Vehicular transmission

A vehicular transmission includes a gear-change mechanism section that shifts power from a driving source and outputs the power to an output shaft; and a hydraulic system that supplies hydraulic pressure from an oil pump to the gear-change mechanism section via a check valve. The check valve includes a cylindrical valve case in which a passage is formed, a valve stored within the valve case so as to be freely movable in an axial direction of the valve case, a valve seat that is formed at one end portion of the passage in the valve case and that closes the passage when the valve sits thereon, a spring for urging the valve so as to sit on the valve seat, and a spring seat fixed on an axially opposite side of the valve seat in the valve case to support the spring.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2005-333250 filed on Nov. 17, 2005 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a vehicular power transmission.

A hybrid vehicle with an internal combustion engine and an electric motor as driving sources includes a hybrid power transmission. The hybrid power transmission requires a motor-operated pump driven by the electric motor and a mechanical pump driven by the driving sources in order to stop the driving sources (and thus stop the vehicle). When either one of the mechanical pump or the motor-operated pump operates and the other is stopped, it is necessary to interpose a check valve in a supplying passage that supplies hydraulic pressure from a hydraulic pump to a hydraulic system. The check valve prevents the hydraulic pressure from the operative pump from escaping from the side of the stopped pump, as disclosed in Japanese Patent Laid-open No. 2001-41066 (FIG. 5), for example.

Specifically, the check valve is mostly disposed within a valve body adjacent to a case for storing a gear-change mechanical section. The check valve is so disposed because the hydraulic pressure is supplied from the mechanical pump (disposed in the gear-change mechanical section) to the valve body, in which a regulator valve and the like is disposed in the supplying passage from the mechanical pump.

SUMMARY

While the check valve is arranged in general such that a ball of the check valve is stored in a hole formed in the valve body, the passage is closed when the ball is biased by a spring and sits on a valve seat. Fluid flows through the passage by moving the ball against the spring as the hydraulic pressure acts on the passage. Furthermore, there is a case when the fluid flown into the passage flows in a direction crossing to a direction in which the ball is movable. For example, when the valve seat is formed in the case that stores the gear-change mechanical section, the fluid from the mechanical pump flows within the valve body from the valve seat by passing the passage formed in the case, moves the ball by going against the spring and flows within the valve body so as to cross the ball. The ball also eccentrically hits against the valve seat because a clearance from the hole for storing the ball is large. As a result, a passage part (referred to as a guide part hereinafter), including the valve seat where the ball moves and slidably abuts eccentrically, becomes worn and is eventually damaged. As a result, the durability of the check valve drops and the pressure drops because of leaking fluid.

Specifically, because the supplying passage of the mechanical pump becomes a passage of main line pressure in running the vehicle when the gear-change mechanical section is operative, the above-mentioned problem of durability is soon realized because a large amount of fluid flows through the valve case. Then, there is a possibility that pressure loss becomes large and fuel consumption drops.

The invention thus provides, among other things, a vehicular transmission that solves the above-mentioned problems by using a check valve arranged such that a ball will not eccentrically hit against a guide part.

The invention according to a first exemplary aspect includes a vehicular transmission with a gear-change mechanism section that shifts power from a driving source and outputs the power to an output shaft; and a hydraulic system that supplies hydraulic pressure from an oil pump to the gear-change mechanism section via a check valve. The check valve includes a cylindrical valve case in which a passage is formed, a valve stored within the valve case so as to be freely movable in an axial direction of the valve case, a valve seat that is formed at one end portion of the passage in the valve case and that closes the passage when the valve sits thereon, a spring for urging the valve so as to sit on the valve seat, and a spring seat fixed on an axially opposite side of the valve seat in the valve case to support the spring, wherein the check valve is structured such that (1) fluid flows into the valve case from the valve seat, along the axial direction of the valve case and out of outflow ports and (2) such that a direction of flow of the fluid within the valve case almost coincides with a movable direction of the valve.

The invention according to a second exemplary aspect includes a check valve with a cylindrical valve case in which a passage is formed; a valve stored within the valve case so as to be freely movable in an axial direction of the valve case; a valve seat that is formed at one end portion of the passage in the valve case and that closes the passage when the valve sits thereon; a spring for urging the valve so as to sit on the valve seat; and a spring seat fixed on an axially opposite side of the valve seat in the valve case to support the spring, wherein the check valve is structured such that (1) fluid flows into the valve case from the valve seat, along the axial direction of the valve case and flows out of outflow ports and (2) such that a direction of flow of the fluid within the valve case almost coincides with the movable direction of the valve.

DETAILED DESCRIPTION OF EMBODIMENTS

A mode for carrying out the invention will be explained with reference toFIGS. 1 through 4C.FIG. 1is a schematic drawing of a driving system of a hybrid vehicle of the invention,FIG. 2is a drawing showing a section of a check valve by enlarging a part of a vehicular power transmission,FIG. 3shows an oil passage of the check valve of the embodiment andFIGS. 4A-4Care section views of the check valve, respectively.

A structure of a hybrid transmission to which the invention is applied will first be explained with reference toFIG. 1. In the hybrid power transmission1, an input shaft17of a gear-change mechanical section10is connected to a crank shaft2aof an engine2via a damper unit (not shown) and a carrier CR1of a power distributing planetary gear5. The power distribution planetary gear5is a simple planetary gear connected to the input shaft17via a hub member18. The carrier CR1has pinions P1rotatably supported by side plates (not shown). A rotor shaft19of a first motor3is connected to a sun gear S1that gears with the pinions P1. A ring gear R1is also connected to the pinions P1and the ring gear R1is connected with a drum-like supporting member20and is connected to a transmission shaft21via the supporting member20.

A stepped transmission6having a planetary gear unit6ais connected to a rear end (right side in the figure) of the transmission shaft21. Specifically, a carrier CR2of the planetary gear unit6ais connected to the transmission shaft21via a hub member22. The carrier CR2has long pinions P2and P4and a short pinion P3(referred to simply as a pinion P3hereinafter). The pinion P2of a small diameter part and the pinion P4of a large diameter part are formed in a body as the long pinion and the pinion P3gears with the pinion P2of the small diameter part.

The sun gear S2gears with the pinion P3and is connected with a rotor shaft23of a second motor4. A sun gear S3gears with the pinion P4and is connected with a hub member24. A friction plate of a first brake B1, that is a multi-plate brake, is engaged with the hub member24and the first brake B1is freely anchored by line oil supplied from a regulator valve.

The pinion P3gears with a ring gear R2and a friction plate of a second brake B2, that is a multi-plate brake, is engaged with the ring gear R2. The second brake B2is freely anchored by line oil supplied from the regulator valve.

Then, the transmission shaft21is connected to an output shaft26of the gear-change mechanical section10. The output shaft26is linked with a differential unit via a coupling and a propeller shaft (not shown) and is further connected to driving wheels16, rear wheels, via the differential unit and right and left driving shafts.

Hydraulic pressure is supplied to a valve body40having, for example, a regulator valve. A mechanical oil pump11is powered by the engine2in order to operate the gear-change mechanical section10or to lubricate each sliding section. The hybrid power transmission1is also provided with a motor-operated oil pump12that is driven independently of the mechanical oil pump11. The motor-operated oil pump12is driven by an electric motor13to which electric power is supplied from an inverter for the motor-operated oil pump12. When the engine2is idling or is stopped for example, the hybrid power transmission1that is linked with the engine2also stops. The motor-operated oil pump12is thus mainly driven when the hybrid power transmission1is in the stopped state to assure hydraulic pressure of a hydraulic control unit.

The mechanical oil pump11and the motor-operated oil pump12are connected in parallel with respect to the hydraulic control unit. As such, when the motor-operated oil pump12operates when the mechanical oil pump11is stopped, the hydraulic pressure generated by the motor-operated oil pump12flows backward to the mechanical oil pump11and hydraulic pressure necessary for the hydraulic control unit cannot be supplied. As a measure for this, a hydraulic check valve70prevents the hydraulic pressure from flowing backward to the mechanical oil pump11.

Next, a structure of the check valve70(backflow preventing valve) of the invention will be explained.FIG. 2shows a section of the check valve70by enlarging a part of the gear-change mechanical section10. The check valve70is disposed in a valve body fixed at a lower part of a mission case41such that its axial line is almost coincident with a direction of gravity. Oil pressurized by the mechanical oil pump11is supplied to an upper part of the check valve70via an oil passage (not shown) within the mission case41. The pressurized oil then presses down a ball73(which is a valve positioned at the upper part of the check valve70in the figure) while compressing a spring74. Then, a gap is produced between a valve seat72aof the valve case72and the ball73, thus creating a passage where the oil flows (FIG. 4A).

Meanwhile, when pressure of the passage on the side of the mechanical pump is negative with respect to the hydraulic control unit, the oil flows into the check valve70from a lower part thereof inFIG. 2and the ball73in the check valve70abuts against the valve seat72aof the valve case72in linkage with the flow of the oil. Thus, it becomes possible to shut off the oil flow passage and to prevent the oil from flowing backward.

The flow passage of the oil will now be explained with reference toFIG. 3. The oil30flowing in from a return passage from a hydraulic circuit and the oil31suctioned from an oil pan through a strainer are lead to the mechanical oil pump11and the motor-operated oil pump12connected in parallel. The pumps11and12are arranged so that either one operates appropriately. For example, when the mechanical oil pump11stops and the motor-operated oil pump12operates due to idling, the motor-operated oil pump12pumps out the oil to the check valve32that is connected with an outflow port to supply oil to a regulator passage33and a lubricant passage34, i.e., to a side of hydraulic load.

Meanwhile, because a short-circuit passage to the original oil flow-in passage via the check valve70and the stopped mechanical pump11is branched beside the supplying passages33and34to the load side in this oil flow circuit, the check valve70that plays the role of a one-way valve is interposed to prevent the oil from flowing into the short-circuit passage by shutting off the short-circuit of the hydraulic circuit.

Next, a mechanism of the check valve70will be explained.FIG. 4Ais a section view of the check valve70in a direction of a side face thereof,FIG. 4Bis a plan section view of the check valve70taken along an A-A line andFIG. 4Cis a plan section view of the check valve70taken along a B-B line. The check valve70is composed of the cylindrical valve case72within which the passage is formed, the ball73disposed within the valve case72so as to be slidable in an axial direction, i.e., in a longitudinal direction of the valve case72, the valve seat72athat is formed at one end portion of the passage of the valve case72and that closes the passage when the ball73seats thereon, a spring74that urges the ball73so that it seats on the valve seat72aand a spring seat71fixed on the axially opposite side from the valve seat72aof the valve case72.

The valve case72has a screw thread72cformed around an outer periphery of an upper part thereof and is fixed by screwing the screw thread72cinto a female screw (not shown) formed at an opening of the oil passage. The lower part of the valve case72is inserted into an opening hole composing an oil passage for supplying hydraulic pressure of the valve body40. It is noted that the opening of the oil passage for supplying hydraulic pressure of the mission case41is oil-tightly jointed with the oil passage for supplying hydraulic pressure of the valve body40and a flange72dof the valve case72is oil-tightly jointed with the mission case41. Then, in a state when the valve case72is thus mounted, the check valve70is disposed so that its axial direction, i.e., the longitudinal direction thereof, almost coincides with a direction of gravity. An inflow port72fand the valve seat72aagainst which the ball73abuts are formed at the upper part of the valve case72and an oil-tight state or a state in which the oil is allowed to pass is brought about depending on a movement of the ball73.

Further, a plurality of (three for example) straight concave channels72bare formed along the axial direction on an inner peripheral face of the valve case72from the lower part of the valve seat72ato a terminal of the valve case72. The concave channel72bbecomes a passage for guiding the oil flowing from the valve seat72ato the terminal of the valve case72. There is provided a supporting section72e, formed to be concentric with the valve case72between the concave channels72b, for slidably supporting the ball73. These concave channels72band the supporting sections72eform the passages and can also restrict the movement of the ball73so that it is freely movable only along a radial center of the valve case72in the axial direction. Therefore, the ball73can sit on the valve seat72awhile keeping an axial center of the ball73always concentric with an axial center of a seat face of the valve seat72a. Still more, because the concave channel72bbecomes the passage, it is advantageous from an aspect of reducing loss resistance to be straight and to have a large sectional area, it is desirable to provide many concave channels72bor to provide the concave channel72bhaving a large sectional area. Meanwhile, from the necessity that the supporting section72erestricts the movement of the ball73in the radial direction within the valve case72, it is required to abut against the peripheral face of the ball73by contact points of at least three or more. There is a mutual relationship between the area of the concave channel72band a number of the supporting section72eand it must be appropriately selected from the oil passing loss resistance and mobility of the ball73.

Next, while the ball73(which is an example of a valve) is preferably a globular ball from the necessity of bringing about the oil-tight state by sliding within the valve case72and by abutting against the valve seat72a, it is also possible to adopt a round column whose face of abutment is a plane face, a circular cone whose face of abutment is a slope or a disk-like plain plate as long as it is possible to form the oil-tight state. However, it is desirable to adopt the shape of the ball in order to reduce loss resistance without hampering a streamline along which the oil flows. Still more, the ball73is urged toward the valve seat72aby the spring74supported by the spring seat71and the ball73abuts against the valve seat72ain a normal state. The ball73slides and forms the passage only when force in a direction going against the urging force of the spring74is applied.

One end portion of the spring74abuts against a spring seat75provided in the spring seat71and is disposed so as to cover an outer periphery of a stopper section75aand is supported so as to be movable in the compressing direction of the spring74. Meanwhile, the other end of the spring74abuts against the ball73and the ball73is capable of moving in the vertical direction along with the movement of the spring74. Because the urging force of the spring74is determined by a diameter of the spring wire and a number of windings, the wire diameter and the number of windings are determined so that the spring74can exhibit the least urging force that enables the ball73to abut against the valve seat72a.

Next, the spring seat71is inserted into the valve case72from the lower end of the valve case72together with the ball73and the spring74, and engages in a body with the supporting sections72ethat form the inner periphery of the valve case72such that the engagement will not be disengaged even if hydraulic pressure acting within the valve case72is applied. The spring seat75has a pedestal and is smaller than the outer diameter of the spring seat71and the columnar stopper section75athat extends from the spring seat75. The spring seat75is the face against which the spring74abuts as described above and the stopper section75ahas an apex for restricting the vertical movement of the ball73at the upper end thereof. Thereby, the ball73is restricted to move only between the valve seat72aand the apex of the stopper section75ato prevent the ball73from largely sliding within the valve case72. It is noted that a range of an inner wall face of the valve case72, where the ball73restricted by the stopper section75aslidably contacts the valve seat72a, is a guide part where eccentric abrasion may occur. Still more, the stopper section75ahas a perforated hole76dthat penetrates through the spring seat71to the vicinity of the apex of the stopper section75aas a passage described later. The stopper section75aalso has a through hole76bformed to guide the oil passed through the concave channel72bof the valve case72to the through hole76bby the side portion thereof.

The oil flown into the valve case72via the inflow port72fand through the gap between the valve seat72aand the ball73partially passes through the concave channel72bof the valve case72and flows out of the valve case72from the outflow port76athat corresponds to the lower end of the concave channel72b. A part thereof is guided to the perforated hole76dvia a through hole76bprovided in the stopper section75aand is flown out of the valve case72from the perforated hole76dvia the through hole76bprovided in the stopper section75a. Thereby, a straight oil passage may be formed, there are two oil outflow passages of outflow ports76aand76c, the oil flown into the valve case72is guided to the outside without causing loss and loss of pressure otherwise caused in the check valve70may be suppressed to the minimum.

It is noted that although the check valve interposed in the supplying fluid passage from the mechanical pump has been explained in the embodiment, the invention is also applicable to the check valve interposed in the supplying fluid passage from the motor-operated pump. Still more, although the invention has been applied to the hybrid transmission as a vehicular transmission, the invention is not limited to that and is applicable to other vehicular transmissions such as an automatic transmission in the same manner.

According to an exemplary aspect of the invention, the check valve in which the valve is stored in the valve case formed in a body with the valve seat is used, so that the movement of the valve is restricted in the axial direction of the valve case and the flow of the fluid almost coincides with the movable direction of the valve. Accordingly, the valve will not eccentrically hit against a guide part including the valve seat (referred to typically as a valve seat) and it becomes possible to prevent eccentric abrasion of the valve seat otherwise caused by the eccentric hitting and to prolong the life of the check valve.

According to an exemplary aspect of the invention, the ball is used as the valve and the stopper section restricts a movable range of the ball. Therefore, the movable direction of the ball almost coincides with the direction of gravity, no load otherwise caused by the gravity will not act on the ball and it becomes possible to prevent the ball from eccentrically hitting against the valve seat more steadily while keeping smooth the movement of the valve (ball) within the valve case.

According to an exemplary aspect of the invention, the check valve is applied to the supplying oil passage from the mechanical pump that is a main oil passage of the transmission for hybrid vehicles, so that it is possible to solve the problems concerning the durability of the check valve, to prevent pressure loss from increasing and to keep high performance of fuel consumption for a long period of time.

According to an exemplary aspect of the invention, the check valve is fixed to the case of the gear-change mechanical section and is disposed between the valve body such that the longitudinal direction of the check valve conforms to the vertical direction, so that it becomes possible to prevent the eccentric abrasion of the valve from occurring that is otherwise caused by the eccentric hitting against the valve seat.

According to an exemplary aspect of the invention, the concave channels formed on the inner peripheral face of the valve case become the passages and the ball can move along the axial line accurately while contacting with the inner peripheral face of the valve case, so that it is possible to steadily prevent the eccentric abrasion from occurring that is otherwise caused by the eccentric hitting against the valve seat.

According to an exemplary aspect of the invention, there are the plurality of concave channels and outflow ports, so that it is possible to smoothen the flow of the fluid in the check valve and to prevent pressure loss from increasing.

According to an exemplary aspect of the invention, the outflow port is the opening continuous to the concave channel, so that the flow of the fluid in the check valve is smooth. Still more, the holes are made through the stopper section as outflow ports, and the flow of the fluid thus becomes smoother.

According to an exemplary aspect of the invention, the check valve is separately made from the valve body and is fixed to the case for storing the automatic gear-change mechanical section, so that it is possible to prevent an oil amount within the valve case from being unbalanced in assembling the valve body to the case.