JP3191378B2 - Slip limit start shock reduction device for fluid transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for limiting a slip of a fluid transmission device inserted into a transmission system or the like of an automatic transmission, and more particularly to a device for reducing a shock at the start of a slip limit.

[0002]

2. Description of the Related Art An automatic transmission has a fluid transmission device such as a torque converter in a transmission system for the purpose of increasing torque and absorbing torque fluctuation. The torque converter includes an input element driven by the engine and an output element opposed to the input element. The output element is driven by an internal working fluid stirred by the input element to transmit power between the input and output shafts. And a predetermined torque increasing function or a torque fluctuation absorbing function can be achieved.

[0003] However, in a fluid transmission device represented by a torque converter, relative rotation (slip) cannot be avoided between input and output elements, and power transmission efficiency is poor. Therefore, under an engine operating state that does not require a large torque increasing function or a torque fluctuation absorbing function, or an engine operating state that hardly requires a torque increasing function or a torque fluctuation absorbing function,
A torque converter having a lock-up clutch for limiting the above-mentioned slip depending on an operation state tends to be frequently used in an automatic transmission.

Conventionally, in controlling the slip limit, an automatic transmission of the type described in "RE4R01A type automatic transmission maintenance manual" issued by the applicant of the present invention in March 1987, for example, is actually used on an actual vehicle. As shown in FIG. 5B, the lock-up clutch engagement pressure Pb is so-called from the instant t ₁ when the slip limit command is issued to the engagement start instant t ₂ of the lock-up clutch. The time series is changed so as to gradually increase by the feedforward control, and then the lock-up clutch coupling pressure Pb is feedback-controlled according to the deviation between the target slip amount set for each operating state and the actual slip amount 運 転 N, and the actual slip amount △ There is a slip limit control device that brings N to the target slip amount.

[0005]

However, in such a conventional slip limit control device, generally, the lockup clutch engagement pressure Pb and the torque converter slip amount △ N
Is shown in FIG. 6 by a dashed line.
The following problems occurred.

Namely, the lock-up clutch is to initiate the contact when the coupling pressure of P ₀ (clutch plate starts to contact), in theory, as shown by the solid line in FIG. 6, from the time the bond starts The clutch coupling force increases in proportion to the increase of the lock-up clutch coupling pressure, and the torque converter slip amount ΔN should decrease with the same proportional tendency. Actually, as indicated by the dashed line, the lock-up clutch has the engagement pressure P which is higher than P ₀ by ΔP.
If it does not become ₀ + ΔP, a coupling force cannot be generated (coupling starts), and when the coupling force starts to be generated, the torque converter slip amount is suddenly reduced by ΔNh, and the theoretical characteristic shown by the solid line is obtained. It suddenly increases so as to exhibit a hysteresis characteristic such as matching.

By the way, as in the prior art shown in FIG. 5 (b), immediately after the lock-up clutch engagement start instant t ₂ , the lock-up clutch engagement pressure Pb is changed to the actual slip amount ΔN of the torque converter and the target slip amount. If the feedback control is performed in accordance with the deviation, the large slip amount deviation (△ in FIG. 6) is also obtained immediately after the instant t _{2 in} FIG.
Nh), control is performed to increase the lock-up clutch coupling pressure Pb in order to eliminate the deviation ΔNh. On the other hand, as apparent from processing described above, the binding pressure Pb of the lock-up clutch (P ₀ + △ P) binding force of the lock-up clutch for binding initial instant t ₂ of the lock-up clutch becomes becomes suddenly large Nevertheless, in the related art, the lock-up clutch engagement pressure Pb continues to rise as described above immediately after the lock-up clutch engagement start instant t _{2, and the} clutch engagement pressure Pb rises immediately after the instant t _{2 and the} instant t _{2 2,} due to the synergistic effect of the sudden increase in the lock-up clutch coupling force, as shown in FIG.
So it can be appreciated from the rapid decrease immediately after the lock-up clutch coupling initial instant t _2, causing instability of control with a shock immediately after the start of the slip limiting torque converter increases.

According to the present invention, the lock-up clutch engagement pressure is maintained at a pressure near the lock-up clutch engagement instant value without feedback control of the lock-up clutch engagement pressure for a while after the lock-up clutch engagement start. An object is to solve the above-mentioned problem.

[0009]

SUMMARY OF THE INVENTION To this end, a slip limiting onset shock mitigation system for a fluid transmission according to the present invention, as shown in FIG. Power is transmitted to an output element, and is used in a fluid transmission device capable of limiting a slip between the input and output elements by an appropriate connection of a lock-up clutch. Until the lock-up clutch engagement start detecting means detects the start of engagement of the up-clutch, the lock-up clutch engagement pressure is gradually increased, and then the lock-up clutch engagement pressure is fed back according to the deviation between the target slip amount and the actual slip amount. In the slip limit control device for a fluid transmission device, the lock-up clutch engagement is controlled. Timer means for measuring an elapsed time after the start of engagement of the lock-up clutch is detected by the start detection means, and until the elapsed time reaches a set time, the feedback control is inhibited to reduce the lock-up clutch engagement pressure. A feedback control delay means for keeping the value close to the value at the start of lock-up clutch engagement is provided.

[0010]

The input element stirs the internal working fluid, and the working fluid fluidly drives the output element, so that the fluid transmission transmits power from the input element to the output element. During this time, when the slip limit command means commands the slip limit, the slip limit control device controls the lock-up clutch coupling pressure from the instant of the command until the lock-up clutch coupling start detecting means detects the start of coupling of the lock-up clutch. The feedback control delay means inhibits the feedback control and locks up the lock-up clutch coupling pressure until the timing means for measuring the elapsed time from the start of engagement of the lock-up clutch measures the elapse of the set time. Keep the pressure near the value at the start of clutch engagement,
Thereafter, the slip limit control device performs feedback control of the lock-up clutch engagement pressure in accordance with the deviation between the target slip amount and the actual slip amount of the fluid transmission. The lock-up clutch is engaged in response to the engagement pressure set as described above, and thereby controls the slip of the fluid transmission to a corresponding slip amount.

According to the present invention, the lock-up clutch engagement pressure is not immediately feedback-controlled immediately after the start of engagement of the lock-up clutch, and the lock-up clutch engagement pressure is set to a value close to the value at the start of the engagement for a set time from the start of the engagement. The feedback control amount corresponding to the difference between the actual slip amount of the torque converter and the target slip amount is not added to the lock-up clutch engagement pressure during the set time from the start of the engagement, Therefore, the lock-up clutch engagement pressure does not continue to increase immediately after the start of engagement of the lock-up clutch. Conventionally, since the lock-up clutch engagement pressure is continuously increased by feedback control as described above immediately after the start of engagement of the lock-up clutch, a synergistic effect of the hysteresis characteristic peculiar to the lock-up clutch and the coupling force change characteristic referred to as the lock-up clutch characteristic. However, according to the present invention, the feedback control of the lock-up clutch coupling pressure during the set time from the start of coupling of the lock-up clutch is performed according to the present invention. Since the lock-up clutch engagement pressure is maintained at a pressure near the value at the start of the engagement without performing the above, it is possible to eliminate the occurrence of a large shock and the instability of control due to the sudden decrease in the torque converter slip amount.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows an embodiment of a slip limiting start shock reducing device according to the present invention, wherein reference numeral 1 denotes a torque converter as a fluid transmission device whose slip is to be limited, which is to be controlled.
The torque converter 1 transmits the rotational power from the engine 2 to the gear transmission mechanism 3 of the automatic transmission, and performs a predetermined torque increasing function and a torque fluctuation absorbing function during this time. The main components are a pump impeller 1a and a turbine runner 1b as an output element which is drivingly coupled to an input shaft of the gear transmission mechanism 3. As is well known, such a torque converter 1 is driven by a pump impeller 1a by an engine, and the turbine runner 1b is fluidly driven by an internal working fluid stirred by the pump impeller 1a to transfer engine power to a gear transmission mechanism 3 under a torque increasing function and a torque fluctuation absorbing function. Shall be communicated.

Further, the torque converter 1 includes a lock-up clutch 4 which is drivingly connected to the turbine runner 1b so as to be axially displaceable. The lock-up clutch 4 has a leftward stroke in the drawing via a clutch facing 4a and a pump impeller 1a. , The slip between the pump impeller 1a and the turbine runner 1b is limited according to the frictional engagement strength. Therefore, the torque converter 1 has a converter (CV) state in which the slip is not limited at all, a lock-up (LU) state in which the slip is zero, and a slip control (SL) intermediate between the two.
Power transmission can be performed in three modes, namely, the state.

Next, a hydraulic circuit for controlling these three modes will be described. The working fluid of the torque converter 1 is supplied from one of the circuits 5 and 6 and drained from the other. When the fluid is supplied from the circuit 5 and drained from the circuit 6, the torque converter 1 is in a converter (CV) state, When the torque is supplied from the circuit 6 and drained from the circuit 5, the torque converter 1 locks up (L
U) or slip control (SL).

The supply direction of these working fluids and the pressure regulation of the circuit 6 are controlled by a lock-up control valve 7, which is urged toward the illustrated position by the pressure of a spring 8 and a chamber 9, and the chambers 10, 11 Is urged in the opposite direction via the plug 12 by the pressure of
The pressure in the chamber 9 is regulated by the lock-up solenoid 15 using the pilot pressure Pp from the pressure source 13 to the circuit 14 as an original pressure, and the pressure in the circuit 5 is derived as the pressure in the chamber 10. Is the pilot pressure Pp
Lead.

The duty of the lock-up solenoid 15 is controlled by the controller 16. At a duty of 0%, the pressure of the chamber 9 is set to the same maximum value as the pilot pressure Pp, and the pressure of the chamber 9 is increased from the drain port 15a in accordance with an increase in the duty. The pressure in the chamber 9 is gradually reduced by draining.

When the pressure in the chamber 9 is set to the maximum value at the duty of the solenoid 15 of 0%, the lock-up control valve 7 is set to the position shown in FIG. At this time, the working fluid having the converter pressure Pc from the pressure source 13 to the circuit 17 is supplied from the circuit 5 to the torque converter 1 and is removed from the circuit 6 through the drain circuit 18, thereby turning the torque converter 1 into a converter (CV) state. To When the pressure in the chamber 9 is 0 due to the duty of the solenoid 15 being 100%, the lock-up control valve 7
Is stroked to the rightmost limit position in the figure by the pressure of the chambers 10 and 11 at first and then by the pressure of the chamber 11. At this time, the working fluid having the converter pressure Pc from the pressure source 13 to the circuit 17 is supplied from the circuit 6 to the torque converter 1 and is removed from the circuit 5 through the drain port 19 to lock up the torque converter 1 (LU). State.

The duty of the solenoid 15 is set to 0
When the pressure of the chamber 9 is set to a pressure corresponding to the duty value within a range of 100% to 100%, the lock-up control valve 7 changes the pressure of the circuit 6 which strokes between the two limit positions toward the torque converter 1 according to the duty value. Value,
The torque converter 1 is brought into a slip control (SL) state such that the slip corresponds to the duty value.

The controller 16 which controls the duty of the lock-up solenoid 15 includes a signal from a throttle opening sensor 21 for detecting an engine throttle opening TVO and an engine speed for detecting an engine speed Ne (torque converter input speed). A signal from the sensor 22;
A signal from a turbine rotation sensor 23 for detecting the output speed Nt of the torque converter, a signal from a gear position sensor 24 for detecting the selected shift stage Gp of the gear transmission mechanism 3, and a signal from a vehicle speed sensor 25 for detecting the vehicle speed VSP. 3 (a) and 3 (b) based on the input information to execute the lock-up solenoid 15
The duty control described above, that is, the slip limit control of the torque converter 1 and the slip limit start shock reduction control targeted by the present invention are performed as follows.

3A shows a main routine, and FIG. 3B shows a subroutine. In FIG. 3A, first, at step 31, the engine throttle opening TVO, the vehicle speed VSP and the selected gear Gp are read. . Next step 3
In step 2, a region corresponding to the engine throttle opening TVO, the vehicle speed VSP, and the selected shift speed Gp is determined from the input information based on a torque converter slip control map preset for each of the selected shift speeds Gp as shown in FIG. I do.
Here, CV is a region in which the torque converter is to be in a converter state in which no slip limit is set, LU is a lock-up region in which the slip amount of the torque converter should be set to 0, and SL is a state in which the torque converter is in an intermediate state between the two. Each of the slip control regions in which the slip amount is set to a designated amount (not shown) according to the engine operating state is shown.

In FIG. 3A, in step 32, the SL area is set.
Alternatively, it is checked whether or not it is in the LU range. If it is not in these ranges, that is, if it is in the CV range, the drive duty of the lock-up solenoid 15 is set to 0% in step 33.
By releasing the lock-up clutch 4, the torque converter 1 is brought into the converter state as predetermined.
If it is the SL area or the LU area, step 34 is executed to perform the lock-up clutch engagement control described below.

The control in this step 34 is shown in FIG.
First, at step 41, the input / output rotational speeds Ne and Nt of the torque converter are read. Next, at step 42, the torque converter slip amount △ N obtained from the difference Ne-Nt = △ N is equal to the set slip amount △ N indicating the start of lock-up clutch engagement shown in FIG.
It is checked whether the lock-up clutch 4 is engaged before or after the engagement is started based on whether or not it is longer than s.

[0023] If before binding the start of the lockup clutch, i.e. step 4 if the previous FIGS. 5 (a) Medium instant t ₂
In step 3, the lock-up clutch coupling pressure Pb is determined every moment to gradually increase the lock-up clutch coupling pressure Pb by the feedforward control. The is manner of increasing the lock-up clutch coupling pressure, 5 slip limiting command as shown in (a) instant t ₁
Gradually increased over time from such things as just a P ₀ + △ P in FIG. 6 in the lock-up clutch coupling initial instant t ₂ is considered. In the meantime the step 44 continues to reset the timer TIMER for measuring the elapsed time from the lock-up clutch coupling initial instant t ₂ to 0.

When the engagement of the lock-up clutch is started, the control branches to step 45, and the following control is performed. That is, at step 45, the TIMER is
Depending on whether or not showing the set time Ts illustrated in (a) checks whether reached instantaneously t ₃ when shown in FIG. During the period from the moment when the lock-up clutch is started to be engaged until the set time Ts elapses, in step 46, the lock-up clutch engagement pressure Pb is reduced to a pressure near the value at the moment when the lock-up clutch engagement is started, as shown in FIG. Set the keep command. Here, maintaining the lock-up clutch engagement pressure Pb at a pressure near the value at the instant of start of lock-up clutch engagement means that the lock-up clutch engagement pressure Pb is maintained at the same pressure as the instant of engagement of the lock-up clutch. This not only means that the lockup clutch engagement pressure Pb is gently increased from the value at the moment when the lockup clutch is started to be engaged within a range where the problem of the shock does not occur. Then, after reaching the instant t ₃ at which the set time Ts has elapsed from the instant at which the lock-up clutch is engaged, at step 47, the actual slip amount ΔN of the torque converter and the target slip amount (LU In the region, based on the deviation from the target slip amount of 0), the lockup clutch coupling pressure Pb for eliminating this deviation is obtained by PID calculation (feedback control). This PID operation is a well-known operation.
A method as described in JP-A-1463 can be adopted.

In step 48, steps 44, 46,
The drive duty of the lock-up solenoid 15 for achieving the lock-up clutch coupling pressure Pb obtained at 47 is calculated and output to the lock-up solenoid 15. Thereby, in the slip control region SL or the lock-up region LU, the lock-up clutch coupling pressure Pb at the time of switching to these regions is given as shown in FIG. 5A, and the slip amount ΔN of the torque converter 1 is shown in FIG. Thus, the target slip amount can be finally brought.

By the way, since the lock-up clutch coupling pressure Pb is prevented from rising during the set time Ts from the moment when the lock-up clutch is started to be coupled, the coupling force of the lock-up clutch is caused by the above-mentioned hysteresis characteristic on the hardware. Although this tendency tends to increase rapidly, this tendency can be alleviated to avoid the slip limit start shock and the unstable control as apparent from the slip lowering situation in FIG.

[0027]

Thus, the slip limiting start shock reducing device according to the present invention does not immediately feedback-control the lock-up clutch engagement pressure immediately after the start of engagement of the lock-up clutch, as described in claim 1, but from the start of the engagement. Since the lock-up clutch engagement pressure is maintained at a pressure near the value at the start of the engagement during the set time, the feedback according to the deviation between the actual slip amount of the torque converter and the target slip amount during the set time from the start of the engagement. The control amount is not added to the lock-up clutch engagement pressure, and therefore, the lock-up clutch engagement pressure does not continue to increase immediately after the start of engagement of the lock-up clutch. Conventionally, as described above, the feedback control of the lock-up clutch engagement pressure was started immediately after the start of engagement of the lock-up clutch, and the lock-up clutch engagement pressure was continuously increased immediately after the start of engagement of the lock-up clutch. The synergistic effect with the hysteresis characteristic shown in FIG. 6, which rapidly increases the coupling force immediately after the start of the coupling, causes a large shock and an unstable control due to a sudden decrease in the torque converter slip amount. As described above, the lock-up clutch coupling pressure is maintained at a pressure near the value at the start of the coupling without performing the feedback control of the lock-up clutch coupling pressure for a set time from the start of the lock-up clutch coupling. Hysteresis that causes the coupling force to rise immediately after the coupling starts雖 and those with sex also, it is possible to eliminate the instability of the generation and control of a large shock due to the sudden decrease of the torque converter slip amount.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a slip limit start shock reduction device of the present invention.

FIG. 2 is a system diagram of a slip limit control device for a torque converter showing one embodiment of the present invention.

FIG. 3 is a flowchart of a control program executed by the controller of the example.

FIG. 4 is a map of a slip control area of the torque converter in the example.

FIG. 5A is a time chart of a slip limiting operation of the same example, and FIG. 5B is a time chart of a slip limiting operation of the conventional device.

FIG. 6 is a graph showing a change characteristic of a torque converter slip amount with respect to a coupling pressure of a lock-up clutch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Torque converter (fluid transmission) 1a Pump impeller (input element) 1b Turbine runner (output element) 2 Engine 3 Gear transmission mechanism 4 Lock-up clutch 7 Lock-up control valve 13 Pressure source 15 Lock-up solenoid 16 Controller 21 Throttle opening Sensor 22 Engine rotation sensor 23 Turbine rotation sensor 24 Gear position sensor 25 Vehicle speed sensor

Continuation of the front page (56) References JP-A-1-120479 (JP, A) JP-A-60-116929 (JP, A) JP-A-2-120567 (JP, A) JP-A-3-129167 (JP) JP-A-2-292461 (JP, A) JP-A-4-331868 (JP, A) JP-A-4-140569 (JP, A) JP-A-4-1133071 (JP, A) 5-187540 (JP, A) JP-A-5-180321 (JP, A) JP-A-5-172241 (JP, A) JP-A-61-43953 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16H 61/14

Claims (1)

(57) [Claims] An internal working fluid stirred by an input element transmits power from the input element to an output element, and a slip-up between the input and output elements can be limited by an appropriate connection of a lock-up clutch. The lock-up clutch engagement pressure is gradually increased until the lock-up clutch engagement start detecting means detects the start of engagement of the lock-up clutch after the slip limitation command means instructs the slip limitation, and then the lock-up is performed. In the slip limit control device of the fluid transmission device, wherein the up-clutch engagement pressure is feedback-controlled in accordance with the deviation between the target slip amount and the actual slip amount, the lock-up clutch engagement start detecting means determines that the engagement of the lock-up clutch is started. A timing means for measuring the elapsed time after the detection, and the elapsed time A fluid transmission device comprising feedback control delay means for inhibiting the feedback control and keeping the lock-up clutch engagement pressure close to the value at the time of starting the lock-up clutch engagement until a fixed time is reached. Slip limit start shock reduction device.