Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1988-03-01
1990-07-24
Braun, Leslie A.
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
74869, B60K 4110
Patent
active
049427822
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reverse shift control device for preventing an automatic transmission from shifting to reverse even if a shift lever is mistakenly manipulated to R range.
2. Description of the Prior Art
In an automatic transmission in general, if a shift lever is manipulated to R range, a sudden engine brake is applied even if an automobile is traveling forward.
Under such circumstances in automatic transmissions, a solenoid valve for anti-reverse and a switching valve, or a solenoid valve for a reverse clutch to prevent an automatic transmission from assuming a reverse condition even if a shift lever has been moved to R range, have been proposed.
However, the above-mentioned automatic transmissions must include exclusive solenoid valves, or other expensive valves; accordingly, the cost of such automatic transmissions is relatively high. Further, the recent demand for front-mounted front wheel drive engines and multiple speed transmissions require severe space restrictions for installation than ever.
SUMMARY OF THE INVENTION
Thus an object of the present invention is to utilize shift valves and a solenoid valve to prevent an automatic transmission from assuming a reverse condition while the vehicle is running at a high speed, and more particularly to provide a reverse shift control device in an automatic transmission for performing the above function. above, and shown in FIG. 1 as an example.
In a hydraulic control device of an automatic transmission having hydraulic servos (C), (B) of certain frictional engaging components of a transmission gear mechanism, shift valves (11), (12), (13), (16), (15) to control oil pressure applied to each hydraulic servo, solenoid valves (S1) , (S2), (S3) to control the shift valves, a manual valve (10), respective ones of the shift valves (11), (12) have ports (Rc), (2k) to which line pressure is applied in a reverse range of the manual valve (10), and have ports (2i), (2l) which connect a hydraulic servo (B.sub.3) of a frictional engaging component (1st & reverse brake, for example) operated when the vehicle assumes the reverse condition. When the manual valve is at R range and the speed of the vehicle is greater than a predetermined speed (7 km/h for example), a controller (U) sends signals to the solenoid valve (S1) which controls the shift valves (11) and (12). Based on signals from controller (U), the shift valves (11), (12) are shifted so that the ports (Rc, 2j) and (2k, 2l) are disconnected.
In the above-described structure, when the manual valve (10) is at R range, line pressure is applied from a port (R) to a second clutch servo (C.sub.2) through oil paths (Ra), (Rd) and (Re). Line pressure in oil path (Ra) is applied to a port (Rc) of the shift valve (12).
When the vehicle stops or runs at less than a predetermined speed, the first solenoid valve (S1) is switched "OFF", and the first and second shift valves (11), (12) assume the "upper half position". Consequently, line pressure in the port (Rc) is applied to a brake servo (B.sub.3) (a frictional engaging component operated when in reverse) through the port (2i), the coil path (2j), and the ports (2k), (2l) of the first shift valve (11), and an oil path (2m). Then, the automatic transmission assumes the reverse condition, which causes the vehicle to traveling reverse.
On the other hand, when the vehicle is traveling forward at more than a predetermined speed, the controller (U) sends signals to switch the first solenoid valve (S1) "ON". Then, the solenoid valve (S1) assumes a "drain condition", and the shift valves (11) and (12) are shifted to the "lower half position". Due to this operation of the shift valves, the ports (Rc and 2j) and (2k and 2l) are disconnected, and the brake servo (B.sub.3) is drained because the port (2l) and a drain port are connected. Consequently, the automatic transmission is prevented from assuming the reverse condition.
As explained above, according to the present invention, when the manual valve (10) is shi
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Kuwayama Yoshinari
Miura Masakatsu
Yokoyama Fumitomo
Aisin-Warner Kabushiki Kaisha
Braun Leslie A.
Macris Harold F.
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