JPH0792146B2 - Hydraulic control device for automatic transmission - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic control device for an automatic transmission, and more particularly,
The present invention relates to a hydraulic pressure control device having a function of setting the hydraulic fluid pressure of the friction element to the maximum pressure when the hydraulic fluid of the friction element is at a predetermined temperature or lower.

2. Description of the Related Art As a conventional automatic transmission, for example, JP-A-62-62047 is known.
As disclosed in Japanese Unexamined Patent Publication No. 2005-163242, various combinations of planetary gear sets (sun gear, pinion carrier, internal gear) can be obtained by changing the combined combination of the components (sun gear, pinion carrier, internal gear) via a plurality of friction elements. It is designed to be used.

As the friction element, for example, a clutch, a brake, or the like is used, and engagement or release is performed by a line pressure (operating hydraulic pressure) supplied from a control valve (hydraulic pressure control circuit).

By the way, the line pressure is changed according to the driving condition of the vehicle, that is, the engine load (throttle opening) in order to prevent the engagement shock of the friction element. When the engine speed is low, the line pressure is low and the engine speed is low. When is high, the line pressure is set to be high.

However, when the temperature of the hydraulic fluid is extremely low, for example,
At −10 ° C. or lower, the viscosity of the hydraulic fluid is significantly increased, and the viscous resistance at that time reduces the flow rate of the hydraulic fluid, causing a delay in the operation of the friction element.

Therefore, there has been a conventional one in which the friction element is smoothly operated by always setting the line pressure to the maximum pressure regardless of the engine load at the low temperature.
1987 NISSAN maintenance manual: RE4R01A type).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a conventional hydraulic control device for an automatic transmission, by setting the line pressure to the maximum pressure at a low temperature, smooth operation of the friction element may not be possible. However, when the viscosity of the hydraulic fluid is high as described above, the viscous resistance is remarkably large, so that the load of the hydraulic pump for generating the line pressure is also large. In addition to the heavy load of
Further, as described above, in order to maximize the pressure of the hydraulic fluid,
A significant increase in pump load will result.

Further, since the hydraulic pump is normally driven by the engine, a large load is also applied to the engine.

Therefore, there is a problem that the engine startability is significantly deteriorated when the maximum control of the line pressure causes a significant load increase even at such a low temperature.

Therefore, it is an object of the present invention to provide a hydraulic pressure control device for an automatic transmission, which enables a friction element to operate smoothly at a low temperature and at the same time reduces a load in a low rotation region of an engine as much as possible. .

Means for Solving the Problems In order to achieve the above object, the present invention includes a hydraulically operated friction element a for switching a transmission gear, as shown in FIG. In a hydraulic pressure control device for an automatic transmission, which is provided with a low temperature hydraulic pressure control means b for setting the hydraulic pressure of the friction element a to the maximum pressure when the hydraulic fluid has a high temperature and a low temperature, Engine speed detecting means c for detecting
And a prohibiting means d for prohibiting the hydraulic pressure control by the low temperature hydraulic pressure control device b when the hydraulic fluid is at a low temperature and the engine rotational speed is in a low rotational speed region below the idling rotational speed.
And are provided.

With the above configuration, in the hydraulic control device for an automatic transmission according to the present invention, even when the hydraulic fluid of the friction element is in a low temperature state, when the engine is in a low rotation region below the idling speed, By prohibiting the hydraulic pressure control by the hydraulic pressure control device b, the hydraulic fluid is set to a low pressure according to the normal engine load.

Therefore, the viscous resistance of the hydraulic fluid whose viscosity is high in the low temperature state can be minimized by reducing the pressure, and the load acting on the engine can be reduced accordingly.

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

That is, FIG. 2 is a schematic view of a shift control device for an automatic transmission showing one embodiment of the present invention, in which 10 is a control unit as a hydraulic pressure control device, which is controlled by a control signal output from the control unit 10. The gear shift of the automatic transmission 1 is performed.

The automatic transmission 1 is constituted by, for example, a power train shown in FIG. 3, is coupled to an engine 3 via a torque converter 2, and rotation of the engine 3 is performed via the torque converter 2 and the automatic transmission 1. It is output to the outside drive wheel side.

By the way, the power train of the automatic transmission 1 includes a front planetary gear set 12 including a front sun gear 12s, a front pinion gear 12p, a front internal gear 12i, and a front planet carrier 12c, a rear sun gear 14s, a rear pinion gear 14p, and a rear internal gear. 14i, a rear planetary gear set 14 including a rear apnet carrier 14c, and these two planetary gear sets 12 and 14 are arranged in tandem.

Further, as shown in the power train, a reverse clutch R / C connecting the input shaft 16 and the front sun gear 12s, a high clutch H / C connecting the input shaft 22 and the front planet carrier 12c,
A forward clutch F / C that connects the front planet carrier 12c and the rear internal gear 14i, and a brake band B / that fixes the front sun gear 12s to the housing side.
B, friction elements such as a low and reverse brake L & R / B for fixing the front planet carrier 12c to the housing side are provided.

Further, a forward one-way clutch F / O / C is provided between the forward clutch F / C and the rear internal gear 14i.
Front planet carrier 12c
Rowan way clutch L / O ・ C between the housing and the housing
And the overrun clutch O / R / C is arranged in parallel with the forward one-way clutch F / O / C between the front planet carrier 12c and the rear internal gear 14i.

By the way, in the power train having such a configuration, as shown in Table 1 below, various gears are obtained by engaging and releasing various friction elements by the line pressure supplied from the hydraulic pressure control circuit described later. It is like this.

In the table, a circle mark indicates a fastened state, and a blank mark indicates a released state.

In addition, the above forward one-way clutch F / O / C is
The rear internal gear 14i is free to rotate in the forward rotation direction with respect to the front planet carrier 12c, is locked in the rotation in the reverse rotation direction, and the low one-way clutch L / O / C is rotated in the forward rotation direction of the front planet carrier 12c. Sometimes free, locked when rotating in the reverse direction.

By the way, although the above overrun clutch O / R / C is not shown in Table 1, the overrun clutch O / R / C is not shown.
By engaging the engine, the function of the forward one-way clutch F / O / C is lost and the engine brake is activated.

FIG. 4 shows a hydraulic pressure control circuit for controlling the hydraulic pressure supplied to each of the friction elements, and the friction element is engaged or released by the control hydraulic pressure supplied from the hydraulic pressure control circuit.

That is, in the hydraulic control circuit, the pressure regulator valve 20, the pressure modifier valve 22, the line pressure solenoid 24, the pilot valve 26, the torque converter regulator valve 28, the lockup control valve 30, the shuttle valve 32,
Lockup solenoid 34, manual valve 36, first shift valve 38, second shift valve 40, first shift solenoid 42, second shift solenoid 44, forward clutch control valve 4
6,3-2 Timing valve 48,4-2 Relay valve 50,4-2 Sequence valve 52, I range pressure reducing valve 54, Shuttle valve 56, Overrun clutch control valve 58, Third shift solenoid 60, Overrun clutch pressure reducing Valve 62, 2nd speed servo apply pressure accumulator 64, 3rd speed servo release pressure accumulator 66,4
A fast servo apply pressure accumulator 68 and an accumulator control valve 70 are provided.

And, each component of the hydraulic control circuit has the relationship shown in the figure, the reverse clutch R / C, the high clutch H / C,
Forward clutch F / C, brake band B / B, low and reverse brake L & R / B, overrun clutch ORR /
Connected to each friction element of C and oil pump O / P,
By the switching combination of the shift valve 38 and the second shift valve 40, the hydraulic pressure is supplied to and stopped from each friction element, and the line pressure as the engagement pressure supplied to each friction element is controlled.

The detailed configuration and function of each component of the hydraulic pressure control circuit are the same as those described in JP-A-62-62047, and detailed description thereof will be omitted.

Incidentally, the band brake B / B is operated by the band servo B / S, and the band servo B / S is the second speed servo apply pressure chamber 2S / A, the third speed servo release pressure chamber 3S / R and the fourth speed servo apply. Comprised of pressure chamber 4S / A, 2nd speed servo apply pressure chamber 2S
By supplying hydraulic pressure to / A, the bunt brake B / B is engaged, and in this state, hydraulic pressure is supplied to the third speed servo release pressure chamber 3S / R, which releases the bunt brake B / B. Further, in this state, hydraulic pressure is supplied to the fourth speed servo apply pressure chamber 4S / A so that the bunt brake B / B is engaged.

By the way, the switching of the first and second shift valves 38, 40 is
This is performed by turning on and off the first and second shift solenoids 42 and 44, and at the time of turning on, pilot pressure is supplied to these first and second shift valves 38 and 40 to the right half position (upper position) in the figure,
And when it is off, the pilot pressure is drained and the first and second
The shift valves 38, 40 are in the left half position (lower position) in the figure,
As shown in Table 2 below, each shift speed can be obtained by performing ON / OFF switching.

The switching signals for the first and second shift valves 38, 40 are output from the control unit 10 shown in FIG. 2, and for example, the vehicle speed and throttle opening as shown in FIG. The shift control is performed according to the shift schedule determined by

Further, in the hydraulic control circuit, the discharge pressure of the oil pump O / P driven by the engine is regulated as a line pressure by the pressure regulator valve 20, and the line pressure is supplied to each friction element as a fastening pressure. It has become so.

The pressure regulator valve 20 works as a force that the discharge pressure of the oil pump O / P acting on the pressure receiving surface 20d acts on the pressure receiving surface 20d as shown in FIG.
Circuit 20 and the urging force of the spring 20a that is contracted between
The modifier pressure acting on the lower end of the plug 20c via 6 acts as forces acting upward in the figure, and the spool 20b is moved to a position where these forces are balanced, and the port 20e
The line pressure is adjusted to.

The modifier pressure is generated by the pressure modifier valve 22. The pressure modifier valve 22 is controlled by the signal pressure supplied from the line pressure solenoid 24.

The line pressure solenoid 24 is an on-drain type solenoid valve, and by controlling the duty of the line pressure solenoid 24, the pilot pressure output from the pilot valve 26 is pressure-controlled, and the control pressure is used as a signal pressure. Supply to the pressure modifier valve 22.

Therefore, by controlling the signal pressure by the line pressure solenoid 24, the modifier pressure can be changed, and the line pressure can be controlled by the pressure regulator valve 20.

By the way, the line pressure solenoid 24 is driven by a control signal output from the line pressure solenoid control means 80 incorporated in the control unit 10 shown in FIG. 2, and is usually controlled as a signal pressure corresponding to the accelerator opening. To be done.

Further, the line pressure solenoid control means 80 has a built-in low temperature hydraulic pressure control means 82, and the working fluid temperature detected by a liquid temperature detection means 86 described later is a constant temperature set in advance (for example, −10 ° C.). In the following cases, a control signal for maximizing the line pressure is output to the line pressure solenoid 24, and the maximum constant pressure is set irrespective of the accelerator opening as indicated by the characteristic line shown by the solid line in FIG.

The characteristic line indicated by the broken line in the figure is the line pressure characteristic at room temperature.

Here, in this embodiment, the control unit 10 includes a liquid temperature detecting means 86 for detecting the temperature of the working fluid from the detection signal of the liquid temperature sensor 84, and an engine for detecting the engine speed from the detection signal of the engine rotation sensor 88. Rotation speed detection means 90,
A shift range detection means 94 for detecting a range position selected from the detection signal of the inhibitor switch 92 is provided, and the detection signals of these detection means 86, 90, 94 are output to the line pressure solenoid control means 80. Has become.

Further, the line pressure control means 80 has a prohibition means 96 for prohibiting the control by the low temperature hydraulic pressure control means 82 under a certain condition.
Is provided.

FIG. 7 shows a flowchart of the control performed by the control unit 10. First, in step I, the shift signal from the inhibitor switch 92 is changed to shift range detecting means.
94, the liquid temperature signal from the liquid temperature sensor 84 is input to the liquid temperature detecting means 86 in step II, and the engine speed signal from the engine speed sensor 88 is input to the engine speed detecting means 90 in step III.

Then, in the next step IV, it is judged whether or not it is in the power non-transmission range of the P range or the N range.
If IV is "YES", the process proceeds to step V and it is determined whether the liquid temperature is below a certain temperature.

If it is determined to be "YES" in step V, the process proceeds to step VI, and it is determined whether the engine speed is equal to or lower than a predetermined number of revolutions. If "YES", the process proceeds to step VII, and the prohibiting means 96 is used. The control by the low temperature hydraulic pressure control means 82 is prohibited.

Therefore, by prohibiting the control by the low temperature hydraulic pressure control means 80 in this way, the control is performed according to the line pressure characteristic at room temperature as shown by the broken line in FIG. , The line pressure is set to a low level when the accelerator opening is small.

Further, the predetermined engine speed, which serves as the determination criterion in step VI, is set to the engine speed at engine start.

If it is determined to be "NO" in step IV, step V, or step VI, proceed to step VIII,
The prohibiting means 96 is not activated, and the low temperature hydraulic pressure control means 82
Normal control including control of is performed.

In the hydraulic pressure control device of the present embodiment having the above configuration,
When the hydraulic fluid of the friction element is below a preset constant temperature, the prohibiting means is provided at the time of starting at low engine speed.
Since 96 is operated and the control of the low temperature hydraulic pressure control means 82 is prohibited, the line pressure controlled by the pressure regulator valve 20 is adjusted to a low pressure according to the accelerator opening.

FIG. 8 shows the output from the line pressure solenoid control means 80 to the line pressure solenoid 24 when the above line pressure control is performed.
ON, the duty ratio characteristic A of the OFF signal, the speed transition characteristic B of the engine, showed the liquid temperature variation characteristic C of the hydraulic fluid, a constant temperature T _F following the speed transition characteristic B of the liquid temperature change characteristic C When both conditions below the predetermined rotation speed N _E are satisfied, the ON ratio of the duty ratio is increased.

That is, in the duty ratio characteristic A, the ON ratio is increased, so that the drain amount of the pilot pressure is increased and the signal pressure supplied to the pressure modifier valve 22 is decreased, and as a result, the pressure regulator valve 20 adjusts the signal pressure. The line pressure applied can be reduced.

Therefore, the oil pump O / P that discharges the hydraulic fluid whose viscous resistance is large due to the low temperature does not need to discharge the high-pressure hydraulic fluid, so the load acting on the oil pump O / P, The load acting on the engine can be significantly reduced, and the startability of the engine is improved.

By the way, in the above-mentioned embodiment, the case where the predetermined number of revolutions of the engine on which the prohibiting means 96 is operated is set to the number of revolutions at the time of starting has been described. It is possible to prevent the engine load from being reduced due to the reduction of the engine load even in the idling.

EFFECTS OF THE INVENTION As described above, in the hydraulic control device for an automatic transmission according to the present invention, the working fluid of the friction element is in a low temperature state accompanied by its high viscosity, and the engine speed is When the engine speed is in the low speed range below the idling speed, the hydraulic pressure control by the low temperature hydraulic pressure control means is prohibited by the prohibiting means, so the working hydraulic pressure in this case is set to a normal low pressure and the load acting on the engine is reduced. Can be significantly reduced.

Therefore, there is an excellent effect that the engine can be smoothly operated in a low rotation region such as engine start even at a low temperature.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing the concept of the present invention, FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 3 is a schematic configuration showing a power train of an automatic transmission to which the present invention is applied. Figure,
FIG. 4 is a schematic configuration diagram showing a hydraulic pressure control circuit of an automatic transmission to which the present invention is applied, FIG. 5 is an explanatory diagram showing an example of a shift schedule used in the present invention, and FIG. Fig. 7 is a characteristic diagram of the line pressure at low temperature and the line pressure at room temperature when the hydraulic control means is operated, Fig. 7 is a flow chart showing one processing example for executing the control according to the present invention, and Fig. 8 is the present invention. It is a characteristic view which shows the control signal of the hydraulic fluid controlled, an engine speed, and the relationship of hydraulic fluid temperature. 1 ... Automatic transmission, 2 ... Torque converter, 3 ... Engine, 10 ... Control unit (hydraulic pressure control device), 20 ... Pressure regulator valve, 24 ... Line pressure solenoid, 80 ... Line Pressure solenoid control means,
82 …… Liquid pressure control means at low temperature, 84 …… Liquid temperature sensor, 86 ……
Liquid temperature detecting means, 88 ... Engine speed sensor, 90 ... Engine speed detecting means, 94 ... Shift range detecting means, 96
…… Prohibition means, H / C …… High clutch (friction element), F / C
…… Forward clutch (friction element), B / B …… Brake band (friction element), L & R / B …… Low and reverse brake (friction element), ORR / C …… Overrun clutch (friction element).

Claims (1)

[Claims] 1. A hydraulic pressure-operated friction element for switching transmission gears is provided, wherein the hydraulic fluid pressure of the frictional element is maximized when the hydraulic fluid has a high viscosity accompanied by an increase in viscosity of the hydraulic fluid. A hydraulic pressure control device for an automatic transmission, which is provided with a low temperature hydraulic pressure control means for setting a high pressure, an engine rotational speed detection means for detecting an engine rotational speed, and an engine rotational speed when the hydraulic fluid is at a low temperature. A hydraulic pressure control device for an automatic transmission, comprising: prohibiting means for prohibiting the hydraulic pressure control by the low temperature hydraulic pressure control means when the engine speed is in a low rotational speed range equal to or lower than the idling rotational speed.