JPS5922099B2 - Automatic transmission hydraulic control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control system for an automatic transmission for a vehicle, and particularly relates to improvements in the transmission characteristics during downshifting.

In an automatic transmission T for a vehicle that includes a hydraulic torque converter and a gear transmission mechanism equipped with a plurality of frictional engagement devices for obtaining several gears, the frictional force is changed depending on the driving state of the vehicle. The operation of the engagement device is switched between various types, and the gear transmission mechanism is automatically controlled to a transmission state most suitable for the driving condition of the vehicle at that time.

Switching control of such a frictional engagement device is normally performed by a hydraulic control device, and this hydraulic control device includes a throttle oil pressure that changes depending on the amount of depression of the accelerator pedal, that is, the intake throttle opening, and a control that changes depending on the vehicle speed. A gear shift valve is built in that is switched depending on the equilibrium relationship between the governor oil pressure and the gear speed of the gear transmission mechanism based on the comparative relationship between the throttle oil pressure and the governor oil pressure, that is, the amount of accelerator pedal depression and the vehicle speed. It has become.

In this case, the speed change valve has a first switching position in which one low gear friction engagement device is connected to the line oil pressure supply path and one high gear friction engagement device is connected to the drain oil path; It is configured to be switched between a second switching position in which the stage friction engagement device is connected to the line oil pressure supply oil passage and the low speed stage friction engagement device is connected to the drain oil passage, In addition, in order to provide an appropriate overlap in switching the hydraulic pressure supply to the frictional engagement device for low speed gear and the frictional engagement device for high speed gear, and to smoothly perform gear changeover, the frictional engagement device for low speed and high gear speed is provided. An accumulator for a low speed stage and an accumulator for a high speed stage are connected to each of the hydraulic pressure supply paths.

FIG. 1 shows that when switching the hydraulic pressure supply between the frictional engagement device for low gear and the frictional engagement device for high gear using a hydraulic pressure supply path equipped with such an accumulator, especially when the hydraulic pressure is switched from the high gear to the low gear, FIG. 7 is a diagram showing an example of changes in oil pressure supplied to each frictional engagement device, corresponding engine rotational speed, and transmission output shaft torque when a shift is performed.

In this case, curve A in the hydraulic diagram shows the course of the hydraulic pressure supplied to the high-speed friction engagement device (...clutch),
Curve B shows the course of oil pressure supplied to the low-speed frictional engagement device (low clutch).

In this case, a portion a of curve A corresponds to the operating range of the high speed accumulator, and a portion b of curve B corresponds to the operating range of the low speed accumulator.

Further, the 0 point is the point at which the bike clutch is substantially disengaged, and the d point is the point at which the low clutch starts to be substantially engaged.

-・Between the release of the clutch and the engagement of the low clutch, the first
When the appropriate timing as shown in the figure is maintained, the engine speed gradually increases after the bike clutch is released, and when the engine speed reaches the speed corresponding to the low gear ratio relative to the vehicle speed at that time, the low clutch is engaged. As a result, negative torque is not generated on the output shaft, and a relatively smooth downshift is achieved with output shaft torque fluctuations as shown in the figure.

However, even in this case, the output shaft torque fluctuation is quite large, and the feeling during downshifting is not necessarily satisfactory. Furthermore, the timing of release and engagement between both frictional engagement devices is It shifts as shown in Figure 2.
That is, if the low clutch is engaged too quickly with respect to the bike clutch being released, the output shaft torque momentarily becomes a large negative value as shown in the figure, resulting in an indeterminate shift shock.

Further, a force ζ not shown in the drawings conversely, if the engagement of the low clutch is too delayed with respect to the release of the bike clutch, engine revving will occur during gear shifting.

In general, the operating performance of an accumulator, especially its set pressure, is determined from the perspective of alleviating the shift shock when engaging a bike clutch from a low gear to a high gear, and the set pressure is set to sufficiently transmit the torque that the clutch should transmit. is set to a value that is possible.

Therefore, oil is drained from the bike clutch at a high set pressure even during downshifting, so during the operation of the accumulator, that is, in the region a of curve A in Fig. 1,
The bike latch is engaged and no slippage occurs.

Therefore, in this case, only the timing relationship between the 0 point and the d point is the condition that affects the smoothness of the downshift, but the timing between these two points must be set appropriately for each actual hydraulic control device. This is extremely difficult from the viewpoint of manufacturing accuracy, and the timing also changes depending on the vehicle speed at the time of downshifting and the engine output torque at that time, that is, the throttle opening. It is also extremely difficult to maintain properly.

SUMMARY OF THE INVENTION An object of the present invention is to address the above-mentioned problems in the hydraulic leg system of an automatic transmission, and to provide a hydraulic control system that is improved in terms of shift characteristics during downshifts.

According to the present invention, this object includes a frictional engagement device for a low gear and a frictional engagement device for a high gear, and shifts the gear by switching engagement between these two frictional engagement devices. In a hydraulic control device for a gear shifting mechanism for an automatic transmission, the friction engagement device for low gear is connected to a line oil pressure supply oil passage, and the friction engagement device for high gear is connected to a drain oil passage. A switching operation is performed between a first switching position and a second switching position in which the high-speed gear friction engagement device is connected to a line oil pressure supply oil path and the low-speed gear friction engagement device is connected to a drain oil path. a speed change valve, a low speed accumulator and a high speed accumulator connected to the hydraulic pressure supply oil passages of the low speed and high speed frictional engagement devices, respectively; a first flow resistance means for applying flow resistance to an oil passage for discharging oil from the high speed friction engagement device during a downshift when the high speed gear accumulator is switched to the first switching position; a second flow resistance means that provides flow resistance to an oil passage supplying hydraulic pressure to the pressure chamber; and a second flow resistance means that is controlled by the hydraulic pressure of the low-speed friction engagement device during the downshift, and the hydraulic pressure is controlled by the low-speed friction engagement device. The hydraulic pressure of the high speed friction engagement device increases the resistance of the first and second flow resistance means under the operation of the high speed accumulator until a predetermined level is reached that results in substantial engagement of the first and second flow resistance means. The first pressure is set to a value that causes the frictional engagement device for the high speed gear to slip, and when the hydraulic pressure of the frictional engagement device for the low gear reaches the predetermined level, the first pressure and the second pressure are and hydraulic control means for causing the hydraulic pressure of the high speed friction engagement device to be significantly lower than the first pressure under the operation of the high speed accumulator by modifying at least one of the flow resistance means. This is achieved by a characteristic hydraulic control device.

FIG. 3 is a hydraulic circuit diagram showing the main parts of a hydraulic control device incorporating one embodiment of the present invention.

In the figure, 1 is a bike clutch, 2 is a low clutch, and these are line hydraulic pressure (pf) supplied via oil line 3.
is selectively supplied via the transmission valve 4 and the oil passage 5 or 6, or the supplied hydraulic pressure is supplied to the oil passage 5 or 6 and the transmission valve 4.
The oil is then discharged to a drain oil path connected to the drain port of the speed change valve.

The speed change valve 4 includes a valve element 8 which is pushed upward in the figure by a compression coil spring 7, and the lower end of the valve element receives throttle oil pressure (PTH) through a port 9, and the upper end receives the governor through a port 10. Hydraulic pressure (PGO) is supplied, and switching is performed based on the equilibrium relationship between the governor oil pressure and the throttle oil pressure.

The line oil pressure supplied to port 11 via oil passage 3 is supplied to bike clutch 1 via port 12 and oil passage 5 when the transmission valve is in the downward switching position as shown in the figure, and when the transmission valve is in the upward switching position. When in the switching position, the oil is supplied to the low clutch 2 via the port 13 and the oil path 6.

Furthermore, when the gear shift valve is in the downward switching position, the low clutch 2 is drained directly from the oil passage 6 and port 13 to the drain oil passage 15 via the drain port 14; When in the switching position, oil passage 5 and port 12 are connected to port 16, from which water is drained via oil passage 17 and a control valve (downshift timing valve) 18, which will be explained in detail below. .

The control valve 18 includes a valve element 20 pushed upward in the figure by a compression coil spring 19, and the valve element is switched in the vertical direction to control communication or isolation between the ports 21 and 22. It has become.

When the valve element 20 is in the upward switching position as shown, the ports 21 and 22 are closed, and therefore the drain oil passage of the bike clutch is a one-way connection that leads from the oil passage 17 through the port 21 to the drain oil passage 23. When the valve element 20 is switched downward, the ports 21 and 22 communicate with each other, and at this time, the drain oil passage of the drain comes to communicate with the two drain oil passages 23 and 24.

Low clutch hydraulic pressure supplied to a port 26 via an oil passage 25 connected to the oil passage 6 is applied to the upper end of the valve element 20.

Further, in this embodiment, throttle oil pressure is supplied to the port 27, and a force that increases according to the accelerator opening is applied upward in the figure to the valve element 20. ing.

28 and 29 are accumulators for high-speed and low-speed stages connected to the oil passages 5 and 6, respectively, and their pistons 30 and 31 are compressed by the spring force of the compression coil springs 32 and 33 and their back pressure chambers 34 and 35. back pressure is applied by hydraulic pressure supplied to the

In the illustrated embodiment, the oil passages 5 and 6 are each provided with a parallel circuit of a throttle 36, 37 and a check valve 38, 39, and back pressure chambers of the high speed and low speed accumulators are provided. 34.35 are each provided with a parallel circuit of a throttle element 42.43 and a check valve 44.45.

The drain oil passage connected to the drain port 14 of the speed change valve 4 is provided with a throttling element 46, and the drain oil passage 23 and 2 connected to the ports 21 and 22 of the control valve 18 are provided with a throttling element 46.
4 are connected to aperture elements 47 and 48, respectively.

In a hydraulic control device including a hydraulic circuit having such a configuration, when an upshift is performed in which the low clutch 2 is released and the high clutch 1 is engaged, the hydraulic pressure of the low clutch 2 is transferred to the oil passage 6 including the check valve 39. from the drain oil passage 15 through ports 13 and 14. .

The release timing of the low clutch and the set pressure of the accumulator 29 are determined by the throttle element 46.4.
3 aperture and the piston 31 of the accumulator 229
It is set to a preferable state by the land difference, etc.

On the other hand, at this time, the bike clutch 1 is connected to the port 11 from the oil passage 3.
and 12, line hydraulic pressure is supplied through the oil path 5 including the throttle element 36, and the timing of engaging the bike clutch and the set pressure of the accumulator 28 are determined by the land difference between the throttle element 36, the piston 30 of the accumulator 28, etc. can be set to a preferable value by appropriately designing.

In addition, the accumulator 28 at the time of such an upshift
The set pressure is set to a sufficiently high pressure that does not cause clutch slippage, so as to soften the shift shock when the bicycle clutch is engaged and to transmit sufficient driving torque after the high-flanch engagement.

On the contrary, when a downshift is performed in which the low clutch 1 is released and the low clutch 2 is engaged, the oil pressure of the motorcycle clutch 1 is transferred from the oil passage 5 including the check valve 38 through the ports 12 and 16. Further, the oil is drained from the oil passage 17 through a drain oil passage passing through a control valve 18.

The timing for releasing the bike latch and the set pressure of the accumulator 28 are determined by the throttle elements 47, 48 and 42.
, the land difference in the piston 30 of the accumulator 28, and the switching operation of the control valve 18, that is, its port 2.
It is controlled by changes in the low clutch oil pressure that acts on 6.

Also, at this time, the port 1- is connected to the low clutch 2 from the oil passage 3.
11 and 13, line hydraulic pressure is supplied via the oil passage 6 including the throttle element 37.

The timing of engagement of the low clutch and the set pressure of the accumulator 29 are appropriately adjusted by the land difference between the throttle element 37 and the piston 31 of the accumulator 29.

FIG. 4 is a line showing the fluctuations in oil pressure, engine speed, and output shaft torque in the bike clutch and low clutch achieved during downshift by the hydraulic control device according to the present invention, similar to FIG. 1 or 2. It is a diagram.

In this case, the oil pressure in the accumulator operating region of the bike clutch oil pressure curve A, that is, region a, is the same as that of the throttle element 42.
．． Aperture of 47 and piston 3 of accumulator 28
By appropriately determining the land difference, etc. at 0VrC, the pressure is set to produce an appropriate amount of slip in the bike clutch, and this causes an appropriate amount of slip in the bike clutch immediately after the shift valve 4 is switched, which causes the engine to The rotational speed increases more gradually when a moderate load is applied.

When the engine speed increases to a speed corresponding to the low gear ratio at the current vehicle speed, the low clutch is engaged.

Therefore, in this case, the output shaft torque rarely decreases to zero upon downshifting, and as shown in the figure, the output shaft torque shifts to the low gear torque with relatively small torque fluctuations.

By keeping the bike clutch in a slipping state for a relatively long period of time from the beginning of the downshift until the low clutch oil pressure rises, smooth downshifts with small torque fluctuations can be achieved. Furthermore, in this case, as can be understood from the absence of the 0 point in Figures 1 and 2, the degree of influence that the operating timing between the two frictional engagement devices has on the smoothness of the shift is different from that in the conventional case. This is significantly alleviated compared to the case of a hydraulic control device.

Furthermore, in the case of the present invention, in the process of supplying hydraulic pressure to the low clutch 2, when the idle displacement of the low clutch piston ends and the hydraulic pressure that is to be opposed by the accumulator 29 begins to be formed in the oil passage 6 (see e in FIG. 4). point), which causes the control valve 18 to switch downwards and ports 21 and 22 to
Communication will take place.

From this moment (corresponding to point f in FIG. 4)...the flow path resistance of the drain oil path of the engine clutch is significantly reduced, and the bike clutch oil pressure is quickly reduced to substantially zero.

Therefore, according to the present invention, by slipping the bike clutch during downshifting, it is possible to perform a smooth gear change with small torque fluctuations, and also to ensure that the timing when the low clutch substantially engages is captured, so that the bike clutch can be shifted smoothly. It is possible to release the slip, avoid unnecessary slip operation of the bike latch, and ensure the necessary life of the bike latch.

As is clear from the above description, in the embodiment shown in FIG. 3, the first flow resistance means that provides flow resistance to the oil passage for discharging oil from the high speed friction engagement device during downshifting is Throttle elements 47 and 48 are connected in parallel to each other, and the second flow resistance means that provides flow resistance to the oil passage that supplies hydraulic pressure to the back pressure chamber of the high speed accumulator during downshifting is the throttle element 42. .

Further, in this embodiment, the hydraulic control means is a control valve 18.
is controlled by the oil pressure of the low gear friction engagement device during downshifting, and the flow resistance of the first flow resistance means is controlled by the oil pressure of the low gear friction engagement device until the oil pressure reaches a predetermined level that causes substantial engagement of the low gear friction engagement device. While the throttle element 48 forming a part of the flow resistance means is kept in a closed state, the resistance value of the first and second flow resistance means is changed by the hydraulic pressure of the high speed friction engagement device to the high speed stage under the operation of the high speed accumulator. When the hydraulic pressure of the frictional engagement device for low speed reaches the predetermined level, the second and second flow resistance means i.e. in this case said first flow resistance means;
Throttle elements 47 connected in parallel to each other constitute the same.
48 from a state in which only one of them is opened to a state in which both of them are opened, and by modifying this to reduce the flow resistance of the first flow resistance means, the frictional engagement device for high speed stage is modified. The hydraulic pressure is significantly lowered from the first pressure under the operation of the high-speed stage accumulator.

FIG. 5 is a hydraulic circuit diagram showing the main parts of a hydraulic control device incorporating another embodiment of the present invention.

In Fig. 5, the parts corresponding to those in Fig. 3 are shown in Fig. 3.
They are indicated by the same reference numerals as in the figure.

In this embodiment, the control valve 18 controlled by the low clutch oil pressure is connected to the high speed accumulator 28 in order to significantly reduce the bike clutch oil pressure at point f corresponding to point e in FIG. The flow path resistance of the back pressure oil path is switched and controlled in steps.

That is, until the low clutch oil pressure reaches point e, the control valve 18
The valve element 20 is in a position where it cannot be switched upward as shown in the figure, and the hydraulic pressure supplied to the back pressure chamber of the accumulator 28 is restricted by the line hydraulic pressure supplied from the oil passage 49 passing through the ports 50 and 51 of the control valve 18. It is supplied through the parallel paths of elements 52 and 53, but when the low clutch oil pressure reaches point e, the valve element 20 of the control valve 18 is switched downward in the figure, and the ports 50 and 51 are cut off. Thereafter, the hydraulic pressure supplied to the back pressure chamber 34 of the accumulator 28 is supplied only through the throttling element 52, and the degree of throttling of the back pressure supply oil path is significantly increased.

Therefore, the set pressure of the accumulator 28 is significantly lower than at this time (point f).

As is clear from the above explanation, in the embodiment shown in FIG. The second flow resistance means, which is a throttle element 54 provided in the passage 17 and provides flow resistance to the oil passage that supplies hydraulic pressure to the back pressure chamber of the high speed accumulator during downshifting, is a throttle element 54 that is connected in parallel with each other. Elements 52 and 53.

Further, in this embodiment, the hydraulic control means is a control valve 18.
and the second flow resistance means is controlled by the oil pressure of the low gear friction engagement device during downshifting, and the second flow resistance means is controlled until the oil pressure reaches a predetermined level that causes substantial engagement of the low gear friction engagement device. With both of the throttling elements 52 and 53 open, the resistance values of the first and second flow resistance means are adjusted so that the hydraulic pressure of the high-speed friction engagement device is at high speed under the operation of the high-speed accumulator. The first pressure is set to a value that causes the gear frictional engagement device to slip, and when the hydraulic pressure of the low gear frictional engagement device reaches a predetermined level, the first and second flow resistance means , in this case said second flow resistance means, constituting the throttling elements 52 connected in parallel with each other.
．． By modifying this from a state in which both of the throttle elements 53 are open to a state in which only one throttle element 52 is open, and by modifying the second flow resistance means to increase the flow resistance, the high speed stage is The hydraulic pressure of the frictional engagement device is significantly lowered from the first pressure under the operation of the high-speed stage accumulator.

Furthermore, as is clear from the comparison of the two embodiments shown in FIGS. 3 and 5 above, the hydraulic control means acts on at least one of the first and second flow resistance means to modify the flow resistance thereof. By doing so, when the oil pressure of the low-speed friction engagement device reaches the predetermined level, the oil pressure of the high-speed friction engagement device is lowered under the operation of the high-speed accumulator. It is possible to achieve an operation in which the first pressure, which causes the frictional engagement device for high speed gear to slip, is significantly lowered and the frictional engagement device for high speed gear is substantially released.

However, it will of course be clear that embodiments may also be implemented in which hydraulic control means are provided which respectively act on both said first and second flow resistance means.

This is obtained simply by superposing the embodiment of FIG. 3 and the embodiment of FIG.

Although the present invention has been described in detail with respect to specific embodiments above, it will be appreciated by those skilled in the art that the present invention is not limited to such embodiments, and that various modifications can be made within the scope of the present invention. It would be obvious for

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing characteristics during downshifting in a conventional hydraulic control device. FIG. 3 is a hydraulic circuit diagram showing the main parts of a hydraulic control device incorporating one embodiment of the present invention. FIG. 4 is a diagram showing the characteristics of the hydraulic control system according to the present invention during downshift. FIG. 5 is a hydraulic circuit diagram showing the main parts of a hydraulic control device incorporating another embodiment of the present invention. 1... Bike clutch, 2... Low clutch, 4... Speed valve, 18... Control valve (
downshift timing pulp), 28... accumulator for low speed stage, 29... accumulator for high speed stage.

Claims (1)

[Claims] 1. An automatic transmission that includes a frictional engagement device for a low gear and a frictional engagement device for a high gear, and switches gears by switching the engagement between these two frictional engagement devices. In a hydraulic control device for a gear transmission mechanism, the first friction engagement device connects the low speed gear friction engagement device to a line oil pressure supply oil path and connects the high speed gear friction engagement device to a drain oil path. a transmission valve that operates to switch between a switching position and a second switching position in which the high speed gear friction engagement device is connected to a line oil pressure supply oil path and the low speed gear friction engagement device is connected to a drain oil path; ,
A low speed accumulator and a high speed accumulator connected to the hydraulic pressure supply oil passages of the low speed and high speed friction engagement devices, respectively, and the shift valve are moved from the second switching position to the first switching position. a first flow resistance means that applies flow resistance to an oil path for discharging oil from the high-speed friction engagement device during a downshift, and a first flow resistance means that applies flow resistance to an oil path for discharging oil from the high-speed friction engagement device; a second flow resistance means that provides flow resistance to an oil passage supplying oil, and a second flow resistance means that is controlled by the oil pressure of the low speed friction engagement device during the downshift, and the oil pressure is controlled by the oil pressure of the low speed friction engagement device to substantially increase the flow resistance of the low speed friction engagement device. Until a predetermined level is reached at which engagement occurs, the
and the resistance value of the second flow resistance means is set to a first pressure that causes the oil pressure of the high speed friction engagement device to slip in the high speed friction engagement device under the operation of the high speed accumulator. When the hydraulic pressure of the frictional engagement device for the low gear reaches the predetermined level, the frictional engagement device for the high gear A hydraulic control device comprising: hydraulic control means for significantly lowering the hydraulic pressure of the coupling device from the first pressure under the operation of the high-speed stage accumulator. 2. In the hydraulic control device according to claim 1, the hydraulic control means includes a control valve that is controlled by the hydraulic pressure of the low speed friction engagement device to control the first flow resistance means. The hydraulic control is characterized in that the trundle valve is configured to reduce the flow resistance of the first flow resistance means when the oil pressure of the low speed friction engagement device reaches the predetermined level. Device. 3. In the hydraulic control device according to claim 1, the hydraulic control means includes a control valve that is controlled by the hydraulic pressure of the low-speed friction engagement device to control the second flow resistance means. , wherein the control valve is configured to increase the flow resistance of the second flow resistance means when the oil pressure of the low-speed friction engagement device rises to the predetermined level.