Continuously variable transmission hydraulic control device

Abstract

The present application relates to a continuously variable transmission hydraulic control device. Specifically, a continuously variable transmission (CVT) hydraulic control device includes a pressure regulating valve that regulates an operating pressure of oil supplied to a friction element of a forward-reverse device, and a switching valve that switches drain oil paths via which oil supplied to the friction element is drained, by a pilot pressure from the pressure regulating valve and an elastic force of a return spring, respectively. Specifically, the drain oil paths switched by the switching valve have different oil flow resistances from each other.

Description

Technical Field

[0001] This invention relates to a hydraulic control device for a continuously variable transmission (CVT), and more specifically, to a technique for switching the forward and backward movement states of a continuously variable transmission (CVT) using hydraulic pressure. Background Technology

[0002] The statements in this section are provided only as background information in relation to the present invention and do not constitute prior art.

[0003] A continuously variable transmission (CVT) using a drive belt can continuously change the transmission ratio by altering the pulley ratio between the drive pulley and the driven pulley, and uses friction elements such as clutches or brakes, and hydraulic pressure configured to control the rotating elements of the forward-reverse mechanism connected to the drive pulley or driven pulley, to switch between forward and backward movement states.

[0004] We can assume that the forward friction element represents the friction element that enables the forward-reverse mechanism to achieve the forward movement state of the CVT, and the backward friction element represents the friction element that enables the forward-reverse mechanism to achieve the backward movement state of the CVT. Here, if hydraulic pressure is provided, the CVT can be in the forward movement state (D gear) or the backward movement state (R gear) by the hydraulic pressure supplied to the forward or backward friction element. Then, when the CVT is switched to neutral (N) gear, the hydraulic pressure needs to be released from the forward or backward friction element at an appropriate speed.

[0005] If the hydraulic pressure is released too quickly, the torque transmitted to the drive wheels may be released suddenly, causing a shock to the vehicle such as a jerking motion; if the speed is too slow, the vehicle may move even in neutral (N).

[0006] This phenomenon can be greatly affected by changes in oil viscosity, which is based on the temperature of the oil supplied to the forward or backward friction element.

[0007] Content described as prior art is provided only to aid in understanding the background of the invention and should not be considered as corresponding to prior art known to those skilled in the art. Summary of the Invention

[0008] The present invention provides a continuously variable transmission (CVT) hydraulic control device that prevents unnecessary vehicle movement or impact by releasing the hydraulic pressure supplied to the forward or backward friction elements of the CVT at an appropriate speed when the CVT is shifted to neutral (N) gear, regardless of changes in oil viscosity based on temperature.

[0009] According to one embodiment of the present invention, a continuously variable transmission (CVT) hydraulic control device includes: a pressure regulating valve and a switching valve, the pressure regulating valve regulating the operating pressure of oil supplied to the friction elements of the forward-reverse mechanism; the switching valve is configured to switch the discharge path of the oil supplied to the friction elements by means of a pilot pressure from the pressure regulating valve and the spring force of a return spring. Specifically, the discharge paths switched by the switching valve are configured to have different oil flow resistances.

[0010] The pressure regulating valve can be a solenoid valve; the controller that controls the pressure regulating valve can be configured to adjust the pilot pressure supplied to the switching valve based on the temperature of the oil.

[0011] The switching valve may include a first port, a second port, and a third port, with operating pressure from a pressure regulating valve supplied to the first port; the second port is connected to a friction element; and oil discharged from the friction element is discharged through the third port. In one embodiment, the switching valve may be configured to switch between a first state and a second state, in which the second and third ports are connected to each other, and in the second state, the first and second ports are connected to each other.

[0012] In one embodiment, the reset spring is configured to keep the switching valve in a first state, and to switch the switching valve to a second state when the spring force of the reset spring is overcome by a pilot pressure from the pressure regulating valve.

[0013] The controller can be configured to control the pressure regulating valve when the oil temperature is at or above a predetermined reference temperature, so that the pilot pressure switches the switching valve to the second state.

[0014] The drain path formed when the switching valve is in the first state can have less oil flow resistance than the drain path formed when the switching valve is in the second state.

[0015] A switching valve can be installed between the manual valve and the friction element to supply operating pressure from the pressure regulating valve to the friction element via the manual valve operated by the gear shift lever.

[0016] The switching valve can be connected to a manual valve to receive oil discharged from the friction elements via a manual valve operated by the gear shift lever, and then discharge the received oil.

[0017] The friction element of the forward-reverse device can be configured to include a forward friction element that realizes a forward movement state and a backward friction element that realizes a backward movement state; at least one switching valve can be included in at least one of the forward friction element and the backward friction element to switch the oil discharge path.

[0018] Further applicability will become apparent from the description provided herein. It should be understood that this specification and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0019] To better understand the invention, different embodiments thereof will now be described by way of example with reference to the accompanying drawings, in which:

[0020] Figure 1 This is a schematic diagram of a first embodiment of a continuously variable transmission (CVT) hydraulic control device, showing the state of engaging reverse (R) gear;

[0021] Figure 2 It describes conditions under high temperature. Figure 1 A schematic diagram of the implementation scheme switching to neutral (N) gear, thereby discharging oil from the rear towards the friction element;

[0022] Figure 3 It describes the conditions at low temperatures. Figure 1 A schematic diagram of the implementation scheme switching to neutral (N) gear, thereby discharging oil from the rear towards the friction element;

[0023] Figure 4 This is a schematic diagram illustrating a second embodiment of a continuously variable transmission (CVT) hydraulic control device according to another embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram showing a third embodiment of a continuously variable transmission (CVT) hydraulic control device according to an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram illustrating an example of a continuously variable transmission (CVT) that can be applied to the present invention.

[0026] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Detailed Implementation

[0027] The following description is merely exemplary in nature and is not intended to limit the invention, application, or use. It should be understood that in all the drawings, corresponding reference numerals denote the same or corresponding parts and features.

[0028] Hereinafter, a continuously variable transmission (CVT) hydraulic control device according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

[0029] Figure 6The structure of a continuously variable transmission (CVT) applicable to the present invention is shown. This structure can be configured such that when power is input from a power source such as an engine via a torque converter (TC), this power is transmitted to the drive pulley 3 via a forward-reverse mechanism 1 including a planetary gear set (PG); the power transmitted to the drive pulley 3 is transmitted to the driven pulley 7 via a drive belt 5; and then the power is transmitted to the drive wheels via a differential 9.

[0030] The forward-backward device 1 may include a backward friction element (R_FE) capable of fixing the gear ring (R) of the planetary gear assembly (PG) and a forward friction element (F_FE) capable of connecting the sun gear (S) and the planet carrier (C).

[0031] refer to Figures 1 to 5 All embodiments of the present invention can be configured to collectively include: a pressure regulating valve 11 and a switching valve (TV), wherein the pressure regulating valve 11 regulates the operating pressure of the oil supplied to the friction element (FE) of the forward-reverse device 1; and the switching valve (TV) is configured to switch the path through which the oil supplied to the friction element (FE) is discharged by means of a pilot pressure from the pressure regulating valve 11 and the spring force of the return spring 13, respectively.

[0032] Here, the drain paths switched by the switching valve (TV) can be configured to have different oil flow resistances.

[0033] In other words, in this invention, when the CVT is switched to neutral (N) to discharge oil, the hydraulic pressure supplied to the friction element of the forward-reverse device 1, which is used to achieve forward and reverse movement in drive (D) and reverse (R) gears respectively, can be discharged through one of the paths with different flow resistances using a switching valve (TV). In this way, the speed at which hydraulic pressure is released from the friction element can be appropriately adjusted, changing the speed through variations in oil viscosity and the like, thereby preventing unnecessary movement or impacts to the vehicle.

[0034] As described above, the forward-reverse device 1 may include a planetary gear assembly (PG) and a friction element (FE), wherein the planetary gear assembly (PG) is connected to a drive pulley 3 or a driven pulley configured with a conventional CVT; the friction element (FE), such as a brake or clutch, restricts or connects the rotational element of the planetary gear (PG).

[0035] The friction element (FE) can be configured as a forward friction element (F_FE) and a backward friction element (R_FE), wherein the forward friction element (F_FE) is capable of moving forward by hydraulic pressure supplied to it, and the backward friction element (R_FE) is capable of moving backward by hydraulic pressure supplied to it.

[0036] The pressure regulating valve 11 may be a solenoid valve, and the controller (CLR) controlling the pressure regulating valve 11 may be configured to regulate the pilot pressure supplied to the switching valve (TV) based on the temperature of the oil.

[0037] Like conventional CVT hydraulic control units, the pressure regulating valve 11 can be configured to receive line pressure formed by the oil pump and regulating valve, and driven by an electrical signal from the controller (CLR) to regulate and provide appropriate hydraulic pressure to the friction elements.

[0038] When the CVT is switched from neutral (N) to D for forward movement or R for backward movement, the pressure regulating valve 11 can appropriately adjust and supply hydraulic pressure to the forward friction element (F_FE) or the backward friction element (R_FE), thereby enabling a smooth switch without shock.

[0039] For reference, the operating pressure may refer to the hydraulic pressure supplied to the forward friction element (F_FE) or the backward friction element (R_FE) via the pressure regulating valve 11, and the pilot pressure may refer to the hydraulic pressure supplied to the operating switching valve (TV). Figure 1 This shows the situation where both operating pressure and pilot pressure are supplied simultaneously. Figure 2 This shows the case where only pilot pressure is supplied.

[0040] The switching valve (TV) may include: a first port P1, a second port P2, and a third port P3, with operating pressure from the pressure regulating valve 11 supplied to the first port P1; the second port P2 is connected to a friction element; the third port P3 discharges oil discharged from the friction element, and the switching valve may be configured to switch between a first state and a second state, in which the second port P2 and the third port P3 are connected to each other, and in the second state, the first port P1 and the second port P2 are connected to each other.

[0041] The switching valve (TV) can be configured to have a first state by means of the return spring 13, and a second state by means of the spring force of the return spring 13 overcoming the pilot pressure from the pressure regulating valve 11.

[0042] The controller (CLR) can be configured to control the pressure regulating valve 11 when the oil temperature is at or above a predetermined reference temperature, so that the pilot pressure switches the switching valve (TV) to the second state.

[0043] The control unit (CLR) can receive oil temperature information directly from a separate oil temperature sensor, or from another controller, etc. The reference temperature can be set to distinguish whether the vehicle unnecessarily shifts in neutral (N) due to a slower oil discharge rate than normal when oil is discharged from the friction elements. The reference temperature can be determined through experimentation and analysis.

[0044] The drain path formed when the switching valve (TV) is in the first state can have less oil flow resistance than the drain path formed when the switching valve (TV) is in the second state.

[0045] In other words, because the pilot pressure is ineffective due to the oil temperature being below the reference temperature, the discharge path formed when the switching valve (TV) is in the first state has less oil flow resistance than the discharge path formed when the switching valve (TV) is in the second state. Therefore, even with higher viscosity oil, the discharge is smoother. Correspondingly, the friction elements can have the following speeds, formed to be almost identical: the speed at which hydraulic pressure is released when the switching valve (TV) is in the second state at or above the reference temperature; and the speed at which hydraulic pressure is released when the switching valve (TV) is in the first state at a temperature below the reference temperature.

[0046] Therefore, the oil discharge path formed in the second state can be configured to have a level of flow resistance that does not cause impact. This is because, under normal conditions where the oil temperature is at or above the reference temperature, the speed at which hydraulic pressure is released from the friction element is not too fast when the CVT is switched to N gear.

[0047] Here, the magnitude of the flow resistance in the drain path can be achieved by adjusting the minimum flow cross-sectional area of ​​each path. That is, for example, at least a portion of the drain path formed when the switching valve (TV) is in the second state can be implemented to include an orifice with a smaller cross-sectional area than any portion of the drain path formed in the first state or other states.

[0048] The orifice with the above structure can be installed at any location on the drain path formed when the switching valve (TV) is in the second state.

[0049] The above configuration is common to all exemplary embodiments of the present invention. Figures 1 to 3 A first embodiment is shown, wherein a switching valve (TV) is installed between a manual valve (MV) and a friction element to supply operating pressure from a pressure regulating valve 11 to the friction element via the manual valve (MV) operated by a gear shift lever (TL).

[0050] For reference, the manual valve (MV) could further include an option for parking (P gear).

[0051] Furthermore, at least one switching valve (TV) may be included in at least one of the forward friction element (F_FE) and the backward friction element (R_FE) to switch the oil discharge path. Figure 4 A second embodiment is shown, in which a total of two switching valves are provided, including an additional switching valve (TV_A), thereby switching the discharge path of oil discharged from the forward friction element (F_FE) and the backward friction element (R_FE).

[0052] in addition, Figure 5 A third embodiment of the invention is shown, wherein a switching valve (TV) is connected to a manual valve (MV) to receive oil discharged from the friction element via a manual valve operated by a gear shift lever (TL), and then discharge the received oil.

[0053] In the following text, based on Figures 1 to 3 The operation of the invention is described in the first embodiment.

[0054] Figure 1 The manual valve (MV) is shown to be in the R position and the operating pressure of the pressure regulating valve 11 is supplied to the rearward friction element (R_FE), thereby enabling the vehicle to move backward.

[0055] Here, the pilot pressure supplied from the pressure regulating valve 11 to the switching valve (TV) can give the switching valve (TV) a second state, and the hydraulic pressure supplied via the manual valve (MV) can be provided to the backward friction element (R_FE) through the first port P1 and the second port P2.

[0056] When the driver operates the transmission lever (TL) in the rearward movement state described above to shift the manual transmission (MV) to neutral (N), this state can be switched to... Figure 2 The state shown or Figure 3 The state shown.

[0057] In other words, when the oil temperature is at or above the reference temperature, the controller (CLR) can drive the pressure regulating valve 11, so that the pilot pressure can continuously maintain the switching valve (TV). Figure 2 The second state is shown. When the oil temperature is below the reference temperature, the pilot pressure is not provided or is only provided to a level where the pilot pressure cannot overcome the spring force of the return spring 13, thus causing the switching valve (TV) to have the following characteristics: Figure 3 The first state is shown.

[0058] The oil discharge path through which the oil exits the rearward friction element (R_FE) and is formed when the switching valve (TV) is in the first state has less flow resistance than the oil discharge path formed when the switching valve (TV) is in the second state. Therefore, the oil in the rearward friction element (R_FE) can be smoothly discharged even under lower temperature conditions with higher oil viscosity, thereby effectively preventing unnecessary vehicle movement in neutral (N) gear.

[0059] This invention can prevent unnecessary vehicle movement or impact when the CVT is switched to neutral (N) by releasing the hydraulic pressure supplied to the forward or backward friction element of the continuously variable transmission (CVT) at an appropriate speed, regardless of changes in oil viscosity based on oil temperature, and can achieve this function at a very low cost.

[0060] Although the invention has been shown and described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various modifications and alterations can be made to the invention without departing from its spirit.

Claims

1. A continuously variable transmission (CVT) hydraulic control device, comprising: A pressure regulating valve configured to regulate the operating pressure of the oil supplied to the friction elements of the forward-reverse mechanism; and A switching valve is configured to switch the oil discharge path separately by a pilot pressure from the same pressure regulating valve and the spring force of a return spring; in: The oil supplied to the friction elements is discharged through the oil drain path; The oil discharge paths switched by the switching valve are configured to have different oil flow resistances; in: The pressure regulating valve is a solenoid valve; The controller is configured to control the same pressure regulating valve and adjust the pilot pressure supplied to the switching valve based on the oil temperature. The switching valve is installed between the manual valve and the friction element, and is configured to supply operating pressure from the same pressure regulating valve to the friction element via the manual valve operated by the gear shift lever; The switching valve is connected to a manual valve and is configured to receive oil discharged from the friction element via a manual valve operated by a transmission lever, and then discharge the received oil.

2. The continuously variable transmission hydraulic control device according to claim 1, wherein, The switching valve includes: The first port is supplied with operating pressure from the pressure regulating valve. The second port is connected to the friction element; and The oil discharged from the friction element is discharged through the third port; The switching valve is configured to switch between a first state and a second state. In the first state, the second port and the third port are connected to each other, and in the second state, the first port and the second port are connected to each other.

3. The continuously variable transmission hydraulic control device according to claim 2, wherein: The reset spring is configured to put the switching valve in a first state; When the pilot pressure from the pressure regulating valve overcomes the spring force of the reset spring, the switching valve is switched to the second state.

4. The continuously variable transmission hydraulic control device according to claim 3, wherein, When the oil temperature is equal to or higher than a predetermined reference temperature, the controller is configured to control the pressure regulating valve so that the pilot pressure switches the switching valve to the second state.

5. The continuously variable transmission hydraulic control device according to claim 4, wherein, The first drain path formed when the switching valve is in the first state has less oil flow resistance than the second drain path formed when the switching valve is in the second state.

6. The continuously variable transmission hydraulic control device according to claim 1, wherein, The friction elements of the forward-backward device include: a forward friction element that realizes a forward movement state and a backward friction element that realizes a backward movement state; At least one switching valve is included in at least one of a forward friction element and a backward friction element, and is configured to switch the oil discharge path.

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