# Patent

## Title
Vertical fluid power transmission and outboard engine system

## Abstract

A vertical fluid power transmission includes: a vertical crankshaft of an engine; a vertical output shaft; and a vertical torque converter disposed between the crankshaft and the output shaft. An oil supply passage is connected to one end of the circulation circuit of the vertical torque converter, and guides a stored oil that is drawn up from an oil tank and discharged by an oil pump. An oil return passage is connected to the other one end of the circulation circuit, and leads to the oil tank. A normally-closed pressure response valve is provided in the oil return passage. The pressure response valve is opened by an upstream pressure. Thus, the oil tank for storing a working oil of the torque converter is separated from the torque converter, thereby downsizing the torque converter, and the working oil is circulated between the oil tank and the circulation circuit of the torque converter, thereby promoting cooling of the working oil.

## Background
RELATED APPLICATION DATA
The present invention is based upon Japanese priority application Nos. 2006-145961, 2006-145965 and 2006-145966, which are hereby incorporated in their entirety herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement of a vertical fluid power transmission comprising: a crankshaft of an engine, the crankshaft having an axis in a vertical direction; an output shaft having an axis in a vertical direction; and a torque converter which has an axis in a vertical direction, and is disposed between the crankshaft and the output shaft; the torque converter including a pump impeller connected to the crankshaft, a turbine runner connected to the output shaft so as to be opposed to the pump impeller, a stator arranged between the pump impeller and the turbine runner, and a circulation circuit of a power transmission oil, the circuit being defined between the pump impeller, turbine runner and stator. The present invention also relates to an improvement of an outboard engine system equipped with the above-described vertical fluid power transmission.
2. Description of the Related Art
Such a vertical fluid power transmission is already known as disclosed in U.S. Pat. No. 3,407,600.
In the vertical fluid power transmission disclosed in U.S. Pat. No. 3,407,600, an oil reservoir is formed in a lower portion of a circulation circuit of a torque converter so as to supply a working oil utilizing centrifugal force, and the torque converter is of a sealed-type. Therefore, the torque converter has an increased size due to the inner oil reservoir. Further, because the torque converter is the sealed-type, the working oil in the circulation circuit disadvantageously obtains a poor cooling and thus is easy to be deteriorated.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the above circumstances, and has an object of the present invention is to provide a vertical fluid power transmission wherein an oil tank for storing a working oil of a torque converter is separated from the torque converter, thereby downsizing the torque converter, and the working oil is circulated between the oil tank and a circulation circuit of the torque converter, thereby promoting cooling of the working oil.
In order to achieve the above object, according to a first feature of the present invention, there is provided a vertical fluid power transmission comprising: a crankshaft of an engine, the crankshaft having an axis in a vertical direction; an output shaft having an axis in a vertical direction; and a torque converter which has an axis in a vertical direction, and is disposed between the crankshaft and the output shaft; the torque converter including a pump impeller connected to the crankshaft, a turbine runner connected to the output shaft so as to be opposed to the pump impeller, a stator arranged between the pump impeller and the turbine runner, and a circulation circuit of a power transmission oil, the circuit being defined between the pump impeller, turbine runner and stator, wherein an oil supply passage is connected to one end of the circulation circuit, and guides a stored oil that is drawn up from an oil tank and discharged by an oil pump, wherein an oil return passage is connected to the other one end of the circulation circuit, and leads to the oil tank, and wherein a normally-closed pressure response valve is provided in the oil return passage, the pressure response valve being opened when an upstream pressure reaches a predetermined value.
With the first feature of the present invention, the oil tank for storing the working oil for the torque converter is separated from the torque converter, thereby downsizing the torque converter. In addition, the working oil is circulated between the oil tank and the circulation circuit of the torque converter through the oil supply passage and the oil return passage, thereby promoting the cooling of the working oil and preventing degradation of the working oil.
Also, because the oil return passage is provided with the normally-closed pressure response valve, when the engine is running, the pressure response valve is opened by the discharge pressure of the oil pump to provide communication to the oil return passage, thereby performing the circulation of the oil without problem. When the engine is stopped, the pressure response valve automatically closes to block the oil return passage, thereby preventing the oil from flowing out of the circulation circuit of the torque converter into the oil tank so as to maintain the circulation circuit in an oil-filled state. Therefore, the operational response of the torque converter can be enhanced.
According to a second feature of the present invention, in addition to the first feature, the oil supply passage is connected to an upper end of the circulation circuit.
With the second feature of the present invention, when the engine is stopped, the oil is prevented from flowing back from the circulation circuit into the oil pump, thereby maintaining the circulation circuit in an oil-filled state.
According to a third feature of the present invention, in addition to the second feature, a part of the oil supply passage comprises a vertical hole which is formed at a central portion of the output shaft and which has an upper end communicating with the circulation circuit.
With the third feature of the present invention, a part of the oil supply passage comprises the vertical hole of the output shaft, thereby simplifying the structure of the oil supply passage, and when the engine is stopped, the vertical hole prevents the oil from flowing back from the circulation circuit into to the oil pump.
According to a fourth feature of the present invention, in addition to any of the first to third features, the oil tank is arranged below the torque converter.
With the fourth feature of the present invention, the oil tank arranged below the torque converter further promotes the cooling of the circulating oil, because the oil tank is separated from the engine and is not heated much by the engine, and because the oil tank can be designed to have a relatively large capacity without any interference by the engine and the torque converter to allow a large amount of oil to flow to the circulation circuit. In addition, the engine, the torque converter and the oil tank are sequentially arranged from top to bottom, thereby downsizing a complete transmission comprising these components.
According to a fifth feature of the present invention, there is provided an outboard engine system comprising: a casing; an engine including a crankshaft and mounted in an upper part of the casing; a torque converter; an output shaft connected to the crankshaft through the torque converter; and a propeller shaft arranged below the output shaft to be driven by the output shaft; the torque converter, the output shaft and the propeller shaft being disposed in the casing; an oil tank disposed in the casing; an oil pump for drawing up a stored oil in the oil tank; a first oil supply passage for guiding the oil discharged from the oil pump to a portion to be lubricated in the engine; and a first oil return passage for returning the oil from the portion to be lubricated to the oil tank, wherein the outboard engine system further comprises: a second oil supply passage for guiding the oil discharged from the oil pump to a circulation circuit in the torque converter; and a second oil return passage for returning the oil from the circulation circuit to an intake side of the oil pump or to the oil tank.
With the fifth feature of the present invention, because the lubrication oil circulating between the portion to be lubricated in the engine and the oil tank is constantly supplied to the circulation circuit of the torque converter, thereby promoting the cooling of the circulating oil in the circulation circuit to prevent the degradation of the circulating oil. Also, any additional oil tank or oil pump for supplying the oil to the circulation circuit is not particularly needed, thereby avoiding the increase in the size and complexity in the structure of the outboard engine system.
According to a sixth feature of the present invention, in addition to the fifth feature, an oil filter is disposed in the first oil supply passage; the second oil supply passage is branched from the first oil supply passage at a portion upstream of the oil filter; and an oil relief passage is provided in the first oil supply passage at a portion upstream of the oil filter, the oil relief passage including a pressure relief valve which opens when a pressure of the first oil supply passage is a predetermined value or more.
With the sixth feature of the present invention, the pressure of the first oil supply passage is regulated by a single pressure relief valve, which in turn regulates the pressure of the second oil supply passage. Therefore, the pressure of the circulation circuit in the torque converter is regulated, and the transmission characteristics are stabilized.
According to a seventh feature of the present invention, in addition to the sixth feature, a downstream end of the oil relief passage is connected to an oil suction passage provided between the oil tank and the oil pump.
With the seventh feature of the present invention, the oil relieved from the oil relief passage is smoothly returned to the oil pump, thereby simplifying the oil pressure circuit.
According to an eighth feature of the present invention, there is provided an outboard engine system comprising: a casing; an engine including a crankshaft and mounted in an upper part of the casing; a torque converter; an output shaft connected to the crankshaft through the torque converter; and a propeller shaft arranged below the output shaft to be driven by the output shaft; the torque converter, the output shaft and the propeller shaft being disposed in the casing; an oil tank disposed in the casing; a first oil pump for drawing up a stored oil in the oil tank; a first oil supply passage for guiding the oil discharged from the first oil pump to a portion to be lubricated in the engine; and a first oil return passage for returning the oil from the portion to be lubricated to the oil tank, wherein the outboard engine system further comprises: a second oil pump for drawing up the stored oil in the oil tank; a second oil supply passage for guiding the oil discharged from the second oil pump to a circulation circuit in the torque converter; and a second oil return passage for returning the oil from the circulation circuit to the oil tank.
With the eighth feature of the present invention, because the lubrication oil circulating between the portion to be lubricated in the engine and the oil tank is supplied to the circulation circuit in the torque converter as an working oil, the oil also circulates between the circulation circuit and the oil pump, thereby promoting the cooling of the circulating oil in the circulation circuit to prevent the degradation of the oil. Also, any additional oil tank or oil pump for supplying the oil to the circulation circuit is not particularly needed, thereby avoiding the increase in the size and complexity in the structure of the outboard engine system. Further, because first and second oil pumps are separately provided to supply the oil to the portion to be lubricated in the engine and the torque converter, capacity of the first and second oil pumps can be individually set corresponding to the portion to be lubricated and the circulation circuit, thereby easily preventing power loss due to an excess supply of the oil.
The above-mentioned object, other objects, characteristics, and advantages of the present invention will become apparent preferred embodiments, which will be described in detail below by reference to the attached drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing an outboard engine system according to a first embodiment of the present invention.
FIG. 2 is an enlarged sectional view showing the portion 2 of FIG. 1.
FIG. 3 is an enlarged view showing the essential portions of FIG. 2.
FIG. 4 is an enlarged sectional view showing the portion 4 of FIG. 1.
FIG. 5 is a view showing a hydraulic circuit including an oil pump.
FIG. 6 is a view corresponding to FIG. 1, but showing a second embodiment of the present invention.
FIG. 7 is an enlarged sectional view showing the portion 7 of FIG. 6.
FIG. 8 is an enlarged view showing the essential portions of FIG. 7.
FIG. 9 is a view corresponding to FIG. 5, but showing the second embodiment.



DESCRIPTION OF THE PREFERRED EMBODIMENTS
A first embodiment of the present invention will be described with reference to FIGS. 1 to 6. In FIG. 1, an outboard engine system O includes a casing 1 which has a water-cooled multi-cylinder four-stroke engine E mounted in its upper portion, and supports a propeller shaft 3 at its lower portion. The propeller shaft 3 has a propeller 2 provided at its rear end. A vertically-extending swivel shaft 6 is mounted to the casing 1 via an upper arm 4 and a lower arm 5 so as to situate in front of the casing 1. The swivel shaft 6 is rotatably supported by a swivel case 7 which is coupled to a stern bracket 8 via a horizontally-extending tilt shaft 9. The stern bracket 8 is cramped to a transom Bt of a body of a ship. Therefore, the casing 1 is horizontally rotatable around the swivel shaft 6, and vertically tiltable around the tilt shaft 9. The reference numeral Ef denotes a removable engine hood for covering the engine E.
In FIG. 2, FIG. 3 and FIG. 4, the above casing 1 includes the extension case 10, the mount case 11 bolt-coupled to an upper end of the extension case 10, and a gear case 12 bolt-coupled to a lower end of the extension case 10. The extension case 10 includes an upper case 10a and a lower case 10b bolt-coupled to the upper case 10a. The mount case 11 is jointed to an upper end surface of the upper case 10a by a plurality of bolts 163.
The casing 1 further includes annular lower distance members 13, an bearing bracket 14, and annular upper distance members 15, which are sequentially superimposed on the upper end of the mount case 11. The engine E is mounted to the upper distance member 15 with the crankshaft 17 being vertically arranged and the cylinder block 18 facing rearward. The bearing bracket 14 and upper distance member 15 are secured to the cylinder block 18 and a bottom wall of the crankcase 19 of the engine E by a plurality of bolts 161. The lower distance member 13, the bearing bracket 14, and the upper distance member 15 are secured to one another by a plurality of bolts 162.
In FIG. 2 and FIG. 3, the torque converter T is vertically arranged in the annular upper distance member 15, and the output shaft 20 coupled to the crankshaft 17 via the torque converter T is vertically arranged in the extension case 10.
The gear case 12 horizontally supports the propeller shaft 3 having the propeller 2 at its rear end, and houses a forward-reverse shifting gear mechanism 21 connecting the propeller shaft 3 to the output shaft 20.
In operation of the engine E, the power thereof is transmitted from the crankshaft 17 to the output shaft 20 via the torque converter T, and further to the propeller shaft 3 via the forward-reverse shifting gear mechanism 21, thereby driving the propeller 2. The rotational direction of the propeller 2 is controlled and switched by the forward-reverse shifting gear mechanism 21.
In the extension case 10, an oil tank 22 open to the mount case 11 is integrally formed with the upper case 10a of the extension case 10. The oil tank 22 stores oil 23 which is used in both lubrication of the engine E and operation of the torque converter T. A downstream end 90 of an exhaust gas passage of the engine E is integrally formed with the upper case 10a. 
As clearly shown in FIG. 3, the torque converter T includes a pump impeller 25, a turbine runner 26 arranged above the pump impeller 25 and opposed to the pump impeller 25, a stator 27 arranged between the inner peripheral portions of the pump impeller 25 and the turbine runner 26, and a circulation circuit 28 of working oil which is defined between these three impellers 25 to 27. The three impellers 25 to 27 are arranged to have a common vertical axis, as in the case of the crankshaft 17 and the output shaft 20.
The pump impeller 25 integrally includes a transmission cover 29 for covering an upper surface of the turbine runner 3. A ring gear 30 for starting operation is secured to an outer peripheral surface of the transmission cover 29. A drive plate 31 is secured to the ring gear 30 by a bolt 322. The drive plate 31 is also secured to a lower end surface of the crankshaft 17 by a bolt 321. The torque converter T is suspended from the crankshaft 17 via the drive plate 31.
A cup-shaped supporting cylinder 34 is secured to a central part of the transmission cover 29. The supporting cylinder 34 is fitted into a supporting hole 33 which is open to the central part of the lower end surface of the crankshaft 17. The output shaft 20 has an upper end which extends to the inside of the supporting cylinder 34 and is supported in the supporting cylinder 34 via a bearing bush 35. A hub of the turbine runner 26 is spline-coupled to the output shaft 20. A hollow stator shaft 37 is arranged around the outer periphery of the output shaft 20 so as to be supported by the output shaft 20 via a needle bearing 36. A known free wheel 38 is interposed between the stator shaft 37 and a hub of the stator 27.
A hollow pump shaft 39 is arranged at the outer periphery of the stator shaft 37. The hollow pump shaft 39 is integrally coupled to the pump impeller 25 and extends downward. The pump shaft 39 is supported by the bearing bracket 14 via an upper ball bearing 43 on the side of the outer periphery. An oil pump 41 driven at the lower end portion of the pump shaft 39 is attached to a pump housing 40 formed at a lower surface of the bearing bracket 14. A pump cover 42 covering a lower surface of the oil pump 41 is bolt-coupled to a lower surface of the bearing bracket 14. An oil seal 45 is attached to an upper end portion of the bearing bracket 14 such that its lip is in close contact with an outer peripheral surface of the pump shaft 39 at a position immediately above the ball bearing 43.
The stator shaft 37 has a large diameter portion 37a at its lower end. A flange 37b is integrally formed on an outer periphery of the large diameter portion 37a. The flange 37b is secured to the pump cover 42 by a bolt 46. A lower ball bearing 44 is mounted to its inner periphery of the flange 37b so as to support the output shaft 20.
Therefore, the pump shaft 39 is supported by the bearing bracket 14 via the upper ball bearing 43, and the output shaft 20 is supported by the large diameter portion 37a of the stator shaft 37 via the lower ball bearing 44, thereby reasonably supporting the pump shaft 39, the stator shaft 37, and the output shaft 20 and downsizing the vertical fluid power transmission including the torque converter T and output shaft 20.
Because the oil pump 41 is mounted to the bearing bracket 14 in a space between the upper and lower ball bearings 43 and 44, thereby downsizing the vertical fluid power transmission having the oil pump 41.
A thrust needle bearing 47 is interposed between the pump impeller 25 and the hub of the stator 27. A thrust needle bearing 48 is interposed between the hub of the turbine runner 26 and the transmission cover 29.
The oil pump 41 draws up the oil stored in the oil tank 22, and supplies the oil to the engine E and the torque converter T. The route of the oil discharged by the oil pump 41 will be described below with reference to FIG. 5.
The oil pump 41 draws up the oil 23 stored in the oil tank 22 via an oil suction passage 50, and discharges the oil 23 to a first oil supply passage 51. The oil discharged to first oil supply passage 51 is filtered by an oil filter 53 provided in the middle of the first oil supply passage 51, and supplied to a lubricated portion of the engine E. After the lubrication, the oil flows downward to the bottom portion of the crankcase 19 of the engine E, and returns to the oil tank 22 via the first oil return passage 59.
The oil discharged to the first oil supply passage 51 is also supplied to a circulation circuit 28 of the torque converter T via a second oil supply passage 52 which is a branch from the first oil supply passage 51 upstream of the oil filter 53. After being used in the circulation circuit 28, the oil is returned to the oil suction passage 50 or the oil tank 22 via a second oil return passage 54.
An oil relief passage 55 is another branch from the first oil supply passage 51 upstream of the oil filter 53, and reaches the oil suction passage 50. The oil relief passage 55 has a pressure relief valve 56 which opens when an oil pressure of the first oil supply passage 51 exceeds a specified value.
The second oil supply passage 52 has an orifice 57 for controlling the amount of the oil supplied to the circulation circuit 28 of the torque converter T. The second oil return passage 54 also has a normally-closed pressure response valve 58 which opens when an oil pressure upstream of the second oil return passage 54 exceeds a predetermined value.
Thus, when the pressure of the first oil supply passage 51 is regulated by the single pressure relief valve 56, the pressure of the second oil supply passage 52 is concurrently regulated, whereby the pressure of the circulation circuit 28 in the torque converter T is regulated, and the transmission characteristics of the torque converter T can be stabilized. In addition, the downstream end of the oil relief passage 55 is connected to the oil suction passage 50, whereby the oil released from the oil relief passage 55 is smoothly returned to the oil pump 41, thereby simplifying the oil pressure circuit.
Again, in FIG. 2 and FIG. 3, the oil suction passage 50 is suspended from the bearing bracket 14, and includes a suction tube 50a having a lower end portion extending into the oil tank 22, and a lateral oil passage 50b which is provided in the bearing bracket 14 so as to communicate the upper end portion of the suction tube 50a with a suction port 41a of the oil pump 41.
The second oil supply passage 52 includes a bottomed vertical hole 52b which is provided at a central portion of the output shaft 20 so as to open in the upper end surface of the output shaft 20, an inlet oil passage 52a which is provided to pass through the fitted portions between the pump cover 42, the stator shaft 37 and the output shaft 20 so as to communicate a discharge port 41b of the oil pump 41 with the lower portion of the vertical hole 52b, and a horizontal hole 52c which is provided at an upper part of the vertical hole 52b so as to pass through the peripheral portion of the thrust needle bearing 48 into the transmission cover 29.
The second oil return passage 54 includes a cylindrical oil passage 54a which is defined between the output shaft 20 and the stator shaft 37 and is in communication with the circulation circuit 28 through the peripheral portion of the thrust needle bearing 47 above the hub of the pump impeller 25, and a lateral outlet oil passage 54b which is provided at the pump cover 42 to communicate with the lower end portion of the cylindrical oil passage 54a. The outlet oil passage 54b is in communication with the lateral oil passage 50b via the pressure response valve 58.
The pressure response valve 58 includes a cylindrical valve chamber 60 horizontally provided in the pump cover 42, and a piston-type valve body 61 slidably fitted in the valve chamber 60. The outlet oil passage 54b is open to the inner end surface of the valve chamber 60. A valve hole 62 is open in the inner side surface of the valve chamber 60 so as to communicate with the lateral oil passage 50b or the oil tank 22. The valve body 61 is arranged so that its top surface, that is, pressure receiving surface is directed toward the outlet oil passage 54b. The valve hole 62 is closed when the valve body 61 is advanced toward the outlet oil passage 54b, and is opened when the valve body 61 is retracted. A valve spring 63 is arranged between the rear surface of the valve body 61 and the screw plug 64 screwed into the opening of the valve chamber 60 so as to urge the valve body 61 to the advancing direction, that is, to the valve closing direction. Therefore, the valve body 61 is normally held at its closed position by a set load of the valve spring 63 to thereby block the second oil return passage 54. When an oil pressure is generated upstream of the second oil return passage 54 and exceeds a predetermined value, the top surface of the valve body 61 receives the oil pressure, and the valve body 61 is caused to retract against the set load of the valve spring 63 to be opened, whereby the second oil return passage 54 enters a communicated state.
An opening 66 (see FIG. 2) is provided in a bottom wall of the crankcase 19 of the engine E. The oil having completed the lubrication of the engine E is discharged through the opening 66. The opening 66 is opened in the upper surface of the mount case 11 through a series of vertical through holes 67 which are formed in the upper distance member 15 and the peripheral portion of the bearing bracket 14, and through the inner side portion of the annular lower distance member 13. The mount case 11 has an opening 68 which is open to the oil tank 22. Therefore, the oil which flows into the bottom portion of the crankcase 19 after completing the lubrication of the engine E is directed to return to the oil tank 22 via the opening 66, through holes 67 and the opening 68. The opening 66, the through holes 67, and the opening 68 form the first oil return passage 59.
In FIG. 3, a first seal member 701 is attached to the outer periphery of the stator shaft 37 so as to closely contacts the inner peripheral surface of the pump shaft 39 in a relatively rotatable manner, thereby preventing the oil in the torque converter T from flowing downward of the pump shaft 39.
A second seal member 702 is provided between the stator shaft 37 and the pump cover 42 at a position below the inlet oil passage 52a, thereby preventing the oil in the inlet oil passage 52a from flowing downward of the stator shaft 37 and the pump cover 42.
Third and fourth seal members 703 and 704 are provided around the outer periphery of the output shaft 20 in the fitted portions of the output shaft 20 and the stator shaft 37 such that they are arranged in the vertical direction to closely contact from above and below the inner peripheral surface of the stator shaft 37 in a relatively rotatable manner. The third and fourth seal members 703 and 704 cooperate to prevent the oil in the inlet oil passage 52a from flowing out of the fitted portions of the output shaft 20 and the stator shaft 37. Further, the upper seal member 703 prevents the oil in the inlet oil passage 54a from flowing downward to the fitted portions of the output shaft 20 and the stator shaft 37.
As shown in FIG. 3 and FIG. 4, the output shaft 20 is divided into an upper output shaft 20a having the vertical hole 52b and supported by the lower ball bearing 44, and a lower output shaft 20b coupled to the forward-reverse shifting gear mechanism 21 (see FIG. 1). An upper end portion of the lower output shaft 20b is supported via a bush 72 in a supporting sleeve 71 which is integrally formed with the outer side of the oil tank 22. The upper output shaft 20a has a flange 73 which abuts on the upper end surface of the inner lace of the ball bearing 44 attached to the inner periphery of the large diameter portion 37a of the stator shaft 37. A stopper collar 74 is locked to the inner peripheral surface of the large diameter portion 37a so as to support the lower end surface of an outer lace of the ball bearing 44. Therefore, unless the stopper collar 74 is removed, the upper output shaft 20a cannot be pulled out downward from the central portion of the torque converter T.
Besides the vertical hole 52b, the upper output shaft 20a has a plug hole 76 connected to the lower end of the vertical hole 52b, and a spline hole 77 connected to the lower end of the plug hole 76 and open in the lower end surface of the upper output shaft 20a. A plug 78 is screwed into the plug hole 76 to form the bottom wall of the vertical hole 52b. The plug 78 has a part of the inlet oil passage 52a, and the orifice 57 for communicating the inlet oil passage 52a with the vertical hole 52b. A fifth seal member 705 is attached to the plug 78 to closely contact the inner peripheral surface of the plug hole 76.
The inlet oil passage 52a may be formed to bypass the plug 78.
A spline shaft 80 is formed at the upper end portion of the lower output shaft 20b. The spline shaft 80 is fitted into the spline hole 77 to couples the upper and lower output shafts 20a and 20b to each other.
Now, operation of the first embodiment will be described below.
In operation of the engine E, the oil pump 41 is driven by the pump shaft 39 to draw up the oil 23 in the oil tank 22 through the oil suction passage 50, that is, through the suction tube 50a and the lateral oil passage 50b, and discharges the drawn-up oil 23 to the first oil supply passage 51 and the second oil supply passage 52. The oil discharged to the first oil supply passage 51 is supplied to the lubricated portion of the engine E, as described above.
Meanwhile, the oil supplied to the second oil supply passage 52 sequentially passes through the inlet oil passage 52a and the orifice 57; ascend through the vertical hole 52b of the upper output shaft 20a to go out of the horizontal hole 52c; enters the transmission cover 29 while lubricating the thrust needle bearing 48; and then flows into the circulation circuit 28 from the outer peripheral side of the turbine runner 26.
The oil in the circulation circuit 28 circulates as shown by an arrow in FIG. 3 with the rotation of the pump impeller 25 to transmit the rotational torque of the pump impeller 25 to the turbine runner 26, thereby driving the output shaft 20. At this time, if the torque is amplified between the pump impeller 25 and the turbine runner 26, the reaction force due to the amplification is borne by the stator 27, which is fixed there by the locking operation of the free wheel 38. Such a torque amplifying effect of the torque converter T strongly drives the propeller 2, thereby effectively improving start and acceleration of a ship.
After the amplification, the stator 27 rotates in the same direction together with the pump impeller 25 and the turbine runner 26 due to the reversal in direction of the torque which the stator 27 receives, while causing the freewheel 38 to run idle.
After being used at the circulation circuit 28, the oil runs down the cylindrical oil passage 54a while lubricating the thrust needle bearing 47 above the hub of the pump impeller 25, and enters the valve chamber of the pressure response valve 58 from the outlet oil passage 54b. 
The oil having entered the valve chamber 60 exerts a pressure to press the valve body 61 of the pressure response valve 58 against the set load of the valve spring 63, whereby the valve body 61 is opened to open the valve hole 62, so that the oil returns from the valve chamber 60 through the valve hole 62 into the oil suction passage 50 or the oil tank 22. In this way, the oil circulates between the circulation circuit 28 of the torque converter T and the oil tank 22 arranged below the torque converter T through the second oil supply passage 52 and the second oil return passage 54. Therefore, it is possible to downsize the torque converter T, and promote the cooling of the circulating oil to prevent degradation of the oil.
In particular, since the oil tank 22 arranged below the torque converter T is separated from the engine E, the oil tank 22 is not much heated by the engine E, the oil tank 22 can have a relatively large capacity without any interference by the engine E and the torque converter T, and thus can increase the amount of oil flowing into the circulation circuit 28, thereby further promoting the cooling of the circulating oil. Further, the engine E, the torque converter T, and the oil tank 22 are sequentially arranged from top to bottom, and the torque converter T can be downsized without any interference by the oil tank 22, thereby reducing the size and weight of the outboard engine system O including these components.
The oil discharged from the oil pump 41 for lubricating the engine E is also supplied to the circulation circuit 28, which eliminates any addition/expansion of the oil tank 22 and the oil pump 41 for supplying the oil to the circulation circuit 28, thereby avoiding an increase of size and a complication of the outboard engine system O.
The elongated output shaft 20 is divided into two portions, that is, the upper output shaft 20a and lower output shaft 20b which are retractably spline-connected to each other. The upper output shaft 20a is coupled to the stator shaft 37 in the axial direction via the lower ball bearing 44 and the stopper collar 74. Therefore, the torque converter T, the bearing bracket 14, the pump cover 42, and the upper output shaft 20a are compactly incorporated into a single unit as a vertical power transmission without any interference by the lower output shaft 20b, thereby facilitating assemblability of the vertical power transmission and mountability of the vertical fluid power transmission to the outboard engine system O.
Further, if the gear case 12 is separated from the extension case 10 for maintenance of the forward-reverse shifting gear mechanism 21 for example, the lower output shaft 20b can be separated downward together with the gear case 12 while the upper output shaft 20a is remained on the torque converter T side by pulling the spline shaft 80 of the lower output shaft 20b out of the spline hole 77 of the upper output shaft 20a. Therefore, it is possible to easily perform the maintenance of the forward-reverse shifting gear mechanism 21, and further avoid disassembly of the vertical fluid power transmission to easily reassemble the gear case 12 into the system.
Furthermore, since the bottom wall of the vertical hole 52 as a part of the second oil supply passage 52b, that is, the plug 78 is screwed into the upper output shaft 20a of the vertical fluid power transmission, the oil is prevented from flowing out of the vertical hole 52b and going downward of the upper output shaft 20a. In this case, although the bottom wall of the vertical hole 52b may be integrally formed with the upper output shaft 20a, the vertical hole 52b, the plug hole 76, and the spline hole 77 are arranged to axially pass through the upper output shaft 20a if the plug 78 is used. Therefore, after processing of these holes, washing can advantageously reliably prevent cut chips from residing in these holes.
The same is true in the case where the engine E and the torque converter T are removed from the mount case 11, which facilitates maintenance of these components.
Moreover, the engine E is mounted to the mount case 11 via the bearing bracket 14 supporting the pump shaft 39 of the torque converter T, the upper distance member 15 connected to the upper end of the bearing bracket 14 to surround the torque converter T, and the lower distance member 13 connected to the lower end of the bearing bracket 14. Therefore, it is possible to easily mount the engine E to the mount case 11 without any interference by the torque converter T, thereby providing an excellent assemblability.
The oil pump 41 is attached to the pump housing 40 formed on the lower surface of the bearing bracket 14 and holds the pump cover 42. Therefore, the bearing bracket 14 supports not only the torque converter T but also the oil pump 41, thereby simplifying the support structure of the oil pump 41.
When the operation of the engine E is terminated, also the operation of the oil pump 41 is terminated, so that in the pressure response valve 58, the pressure of the valve chamber 60 is decreased and the valve body 61 is closed by the set load of the valve spring 63. This causes the outlet oil passage 54b to enter the blocked state, and prevents the oil from flowing from the circulation circuit 28 of the torque converter T into the oil tank 22, thereby keeping the circulation circuit 28 filled with the oil. Therefore, it is possible to enhance the responsiveness of operation of the torque converter T.
Because a part of the second oil supply passage 52 is the vertical hole 52b which is formed at the central portion of the upper output shaft 20a and whose upper end communicates with the circulation circuit 28, the structure of the second oil supply passage 52 can be simplified. Further, when the engine E is not operated, the vertical hole 52b prevents the oil from flowing back from the circulation circuit 28 into the oil pump 41.
Next, a second embodiment of the present invention shown in FIG. 6 to FIG. 9 will be described below. In FIG. 6, a first oil pump 24 is provided in a cylinder head of the engine E, and is driven by a cam shaft 82 for valve operation, the cam shaft 82 being supported by the cylinder head. The first oil pump 24 draws up the oil in the oil tank 22, and supplies the oil to a portion to be lubricated in the engine E. In FIGS. 7 and 8, an oil pump 41 driven at a lower end of a pump shaft 39 serves as the second oil pump 41 for drawing up the oil in the oil tank 22 to supply the oil to the circulation circuit 28 of the torque converter T. The passages of the oil discharged from the first and second oil pumps 24 and 41 will be described below by reference to FIG. 9.
The oil suction passage 50 extending from the single oil tank 22 is divided into first and second branched oil suction passages 50c an 50d, to which the first and second oil pumps 24 and 41 are connected, respectively. The first oil pump 24 draws up the oil from the oil tank 22 through the first branched oil suction passage 50c, and discharges the oil to the first oil supply passage 51. The oil discharged to the first oil supply passage 51 is filtered by an oil filter 53 provided in the middle of the first oil supply passage 51, and is supplied to the portion to be lubricated in the engine E. After lubrication, the oil runs down to the bottom of the crank case 19 of the engine E, and returns to the oil tank 22 through a first oil return passage 59.
Meanwhile, the second oil pump 41 draws up the oil from the common oil tank 22 through the second branched oil suction passage 50d, and discharges the oil to the second oil supply passage 52. Then, the oil is supplied to the circulation circuit 28 of the torque converter T as an working oil. After being used in the circulation circuit 28, the oil returns to the oil suction passage 50 or the oil tank 22 through the second oil return passage 54. Because the second oil supply passage 52 is used exclusively for supplying the oil to the torque converter T, the orifice 57 in the first embodiment is not required to be formed.
An oil relief passage 55 branches from the first oil supply passage 51 upstream of the oil filter 53, and leads to the oil suction passage 50. A pressure relief valve 56 is provided in the oil relief passage 55, and opens when the oil pressure of the first oil supply passage 51 reaches a predetermined value.
A normally-closed pressure response valve 58 is provided in the second oil return passage 54, and opens when the oil pressure upstream of the second oil return passage 54 reaches a predetermined value.
The first and second oil pumps 24 and 41 are designed to individually have capacities corresponding to required characteristics of the circulating section of the engine E and the circulation circuit 28 of the torque converter T. In the example shown in the drawings, the second oil pump 41 is designed to have a volume smaller than that of the first oil pump 24.
Referring again to FIGS. 7 and 8, the oil suction passage 50 comprises a suction tube 50 which is hung on the bearing bracket 14 and has a lower end projecting into the oil tank 22. The first branched oil suction passage 50c compresses a conduit 50c which is connected to the bearing bracket 14 so as to communicate with the oil suction passage 50. The second branched oil suction tube 50d comprises a horizontal oil passage 50d provided at the bearing bracket 14 to communicate the suction conduit 50c with the suction port 41a of the second oil pump 41.
The second oil supply passage 52 comprises: a bottomed central vertical hole 52b so as to open in the upper end surface of the output shaft 20; an inlet oil passage 52a passing through the fitted portions between three components, that is, the pump cover 42, the stator shaft 37, and the output shaft 20 to communicate the discharge port 41b of the second oil pump 41 with the lower portion of the vertical hole 52b; and a horizontal hole 52c provided in the output shaft 20 so as to communicate the upper portion of the vertical hole 52b with the interior of the transmission cover 29 via the periphery of the thrust needle bearing 48.
The second oil return passage 54 is defined between the output shaft 2 and the stator shaft 37, comprising: a cylindrical oil passage 54a communicating with the circulation circuit 28 via the periphery of the thrust needle bearing 47 above an hub of the pump impeller 25; and a horizontal outlet oil passage 54b provided in the pump cover 42 so as to communicate with the lower end portion of the cylindrical oil passage 54a. The outlet oil passage 54b communicates with the horizontal oil passage 50d via the pressure response valve 58.
Because the other components are the same as those of the first embodiment, components in FIG. 6 to FIG. 9 corresponding to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.
As described above, the first oil pump 24 driven by the valve operating cam shaft 82 draws up the oil 23 in the oil tank 22 through the first branched oil suction passage 50c and discharges the oil to the first oil supply passage 51, thereby supplying the oil to the portion to be lubricated in the engine E. After lubrication, the oil runs down to the bottom of the crank case 19 of the engine E, and returns to the oil tank 22 through the first oil return passage 59.
Meanwhile, the second oil pump 41 driven by the pump shaft 39 draws up the oil 23 in the same oil tank 22 through the second branched oil suction passage 50d, and discharges the oil to the second oil supply passage 52 as an working oil. The working oil passes through the inlet oil passage 52a and ascends the vertical hole 52b of the upper output shaft 20a; goes out of the horizontal hole 52c to enter the transmission cover 29 while lubricating the thrust needle bearing 48; and then flows in the circulation circuit 28 from the outer peripheral side of the turbine runner 26.
After being used in the circulation circuit 28 for transmission, the working oil runs down the cylindrical oil passage 54a while lubricating the thrust needle bearing 47 above the hub of the pump impeller 25, and passes through the outlet oil passage 54b to enter the valve chamber 60 of the pressure response valve 58. The pressure of the oil having entered the valve chamber 60 pushes the valve body 61 of the pressure response valve 58 against a set load of the valve spring 63; the valve body 61 is opened to open the valve hole 62; and the oil returns to the oil suction passage 50 or the oil tank 22 from the valve chamber 60 through the valve hole 62.
In this way, the oil circulates between the circulation circuit 28 of the torque converter T and the oil tank 22 arranged below the circulation circuit 28 through the second oil supply passage 52 and the second oil return passage 54. Therefore, it is not required to provide an oil reservoir in the torque converter T, thereby downsizing the torque converter T, and promoting the cooling of the circulating oil in the circulation circuit 28 to prevent the degradation of the oil.
Particularly, the oil tank 22 arranged below the torque converter T further promotes the cooling of the circulating oil, because the oil tank 22 is separated from the engine E and is not heated much by the engine E, and because the oil tank 22 can be designed to have a relatively large capacity without any interference by the engine E and the torque converter T to allow a large amount of oil to flow in the circulation circuit 28. In addition, because the engine, the torque converter and the oil tank are sequentially arranged from top to bottom, and because the torque converter T can be compactly structured without interference by the oil tank 22, the outboard engine system O comprising these components can be downsized.
The oil drawn up from the common oil tank 22 by the first and second pumps 24 and 41 is supplied to the portion to be lubricated in the engine E and the circulation circuit 28 of the torque converter T, respectively. Therefore, any additional oil tank used exclusively for the circulation circuit 28 of the torque converter T is not required, thereby avoiding the increase in the size and complexity in the structure of the outboard engine system. Further, capacity of the first and second oil pumps 21 and 41 can be individually set corresponding to required characteristics of the portion to be lubricated in the engine E and the circulation circuit 28 of the torque converter T, thereby easily preventing power loss due to an excess supply of the oil.
The present invention is not limited to the above described embodiment, and various modifications in design can be made without departing from the subject matter of the present invention. For example, the oil tank 22 may be divided into a section for storing working oil for the torque converter T and a section for storing lubrication oil for the engine E, and oil suitable for each purpose is stored in each section. Further, the power may be input from the engine E through a reduction gear into the torque converter T, and the power may be transferred from the torque converter T through the reduction gear into the output shaft 20.
The first oil pump 24 of the second embodiment may be arranged to be driven by the pump shaft 39 as in the case of the second oil pump 41. Further, the first and the second oil pumps 24 and 41 may be arranged to be driven by other shafts.

## Claims

1. A vertical fluid power transmission comprising:
a crankshaft of an engine, the crankshaft having an axis in a vertical direction;
an output shaft having an axis in a vertical direction;
a torque converter which has an axis in a vertical direction, and is disposed between the crankshaft and the output shaft;
the torque converter including:
a pump impeller connected to the crankshaft;
a turbine runner connected to the output shaft so as to be opposed to the pump impeller;

a stator arranged between the pump impeller and the turbine runner; and
a circulation circuit of a power transmission oil, the circuit being defined between the pump impeller, turbine runner and stator,
wherein an oil supply passage is connected to one end of the circulation circuit, and guides a stored oil that is drawn up from an oil tank and discharged by an oil pump,
wherein an oil return passage is connected to the other one end of the circulation circuit, and leads to the oil tank, and
wherein a normally-closed pressure response valve is provided in the oil return passage, the pressure response valve being opened when an upstream pressure reaches a predetermined value.

2. The vertical fluid power transmission according to claim 1, wherein the oil supply passage is connected to an upper end of the circulation circuit.

3. The vertical fluid power transmission according to claim 2, wherein a part of the oil supply passage comprises a vertical hole which is formed at a central portion of the output shaft and which has an upper end communicating with the circulation circuit.

4. The vertical fluid power transmission according to any of claims 1 to 3, wherein the oil tank is arranged below the torque converter.

5. An outboard engine system comprising:
a casing;
an engine including a crankshaft and mounted in an upper part of the casing;
a torque converter;
an output shaft connected to the crankshaft through the torque converter; and
a propeller shaft arranged below the output shaft to be driven by the output shaft;
the torque converter, the output shaft and the propeller shaft being disposed in the casing;
an oil tank disposed in the casing;
an oil pump for drawing up a stored oil in the oil tank;
a first oil supply passage for guiding the oil discharged from the oil pump to a portion to be lubricated in the engine; and
a first oil return passage for returning the oil from the portion to be lubricated to the oil tank;
a second oil supply passage for guiding the oil discharged from the oil pump directly to a circulation circuit in the torque converter; and
a second oil return passage for returning the oil from the circulation circuit to an intake side of the oil pump or to the oil tank.

6. The outboard engine system according to claim 5, wherein an oil filter is disposed in the first oil supply passage; the second oil supply passage is branched from the first oil supply passage at a portion upstream of the oil filter; and an oil relief passage is provided in the first oil supply passage at a portion upstream of the oil filter, the oil relief passage including a pressure relief valve which opens when a pressure of the first oil supply passage is a predetermined value or more.

7. The outboard engine system according to claim 6, wherein a downstream end of the oil relief passage is connected to an oil suction passage provided between the oil tank and the oil pump.

8. An outboard engine system comprising:
a casing;
an engine including a crankshaft and mounted in an upper part of the casing;
a torque converter;
an output shaft connected to the crankshaft through the torque converter; and
a propeller shaft arranged below the output shaft to be driven by the output shaft;
the torque converter, the output shaft and the propeller shaft being disposed in the casing;
an oil tank disposed in the casing;
a first oil pump for drawing up a stored oil in the oil tank;
a first oil supply passage for guiding the oil discharged from the first oil pump to a portion to be lubricated in the engine; and
a first oil return passage for returning the oil from the portion to be lubricated to the oil tank;
a second oil pump for drawing up the stored oil in the oil tank a second oil supply passage for guiding the oil discharged from the second oil pump directly to a circulation circuit in the torque converter; and
a second oil return passage for returning the oil from the circulation circuit to the oil tank.