… Piston member, 16 …… Pressure receiving chamber, 18 …… Oil passage, 19 …… Bypass oil passage, 20 …… Reaction chamber 21 …… Drain port, 23 …… One way orifice, 24 …… Snap ring, 26 …… Orifice, 28 …… Check valve, 32 …… Disc spring (spring member).

Claims (1)

[Claims] 1. A gear shift mechanism having a plurality of shift stages, a plurality of friction engagement devices, and a hydraulic system for selectively operating the friction engagement devices to selectively shift the gear shift mechanism. This hydraulic system is provided with an accumulator device (10) interposed between the friction engagement device and a hydraulic pressure source, and between the accumulator device (10) and the hydraulic pressure source. In an automatic transmission having an orifice (26), the accumulator device (10) includes a cylinder member (12),
This cylinder member (12) fits inside the cylinder chamber
(16) and the reaction force chamber (20) define the piston member (14) and the load-deflection characteristic until the pressure in the pressure receiving chamber (16) increases from zero and reaches a completely constant value. In the meantime, the reaction force chamber (20) is set as a non-linearity in which the rate of change of load with respect to deflection is reduced from positive to negative at least once and then becomes positive again.
An automatic transmission, comprising: a spring member (32) housed in the.