JPS6242184B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an automatic transmission in which an overdrive device is arranged between a hydraulic torque converter and an underdrive device.

BACKGROUND OF THE INVENTION Automatic transmissions automatically switch reduction ratios in relation to vehicle speed and engine load. The automatic transmission is
It usually consists of a torque converter and an underdrive device connected to the torque converter to obtain a plurality of reduction ratios of 1 or more, in other words, an underdrive device equipped with a plurality of gears with a reduction ratio of 1 or 1 or more. In recent years, the demand for automatic transmissions that can also provide overdrive (speed-increasing drive) has been increasing from the viewpoint of improving driving feeling, saving fuel, and reducing harmful components in exhaust gas. When an overdrive device is added to an automatic transmission consisting of a torque converter and an underdrive device, the required strength of the gears of the overdrive device and the required capacity of the friction material can be reduced in terms of durability and cost. Advantageously, the overdrive device is arranged between the torque converter and the underdrive device, rather than being connected to the output side of the underdrive device (rearward type),
It is preferable to connect the output side of the overdrive device to the input side of the underdrive device (front-end type) (for example, Japanese Patent Laid-Open No. 52-52067).

U.S. Pat. No. 3,444,761 and the Federal Republic of Germany magazine "Automobiletechnische"
Zeitschrift (September 1975 issue) discloses that multiple transmissions are connected coaxially and an oil pan is omitted at the bottom of a given transmission, but it does not disclose anything about the exhaust passage that allows the oil pan to be omitted. do not have.

Problems to be Solved by the Invention The power on the input side is directly coupled to a reduction ratio of 1 and a reduction ratio of less than 1 to an underdrive device consisting of a planetary gear device equipped with a plurality of gears with a reduction ratio of 1 or more than 1. When configuring an automatic transmission by installing an overdrive device consisting of a planetary gear device that selectively transmits data to the output side with an overdrive ratio of It is necessary to configure the stationary side member of the brake device in the transmission case, which locks one element of each planetary gear device constituting the underdrive device and the overdrive device to the transmission case. must be extended in the axial direction of the planetary gear device, and therefore a transmission completely different from the transmission for automatic transmissions without overdrive must be prepared, and the planetary gear that constitutes the underdrive device must be Regarding the device itself, it is difficult to share parts between the case without an overdrive and the case with a planetary gear device that makes up the overdrive device.
Furthermore, it is often difficult to use common parts for the planetary gear device itself that constitutes the overdrive device in combination with other types of underdrive devices.

In addition, in order to standardize the parts of the underdrive device itself and the overdrive device itself, the planetary gear device constituting the overdrive device is installed in a transmission case separate from the transmission case that houses the planetary gear device constituting the underdrive device. If you try to drively connect both planetary gear units by storing them in a drive case, it is difficult to firmly connect the overdrive case and transmission case, and the oil for lubrication and cooling of the overdrive unit is difficult to connect. It becomes necessary to also attach the oil pan to be accommodated in the overdrive case.

SUMMARY OF THE INVENTION Therefore, the present invention aims to strengthen the connection between an overdrive case that accommodates an overdrive device and a transmission case that accommodates an underdrive device, facilitate alignment of the overdrive device and the underdrive device, and facilitate automatic gear shifting. An oil pan that houses oil for machine control, lubrication, and cooling is installed only in the transmission case.
The oil in the overdrive case is intended to be collected into the oil pan.

Means for Solving the Problems In order to achieve this object, the automatic transmission of the present invention includes a hydraulic torque converter having a pump impeller, a stator, and a turbine runner driven by the crankshaft of an engine; An oil pump having a housing surrounding the periphery, an oil pump body disposed adjacent to the torque converter, and an oil pump cover that partitions a pump chamber together with the oil pump body, and supplying working hydraulic pressure to the oil pump. A direct coupling ratio having a reduction ratio of 1 and an overdrive ratio having a reduction ratio of less than 1 are arranged adjacent to and coaxially with respect to the torque converter and connected to the turbine runner of the torque converter on the input side, and transmitting power on the input side. an overdrive device consisting of a planetary gear device that selectively transmits data to the output side; a lubricating oil that surrounds the elements constituting the overdrive device together with the oil pump cover and communicates with the lower part of the space in which the elements are accommodated; an overdrive case having a discharge passage, the overdrive case being disposed adjacent to the overdrive device and coaxially with the torque converter, and having an input shaft connected to an output side of the overdrive device to output power from the input side to 1. A transmission case that incorporates elements constituting an underdrive device consisting of a planetary gear device that transmits transmission to the output side at multiple reduction ratios as described above, and is connected to the transmission case with a spigot and connects the input shaft of the underdrive device. The overdrive case that supports the overdrive device and partitions the internal space of the overdrive device and the underdrive device, penetrates the oil pump body, the oil pump cover, and the overdrive case to the transmission case. A through bolt connects the oil pump body, the oil pump cover, the overdrive case, and the transmission case, and is located below the underdrive device and communicates with the discharge passage of the overdrive case. It also includes an oil pan for storing oil.

Effect of the Invention In the automatic transmission of the present invention, the power of the crankshaft of the engine is transmitted to the overdrive device via the hydraulic torque converter, and is transmitted to the underdrive device at a reduction ratio selected by the overdrive device, To the output side of the underdrive device,
It is output at a reduction ratio obtained by multiplying the reduction ratio of the overdrive device by the reduction ratio of the underdrive device. The overdrive device is located in a space surrounded by the overdrive case and the oil pump cover,
The lubricating and cooling oil supplied to the overdrive device flows into a discharge passage formed in the overdrive case that communicates with the lower part of the space in which the elements that make up the overdrive device are housed, and flows into the oil pan. Forced to reflux.

Example The present invention will be described with reference to the illustrated embodiments.

FIG. 2 shows an automatic transmission that is commercially available before the application is filed and does not include an overdrive device. The hydraulic torque converter 1 includes a pump impeller 5, a turbine runner 6, and a stator 7. The pump impeller 5 is connected to a crankshaft 8 of an engine (not shown), and the turbine runner 6 is connected to a turbine shaft 9a. There is. The torque converter 1 is
The turbine shaft 9a is circumferentially surrounded by the housing 17a.

Rear of torque converter 1 (hereinafter, the side closer to the engine is referred to as "front", and the side farther from the engine is referred to as "rear")
are partitioned by an oil pump body 20. The oil pump cover 21 is arranged adjacent to the oil pump body 20 and defines a pump chamber of the oil pump 71 together with the oil pump body 20. The oil pump gear 50 of the oil pump 71 is connected to the pump impeller 5. Passage 7 formed in oil pump body 20
2 is connected to the suction port of the oil pump 71, and is also connected to a passage 73 formed at the bottom of the oil pump cover 21.

An underdrive device 3 with three forward speeds and one reverse speed is installed coaxially with the torque converter 1 behind the oil pump 71 and adjacent to the oil pump cover 21 . The turbine shaft 9a serves as an input shaft of the underdrive device 3. The underdrive device 3 has its front section covered by an oil pump cover 21.
and a transmission case 18. Oil pump body 20, oil pump cover 21, and transmission case 18 are connected to each other by a plurality of bolts 22a.

The turbine shaft 9a is connected to a clutch cylinder 65, and a multi-plate clutch 24 is provided between the clutch cylinder 65 and the intermediate shaft 29. The hub 66 is fitted with a clutch cylinder 65, and a multi-plate clutch 25 is provided between the hub 66 and the sun gear shaft 30. sun gear shaft 3
0 and a support 31 fixed to the transmission case 18, a multi-disc brake 26 is provided.
Furthermore, a series connection of a one-way clutch 61 and a multi-disc brake 60 is provided. A sun gear 32 is formed on the sun gear shaft 30. Sun gear 32 meshes with planetary pinions 34 and 37, one planetary pinion 34 meshes with ring gear 35, and the other planetary pinion 37 meshes with ring gear 38. In other words, a two-row planetary gear device including the sun gear 32, the planetary pinion 34, and the ring gear 35, and the sun gear 32, the planetary pinion 37, and the ring gear 38 is configured. ring gear 3
5 is connected to the intermediate shaft 29 via a flange 67. Further, the planetary pinion 34 is rotatably supported on a pinion shaft 69 of the carrier 33, and the planetary pinion 37 is rotatably supported on a pinion shaft 68 of the carrier 36. An output shaft 39 of the underdrive device 3 is connected to a ring gear 38 and a carrier 33. A multi-disc brake 27 and a one-way clutch 28 are provided between the carrier 36 and the transmission case 18.

Below the underdrive device is the oil pan 75a.
covered by. Inside the oil pan 75a, a hydraulic control device 4 is provided which controls the hydraulic pressure supplied to the hydraulic surge (cylinder) of the underdrive device.
a (only a portion is shown) is placed. A passage 76 formed at the lower front end of the transmission case 18 connects the oil passage 73 of the oil pump cover 21 into the oil pan 75a.

In addition to the oil passage 73, the oil pump cover 21 is provided with an oil passage that connects the hydraulic control device 4a and the clutch cylinder 65, and an oil passage that connects the discharge port of the oil pump 71 and the hydraulic control device 4a. ing. Further, the oil pump body 20 and the oil pump cover 21 are formed with an oil passage for supplying oil from the hydraulic control device 4a to the torque converter 1, and an oil passage for returning oil from the torque converter 1 to the hydraulic control device 4a. .

Note that in FIG. 2, level _H1 indicates the height of oil during normal running.

Figure 1 shows overdrive device 2 in an automatic transmission.
An example of the present invention is shown below. Portions corresponding to those in FIG. 2 are indicated by the same reference numerals as in FIG.

The overdrive device 2 includes a sun gear 11 and a planetary pinion 1 in an overdrive case 16.
4, ring gear 15, the planetary pinion 1
A clutch device that accommodates a carrier 10 that supports an overdrive case 16 and engages the sun gear 11 and the carrier 10 to enable integral rotation, and a clutch device that locks the sun gear 11 to an overdrive case 16 and makes it stationary. The overdrive case 16 is connected to the transmission case 18 by a spigot, and the overdrive case 16 is connected to the transmission case 18 together with an oil pump body 20 and an oil pump cover 21 by a through bolt 22. is combined with

The turbine shaft 9 plays the role of an output shaft of the torque converter 1 as well as an input shaft of the overdrive device 2, and is connected to a carrier 10 of a planetary gear device in the overdrive device. The carrier 10 has a pinion shaft 49, and needle bearings 43, 44 are provided in two rows in the axial direction on the outer periphery of the pinion shaft 49. The planetary pinion 14 is connected to these two needle bearings 4.
3 and 44, and is rotatably supported by a pinion shaft 49, and meshes with sun gear 11 and ring gear 15. A thrust washer 5 is provided between the planetary pinion 14 and the carrier 10, respectively.
1,52 are provided. A sun gear shaft 79, on which the sun gear 11 is formed, is connected to the clutch cylinder 63. The hub 64 is spline fitted to the clutch cylinder 63. A multi-plate clutch 12 is provided between the clutch cylinder 63 and the carrier 10, and a sun gear shaft 78 and the carrier 10 are connected to each other.
A one-way clutch 13 is provided between the hub 64 and the overdrive case 16 containing the overdrive device, and a multi-disc brake 19 is provided between the hub 64 and the overdrive case 16 containing the overdrive device. The housing 17 covers the periphery of the torque converter 1 and has an extension portion 77 having an inner surface shaped like a cylindrical side surface. The overdrive case 16 has a cylindrical side surface, and the overdrive case 16 is arranged so that the side surface is fitted into the inner surface of the extension portion 77 . Further, the overdrive case 16 is assembled to the transmission case 18 by a spigot, which facilitates alignment of the overdrive device 2 and the underdrive device 3. A flange 53 connected to the ring gear 15 is spline connected to the input shaft 23 of the underdrive device 3. The input shaft 23 is arranged coaxially with the turbine shaft 9 and is connected to the aforementioned clutch cylinder 65 of the underdrive device 3. The overdrive case 16 has a radially extending portion 105 for supporting the input shaft 23, and this portion 105 partitions the internal space of the overdrive device 2 from the internal space of the underdrive device 3.
A bearing 54 is provided between the turbine shaft 9 and the input shaft 23.
A washer 56 is provided between the carrier 10 and the flange 53. The plurality of through bolts 22 pass through the oil pump body 20 , the oil pump cover 21 , and the overdrive case 16 in this order to attach the transmission case 1 to the transmission case 1 .
8 and connect them to each other in the axial direction.

In such an automatic transmission, the relationship between the shift position and gear position and the operating state of each clutch and brake is shown in the diagram of FIG. In Figure 3, P is the parking range, R is the reverse range, N is the neutral range, D is the drive range, 2 is the second range, L is the low range, 〇 is the engaged state, × is the released state, and RC is the locked state. situation,
OR indicates an overrun state, and * indicates a state where no power is being transmitted. Also
OD means overdrive.

Next, lubrication and cooling of each element constituting the overdrive device 2 and the underdrive device 3 will be explained.

The oil pressurized by the oil pump 71 is adjusted to a predetermined pressure in the hydraulic control device 4. The regulated oil flows through the oil passage 45 of the transmission case 18 and the oil passage 46 of the intermediate shaft 29.
It is supplied to each element of the overdrive device 2 and the underdrive device 3 via the pump to lubricate and cool them. Special oil passages are formed in the overdrive device 2 for lubrication and cooling in the vicinity of the needle bearings 43, 44. That is, a space defined by the input shaft 23 and the turbine shaft 9 forms an oil chamber 55. Oil chamber 5
5 is a hole 42 provided in the side wall of the input shaft 23.
It is connected to the inner hole of the input shaft 23 via. The oil passage 40 extends within the carrier 10 in its radial direction,
It is connected to the oil chamber 55 at one end and is closed off by a plug 58 at the other end. An oil passage 41 extending in the axial direction is provided inside the pinion shaft 49 . The oil passage 41 is connected to the oil passage 40 at one end.
and is closed at the other end by a plug 57. An oil passage 48 is formed in the radial direction approximately at the center of the pinion shaft 49 in the longitudinal direction, and this oil passage 48 is connected to the oil passage 41 at one end and reaches an intermediate point between the needle bearings 43 and 44 at the other end. . Thus needle bearing 4
Elements near 3 and 44 are lubricated and cooled by oil at a predetermined pressure supplied through the hole 42, the oil chamber 55, and the oil passages 40, 41, and 48.

4 is a left side view (torque converter 1 side) of the overdrive case 16, FIG. 5 is a sectional view taken along the - line in FIG. Device 3
side) respectively. In FIGS. 4 and 6, the vertical direction corresponds to the vertical direction, and in FIG. 5, the left end corresponds to the torque converter 1 side, and the right end corresponds to the underdrive device 3 side. 81 is
This is a hole for the bolt 22 to pass through. 82 is
This is a breather passage that connects a breather port (not shown) provided in the underdrive device and a hole in the oil pump body 20. Reference numeral 83 denotes an oil return passage provided below the breather passage 82 in order to prevent oil from leaking from the breather port of the underdrive device 3 via the breather passage 82. The breather passage 82 and the oil return passage 83 are formed in the groove 10 formed in the end surface of the overdrive case 16 on the underdrive device 3 side.
They are connected to each other via 3. In this way, the oil in the breather passage 82 is returned via the oil return passage 83 without leaking from the breather port. 84 is a supply passage for supplying oil from the hydraulic control device 4 to the torque converter 1; 85 is a supply passage for supplying oil from the torque converter 1 to the hydraulic control device 4;
This is a discharge passageway for returning to. 86 and 87 are suction passages that guide oil in the oil pan 75 installed at the lower part of the underdrive device 3 to the oil pump 71; 91 is a suction passage that guides the oil pressurized by the oil pump 71 to the underdrive device 3; This is a discharge passage leading to the hydraulic control device 4 at the bottom of the . The suction passage 87 is connected at the front end to the oil passage 73 of the oil pump cover 21, and at the rear end to the oil passage 76 and an oil passage (not shown) provided through the side wall. In order to be properly connected to the oil passage 73, the suction passage 87 is formed at the lowest end of the overdrive case and has an enlarged portion 92 at the front end. The discharge passage 93 is the suction passage 8
It is formed at the lowest end of the periphery of the overdrive case 16 along with the overdrive case 1.
6 and is connected to the inside of the oil pan 75 at the rear end. At least the lower part of the discharge passage 93 is located below the lowermost rotating element of the overdrive device 2, in this case the clutch cylinder 63. Suction passage 8
7 and the discharge passage 93 are separated by a wall 98. Further, 101 is a passage connecting the hydraulic control device 4 and the multi-disc clutch 12 and guiding the hydraulic pressure, and 102 is a passage connecting the hydraulic control device 4 and the clutch cylinder 65 and guiding the hydraulic pressure. Passage 82, 83, 8
4, 85, 86, 87, 91, and 101 all penetrate in the axial direction around the overdrive case 16.

As can be seen from the left side view and right side view of FIGS. 4 and 6, the angular intervals of the bolt through holes 82 in the circumferential direction of the overdrive case 16 are different, and a plurality of bolts 22 are inserted into the holes 81.
through the oil pump body 20, oil pump cover 21, overdrive case 16,
When the transmission case 18 is assembled, the passages 82 to 87 on both sides of the overdrive case 16 in the axial direction are automatically connected to their corresponding passages.

In order to smoothly return the oil that has finished lubricating and cooling each element of the overdrive device 2 into the oil pan 75 via the discharge passage 93, the oil level at the bottom of the underdrive device is lowered from _H1 to _H2 . It will be done. The level H ₂ is set lower than the discharge passage 93. In order to reduce the oil level to H ₂ and still be able to accommodate the correct amount of oil,
The oil pan 75 is deeper than the oil pan 75a. It is also possible to simply lower the mounting position of the oil pan 75a to the transmission case 18 without changing the oil pan 75a.

Effects of the Invention According to the present invention, the power on the input side is reduced to a reduction ratio of 1
An overdrive device consisting of a planetary gear device that selectively transmits data to the output side with a direct coupling ratio of A transmission is arranged coaxially with these, and connects the input side and output side of the overdrive device to the turbine runner of the hydraulic torque converter and the input shaft of the underdrive device, respectively, and accommodates the underdrive device consisting of a planetary gear device. Since the overdrive case housing the overdrive device is connected to the overdrive case through the spigot, the planetary gear device constituting the underdrive device and the planetary gear device constituting the overdrive device do not interfere with each other. Therefore, the underdrive device can use the planetary gear device used in conventional automatic transmissions without overdrive as is, and can be assembled in the same way as for conventional automatic transmissions. The input shaft of the drive device can be strongly supported, and the planetary gear device that makes up the overdrive device can be designed regardless of the type and structure of the planetary gear device that makes up the underdrive device, so the power transmission capacity is It is possible to provide a common device that can be shared by a plurality of underdrive devices having the same or similar types and structures. In addition, the overdrive device is housed in an overdrive case separate from the transmission case, and the overdrive case is connected to the transmission case housing the underdrive device by a spigot. Even when an overdrive device is added to an automatic transmission that combines a type torque converter and an underdrive device, the transmission case housing the underdrive device must have a length along the axial direction of the underdrive device. There is no need to change the design of the spigot joint with the overdrive case if necessary, and the transmission case of the conventionally manufactured automatic transmission can be used at the end of the hydraulic torque converter side. In the case of an oil pump in which the oil pump body and oil pump cover are engaged at the stepped part and connected with bolts,
When the stepped portion of the transmission case that engages the oil pump body and oil pump cover is used for the spigot connection structure with the overdrive case, the transmission case is connected to an automatic transmission without an overdrive. According to the invention, it is also possible to use the present invention in common with an automatic transmission equipped with an overdrive device. Furthermore, since the underdrive device can be assembled into the transmission case separately from the overdrive device, the underdrive device can be installed in a conventional automatic transmission without an overdrive. The assembly procedure can be performed easily.

Moreover, the oil pump body and the oil pump cover of the oil pump that generates working oil pressure for operating the automatic transmission are arranged to extend between the hydraulic torque converter and the overdrive device, and the through bolts are arranged to extend between the hydraulic torque converter and the overdrive device. The oil pump body, the oil pump cover, and the overdrive case are passed through to reach the transmission case, and the oil pump body, oil pump cover, overdrive case, and transmission case are connected. Compared to connecting the oil pump and overdrive case, and the overdrive case and transmission case using separate bolts, assembly is simpler, and each connection part is connected with an average bonding force, so that partial oil Leakage can be prevented, and the strength of the connection can be ensured by coupling the overdrive case and transmission case with the spigot, and the input shaft of the underdrive device can be supported by the coupling with the spigot and the overdrive case. Accordingly, the concentric arrangement of each planetary gear device of the overdrive device and the underdrive device can be improved. Since the oil pump is installed on the side of the hydraulic torque converter in the overdrive case, it can be driven by being connected to the pump impeller of the hydraulic torque converter in the same way as a conventional automatic transmission without overdrive, resulting in stable driving. In addition, in the automatic transmission of the present invention in which an overdrive device is added to the transmission by using a screw hole provided in the transmission in order to mount the oil pump with a screw in an automatic transmission without an overdrive, It can be a threaded hole for a through bolt that passes through the body, oil pump cover, and overdrive case and is screwed into the transmission case.

Further, in the present invention, the overdrive case that houses the planetary gear device that constitutes the overdrive device is surrounded by the oil pump cover on the front side, and the internal space of the overdrive device is connected to the internal space of the underdrive device on the rear side. Although the overdrive case is partitioned, there is a lubricating oil discharge passage that communicates with the lower part of the space in which the elements of the planetary gear set constituting the overdrive device are housed, and the discharge passage is located below the underdrive device. According to the normal lubrication method, the oil passage is passed from the oil pan below the underdrive device to the axis of the intermediate shaft or input shaft of the underdrive device. The lubricating oil supplied from the oil passage formed at the axis of the overdrive device to lubricate and cool each element of the overdrive device is collected in a discharge passage communicating with the lower part of the space in the overdrive case. Since the oil is returned to the oil pan, there is no need to install an oil pan below the overdrive device in addition to the oil pan placed below the underdrive device. Even if an overdrive is added, the oil pan installed in the transmission case of an automatic transmission without overdrive can be used as is, or by replacing the oil pan with a deeper depth than the oil pan in the transmission case, an overdrive can be added. It is possible to store and distribute lubricating oil as equipment is added.

In summary, in the present invention, an overdrive device consisting of a planetary gear device having a speed reduction ratio of 1 and an overdrive ratio of less than 1 is housed in an overdrive case that encloses an oil pump cover of an oil pump. The overdrive case is arranged coaxially with the hydraulic torque converter, and its output side is connected to the input shaft of an underdrive device consisting of a planetary gear device housed coaxially with the hydraulic torque converter in the transmission case. is connected to the transmission case by a spigot, and is also connected by a through bolt that passes through the oil pump body, oil pump cover, and overdrive case and reaches the transmission case. The purpose is to firmly connect the transmission case and place the overdrive device and underdrive device coaxially with respect to the hydraulic torque converter. The formed lubricating oil discharge passage communicates with the oil pan located below the underdrive device housed in the transmission case, so an overdrive device can be added to a conventional automatic transmission without an overdrive. Even in some cases, lubricating oil for the overdrive device can be stored only in the oil pan provided in the transmission case of the automatic transmission, or if necessary, the oil pan provided in the transmission case can be All you need to do is replace it with a deeper one, and all the equipment that should be housed inside the oil pan can be housed within this oil pan, so there is no need to add a new oil pan to the overdrive case when adding an overdrive device. This makes it possible to standardize parts.

Although the present invention has been described with reference to embodiments, it will be apparent to those skilled in the art that the present invention is not limited thereto and includes embodiments with various modifications.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the automatic transmission of the present invention when an overdrive device is added, and FIG. 2 is a longitudinal sectional view of an automatic transmission that has been commercialized before the application without an overdrive device. FIG. 3 is a diagram showing the relationship between the shift position and gear stage and the operating state of each friction engagement device. FIG. 4 is a left side view of the overdrive case, and FIG. −
A cross-sectional view taken along the line, and FIG. 6 is a right side view of the overdrive case. DESCRIPTION OF SYMBOLS 1... Torque converter, 2... Overdrive device, 3... Underdrive device, 5... Pump impeller, 6... Turbine runner, 7... Stator, 8... Crankshaft, 16... Overdrive case, 17... Housing, 18... Transmission case, 20... Oil pump body, 22... Bolt, 23... Input shaft, 53...
Flange, 63...Clutch cylinder, 71...
Oil pump, 75...oil pan, 93...discharge passage.

Claims (1)

[Claims] 1. A hydraulic torque converter having a pump impeller, a stator, and a turbine runner driven by a crankshaft of an engine, a housing surrounding the torque converter, and a housing disposed adjacent to the torque converter. An oil pump having an oil pump body and an oil pump cover that partitions a pump chamber together with the oil pump body and supplying working hydraulic pressure, the oil pump being arranged adjacent to the oil pump and coaxially with the torque converter. and an overdrive comprising a planetary gear device connected to the turbine runner of the torque converter on the input side and selectively transmitting power on the input side to the output side with a direct coupling ratio of a reduction ratio of 1 and an overdrive ratio of less than 1. A drive device, an overdrive case surrounding the elements constituting the overdrive device together with the oil pump cover and having a lubricating oil discharge passage communicating with the lower part of the space in which the elements are housed, adjacent to the overdrive device Moreover, a planetary gear device is arranged coaxially with the torque converter, and has an input shaft connected to the output side of the overdrive device, and transmits power on the input side to the output side at a plurality of reduction ratios of one or more. an underdrive device consisting of an underdrive device, a transmission case incorporating elements constituting the underdrive device, a transmission case coupled to the transmission case with a spigot to support an input shaft of the underdrive device, and an internal space of the overdrive device. The transmission case is reached by passing through the overdrive case that partitions the internal space of the underdrive device, the oil pump body, the oil pump cover, and the overdrive case, and reaching the oil pump body and the oil pump cover. and a through bolt that connects the overdrive case and the transmission case, and an oil pan that is located below the underdrive device, communicates with the discharge passage of the overdrive case, and stores oil. An automatic transmission featuring: 2 Claims characterized in that the discharge passage of the overdrive case is located below the overdrive case and is formed alongside a suction passage that guides oil from the oil pan to the oil pump. The automatic transmission described in paragraph 1. 3. The automatic transmission according to claim 2, wherein the oil level of the oil contained in the oil pan is set lower than that of the discharge passage of the overdrive case. 4. Claim 3, characterized in that the depth of the oil pan used when the overdrive device is added is deeper than the depth of the oil pan used when the overdrive device is not added. automatic transmission. 5. The installation position of the oil pan on the transmission case when the overdrive device is added is lower than the installation position of the oil pan on the transmission case when the overdrive device is not added. An automatic transmission according to claim 3, characterized in that: