JPS5822654B2 - 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 at the highest speed gear.

In an automatic transmission 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 changes depending on the driving state of the vehicle. The operation of the engagement device is automatically switched and the gear transmission mechanism is controlled to the most suitable speed change state for the vehicle driving condition at that time.

Switching control of such a frictional engagement device is normally performed by a hydraulic control device, and this hydraulic control device has a throttle hydraulic 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 of the governor oil pressure, and the gear speed of the gear transmission mechanism is selected 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. ing.

Therefore, even if the amount of depression of the accelerator pedal is a certain amount, if the vehicle speed is at a relatively low value,
In the comparative relationship between throttle oil pressure and governor oil pressure, the throttle oil pressure is in a relatively higher state than the governor oil pressure, and the gear transmission mechanism is switched to a lower speed gear, whereas the vehicle speed is at a relatively higher value. In the comparative relationship between the throttle oil pressure and the governor oil pressure, the throttle oil pressure is relatively lower than the governor oil pressure, and the gear transmission mechanism is switched to a higher speed gear.

In conventional automatic transmissions, which select the gear position of the gear transmission mechanism based on the contrast between the throttle oil pressure and the governor oil pressure, even when the vehicle speed is at a fairly low value, the accelerator pedal is not depressed enough. Therefore, under operating conditions in which the throttle oil pressure is sufficiently small compared to the governor oil pressure, a situation occurs in which the gear transmission mechanism is switched to a high speed gear.

In particular, when an overdrive mechanism is incorporated into a part of the gear transmission mechanism, under such conditions, the vehicle will be driven by the overdrive gear even though the vehicle speed is at a fairly low value.

When a vehicle is operated in such a high speed gear change state, sufficient acceleration performance cannot be obtained, especially when the total gear ratio at the highest speed gear is small, such as in an automatic transmission with an overdrive device. In addition, when the engine brake is activated, drivability deteriorates because sufficient power cannot be obtained, and at the same time, the engine is operated in a low rotation and high torque range, causing harmful components in the gas to be removed. In particular, there is a problem in that it becomes difficult to control HC.

The present invention has been made to solve this problem, and when the vehicle speed is below a predetermined level, regardless of the amount of depression of the accelerator pedal, the automatic transmission will shift to the highest speed gear, especially in an automatic transmission incorporating an overdrive mechanism. The object of the present invention is to provide a hydraulic control device for an automatic transmission which is improved so that it cannot be switched to an overdrive stage.

Such an object, according to the invention, is a hydraulic control device for an automatic transmission comprising a hydraulic torque converter and a gear transmission mechanism with a plurality of frictional engagement devices for obtaining several gear stages. a hydraulic pressure source, a line hydraulic control valve that generates line hydraulic pressure regulated from the hydraulic source, a throttle hydraulic control valve that generates throttle hydraulic pressure according to the intake throttle opening, and a governor hydraulic pressure that corresponds to the vehicle speed. a governor hydraulic pressure control valve that generates the pressure, a manual switching valve that manually switches the speed range, and a plurality of valves that switch the hydraulic pressure supplied to the friction engagement device according to the equilibrium relationship between the AiJ throttle hydraulic pressure and the governor hydraulic pressure. transmission valves, and further, when the governor oil pressure is below a predetermined value, the transmission valve that achieves the highest gear of the transmission valves is held at the low speed side switching position regardless of the value of the throttle oil pressure. In order to achieve this, in addition to each of the above-mentioned components, a passage is provided in the middle of the passage guiding the governor hydraulic pressure to the transmission valve that achieves the highest speed gear among the transmission valves, and is controlled by the governor hydraulic pressure so that the governor hydraulic pressure is below a predetermined value. The transmission valve that achieves the highest gear among the transmission valves has a switching valve that is in a closed state when the governor oil pressure is equal to or higher than a predetermined value, and that is in a communication state when the governor oil pressure is equal to or higher than a predetermined value. element, a piston that receives the throttle oil pressure at one end, and a compression spring interposed between the other end of the valve element and the other end of the piston, and when the throttle oil pressure is less than a predetermined value, it exceeds the throttle oil pressure. and balances the spring force of the compression spring with the governor oil pressure, and when the throttle oil pressure is equal to or higher than a predetermined value, the spring force of the compression spring is exceeded and the throttle oil pressure is balanced with the governor oil pressure. This is achieved by a hydraulic control device such as

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of a hydraulic automatic transmission with an overdrive device.

A more specific structure of such an automatic transmission is illustrated and explained in detail in Japanese Patent Application No. 144926/1982 or No. 159179/1989 filed by the same applicant as the present applicant. If necessary, please refer to the specifications and drawings of these applications.

This automatic transmission includes a torque converter 1, an overdrive mechanism 2, and a gear transmission mechanism 3 with three forward speeds and one reverse speed, and is controlled by a hydraulic control device as shown in FIG.

The torque converter 1 is well known and includes a pump 5, a turbine 6, and a stator 7. The pump 5 is connected to an engine crankshaft 8, and the turbine 6 is connected to a turbine shaft 9.

The turbine shaft 9 forms the output shaft of the torque converter 1, which also serves as the input shaft of the overdrive mechanism 2, and is connected to a carrier 10 of a planetary gear system in the overdrive mechanism.

A planetary pinion 14 rotatably supported by a carrier 10 meshes with a sun gear 11 and a ring gear 15.

A multi-disc clutch 12 is located between the sun gear 11 and the carrier 10.
A one-way clutch 13 is provided, and a multi-disc brake 19 is provided between the sun gear 11 and a housing or overdrive case 16 containing the overdrive mechanism.

The ring gear 15 of the overdrive mechanism 2 is connected to the input shaft 23 of the gear transmission mechanism 3.

A multi-disc clutch 24 is provided between the input shaft 23 and the intermediate shaft 29, and a multi-disc clutch 25 is provided between the input shaft 23 and the sun gear shaft 30.

A multi-disc brake 26 is provided between the sun gear shaft 30 and the transmission case 18.

The sun gear 32 provided on the sun gear shaft 30 is connected to the carrier 3
3. Planetary pinion 34 supported by the carrier, ring gear 35 meshing with the pinion, another carrier 36, planetary pinion 37 supported by the carrier, and ring gear 38 meshing with the pinion in two rows. It constitutes a planetary gear mechanism.

The ring gear 35 in one planetary gear mechanism is connected to the intermediate shaft 29
is connected to.

Further, the carrier 33 in this planetary gear mechanism is connected to a ring gear 38 in the other planetary gear mechanism, and these carrier and ring gear are connected to an output shaft 39.

Further, a multi-disc brake 27 and a one-way clutch 28 are provided between the carrier 36 and the transmission case 18 in the other planetary gear mechanism.

Such a hydraulic automatic transmission with an overdrive device engages or disengages each clutch and brake according to the engine output and vehicle speed by a hydraulic control device, which will be explained in detail below. 0/D) or one reverse speed by manual switching.

Table 1 shows the shift gear position and operating status of clutches and brakes.
Shown below.

Mark ○ here (Engine block) show.

2 is a diagram showing a basic example of the configuration of a hydraulic control circuit included in the hydraulic control device.

Oil pumped up from the oil reservoir 40 by the oil pump 41 is sent to the line oil pressure control valve 42, and generates line oil pressure Pt regulated to a predetermined pressure in the oil passage 43.

This line oil pressure is also supplied to a manual switching valve 44, a throttle oil pressure control valve 45, and a tenant oil pressure control valve 46.

The manual switching valve 44 is used for Barking (P), IJ berth (River,
Neutral (N), D range (D), 2 range (2)
, L range (has a suitable switching position), and the line oil pressure supplied to its input port 43a is switched to its output ports 43b, 43c, 43d, and 4 according to the switching position of the valve.
3e as shown in Table 2.

The throttle oil pressure control valve 45 controls the oil pressure p which increases according to the amount of depression of the accelerator pedal, that is, the opening degree of the intake throttle valve.
th is generated at its output port 50.

The control valve 46 adjusts the line oil pressure to a lower predetermined oil pressure and outputs the tenant oil pressure to its output oil line 51.
The tenant oil pressure generated in the throttle oil pressure control valve is supplied to the transmission valve described below through a switching valve 52 and an oil passage 53, which are connected when the accelerator pedal is depressed by a predetermined amount or more. The function is to hold the switch in one switching position.

Output oil passage 47 connected to port 1-43b of manual switching valve 44
is connected to the clutch 24 (forward clutch), and an oil path 47a branched from the middle thereof is connected to the governor hydraulic control valve 54.

The governor hydraulic pressure control valve generates a governor hydraulic pressure Pgo at its output port 55 in accordance with the vehicle speed.

56 and 57 are a 1st-2nd speed switching valve and a 2nd-3rd speed switching valve, respectively, and 58 is an overdrive control valve.

These switching valves or control valves switch the supply of hydraulic pressure to frictional engagement devices such as clutches and brakes incorporated in the gear transmission mechanism shown in Fig. 1, and move the gear transmission mechanism between various speed stages. It performs a switching action, and is generically referred to as a gear shift valve.

In this embodiment, the overdrive control valve 58 is a transmission valve that achieves the highest speed stage among the speed stages achieved by switching these transmission valves.

The 1-2 speed switching valve 56 includes two valve elements 60 and 61 facing each other in the axial direction via a compression coil spring 59.

The valve element 60 has the sum of the downward pressing force in the figure, which is applied by the spring 59, and the downward pressing force in the figure, which is applied by the throttle oil pressure Pth applied to the port 62 via the oil passage 50a, and the lower end of the valve element 60. Due to the balance with the upward pressing force in the figure given by the governor oil pressure Pgo applied to the port 63 via the oil passage 55a, the position is displaced downward as shown in 56A and in the -L direction as shown in 56B. It is meant to be displaced between positions.

Valve element 61 has ports 64 and 65 thereof connected to manual switching valve 4.
When 4 is switched to L range, the output capo-1-43d
The current line oil pressure is regulated and supplied through the oil passage 49 and the low modulator valve 66, and when this oil pressure is supplied, the valve element 61 is displaced downward in the figure. , serves to forcibly hold the valve element 60 below the vehicle speed at which it reaches the switching position 56A.

The 2-3 speed changeover valve 57 similarly has valve elements 68 and 69 facing each other in the axial direction via a compression coil spring 67, with the valve element 68 also having a downward direction in the figure, which is also actuated by the spring 67. The sum of the pressing force and the downward pressing force due to the throttle oil pressure Pth exerted on the port 10 via the oil passage 50b, and the upward pressing force in the figure exerted by the governor oil pressure Pgo applied to the lower end port 71 through the oil passage 55b. The balance relationship allows switching between a downward switching position as shown at 57A and an upward switching position as shown at 57B.

Further, on the upper surface of the upper valve element 69, there are two manual switching valves 44.
When the range is switched, the line hydraulic pressure appearing at the output port 43c is applied through the oil passage 48 and 48a1 port 72, and at this time, the valve element 69 is displaced downward and the valve element 68 is moved to the 57A. The switch is forcibly held in the downward switching position shown in .

The overdrive control valve 58 has a valve element 74 pressed downward by a compression coil spring 73, and the governor oil pressure Pgo supplied to the port 75 via the oil path 55c is applied to the lower end of the valve element. It looks like this.

Further, in addition to the downward pressing force exerted by the spring 73, the upper end of the valve element 74 is applied to the throttle hydraulic pressure Pth or the manual switching valve 44.
When the switch is switched to the 2 range, the line hydraulic pressure appearing at the output port 43c is applied through the oil passage 50c or 48h, respectively, and further via the shuttle valve 76 and port 7γ, and the force due to this hydraulic pressure and the spring force are Due to the balance between the sum of It is now possible to

- When the manual switching valve 44 is switched to the D range, the port 78 of the second-speed switching valve 56 has seven song names 47b.
Line oil pressure is supplied.

When the 1st-2nd speed switching valve is in the upward switching position indicated by 56B, this line oil pressure is applied to the oil passage 4 from the port 19.
7c and is led to the port 80 of the 2-3 speed switching valve 57.

When the 2-3 speed switching valve is in the downward switching position shown at 57A, the line oil pressure led to this port 80 is
The oil is guided from the port 81 to the brake 26 (second brake) via an oil path 47d.

Further, when the 2-3 speed switching valve is in the upward switching position as shown at 57B, the hydraulic pressure supplied to the port 80 is guided to the port 82, from which it passes through the oil passage 47e and the shuttle valve 47f to the clutch 25 ( reverse clutch).

Incidentally, when the manual switching valve 44 is switched to the L range, the oil pressure appearing at the output port 1-43d is transferred to the port 64 of the low modulator valve 66. It is then supplied to the inside side of brake 2γ (first brake).

Furthermore, a manual switching valve 44 is installed on the outside side of the brake 27.
When the engine is switched to the R position, the hydraulic pressure that appears at its output capo 43e is supplied.

Line hydraulic pressure is supplied to the port 84 of the overdrive control valve 58 from the oil passage 43 via an oil passage 43f.

When the overdrive control valve is in the downward switching position as shown at 58A, the line oil pressure supplied to this port 84 is supplied to the clutch 12 of the overdrive mechanism via the port 85 and the oil passage 43g, and When the drive control valve is in the upwardly switched position as shown at 58B, the oil is supplied to the brake 19 of the overdrive mechanism via the port 86 and the oil passage 43h.

The operating procedure of the hydraulic control circuit shown in FIG. 2 is basically well known, and its outline is as follows.

) When the D range manual switching valve 44 is switched to the D range,
Line hydraulic pressure is supplied to the oil passage 47, and this line hydraulic pressure is supplied to the clutch 24 as it is.

At this time, when the vehicle is stopped or in a low speed running state, the governor oil pressure Pgo generated by the governor oil pressure control valve 54 is low, and the 1st-2nd speed switching valve 56, the 2nd-3rd speed switching valve 57, and the overdrive control valve 58 are They are in the downward switching position as shown at 56A, 57A and 58A, respectively, and the oil passage 47
The hydraulic pressure supplied through port 78 is cut off at port 78, and therefore no hydraulic pressure is supplied to reverse clutch 25 and second brake 26, which are connected to the oil passages thereafter.

On the other hand, the oil pressure led to the overdrive control valve 58 from the oil passage 43f is supplied to the clutch 12 of the overdrive 1 drive mechanism.

Therefore, in this state, the overdrive mechanism is in a locked state and the gear transmission mechanism is in the first speed state.

As the vehicle speed gradually increases from this state, the governor core free pressure P
go gradually increases, and at a certain vehicle speed, the 1st-2nd speed switching valve 56
is switched to the position 56B, and the line oil pressure is led to the port 19, and this oil pressure is transferred to the port 8 of the 2-3 speed switching valve 57.
It is transmitted from 0 to 81, is supplied to the second brake 26 via the oil path 47d, and engages the brake 26.

In this state, the gear transmission mechanism is switched to the second speed state.

When the vehicle speed further increases, the 2nd-3rd speed switching valve 57 is also switched to the position 57B, and the hydraulic pressure supplied to that port 80 is then transmitted to the port 82), from which the oil passage 47
It is supplied to the reverse clutch 25 through the e1 shuttle valve 47f, engages the clutch 25, and on the other hand brake 26
The hydraulic pressure acting on the oil passage 41d1 is discharged from the port 81 through the drain port 81a.

In this state, the gear transmission mechanism is switched to the third speed (directly connected) state.

As vehicle speed increases further, overdrive control valve 58 is also switched to position 58B, thereby causing its port 8
The hydraulic pressure supplied to the clutch 12 is supplied to the brake 19 from the port 86 instead of the port 85 through the oil passage 43h, while the oil pressure that was acting on the clutch 12 is supplied to the brake 19 through the oil passage 43g1 port 8.
5 and is discharged to the drain port 85a.

In this state, the overdrive mechanism 2 operates and an overdrive state is achieved.

The above has explained the switching changes that occur as the governor oil pressure increases due to an increase in vehicle speed. Of course, such switching changes are performed based on the balance between the governor oil pressure and the throttle oil pressure that act in opposition to the valve elements of each switching valve, as described above. It is possible to
The switching point changes not only depending on the vehicle speed but also on the amount of depression of the accelerator pedal.

Conversely, when the vehicle speed decreases, the overdrive control valve 58.2-3rd speed switching valve 57.1-2nd speed switching valve 56
respectively from 58B to 58A, and from 57B to 57A.
It will be obvious that the shift is made from 56B to 56A, and a corresponding change in gear stage occurs.

When the 2-range manual switching valve 44 is switched to the 2-range, hydraulic pressure is generated not only at the output port 1-43b but also at the output port 43c, and the hydraulic pressure passes through the oil passages 48a and 48b to the 2-range, respectively.
It is supplied to the port 72 of the 3rd speed switching valve 51 and the port 7γ of the overdrive control valve 58, and forcibly pushes these valve elements 69 and γ4 downward in the figure, thereby controlling the 2nd-3rd speed switching valve and the overdrive control valve. The valves are forced into the switched positions of 57A and 58A, respectively.

Therefore, in such a state, the overdrive mechanism is held in a locked state, and the gear transmission mechanism operates only in the second speed or lower, that is, in the first speed or the second speed.

When the L range manual switching valve 44 is switched to the L range, oil pressure is also generated at its output port 43d, and this oil pressure is passed through the low modulator valve 66 to the port 6 of the 1st-2nd speed switching valve 56.
4 and 65 to drive its valve element 61 downward in the figure and forcefully hold the 1-2 speed switching valve in the condition 56A.

In this state, the automatic transmission mechanism is maintained at the first speed state.

Next, the switching operations of the 1st-2nd speed switching valve 56, the 2nd-3rd speed switching valve 57, and the overdrive control valve 58 will be described in more quantitative detail.

FIG. 3 is a graph showing changes in throttle oil pressure pth with respect to accelerator opening.

As shown in this graph, the throttle oil pressure increases and decreases approximately in proportion to the accelerator opening.

FIG. 4 is a graph showing changes in governor oil pressure Pgo with respect to output shaft rotational speed (corresponding to vehicle speed).

In this case as well, the governor oil pressure changes approximately in proportion to the output shaft rotation speed.

FIG. 5 is a graph showing the change in line oil pressure PL with respect to 1 degree of accelerator opening. As shown in the figure, the line oil field has a predetermined withstand pressure level even when the accelerator opening is zero, and as the accelerator opening increases. It is gradually increasing.

(A) Regarding the operation of the 1st-2nd speed switching valve 56: (A-a)
When the valve moves upward from the downwardly displaced state 56A: (A-a・1) When the manual switching valve 44 is set to the D range position: ' (A-a・1・1) Open the accelerator. When the switching valve 52 is not activated when the switching valve 52 is not operating (when the oil passages 51 and 53 are cut off): The throttle oil pressure pth appearing at the port 50 of the throttle oil pressure control valve 45 is transmitted through the oil passage 50a. 1-2 speed switching valve 5
6 is supplied to port 62, from which it reaches port 62a, and further supplied to port 62c via shuttle valve 62b.

On the other hand, the governor hydraulic pressure Pg generated by the governor hydraulic control valve 54
o is connected to the port 63 of the 1st-2nd speed switching valve 56 via the oil passage 55a.
supplied to

The valve element 60 moves upward due to the balance between the sum of the downward spring force F exerted by the spring 59, the downward force exerted by the throttle hydraulic pressure on the land L1□, and the upward force exerted by the governor hydraulic pressure on the land L1□. Since it moves, the balance equation is as follows.

A11Pth+F1<A12PgO (1) where, A1
1 and AI□ are the areas of lands L11° and L1□, respectively, and Fl is the spring force of the spring 59.

(A-a.1.11) When the accelerator opening is above a certain value α and the switching valve 52 is activated (when the oil passages 51 and 53 are in communication): Detent oil pressure regulated by the detent oil pressure control valve 46 Pd
is supplied to the shuttle valve 62b via the oil path 53a,
If the throttle oil pressure pth is larger than the tetent oil pressure Pd, the throttle oil pressure will act on the port 62c, and the balance condition equation will be expressed as in the case of A-a.1.1.
1).

(A-a.2) When the manual switching valve 44 is set to the 2 range position: In this case, line oil pressure appears in the oil passages 47 and 48,
Compared to the case of the D range, the new hydraulic pressure generated in the oil passage 48 does not act on the 1st-2nd speed switching valve 56, so the operation of the 1st-2nd speed switching valve is the same as in the case of A-a.1. The balance conditional expression is also the same.

(A-a.3) When the manual switching valve 44 is set to the L range position: In this case, line oil pressure appears in the oil passages 4γ, 48, and 49.

The line oil pressure appearing in the oil passage 49 is regulated to a predetermined low modulator oil pressure PR by the low modulator leak valve 66.
It is added to ports 64 and 65 of the 1-2 speed switching valve 56.

At this time, when the valve element 61 moves downward, the port 64 communicates with the port 83, and the hydraulic pressure passes through the oil path 49a to the brake 2.
7 and engages it.

Also, at this time, the port 65 is closed, so the low modulator hydraulic pressure is supplied only to the port 64.

(A-a.3.1) When the accelerator opening is below a certain value α and the switching valve 52 is not activated: Same as in A-a.1.1 except that the low modulator oil pressure is uniformly applied to the land L13. Throttle oil pressure Pth
and the governor oil pressure Pgo act, so the balance equation in which the valve 60 moves upward is as follows.

A1□Pth ten A13PR<A1□Pgo+A14Pt
h (2) Here, A1□yA12tks are land L1, respectively.

This is the area of TiI41L13.

Governor oil pressure Pg o at maximum vehicle speed obtained by taking into account the maximum engine speed and torque converter slip in 1st gear
', A1□Pth 10A13I)R, >, A1□Pgo'+
A13. so that A14 Pt h. Once the value of PR is determined, the equation Ichihi holds true at all vehicle speeds, so the 1st-2nd speed switching valve will not be displaced upward in the L range.

(A-a.3.11) When the accelerator opening is greater than a certain value α and the switching valve 52 is activated: Same as in A-a.1.ii, the detent oil pressure Pd
is lower than the throttle oil pressure Pth, so in this case, the formula (
2) becomes the conditional expression.

(A-b) When the valve moves downward from the upwardly displaced state 56B: (A-b・1) When the manual switching valve 44 is set to the D range position: (A-b・1・1) When the accelerator opening is less than a certain value α and the switching valve 52 is not activated: The throttle oil pressure supplied via the oil path 50a is blocked at the port 62 of the 1st-2nd speed switching valve 56, and the valve element is not operated. does not work.

On the other hand, the governor oil pressure Pgo is supplied to the port 63 from the oil passage 55a.

Therefore, the balance equation in this case is as follows. ``1〉A
12 P g O (3) (A-b・1・[1) When the accelerator opening degree is above a certain value α and the switching valve 52 is activated: The detent oil pressure appearing in the oil passage 53 passes through the oil passage 53a1 and the shuttle valve 62b. Port 2 of 1-2 speed switching valve 56
It is supplied to c.

Governor oil pressure Pgo is supplied to port 63 in the same way as in A-b.1.1.

Therefore, in this case, the balance conditional expression for the downward movement of the valve element is as follows.

F1+A1□Pd>A1□Pgo (4)(
A-b.2) When the manual switching valve 44 is set to the 2nd range position: As in the case of A-a.2, the 1st-2nd speed switching valve does not change, and the balance condition equation is Similarly, in the D range, the formula (4) is obtained.

(A-b・3) When the manual switching valve 44 is set to the L range position: As in the case of A-a・3, the low modulator oil pressure P
R acts upwards on land L13.

(A-b.3.1) When the accelerator opening is below a certain value α and the switching valve 52 is not activated: In A-b.2.1 except for the low modulator oil pressure PI (, acting on land 13) Similarly, the throttle oil pressure Pth does not act on the 1st-2nd speed switching valve 56, and the governor oil pressure Pth
Since only go acts, the balance conditional expression for the valve element to move downward is as follows.

A15 P B> AI 2 P g O (5) where is the area of AI5.

(A-b.3.11) When the accelerator opening is above a certain value α and the switching valve 52 is activated: The detent oil pressure supplied to the shuttle valve 62b via the oil passages 53 and 53a is caused by the throttle oil pressure being applied to the shuttle valve. Since it is not supplied, it is supplied to port 62c.

Therefore, the conditional expression for the valve element to move downward is as follows.

A11Pd+A15PR>A11Pd+A15PR(6
) (B) Regarding the operation of the 2nd-3rd speed switching valve 57 and the overdrive control valve 58: The same analysis as above for the 1st-2nd speed switching valve 56 is performed for these valves, but a simple one will be used here. For this reason, a detailed explanation will be omitted, and the balance condition expressions for each case will be listed in Table 3 below.

Automatic transmission diagrams obtained from the calculation formulas in Table 3 are shown in FIGS. 6, 7, and 8 for each range, respectively.

FIG. 9 is a hydraulic circuit diagram of essential parts showing one embodiment of the hydraulic control circuit according to the present invention, and corresponds to the right end portion of the hydraulic circuit shown in FIG.

In FIG. 9, parts in FIG. 2 are designated by the same reference numerals as in FIG.

In this embodiment, in the middle of the oil path 55c that supplies the governor hydraulic pressure to the port 75 of the overdrive control valve 58, there is provided a governor which is controlled by the governor hydraulic pressure and which is connected to the overdrive control valve when the governor hydraulic pressure is below a predetermined value. The three-way switching valve 87 is provided with a switching valve 87 for cutting off the supply of hydraulic pressure.The switching valve 87 has a valve element 89 pressed downward in the figure by a compression coil spring 88, and controls the governor hydraulic pressure applied to its port 90. Depending on the size, switching is performed between a downward switching value as shown at 87A and an upward switching position as shown at 87B.

When this switching valve is in the downward switching position indicated by 87A, the port 91 is closed and the oil passage 55d is closed.
The governor hydraulic pressure supplied through the port 92 is cut off here, and the hydraulic pressure does not appear at the port 92, so that the governor hydraulic pressure is not supplied to the port 75 of the overdrive control valve 58, which is connected to the port 92 through the oil passage 55e.

When the switching valve 87 is displaced to the upward switching position indicated by 87B, the ports 91 and 92 are in communication, and the governor hydraulic pressure is supplied to the port γ5 of the overdrive control valve 58.

The operating conditions of the switching valve 87 are as follows.

(a) When the valve 87 moves upward from the downward switching state 8γA: This conditional expression is as follows.

F4<A4, Pgo(7) Here, F4 is the set load of spring 88, A4□ is land L4
It is the area of □.

(b) When the switching valve 87 moves downward from the upward switching state 87B: The conditional expression for this is as follows.

F4 <A42 P go (8) where A
42 is the area of land L42.

By selecting the spring force F4 of the spring 88 and the areas of the lands L41 and L4□ to appropriately satisfy the conditions according to the above equations (7) and (8), the overdrive control valve 58 is
Regardless of the value of the throttle oil pressure acting on the port 77, until the governor oil pressure reaches an arbitrary predetermined value, it is reliably held at the downward switching position as shown at 58A, and is therefore supplied via the oil path 43f. The line oil pressure thus generated reaches port 84 to port 85, from which it is supplied to clutch 12 of the overdrive control valve, so that the overdrive mechanism is reliably maintained in a locked state and the overdrive is not activated.

FIG. 10 is a diagram similar to FIG. 9 showing a second embodiment of the present invention.

In this figure as well, parts corresponding to those in FIG. 2 are designated by the same reference numerals as in FIG.

In this embodiment, a portion of the overdrive control valve 58 is modified from the structure shown in FIG. The hydraulic pressure applied to the port 77 is supported by the piston element L3m.
It is designed to act on the upper end of m.

The operating condition expressions of such overdrive control valves are shown in Table 4, following Table 3, for each case.

As can be seen from the D range (1) in Table 4, in this case, the overdrive control valve 58 is at 58A until the force of the throttle oil pressure Pth acting on the piston element L3m overcomes the spring force of the compression coil spring 73. The value of the governor oil pressure when switching from the downward switching position shown at 58 to the upward switching position shown at 58B is determined only by the spring force F3 of the spring 73, regardless of the throttle oil pressure acting on the port 77.

Therefore, in this case, by appropriately determining the spring force F3 of the spring 73 and the area A3m of the piston element Lm, the lower limit value of the vehicle speed for switching the first bad drive control valve 58 to the overdrive operating position can be set to the throttle oil pressure. It can be determined regardless.

11 and 12 are D range automatic shift diagrams (however, only the 3-0/D shift diagram is omitted) of the embodiment shown in FIGS. 9 and 10, respectively.

As shown in these figures, both the <3-0/D upshift diagram and the 0/D-3 downshift diagram change vertically at a certain vehicle speed. The overdrive condition is not caused under any circumstances.

In the embodiment shown in FIG. 9, as is clear from the figure, one switching valve 87 is added to the conventional hydraulic 'feU control circuit.

In this embodiment, as shown in FIG. 11, at vehicle speeds above a predetermined speed at which the overdrive mechanism can operate, the automatic gear shift diagram is similar to that of conventional hydraulic control without the additional switching valve 87. It is the same as the automatic transmission diagram of the device.

In the embodiment shown in FIG. 10, only a portion of the overdrive control valve has been modified and no additional cutoff valves are required.

In this case, as shown in FIG. 12, the D range automatic shift diagram is somewhat different from that of the conventional hydraulic control circuit.

However, in either embodiment, by appropriately selecting the spring force F4 or F3 of the spring 88 or 73, it is possible to arbitrarily set the minimum vehicle speed for the overdrive mechanism to operate.

It will be apparent to those skilled in the art that various modifications can be made to the embodiments described above without departing from the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a hydraulic automatic transmission with an overdrive device. FIG. 2 is a hydraulic circuit diagram showing a general configuration of a hydraulic control device for the automatic transmission shown in FIG. 1. FIG. FIG. 3 is a graph showing changes in throttle oil pressure with respect to accelerator opening. FIG. 4 is a graph showing changes in governor oil pressure with respect to output shaft rotational speed. FIG. 5 is a graph showing changes in line oil pressure with respect to accelerator opening. 6, 7, and 8 are automatic shift diagrams of the D range, 2 range, and L range of the hydraulic control device shown in FIG. 2, respectively. FIG. 9 is a partial diagram of a hydraulic circuit showing one embodiment of the hydraulic control device of the present invention. FIG. 10 is a diagram similar to FIG. 9 showing another embodiment of the present invention. FIGS. 11 and 12 are D-range automatic shift diagrams in the embodiment shown in FIGS. 9 and 10, respectively. 1...torque converter, 2...overdrive mechanism, 3...gear transmission mechanism, 5...
...Pump, 6...Turbine, 1...
...Stator, 8... Engine crankshaft, 9...
... Turbine shaft, 10 ... Carrier, 11
...Sankia, 12...Multi-plate clutch, 13...One-way clutch, 14...
... Planetary pinion, 15 ... Ring gear, 16 ... Overdrive case, 18 ...
...Transmission case, 19...
Multi-disc brake, 23... Input shaft of gear transmission mechanism, 24, 25... Multi-disc clutch, 26° 27.
...Multi-disc brake, 28...One-way clutch, 29...Intermediate shaft, 30...
Sun gear axis, 31...Support, 32...
...Sangia, 33...Career, 34...
...Planetary pinion, 35...Ring gear, 36...Carrier, 37...Planetary pinion, 38...Ring gear, 39.
... Output reason, 40 ... Oil reservoir, 41 ... Oil pump, 42 ... Line hydraulic control valve, 44 ... Manual switching Valve, 45・
...Throttle oil pressure control valve, 46...Detent oil pressure control valve, 47...D range output oil path, 48...2 range output oil path, 49.・・・・・・
・L range output oil path, 52...Switching valve, 54.
...Governor hydraulic control valve, 56...1-2
Speed switching valve, 57...2-3 speed switching valve, 58...
...Overdrive control valve, 66...Low modulator valve, 87...Switching valve, L3m...
····piston.

Claims (1)

[Claims] 1. A hydraulic control device for an automatic transmission including a hydraulic torque converter and a gear transmission mechanism equipped with a plurality of frictional engagement devices for obtaining several gear stages, A hydraulic pressure source, a line hydraulic control valve that generates a line hydraulic pressure regulated from the hydraulic source, a throttle hydraulic control valve that generates a throttle hydraulic pressure according to the intake throttle opening, and a governor hydraulic pressure that generates a governor hydraulic pressure according to the vehicle speed. a governor hydraulic pressure control valve, a plurality of shift valves that switch the hydraulic pressure supplied to the frictional engagement device according to a manual switching operation for manually switching a transmission range, and an equilibrium relationship between the throttle hydraulic pressure and the governor hydraulic pressure; and one of the speed change valves to maintain the speed change valve that achieves the highest speed gear in the low speed side switching position regardless of the value of the throttle oil pressure when the governor oil pressure is below a predetermined value. A transmission valve is provided in the middle of a passage that guides the governor hydraulic pressure to the transmission valve that achieves the highest speed gear, and is controlled by the governor hydraulic pressure, and is in a disconnected state when the governor hydraulic pressure is below a predetermined value and is in a communication state when the governor hydraulic pressure is above a predetermined value. A hydraulic control device comprising a switching valve. 2. A hydraulic control device for an automatic transmission including a hydraulic torque converter and a gear transmission mechanism equipped with a plurality of frictional engagement devices for obtaining several gear stages, the hydraulic control device including a hydraulic power source and the hydraulic pressure. A line hydraulic control valve that generates line hydraulic pressure regulated from a source, a throttle hydraulic control valve that generates throttle hydraulic pressure according to the intake throttle opening degree, and a governor hydraulic control valve that generates governor hydraulic pressure according to the vehicle speed; a manual switching valve that manually switches a speed range; a plurality of shift valves that switch hydraulic pressure supplied to the frictional engagement device according to an equilibrium relationship between the throttle hydraulic pressure and the governor hydraulic pressure; Achieving the highest speed among the speed change valves so that the speed change valve that achieves the highest speed among the speed change valves is held in a low speed side switching position regardless of the value of the throttle oil pressure when the value is less than a predetermined value. The speed change valve has a valve element receiving the governor oil pressure at one end, a piston receiving the throttle oil pressure at one end, and a compression spring interposed between the other end of the valve element and the other end of the piston. When the oil pressure is less than a predetermined value, the spring force of the compression spring is balanced with the governor oil pressure by overcoming the throttle oil pressure, and when the throttle oil pressure is more than a predetermined value, the spring force of the compression spring is exceeded and the throttle oil pressure is adjusted. A hydraulic control device characterized in that the hydraulic control device is configured to balance the governor hydraulic pressure with the governor hydraulic pressure.