DE3732676C2 - - Google Patents

Description

The invention relates to a hydraulic control circuit for an automatic transmission with two forward gear ranges, the control circuit being a fail-safe circuit and a Hand-L trap includes. Such automatic transmissions are made, for example known from DE 31 17 276 or DE 35 32 784 become.

FIG. 5 shows according to an internal state of the art a further hydraulic control circuit for an automatic transmission with two forward speed ranges. This control circuit comprises a torque converter 1 , a manual switching valve 2 , a switching valve 3 , a solenoid valve 4 controlling the switching valve, a control valve 5 , a memory 6 , an oil pump 7 and an oil cooler 8 . The state of engagement of a friction clutch device comprising a clutch C1 and brakes B1 and B2 in each speed or gear range of the automatic transmission is shown in Table 1.

Table 1

When a shift from the second speed or speed range of the D range to the L range is carried out in this hydraulic control circuit, the solenoid valve 4 is set in the open state until the driving speed drops below a predetermined value and becomes like that The following table 2 shows that the second speed stage is maintained, a manual L blocking circuit being formed. This makes it possible to prevent the engine from continuing to run when a manual L shift is made.

Table 2

However, since this conventional hydraulic control circuit has only a single solenoid valve for control, a fail-safe circuit cannot be formed if the solenoid valve 4 malfunctions. If a failure occurs in the electrical circuit for controlling the solenoid of the solenoid valve, first gear cannot be achieved even if the manual control valve is switched to an L position.

On the other hand, assuming that the hydraulic control circuit also to be referred to as internal prior art has the structure shown in Fig. 6 and that a fail-safe circuit is formed by a single solenoid valve as shown in Table 3, it will not be possible to form the hand-L blocking circle.

Table 3

It is therefore the object of the invention to achieve the above adhering to the conventional hydraulic control circuit Solve problems, d. that is, a hydraulic Control circuit for an automatic transmission with two forward gear ranges be created in which both a fail-safe Circle as well as a hand-L blocking circle by a single Solenoid valve can be formed.

To achieve this object, the invention provides a hydraulic system lik control circuit for an automatic transmission with two forward before ranges, with a changeover valve for setting two switching levels by one solenoid valve is switched. The changeover valve is provided with an auxiliary valve, with a manual change of the forward gear range either a forward Control of the switch valve allows on both sides, so that the solenoid valve in each case takes the opposite switching position.

In the D area z. B. operates the hydraulic control circuit according to the invention of the automatic transmission such that the changeover valve switched in response to the switching of the solenoid valve  so that a first speed state (D-1) and a second speed state (D-2) of the D range getting produced. If the L range is effective, then the auxiliary valve by a manual L signal pressure from a manual switch valve actuates and switches in response to switching of the solenoid valve, the changeover valve in one direction um, to that prevailing in the mentioned D-area has, is reversed, so that a first speed state (L-1) and a second speed state (L-2) for the L range. That way you can four different switching or speed states (D-1, D-2, L-1, L-2) accomplished by a single solenoid valve will.

Preferred developments of the invention are the subject of Claims 2 to 9.

Despite the fact that the automatic transmission has two forward gear ranges has a hydraulic control circuit that contains only a single solenoid valve, it is through the invention possible both a fail-safe circle as well as forming a hand-L blocking circle, whereas it is at the prior art was only possible one of these Realize circles with a single solenoid valve. If for example, as Table 4 shows, such an arrangement is taken that the switching valve is a hydraulic pressure is applied to keep this valve in the second driving state, when the solenoid valve is closed, the Auxiliary valve is in the L range, and such that the Hydraulic pressure holding valve in the second speed stage is placed on an outlet side to the changeover valve to put in a first speed stage when the solenoid valve is open with the auxiliary valve in the L area, then it becomes a fail-safe circle  form in the event that the solenoid valve due to a Malfunction opens how to also form a hand-L blocking circuit if a shift from the D range (in D-2 speed state) to the L area.

Table 4

According to the invention, a changeover valve with an auxiliary valve (Check valve) provided in response to the Switching a solenoid valve when the L range is effective, the changeover valve switches in a direction that is to that that prevails when the D range is effective, vice versa is so that it is made possible with the help of a single solenoid valve in an automatic transmission with two Forward gear ranges to get four switching states and both a fail-safe circle and a hand-L- To form a blocking circle.

To the disadvantages of the prior art highlighted above to eliminate, another way is conceivable, according to which an additional solenoid valve for a manual L-lock circuit to a solenoid valve for 1-2 switching becomes. In the case of an automatic transmission with two speed ranges however, the space in the hydraulic circuit is very limited and can the additional solenoid valve that exclusively used for the manual L blocking circuit, not effective  used for another purpose in this circuit will. This makes it difficult to make room for installation preserve or ensure. Furthermore, the solenoid valve costly and increases the total cost. According to the invention it is sufficient, in addition, only one, small and to provide cheap auxiliary valve so that the above the spatial constraints and costs Disadvantages can be eliminated.

The subject of the invention is described with reference to the drawings, where spatial information on the respective figure relate, explained. Show it:

Fig. 1 is a diagram of a hydraulic circuit, wherein a D-2 state is shown in the embodiment according to the invention;

FIG. 2 shows a diagram similar to FIG. 1 for a D-1 state;

. Fig. 3 is a similar to Figure 1 scheme for a L-2 state;

FIG. 4 shows a diagram similar to FIG. 1 for an L-1 state;

FIGS. 5 and 6 are hydraulic circuit diagrams showing examples according to an internal prior art.

As shown in FIGS. 1-4 show the switching valve 10 has a spool 11 having supporting surfaces 11 a and b 11. The control piston 11 is pressed to the right in the figures by a spring 12 attached to the left end of the control piston. The changeover valve 10 has an inlet port 10 a, the 10 A communicates with one at the left end side of the supporting surface 11 a formed oil chamber, a recess formed with a between the supporting surfaces 11 a and b 11 oil chamber 10 B associated clutch pressure outlet port 10 b, an inlet opening 10 c connected to an oil chamber 10 C formed on the right end face of the control piston 11 and an inlet opening 10 d formed between the inlet opening 10 c and the clutch pressure outlet opening 10 b. When the control piston 11 in the right side in the figures position under the urging force of the spring 12 (Fig. 1 and 3), then is the clutch pressure outlet port 10 b to the inlet port 10 d via the oil chamber 10 B in combination. The control piston is in the left side position against the urging of spring 12 (Fig. 2 and 4), then the inlet port 10 b ver included d by the area 11 and the clutch pressure outlet port 10 b is connected to the drain port 10 e.

A check or auxiliary valve 20 has a control piston 21 with load-bearing surfaces 21 a and 21 b, which is pressed to the right by a spring 22 acting on its left end face. The check valve 20 includes a with a between the surfaces 21 a and 21 of the control piston 21 b formed oil chamber 20A associated inlet port 20 a, a a trained outlet port 20 b to the left of the inlet port 20, a hand-L-signal pressure inlet port 20 c, which is in communication with an oil chamber 20 B formed on the right end face of the control piston 21 , and an outlet opening 20 d formed between the hand-L signal pressure inlet opening 20 c and the inlet opening 20 a. When the control piston 21 under the pressure of the spring 22 in the right-side position (Fig. 1 and 2), then the inlet opening 20 a and the outlet port 20 d through the oil chamber 20 A and the outlet port 20 b with a drain opening 20 e connected. The control piston 21 is against the pressure of the spring 22 in the left-hand position ( FIGS. 3 and 4), then the outlet opening 20 d is closed by the supporting surface 21 b and the inlet opening 20 a is connected to the outlet opening 20 b.

The inlet opening 10 a of the changeover valve 10 is with the outlet opening 20 b of the check valve 20 , the inlet opening 10 d is upstream with a line pressure oil line L1 from a throttle point 40 and the inlet opening 10 c of the oil chamber 10 C with the line pressure oil line L1 the throttle point 40 via a throttle point 50 with the outlet opening 20 d of the check valve 20 in connection.

The inlet port 20 a of the check valve 20 is downstream of the throttle body 40 is connected to the line pressure oil path L1, while the inlet port 20 c of the oil chamber 20 B with a hand L signal pressure outlet port 30 a of the manual valve 30 is in communication.

The brake B1 is actuated by a spring-loaded actuator or servo device B1-S via the oil line L2, which is connected to the manual control valve 30 via a throttle and check valve group 42 . The side of the servo B1-S, on which the spring is located, is connected via a parallel group 41 from a throttle point 41a and a check valve 41b, which allows a flow to the brake B1 are connected to an oil passage L3 for the clutch C1. The oil path L3 is b to the clutch pressure outlet port 10 via a throttle and non-return valve assembly 43 and connected to the memory. 6 The solenoid valve 4 is controlled by an electronic control unit ECU in response to the running speed of the vehicle and other conditions.

With the exception of the changeover valve, the check valve and the associated oil lines, the construction of the other parts of the hydraulic control circuit and the operation of the clutch and the brakes in any speed state correspond to the design in the conventional hydraulic control circuit shown in FIG. 5.

The operation of the hydraulic control circuit in each switching or speed condition is assigned based on the Drawings described in the implementing regulations.  

Fig. 1 shows the second speed state (D-2) of the D range. The solenoid valve 4 is open. Consequently, the line pressure from the manual switching valve 30 in the oil line L1 at the inlet opening 10 c of the switching valve 10 produces no pressure. Since the D range predominates, the L signal pressure from the manual L signal pressure inlet opening 20 c is not generated in the oil chamber 20 B of the servo valve 20 . The control piston 21 is under the force of the spring 22 in the right-hand position, the inlet opening 20 a is connected to the outlet opening 20 d via the oil chamber 20 A. As a result of 10 C of the switching valve 10 is not generated pressure in the oil chamber.

As a result, the control piston 11 of the changeover valve 10 is under the force of the spring 12 in the right-hand position (in FIG. 1), so that the inlet opening 10 d and the clutch pressure outlet opening 10 b are connected to one another to supply line pressure from the oil line L1 to To lead clutch C1 and thus establish the second speed state, as indicated in Table 1.

Fig. 2 shows the first speed state (D-1) of the D range. When the vehicle speed decreases from the second speed state (D-2) of FIG. 1 to a value below a predetermined vehicle speed, then the solenoid valve 4 is closed. As a result, the line pressure from the manual switching valve 30 in the oil line L1 is introduced into the oil chamber 10 C of the switching valve 10 from the inlet port 10 c. Since the D range is present at the manual switching valve 30 at this moment, the L signal pressure is also not generated in the chamber 20 B of the check valve 20 , in which the control piston 21 is in its right-hand position. Consequently, the line pressure is introduced into the oil chamber 10 C through the inlet opening 20 a, outlet opening 20 d and inlet opening 10 c.

Due to the hydraulic pressure introduced into the oil chamber 10 C, the control piston 11 is displaced against the force of the spring 12 to the left, so that as a result the inlet opening 10 d is closed by the surface 11 b. In addition, the clutch pressure outlet opening 10 b is connected to the drain opening 10 e, so that the clutch pressure is discharged via the drain opening 10 e. As a result, the clutch C1 is released from its engaged state and the brake B1 is applied by the line pressure from the manual switching valve 30 in the oil line L2. As a result, the first speed state is established as shown in Table 1.

In FIG. 3, the second speed state (L 2) of the L-section is shown. When the manual valve 30 is shifted from the second speed state (D-2) of Fig. 1 to the L range, then the solenoid valve 4 is closed until the driving speed drops below the predetermined vehicle speed (V₂₁). The hand-L-Signaldruck- outlet opening 30 a of the manual valve 30 outputs the low signal pressure applied to the oil chamber 20 B of the hand-L-Signaldruck- inlet port 20 c of the check valve 20 is placed, with which the control piston 21 against the force the spring 22 is shifted to the left.

As a result, the outlet opening 20 d is closed by the surface 21 b and hydraulic pressure introduced into the oil line L3 from the oil line L1 via the throttle point 50 is blocked at the outlet opening 20 d. In addition, the inlet opening 20 a and the outlet opening 20 b are connected so that the line pressure from the oil line L1 through the inlet opening 20 a, the oil chamber 20 A, the outlet opening 20 b and the inlet opening 10 a of the changeover valve 10 are introduced into the oil chamber 10 A. becomes.

Despite the fact that the line pressure is introduced into the oil chamber 10 C of the changeover valve 10 , the control piston is consequently in the right-hand position under the pressure force of the spring 12 and the pressure force of the hydraulic pressure introduced into the oil chamber 10 A. As a result, the inlet opening 10 d and the clutch pressure outlet opening 10 b are connected to one another, so that the clutch pressure is applied from the oil line L1 to the clutch C1, which maintains the second speed state.

When a shift from the D-2 state to the L range is performed, the solenoid valve 4 is closed until the vehicle speed drops below the predetermined vehicle speed V₂₁, and the changeover valve 10 is kept in the second speed state due to the operation of the check valve 20 . As a result, a hand L lock circle is formed.

FIG. 4 shows the first-speed state (L-1) of the L-range. As in the case of FIG. 3, the control piston 21 of the check valve 20 is held in the left-hand position due to the L signal pressure from the manual switching valve 30 . If the driving speed drops below the predetermined driving speed from the second speed state (L-2) of FIG. 3, the solenoid valve 4 is opened, so that the pressure oil from the oil chamber 10 A of the changeover valve 10 via the inlet opening 10 a, the outlet opening 20 b and the inlet opening 20 a is discharged from the solenoid valve 4 . As a result, the hydraulic pressure in the oil chamber 10 C overcomes the force of the spring 12 and presses the control piston 11 to move to the left. Thus, in the same way as in FIG. 2, pressure oil is discharged from the clutch C1 via the drain opening 10 e and the brake B1 is applied due to the brake pressure from the oil line L2, so that the first speed state (L-1) is established.

Should the solenoid valve 4 open due to a malfunction in the L-2 state shown in FIG. 3, the state shown in FIG. 4 is established and the first speed state is maintained. As a result, a fail-safe circle is formed.

Claims (8)

1.Hydraulic control circuit for an automatic transmission with two manually switchable forward gear ranges (D, L), in each of which two switching stages can be set by alternately acting on friction elements by means of a changeover valve ( 10 ) which is switched by a single solenoid valve switched according to an instantaneous vehicle speed ( 4 ) pilot operated, characterized in that in the pilot control circuit for controlling the changeover valve ( 10 ), a 2-position multi-way valve auxiliary valve ( 20 ) is interposed, which optionally with a manual change of the forward gear range (D, L) Pilot control of the change-over valve ( 10 ) on both sides enables the solenoid valve ( 4 ) to assume the opposite switching position while the friction elements are constantly applied. 2. Control circuit according to claim 1, characterized in that when the auxiliary valve ( 20 ) is in the L region, hydraulic pressure is introduced into the changeover valve ( 10 ) in order to keep this valve in a second speed state when the solenoid valve ( 4 ) is closed, and that the hydraulic pressure holding the changeover valve in the second speed state is applied to an outlet side in order to bring the changeover valve ( 10 ) into a first speed state when the solenoid valve ( 4 ) is open. 3. Control circuit according to one of claims 1 or 2, characterized in that when switching the manual switching valve ( 30 ) from the D to L range, the solenoid valve ( 4 ) remains closed until the driving speed drops below a predetermined value. 4. Control circuit according to one of claims 1 to 3, characterized in that the auxiliary valve ( 20 ) has a spring-loaded control piston ( 21 ) and one acting on the control piston ( 21 ) against the force of a spring ( 22 ) and the manual L signal pressure receiving chamber ( 20 B), wherein the control piston ( 21 ) has two positions for actuating the changeover valve ( 10 ) by supplying an oil pressure acting on the control piston ( 11 ) of the changeover valve ( 10 ) in opposite directions. 5. Control circuit according to claim 4, characterized in that the auxiliary valve ( 20 ) two with two chambers ( 10 A, 10 C) of the changeover valve ( 10 ) connected outlet openings ( 20 b, 20 d) to the control piston ( 11 ) of the Switch valve ( 10 ) act in opposite directions, and has an inlet opening ( 20 a) connected to the solenoid valve ( 4 ). 6. Control circuit according to claim 5, characterized in that the one outlet opening (20 d) of the auxiliary valve (20) chamber (10 C) interacts with the one, counter to a spring (12) of the changeover valve (10) and the other outlet port (20 b) the auxiliary valve ( 20 ) with the other, in the same direction as the spring ( 12 ) acting chamber ( 10 A) is connected. 7. Control circuit according to claim 6, characterized in that the switching valve ( 10 ) with its outlet opening ( 10 b), when its inlet opening ( 10 d) is closed, to be connected to the outlet opening ( 10 e). That the manual valve (30) has 8. Control circuit according to claim 4, characterized in that a manual-low signal pressure in its L-range position dispensing outlet (30 a) connected to the chamber (20 B) of the auxiliary valve (20 ) is connected.