Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Fluid pressure actuator for adjustment of member
Reexamination Certificate
2002-05-15
2004-02-17
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Fluid pressure actuator for adjustment of member
Reexamination Certificate
active
06692388
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulic controller which comprises a choking element for an internal oil passage (especially, a choking element that is generally referred to as “choke passage”).
Furthermore, the present invention relates to a hydraulic controller which generates a signal pressure by using an above mentioned choking element so as to control the operation of a transmission. The present invention relates particularly to a hydraulic controller which provides a signal pressure that corresponds to the rotation of the engine and is used, for example, for operating the starting clutch of the transmission.
BACKGROUND OF THE INVENTION
For hydraulically executing the shift control of a transmission, various types of hydraulic controller have been known, and hydraulic controllers have been incorporated in transmissions for hydraulic shift control. Such a hydraulic controller includes a regulator valve, which is used to adjust and produce a line pressure from oil supplied by an oil pump. This line pressure is then used for producing various control pressures to execute, for example, the shift control of the transmission. The part of the oil that is supplied from the pump to the regulator valve but not used for the line pressure to execute various control operations is discharged from the regulator valve. This discharged oil is used for lubricating the internal mechanisms of the transmission. For performing the lubrication, the hydraulic controller includes various lubrication control valves to control appropriately the pressure necessary for distributing a predetermined amount of lubrication oil to each internal mechanism.
In many cases, such a hydraulic controller includes many choking elements (various orifices and chokes), which are provided to oil passages in the transmission. For example, Japanese Laid-Open Patent Publication No. H04(1992)-254057 discloses a hydraulic controller which has hydraulic control valves and a separator plate between them on a side of the housing of the transmission. In this hydraulic controller, the separator plate is provided with a plurality of small apertures, i.e., choking elements (orifices).
Choking elements can be provided in this way, i.e., as orifices formed in the separator plate, but the choking elements provided in this way cannot be highly viscosity-sensitive choking elements, i.e., choking elements whose passage lengths are longer than their diameters, disclosed, for example, in Japanese Utility-Model Publication No. H07(1995)-20437. By the way, a control valve can be provided with a choking element formed in the valve body thereof. However, choking elements are small apertures, so it is difficult to form choking elements in a casting process. They must be formed by machining, for example, by drilling. As choking elements are difficult to form, the machining cost is relatively high.
Furthermore, if apertures formed in the separator plate are to be used as orifices, then the apertures must be connected to oil passages provided on one side of the separator plate and to other oil passages provided on the other side thereof, so that oil can flow continuously. Because of this reason, if orifices are to be provided in passages formed in the valve body that is provided on one side of the separator plate, then it is relatively difficult to use small apertures formed in the separator plate as orifices.
Moreover, generally, a vehicular transmission comprises a starting clutch, which is provided between the input member and the output member of the transmission, the input member being driven by a prime mover (engine) and the output member being connected to wheels of a vehicle. In this arrangement, the starting clutch typically being actuated hydraulically controls the engagement of the input and output members, for example, in starting or stopping the vehicle. Such an engagement control is executed generally in correspondence to the rotational speed of the prime mover. In such a case, the rotational speed of the prime mover is detected by a sensor, which generates a signal representing the rotational speed. This signal is used to control the operation of an electrically controlled valve, which produces a control pressure used for the engagement control.
In such a hydraulic control that utilizes an electrically controlled valve, a control failure can occur if electrical trouble (for example, a problem that the control system cannot start up) or an open stick (a condition where a valve spool sticks and stays open) happens. To avoid a control failure, the controller is often equipped with a backup system that utilizes a valve to generate a signal pressure in correspondence to the rotational speed of the prime mover, and then this signal pressure is used for the engagement control in backup operations. For example, a Pitot-tube is used to generate the signal pressure for the execution of the engagement control (refer to Japanese Laid-Open Utility-Model Publication No. S63(1988)-30662, Japanese Laid-Open Patent Publication No. H06(1994)-26565, etc.). However, this arrangement presents a new problem of the size of the transmission becoming large as it requires a space for the placement of a Pitot-flange.
In consideration of the above disadvantages, the applicant of the present invention has proposed a hydraulic controller disclosed in Japanese Laid-Open Patent Publication No. H11(1999)-257445. This hydraulic controller comprises an oil pump which is driven by the engine to deliver oil by the amount that corresponds to the rotational speed of the engine. The oil delivered from the oil pump is led into an oil passage with an orifice, and the above mentioned signal pressure for the engagement control is produced from the pressure difference created by the orifice, i.e., the difference in the pressure before and after the orifice in the flow.
As long as the temperature and viscosity of the oil does not change, the pressure difference created by the orifice changes in correspondence to the flow of the oil. This condition enables the production of the signal pressure that corresponds to the flow of the oil, i.e., to the rotational speed of the engine, which drives the oil pump. However, if the temperature of the oil changes, and the viscosity changes accordingly, then there is a change in the pressure difference even though the flow is kept constant. Because of this adverse effect, the signal pressure produced through the orifice when the oil is at a low temperature is higher than when the oil is at a high temperature. If the signal pressure is used in this condition, then the engagement control is not performed smoothly.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a hydraulic controller which utilizes a choking element formed in a separator plate.
It is another object of the present invention to provide a hydraulic controller whose construction enables formation of a choking element in a separator plate, for a passage provided in a valve body, which is provided on one side of the separator plate.
It is yet another object of the present invention to provide a hydraulic controller which always produces a signal pressure that corresponds to the rotation of the engine, from a pressure difference created through an orifice even though the temperature of the oil fluctuates.
A hydraulic controller according to the present invention is equipped with a first valve body, a second valve body and a separator plate, which is sandwiched between the first and second valve bodies. Also, the hydraulic controller comprises an upstream hydraulic control element (for example, the SC shift valve
92
described in the following preferred embodiment), a downstream hydraulic control element (for example, the SC backup valve
94
in the following embodiment), a connection oil passage (for example, oil passage
103
in the following embodiment) and a choking element (for example, the choke
75
in the following embodiment). The upstream hydraulic control element is provided on an upstream side for hydraulic contr
Kunii Hisashi
Narai Katsuyuki
Nirasawa Hideo
Urano Junji
Yamaguchi Akihiro
Hannon Thomas R.
Honda Giken Kogyo Kabushiki Kaisha
Lahive & Cockfield LLP
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