JPH0685961U - Hydrostatic transmission - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a hydrostatic pressure transmission with good starting characteristics, compact size, and simple circuit configuration that facilitates neutral holding control [Configuration] Oblique shaft as a fixed displacement hydraulic motor for hydrostatic pressure transmission -Type hydraulic motor 3 is used, and the replenishment / neutral holding valve 20 provided in the closed hydraulic circuit 18 is provided with a communication hole 28 extending over the forward side line and the return side line of the closed hydraulic circuit.
Then, the check member 30 is pushed by the spring 29 so that the head portion 30a enters into the communication hole and closes each opening thereof, and the rod 31 that extends in the communication hole and loosely fits the head portion 30a of the check member. And a high pressure relief valve 22 with a closed hydraulic circuit.
Is composed of a valve body having two pressure receiving surfaces 33a and 33b for respectively receiving the pressures of the forward side pipe and the return side pipe, and a spring 35 for pushing the valve body 34. [Effect] The starting characteristic is improved. , The whole becomes compact, and the neutral holding state can be easily changed only by changing the length of the rod.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydrostatic pressure transmission applied to a continuously variable transmission device for agricultural machinery and construction machinery.

[0002]

[Prior art]

 Conventionally, a hydrostatic transmission having a configuration in which a variable displacement hydraulic pump and a variable or fixed displacement hydraulic motor are connected by a closed hydraulic circuit or an open hydraulic circuit is known. For example, agricultural machines such as combine harvesters and wheel loaders and construction machinery are known. It is used as a vehicle. The closed hydraulic circuit type has a good braking function by controlling the discharge amount of the hydraulic pump, and the hydrostatic transmission of the closed hydraulic circuit is used for traveling. The general main configuration of a conventional hydrostatic transmission with a closed hydraulic circuit system is as shown in Fig. 1. It consists of a swash plate type reversible discharge type variable displacement hydraulic pump a and a swash plate type fixed displacement hydraulic motor b. They are connected to each other by a closed hydraulic circuit c, and a high pressure relief valve f is provided in each of the forward side conduit d and the return side conduit e of the closed hydraulic circuit c in order to prevent high temperature due to high pressure of hydraulic oil. Checks the discharge oil whose pressure is controlled by the low-pressure relief valve h from the charge pump g in order to replenish minute leaks from devices such as motors. The valve function and the same state as when the hydraulic pump a is in the neutral position are set. The oil is supplied to the closed hydraulic circuit c via a supplementary / neutral holding valve i having a function. The high pressure relief valve f has a structure of a general pilot operated type relief valve, and the replenishment / neutral holding valve i is a forward line d and a return line of a closed hydraulic circuit c as shown in FIG. It is composed of a spool-shaped shuttle member j slidably provided in a passage k connecting the passage e and a spring m for pushing one end of the shuttle member j, and is supplied from a replenishment circuit 1 connected in the middle of the passage k. When the discharge pressure of the supplied charge pump g is higher than the pressures of both the pipe lines d and e of the closed hydraulic circuit c and higher than the converted pressure of the spring m, the shuttle member j moves as shown in FIG. Then, the replenishing circuit 1 is connected to both the pipelines d and e, and the discharge oil of the charge pump g is supplied through the through hole of the shuttle member j. When the return line e becomes low pressure while the hydraulic motor b is rotating at a high speed, the shuttle member j provided in the return line e moves to move the discharge oil of the charge pump g as shown in FIG. Is supplied to the return line e. When the hydraulic pump a of the replenishment / neutral holding valve i is in the neutral position, it has the same function as that of the swash plate of the pump a with a slight tilt angle. Even if there is, the shuttle member j has a function of balancing the pressure in the closed hydraulic circuit c so that the hydraulic motor b does not rotate. This function is performed by the shuttle member j when the state shown in FIG. The forward side conduit d of c is connected to the return side conduit e, and even if a small amount of discharge from the hydraulic pump a occurs, the pressure becomes high via the path k. It is realized by flowing a flow rate to e.

[0003]

[Problems to be solved by the device]

 In the conventional case, a swash plate type fixed displacement hydraulic motor b is used. With the swash plate type, there is friction loss between the piston and the cylinder bore, and between the piston shoe and the slide plate. Performance is poor when the hydraulic motor starts to rotate at low speed due to the instability of the cylinder.Because the output shaft that supports the cylinder block is long, a bearing is required behind the cylinder block, which increases the motor structure and limits the device configuration. There was an inconvenience. Further, it is common to flow oil in the closed hydraulic circuit in the forward and reverse directions, and for that purpose, it is necessary to provide high-pressure relief valves in the forward-side pipeline and the return-side pipeline that constitute the closed hydraulic circuit. Since the circuit configuration is complicated, the neutral holding function of the replenishment / neutral holding valve is performed by the opening of the through hole formed in the shuttle member j, so it is difficult to control the neutral holding when there is a minute discharge from the hydraulic pump. There was a drawback.

An object of the present invention is to provide a hydrostatic transmission having a simple structure without such disadvantages and drawbacks.

[0005]

[Means for Solving the Problems]

 In the present invention, a reversible discharge type variable displacement hydraulic pump and a fixed displacement hydraulic motor are connected by a closed hydraulic circuit, and reciprocating pipelines of the closed hydraulic circuit are replenished with oil from a charge pump and the hydraulic pump is In the hydrostatic pressure transmission equipped with a replenishment / neutral holding valve for holding the neutral position and a high pressure relief valve for eliminating high pressure from these reciprocating pipes to the tank, the fixed displacement hydraulic motor An oblique shaft type hydraulic motor is used as the above, and the replenishment / neutral holding valve is formed across the forward side line and the return side line of the closed hydraulic circuit, and the supply pipe from the charge pump is opened in the middle part. And the check provided on the forward and return conduits that block the openings of the communication hole by the spherical or conical head that is pushed by the spring and enters the communication hole. A member extending in the communication hole and A rod in which the head of the check member is loosely fitted and has a length that can simultaneously open the opening, and the high-pressure relief valve is connected to the forward side conduit and the return side conduit. The valve body, which is slidably provided in the provided connection hole and has two stages of pressure-receiving surfaces in the same direction, which receive the pressures of the forward-side pipeline and the return-side pipeline, respectively, and the respective pressure-receiving surfaces faced each other. The above-mentioned object is achieved by constructing the valve body in the direction with a spring. Further, in a hydrostatic transmission in which the reversible discharge type variable displacement hydraulic pump and the hydraulic motor are housed in a common casing, a diagonal shaft type fixed displacement hydraulic motor is used as the hydraulic motor, and the casing is configured. A reciprocating pipeline of the closed hydraulic circuit is formed inside the lid member, and a projection having a slanted tip is provided on the inner surface of the front lid member to open the end of the reciprocating pipeline from the slanting surface. The above object can also be achieved by mounting the valve plate of the oblique shaft type fixed displacement hydraulic pump on the inclined surface.

[0006]

[Action]

 When the reversible discharge type variable displacement hydraulic pump is driven by an engine or the like, a fixed displacement hydraulic motor connected to it via a closed hydraulic circuit is rotated as in the conventional case. Since the motor is an oblique shaft type, it can be stably started with less friction loss of the motor itself, and the structure is smaller because there is no bearing behind the cylinder block. In addition, the replenishment / neutral holding valve is such that, when oil is replenished from the charge pump to one of the lines of the closed hydraulic circuit, the head of the check member that opens and closes the line slides along the rod, Oil is replenished to the closed hydraulic circuit via the supply pipe from the pump, and when the hydraulic pump does not discharge the flow rate or discharges only a small flow rate, the rod is pushed by the springs of the check members at both ends of the rod and the neutral position is reached. Since the length of the rod is set so as to open both openings of the communication hole at this time, the forward and backward pipes of the closed hydraulic circuit are opened through the open openings. Since the oil in the passage is made to flow through, even if there is a small amount of discharge from the hydraulic pump, no pressure enough to rotate the hydraulic motor is generated, and the rod and check members have a simple structure. Is also easy and cheap. The high-pressure relief valve that prevents high pressure in the closed hydraulic circuit has two pressure receiving surfaces, and the pressures in the forward and return pipelines of the closed hydraulic circuit act on each pressure receiving surface. However, even if the hydraulic motor is rotated in the reverse direction, the pressures of the forward and reverse side pipes acting on each pressure receiving surface only change, so the valve acted by the high pressure generated in one of the pipes. The body can be pushed open and can be relieved to the other line, and one high pressure relief valve can be provided in the connection hole without having to separately provide two high pressure relief valves in the forward line of the reciprocating line. Can be provided to relieve the reversible flow.

Further, the reciprocating pipe line is formed inside a front cover member of a common casing that accommodates the reversible discharge hydraulic pump and the oblique shaft type fixed displacement hydraulic motor, and further, on the inner surface of the front cover member. By providing a projection having a sloped front end to open the end of the reciprocating pipeline from the slope, and mounting the valve plate of the sloped fixed displacement hydraulic pump on the slope, The mounting structure of the fixed displacement hydraulic motor is simplified and its assembly is easy.

[0008]

【Example】

 An embodiment of the present invention will be described with reference to the attached drawings. In FIGS. 4 to 5, reference numeral 1 denotes a swash plate type reversible discharge type variable displacement hydraulic pump, and a casing 2 of the hydraulic pump 1 is provided with a reversible discharge type variable displacement hydraulic pump. An oblique shaft type fixed displacement hydraulic motor 3 is provided. The input shaft 4 of the hydraulic pump 1 is connected to, for example, an engine 5 mounted on a combine, and when a tilt angle of a swash plate 6 of the hydraulic pump 1 is manually changed, the input / output shaft 4 emerges from a cylinder block 7 that rotates together with the input shaft 4. The stroke of the piston 8 is changed so that the end face of the cylinder block 7 is discharged from any one of the cocoon-shaped ports 10 and 11 of the valve plate 9 in which the end face of the cylinder block 7 is slidably contacted and its discharge amount is determined. The head of the piston 14 of the hydraulic motor 3 is attached to a drive plate 13 formed integrally with the end of the output shaft 12 parallel to the input shaft 4, and the piston 14 is inclined with respect to the output shaft 12. The cylinder block 17 is rotatably supported by a valve plate 15 having a spherical surface and a center pin 16 which are provided so as to project from and retract to the cylinder block 17. Although not shown, the valve plate 15 is also provided with a cocoon-shaped port. The output shaft 12 of the hydraulic motor 3 is connected to a wheel traveling shaft 23 of a combine, for example.

As shown in FIG. 6, the respective ports of the hydraulic pump 1 and the hydraulic motor 3 are connected to each other by a closed hydraulic circuit 18, and a gear pump is connected to a reciprocating pipe line constituting the closed hydraulic circuit 18. The replenishment / neutral holding valve 20 for replenishing the oil from the charge pump 19 and holding the neutral position of the hydraulic pump 1, and the high pressure for eliminating the high pressure from the reciprocating pipelines 18a, 18b to the tank 21. The relief valve 22 is provided to configure a hydrostatic transmission.

The closed hydraulic circuit 18 is formed inside the front cover member 2 a that constitutes the casing 2 of the hydraulic pump 1, and the replenishment / neutral holding valve 20 and the high pressure relief valve 22 attached to the circuit 18 are also included in the casing. I attached it to 2. On the inner surface of the front lid member 2a, a projection 38 having a slope 37 formed at its tip is provided, and the end of the reciprocating pipeline of the closed hydraulic circuit 18 is opened at the slope 37, and the slope 37 is provided with a valve plate. 15 was fixed, and the flow rate from the reciprocating pipe was supplied to the oblique shaft type fixed displacement hydraulic motor 3 through the valve plate 15. This structure simplifies the structure and facilitates assembly. The charge pump 19 is provided inside the other back cover member 2b of the casing 2, and the oil discharged from the charge pump 19 is replenished / neutralized by a supply pipe 24 through a port 25 of the front cover member 2a. It is supplied to the holding valve 20. Reference numeral 26 in FIG. 6 is a line filter, and 27 is a low pressure relief valve.

When the oblique shaft type fixed displacement hydraulic motor 3 is used as the hydraulic motor of the hydrostatic transmission, it is possible to dispose the high pressure relief valve 22 there since no bearing is required on the opposite side of the cylinder block 17. As a result, the structure of the transmission becomes compact and friction loss is small, so the starting characteristics are stable and the efficiency during operation is also improved.

As shown in FIG. 7, the replenishment / neutral holding valve 20 is formed so as to straddle the forward hydraulic line 18a and the backward hydraulic line 18b of the closed hydraulic circuit 18, and is connected to the intermediate portion from the charge pump 19. The communication hole 28 in which the supply pipe 24 is opened, and the spherical or conical head portion 30a pushed by the spring 29 enters into the communication hole 28 to close the respective opening portions at both ends of the communication hole 28. A cap-shaped check member 30 provided on the forward side conduit 18a and the return side conduit 18b, and a rod 31 extending in the communication hole 28 and having a head portion 30a of the check member 30 loosely fitted at both ends thereof. It is composed of a rod having a length capable of simultaneously opening the openings. The head portion 30a was manufactured by cutting out from the check member 30 into a spherical shape or a conical shape as shown in FIG. 8 or 10, or by welding a spherical body 32 as shown in FIG.

When the pressures in the forward-side pipeline 18 a and the backward-side pipeline 18 b of the closed hydraulic circuit 18 are substantially equal, the spring 29 pushing each check member 30 causes the rod 31 to move to the neutral position, that is, the supply pipe from the charge pump 19. 24 stops at a position communicating with the forward side conduit 18a and the return side conduit 18b, and as a result, the hydraulic motor 3 is not rotated by the hydraulic oil, and the combine or the like is stopped. Even if some discharge is performed from the hydraulic pump 1, the forward side conduit 18a and the return side conduit 18b communicate with each other through the communication hole 28, and the discharge oil circulates therethrough, so that the hydraulic motor 3 is It will not rotate and the combine etc. will be stopped. Further, when the discharge amount from the hydraulic pump 1 starts to increase, the pressure in the forward side pipeline 18a increases due to the restriction of the flow rate flowing through the communication hole 28, and at the same time, the pressure in the return side pipeline 18b increases in the hydraulic motor 3. Since the pressure becomes low due to suction, the check member 30 and the rod 31 move in the direction of the low-pressure return line 18b, as shown in FIG. 11, and close the opening on the high-pressure side of the communication hole 28. As a result, the oil discharged from the hydraulic pump 1 circulates in the closed hydraulic circuit 18 so as to rotate the hydraulic motor 3. When the discharge amount from the hydraulic motor 1 becomes extremely large and the hydraulic motor 3 is rotating at a high speed, if the pressure in the return line 18b becomes low due to insufficient flow rate, as shown in FIG. The head portion 30a of the check member 30 of the pipe line 18b slides so as to come out of the rod 31, and oil is replenished from the supply pipe 24 to the return pipe line 18b. The setting of the flow rate flowing between the outward side conduit 18a and the return side conduit 18b via the communication hole 28 can be easily changed by changing the length of the rod 31, and if the rod 31 is lengthened, The volume of distribution increases and can be set to a small value by shortening it.

The details of the structure of the high-pressure relief valve 22 are as shown in FIG. 5, and the inside of the connection hole 36 provided by connecting the forward-side pipeline 18a and the return-side pipeline 18b of the closed hydraulic circuit 18 is shown. A valve body 34 having two pressure-receiving surfaces 33a and 33b, which are provided in a slidable state, and which face in the same direction to receive the pressures of the forward-side conduit and the return-side conduit, respectively, and the direction in which the respective pressure-receiving surfaces face The valve body 34 is composed of a spring 35 that pushes the valve body, and the valve body 34 is configured as shown in FIG. 13 even if the pressure in either the forward side pipeline 18a or the return side pipeline 18b exceeds the converted pressure of the spring 35. The spring 35 is bent to open the connection hole 36, and hydraulic oil is flowed from the high-pressure side to the low-pressure side pipe to perform a relief operation. Therefore, even if the tilting direction of the swash plate of the hydraulic pump 1 is changed to change the flow direction in the closed hydraulic circuit 18, the high pressure control of the closed hydraulic circuit 18 can be performed by one high pressure relief valve 22.

It is also possible to use a slant shaft type variable displacement hydraulic motor instead of the slant shaft type fixed displacement hydraulic motor 3, and in this case, the projection 38 of the front cover member 2 a of the casing 2 is deleted, Instead, a known tilting mechanism for tilting the cylinder block 17 with respect to the output shaft 12 is provided. In this case, since the displacement of the hydraulic motor can be changed, the speed ratio with the hydraulic pump 1 can be made large, and the oblique shaft type variable displacement hydraulic motor has better mechanical efficiency than the swash plate type variable displacement hydraulic motor. The tilt angle can be reduced and the speed ratio can be increased compared to the plate-type variable displacement hydraulic motor.

[0016]

[Effect of device]

 As described above, according to the present invention, an oblique shaft type hydraulic motor is used as the hydraulic motor of the hydrostatic transmission, and the replenishment / neutral holding valve is spread over the forward hydraulic line and the return hydraulic line of the closed hydraulic circuit. The high-pressure relief valve of the closed hydraulic circuit is composed of a check member that is loosely fitted to the rod inserted through the communication hole, and has a two-stage pressure receiving surface that receives the pressures of the forward-side pipeline and the backward-side pipeline. Since it is composed of a pressed valve element, the starting characteristics are improved, and because the hydraulic motor is small and only one high pressure relief valve is required, a hydrostatic pressure transmission can be constructed compactly, and the rod length of the replenishment / neutral holding valve is long. The neutral holding state can be easily changed simply by changing the height, which is convenient, and the like. The front cover member of the common casing that houses the hydraulic motor and the slant shaft type fixed displacement hydraulic motor has a closed hydraulic circuit. Forming a return conduit Rutotomoni by forming a projection for mounting the valve plate on its inner surface, an effect such that performed easily assembled structure becomes simple.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a conventional hydrostatic transmission.

FIG. 2 is an explanatory view of an operating state of the replenishment / neutral holding valve of FIG. 1 at neutral holding and a minute discharge of the hydraulic pump.

FIG. 3 is an explanatory diagram of an operating state of the supplementary / neutral holding valve of FIG. 1 when the hydraulic motor is operating at high speed.

FIG. 4 is a cutaway side view of the embodiment of the present invention.

5 is a sectional view taken along the line AA of FIG.

FIG. 6 is a hydraulic circuit diagram of FIG.

7 is an enlarged cross-sectional view of the supplementary / neutral holding valve of FIG.

FIG. 8 is a sectional view of the check member.

FIG. 9 is a sectional view of a modification of the check member.

FIG. 10 is a sectional view of a modification of the check member.

11 is a cross-sectional view of an operating state of the supplementary / neutral holding valve of FIG.

12 is a cross-sectional view of an operating state of the supplementary / neutral holding valve of FIG.

13 is a cross-sectional view of the high pressure relief valve of FIG. 5 in an operating state.

[Explanation of symbols]

1 Reversible Discharge Variable Capacity Hydraulic Pump 2 Casing 3 Fixed Capacity Hydraulic Motor 4 Input Shaft 18 Closed Hydraulic Circuit 18a Forward Line 18b Return Side Hydraulic Line 19 Charge Pump 20 Refill / Neutral Holding Valve 21 Tank 22 High Pressure Relief Valve 24 Supply Piping 28 Communication hole 29 Spring 30 Check member 30a Head 31 Rod 32 Connection hole 33a Pressure receiving surface 33b Pressure receiving surface 34 Valve body 35 Spring

Claims (4)

[Scope of utility model registration request] 1. A reversible discharge type variable displacement hydraulic pump and a hydraulic motor are connected by a closed hydraulic circuit, and reciprocating pipelines of the closed hydraulic circuit are replenished with oil from a charge pump and a neutral position of the hydraulic pump is provided. In a hydrostatic transmission equipped with a replenishment / neutral holding valve for holding a high pressure and a high pressure relief valve for eliminating high pressure from these reciprocating pipelines to a tank, an oblique shaft hydraulic motor is used as the hydraulic motor. Then
The replenishment / neutral holding valve is formed by straddling the forward-side pipeline and the backward-side pipeline of the closed hydraulic circuit, and has a communication hole in which a supply pipe from the charge pump is opened in an intermediate portion, and a spherical shape pushed by a spring Alternatively, a check member provided in the forward-side conduit and the return-side conduit that closes each opening of the communication hole when a conical head enters the communication hole, and a check member extending in the communication hole and both ends. And a rod in which the head of the check member is loosely fitted and having a length that can simultaneously open the opening, and the high-pressure relief valve connects the forward side conduit and the return side conduit. The valve body is provided slidably in the connection hole provided with the two-stage pressure-receiving surfaces facing in the same direction and receives the pressures of the forward-side pipeline and the return-side pipeline, respectively. A hydrostatic transmission characterized by comprising a spring that pushes the valve element in a predetermined direction. 2. The hydrostatic transmission according to claim 1, wherein the oblique shaft hydraulic motor is an oblique shaft variable displacement hydraulic motor or an oblique shaft fixed displacement hydraulic motor. 3. The hydrostatic transmission according to claim 1, wherein a discharge direction and a discharge amount of the reversible discharge type variable displacement hydraulic pump are changed by a manual operation. 4. A hydrostatic transmission in which a reversible discharge type variable displacement hydraulic pump and a hydraulic motor are connected by a closed hydraulic circuit, and the reversible discharge type variable displacement hydraulic pump and the hydraulic motor are housed in a common casing. An oblique shaft type fixed displacement hydraulic motor is used as the hydraulic motor, a reciprocating pipe line of the closed hydraulic circuit is formed inside the front cover member that constitutes the casing, and the tip is formed as an inclined surface on the inner surface of the front cover member. A hydrostatic transmission characterized in that a formed projection is provided to open an end of the reciprocating pipeline from the slope, and a valve plate of the oblique shaft type fixed displacement hydraulic pump is attached to the slope.