192 clutches and power-stop control – Clutches – Operators
Patent
1988-11-22
1991-07-30
Lorence, Richard
192 clutches and power-stop control
Clutches
Operators
192 8711, 192 109F, 137486, 13762565, 91433, F16D 2511
Patent
active
050353128
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for controlling a hydraulic pressure usable for a clutch and more particularly to an apparatus of the foregoing type which assures that detection of filling and detection of a clutch pressure are carried out by a simple electronic control type valve arrangement to prevent an occurence of double engagement with clutches and speed changing is smoothly achieved.
BACKGROUND ART
FIG. 15 illustrates a hitherto widely employed control for speed changing with a transmission. In the illustrated case, speed changing from a first speed to a second speed is taken into account. This conventional control for speed changing is such that a clutch for the first speed is turned off when a command for speed changing is outputted and at the same time a hydraulic oil starts to flow in a clutch for the second speed. Consequently, a hydraulic pressure in the clutch for the first speed is lowered from a predetermined pressure to a level of zero when the command for speed changing is outputted, while a hydraulic pressure in the clutch for the second speed starts to increase gradually after a period of filling time t.sub.f elapses. This filling time t.sub.f designates a period of time required for filling the interior of a clutch pack of the clutch for the second speed with a hydraulic oil.
In this manner, with the conventional apparatus, the time t.sub.f that elapses until the clutch pack is filled with a hydraulic oil is reserved and no torque is transmitted during the period of time t.sub.f. This causes a so-called breathing phenomenon to appear during a period of speed changing with the conventional apparatus and the breathing phenomenon gives rise to a problem concerning running performances such as riding comfortability, acceleration characteristic or the like. Particularly, with respect to a large-sized construction machine, a period of filling time is prolonged due to a large capacity of respective clutches, which has a substantial effect on running performances.
In view of the foregoing problems, in the recent years attention has been paid to a crossover control as disclosed in an official gazette of Japanese Laid-Open Patent NO. 13758/1963 and the crossover control has been lately carried out using electronic type pressure control valves. Specifically, according to the prior invention as proposed by the inventors under Japanese Patent Application NO. 271055/1985, a crossover control as shown in FIG. 16 is carried out using an electronic modulation system for all clutches to prevent an occurrence of breathing during a period of speed changing due to the presence of filling time.
The proposal as shown in FIG. 16 is such that when a command for speed changing is outputted, a hydraulic oil starts to flow in a clutch for the second speed to be next brought in an engaged state, thereafter when the termination of filling is detected, a clutch for the first speed which has been previously brought in an engaged state is turned off and a bulid-up control is initiated for the clutch for the second speed.
According to this proposal, an occurrence of breathing phenomenon due to the presence of filling time t.sub.f is not only prevented reliably but also speed changing can be smoothly achieved, resulting in improved running performances being assured. However, to properly carry out such speed changing, it is required that the filling time t.sub.f is exactly detected and an occurrence of double engagement is prevented without fail.
Hitherto, detection of the filling has been performed by properly controlling a pattern with which a hydraulic pressure is gradually increased as time elapses after a command for speed changing is outputted. Specifically, hitherto, a time required for filling the clutch pack with a hydraulic oil is suitably set on the basis of prior experiments, the termination of filling is identified when the set time elapses after a command for speed changing is outputted, and thereafter a hydraulic pressure is increased gradually.
However, it has been found
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Asayama Yoshio
Okura Yasunori
Sato Takayuki
Tsubota Makio
Kabushiki Kaisha Komatsu Seisakusho
Lorence Richard
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