JPH0212307B2 - - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (1) Industrial Field of Application The present invention is directed to a hydraulic transmission for a vehicle, particularly a swash plate type hydraulic motor surrounding a swash plate type hydraulic pump. A basically hollow cylindrical support shaft is fixed to the distribution end wall to define an oil chamber between the distribution end wall and the distribution end wall. A fixed shaft having a sliding distribution ring at its tip is inserted, and the fixed shaft connects the oil chamber to an annular low-pressure oil chamber between the fixed shaft and the support shaft;
a high pressure oil chamber between the support shaft and the distribution end wall;
The distribution end wall is configured to transfer hydraulic oil between the hydraulic pump and the hydraulic motor and between the high-pressure oil chamber and the low-pressure oil chamber, and the hydraulic pump and the hydraulic motor form a hydraulic closed circuit. The present invention relates to a connected type transmission.

(2) Prior Art Conventionally, in such hydraulic transmissions, the seal of the low pressure oil chamber was interposed between the inner circumferential surface of the support shaft and the outer circumferential surface of the fixed shaft adjacent to the low pressure oil chamber. This was done using a contact-type elastic sealing member, such as a sealing ring.

(3) Problems to be solved by the invention However, in such a hydraulic transmission, the hydraulic motor produces a pumping action when the vehicle decelerates, and the discharge causes the hydraulic pump to rotate as a motor, resulting in an engine braking effect. However, if such a deceleration effect occurs particularly during high-speed running, high rotational friction and high oil pressure will act on the seal member, which is unfavorable in terms of durability of the seal member.

In order to solve this problem, it is conceivable to provide a non-contact type sealing member between the supporting shaft and the fixed shaft, which has a predetermined distance between it and at least one of them, but in that case, The present inventors have discovered that although there is no problem under normal driving conditions of the vehicle, the following problems peculiar to this type of hydraulic transmission arise especially during deceleration driving. Specifically, when the oil temperature rises and the viscosity of the hydraulic oil decreases, the amount of oil leaking from the above-mentioned gap increases. However, this increase in leaked oil is caused by normal operation of the vehicle when the low-pressure oil chamber is low. Although this is not a problem at times, especially during deceleration operation, a problem arises in that the oil pressure in the low-pressure oil chamber, which should normally be at high pressure, decreases, impairing the engine braking effect.

The present invention has been proposed in view of the above, and an object of the present invention is to provide a hydraulic transmission for a vehicle that can solve all of the above problems.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, according to the present invention, a distribution end wall is provided on the motor cylinder of a swash plate type hydraulic motor surrounding a swash plate type hydraulic pump, A basically hollow cylindrical support shaft that defines an oil chamber between the distribution end wall and the distribution end wall is fixedly installed, and a distribution shaft that slides into the distribution end wall is installed in the support shaft. A fixed shaft having a ring at the tip is inserted, and the fixed shaft divides the oil chamber into an annular low-pressure oil chamber between the fixed shaft and the support shaft, and a high-pressure oil chamber between the support shaft and the distribution end wall. A seal portion is provided between the inner circumferential surface of the support shaft and the outer circumferential surface of the fixed shaft adjacent to the low-pressure oil chamber, and the distribution end wall is arranged between the hydraulic pump and the hydraulic motor. , and a vehicle hydraulic transmission configured to transfer hydraulic oil between the high-pressure oil chamber and the low-pressure oil chamber, and in which the hydraulic pump and the hydraulic motor are connected to form a hydraulic closed circuit, wherein the seal The part is integrally provided on either one of the fixed shaft and the support shaft, and is made of a material having a higher coefficient of thermal expansion than the other, so as to form an annular minute space between the part and the other. configured.

(2) Effect According to the above configuration, since the seal part is held in a non-contact state with respect to the fixed shaft or support shaft that is the mating member, there is no risk of wear and deterioration, and there is no risk of deterioration occurring during deceleration of the vehicle. This makes it possible to make it from a highly rigid material that can withstand the high oil pressure in the low-pressure oil chamber.

Furthermore, according to the thermal expansion of the seal portion, as the oil temperature rises and the viscosity of the hydraulic oil decreases, the minute gap can be made smaller to minimize the amount of hydraulic oil leaking from the gap. Therefore, even when the vehicle is running at deceleration, the oil pressure in the low-pressure oil chamber does not decrease due to the leakage of the hydraulic oil, and therefore, a good engine braking effect can always be obtained.

(3) Embodiments Below, embodiments of the present invention will be explained with reference to the drawings. First, in FIG. 1 showing a first embodiment of the present invention, a hydraulic continuously variable transmission T and a forward and reverse gear device G A vehicle transmission device is constructed, and these T and G are housed in a transmission case 1.

The hydraulic continuously variable transmission T includes a constant displacement swash plate hydraulic pump P and a variable displacement hydraulic motor M.

The hydraulic pump P has a pump cylinder 4 with an input shaft 2 protruding from the left side and a support shaft 3 from the right end. are connected to each other so as to be movable only in the axial direction, and their distal ends penetrate the left side wall of the transmission case 1 and protrude to the outside, where they are connected to a flywheel 6 attached to the engine crankshaft E.

A large number of stepped cylinder holes 7, 7... are bored in the pump cylinder 4 in an annular arrangement surrounding the center of rotation of the cylinder 4, and in the illustrated example, each stepped cylinder hole 7
The left half is a large-diameter hole 7l, the right half is a small-diameter hole 7r, and a pressure-receiving portion is formed in the pressure-receiving surface 8 at a stepped portion thereof. A pair of large and small pump plungers 9l and 9r that face each other slides into each stepped cylinder hole 7 to define a pump oil chamber 7A therebetween. The pump plungers 9l and 9r each have a bottomed cylindrical shape with the bottom facing the outer end, and the large diameter pump plunger 9l
A coil spring 11 that springs both plungers 9l and 9r away from each other is housed in the hollow part, and a spring guide that is inserted into the spring 11 and prevents its buckling is housed in the hollow part of the small-diameter pump plunger 9r. The base of the rod 10 is fitted. The spring guide rod 10
The pump plungers 9l and 9r are made of a material having a lighter specific gravity than the pump plungers 9l and 9r.

On the other hand, the hydraulic motor M surrounds the pump cylinder 4. It has a motor cylinder 12 concentric therewith, in which a number of through cylinder holes 13, 13... are bored in an annular arrangement surrounding the center of rotation of the cylinder 12, and at its right end there is a distribution end wall 12a. are integrally formed. Each hole 13 above
has a pair of motor plungers 14 of the same diameter facing each other.
l and 14r slide together and the motor oil chamber 1 is formed between them.
Define 3A. Furthermore, the left side of the motor cylinder 12,
A hollow output shaft 16 and a basically cylindrical support shaft 17 are fixed to both right end faces by bolts 15, respectively, and the output shaft 16 has a bearing 18 on its outer peripheral surface.
The input shaft 2 is supported on the left end wall of the transmission case 1 via bearings 19 and 20 on its inner peripheral surface. In addition, the support shaft 17 connects the outer peripheral surface of the transmission case 1 to the transmission case 1 via the bear link 21.
is supported on the right end wall of the The motor cylinder 12 supports the support shaft 3 of the pump cylinder 4 via a bearing 22 inside thereof, and brings the end surface of the support shaft 3 into close contact with the distribution end wall 12a. A seal ring 23 is fitted onto the outer periphery of the end of the support shaft 3 so as to be in contact with the inner peripheral surface of the motor cylinder 12 .

Further, inside the motor cylinder 12, there are a pair of left and right pump ramps arranged symmetrically and in contact with the outer ends of the left pump plunger group 9l and the right pump plunger group 9r at a fixed angle with respect to their respective axes. Plates 24l, 24r are thrust and radial bearings 25l, 26l; 25r, 26
Supported via r. Therefore, each pump swash plate 24
When rotating relative to the motor cylinder 12, the pump plungers 9l and 24r cooperate with the coil spring 11 to give reciprocating motion to each pump plunger group 9l and 9r, thereby repeating suction and discharge strokes.

In addition, in the hydraulic motor M, the left motor plunger 14l group and the right motor plunger r
A pair of left and right motor swash plates 27l and 27r are arranged symmetrically, abutting each outer end of the group. These motor swash plates 27l, 17r are connected to thrust and radial bearings 28l, 29l; 28r, 29
The swash plate frames 31l and 31 are respectively supported via r.
r each integrally has a trunnion shaft (not shown) having an axis perpendicular to the rotational axis of the motor cylinder 12, and these shafts are rotatably supported by the transmission case 1 and connected to an interlocking device (not shown). (not shown). Thus, both motor swash plates 27l, 27r can tilt symmetrically from an upright position perpendicular to each motor plunger group 14l, 14r to the maximum tilted position shown, and the motor cylinder 12 rotates in these tilted positions. At this time, the motor plungers 14l and 14r can be sequentially reciprocated to repeat the expansion and contraction strokes, and the motor plungers 14
The sliding stroke of l and 14r is the motor swash plate 27.
It is determined by the inclination angle of l and 27r.

A hydraulic closed circuit is formed between the hydraulic pump P and the hydraulic motor M as follows. That is, an oil chamber 38 is formed in the support shaft 17 of the motor cylinder 12, and the distribution end wall 12a faces the oil chamber 38.
A large number of connection ports 39 each bored in 2a,
39..., one discharge port 41 and one suction port 42 are open, the open end of the discharge port 41 is on the rotation center line of the motor cylinder 12, and the open ends of the connection ports 39, 39... are on the same line surrounding the discharge port 41. On a circle, and the suction port 42 is connected to the connection port 39
Each is located on the outside of the group. A fixed shaft 44 that is positioned and fixed to the transmission case 1 via a positioning pin 43 projects into the oil chamber 38 from the outer end of the support shaft 17, and a distribution ring 45 is attached to the projecting end with respect to the center of rotation of the motor cylinder 12. Mounted eccentrically by a certain amount. This distribution ring 45 is in sliding contact with the distribution end wall 12a to form an oil chamber 38, an annular high pressure oil chamber 38h between the fixed shaft 44 and the support shaft 17, and an annular high pressure oil chamber 38h between the support shaft 17 and the distribution end wall 12.
The discharge port 41 communicates with a connection port 39 connected to the motor oil chamber 13A in the expansion stroke through the high pressure oil chamber 38h, and the suction The port 42 communicates with a communication port 39 connected to the motor oil chamber 13A in the contraction stroke. On the other hand, on the end surface of the support shaft 3 of the pump cylinder 4 that contacts the distribution end wall 12a, there are many communication ports 47, 47 connected to each pump oil chamber 7A.
... are opened, and among these ports, the one connected to the pump oil chamber 7A in the discharge stroke is the discharge port 41.
Additionally, those connected to the pump oil chamber 7A in the suction stroke are connected to the suction port 42, respectively.

In the above configuration, when the pump cylinder 4 is rotated via the input shaft 2 due to the rotation of the engine crankshaft E, the high pressure oil generated in the pump oil chamber 7A due to the discharge stroke of the pump plungers 9l and 9r is discharged from the discharge port 41. It flows into the high-pressure oil chamber 38h and further through the connection port 39 in communication with the motor oil chamber 13A in the expansion stroke, giving thrust to the opposed plungers 14l and 14r facing the oil chamber.
The hydraulic oil discharged by the motor plungers 14l, 14r in the contraction stroke returns to the pump oil chamber 7A in the suction stroke via the communication port 39 communicating with the low pressure oil chamber 38l and the suction port 42. During this time,
The pump plungers 9l and 9r in the discharge stroke are connected to the motor cylinder 12 via the pump swash plates 24l and 24r.
The reaction torque applied to the motor plungers 14l, 14r during the expansion stroke
The motor cylinder 12 is rotated by the sum of the reaction torque received from the motor cylinder 12, and an output is output from its output shaft 16.

In this case, the gear ratio of the motor cylinder 12 to the pump cylinder 4 is given by the following equation.

Speed ratio = rotation speed of pump cylinder 4 / rotation speed of motor cylinder 12 = 1 + capacity of hydraulic motor M /
Capacity of Hydraulic Pump P As is clear from the above equation, if the capacity of hydraulic motor M is changed from zero to the maximum value, the gear ratio can be changed from 1 to a certain required value, and the capacity of hydraulic motor M is Opposed motor plunger 14l, 1
Since the stroke is determined by the stroke of 4r, the above-mentioned speed change action can be obtained steplessly by tilting both motor swash plates 27l and 27r from the upright position to the maximum oblique angle as described above.

The fixed shaft 44 is formed hollow, and a short-circuit port 51 that can communicate between the high and low pressure oil chambers 38h and 38l is bored in its side wall, and a cylindrical clutch valve 52 is provided to open and close the port 51. It is rotatably fitted into the hollow part of the fixed shaft 44. clutch valve 52
is provided with a control groove 53 on the side wall of the distal end, and a rotating plate 54 connected to a clutch control device (not shown) on the proximal end, and by rotating the rotating plate 54, the control groove 53 is aligned with the shorting port 51. When the shorting port 51 is fully opened, the clutch is in the off state. When the shorting port 51 is fully closed by shifting the control groove 53 from the position of the shorting port 51, the clutch is on (as shown), and when the shorting port 51 is half open. A half-clutch condition is obtained. That is, in the clutch-off state, the hydraulic oil discharged from the discharge port 41 to the high-pressure oil chamber 38h passes through the short-circuit port 51 to the low-pressure oil chamber 38l, and therefore immediately short-circuits to the suction port 42, rendering the hydraulic motor M inoperable. Also, Kuratsuchi
In the on state, the short circuit of the hydraulic oil as described above is prevented, the hydraulic oil circulates from the hydraulic pump P to the motor M, and normal transmission occurs.

A hydraulic servo motor 57 operated by a pilot valve 55 is built into the clutch valve 52, and the tip of the servo piston 58 is connected to the clutch valve 52.
The valve stem 58a is formed into a valve stem 58a having a smaller diameter than the inner diameter of the valve stem 58a, and protrudes into the high pressure oil chamber 38h.A closing valve 59 for the discharge port 41 is swingably attached to the tip of the valve stem 58a. The discharge port 41 can be closed by moving the servo piston 58 to the left to bring the closing valve 59 into close contact with the distribution end wall 12a. This blockage is performed when the motor swash plates 27l and 27r are placed in an upright position and the gear ratio is controlled to 1:1.This causes the pump plungers 9l and 9r to be hydraulically locked and the pump plungers 9l and 9r to be moved from the pump cylinder 4 to the pump plunger 9l and 9r. 9
The motor cylinder 12 can be mechanically driven via the r group and the pump swash plates 24l, 24r, so that the motor plungers 14l, 14r
The thrust applied to the motor swash plates 27l and 27r disappears, and the load on the bearings of each part due to the thrust is removed.

Referring also to FIG. 2, a seal portion 60 is provided on the outer peripheral surface of the fixed shaft 44 adjacent to the low pressure oil chamber 38l in order to seal the low pressure oil chamber 38l. This seal part 60 is formed by fixing a ring-shaped part to the outer circumferential surface of the fixed shaft 44, and the fixing structure may be any of fitting, adhesion, and pressure bonding, or it may be plated. The seal portion 60 may also be formed by thermal spraying. Furthermore, a small annular gap 61 is formed between the outer surface of the seal portion 60 and the inner surface of the support shaft 17.

Incidentally, the amount of fluid leakage Q between two concentrically arranged members is generally given by the following equation.

Q=πdh ³ /12μ・ΔP/l Here, code d is the diameter of the inner member, code h is the distance between the inner and outer members, code ΔP is the pressure difference between the parts to be sealed, and code l is the seal structure. The length of the applied portion, sign μ, is the fluid viscosity.

As is clear from the above equation, when the temperature of the hydraulic oil increases and the viscosity μ decreases, the leakage amount Q increases, and in order to reduce this leakage amount Q, it is necessary to reduce the interval h. desired.

Therefore, according to the present invention, the seal portion 60 is formed of a material having a higher coefficient of thermal expansion than the support shaft 17. Then, when the oil temperature rises, the seal portion 60 expands in the radial direction at a larger rate than the support shaft 17, and the minute gap 61 becomes smaller. This makes it possible to reduce the amount of leakage Q. Note that the minute gap 61
is set depending on the required engine braking effect.

Referring again to FIG. 1, the forward and reverse gear devices G
is a pair of drive gears 79 fixed to the output shaft 16
₁ , 79 ₂ , and a driven gear 80 ₁ that meshes with one driving gear 79 ₂ and a driven gear 80 ₂ that meshes with the other driving gear 79 ₂ via an intermediate gear 81.
It is rotatably provided on a subshaft 78 that is parallel to the output shaft 16 and rotatably supported by the transmission case 1 . Both driven gears 81 ₁ , 81 ₂ integrally have drive clutch gears 82 ₁ , 82 ₂ at opposing portions, and a driven clutch gear 83 fixed to the subshaft 78 between them.
The clutch gear 83 can be selectively connected to the clutch gear 82 ₁ or 82 ₂ via an annular clutch member 84 that is constantly engaged therewith.

Further, the countershaft 78 is provided with a gear (not shown) connected to a differential device (not shown), and the differential device is switched between the forward direction and the reverse direction of the vehicle in accordance with the operation of the clutch member 84. Driven.

Next, the operation of this embodiment will be explained. Since the seal portion 60 does not contact the support shaft 17, even if a deceleration effect occurs when the vehicle is running at high speed, the seal portion 60
Since high rotational friction and high pressure do not act on the 0, durability performance can be improved. Moreover,
Minute gap 61 between seal portion 60 and support shaft 17
is set so as to obtain a sufficient engine braking effect, so that even if it is a non-contact type, sufficient engine braking can be obtained.

Also, assuming that the temperature of the hydraulic oil increases, the minute gap 61 becomes smaller,
Despite the decrease in the viscosity of the hydraulic oil, a sufficient sealing function is obtained, thus preventing a decrease in the engine braking effect.

FIG. 3 shows a second embodiment of the present invention, in which, contrary to the above-mentioned embodiments, the seal portion 6 is made of a material with a larger coefficient of thermal expansion than the fixed shaft 44.
2 is provided on the inner surface of the support shaft 17 with a minute gap 63 formed between it and the outer peripheral surface of the fixed shaft 44 .

4, 5, and 6 show third, fourth, and fifth embodiments of the present invention, respectively. In the third embodiment, the seal portion 64 provided on the fixed shaft 44 has a A plurality of annular grooves 65 are provided, and in the fourth embodiment, a plurality of annular grooves 65 are provided on the inner surface of the support shaft 17 at a portion facing the seal portion 60 provided on the self-determining shaft 44.
In the fifth embodiment, a plurality of annular protrusions 68 are provided on the seal portion 67 provided on the fixed shaft 44, and a plurality of annular protrusions 68 are provided on the inner surface of the support shaft 17 corresponding to the annular protrusions 68. A groove 67 is provided.

In such third to fifth embodiments, the flow resistance of the hydraulic oil becomes large, and the leakage of the hydraulic oil is further reduced.

FIG. 7 shows a sixth embodiment of the present invention, in which a fixed shaft 44 is made of a material having a larger thermal expansion coefficient than that of the supporting shaft 17.
A seal portion 71 protruding outward in the radial direction is integrally provided to form an annular minute gap 70 between the seal portion 70 and the inner surface of the seal portion 7 .

FIG. 8 shows a seventh embodiment of the present invention, in which, in addition to the seal portion 60 similar to the first embodiment,
A bearing 72 is interposed between the support shaft 17 and the fixed shaft 44, and the bearing 72 prevents the support shaft 17 from deflecting.

FIG. 9 shows an eighth embodiment of the present invention, in which a seal portion 73 having a two-layer structure is provided on the outer surface of the fixed shaft 44. As shown in FIG. That is, the seal portion 73 includes an inner ring portion 74 having a larger coefficient of thermal expansion than the support shaft 17;
The support shaft 17 and an outer ring portion 75 having a higher coefficient of thermal expansion than the inner ring portion 74 are integrally joined together, and by adjusting the thickness of the outer ring portion 76, a minute gap between the support shaft 17 and the seal portion 73 is formed. The amount of change in the interval 76 can be adjusted.

C. Effects of the Invention As described above, according to the present invention, the motor cylinder of the swash plate type hydraulic motor surrounding the swash plate type hydraulic pump is provided with a distribution end wall, and the distribution end wall has a gap between the distribution end wall and the distribution end wall. A basically hollow cylindrical support shaft is fixed to define an oil chamber, and a fixed shaft having a distribution ring at its tip that slides in contact with the distribution end wall is inserted into the support shaft to fix the oil chamber. The oil chamber is defined by the shaft into an annular low-pressure oil chamber between the fixed shaft and the support shaft, and a high-pressure oil chamber between the support shaft and the distribution end wall, and the support is adjacent to the low-pressure oil chamber. A sealing portion is provided between the inner circumferential surface of the shaft and the outer circumferential surface of the fixed shaft, and the distributing end wall is configured to prevent operation between the hydraulic pump and the hydraulic motor, and between the high-pressure oil chamber and the low-pressure oil chamber. In a vehicle hydraulic transmission configured to transfer oil and in which the hydraulic pump and the hydraulic motor are connected to form a hydraulic closed circuit, the seal portion is attached to either the fixed shaft or the support shaft. Since it is provided integrally and is configured to form a small annular gap with the other part, the seal part is held in a non-contact state with respect to the fixed shaft or support shaft that is its counterpart member. As a result, there is no risk of wear and deterioration, and the seal part can be made of a highly rigid material that can withstand high oil pressure in the low-pressure oil chamber that occurs when the vehicle is decelerating, thus improving the durability of the seal part. It can greatly contribute to improvement.

In particular, the seal portion provided on one of the fixed shaft and the supporting shaft is made of a material with a higher coefficient of thermal expansion than the other of the fixed shaft and the supporting shaft, so the oil temperature increases and the viscosity of the hydraulic fluid increases. As the pressure decreases, the minute gap can be made smaller to minimize the amount of hydraulic oil leaking from the gap. Therefore, even when the vehicle is decelerating, the low pressure caused by the hydraulic oil leakage can be reduced. A good engine braking effect can always be obtained without causing a drop in the oil pressure in the oil chamber.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a longitudinal sectional side view of a vehicle transmission, FIG. 2 is an enlarged sectional view of the main part of FIG. 1, and FIG.
4, 5, 6, 7, 8 and 9 are the second, third, fourth, fifth,
FIG. 2 is a sectional view corresponding to FIG. 2 of the sixth, seventh and eighth embodiments; 12... Motor cylinder, 12a... Distribution end wall, 17... Support shaft, 38... Oil chamber, 38h... High pressure oil chamber, 38l... Low pressure oil chamber, 44... Fixed shaft,
45...Distribution ring, 60, 62, 64, 67, 7
1, 73... Seal part, 61, 63, 70, 76
...Micrometer, M...Swash plate type hydraulic motor, P...
Swash plate hydraulic pump.

Claims (1)

[Claims] 1. The motor cylinder 12 of the swash plate hydraulic motor M surrounding the swash plate hydraulic pump P is provided with a distribution end wall 12a, and an oil chamber 38 is defined between the distribution end wall 12a and the distribution end wall 12a. A basically hollow cylindrical support shaft 17 is fixed therein, and within the support shaft 17 is a distribution ring 45 that is in sliding contact with the distribution end wall 12a.
A fixed shaft 44 having a tip end thereof is inserted, and the fixed shaft 44 divides the oil chamber 38 into an annular low pressure oil chamber 38l between the fixed shaft 44 and the support shaft 17, and between the support shaft 17 and the distribution end wall 12a. Adjacent to the low pressure oil chamber 38l, seal portions 60, 62, 64, 67,71,7
3, the distribution end wall 12a is configured to transfer hydraulic oil between the hydraulic pump P and the hydraulic motor M, and between the high pressure oil chamber 38h and the low pressure oil chamber 38l, In a vehicle hydraulic transmission in which a hydraulic motor M and a hydraulic motor M are connected to form a hydraulic closed circuit, the seal portions 60, 6
2, 64, 67, 71, 73 are the fixed shafts 44
and the support shaft 17, and are made of a material having a larger coefficient of thermal expansion than the other, and there is an annular minute space 61, 6 between the support shaft 17 and the support shaft 17.
A hydraulic transmission for a vehicle, characterized in that it is configured to form 3, 70, and 76.