JP2605533B2 - Automatic transmission engine brake selection pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for appropriately controlling an engine brake selection pressure for operating a friction element for an engine brake of an automatic transmission.

[0002]

2. Description of the Related Art As described in, for example, "RE4R01A Automatic Transmission Maintenance Manual" (A261C07) issued by Nissan Motor Co., Ltd., automatic transmissions are operated by selective hydraulic operation of various friction elements (clutches, brakes, etc.). A gear is selected and a shift to another gear is performed by switching the friction element to be operated. On the other hand, depending on the gear stage, there is a gear stage where engine braking cannot be obtained due to the configuration of the power transmission path.If engine braking is required at this gear stage, the requirement can be satisfied by hydraulically operating a separate engine brake friction element. The automatic transmission is configured to operate.

Incidentally, the friction element for engine braking may be used also in the reverse traveling range, and the low reverse brake corresponds to the automatic transmission described in the above literature.

As described above, the low reverse brake as a friction element for engine braking used in the reverse travel range brakes a member rotating in the leading direction in the forward travel range, but trails the same member in the reverse travel range while using the same member. As a result, the brake that is rotating in the direction is braked, so that the brake capacity tends to be insufficient. For this reason, usually, a low reverse brake is designed so that the brake capacity is sufficient in the reverse drive range, and the engine brake selection pressure supplied to the forward drive range is reduced by the pressure reducing valve to reduce the brake capacity in the range. Measures have been taken to reduce the shock of engaging the low reverse brake.

[0005]

Conventionally, however, the pressure reducing valve reduces the input pressure (the same pressure as the hydraulic pressure for operating the low reverse brake in the reverse travel range) to a constant value and supplies it to the low reverse brake. Because it was
The low reverse brake, which was activated to apply the engine brake in the forward drive range, was not always suitable.

For example, when the vehicle is running at a high vehicle speed and the low-reverse brake is actuated, as compared with the case where the vehicle is running at a low vehicle speed and the low-reverse brake is operated, the vehicle is not driven. Since the kinetic energy possessed is large, a predetermined engine brake cannot be obtained unless the capacity of the low reverse brake is large. Conversely, if the capacity of the low reverse brake is large at a low vehicle speed, the kinetic energy of the vehicle is small, so that a large shock occurs when the low reverse brake is engaged. For this reason, at low vehicle speeds, lower the engine brake selection pressure for low reverse brake,
At a high vehicle speed, it is preferable to increase the engine brake selection pressure for the low reverse brake.

However, if the pressure reducing valve supplies a constant pressure to the low reverse brake as in the related art, both of these requirements cannot be satisfied, and one of them has to be sacrificed.

On the other hand, since the pressure reducing valve has the feedback orifice, when the engine brake command pressure is released, the engine brake selection pressure of the low reverse brake is released by releasing the engine brake command.
It acts to delay the release of the pressure, which hinders prompt release of the engine brake.

It is an object of the present invention to overcome these problems by adding a solenoid valve.

[0010]

SUMMARY OF THE INVENTION For the purpose of the former, the present invention comprises a friction element for engine braking in a forward travel range that is also used in a reverse travel range, and an engine brake selection pressure supplied to the friction element in the forward travel range. In the automatic transmission provided with a pressure reducing valve for reducing pressure, a pressure regulating solenoid valve for appropriately applying a control pressure in a direction for increasing the engine brake selection pressure to the pressure reducing valve is provided.

According to a second aspect of the present invention, for the purpose of the latter, a friction element for engine braking in a forward traveling range used in a reverse traveling range is provided, and the engine brake selection pressure supplied to the friction element in the forward traveling range is reduced. An automatic transmission provided with a pressure reducing valve is provided with a drain solenoid valve for applying a control pressure in a direction for decreasing the engine brake selection pressure to the pressure reducing valve in response to an engine brake release command.

[0012]

The automatic transmission operates the friction element for engine braking in the forward traveling range by the engine brake selection pressure supplied thereto, thereby enabling the engine brake traveling at the corresponding gear. On the other hand, the friction element for engine braking is also operated in the reverse travel range to enable reverse travel.

The engine brake selection pressure is reduced by the pressure reducing valve to be lower than the operating pressure of the friction element for engine braking in the reverse drive range, and the capacity of the friction element becomes excessively large during engine braking, causing a large engagement shock. Can be avoided.

The pressure regulating solenoid valve appropriately applies a control pressure in a direction for increasing the engine brake selection pressure to the pressure reducing valve. Therefore, at low vehicle speeds, the required engine brake friction element capacity is reduced as described above, and the engine brake selection pressure is reduced. At high vehicle speeds, the required engine brake friction element capacity is reduced. As described above, it is possible to perform control such that the engine brake selection pressure is increased in response to the large value, and the capacity of the engine brake friction element can always be made as required.

On the other hand, the drain solenoid valve applies a control pressure in a direction for decreasing the engine brake selection pressure to the pressure reducing valve in response to an engine brake release command. Therefore, the engine brake selection pressure to be released from the engine brake friction element at the time of the engine brake release command can be quickly drained, and quick engine brake release in response to the command can be realized.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the engine brake selection pressure control apparatus according to the present invention, which is described in the above-mentioned document having a low reverse brake LR / B as a friction element for an engine brake in a forward drive range used also in a reverse drive range. Of the present invention is applied to the automatic transmission described above. In this figure, for the sake of simplicity, only the portion of the shift control hydraulic circuit according to the present invention is extracted and shown, and other circuit portions are omitted.

In the figure, reference numeral 1 denotes a manual valve, which is P (parking) according to the driving mode (including parking and neutral) desired by the driver.
Range, R (reverse drive) range, N (neutral) range, D
The manual operation is performed in a range (automatic forward shift), two ranges (second speed engine brake range), or one range (first speed engine brake range). This manual valve 1 does not output the line pressure P _L to any port in the P and N ranges, thereby enabling the automatic transmission to be in a neutral state where power cannot be transmitted and enabling parking and stopping.
_L is output to the port 1a to enable the automatic transmission to automatically shift between the first to fourth forward speeds, and to set the line pressure P in two ranges.
Outputs _L to port 1b to the automatic transmission to the engine brake running state capable at the second speed, the low reverse brake will be described later and outputs the line pressure P _L to the port 1c in 1 range LR / the automatic transmission and the engine brake running state capable of the first gear I actuation coupled with the other friction element by operation of B, port 1 the line pressure P _L in R-range
d and the low reverse brake LR / B is actuated to bring the automatic transmission together with the operation of the other friction elements into a state in which the automatic transmission can travel backward.

The manual valve port 1d is connected to the input port of the shuttle valve 3 via the circuit 2, and the output port of the shuttle valve is connected to the low reverse brake LR / B. The other input port of the shuttle valve 3 is connected to a manual valve port 1c via a circuit 4, and a one-range pressure reducing valve 5
Insert The pressure reducing valve is the manual valve engine braking selection by depressurizing the line pressure P _L from the port 1c pressure P _B
This is supplied to the low reverse brake IR / B via the shuttle valve 3.

The pressure reducing valve 5 has a spool 5a, which is
5b and the spring 5c in this chamber
And the pressure in the opposite chambers 5d and 5e
It is urged to the right in the figure. Orifice for preventing pulsation is provided in chamber 5d
The engine brake selection pressure P_BThe feedback
The chambers 5b and 5e are respectively provided with a pressure regulating solenoid valve 7 and
And the drain solenoid valve 8
Constant pilot pressure P _PSupply.

When the solenoid valves 7 and 8 are OFF, the drain ports 7a and 8a are opened to put the chambers 5b and 5e in a non-pressure state.
And supplies ON at the pilot pressure P _P of the circuit 9 is closed these drain port chambers 5b, the 5e. The ON / OFF of the solenoid valves 7 and 8 is controlled by a controller 10. Therefore, a signal from a vehicle speed sensor 11 for detecting a vehicle speed V is input to the controller 10 and an inhibitor switch 1 for detecting a selection range of the manual valve 1.
2 is input.

The controller 10 executes the control program shown in FIGS. 2 and 3 based on the input information, and controls the engine brake selection pressure (P _B ) aimed at by the present invention by the pressure reducing valve 5. .

[0022] Figure 2 (determined from the signal of the inhibitor switch 12) manual valve 1 while the 1 range is repeatedly executed by the periodic interruption, first reads the vehicle speed V, then the vehicle speed V is the set value greater than or equal _to V ₀ Check whether the vehicle is traveling at high speed or at a lower speed. The high speed traveling, supplies the pilot pressure P _P in the chamber 5b of the pressure reducing valve 5 and ON the pressure regulating solenoid valve 7.

The operation of the pressure reducing valve 5 will now be described. When the pressure is not supplied to the chambers 5b and 5e, the spool 5a
Engine brake selection pressure P _B fed back to d
Strokes to a position where the spring force of the
Engine when the pressure to a value corresponding to the spring force of the engine braking selection pressure P _B spring 5c is to rise by receiving replenishment of the line pressure from the manual valve port 1c, greater than or equal to the value corresponding to the spring force brake selection pressure P _B is eliminated the excess from the drain port 5f result, the engine braking selection pressure P _B becomes a constant value corresponding to the spring force of the spring 5c as shown solid lines in FIG. 4.

Incidentally, as described above, the pressure regulating solenoid valve
7 ON, pilot pressure P in chamber 5b _PIs supplied,
Because the spring 5c is subsidized by that amount, the engine brake selection
Selective pressure P_BRises as shown by the dashed line in FIG.

On the other hand, when it is determined in FIG. 2 that the vehicle is traveling at a low speed of V <V ₀ , the pressure regulating solenoid valve 7 is turned off and the chamber 5 is turned off.
b is put in a non-pressure state. In this case since the pressure reducing valve 5 is no pressure to aid spring 5c, decreasing to a value indicating an engine braking selection pressure P _B by the solid line in FIG.

Therefore, when one range is required due to the need for engine braking at the first speed and the vehicle has a large kinetic energy during high vehicle speed running, the low reverse brake LR / B is actuated to receive the kinetic energy. Pressure P
By increasing _B to increase the brake capacity, and conversely, when driving at low vehicle speeds, the operating pressure of the low reverse brake can be reduced to reduce the brake capacity. The engine brake can be reliably applied while it is in operation.

FIG. 3 shows a control program for switching from one range to another range when the engine brake at the first speed becomes unnecessary. When this engine brake release command is issued, first, the drain solenoid valve 8 is turned on, and this is set for a set time. After that, the drain solenoid valve 8 is turned off. When the pilot pressure P _P in the chamber 5e in ON of the drain solenoid valve 8 is supplied, the compartment 5d feedback pressure P _B is subsidized for causing in FIG rightward spool P5a, engine braking selection pressure P _B is It is drained from the port 5f and falls as shown by the broken line in FIG. Thus when the engine brake release command, while where become delayed slightly missing engine braking selection pressure P _B by the presence of the orifice 6 would otherwise, the promptly consummates engine brake this omission can be released quickly.

[0028]

As described above, the engine brake selection pressure control device according to the present invention has a structure in which the engine brake selection pressure can be appropriately increased by the pressure regulating solenoid valve. The capacity of the friction element for use can be matched with the demand one by one, and the problem that a shock occurs due to an excessive capacity or that a predetermined engine brake cannot be obtained due to an insufficient capacity can be solved.

Further, the engine brake selection pressure control device of the present invention is configured such that the engine brake selection pressure is reduced by the drain solenoid valve at the time of the engine brake release command. The release of the pressure can be completed promptly, and the release of the engine brake corresponding to the command can be promptly achieved.

[Brief description of the drawings]

FIG. 1 is a main part hydraulic circuit diagram of an automatic transmission showing an embodiment of an engine brake selection pressure control device of the present invention.

FIG. 2 is a flowchart of a control program executed by the controller of the example during selection of one range.

FIG. 3 is a flowchart of a control program executed by the controller of the same example when one range is released.

FIG. 4 is a characteristic diagram of an engine brake selection pressure control of the example device.

[Explanation of symbols]

1 Manual valve 3 Shuttle valve 5 Pressure reducing valve 6 Feedback orifice 7 Pressure regulating solenoid valve 8 Drain solenoid valve 10 Controller 11 Vehicle speed sensor 12 Inhibitor switch LR / B Low reverse brake (friction element for engine brake)

Claims (2)

(57) [Claims] 1. An automatic transmission having a friction element for engine braking in a forward traveling range used also in a reverse traveling range and having a pressure reducing valve for reducing an engine brake selection pressure supplied to the friction element in the forward traveling range. An engine brake selection pressure control device for an automatic transmission, further comprising a pressure adjusting solenoid valve for appropriately applying a control pressure in a direction for increasing the engine brake selection pressure to the pressure reducing valve. 2. An automatic transmission having a friction element for engine braking in a forward traveling range used in a reverse traveling range and having a pressure reducing valve for reducing an engine brake selection pressure supplied to the friction element in the forward traveling range. An engine brake selection pressure control device for an automatic transmission, further comprising a drain solenoid valve for applying a control pressure in a direction for decreasing the engine brake selection pressure to the pressure reducing valve in response to an engine brake release command.