JP5070175B2 - Hydraulic circuit of transmission with hydrodynamic torque converter - Google Patents

Description

  The present invention relates to a hydraulic circuit of a transmission with a fluid torque converter used in construction machines and the like.

A construction machine such as a wheel loader is provided with a hydraulic clutch in order to form a shift stage in the transmission (see, for example, Patent Document 1). A clutch actuating valve for turning on / off the pressure oil supply is provided on the upstream side of the hydraulic clutch, and a hydraulic pump is further provided on the upstream side of the clutch, via a pressure oil line from the hydraulic pump. And is supplied to the hydraulic clutch. Further, another pressure oil line branches off from the pressure oil line between the hydraulic pump and the clutch operating valve, and a fluid type torque converter is connected to the branched pressure oil line. The pressure oil supplied to the hydraulic clutch is regulated by providing a relief valve in the middle of the branched pressure oil pipeline.
Japanese Patent Laid-Open No. 60-227056

  However, in the case of the hydraulic circuit as described above, the load pressure of the hydraulic pump is always maintained at a level higher than the clutch operating pressure. The oil supplied to the hydraulic clutch requires high pressure to operate the clutch, while the oil supplied to the fluid torque converter requires a flow rate to circulate inside it, but the high pressure is Not needed. In other words, the load pressure of the hydraulic pump only needs to be high only when the clutch is operated, and otherwise the hydraulic pump is performing useless work. If it does so, the load of the engine which drives a hydraulic pump will always be in a large state, and it is not good for fuel consumption.

  Accordingly, an object of the present invention is to suitably reduce the load of a hydraulic pump in a hydraulic circuit of a transmission to which a fluid type torque converter is connected.

  The present invention has been made in view of the above circumstances, and a hydraulic circuit of a transmission with a fluid torque converter according to the present invention connects a hydraulic clutch to one of two branch circuits branching from a discharge side of a hydraulic pump. A hydraulic torque converter for transmission with a fluid torque converter, wherein a hydraulic torque converter is connected to the other, and a pressure reducing valve for allowing / blocking supply of pressure oil to the hydraulic clutch is provided in the one branch circuit, The one branch circuit is provided with an accumulator on the primary side of the pressure reducing valve and a check valve for preventing a backflow of pressure oil from the accumulator to the other branch circuit. A relief valve device capable of changing a set pressure at least in two steps of high and low on the upstream side of the fluid torque converter, and the relief valve When the pressure accumulated in the accumulator is less than a predetermined value, the set pressure is made higher than the secondary pressure of the pressure reducing valve, and when the pressure is greater than or equal to a predetermined value, the set pressure is It is characterized by being configured to be lower than the secondary side pressure of the pressure reducing valve.

  According to the above configuration, when the pressure accumulated in the accumulator is less than a predetermined value, the set pressure of the relief valve device is made higher than the secondary pressure of the pressure reducing valve (that is, the clutch operating pressure), Sufficient pressure is accumulated in the accumulator. On the other hand, when the pressure accumulated in the accumulator is greater than or equal to a predetermined value, the hydraulic clutch can be operated by the hydraulic pressure accumulated in the accumulator, so the set pressure of the relief valve device is set to the secondary side pressure of the pressure reducing valve. In this case, the oil is led to the fluid type torque converter even when the load pressure of the hydraulic pump is small. Therefore, it is possible to suitably reduce the load on the hydraulic pump when the clutch is not operated.

  The relief valve device may be configured such that the set pressure is substantially the same as the inlet pressure of the fluid torque converter when the pressure accumulated in the accumulator is equal to or greater than a predetermined value.

  According to the said structure, since the pressure loss in a relief valve apparatus is almost lose | eliminated, generation | occurrence | production of the heat resulting from a pressure loss is suppressed, and it becomes possible to miniaturize the oil cooler etc. which cool oil. Note that “substantially the same” refers to the difference between the set pressure of the relief valve device and the inlet pressure of the torque converter due to the pressure loss generated in the flow path forming member between the outlet of the relief valve device and the inlet of the fluid torque converter. It is allowed that a slight difference occurs in

  The relief valve device is biased by a spring in the closing direction and operates in the opening direction using the primary pressure as a pilot pressure, and a state in which pressure oil is applied to resist the opening operation of the relief valve body And a setting pressure switching valve capable of switching between the state in which the pressure oil is unloaded, and the setting pressure switching valve is configured to unload the pressure oil when the pressure accumulated in the accumulator exceeds a predetermined value. It may be.

  According to the above configuration, the set pressure of the relief valve device is set higher than the secondary side pressure of the pressure reducing valve by applying pressure oil to the set pressure switching valve so as to resist the opening operation of the relief valve body. can do. On the other hand, by setting the set pressure switching valve to a state in which the pressure oil is unloaded, the set pressure of the relief valve device can be made lower than the secondary side pressure of the pressure reducing valve.

  Between the relief valve device and the torque converter, there is provided a safety valve in which the inlet pressure of the torque converter is set lower than the secondary side pressure of the pressure reducing valve, and the set pressure switching valve is the accumulator The pressure accumulated in the pilot pressure is used as the pilot pressure, and the relief valve device allows the pilot pressure to be supplied from the accumulator to the set pressure switching valve, and supplies the pilot pressure from the accumulator to the set pressure switching valve. There may be further provided an electromagnetic switching valve capable of switching between the state of shutting off.

  According to the above configuration, the electromagnetic switching valve is switched to a state in which the supply of the pilot pressure from the accumulator to the set pressure switching valve is shut off, thereby preventing the unloading of the pressure oil that resists the opening operation of the relief valve body. can do. As a result, the set pressure of the relief valve device is maintained higher than the secondary side pressure of the pressure reducing valve, and pressure loss occurs in the hydraulic pressure led to the torque converter via the relief valve device. The time required for machine operation can be shortened.

  The electromagnetic switching valve may be configured to be switchable by a user operation.

  According to the said structure, it becomes possible for a user to determine manually whether promotion of warming-up operation using the heat resulting from the pressure loss in a relief valve apparatus is implemented.

  A temperature sensor for detecting an oil temperature of the hydraulic circuit; and a controller for controlling the electromagnetic switching valve based on information from the temperature sensor, wherein the controller has a predetermined oil temperature detected by the temperature sensor. If it is below a value, the structure which controls the said setting pressure switching valve so that it may be in the state which provides the pressure oil which resists the opening operation | movement of the said relief valve main body may be sufficient.

  According to the above configuration, when the oil temperature of the hydraulic circuit decreases, the set pressure of the relief valve device is automatically set so as to be higher than the secondary pressure of the pressure reducing valve. It is possible to automatically promote the warm-up operation using the resulting heat.

  A pressure sensor capable of detecting the pressure accumulated in the accumulator; and a controller for controlling the set pressure switching valve based on information from the pressure sensor, wherein the controller is a pressure detected by the pressure sensor. If the pressure is equal to or greater than a predetermined value, the set pressure switching valve may be controlled so that the pressure oil that resists the opening operation of the relief valve main body is unloaded.

  According to the above configuration, the set pressure of the relief valve device can be easily changed in two steps, high and low, according to the pressure accumulated in the accumulator with a simple configuration using a pressure sensor.

  The relief valve device may be configured such that, when the hydraulic clutch is operated, the set pressure is made higher than the secondary pressure of the pressure reducing valve even if the pressure accumulated in the accumulator is not less than a predetermined value. Good.

  According to the above configuration, by operating the hydraulic clutch, the pressure accumulated in the accumulator does not fluctuate in the vicinity of the predetermined pressure and the set pressure of the relief valve device does not fluctuate. As a result, it is possible to prevent fluctuations in the pressure input to the fluid type torque converter due to fluctuations in the set pressure, reduce the load on the fluid type torque converter and the equipment connected thereto, and reduce the vibration of the equipment.

  The relief valve device can change the set pressure in at least three stages. When the hydraulic clutch is operated, the set pressure when the hydraulic clutch is operated causes the hydraulic clutch to operate. It may be a configuration that provides the necessary clutch actuation pressure.

  According to the above configuration, when the hydraulic clutch is operated, useless power for accumulating the accumulator is not consumed, and the load on the hydraulic pump can be reduced.

  A pressure sensor that detects pressure accumulated in the accumulator; and a controller that controls the relief valve device based on pressure detected by the pressure sensor, wherein the controller detects pressure detected by the pressure sensor. If the pressure is not less than a predetermined value, the set pressure is made lower than the secondary side pressure of the pressure reducing valve, and even if the pressure detected by the pressure sensor is not less than a predetermined value, the hydraulic clutch is operated, The configuration may be such that the relief valve device is controlled so that the pressure detected by the pressure sensor becomes the clutch actuation required pressure.

  According to the above configuration, since feedback control is performed so that the hydraulic pressure supplied to the hydraulic clutch becomes the clutch actuation required pressure, the actual pressure of the pressure oil supplied to the hydraulic clutch can be set to the clutch actuation required pressure. it can. Thereby, useless power consumption can be further suppressed.

  The relief valve device is biased by a spring in the closing direction and operates in the opening direction using the primary pressure as a pilot pressure, and a state in which pressure oil is applied to resist the opening operation of the relief valve body And a set pressure switching valve that can switch between a state in which the pressure oil is unloaded, and a state in which the pressure oil is applied so as to resist the opening operation of the relief valve body from the state in which the hydraulic pressure is unloaded An unload function switching valve that switches to a state in which the pressure oil is unloaded when the pressure accumulated in the accumulator exceeds a predetermined value, and the unload function switching valve When the hydraulic clutch is operated, from the state where the hydraulic pressure is unloaded to the state where pressure oil is applied so as to resist the opening operation of the relief valve body. It may be configured to switch control to.

  According to the above configuration, even if the pressure accumulated in the accumulator is equal to or higher than a predetermined value and the pressure oil applied to the relief valve body is unloaded, the unload function switching valve is unloaded when the hydraulic clutch is operated. The relief valve body is operated in the closing direction by forcibly switching from the loaded state to a state in which pressure oil is applied to the relief valve body. Thereby, regardless of the pressure accumulated in the accumulator, the set pressure becomes higher than the pressure on the secondary side of the pressure reducing valve, and the pressure fluctuation of the fluid torque converter when the hydraulic clutch is operated is prevented.

  The one branch circuit is provided with a plurality of pressure reducing valves in parallel, and each of the plurality of pressure reducing valves is provided with the hydraulic clutch, and at least one of the plurality of hydraulic clutches is The pressure oil to be supplied is discharged through a throttle, and the relief valve device operates the hydraulic clutch for discharging the pressure oil, so that the set pressure is reduced to the secondary pressure of the pressure reducing valve. It may be configured to be higher.

  In the above configuration, by configuring the hydraulic clutch to discharge the pressure oil, a large amount of pressure oil is required in the hydraulic clutch that discharges the pressure oil, and the pressure accumulated in the accumulator fluctuates around a predetermined value and is set The pressure often fluctuates. However, since the set pressure is higher than the secondary side pressure of the pressure reducing valve when the hydraulic clutch is operated, the set value can be prevented from fluctuating. Thereby, the pressure fluctuation of the fluid type torque converter accompanying the fluctuation of the set pressure can be prevented, the load on the fluid type torque converter and the equipment connected thereto can be reduced, and the vibration of the equipment can be reduced.

  As is apparent from the above description, according to the present invention, it is possible to suitably reduce the load on the hydraulic pump other than during clutch operation.

  Embodiments according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a view showing a hydraulic circuit 1 of a transmission with a fluid torque converter according to a first embodiment of the present invention. The hydraulic circuit 1 according to the present embodiment is mounted on a construction machine such as a wheel loader. As shown in FIG. 1, the hydraulic circuit 1 has one trunk circuit 3 connected to the discharge side of a hydraulic pump 2 driven by an engine, and the trunk circuit 3 is provided with a filter 4. A filter safety valve 5 is provided so as to bypass the filter 4. The trunk circuit 3 branches into two branch circuits 6 and 7 on the downstream side. A hydraulic clutch 8 is connected to one branch circuit 6, and a fluid torque converter 9 is connected to the other branch circuit 7.

The hydraulic clutch 8 is for the construction machine transmission to form a total of eight shift speeds of four forward speeds and four reverse speeds. Specifically, the hydraulic clutch 8 includes a forward clutch 8 _F , a reverse clutch 8 _R , a first gear stage forming clutch 8 ₁ , a second gear stage forming clutch 8 ₂ , and a third gear stage forming clutch 8 _3. and a fourth and a gear stage for forming clutch 8 _4. The first gear position forward by the ON the forward clutch 8 _F and the clutch ₈₁ is, second gear position forward by the forward clutch 8 _F and the clutch ₈₂ is turned ON is forward clutch 8 the third gear position forward by the _F clutch 8 ₃ oN is the fourth gear position forward by the oN the forward clutch 8 _F and the clutch 8 ₄ are respectively formed. Further, the reverse first gear position by the ON the reverse clutch 8 _R and the clutch ₈₁ is, the second reverse gear position by the ON the reverse clutch 8 _R and the clutch _82, reverse clutch 8 reverse third gear position by the _R and clutch 8 ₃ to oN is reverse fourth gear position by the oN the reverse clutch 8 _R and the clutch 8 ₄ are respectively formed.

One branch circuit 6 includes an electromagnetic solenoid actuated pressure reducing valve 10 (10 _F , 10 _F , 8 _F , 8 _R , 8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ that allows / blocks the supply of pressure oil to / from each clutch. 10 _R , 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ ) are provided. In the pressure reducing valve 10, the secondary pressure is set to a pressure necessary for the operation of the hydraulic clutch 8 (for example, 2.7 MPa, hereinafter, also simply referred to as “required clutch operation pressure”). One branch circuit 6 is provided with an accumulator 11 on the primary side of the pressure reducing valve 10. The upper limit of accumulator 11 that can store pressure is set to a pressure (for example, 4.9 MPa) higher than the set value of pressure reducing valve 10. Also, one branch circuit 6 is provided with a check valve 12 that prevents the backflow of pressure oil from the accumulator 11 to the other branch circuit 7.

  The other branch circuit 7 is provided with a relief valve device 14 on the upstream side of the fluid torque converter 9. The relief valve device 14 includes a relief valve main body 15 and a set pressure switching valve 16 that can change the set pressure of the relief valve main body 15 in two steps, high and low. The relief valve body 15 is configured to be urged in the closing direction by a spring to operate in the opening direction using the primary side pressure as a pilot pressure, and pressure oil that resists the opening operation can be applied by the set pressure switching valve 16. Has been.

  The set pressure switching valve 16 uses the hydraulic pressure accumulated in the accumulator 11 as a pilot pressure, and applies pressure oil that resists the opening operation of the relief valve body 15 when the pilot pressure is less than a predetermined pressure. For example, when the pilot pressure is lower than the clutch operating pressure, the set pressure switching valve 16 applies pressure oil that resists the opening operation of the relief valve body 15. This pressure oil creates resistance in the opening operation of the relief valve body 15 by forming a closed circuit. That is, when the relief valve main body 15 is opened, the force acts so that the set pressure switching valve 16 maintains the shut-off state of FIG. 1 via the pressure oil. As a result, the set pressure of the relief valve main body 15 is substantially the same as the upper limit of accumulator 11 that can accumulate pressure.

  On the other hand, the set pressure switching valve 16 is in a state where the set pressure switching valve 16 is opened when the pilot pressure reaches the accumulator 11 upper limit of accumulating capacity, and the pressure oil against the opening operation of the relief valve body 15 is unloaded. Switch. Thereby, the set pressure of the relief valve main body 15 becomes substantially the same as the set pressure (for example, 0.9 MPa) of the safety valve 20 that sets the upper limit value of the inlet pressure of the fluid type torque converter 9. The safety valve 20 is provided between the relief valve main body 15 and the fluid torque converter 9, and the inlet pressure of the fluid torque converter 9 is set lower than the secondary pressure of the pressure reducing valve 10.

  The relief valve device 14 can switch between a state in which the supply of pilot pressure from the accumulator 11 to the set pressure switching valve 16 is allowed and a state in which the supply of pilot pressure from the accumulator 11 to the set pressure switching valve 16 is interrupted. The electromagnetic switching valve 17 is further provided. When the electromagnetic switching valve 17 is in the shut-off state, the pilot portion that acts toward the unloading state of the set pressure switching valve 16 is set to a no-load state. Therefore, when the electromagnetic switching valve 17 is in the shut-off state, the set pressure switching valve 16 is held in a state of applying pressure oil that resists the opening operation of the relief valve body 15 by the spring force.

  The electromagnetic switching valve 17 is controlled to be switched by the controller 18. The controller 18 is connected to input means 19 (for example, an operation lever) operated by a user. That is, the controller 18 switches the electromagnetic switching valve 17 according to the operation of the input means by the user. Therefore, the electromagnetic switching valve 17 can be manually switched by a user operation. An oil cooler 22 and a safety valve 21 that sets the outlet pressure of the torque converter 9 are provided on the downstream side of the fluid torque converter 9, and the downstream side of the oil cooler 22 is drained.

  Next, the operation of the hydraulic circuit 1 will be described.

  The electromagnetic switching valve 17 is normally in a state that allows the supply of pilot pressure from the accumulator 11 to the set pressure switching valve 16. In a state where the pressure in the accumulator 11 is smaller than a predetermined value just after the hydraulic clutch 8 is actuated, the set pressure switching valve 16 is in a state of applying pressure oil that resists the opening operation of the relief valve body 15. That is, the set pressure of the relief valve main body 15 is substantially the same as the pressure accumulation upper limit value (for example, 4.9 MPa) of the accumulator 11. Then, the hydraulic pump 2 is operated in a state where the relief valve body 15 is closed, and pressure is accumulated in the accumulator 11.

  When the pressure accumulated in the accumulator 11 reaches the accumulable upper limit value, the set pressure switching valve 16 is switched to a state in which the pressure oil that resists the opening operation of the relief valve body 15 is unloaded. As a result, the set pressure of the relief valve main body 15 is changed to be substantially the same as the set pressure (for example, 0.9 MPa) of the safety valve 20 of the fluid type torque converter 9. Therefore, when the hydraulic pressure generated in the hydraulic pump 2 exceeds the set pressure of the safety valve 20 (that is, the set pressure of the relief valve main body 15), the oil discharged from the hydraulic pump 2 is fluidized torque via the relief valve main body 15. Guided to the converter 9. At this time, since the hydraulic pressure accumulated in the accumulator 11 does not flow back by the check valve 12, the pilot pressure of the set pressure switching valve 16 is maintained at the accumulator 11 capable of accumulating pressure.

  Therefore, the discharge pressure of the hydraulic pump 2 becomes substantially the same as the set pressure of the safety valve 20, and oil is guided to the fluid type torque converter 9 even when the load pressure of the hydraulic pump 2 is small except during the accumulator 11 accumulation. . Therefore, it is possible to reduce the load on the hydraulic pump 2 when the hydraulic clutch 8 is not operated. Further, since the pressure loss between the primary side pressure and the secondary side pressure of the relief valve main body 15 is almost eliminated, the generation of heat due to the pressure loss is suppressed, and the oil cooler 22 for cooling the oil is downsized. You can also.

  Further, when the user operates the input means 19 during the warm-up operation and switches the electromagnetic switching valve 17 to a state in which the supply of the pilot pressure from the accumulator 11 to the set pressure switching valve 16 is cut off, the set pressure switching valve 16 is unloaded. The pilot part acting toward the state becomes a no-load state. As a result, the set pressure switching valve 16 is held in a state of applying pressure oil that resists the opening operation of the relief valve main body 15 by the spring force, and the set pressure of the relief valve main body 15 is substantially equal to the upper limit of accumulator 11 that can accumulate pressure. It is changed to be the same. If it does so, the load of the hydraulic pump 2 will increase, a big pressure loss will arise between the primary side pressure of the relief valve main body 15, and a secondary side pressure, and the heat resulting from it will generate | occur | produce. Therefore, the time required for the warm-up operation is shortened.

(Second Embodiment)
FIG. 2 is a view showing a hydraulic circuit 31 of a transmission with a fluid torque converter according to a second embodiment of the present invention. In addition, about the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 2, the hydraulic circuit 31 of this embodiment includes a temperature sensor 32 that detects the oil temperature on the suction side of the hydraulic pump 2. The temperature sensor 32 is connected to a controller 33 that performs switching control of the electromagnetic switching valve 17.

  If the oil temperature detected by the temperature sensor 32 is equal to or lower than a predetermined value, the controller 33 controls the electromagnetic switching valve 17 so that the supply of the pilot pressure from the accumulator 11 to the set pressure switching valve 16 is cut off. . On the other hand, if the oil temperature detected by the temperature sensor 32 exceeds a predetermined value, the controller 33 controls the electromagnetic switching valve 17 so as to allow the pilot pressure to be supplied from the accumulator 11 to the set pressure switching valve 16. To do.

  With such a configuration, when the oil temperature of the hydraulic circuit 31 decreases, the set pressure of the relief valve body 15 is automatically set so as to be higher than the secondary side pressure of the pressure reducing valve 10. The warm-up operation using the heat caused by the pressure loss in the main body 15 can be automatically promoted.

(Third embodiment)
FIG. 3 is a view showing a hydraulic circuit 41 of a transmission with a fluid torque converter according to a third embodiment of the present invention. In addition, about the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 3, the relief valve device 45 of the present embodiment includes a relief valve main body 15 and a set pressure switching valve 42 composed of an electromagnetic switching valve capable of changing the set pressure of the relief valve main body 15 in two steps, high and low. It has. The set pressure switching valve 42 creates resistance in the opening state of the relief valve main body 15 and the state in which pressure oil that causes resistance to the opening operation of the relief valve main body 15 is applied to the relief valve main body 15 by forming a closed circuit. The pressure oil to be unloaded is configured to be switchable.

One branch circuit 6 is connected to a pressure sensor 43 capable of detecting the pressure of the accumulator 11 (that is, the primary pressure of the pressure reducing valve 10). A controller 44 that controls the set pressure switching valve 42 based on the detected pressure is connected to the pressure sensor 43. When the pressure detected by the pressure sensor 43 is less than a predetermined value (the accumulator 11 is capable of accumulating pressure), the controller 44 causes the set pressure switching valve 42 to generate resistance in the opening operation of the relief valve body 15. Control is performed so that the pressure oil is applied to the relief valve body 15. On the other hand, when the pressure detected by the pressure sensor 43 is equal to or greater than a predetermined value, the controller 44 unsets the pressure oil that resists the opening operation of the relief valve main body 15 so as to be in a state of unloading. To control. Therefore, the set pressure of the relief valve main body 15 can be easily changed in two steps, high and low, according to the pressure detected by the pressure sensor 43.
(Fourth embodiment)
FIG. 4 is a view showing a hydraulic circuit 51 of a transmission with a fluid torque converter according to a fourth embodiment of the present invention. In addition, about the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The first shift speed forming clutch 8 ₁ is connected to the drain 56 via the throttle 54, and the pressure oil supplied to the first shift speed forming clutch 8 ₁ is discharged to the drain 56 via the throttle 54. Yes. When the first pressure oil to the speed forming clutch ₈₁ is not supplied, when it remains without missing oil pressure in the clutch, which may become hot due to frictional heat. By discharging the supplied hydraulic fluid to the first gear stage forming clutch 8 _1, the first gear stage for forming the clutch ₈₁ is prevented from a high temperature as described above.

Further, the hydraulic circuit 51 has a relief valve device 55 including a relief valve main body 15, a set pressure switching valve 16, and an unload function switching valve 52 as shown in FIG. The relief valve device 55 has an oil passage 53 so that pressure oil that applies pressure against the opening operation of the relief valve main body 15 flows. The oil passage 53 is connected to the set pressure switching valve 16 and the relief valve body 15. By opening and closing the oil passage 53 by the set pressure switching valve 16, unloading and onloading of the pressure oil are switched. Further, an unload function switching valve 52 is provided in the oil passage 53 between the set pressure switching valve 16 and the relief valve body 15. Unload function switching valve 52, the hydraulic pressure supplied to the first shift stage forming clutch ₈₁ and the pilot pressure, the first pressure oil to the speed forming clutch ₈₁ is supplied, closes the oil passage 53 Pilot valve.

For structure of this embodiment, the first gear stage for forming the clutch ₈₁ in order to pressure oil many flow required during operation, the pressure tends to fall in the accumulator 11. Therefore, in the configuration as in the first to third embodiments, the pressure of the accumulator 11 is likely to be less than the upper limit value capable of accumulating, and the set pressure of the relief valve body 15 is immediately increased.

In the fourth embodiment the contrary, the hydraulic circuit 51, the oil passage 53 is closed by the unload function switching valve 52 to the first gear stage for forming the clutch ₈₁ during operation. By closing the oil passage 53, pressure oil that resists the opening operation of the relief valve body 15 acts on the relief valve body 15, and the set pressure of the relief valve body 15 is maintained at the accumulator 11 upper limit of accumulative pressure. Therefore, in the first gear stage for forming the clutch ₈₁ during operation, also the pressure of the accumulator 11 is a pressure accumulator can limit can set pressure of the relief valve body 15 is maintained in the accumulator allows the upper limit of the accumulator 11 . Thereby, the fluctuation of the pressure input to the fluid type torque converter 9 due to the fluctuation of the set pressure is prevented, the load of the fluid type torque converter 9 and the equipment connected thereto is reduced, and the vibration of the equipment is reduced. Can do.
(Fifth embodiment)
FIG. 5 is a view showing a hydraulic circuit 61 of a transmission with a fluid torque converter according to a fifth embodiment of the present invention. In addition, about the structure which is common in 4th Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The hydraulic circuit 61 of the fifth embodiment, similarly to the first gear stage for forming the clutch _81, the fourth gear stage for forming clutch 8 ₄ even through the aperture 64 is connected to the drain 56. Unload function switching valve 52, one of the hydraulic pilot among the hydraulic pressure supplied to the hydraulic and fourth gear stage for forming clutch 8 ₄ supplied by the shuttle valve 63 to the first gear stage forming clutch 8 ₁ It is configured to be input as pressure.

Therefore, when operating the first gear stage forming clutch 8 ₁ or fourth gear position forming clutch 8 _4, regardless of the pressure of the accumulator 11, the oil passage 53 is closed. As a result, the set pressure of the relief valve main body 15 is maintained at the upper limit of accumulator 11 capable of accumulating pressure. In this way, even if the two hydraulic clutches 8 ₁ and 8 ₄ are connected to the drain 56, the set pressure of the relief valve main body 15 is set to the upper limit of the accumulator 11 when the hydraulic clutch 8 is operated. Since the value is maintained, the set pressure of the relief valve main body 15 is prevented from fluctuating.

The hydraulic circuit 61 has the same effects as the hydraulic circuit 51 of the fourth embodiment.
(Sixth embodiment)
FIG. 6 is a view showing a hydraulic circuit 71 of a transmission with a fluid torque converter according to a sixth embodiment of the present invention. In addition, about the structure which is common in 4th Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 6, the relief valve device 75 of this embodiment includes a relief valve main body 15, a set pressure switching valve 16, and an unload function switching valve 72. The unload function switching valve 72 is an electromagnetic on-off valve, and is disposed in the oil passage 53 similarly to the unload function switching valve 52 of the fourth embodiment. The unload function switching valve 72 is electrically connected to the controller 76.

The controller 76 is electrically connected to the shift lever 77. When the shift lever is operated to the first gear position, the controller 76 outputs that the shift lever has been operated. Controller 76, at the same time as performing the first operation of the gear stage for forming clutch 8 ₁ by the output from the shift lever 77 actuates the unload function switching valve 72 closes the oil passage 53. As a result, the pressure oil that resists the opening operation of the relief valve body 15 acts on the relief valve body 15, and the set pressure of the relief valve body 15 is maintained at the upper limit of accumulator 11 that can accumulate pressure.

The hydraulic circuit 71 configured as described above has the same effects as the hydraulic circuit 51 of the fourth embodiment.
(Seventh embodiment)
FIG. 7 is a view showing a hydraulic circuit 81 of a transmission with a fluid torque converter according to a seventh embodiment of the present invention. In addition, about the structure which is common in 6th Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. As shown in FIG. 7, the relief valve device 85 of the present embodiment includes a relief valve body 15, a set pressure switching valve 16, an unload function switching valve 82, and an electromagnetic proportional relief valve 83. Furthermore, the relief valve device 85 has first to third oil passages 85a, 85b, 85c.

  A set pressure switching valve 16 is provided in the first oil passage 85a. The second oil passage 85 b is connected to the drain 86 via the electromagnetic proportional relief valve 83. The electromagnetic proportional relief valve 83 operates in the opening direction using the hydraulic pressure of the second oil passage 85b as a pilot pressure. The electromagnetic proportional relief valve 83 is electrically connected to the controller 84, and a force corresponding to the current output from the controller 84 is applied against the pilot pressure to change the pressure of the second oil passage 85b. Is configured to do.

  The unload function switching valve 82 is a valve that connects the third oil passage 85c connected to the relief valve body 15 to one of the first oil passage 85a and the second oil passage 85b. The unload function switching valve 82 is connected to the controller 84. The controller 84 connects the third oil passage 85 c and the second oil passage 85 b to the unload function switching valve 82 based on the output from the shift lever 77. As a result, the hydraulic pressure in the second oil passage 85 b is applied to the relief valve body 15 as a hydraulic pressure that resists the opening direction of the relief valve body 15. By changing the current value of the electromagnetic proportional relief valve 83, the oil pressure of the second oil passage 85b is changed, and the set pressure of the relief valve body 15 is changed.

In the electromagnetic proportional relief valve 83, the current flowing from the controller 44 is set to such a value that the set pressure of the relief valve main body 15 can give the clutch actuation required pressure. Thus, when the shift lever for switching the first speed change stage forming clutch ₈₁ is turned ON is operated, hydraulic pressure supplied to the first shift stage forming clutch ₈₁ is a clutch actuation necessary pressure. Thus, it is possible to operate the first gear stage forming clutch 8 ₁ minimum necessary pressure. Therefore, wasteful power for accumulating the accumulator is not consumed, and the load on the hydraulic pump can be reduced.

  In addition, the set pressure of the relief valve main body 15 may not become the clutch actuation required pressure when the shift lever is operated due to individual differences for each product, environment, aging, etc., but fine adjustment of the set pressure is necessary. Thus, the set pressure can be set to the clutch actuation required pressure. Thereby, useless power can be further suppressed.

  If there is no output from the shift lever 77, the controller 84 connects the third oil passage 85c and the first oil passage 85a to the unload function switching valve 82. As a result, the set pressure of the relief valve body 15 can be switched between high and low in two steps according to the pressure of the accumulator 11 by the set pressure switching valve 16 as described above.

The hydraulic circuit 81 has the same operational effects as the hydraulic circuit 71 of the sixth embodiment.
(Eighth embodiment)
FIG. 8 is a view showing a hydraulic circuit 91 of a transmission with a fluid torque converter according to an eighth embodiment of the present invention. In addition, about the structure which is common in 3rd and 7th embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The relief valve device 95 of this embodiment includes a relief valve main body 15 and an unload function switching valve 92. The relief valve device 95 has an oil passage 93. The oil passage 93 is connected to the relief valve main body 15 and the unload function switching valve 92, and the hydraulic pressure flowing therethrough applies a pressure against the relief valve main body 15 in the opening direction.

  The unload function switching valve 92 is configured such that the pressure oil in the oil passage 93 can be discharged to the drain 94. The unload function switching valve 92 is an electromagnetic proportional relief valve that controls the oil pressure of the oil passage 93 by adjusting the opening of the oil passage 93 according to the current flowing therethrough. The unload function switching valve 92 operates in the opening direction by a pilot pressure that is a pressure against the closing direction on the relief valve main body 15, and a force against the opening direction acts when a current is passed. The unload function switching valve 92 is electrically connected to the controller 44.

  In addition to the pressure sensor 43, the controller 44 is electrically connected to the shift lever 77. When the pressure detected by the pressure sensor 43 is less than a predetermined value (upper limit of accumulator 11 pressure accumulation), the controller 44 allows an electric current to flow through the unload function switching valve 92 and causes the oil passage 93 to pass through the unload function switching valve 92. Close. As a result, a pressure against the opening direction is applied to the relief valve main body 15, and the set pressure becomes the upper limit of the accumulator 11 capable of accumulating pressure.

  On the other hand, when the pressure detected by the pressure sensor 43 is equal to or higher than a predetermined value, the controller 44 stops the current, causes the unload function switching valve 92 to open the oil passage 93, and unloads the pressure oil in the oil passage 93. Let Thereby, the set pressure becomes the set pressure of the safety valve 20 of the fluid type torque converter 9. Thus, according to the pressure detected by the pressure sensor 43, the set pressure of the relief valve main body 15 can be easily changed in two steps, high and low.

  Furthermore, even if the pressure detected by the pressure sensor 43 is equal to or greater than a predetermined value, the controller 44 sends an electric current to the unload function switching valve 92 in accordance with the output from the shift lever 77, and the unload function switching valve 92. To move in the closing direction. Thereby, the opening degree of the oil passage 93 is reduced, the oil pressure of the oil passage 93 is increased, and the set pressure of the relief valve body 15 is changed. At this time, the controller 44 adjusts the opening of the oil passage 93 by adjusting the current flowing through the unload function switching valve 92 so that the pressure detected by the pressure sensor 43 becomes the clutch operation necessary pressure. Note that the set pressure of the relief valve main body 15 when the clutch is operated can be adjusted by the controller 44.

  According to the hydraulic circuit 91, there are the same effects as the hydraulic circuit 81 of the seventh embodiment.

  As described above, the hydraulic circuit of the transmission with the fluid torque converter according to the present invention has an excellent effect of reducing the load of the hydraulic pump when the clutch is not operated, and the construction machine that can exhibit the significance of this effect. It is beneficial to apply widely to.

It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 1st Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 2nd Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 3rd Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 4th Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 5th Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 6th Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 7th Embodiment of this invention. It is drawing which shows the hydraulic circuit of the transmission with a fluid type torque converter which concerns on 8th Embodiment of this invention.

Explanation of symbols

1, 31, 41, 51, 61, 71, 81, 91 Hydraulic circuit 2 Hydraulic pumps 6, 7 Branch circuit 8 Hydraulic clutch 9 Fluid torque converter 10 Pressure reducing valve 11 Accumulator 12 Check valves 14, 45, 55, 75 , 85, 95 Relief valve device 15 Relief valve body 16, 42 Set pressure switching valve 17 Electromagnetic switching valve 18, 33, 44, 76, 84 Controller 20 Safety valve 32 Temperature sensor 43 Pressure sensor 52, 72, 82, 92 Unload function Switching valve 54, 64 Restriction 77 Shift lever 83 Electromagnetic proportional relief valve

Claims (12)

A hydraulic clutch is connected to one of the two branch circuits branching the discharge side of the hydraulic pump, and a fluid torque converter is connected to the other, allowing supply of pressure oil to the hydraulic clutch to the one branch circuit A hydraulic circuit for a transmission with a fluid torque converter provided with a pressure reducing valve for shutting off,
The one branch circuit is provided with an accumulator on the primary side of the pressure reducing valve and a check valve for preventing a backflow of pressure oil from the accumulator to the other branch circuit,
The other branch circuit is provided with a relief valve device capable of changing a set pressure at least in two steps of high and low on the upstream side of the fluid torque converter,
The relief valve device makes the set pressure higher than the secondary side pressure of the pressure reducing valve when the pressure accumulated in the accumulator is less than a predetermined value, and sets the pressure when the pressure is greater than or equal to a predetermined value. A hydraulic circuit for a transmission with a fluid torque converter, characterized in that the pressure is lower than the secondary side pressure of the pressure reducing valve.   2. The fluid type according to claim 1, wherein the relief valve device is configured to make the set pressure substantially the same as an inlet pressure of the fluid type torque converter when a pressure accumulated in the accumulator is a predetermined value or more. Hydraulic circuit for transmission with torque converter. The relief valve device is biased by a spring in the closing direction and operates in the opening direction using the primary pressure as a pilot pressure, and a state in which pressure oil is applied to resist the opening operation of the relief valve body And a set pressure switching valve capable of switching between a state in which the pressure oil is unloaded,
3. The hydraulic circuit for a transmission with a fluid torque converter according to claim 1, wherein the set pressure switching valve is configured to unload the pressure oil when a pressure accumulated in the accumulator exceeds a predetermined value. Between the relief valve device and the torque converter is provided a safety valve in which the inlet pressure of the torque converter is set lower than the secondary side pressure of the pressure reducing valve,
The set pressure switching valve is a pilot pressure that is a pressure accumulated in the accumulator,
The relief valve device is an electromagnetic that can switch between a state allowing the supply of pilot pressure from the accumulator to the set pressure switching valve and a state blocking the supply of pilot pressure from the accumulator to the set pressure switching valve. The hydraulic circuit of a transmission with a fluid type torque converter according to claim 3, further comprising a switching valve.   The hydraulic circuit for a transmission with a fluid type torque converter according to claim 4, wherein the electromagnetic switching valve is configured to be switchable by a user operation. A temperature sensor that detects an oil temperature of the hydraulic circuit; and a controller that controls the electromagnetic switching valve based on information from the temperature sensor;
The controller is configured to control the set pressure switching valve so as to be in a state of applying pressure oil that resists the opening operation of the relief valve body when the oil temperature detected by the temperature sensor is equal to or lower than a predetermined value. The hydraulic circuit of a transmission with a fluid type torque converter according to claim 3. A pressure sensor capable of detecting the pressure accumulated in the accumulator, and a controller for controlling the set pressure switching valve based on information from the pressure sensor,
The controller is configured to control the set pressure switching valve so as to be in a state of unloading pressure oil against an opening operation of the relief valve body when a pressure detected by the pressure sensor is equal to or greater than a predetermined value. The hydraulic circuit of a transmission with a fluid type torque converter according to claim 3.   The relief valve device is configured such that, when the hydraulic clutch is operated, the set pressure is made higher than the secondary pressure of the pressure reducing valve even if the pressure accumulated in the accumulator is equal to or higher than a predetermined value. The hydraulic circuit of the transmission with a fluid type torque converter according to claim 1 or 2.   The relief valve device can change the set pressure in at least three stages. When the hydraulic clutch is operated, the set pressure when the hydraulic clutch is operated causes the hydraulic clutch to operate. 9. The hydraulic circuit for a transmission with a fluid torque converter according to claim 8, wherein the hydraulic pressure circuit is configured to have a necessary pressure required for clutch operation. A pressure sensor for detecting the pressure accumulated in the accumulator; and a controller for controlling the relief valve device based on the pressure detected by the pressure sensor;
If the pressure detected by the pressure sensor is greater than or equal to a predetermined value, the controller reduces the set pressure to be lower than the secondary pressure of the pressure reducing valve, and the pressure detected by the pressure sensor is greater than or equal to a predetermined value. 8. The fluid torque converter according to claim 7, wherein the relief valve device is controlled such that when the hydraulic clutch is operated, the pressure detected by the pressure sensor becomes the required pressure for clutch operation. Hydraulic circuit of the transmission with. The relief valve device is biased by a spring in the closing direction and operates in the opening direction using the primary pressure as a pilot pressure, and a state in which pressure oil is applied to resist the opening operation of the relief valve body And a set pressure switching valve that can switch between a state in which the pressure oil is unloaded, and a state in which the pressure oil is applied so as to resist the opening operation of the relief valve body from the state in which the hydraulic pressure is unloaded With an unloading function switching valve that switches to
The set pressure switching valve is configured to switch to a state in which the pressure oil is unloaded when a pressure accumulated in the accumulator becomes a predetermined value or more,
The unload function switching valve is configured to forcibly switch from a state where the hydraulic pressure is unloaded to a state where pressure oil is applied so as to resist the opening operation of the relief valve body when the hydraulic clutch is operated. The hydraulic circuit for a transmission with a fluid type torque converter according to claim 8, wherein The one branch circuit is provided with a plurality of pressure reducing valves in parallel, and each of the plurality of pressure reducing valves is provided with the hydraulic clutch,
At least one of the plurality of hydraulic clutches is configured such that the supplied pressure oil is discharged through the throttle,
The said relief valve apparatus is comprised so that the said setting pressure may be made higher than the secondary side pressure of the said pressure reducing valve, if the hydraulic clutch which discharges the said pressure oil is operated. The hydraulic circuit of the transmission with a fluid type torque converter as described in thru | or 11.

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