Patent Publication Number: US-2010125396-A1

Title: Hydraulic control apparatus for speed ratio change

Description:
FIELD OF THE INVENTION 
     The present invention relates to a hydraulic control apparatus for speed ratio change, and more particularly, to a hydraulic transmission apparatus capable of changing a reduction ratio according to the moving status of a carrier. 
     BACKGROUND OF THE INVENTION 
     Please refer to  FIG. 1 , which shows a conventional hydraulic continuous variable transmission system. In  FIG. 1 , the variable transmission system  1  comprises an engine input shaft  10  and a torque converter  101 . The torque converter  101  is connected to an input pulley  12  through a clutch  11  while the input pulley  12  is further connected to an output pulley  14  by a metal belt  13 . Moreover, the output pulley  14  is further connected with a reduction gear set  15  as the reduction gear set  15  is connected to a differential gear  16 . As each of the two pulleys  12 ,  14  are made of two cones facing each other and the belt  13  is riding in the groove between the two cones, the belt will ride lower in the groove when the two cones of the pulley are far apart for enabling the radius of the belt loop going around the pulley to get smaller and on the contrary, the belt will ride higher in the groove when the cones are close together for enabling the radius of the belt loop going around the pulley to get larger. Thus, when an hydraulic pump is brought along to function by an engine for generating a hydraulic pressure to be used for causing the the two pulleys  12 ,  14  to perform an axial movement, the distances D between the two cones of the pulleys  12 ,  14  will be varied accordingly so that the pitch radius of the belt  13  will be caused to change and thus determines a reduction gear ratio. 
     There can be two primary types of transmission efficiency loss happening in the conventional hydraulic continuous variable transmission system, which are pressure loss and outflow rate loss. Notably, there is only one hydraulic pump used in the conventional hydraulic continuous variable transmission system of  FIG. 1  that is brought along to function by the engine in a manner that the hydraulic pressure and flow caused by the hydraulic pump will increase with the increasing of the engine rotation speed. However, such configuration will cause the conventional hydraulic continuous variable transmission system to suffer a high efficiency loss, since the hydraulic pump will keep working and thus exhausting energy even when the engine is idle. Moreover, since the energy conversion efficiency of the engine can reach no higher then  30 %, the operation of hydraulic pump driven by the engine will certainly cause great energy loss. 
     Please refer to  FIG. 2 , which shows a conventional hydraulic continuous variable transmission system disclosed in U.S. Pat. No. 7,261,672. In  FIG. 2 , there are two motor-driven hydraulic pumps  20 ,  21  being configured in this transmission system, that are used as a primary pump  20  and an secondary pump  21  for outputting pressure to control the first and the second pulleys  22 ,  23  to perform an axial movement. Thereby, the distances D between the two cones of the pulleys  22 ,  23  will be varied accordingly so that the pitch radius of its transmission belt will be caused to change and thus determines a reduction gear ratio. However, it is noted that the primary hydraulic loop of the aforesaid variable transmission system is formed by serial-connecting its secondary hydraulic circuits, so that when the two pumps  20 ,  21  are control for changing the reduction gear ratio, turbulence will be caused due to the interference between the hydraulic circuits. There is another control device disclosed in U.S. Pat. No. 6,287,227 that is designed to use a linkage mechanism as hydraulic pressure control so as to determine a reduction gear ratio for a continuous variable transmission (CVT) system. In addition, another gear ratio control device is disclosed in U.S. Pub. No. 2008/0146409, in which the hydraulic pressure is controlled and determined by a step motor which controls the open degree of a hydraulic valve, and thereby controls the reduction gear ratio to be adjusted continuously. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hydraulic control apparatus for speed ratio change capable of using two independent hydraulic drive circuits along with two hydraulic control circuits connected respectively thereto for achieve a speed ratio change in a continuous manner while maintaining a power source of the hydraulic control apparatus, such as a motor or an engine, to function within its optimum efficiency region for achieving low energy consumption and low pollution during the operation of the power source. 
     The present invention further provides a hydraulic control apparatus for speed ratio change, being a continuous variable transmission device of two independent hydraulic drive circuits and two hydraulic control circuits connected respectively thereto, that is able to enable the two hydraulic drive circuits to be parallel-connected for satisfying a comparatively large torque demand while maintaining a stable output with regard to torque and speed, by that not only the comfort and safety of carrier where the hydraulic control apparatus is mounted can be ensured as it is cruising in low speed, but also no vibration will be caused by any speed changing of the carrier. 
     The present invention further provides a hydraulic control apparatus for speed ratio change, being a continuous variable transmission device of two independent hydraulic drive circuits and two hydraulic control circuits connected respectively thereto, that is able to enable the two hydraulic drive circuits to be serial-connected for satisfying a high-speed cruising demand of a carrier as the serial connection will cause a smaller reduction ratio for enabling the carrier to cruise stably in high speed. 
     In an embodiment, the present invention provides a hydraulic control apparatus for speed ratio change, comprising: a first pulley unit, connected to a power source so as to be driven thereby; a second pulley unit, coupled to the first pulley unit by a transmission belt while being connected to a power output mechanism; a first hydraulic drive circuit, connected to the first pulley unit; a second hydraulic drive circuit, connected to the second pulley unit; a hydraulic control circuit, fluidly connected to the first and the second hydraulic drive circuits in respective; and a controller, electrically connected to the first hydraulic drive circuit, the second hydraulic drive circuit and the hydraulic control circuit; wherein, the controller is enabled to issue a control signal for controlling the hydraulic control circuit to perform a task selected from the group consisting of: enabling the first hydraulic drive circuit and the second hydraulic drive circuit to serial-connected, and enabling the first hydraulic drive circuit and the second hydraulic drive circuit to be parallel-connected. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein: 
         FIG. 1  is a sectional view of a conventional hydraulic continuous variable transmission system. 
         FIG. 2  shows a conventional hydraulic continuous variable transmission system disclosed in U.S. Pat. No. 7,261,672. 
         FIG. 3  is a schematic diagram showing a hydraulic control apparatus for speed ratio change according to an embodiment of the invention. 
         FIG. 4  shows a hydraulic control apparatus of the invention as the hydraulic drive circuits configured therein are parallel-connected. 
         FIG. 5A  and  FIG. 5B  are schematic diagrams illustrating how the pitch radius of the transmission belt is changed by the use of pulley units of the invention. 
         FIG. 6  shows a hydraulic control apparatus of the invention as the hydraulic drive circuits configured therein are serial-connected. 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     For your esteemed members of reviewing committee to further understand and recognize the fulfilled functions and structural characteristics of the invention, several exemplary embodiments cooperating with detailed description are presented as the follows. 
     Please refer to  FIG. 3 , which is a schematic diagram showing a hydraulic control apparatus for speed ratio change according to an embodiment of the invention. In this embodiment, the hydraulic control apparatus is adapted for mounting on a carrier to be used as a hydraulic continuous variable transmission device, and the carrier can be a vehicle or other transportation devices. The hydraulic control apparatus  3  of  FIG. 3  comprises: a first pulley unit  30 , a second pulley unit  31 , a first hydraulic drive circuit  32 , a second hydraulic drive circuit  33 , a hydraulic control circuit  34  and a controller  35 . The first pulley unit  30  is composed of a first fixed pulley  301  and a first movable pulley  302 , in which a fluid chamber  303  is formed sandwiching between the first fixed pulley  301  and the first movable pulley  302  and is used for holding a fluid, such as oil, therein and consequently causing a pressure to be exerted on the first movable pulley  302  so as to force the same to perform an axial movement. 
     The first pulley unit  30  is further connected to a power source  90  so as to be driven thereby. Generally, the power source can be an engine, a motor or a hybrid power source, and so on, but is not limited thereby. The second pulley unit  31  is disposed at a side of the first pulley unit  30  while being connected to the same by a transmission belt  36  so that power of the power source  90  can be transmitted from the first pulley unit  30  to the second pulley unit  31  where it is further being transmitted to a power output mechanism  37 . In this embodiment, the transmission belt  36  is a metal belt, but is not limited thereby. Similarly, the second pulley unit  31  is composed of a second fixed pulley  311  and a second movable pulley  312 , in which a fluid chamber  313  is formed sandwiching between the second fixed pulley  311  and the second movable pulley  312  and is used for holding a fluid, such as oil, therein and consequently causing a pressure to be exerted on the second movable pulley  312  so as to force the same to perform an axial movement. 
     The first hydraulic drive circuit  32  is designed to use a pipeline  320  to connect fluidly with the fluid chamber  303  by way of the first fixed pulley  301 . In this embodiment, the first hydraulic drive circuit  32  is comprised of a servo motor  321  and a hydraulic pump  322 , in which the servo motor  321  is connected to the controller  35  by a motor control unit  323 ; and the hydraulic pump  322  is connected to the servo motor  321  for receiving power from the same and thus outputting a controllable hydraulic pressure for pressing the fluid to flow through the pipeline  320  and then into the fluid chamber  303  of the first pulley unit  30 . It is noted that the hydraulic pump  322  is further connected to the hydraulic control circuit  34  by a pipeline  324 . Similarly, the second hydraulic drive circuit  33  is designed to use a pipeline  330  to connect fluidly with the fluid chamber  313  by way of the second fixed pulley  311 . Also in this embodiment, the second hydraulic drive circuit  33  is comprised of a servo motor  331  and a hydraulic pump  332 , in which the servo motor  331  is connected to the controller  35  by a motor control unit  333 ; and the hydraulic pump  332  is connected to the servo motor  331  for receiving power from the same and thus outputting a controllable hydraulic pressure for pressing the fluid to flow through the pipeline  330  and then into the fluid chamber  313  through the second fixed pulley unit  311 . Moreover, the hydraulic pump  332  is further connected to the hydraulic control circuit  34  by a pipeline  334 . 
     The hydraulic control circuit  34  is respectively connected to the first hydraulic drive circuit  32  and the second hydraulic drive circuit  33 . Moreover, the hydraulic control circuit  34  is configured with a control valve  340  which is connected to the first hydraulic drive circuit  32 , the second hydraulic drive circuit  33  and a fluid tank  341  respectively by way of the pipelines  324 ,  334 ,  341 . As shown in  FIG. 3 , there is a fluid contained in the fluid tank  341  that can be fed to the aforesaid hydraulic drive circuits for enabling the same to function. In addition, the fluid in the fluid tank can be a kind of oil. In this embodiment, the control valve  340  is configured for switching the series or parallel connection status between the first hydraulic drive circuit  32  and the second hydraulic drive circuit  33 . In this embodiment, the control valve  340  can be a solenoid electric valve, such as a 3-way, 2-position solenoid electric valve, but is not limited thereby. The controller  35  is electrically connected to the first hydraulic drive circuit  32 , the second hydraulic drive circuit  33  and the hydraulic control circuit  34  in a manner that the controller  35  is enabled to issue a control signal for controlling the hydraulic control circuit  34  to perform a task selected from the group consisting of: enabling the first hydraulic drive circuit  32  and the second hydraulic drive circuit  33  to serial-connected with each other, and enabling the first hydraulic drive circuit  32  and the second hydraulic drive circuit  33  to be parallel-connected with each other. 
     The hydraulic control apparatus for speed ratio change  3  of the invention can be adapted for all kinds of vehicles of different power source, such as engine-driven vehicles, hybrid-power vehicles or electric power vehicle, and so on. The following embodiments are provides for illustrating how the hydraulic control apparatus of the invention is used for achieving continuous variable transmission as it is being mounted on a vehicle. Please refer to  FIG. 4 , which shows a hydraulic control apparatus of the invention as the hydraulic drive circuits configured therein are parallel-connected. In  FIG. 4 , the hydraulic control apparatus  3  is coupled to an engine  91  and a kind of oil is used as the fluid in the fluid circuit of the hydraulic control apparatus  3 . It is noted that when the engine  91  is just being started and is operating within its worst operation efficiency region, it is the time when the vehicle is driven to move from a standing stop and thus it is the time requiring the engine to output a large torque with low rotation speed. Therefore, a transmission with high reduction ratio is required, since it can rapidly switch the engine from operating in a low-speed low-efficiency status to a high-speed high-efficiency status. For obtaining a transmission with high reduction ratio, the pitch radius of the first pulley unit  30 , known as the distance between the center of the first pulley unit  30  to where the metal belt  36  makes contact in the groove, should be smaller than that of the second pulley unit  31 . In another word, the oil pressure exerting on the first pulley unit  30  should be smaller than that on the second pulley unit  31 . Please refer to  FIG. 5A  and  FIG. 5B , which are schematic diagrams illustrating how the pitch radius of the transmission belt is changed by the use of pulley units of the invention. Taking the first pulley unit  30  for instance, it is known that the pitch radius of the first pulley unit  30  can be increased by enabling the pump to pressurize the fluid for forcing the same to flow into the fluid chamber  303 . Since the hydraulic pressure in the fluid chamber  303  will force the first movable pulley  302  to move foreward as depicted in  FIG. 5A , the distance between the first fixed pulley  301  and the first movable pulley  302  will be changed in consequency while enabling the metal belt  36  to move upward accordingly and thus the distance between the center of the first pulley unit  30  to where the metal belt  36  makes contact in the groove is increased, as shown in  FIG. 5B . Moreover, the aforesaid description is also true for the second pulley unit  31 . 
     In  FIG. 4 , the controller  35  issues control commands to the motor control units  323 ,  333  for controlling the rotation speeds of the two servo motors  321 ,  331  accordingly, through which controls the output pressures of the hydraulic pumps  322 ,  333  as they are connected respectively to the first and the second pulley units  30 ,  31 . When the control valve  340  is maintained at its normal position for enabling a parallel connection in its hydraulic circuits, the hydraulic pump  332  connecting to the second pulley unit  31  and the hydraulic pump  322  connecting to the first pulley unit  30  will be able to establish their hydraulic pressures independent from each other which are then being used for forcing the fluid to flow into the fluid chambers  303 ,  313  in corresponding to their respective hydraulic pressures and thus causing the first and the second movable pulleys  302 ,  312  to perform their corresponding axial movements. In addition, as the controller  35  will direct the servo motor  321  to rotate slower than the servo motor  331 , the hydraulic pressure of the hydraulic pump  322  connecting to the first pulley unit  30  will be smaller than that of the hydraulic pump  31  connecting to the second pulley unit  31  which will enable the hydraulic control apparatus to achieve its maximum reduction ratio. 
     Please refer to  FIG. 6 , which shows a hydraulic control apparatus of the invention as the hydraulic drive circuits configured therein are serial-connected. When the vehicle is moving in high speed, it is the time requiring the engine to output a small torque with high rotation speed. Thus, for maintaining the engine to operate stably in high efficiency region as it is rotating in high speed, a transmission with low reduction ratio is required. For achieving a transmission with low reduction ratio, the pitch radius of the first pulley unit  30  should be equal to or slightly smaller than that of the second pulley unit  31 . In another word, the oil pressure exerting on the first pulley unit  30  should be larger than that on the second pulley unit  31 . Similarly, the controller  35  will issues control commands to the motor control units  323 ,  333  for controlling the rotation speeds of the two servo motors  321 ,  331  accordingly, through which controls the output pressures of the hydraulic pumps  322 ,  333  as they are connected respectively to the first and the second pulley units  30 ,  31 . However, at this time, the control valve  340  of the hydraulic control circuit  34  will be activated to switch its hydraulic circuits from parallel connection into series connection. In this series connection, the hydraulic pressure of the hydraulic pump  332  connecting to the second pulley unit  31  is diverted to the two pipelines  320 ,  330 , in which the pipeline  330  is fluidly connected to the fluid chamber  313  sandwiched between the second fixed pulley  311  and the second movable pulley  310  for forcing the second movable pulley  310  to perform an axial movement; and the pipeline  320  is connected to another hydraulic pump  322  where the fluid is further pressurized and then forced to flow into the fluid chamber  303  for causing the first movable pulley  302  to move. As the pressure in the fluid chamber  303  will gain from both the two hydraulic pumps  322 ,  332 , it is larger than that in another fluid chamber  313  gaining only from the hydraulic pump  332 . Thus, the rotation speed of the servo motor  321  in the first hydraulic drive circuit  32  will be larger than that of the servo motor  331  in the second hydraulic drive circuit  33  which will enable the hydraulic control apparatus to achieve its minimum reduction ratio. 
     Except for starting to move from standing stop and cruising in high speed, the controller  35  is able to issue control commands according to different moving status of an accelerating carrier for controlling the servo motors  321 ,  331  and the hydraulic control circuit  34  and thus optimizing the performance of the power source while obtaining an optimal power transmission efficiency. In addition, the transmission control can be adjusted for matching with the optimal working efficiency regions of different power sources. 
     To sum up, the present invention provides a hydraulic control apparatus for speed ratio change that is capable of achieving a speed ratio change in a continuous manner while maintaining a power source of the hydraulic control apparatus to function within its optimum efficiency region for achieving low energy consumption and low pollution during the operation of the power source. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.