JP4671750B2 - Shift control device for continuously variable transmission - Google Patents

Description

  The present invention relates to a shift control device for a continuously variable transmission mounted on a vehicle.

  A belt type continuously variable transmission (CVT) mounted on a power transmission system of a vehicle includes a primary pulley provided on an input shaft, a secondary pulley provided on an output shaft, and a drive belt stretched around these pulleys. The transmission ratio is controlled steplessly by changing the winding diameter of the drive belt around the pulley. Each of the primary pulley and the secondary pulley includes a fixed sheave and a movable sheave facing the fixed sheave, and the winding diameter and tension of the drive belt can be controlled by moving the movable sheave in the axial direction. Yes.

  For example, when the tension of the drive belt is controlled by the secondary pulley, the target secondary pressure is calculated based on the target gear ratio and the input torque, and the secondary pressure regulated toward the target value is supplied to the secondary pulley. Will be. Further, when the winding diameter of the drive belt is controlled by the primary pulley, the target speed ratio is set by referring to the speed change characteristic map based on the throttle opening, the vehicle speed, etc., and the primary pressure corresponding to the target speed ratio is set. The hydraulic ratio with the secondary pressure is set. Then, after the target primary pressure is set based on the target secondary pressure and the hydraulic pressure ratio described above, the primary pressure adjusted toward this target value is supplied to the primary pulley.

As described above, as a pressure adjusting method for adjusting the primary pressure and the secondary pressure, the hydraulic oil discharged from the oil pump is adjusted to the line pressure by the line pressure control valve, and then the line pressure is set via the primary pressure control valve. A one-pressure adjustment system has been developed in which the primary pressure is adjusted from the first pressure while the line pressure is used as the secondary pressure as it is (see, for example, Patent Documents 1 and 2). Further, not only the primary pressure is regulated by the primary pressure control valve, but also a double pressure regulation system (for example, see Patent Document 3) in which the secondary pressure is regulated from the line pressure via the secondary pressure control valve has been developed. Yes.
JP-A-6-109114 Japanese Patent Laid-Open No. 8-178042 JP 2001-330117 A

  By the way, in the continuously variable transmission that employs the above-described single pressure control method, it is possible to reduce the cost by reducing the secondary pressure control valve. However, the line pressure and the secondary pressure are the same. Therefore, when the downshift is performed, the secondary pressure is brought close to the line pressure, and when the upshift is performed, it is impossible to adjust the secondary pressure lower than the line pressure. Thus, when the primary pressure cannot be regulated higher than the secondary pressure during upshifting, the pressure receiving area of the primary pulley needs to be set larger than the pressure receiving area of the secondary pulley, and the continuously variable transmission Was supposed to lead to an increase in size. On the other hand, in the continuously variable transmission of the double pressure control system, the primary pressure can be adjusted above the secondary pressure, and the pressure receiving area of the primary pulley can be reduced. Not only can the size be reduced, but it is also possible to improve the shift speed when shifting to the overdrive side.

  However, in a continuously variable transmission that employs both pressure regulating methods, it is necessary to control the line pressure, primary pressure, and secondary pressure separately, so the hydraulic oil from the oil pump is regulated to the line pressure. It is necessary to provide a line pressure control valve, a primary pressure control valve that regulates the primary pressure from the line pressure, and a secondary pressure control valve that regulates the secondary pressure from the line pressure. As these control valves, an electromagnetic control valve that controls the energization state of the solenoid to regulate the hydraulic oil is employed, which leads to an increase in the cost of the hydraulic control circuit. In addition, in order to control the line pressure, the primary pressure, and the secondary pressure, it is necessary to incorporate a hydraulic sensor in each of the line pressure path, the primary pressure path, and the secondary pressure path, resulting in further cost increase of the hydraulic control circuit. It was also.

  An object of the present invention is to improve the transmission speed and reduce the size of the continuously variable transmission, and to reduce the cost of the hydraulic control circuit.

  A transmission control apparatus for a continuously variable transmission according to the present invention includes a transmission pulley around which a drive belt is wound and a tightening pulley, and controls the winding diameter of the drive belt using the transmission pulley, while the tightening pulley is A transmission control device for a continuously variable transmission that controls the tension of a precursor drive belt using a line pressure control valve that adjusts hydraulic oil discharged from a hydraulic supply source to a line pressure, the line pressure control valve, A clamping pressure control valve that is provided between the clamping pulley and adjusts the line pressure to the clamping pressure for the clamping pulley; and a main control pressure chamber provided in the line pressure control valve and the clamp pressure control valve. A first pilot valve that controls supply of pilot pressure to both sides, and a second that controls supply of pilot pressure to a sub-control pressure chamber provided in one of the line pressure control valve and the clamp pressure control valve. A control signal that outputs a control signal to the pilot valve, the first pilot valve, and increases or decreases both the line pressure and the clamp pressure; a control signal is output to the second pilot valve; And a differential pressure setting means for separating the clamp pressure.

  In the continuously variable transmission control device according to the present invention, the line pressure control valve and the clamp pressure control valve are pressure reducing valves in which an upper limit pressure is set based on a pilot pressure.

  In the transmission control device for a continuously variable transmission according to the present invention, the sub control pressure chamber is provided in the line pressure control valve, and the line pressure is regulated higher than the clamp pressure based on a control signal from the differential pressure setting means. It is characterized by that.

  The transmission control device for a continuously variable transmission according to the present invention includes a clamp pressure sensor that is provided between the clamp pressure control valve and the tightening pulley, detects a clamp pressure, a clamp pressure from the clamp pressure sensor, and the clamp pressure sensor. Pressure estimation means for estimating the line pressure based on the control state of the second pilot valve.

  According to the present invention, since the line pressure and the clamp pressure can be separated by controlling the second pilot valve according to the shift state, the shift pressure supplied to the shift pulley is adjusted to be higher than the clamp pressure. It becomes possible to press. As a result, the pressure receiving area on the transmission pulley side can be reduced to reduce the size of the continuously variable transmission, or the transmission speed can be improved to shorten the transmission time. Further, since the line pressure and the clamp pressure can be separated as necessary, it is not necessary to always set the line pressure high, and the load on the hydraulic pressure supply source can be reduced.

  In addition, since the circuit structure is such that a line pressure control valve and a clamp pressure control valve that are mechanically operated are provided and two pilot valves that drive and control these are provided, an increase in the cost of the hydraulic control circuit is avoided. Can do. In other words, by incorporating three electromagnetic pressure control valves that regulate the line pressure, transmission pressure, and clamp pressure separately, the conventional transmission control device (both pressure regulation methods) can regulate the clamping pressure and the transmission pressure freely. ), The development cost and manufacturing cost can be greatly reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a skeleton diagram showing a continuously variable transmission 10 controlled by a shift control apparatus according to an embodiment of the present invention. As shown in FIG. 1, the continuously variable transmission 10 is a belt-type continuously variable transmission, and includes a primary shaft 12 driven by an engine 11 and a secondary shaft 13 parallel to the primary shaft 12. A transmission mechanism 14 is provided between the primary shaft 12 and the secondary shaft 13. The rotation of the primary shaft 12 is transmitted to the secondary shaft 13 via the transmission mechanism 14, and the rotation of the secondary shaft 13 is transmitted to the speed reduction mechanism 15 and the secondary shaft 13. It is transmitted to the left and right drive wheels 17 and 18 through the differential mechanism 16.

  The primary shaft 12 is provided with a primary pulley 20 as a speed change pulley. The primary pulley 20 and a fixed sheave 20a integrated with the primary shaft 12 are opposed to the primary shaft 12 and slide on the primary shaft 12 in the axial direction. And a movable sheave 20b that is freely mounted. The secondary shaft 13 is provided with a secondary pulley 21 as a tightening pulley. The secondary pulley 21 has a fixed sheave 21a integrated with the secondary shaft 13 and the secondary shaft 13 facing the secondary shaft 13 in the axial direction. And a movable sheave 21b that is slidably mounted. A driving belt 22 is wound around the primary pulley 20 and the secondary pulley 21, and the winding diameter of the driving belt 22 can be changed steplessly by changing the pulley groove width between the primary pulley 20 and the secondary pulley 21. It is possible. If the winding diameter of the drive belt 22 around the primary pulley 20 is Rp and the winding diameter around the secondary pulley 21 is Rs, the transmission ratio of the continuously variable transmission 10 is Rs / Rp.

  In order to change the pulley groove width of the primary pulley 20, a plunger 23 is fixed to the primary shaft 12, and a cylinder 24 slidably contacting the outer peripheral surface of the plunger 23 is fixed to the movable sheave 20b. A hydraulic oil chamber 25 is defined by the cylinder 24. Similarly, in order to change the pulley groove width of the secondary pulley 21, a plunger 26 is fixed to the secondary shaft 13, and a cylinder 27 slidably contacting the outer peripheral surface of the plunger 26 is fixed to the movable sheave 21b. A hydraulic oil chamber 28 is defined by the plunger 26 and the cylinder 27. Each pulley groove width is controlled by adjusting the primary pressure Pp supplied to the primary hydraulic fluid chamber 25 and the secondary pressure Ps supplied to the secondary hydraulic fluid chamber 28.

  A torque converter 30 and a forward / reverse switching mechanism 31 are provided between the crankshaft 11 a and the primary shaft 12 to transmit engine power to the primary pulley 20. The torque converter 30 includes a pump shell 30a connected to the crankshaft 11a and a turbine runner 30b facing the pump shell 30a. A turbine shaft 32 is connected to the turbine runner 30b. Furthermore, a lock-up clutch 33 for fastening the crankshaft 11a and the turbine shaft 32 is incorporated in the torque converter 30 according to the running state.

  The forward / reverse switching mechanism 31 includes a double pinion planetary gear train 34, a forward clutch 35, and a reverse brake 36. By operating the forward clutch 35 and the reverse brake 36, the transmission path of engine power is changed. It can be switched. When both the forward clutch 35 and the reverse brake 36 are released, the turbine shaft 32 and the primary shaft 12 are disconnected, and the forward / reverse switching mechanism 31 is switched to a neutral state in which power is not transmitted to the primary shaft 12. When the forward clutch 35 is engaged with the reverse brake 36 released, the rotation of the turbine shaft 32 is transmitted to the primary pulley 20 as it is, and the forward clutch 35 is released. When the reverse brake 36 is engaged, the reverse rotation of the turbine shaft 32 is transmitted to the primary pulley 20.

  FIG. 2 is a schematic diagram showing a hydraulic control system and an electronic control system of the continuously variable transmission 10. As shown in FIG. 2, in order to supply hydraulic oil to the primary pulley 20 and the secondary pulley 21, the continuously variable transmission 10 is provided with an oil pump 40 as a hydraulic supply source driven by the engine 11. A line pressure control valve 42 is connected to the line pressure path 41 connected to the discharge port of the oil pump 40, and the line pressure control valve 42 regulates the line pressure PL that is the basic hydraulic pressure of the hydraulic control circuit. Yes. The line pressure path 41 is branched, and one line pressure path 41 a extending toward the secondary pulley 21 is connected to the secondary pressure control valve 43 and the other line pressure path extending toward the primary pulley 20. 41 b is connected to the upshift valve 44. Further, a branch oil passage 46 is formed in the primary pressure passage 45 extending from the upshift valve 44 toward the hydraulic oil chamber 25, and a downshift valve 47 is connected to the branch oil passage 46.

  The secondary pressure Ps supplied to the secondary hydraulic oil chamber 28 is regulated via a secondary pressure control valve 43, and this secondary pressure control valve 43 is controlled based on a target gear ratio and input torque described later. Yes. By supplying such secondary pressure Ps to the secondary pulley 21, the secondary pulley 21 performs a tightening operation so as to suppress slippage of the drive belt 22. In other words, the secondary pressure Ps is adjusted as a clamp pressure for controlling the tension of the drive belt 22 by the secondary pressure control valve 43 that functions as a clamp pressure control valve. The primary pressure Pp supplied to the primary hydraulic fluid chamber 25 is raised by the upshift valve 44 and lowered by the downshift valve 47. The upshift valve 44 and the downshift valve 47 have a target speed ratio. Controlled based on By supplying such a primary pressure Pp to the primary pulley 20, the primary pulley 20 controls the pulley groove width so as to change the winding diameter of the drive belt 22.

  The line pressure control valve 42 and the secondary pressure control valve 43 are pressure reducing valves that set the upper limit pressure of the line pressure PL and the secondary pressure Ps. The upper limit pressure of the line pressure PL and the secondary pressure Ps is the line pressure. Control is performed in accordance with the magnitudes of pilot pressures P1 and P2 supplied to the control valve 42 and the secondary pressure control valve 43. That is, the pilot pressure P1 input from the pilot valve (first pilot valve) 51 to both the line pressure control valve 42 and the secondary pressure control valve 43, or the pilot valve (second pilot valve) 52 to the line pressure control valve 42. It is possible to control the upper limit pressure of the line pressure PL and the secondary pressure Ps by adjusting the pilot pressure P2 input to the pressure.

  Further, the upshift valve 44 and the downshift valve 47 are flow control valves that control the communication state between the ports, and the communication state between the ports is controlled according to the magnitude of the pilot pressure. That is, by adjusting the pilot pressure P3 input from the pilot valve 53 to the upshift valve 44, the communication state between the line pressure path 41b and the primary pressure path 45 can be controlled and supplied to the primary pulley 20. It becomes possible to raise the primary pressure Pp. On the other hand, by adjusting the pilot pressure P4 input from the pilot valve 54 to the downshift valve 47, the communication state between the primary pressure path 45 and the exhaust oil path 55 can be controlled and supplied to the primary pulley 20. The primary pressure Pp can be reduced.

  The pilot valves 52 to 54 that control the line pressure control valve 42, the upshift valve 44, and the downshift valve 47 are duty solenoid valves that regulate the pilot pressures P2 to P4 by controlling the duty ratio with respect to the solenoid. Yes. The pilot valve 51 that controls the line pressure control valve 42 and the secondary pressure control valve 43 is a linear solenoid valve that regulates the pilot pressure P1 by controlling the current value to the solenoid. Further, the pilot valves 52 to 54 are normally closed pilot valves that are shut off when not energized, and the pilot valve 51 is a normally open pilot valve that communicates when not energized.

  The CVT control unit 60 that outputs a control signal to the pilot valves 51 to 54 and executes the shift control of the continuously variable transmission 10 includes a microprocessor (CPU) (not shown). ROM, RAM, and I / O ports are connected via lines. The ROM stores a control program, various map data, and the like, and the RAM temporarily stores data processed by the CPU. Also, detection signals indicating the running state of the vehicle are input from various sensors to the CPU via the I / O port.

  Various sensors for inputting a detection signal to the CVT control unit 60 include a primary rotational speed sensor 61 that detects the rotational speed of the primary pulley 20, a secondary rotational speed sensor 62 that detects the rotational speed of the secondary pulley 21, and the primary pressure path 45. A primary pressure sensor 63 provided to detect the primary pressure Pp, a secondary pressure sensor 64 provided as a clamp pressure sensor provided to the secondary pressure passage 48 to detect the secondary pressure Ps, and an accelerator pedal sensor detecting the accelerator opening of the accelerator pedal. 65, a vehicle speed sensor 66 for detecting the vehicle speed, a throttle opening sensor 67 for detecting the throttle opening of the throttle valve, and an engine speed sensor 68 for detecting the engine speed. An engine control unit 69 is connected to the CVT control unit 60, and the continuously variable transmission 10 and the engine 11 are controlled in cooperation with each other.

  Hereinafter, the shift control of the continuously variable transmission 10 by the CVT control unit 60 will be described. FIG. 3 is a block diagram showing a shift control system of the CVT control unit 60. As shown in FIG. 3, the CVT control unit 60 includes a target primary rotational speed calculation unit 70, a target gear ratio calculation unit 71, a hydraulic ratio calculation unit 72, and a target primary pressure calculation unit 73 in order to calculate the target primary pressure Pp. I have. The target primary rotational speed calculation unit 70 calculates the target primary rotational speed Np by referring to the speed change characteristic map based on the vehicle speed V and the throttle opening degree To, and the target speed ratio calculating unit 71 calculates the target primary rotational speed Np and A target gear ratio i is calculated based on the actual secondary rotational speed Ns ′. Next, the hydraulic ratio calculation unit 72 calculates the hydraulic ratio (Pp / Ps) between the target primary pressure Pp and the target secondary pressure Ps corresponding to the target speed ratio i, and the target primary pressure calculation unit 73 calculates the hydraulic ratio. The target primary pressure Pp is calculated by multiplying the target secondary pressure Ps.

  In addition, the CVT control unit 60 includes an actual speed ratio calculation unit 74, a feedback value calculation unit 75, and an addition unit 76 for feedback control of the target primary pressure Pp. The actual speed ratio calculation unit 74 calculates the actual speed ratio i ′ based on the actual primary rotation speed Np ′ and the actual secondary rotation speed Ns ′, and the feedback value calculation section 75 calculates the actual speed ratio i ′ and the target speed ratio. A feedback value is calculated based on i. Next, the adding unit 76 adds the feedback value to the target primary pressure Pp, and the target primary pressure Pp is feedback-controlled. Then, a control signal is output to the pilot valves 52 to 54 based on the target primary pressure Pp subjected to feedback control, and the primary pulley 20 adjusts the pulley groove width toward the target gear ratio.

  Further, the CVT control unit 60 includes an input torque calculation unit 77, a required secondary pressure calculation unit 78, and a target secondary pressure calculation unit 79 in order to calculate the target secondary pressure Ps. The input torque calculation unit 77 calculates the input torque Ti input from the engine 11 to the primary shaft 12 based on the engine speed Ne and the throttle opening degree To, and the necessary secondary pressure calculation unit 78 calculates the target gear ratio i. Based on the above, the required secondary pressure Psn is calculated. The input torque Ti and the required secondary pressure Psn are input to the target secondary pressure calculation unit 79, and the target secondary pressure calculation unit 79 calculates the target secondary pressure Ps. Then, a control signal is output to the pilot valves 51 and 52 based on the target secondary pressure Ps, and the secondary pulley 21 performs a tightening operation with a tightening force commensurate with the transmission torque.

  FIG. 4 is a diagram showing an example of a speed change characteristic map referred to when the target primary rotation speed Np is calculated. As shown in FIG. 4, a characteristic line Low indicating the maximum transmission ratio (low state) and a characteristic line OD indicating the maximum transmission ratio (overdrive state) are set in the transmission characteristic map, and these characteristic lines Low are set. A plurality of characteristic lines T1 to T8 corresponding to the throttle opening degree To are set between OD and OD. When the throttle opening degree To is low, the target primary rotation speed Np is calculated according to the characteristic line T1, and as the throttle opening degree To increases, the target primary rotation speed Np is calculated according to the characteristic lines T2 to T7. When the throttle opening To is fully opened, the target primary rotational speed Np is calculated according to the characteristic line T8. Further, when the throttle opening To increases in the low vehicle speed range, the target primary rotational speed Np is set along the characteristic line Low, while when the throttle opening To decreases in the high vehicle speed range, the characteristic The target primary rotational speed Np is set along the line OD.

  Hereinafter, a hydraulic control circuit that controls supply of hydraulic oil to the primary pulley 20 and the secondary pulley 21 will be described. FIG. 5 is a circuit diagram showing a part of the hydraulic control circuit, and the same members as those shown in FIG. As shown in FIG. 5, an input port 80 a of a pilot pressure reducing valve 80 is connected to a line pressure path 41 extending from the oil pump 40, and the discharge pressure from the oil pump 40 reaches a predetermined pressure via the pilot pressure reducing valve 80. Be lowered. A distribution oil passage 81 is connected to the output port 80 b of the pilot pressure reducing valve 80, and the hydraulic oil decompressed through the pilot pressure reducing valve 80 is supplied to the pilot valves 51 to 54 via the distribution oil passage 81. A clutch pressure path 82 is connected to the line pressure path 41, and hydraulic oil supplied to the clutch circuit 83 via the clutch pressure path 82 is supplied from the clutch circuit 83 to the forward clutch 35 and the reverse brake 36. To be supplied.

  A line pressure control valve 42 is connected to the line pressure path 41, and hydraulic fluid flowing through the line pressure path 41 is regulated to the line pressure PL via the line pressure control valve 42. The line pressure control valve 42 includes a housing 85 in which a valve accommodating hole is formed and a spool valve shaft 84 that is movably accommodated in the valve accommodating hole. The housing 85 communicates with the line pressure path 41. The pressure adjusting port 42a, the pressure reducing port 42b through which the hydraulic oil is guided from the line pressure passage 41 when the line pressure PL is reduced, and the bypass port 42c for guiding the hydraulic oil toward the bypass valve 90 described later are formed. . Further, in order to move the spool valve shaft 84 in the axial direction, the housing 85 includes a pilot pressure chamber 42d communicating with the line pressure passage 41, a pilot pressure chamber 42e serving as a main control pressure chamber communicating with the pilot pressure passage 86a, a pilot A pilot pressure chamber 42 f is formed as a sub control pressure chamber communicating with the pressure path 87. The spool valve shaft 84 is urged toward the communication position where the pressure regulating port 42a and the pressure reducing port 42b communicate with each other by the line pressure PL supplied to the pilot pressure chamber 42d, while the pilot pressure chambers 42e and 42f By the supplied pilot pressures P1 and P2, the spool valve shaft 84 is urged toward a blocking position that blocks the pressure adjusting port 42a and the pressure reducing port 42b.

  6 (A) and 6 (B) are explanatory views showing the operating state of the line pressure control valve 42, (A) shows a state in which the spool valve shaft 84 is moved to the communication position, and (B) Shows a state in which the spool valve shaft 84 is moved to the shut-off position. As described above, the pilot pressure chamber 42d of the line pressure control valve 42 is supplied with the line pressure PL flowing through the line pressure path 41 as it is, whereas the pilot pressure chambers 42e and 42f of the line pressure control valve 42 are supplied to the pilot pressure chambers 42e and 42f. The pilot pressures P1 and P2 regulated by the pilot valves 51 and 52 are supplied. Therefore, as shown in FIG. 6 (A), the pilot pressure P1, P2 is lowered, and the thrust force that urges the spool valve shaft 84 in the pressure increasing direction by the pilot pressures P1, P2 becomes the spool valve shaft 84 by the line pressure PL. When the thrust for energizing is reduced below the spool valve shaft 84, the spool valve shaft 84 moves toward the communication position. Under such a state, the hydraulic oil flowing in the line pressure path 41 flows out from the pressure reducing port 42b to a lubrication circuit 89 described later, so that the line pressure PL in the line pressure path 41 is reduced. When the line pressure PL is lowered and the thrust for energizing the spool valve shaft 84 in the step-down direction is lowered by the line pressure PL, the spool valve shaft 84 energized by the pilot pressures P1 and P2 is shut off. Since it moves toward the position, the line pressure PL is maintained at the upper limit pressure lowered according to the pilot pressures P1 and P2.

  On the other hand, as shown in FIG. 6B, when the pilot pressures P1 and P2 are increased, the thrust that urges the spool valve shaft 84 in the pressure increasing direction by the pilot pressures P1 and P2 is caused by the line pressure PL. When the thrust that biases the valve in the pressure-decreasing direction is exceeded, the spool valve shaft 84 moves toward the shut-off position. Under such a state, the hydraulic oil flowing in the line pressure path 41 does not flow out from the pressure reducing port 42b, so that the line pressure PL in the line pressure path 41 is increased. When the thrust for energizing the spool valve shaft 84 in the lowering direction is increased by the line pressure PL by increasing the line pressure PL, the spool valve shaft 84 energized by the line pressure PL is directed toward the communication position. Therefore, the line pressure PL is maintained at the upper limit pressure raised according to the pilot pressures P1 and P2.

  As described above, when the pilot pressure P1 output from the pilot valve 51 and the pilot pressure P2 output from the pilot valve 52 are increased, the line pressure PL is adjusted to be high by the line pressure control valve 42, When the pilot pressure P1 or the pilot pressure P2 is lowered, the line pressure PL is adjusted to be low by the line pressure control valve 42. The line pressure PL can be freely set within a predetermined range by controlling the duty ratio of the pilot valve 52 to the solenoid and the current value of the pilot valve 51 with respect to the solenoid.

  When the spool valve shaft 84 is moved to the communication position, the hydraulic oil discharged from the line pressure passage 41 via the pressure reducing port 42b is brought to a predetermined pressure via the lubricating pressure reducing valve 98 as shown in FIG. After the pressure is reduced, the oil is supplied from the lubricating oil passage 88 to the sliding portions such as the drive belt 22 through the lubricating circuit 89. Further, when the spool valve shaft 84 is moved to the shut-off position, the pressure regulating port 42a and the pressure reducing port 42b are shut off, but the bypass valve 90 is connected to the bypass port 42c communicating with the pressure regulating port 42a. Is connected to the lubricating oil passage 88 through the bypass valve 90. The bypass valve 90 is a switching valve that operates between a communication state and a cutoff state by the line pressure PL.

  Further, as shown in FIG. 5, the line pressure PL adjusted via the line pressure control valve 42 is supplied to the secondary pressure control valve 43 via the line pressure path 41 a, and the secondary pressure control valve 43 supplies the secondary pressure. The pressure is adjusted to Ps. The secondary pressure control valve 43 that regulates the secondary pressure Ps includes a housing 91 in which a valve accommodating hole is formed, and a spool valve shaft 92 that is movably accommodated in the valve accommodating hole. An input port 43a to which the pressure path 41a is connected and an output port 43b to which the secondary pressure path 48 is connected are formed. In order to move the spool valve shaft 92 in the axial direction, the housing 91 includes a pilot pressure chamber 43c communicating with the secondary pressure passage 48, and a pilot pressure chamber 43d serving as a main control pressure chamber communicating with the pilot pressure passage 86b. The spring member 93 is incorporated in the pilot pressure chamber 43d.

  That is, the spool valve shaft 92 is urged toward the communication position where the input port 43a and the output port 43b communicate with each other by the secondary pressure Ps supplied to the pilot pressure chamber 43c, while being supplied to the pilot pressure chamber 43d. Due to the pilot pressure P1 and the spring force from the spring member 93, the spool valve shaft 92 is biased toward a blocking position that blocks the input port 43a and the output port 43b. Therefore, by raising the pilot pressure P1, the thrust that urges the spool valve shaft 92 toward the communication position by the pilot pressure P1 and the spring force urges the spool valve shaft 92 toward the shut-off position by the secondary pressure Ps. When the thrust is exceeded, the spool valve shaft 92 moves toward the communication position so as to increase the upper limit pressure, and the secondary pressure Ps is increased so as to approach the line pressure PL. On the other hand, by reducing the pilot pressure P1, the thrust that urges the spool valve shaft 92 toward the communication position by the pilot pressure P1 is less than the thrust that urges the spool valve shaft 92 toward the shut-off position by the secondary pressure Ps. In this case, the spool valve shaft 92 moves toward the cutoff position so as to reduce the upper limit pressure, and the secondary pressure Ps is reduced.

  Here, the pilot pressure passage 86b connected to the secondary pressure control valve 43 and the pilot pressure passage 86a connected to the line pressure control valve 42 are connected to each other, and the line pressure control valve 42 and the secondary pressure control valve are connected to each other. The same pilot pressure P1 is supplied to the pilot pressure chambers 42e and 43d with 43. That is, when a control signal is output from the CVT control unit 60 functioning as pressure control means to the pilot valve 51 and the pilot pressure P1 is increased, both the line pressure PL and the secondary pressure Ps are increased, and the pilot pressure P1 is increased. Is reduced, both the line pressure PL and the secondary pressure Ps are reduced. In addition, when only the pilot pressure P1 is supplied to the line pressure control valve 42 and the secondary pressure control valve 43, the line pressure PL and the secondary pressure Ps substantially coincide with each other.

  Next, the upshift valve 44 and the downshift valve 47 that regulate the primary pressure Pp and control the winding diameter of the drive belt 22 will be described. First, the upshift valve 44 includes a housing 94 in which a valve accommodating hole is formed, and a spool valve shaft 95 that is movably accommodated in the valve accommodating hole. A line pressure passage 41b is connected to the housing 94. The input port 44a and the output port 44b to which the primary pressure path 45 is connected are formed. Further, in order to move the spool valve shaft 95 to a communication position where the input port 44a and the output port 44b communicate with each other and a blocking position where the input port 44a and the output port 44b are blocked, the housing 94 includes a pilot pressure chamber 44c communicating with the pilot pressure path 96, a spring A spring chamber 44d into which the member 97 is incorporated is formed. When the pilot pressure P3 is increased to exceed the predetermined pressure, the spool valve shaft 95 moves to the communication position against the spring force, while when the pilot pressure P3 is decreased to be lower than the predetermined pressure, The spool valve shaft 95 is moved to the blocking position by a spring force.

  Similarly, the downshift valve 47 includes a housing 100 in which a valve accommodating hole is formed, and a spool valve shaft 101 that is movably accommodated in the valve accommodating hole. An input port 47a to be connected and a discharge port 47b to be connected to the downstream fail-safe valve 102 are formed. Further, in order to move the spool valve shaft 101 to a communication position where the input port 47a and the discharge port 47b communicate with each other and a blocking position where the input port 47a and the discharge port 47b are blocked, the housing 100 includes a pilot pressure chamber 47c communicating with the pilot pressure path 103, a spring A spring chamber 47d into which the member 104 is incorporated is formed. When the pilot pressure P4 is increased to exceed the predetermined pressure, the spool valve shaft 101 moves to the communication position against the spring force, while when the pilot pressure P4 is decreased to be lower than the predetermined pressure, The spool valve shaft 101 is moved to the cutoff position by a spring force.

  That is, when the primary pressure Pp is increased to perform the upshift, the pilot pressure P3 for the upshift valve 44 is increased while the pilot pressure P4 for the downshift valve 47 is decreased. Further, when lowering the primary pressure Pp for downshifting, the pilot pressure P3 for the upshift valve 44 is lowered, while the pilot pressure P4 for the downshift valve 47 is raised. In addition, since the communication state between the ports in the upshift valve 44 and the downshift valve 47 can be freely set by controlling the duty ratio of the pilot valves 53 and 54 to the solenoid, the primary pressure Pp is set within a predetermined range. Can be set freely.

  Further, a fail safe valve 102 is provided on the downstream side of the down shift valve 47, and this fail safe valve 102 can avoid a sudden down shift due to a failure of the pilot valve 54. The fail safe valve 102 includes a housing 105 in which a valve accommodating hole is formed, and a spool valve shaft 106 that is movably accommodated in the valve accommodating hole. The housing 105 includes a discharge port 47b of the downshift valve 47. And an exhaust port 102b for guiding hydraulic oil to the oil pan.

  In order to move the spool valve shaft 106 to a communication position where the input port 102a and the discharge port 102b communicate with each other and a blocking position where the input port 102a and the discharge port 102b are blocked, the housing 105 has a pilot pressure chamber 102c communicating with the pilot pressure path 96, a spring A spring chamber 102d into which the member 107 is incorporated is formed. Since the pilot pressure P3 supplied to the upshift valve 44 is input to the pilot pressure chamber 102c, when the spool valve shaft 95 of the upshift valve 44 moves to the communication position, the spool valve shaft of the failsafe valve 102 106 moves to the blocking position. In other words, even when the pilot pressure P4 for the downshift valve 47 increases due to the pilot valve 54 falling into a fail state under the state where the gear ratio is controlled to the overdrive side, the failed fail is blocked. The discharge of hydraulic oil can be avoided via the safe valve 102, and a sudden downshift due to a decrease in the primary pressure Pp can be avoided.

  In addition, a primary pressure reducing valve 108 is incorporated in a primary pressure path 45 that guides the primary pressure Pp toward the primary pulley 20, and an upper limit pressure of the primary pressure Pp is set by the primary pressure reducing valve 108. By providing the primary pressure reducing valve 108, an excessive primary pressure Pp is not supplied to the primary pulley 20, and the primary pulley 20 can be protected.

  Hereinafter, a hydraulic pressure supply state when the gear ratio of the continuously variable transmission 10 is downshifted to the low side and a hydraulic pressure supply state when the gear ratio is upshifted to the overdrive side will be described. FIG. 7 is a circuit diagram illustrating an example of a hydraulic pressure supply state when performing a downshift, and FIG. 8 is a circuit diagram illustrating an example of a hydraulic pressure supply state when performing an upshift.

  As shown in FIG. 7, when the gear ratio is downshifted to the low side, the upper limit pressure of the line pressure control valve 42 and the secondary pressure control valve 43 is increased by increasing the pilot pressure P1 from the pilot valve 51. The line pressure PL and the secondary pressure Ps are both increased. Further, while lowering the pilot pressure P3 from the pilot valve 53 and increasing the pilot pressure P4 from the pilot valve 54, the hydraulic oil is discharged from the primary pulley 20 via the downshift valve 47 that is in a communicating state, and the primary pulley The primary pressure Pp in 20 is reduced. In this way, the primary pressure Pp is lowered to widen the pulley groove width of the primary pulley 20, while the secondary pressure Ps is raised to narrow the pulley groove width of the secondary pulley 21, so that the gear ratio is downshifted to the low side. It has become.

  On the other hand, as shown in FIG. 8, when the gear ratio is upshifted to the overdrive side, the CVT control unit 60 functioning as a differential pressure setting means lowers the pilot pressure P1 from the pilot valve 51 and the pilot valve. By raising the pilot pressure P2 from 52, the line pressure PL is regulated higher than the secondary pressure Ps. That is, in order to reduce the secondary pressure Ps in accordance with the target secondary pressure Ps, when the pilot pressure P1 is reduced, not only the secondary pressure Ps but also the line pressure PL is reduced. By raising P2, it becomes possible to raise only the line pressure PL in accordance with the target primary pressure Pp. In addition, the pilot pressure P3 from the pilot valve 53 is increased while the pilot pressure P4 from the pilot valve 54 is decreased, whereby hydraulic oil is supplied via the upshift valve 44 that is in a communicating state, and the primary oil in the primary pulley 20 is supplied. The pressure Pp is increased. In this manner, the primary pressure Pp is increased to narrow the pulley groove width of the primary pulley 20, while the secondary pressure Ps is decreased to widen the pulley groove width of the secondary pulley 21, whereby the gear ratio is upshifted to the overdrive side. It is like that.

  9A and 9B are diagrams showing changes in the line pressure PL, the primary pressure Pp, and the secondary pressure Ps when shifting from the low state to the overdrive state, and FIG. The pressure change situation by the shift control device (one pressure regulation system) is shown, and (B) shows the pressure change situation by the shift control device of the present invention.

  First, as shown in FIG. 9 (A), in the one-pressure control type shift control apparatus in which the line pressure PL is used as it is as the secondary pressure Ps, the shift is performed from the low state to the overdrive state. At this time, it has been impossible to raise the primary pressure Pp beyond the secondary pressure Ps. That is, since the primary pressure Pp is a pressure that is regulated by reducing the line pressure PL, the primary pressure Pp is the primary pressure in a one-pressure regulating transmission control device in which the line pressure PL and the secondary pressure Ps always match. The upper limit pressure of Pp is equal to the secondary pressure Ps.

  Therefore, when the pressure receiving areas of the hydraulic oil chambers on the primary side and the secondary side are equal, the tightening force of the primary pulley 20 cannot be set exceeding the tightening force of the secondary pulley 21. It is necessary to set larger than the pressure receiving area on the secondary side. Such setting of the pressure receiving area causes an increase in the size of the primary pulley 20, which has been a factor that hinders the size reduction of the continuously variable transmission 10. Further, since it is difficult to increase the tightening force of the primary pulley 20, it has been difficult to improve the shift speed when shifting to the overdrive side.

  On the other hand, in the speed change control device of the present invention, the line pressure PL can be regulated higher than the secondary pressure Ps by increasing the pilot pressure P2 from the pilot valve 52. As shown in FIG. 9B, in a low state where it is desirable to make the secondary pressure Ps higher than the primary pressure Pp, the line pressure PL and the secondary pressure are reduced by reducing the pilot pressure P2 from the pilot valve 52. The pressure Ps can be substantially matched, and the secondary pressure Ps can be set higher than the primary pressure Pp. On the other hand, in an overdrive state where it is desirable to lower the secondary pressure Ps with respect to the primary pressure Pp, the line pressure PL is raised with respect to the secondary pressure Ps by raising the pilot pressure P2 from the pilot valve 52. Therefore, the secondary pressure Ps can be set lower than the primary pressure Pp. That is, by reducing the pilot pressure P1 in accordance with the target secondary pressure Ps, the pilot pressure P2 is increased in accordance with the target primary pressure Pp even when the line pressure PL and the secondary pressure Ps are decreased (symbol x). As a result, only the line pressure PL can be deviated and increased (symbol y).

  Thus, by raising the line pressure PL with respect to the secondary pressure Ps, the primary pressure Pp can be regulated higher than the secondary pressure Ps. It becomes possible to achieve downsizing and to improve the speed of shifting to shorten the speed of shifting. In addition, the line pressure PL can be adjusted so that the line pressure PL is adjusted to the secondary pressure Ps in the low state and the line pressure PL is adjusted to the primary pressure Pp in the overdrive state. It is possible to suppress the fuel consumption of the engine 11 without increasing the load unnecessarily.

  In addition, since the circuit structure is such that the line pressure control valve 42 and the secondary pressure control valve 43 that are mechanically operated are provided, and the two pilot valves 51 and 52 that drive and control these are provided, a high hydraulic control circuit is provided. Costing can be avoided. That is, a conventional speed change control device that freely regulates the secondary pressure Ps and the primary pressure Pp by incorporating three electromagnetic pressure control valves that regulate the line pressure PL, the primary pressure Pp, and the secondary pressure Ps separately. Compared to the (both pressure regulation method), it is possible to greatly reduce development costs and manufacturing costs.

  Further, the pilot pressure P2 is regulated based on the duty ratio for controlling the solenoid of the pilot valve 52, and the amount by which the line pressure PL is increased with respect to the secondary pressure Ps is determined, so that the CVT control unit functions as a pressure estimating means. 60 makes it possible to estimate the line pressure PL based on the secondary pressure Ps from the secondary pressure sensor 64 and the duty ratio of the pilot valve 52. For this reason, the pressure sensor which detects line pressure PL can be reduced, and it becomes possible to achieve further cost reduction.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the illustrated case, the upper limit pressure of the line pressure control valve 42 is increased by the pilot pressure P2 from the pilot valve 52 in order to separate the line pressure PL and the secondary pressure Ps, but this is not limited thereto. The upper limit pressure of the secondary pressure control valve 43 may be reduced. In other words, the pilot pressure chamber of the line pressure control valve 42 is reduced, a pilot pressure chamber as a sub control pressure chamber is formed in the secondary pressure control valve 43, and the pilot pressure is supplied to the pilot pressure chamber, thereby the spool valve shaft. May be biased in the step-down direction.

  Further, the transmission ratio is controlled by adjusting the primary pressure Pp, and the tension of the drive belt 22 is controlled by adjusting the secondary pressure Ps. However, the present invention is not limited to this, and the primary pressure Pp is adjusted. Thus, the transmission ratio may be controlled by controlling the tension of the drive belt 22 and adjusting the secondary pressure Ps.

  Furthermore, a duty solenoid valve is used as a pilot valve, and a linear solenoid valve is used as a pilot valve. However, the present invention is not limited to this. A linear renoid valve is used as a pilot valve, and a duty solenoid valve as a pilot valve. May be adopted. When a linear solenoid valve is employed as the pilot valve, the line pressure PL is estimated based on the secondary pressure Ps and the current value supplied to the solenoid.

  Further, the upshift valve 44 and the downshift valve 47 are flow rate control valves that control the primary pressure Pp by uniquely controlling the flow rate of the hydraulic oil, but the present invention is not limited to this. Alternatively, a flow control valve that controls the pressure of the hydraulic oil may be adopted.

It is a skeleton figure which shows the continuously variable transmission controlled by the transmission control apparatus which is one embodiment of this invention. It is the schematic which shows the hydraulic control system and electronic control system of a continuously variable transmission. It is a block diagram which shows the transmission control system of a CVT control unit. It is a diagram which shows an example of the speed change characteristic map referred when calculating a target primary rotation speed. It is a circuit diagram which shows a part of hydraulic control circuit. (A) And (B) is explanatory drawing which shows the operating state of a line pressure control valve, (A) shows the state which moved the spool valve axis | shaft to the communicating position, (B) is the cutoff position of a spool valve axis | shaft. The state moved to is shown. It is a circuit diagram which shows an example of the hydraulic pressure supply state at the time of performing a downshift. It is a circuit diagram which shows an example of the hydraulic pressure supply state at the time of performing an upshift. (A) And (B) is a diagram which shows the change state of the line pressure at the time of shifting from a low state to an overdrive state, a primary pressure, and a secondary pressure, (A) is a pressure change state by the conventional transmission control apparatus. (B) shows the pressure change situation by the shift control device of the present invention.

Explanation of symbols

10 continuously variable transmission 20 primary pulley (transmission pulley)
21 Secondary pulley (clamping pulley)
22 Drive belt 40 Oil pump (hydraulic supply source)
42 Line pressure control valve (pressure reducing valve)
42e Pilot pressure chamber (main control pressure chamber)
42f Pilot pressure chamber (sub control pressure chamber)
43 Secondary pressure control valve (clamp pressure control valve, pressure reducing valve)
43d Pilot pressure chamber (main control pressure chamber)
51 Pilot valve (first pilot valve)
52 Pilot valve (second pilot valve)
60 CVT control unit (pressure control means, differential pressure setting means, pressure estimation means)
64 Secondary pressure sensor (Clamp pressure sensor)
PL Line pressure Ps Secondary pressure (clamping pressure)

Claims (4)

A continuously variable transmission that includes a transmission pulley and a tightening pulley around which the drive belt is wound, and that controls the winding diameter of the drive belt using the transmission pulley and controls the tension of the precursor drive belt using the tightening pulley. A shift control device for a machine,
A line pressure control valve that regulates hydraulic oil discharged from a hydraulic supply source to a line pressure;
A clamp pressure control valve that is provided between the line pressure control valve and the tightening pulley and adjusts the line pressure to a clamp pressure for the tightening pulley;
A first pilot valve that controls supply of pilot pressure to both main control pressure chambers provided in the line pressure control valve and the clamp pressure control valve;
A second pilot valve for controlling supply of pilot pressure to a sub-control pressure chamber provided in one of the line pressure control valve and the clamp pressure control valve;
Pressure control means for outputting a control signal to the first pilot valve to increase or decrease both the line pressure and the clamp pressure;
A transmission control device for a continuously variable transmission, comprising: a differential pressure setting means for outputting a control signal to the second pilot valve and causing the line pressure and the clamp pressure to deviate from each other.   2. The continuously variable transmission control apparatus according to claim 1, wherein the line pressure control valve and the clamp pressure control valve are pressure reducing valves in which an upper limit pressure is set based on a pilot pressure. A transmission control device for a transmission.   3. The transmission control device for a continuously variable transmission according to claim 1, wherein the sub control pressure chamber is provided in the line pressure control valve, and the line pressure is determined by a clamp pressure based on a control signal from the differential pressure setting means. A transmission control device for a continuously variable transmission, characterized by being highly regulated.   The shift control device for a continuously variable transmission according to any one of claims 1 to 3, wherein a clamp pressure sensor that is provided between the clamp pressure control valve and the tightening pulley and detects a clamp pressure; A transmission control apparatus for a continuously variable transmission, comprising pressure estimation means for estimating a line pressure based on a clamp pressure from the clamp pressure sensor and a control state of the second pilot valve.

Images