Patent GB-1277321-A (GB)
Title: Automatic transmission
IPC: F16H47/08
Filed: 1970-05-15
Abstract: 1277321 Change-speed control NISSAN MOTOR CO Ltd 15 May 1970 [21 May 1969] 23737/70 Heading F2D  To improve engine-brake capacity of a vehicle automatic transmission on entering manual ranges II and I from Drive, a throttle back-up valve 165 is arranged to supply regulated line pressure through a line 177 to the usual engine-manifold-depression-responsive TV valve 167 to lock that valve in a position delivering to the TV line 151 a pressure which exceeds the normal maximum TV pressure at full throttle, with the following effects:-(a) by loading the main regulator valve 79 through a line 87 servo pressure is increased to a desired level; (b) the increased TV pressure is applied in the downshift direction to the usual 1-2 automatic shift valve 133 so that an automatic 2-1 downshift, which occurs in range I (not in range II), occurs at a higher speed during deceleration of the vehicle, so that engine braking in first ratio occurs earlier than in Drive; (c) the throttle back-up valve 165 cancels the TV pressure increase after the 2-1 downshift to soften the shift; and (d) the pressure increase is restored on manual upshift to range II from first ratio in range I, but subject to delay to soften the shift. The throttle back-up valve 165 has no effect in range D. Function summary.-A manual selector valve 109 provides ranges, D, giving automatic shift between all three forward ratios, first being oneway; II giving invariable second; and I giving two-way first and second under automatic 2-1 downshift control. Automatic shifts are in response to output governor pressure 135 and TV pressure 151. Detent downshift is by solenoid valve 71. Servo pressure is augmented in reverse, increases with TV pressure and also with the increased TV pressure above referred to. The automatic 2-1 downshift in I setting is at a higher speed than in D, and first ratio is locked in after the 2-1 downshift. Gear arrangement.-The gear, Fig. 1, not shown, is the usual torque-converter-driven Simpson planetary gear-set, with selective input clutches, one, 55, a forward clutch engaged in all forward ratios, the other, 53, a direct-drive and reverse clutch; a second ratio band-brake 57 and a low-reverse disc brake 59 in parallel with a one-way brake. Fluid-pressure supply and regulation.-A single input-driven pump 61 supplies the system main 77 under control of a pressure-regulating valve 79 loaded by TV pressure 151 through a line 87 acting on a boost valve 91, and also oppositely loaded by TV pressure 151 supplied to a line 97 through a cut-back valve 171 opened at high speeds by governor pressure 135. Control pressures.-Governor pressure 135 is provided by a two-stage output driven governor valve 63, 65, not described, supplied from the main 77, through the manual valve 111 in all forward settings. TV pressure 151 is provided by a regulator valve 167 loaded by a diaphragm subject to engine inlet-manifold depression, the valve exhausting through a line 177 subject to pressure control by the back-up valve 165 as detailed below. Shift valves are loaded left for upshift by governor pressure 135. The 2-3 shift valve 131 is loaded rightwards for downshift by spring and TV pressure 151, whilst the 1-2 shift-valve 133 has downshift loading by a spring, assisted by TV pressure 151 reaching a differential end land through the 2-3 valve 131 and a line 152, and replaced in range I by boosted TV and line pressure as described below. Manual valve 109 in setting N, neutral, blocks main pressure 77 at the inlet port 115. In all forward range settings, the manual valve pressurizes the forward clutch 55 and 1-2 shiftvalve 133 directly through a line 121. In Drive, D, pressure is supplied also to lines 117, 119, the former feeding the 2-3 shift valve 131 through a forward restrictor 155, and also a second-ratio lock valve 129 to raise that valve (position shown at right). The vehicle starts in first ratio, reacting on the one-way detent. When the 1-2 shift-valve 133 is upshifted left by spring and TV opposed governor pressure 135, it pressurizes from 121 aline 141 feeding the apply line 145 of the second ratio brake 57 through the raised second ratio lock valve 129. When governor pressure 135 overcomes spring and TV pressure 151, it upshifts the 2-3 shift-valve 131, which feeds pressure from the line 117 through the one-way restrictor 155 to a release line 159 of the second-ratio brake 57, and also feeds, through a restrictor 199 the engage line 193 of the direct-reverse clutch 53, establishing third ratio. At high speeds the restrictor 199 is by-passed by a by-pass valve 195 raised by governor pressure 135. In II setting, the manual valve 109 exhausts the line 117 and pressurizes in addition to 119, 121, line 125, the former cutting the feed to the 2-3 shift-valve 131, preventing upshift to third, and also permitting the second-ratio lockvalve 129 to be moved down (left of Fig. 2 by pressure 119, which then directly feeds the apply line 145 of the second brake 57 independently of the 1-2 shift valve 133. Line 125 provides a feed to the solenoid downshift valve 71, additional to its normal main feed 77, and also feeds the throttle back-up valve 165 for the purpose described below. In I setting the lines 117, 119 are exhausted, permitting the second-ratio lock valve 129 to move up (shown at right in Fig. 2); and pressurizing line 123 in addition to 121 and 125. If the 1-2 valve 133 is upshifted at the time of selecting manual I, pressure reaches the apply line 145 of the second brake 57 from line 121, 1-2 shift valve 133, line 141 and second ratio lock valve 129. In this condition the 1-2 valve 133 is loaded to downshift by line pressure and/or TV pressure under control of the throttle back-up valve 165 described below. On such downshift, the second brake feed line 141 exhausts, and line 123 feeds the low-reverse brake 59 through the 1-2 valve 133, line 175 and one-way restrictor 169. R setting is similar to I except that line 121 is exhausted, releasing the forward clutch 55, and 127 is additionally pressurized to supply the direct-reverse clutch line 193 through the downshifted 2-3 shift valve 131, governor pressure feed being exhausted at 121. Throttle back-up valve 165.-Action of this valve differs according to the following two conditions:-(a) manual downshift to setting II or to setting I at the time that the 1-2 shiftvalve 133 is upshifted, or (b) manual upshift into setting II from I. The valve 165 controls pressure in a line 177 through which the TV valve 167 exhausts during normal action to regulate TV pressure 151. Under condition (a) a low-reverse brake line 175 is exhausted and the spool of the back-up valve 165 descends left, Fig. 2), to supply modulated pressure from the line 125 to the TV control line 177, causing the TV valve 167 to rise to its limit and supply the TV line 151 with that modulated pressure 177 which is higher than full throttle TV pressure, and increases loading of the main regulator valve 79 and hence servo pressure, for engine-brake capacity in second ratio. When, after a shift to setting I, the 1-2 shift-valve 133 automatically downshifts, it pressurizes the line 175 of the low-reverse brake 59, from which the pressure passes through a ball check-valve 189 in the spool of the back-up valve 165 to shift that spool upwards (right, Fig. 2), exhausting the line 177 to restore normal TV control, providing a smooth downshift at normal servo pressure. A subsequent manual selection of setting II (condition (b) above), exhausts the low-reverse brake line 175, but the above increased TV and servo pressures are restored only slowly as pressure leaks from below the back-up valve 165 past the clearance of the ball check-valve 189, to allow the valve spool to descend slowly for gradual pressurizing of the TV control line 177. In D setting both lines 123, 125 are exhausted, and the throttle back-up valve 165 is therefore without effect. Figs. 3 and 4 (not shown) are enlarged views of the throttle back-up valve 165, the latter differing from the former in that the ball check valve 189 is in the end of the stationary valve cylinder rather than in the valve spool. The downshift loading of the 1-2 shift-valve 133 in I setting, as referred to above, is controlled by the throttle back-up valve 165 as follows. In the upshifted position of the 1-2 shift-valve 133 the throttle back-up valve 165 boosts throttle pressure 151 to a maximum value as above described, and this boosted pressure 151, passing through the unoperated solenoid downshift valve 71 (position left, Fig. 2), and a line 185, acts in the downshift direction on a differential end land of the 1-2 shift-valve 133. This raises the 2-1 downshift speed point in comparison with that in D range, introducing first ratio earlier during deceleration for increased engine braking. After the 2-1 downshift in setting I, the throttle back-up valve 165 restores normal throttle pressure 151; and full TV-responsive line pressure, directed from line 123 to the low-reverse brake line 175 through the 1-2 shift valve 133, passes to the left end of that valve, locking it in downshift position under all conditions.