JP2010025197A - Electric hydraulic control system for hydraulic torque distribution adjustment differential - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric hydraulic control system for hydraulic torque distribution adjustment differential. <P>SOLUTION: A torque distribution adjustment system controls torque supplied to a pair of axles 30 for wheels of an automobile through a power train. The torque distribution adjustment system includes a hydraulic pump 12 and a hydraulic motor 14. A connection line of the hydraulic pump 12 is communicated with the hydraulic pump 12, and a connection line of the hydraulic motor 14 is communicated with the hydraulic motor 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic control system for an automotive differential device that provides axle torque distribution adjustment with overspeed capability.

  Conventional rear-wheel drive vehicles supply wheel drive torque by means of a propeller shaft connected to the left and right axles via a differential. In a front wheel drive vehicle, it is connected to a front wheel drive axle via a differential driven by a transaxle. Four-wheel drive vehicles and so-called all-wheel drive vehicles also use differentials to drive the front and rear axles. The differential allows a difference in wheel rotation speed to occur between the left and right drive axles (and in some applications between the front and rear axles). The earliest and most basic design of a differential is known as an open differential, but in this case the differential provides a constant torque between the two axles and the relative rotation of the axles It doesn't work to control speed. A well-known drawback of open differentials occurs when one of the drive wheels contacts a low friction coefficient (μ) road surface and the other wheel has a high μ. In such a case, since the traction force generated on the low μ contact surface is low, it is prevented that a large torque is generated on any axle. Since the torque between the two axles is relatively constant, almost no total tractive force can be generated to move the vehicle from that position. Similar disadvantages occur in dynamic conditions during operation, especially in low μ or so-called split μ driving conditions.

  The above limitations of open differential are well known and many design solutions have been attempted to address this shortcoming. One solution is known as lock differential. These systems are usually operated mechanically or hydraulically and use other strategies to connect the two axles together to rotate at an almost constant speed. Thus, under this operating condition, the two axles are not torque limited with respect to each other. Mechanical lock differentials typically use a clutch pack or friction material interface that locks the two axles together when a significant speed difference is detected between the axles. Other systems incorporate fluid connections between axles that provide a certain level of speed connection.

  While the above-described lock differential systems provide significant advantages over open differentials in many operating conditions, they also have important limitations. Reliability and warranty issues are problems in many lock differential designs. Lock differentials that use a mechanical friction interface face friction material wear.

  Another fundamental drawback of the lock differential is that the lock differential can basically only supply torque that acts to reduce wheel speed differences between the axles. It is impossible to increase the speed of one axle with respect to the other axle, which is realized by transmitting torque from one axle to the other axle.

  Vehicle powertrain and suspension designers take into account the forces acting on the tire contact surface to achieve the required traction, braking, steering and steering behavior in the vehicle. As a result, the force acting on the tire contact surface is decomposed into vertical and horizontal vector components. Automobile designers often desire to manage these tire force vectors to provide the required level of steering characteristics, particularly the required level of characteristics referred to as oversteer and understeer conditions. In order to prevent oversteer and understeer in maneuvers around a curve, it is well known to adjust the wheel contact distribution using brake torque. Such electronically controlled braking systems are known by various names and acronyms, for example, names such as Dynamic Stability Control (DSC) and Electronic Stability Program (ESP). However, these systems only work in the energy decay (eg braking) mode. It would be highly desirable to adjust the wheel contact distribution by managing the redistribution of torque at each wheel. The above-mentioned lock differential cannot perform wide control of wheel traction force distribution adjustment. A differential design that allows overspeed of one wheel, in other words, allows for a faster drive than the other wheel to control torque distribution, for example, is a highly desirable property. It is.

  The present invention relates to a control system for an electrohydraulic torque distribution adjustment differential for automotive applications. The system of the present invention uses a hydraulic pump driven by a differential carrier. The hydraulic motor is coupled to a planetary gear unit that couples the differential carrier to one axle. This connection provides control for both axles through differential gear coupling. The hydraulic motor can be driven in either direction, and can be produced while highly controlling the relative speed difference between the axles. In designing a mass-produced automotive product, cost and reliability are fundamental requirements along with performance characteristics. The electrohydraulic control system of the present invention uses relatively low cost valves and circuit elements. This feature is achieved in part by using a low pressure servo controlled hydraulic circuit.

  The hydraulic motor coupled to the differential in the system of the present invention can be driven by various variable displacement pumps such as a so-called oblique shaft type that can be operated in one or both rotational directions. Hydraulic fluid is supplied to the motor in either direction by an electronically controlled directional control valve to provide the required control. A hydraulic circuit can also be used to hydraulically lock the hydraulic motor. As a result, the system operates in approximately the same lock mode as the lock differential, if desired.

  These and other aspects and advantages of the present invention will become apparent from the detailed description of the invention in conjunction with the accompanying drawings.

  A hydraulic torque distribution adjustment differential system is schematically shown in FIG. This system is indicated generally at 10. The basic components of the system 10 include a hydraulic pump 12, a hydraulic motor 14, a differential gear assembly 16, a planetary gear device 32, and a hydraulic circuit 18. Basic mechanical features are described first, followed by a description of the hydraulic control system and operating system.

  A differential assembly 16 shown in FIG. 1 includes basic elements of a normal differential assembly, and includes a ring gear 22 driven by a bevel gear pinion 17 connected to a propeller shaft (not shown) of a vehicle. The ring gear 22 is coupled to a differential carrier 24 that rotates with the ring gear. A pair of planet gears 26 can rotate about a common differential shaft 20 attached to the carrier. The planetary gear 26 meshes with a pair of side gears 28 that are subsequently splined or otherwise coupled to a pair of axles 30 for the left and right wheels of the vehicle. The components of the differential 16 described here are general components of a so-called open differential. Front-wheel drive vehicles often use a planetary gear unit differential. However, this system also basically functions in the same way as the above design and can be used with the present invention.

  The planetary gear unit 32 is mechanically coupled to the differential 16 to provide torque distribution adjustment and overspeed capability according to the present invention. Basically, the planetary gear set 32 allows a controlled variable ratio mechanical connection between one axle 30 and the differential carrier 24. Due to the mechanical coupling between the components of the differential 16, this connection allows complete control over the relative speed of both axles 30. The planetary gear set 32 includes a pair of planetary gear carriers 34 and 36, which are coupled to the differential carrier 24 and the axle 30, respectively. Planetary gear sets 38 and 40 associated with planet carriers 34 and 36, respectively, engage a common ring gear 42. The planetary gear 38 meshes with the sun gear 44, but the sun gear 44 is fixed to the differential structure and does not rotate. However, the sun gear 46 is connected to the drive gear 48. This drive gear 48 meshes with the output side of the hydraulic motor 14 via a series of gears 50, 52 and 54 and provides the required speed and torque connection between the planetary gear unit 32 and the hydraulic motor 14. Since the sun gear 44 is fixed and the rotation of the sun gear 46 is controlled by the operation of the hydraulic motor 14, complete control over the relative speed between the differential carrier 24 and the axle 30 is provided. This provides control over the relative speed between the two axles 30 as described above. A series of connecting gears 53, 55, 56 and 58 rotate the input shaft 60 of the hydraulic pump 12 driven by the rotation of the differential carrier 24. Thus, the pump 12 rotates whenever the differential carrier rotates.

  In one embodiment of the present invention, the hydraulic pump 12 is preferably of the so-called oblique axis type that includes a plurality of reciprocating pistons coupled to a drive plate. By changing the angle of the shaft between the cylinder and the drive plate surface, a variable positive displacement hydraulic output to the motor 14 can be provided. Thus, if no torque distribution adjustment or lock function is required, the pump displacement can be set to zero or very near zero to reduce pressurization losses associated with the pump.

  The hydraulic pump 12 includes a first hydraulic pump connection line 68 that is in fluid communication with the priority control valve 70. The priority control valve 70 includes a control valve output line 72 that supplies flow to the hydraulic motor 14. The control valve 70 controls the pressure directed to the control solenoid supply line / lubricating circuit 71 through the low pressure output line 88. If additional flow is still available after maintaining sufficient pressure on the lubrication circuit 71, the regulator valve 70 fully opens the port connecting the first hydraulic pump connection line 68 and the hydraulic motor 14. If the minimum pressure is not supplied to the low pressure output line 88, the valve closes the flow to the control valve output line 72 and directs the entire flow from the hydraulic pump 12 to the lubrication circuit 71. The control valve output line 72 is in communication with the flow direction valve 74. The flow direction valve 74 includes first and second flow states. In the first flow state, the control valve output line 72 is connected to the first hydraulic motor connection line 76. The pressure of the hydraulic flow through the hydraulic motor 14 passing from the first hydraulic motor connection line 76 to the second hydraulic motor connection line 78 drives the gear 54 in the first direction, thereby transferring torque to the differential assembly and axle 30. Supply.

  The second hydraulic motor connection line 78 is in fluid communication with the flow direction valve 74 to connect the second hydraulic motor connection line 78 to the second hydraulic pump connection line 80, thereby returning to the hydraulic pump 12. Is completed.

  In the second flow state of the flow direction valve 74, the control valve output line 72 is connected to the second hydraulic motor connection line 78, and the first hydraulic motor connection line 76 is connected to the connection line 80, ie, the pump suction port. The Accordingly, the flow direction valve 74 selectively reverses the flow through the hydraulic motor 14 and drives the gear 54 in a second direction opposite to the first direction.

  An actuator, such as an electric motor 82, is in mechanical communication with the hydraulic pump 12, and is configured to control the hydraulic pump 12 to change the displacement and adjust the pump output pressure. A pressure sensor 84 is in fluid communication with the first hydraulic pump connection line 68 and is configured to generate a control signal for the electric motor 82 based on the measured system pressure. As a result, an electrical feedback loop is created that regulates the flow of output supplied by the hydraulic pump 12. In this manner, the electric motor 82 can be used to increase the pressure in the hydraulic circuit, whereby torque can be added to or subtracted from one axle (depending on the direction of flow). This results in an overspeed or underspeed of one wheel that improves steering and vehicle control by adjusting the distribution of wheel torque, for example in turning conditions.

  Under normal operating conditions, it is desirable to operate the differential assembly in the open differential mode. For this reason, the differential pressure operating valve 86 is provided in parallel to the hydraulic motor 14. When this valve is activated, flow through this differential pressure actuated valve 86 is no longer possible and the entire flow from the control valve output line 72 is communicated to the hydraulic motor 14. Instead, when the differential pressure operating valve 86 is in the bypass state, the differential pressure operating valve 86 connects the first hydraulic motor connection line 76 to the second hydraulic motor connection line 78 to bypass the hydraulic motor 14. In this bypass condition, the hydraulic pump 12 can rotate freely without the resistance of the hydraulic motor, allowing the differential assembly to operate as an open differential.

  The regulator valve 70 also includes a low pressure output line 88 configured to drive the fluid control circuit. The low pressure output line 88 can supply a pressure that is significantly lower than the torque distribution adjustment pressure supplied through the hydraulic motor 14 to the control solenoid. For example, the pressure controlling the solenoid can be about 50-500 PSI, and in many examples can be less than about 200 PSI, such as 100 PSI for the illustrated example. The low pressure output line 88 is in communication with a flow direction solenoid 92 configured to operate the spool of the flow direction valve 74 between a first flow state and a second flow state. Similarly, the low pressure output line 88 is also in fluid communication with a differential pressure activated solenoid 90 that is configured to operate the differential pressure activated valve 86 between an active state and a bypass state. As a result, the flow direction solenoid 92, the differential pressure operation solenoid 90, the pressure sensor 84, and the electric motor 82 can be electrically connected to the controller 94. The controller 94 is configured to operate the solenoids 90, 92 and the electric motor 82 based on the need for vehicle torque distribution adjustment. The controller 94 also provides the electric motor 82, the flow direction solenoid 92, and the differential pressure actuated solenoid 90 with information obtained from other subsystems of the vehicle, i.e. vehicle speed, throttle position, lateral acceleration and steering handle. It is also possible to communicate with other vehicle systems so as to operate based on information including the angle.

  Those skilled in the art will readily appreciate that the above description is intended to exemplify the practice of the principles of the invention, and the invention is defined by the following claims. The specification is not intended to limit the scope or application of the invention in that it may be modified, changed and modified without departing from the spirit of the invention.

1 is a schematic diagram of a hydraulic torque distribution adjustment system according to one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydraulic torque distribution adjustment differential system 12 Hydraulic pump 14 Hydraulic motor 16 Differential gear assembly 17 Bevel gear pinion 18 Hydraulic circuit 20 Differential shaft 22 Ring gear 24 Differential carrier 26 Planetary gear 28 Side gear 30 Axle 32 Planetary gear unit 34 Planetary carrier 36 Planetary carrier 36 Planetary carrier 36 Planetary carrier 36 Planet 38 planetary gear 40 planetary gear 42 ring gear 44 sun gear 46 sun gear 48 drive gear 50 gear 52 gear 53 connection gear 54 gear 55 connection gear 56 connection gear 58 connection gear 60 hydraulic pump input shaft 68 first hydraulic pump connection line 70 priority control valve 71 Lubrication circuit 72 Control valve output line 74 Flow direction valve 76 First hydraulic motor connection line 78 Second hydraulic motor connection line 80 second hydraulic pump connection line 82 the electric motor 84 the pressure sensor 86 differential pressure actuated valve 88 low-voltage output line 90 the differential pressure actuating solenoid 92 flow direction solenoid 94 controls

Claims (20)

A torque distribution adjustment system (10) for controlling torque supplied to a pair of axles (30, 32) of a vehicle wheel via a power train;
A hydraulic pump (12) in communication with the differential assembly (16) and configured to be driven by the differential assembly (16);
A hydraulic motor (14) in communication with the differential assembly (16) for controlling the supply of drive torque to the axle pair (30, 32);
A hydraulic pump connection line (68) in fluid communication with the hydraulic pump (12);
A hydraulic motor connection line (76) in fluid communication with the hydraulic motor (14);
A torque distribution adjustment system including:
The hydraulic pump connection line (68) communicates with the hydraulic motor connection line (76) via a regulation valve (70), and the regulation valve (70) communicates with the hydraulic motor connection line (76). 1 control valve output line (72) and a second control valve output line, and further when the second flow through the control valve priority output line (88) exceeds a minimum pressure , Configured to allow a first flow between the hydraulic pump connection line (68) and the first control valve output line (72) to supply to the hydraulic motor (14),
Torque distribution adjustment system.   The system of claim 1, further comprising a differential pressure operated valve (86) connected to the hydraulic motor connection line (76) and configured to selectively bypass the hydraulic motor (14).   The system of claim 1, further comprising a flow direction valve (74) configured to selectively reverse the flow through the hydraulic motor (14).   The system of claim 1, wherein the regulator valve priority output line (88) is configured to provide a low pressure flow to a valve control circuit.   The system of claim 4, wherein the low pressure is significantly lower than a pressure required for torque distribution adjustment.   The valve control circuit includes a solenoid (92) configured to operate a flow direction valve (74), the flow direction valve (74) reversing the flow through the hydraulic motor (14). The system of claim 4, wherein the system is configured.   The valve control circuit includes a solenoid (90) configured to operate a differential pressure operated valve (86), the differential pressure operated valve (86) configured to bypass the hydraulic motor (14). The system according to claim 4.   The system of claim 1, wherein a priority output line (88) of the regulator valve supplies the second flow to a lubrication circuit (71). A torque distribution adjustment system for controlling torque supplied to a pair of axles (30, 32) of a vehicle wheel via a power train,
A hydraulic pump (12) in communication with the differential assembly (16) and configured to be driven by the differential assembly (16);
A hydraulic motor (14) in communication with the differential assembly (16) to control the direction and magnitude of the distribution adjustment torque across the axle pair (30, 32);
A first hydraulic pump connection line (68) in fluid communication with the hydraulic pump (12);
A first hydraulic motor connection line (76) in fluid communication with the hydraulic motor (14);
An electric motor (82) configured to adjust the volume of the hydraulic pump (12) and thereby control the output of the hydraulic pump;
A pressure sensor (84) in communication with the electric motor (82) and configured to supply a control signal to the electric motor (82), thereby adjusting the output of the hydraulic pump (12); ,
Including torque distribution adjustment system.   The system of claim 9, wherein the pressure sensor (84) is configured to sense a pump output pressure between the hydraulic pump (12) and a regulator valve (70).   The system of claim 9, wherein the first hydraulic pump connection line (68) communicates with a regulating valve (70), further comprising a differential pressure actuated valve (86), wherein the differential pressure actuated valve (86) 86) communicates with the control valve (70) and selectively guides the flow from the control valve output line (72) to the hydraulic pump (12), bypassing the hydraulic motor (14), A system configured to bypass the hydraulic motor (14).   The system of claim 9, further comprising a flow direction valve (74), wherein the flow direction valve (74) connects the first hydraulic pump connection line (68) to the first hydraulic motor connection line (76). Or alternatively, by connecting the first hydraulic pump connection line (68) to the second hydraulic motor connection line (78), the flow through the hydraulic motor (14) is selectively selected. A system that is configured to reverse.   The system of claim 9, wherein the priority output line (88) of the regulator valve is configured to provide a low pressure flow to the valve control circuit.   The system of claim 13, wherein the low pressure stream is about 50-500 PSI.   The valve control circuit includes a solenoid (92) configured to operate a flow direction valve (74), the flow direction valve (74) reversing the flow through the hydraulic motor (14). 14. The system of claim 13, wherein the system is configured.   The valve control circuit includes a solenoid (90) configured to operate a differential pressure operated valve (86), the differential pressure operated valve (86) configured to bypass the hydraulic motor (14). The system of claim 13. A torque distribution adjustment system for controlling the direction and magnitude of torque supplied to a pair of axles (30, 32) of a vehicle wheel via a power train,
A hydraulic pump (12) in communication with the differential assembly (16) and configured to be driven by the differential assembly (16);
A hydraulic motor (14) in communication with the differential assembly (16) to control the direction and magnitude of the distribution adjustment torque across the axle pair (30);
A first hydraulic pump connection line (68) in fluid communication with the hydraulic pump (12);
First and second hydraulic motor connection lines (76, 78) each in fluid communication with the hydraulic motor (14);
A differential pressure operated valve (86) configured to selectively bypass the hydraulic motor (14);
Including torque distribution adjustment system.   The system of claim 17, wherein the differential pressure actuated valve (86) connects the first and second hydraulic motor connection lines (76, 78), thereby bypassing the hydraulic motor (14). A torque distribution adjustment system for controlling torque supplied to a pair of axles (30, 32) of a vehicle wheel via a power train,
A hydraulic pump (12) in communication with the differential assembly (16) and configured to be driven by the differential assembly (16);
A hydraulic motor (14) in communication with the differential assembly (16) to control the direction and magnitude of the distribution adjustment torque across the axle pair (30, 32);
A first hydraulic pump connection line (68) in fluid communication with the hydraulic pump (12);
First and second hydraulic motor connection lines (76, 78) each in fluid communication with the hydraulic motor (14);
A flow direction valve (74) configured to selectively reverse the flow through the hydraulic motor (14);
Including torque distribution adjustment system.   The flow direction valve (74) selectively connects the first hydraulic motor connection line (76) to the first hydraulic pump connection line (68) or the second hydraulic motor connection line (78). 20. The system of claim 19, wherein the system is selectively connected to the first hydraulic pump connection line (68), thereby selectively reversing the flow through the hydraulic motor (14).

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